Press Brake Die Holder Technology

FIELD OF THE INVENTION

0001The present invention is in the field of press brakes. More particularly, this invention relates to die holders for press brakes.

BACKGROUND OF THE INVENTION

0002Tooling for use with a press brake commonly includes a horizontally elongated punch having a downwardly-facing tip, and a horizontally elongated die having an upwardly open workpiece-contact portion adapted to receive the punch tip during, for example, a workpiece bending operation.

0003Due to the substantial forces involved in bending operations, it is important that punches and dies be kept in alignment to avoid undue wear, to assure accurate bending, and to avoid breakage. Commonly, the punch is mounted in a fixed position, and the die can be positionally adjusted into precise alignment with the punch tip. When the die holder is then locked in position, relative lateral movement between the punch and die is restrained.

0004A press brake die commonly has a downwardly extending tang that is mounted in an upwardly open channel of a die holder. Set screws, inserted through the side of the die holder, may be employed to lock the die's tang in the channel. In other cases, the fit between the tang and die holder is sufficiently close that no locking is provided, and as a result, the die can be removed from the die holder with some ease.

0005Particularly in the latter case (in which the die's tang is simply received in a closely sized channel of the die holder), some slight back and forth rocking motion or “wobble” of the die within the holder can occur, and is difficult to avoid. A very small amount of wobble or play between the die's tang and the channel is magnified at the upper portion of the die (where the die meets the punch tip). It is difficult economically to obtain tolerances that prevent such movement. If most of the wobble is to be avoided by extremely close tolerances in machining the tang and channel, the cost of machining may become economically prohibitive. Furthermore, very close tolerances between the tang and die holder make it difficult to insert the tang into the die holder.

0006It would be desirable to provide a die holder that offers positive die clamping. It would be particularly desirable to provide a die holder that offers positive clamping without requiring adjustment of set screws or other fasteners that require tools. It would also be desirable to provide a die holder that is convertible between a hydraulically-operable state and a manually-operable state. Further, it would be desirable to provide a die holder having one or more die-contact bodies that deliver downward force to the tang of a die during clamping. Finally, it would be desirable to provide a die holder having selected surfaces coated with wear-resistant coating.

SUMMARY OF THE INVENTION

0007In certain embodiments, the invention provides a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. The die holder has a first shoulder, a second shoulder, a base, and an elongated channel adapted to receive the tang of the die. In the present embodiments, the die holder further includes an elongated locking bar adapted for movement toward the second shoulder of the die holder so as to positively clamp the tang when the tang is positioned in the channel. The present embodiments involve the first shoulder of the die holder carrying at least one cam member, which is adapted to move so as to cause a camming action between the cam member and the locking bar. This camming action causes the movement of the locking bar toward the second shoulder of the die holder.

0008Some embodiments of the invention provide a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. In the present embodiments, the die holder is adapted for conversion between a first operatively-assembled configuration having a manually-operable actuator unit and a second operatively-assembled configuration having a hydraulically-operable actuator unit. The die holder has a block that includes a base and a shoulder. Preferably, the base and shoulder together have a generally L-shaped configuration. In the present embodiments, the die holder further includes an elongated locking bar. This locking bar has a first clamping wall, while the noted shoulder has a second clamping wall. Here, the die holder is provided with a rigid fastening assembly adapted to rigidly attach the base, as desired, either to a lower portion of the manually-operable actuator unit or to a lower portion of the hydraulically-operable actuator unit. This die holder is also provided with a resilient fastening assembly adapted to resiliently attach the locking bar, as desired, either to an upper portion of the manually-operable actuator unit or to an upper portion of the hydraulically-operable actuator unit.

0009In certain embodiments, the invention provides a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. The die holder has two confronting walls between which the tang can be positioned. A desired one of the walls is adapted for being moved toward the other wall so as to positively clamp the tang when the tang is positioned between the two walls. In the present embodiments, the die holder is provided in combination with both a manually-operable actuator unit and a hydraulically-operable actuator unit, and the die holder is adapted for conversion between a first operatively-assembled configuration that includes the manually-operable actuator unit and a second operatively-assembled configuration that includes the hydraulically-operable actuator unit.

0010Some embodiments of the invention provide a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. The die holder has two confronting walls between which the tang can be positioned, and a desired one of the two walls is adapted for being moved toward the other wall so as to positively clamp the tang when the tang is positioned between the two walls. In the present embodiments, the die holder has a die-contact body that delivers a downward force to the tang when the tang is positively clamped between the two walls. This downward force urges the tang downwardly toward a base of the die holder (which base typically extends between the two walls of the die holder). Preferably, the die holder and die-contact body are adapted to deliver the downward force to the tang even when the opposed clamping surfaces of the tang consist of parallel planar surfaces. In certain embodiments of this nature, during positive clamping of the die's tang between the two confronting walls, the die-contact body delivers the downward force as a frictional force. Some of the present embodiments involve the two confronting walls both carrying die-contact bodies adapted to collectively deliver the downward force. In such embodiments, the die-contact bodies can optionally be mounted on the confronting walls so as to have limited range freedom of movement relative to the confronting walls. In one advantageous embodiment, the die-contact bodies are wedge members that, during positive clamping of the die's tang between the two confronting walls, move downwardly relative to the confronting walls (e.g., the base of the die holder).

0011Certain embodiments of the invention provide a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. The die holder has two confronting walls between which the tang can be positioned. A desired one of the two walls is adapted for being moved toward the other wall so as to positively clamp the tang when the tang is positioned between the two walls. In the present embodiments, the die holder has a resilient body that delivers a downward force to the tang when the tang is positively clamped between the two walls. This downward force urges the tang downwardly toward a base of the die holder.

0012In some embodiments, the invention provides a press brake die holder for holding a die having an upper, workpiece-contact portion and a lower, elongated tang. The die holder has a block that includes a base and a shoulder. Preferably, the base and shoulder together have a generally L-shaped configuration. In the present embodiments, the die holder further includes an elongated locking bar. Preferably, the locking bar has a first clamping wall, and the noted shoulder has a second clamping wall. In the present embodiments, the locking bar's clamping wall is defined by uncoated metal, and the locking bar has a bottom wall that bears a coating and that is adapted to slide along a coating on the base during clamping and unclamping actions of the die holder. Further, the noted shoulder preferably has an upwardly-facing loading surface (optionally one along which a downwardly-facing loading surface of the die is adapted to slide during positioning of the die at such time as the die holder is in an unclamped position) that has a coating. Still further, the locking bar preferably has an upwardly-facing loading surface (optionally one along which a downwardly-facing loading surface of the die is adapted to slide during positioning of the die at such time as the die holder is in the unclamped position) that has a coating.

0013In some embodiments involving a locking bar, the locking bar has a long axis parallel to the die holder's longitudinal axis (e.g., parallel to the die holder's channel), and the locking bar is adapted to move (e.g., laterally) in a horizontal plane perpendicular to the locking bar's long axis during clamping and unclamping actions of the die holder.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a die holder on which is mounted a die in accordance with certain embodiments of the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> is a partially exploded perspective view of the die holder and die of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a partially exploded perspective view of a manually-operable actuator unit that is provided in certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 4</figref> is a perspective view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 3</figref>;

<figref idref="DRAWINGS">FIG. 5</figref> is a front view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 4</figref>;

<figref idref="DRAWINGS">FIG. 6</figref> is a top view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 4</figref>;

<figref idref="DRAWINGS">FIG. 7</figref> is a back view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 4</figref>;

<figref idref="DRAWINGS">FIG. 8A</figref> is a broken-away top view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 4</figref>, wherein the illustrated cam member is shown in a first configuration;

<figref idref="DRAWINGS">FIG. 8B</figref> is a broken-away top view of the manually-operable actuator unit of <figref idref="DRAWINGS">FIG. 4</figref>, wherein the illustrated cam member is shown in a second configuration;

<figref idref="DRAWINGS">FIG. 9</figref> is a perspective view of a die holder on which is mounted a die in accordance with other embodiments of the invention;

<figref idref="DRAWINGS">FIG. 10</figref> is an exploded perspective view of the die holder and die of <figref idref="DRAWINGS">FIG. 9</figref>;

<figref idref="DRAWINGS">FIG. 11</figref> is an exploded perspective view of a hydraulically-operable actuator unit that is provided in certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 12</figref> is a front view of the hydraulically-operable actuator unit of <figref idref="DRAWINGS">FIG. 11</figref>;

<figref idref="DRAWINGS">FIG. 13</figref> is a back view of the hydraulically-operable actuator unit of <figref idref="DRAWINGS">FIG. 11</figref>;

<figref idref="DRAWINGS">FIG. 14</figref> is a cross-sectional view of the hydraulically-operable actuator unit of <figref idref="DRAWINGS">FIG. 13</figref> taken along lines <b>14</b>-<b>14</b>;

<figref idref="DRAWINGS">FIG. 15A</figref> is an end view of a die holder in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 15B</figref> is an end view of another die holder in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 16</figref> is a cross-sectional view of the hydraulically-operable actuator unit of <figref idref="DRAWINGS">FIG. 12</figref> taken along lines <b>16</b>-<b>16</b>;

<figref idref="DRAWINGS">FIG. 17</figref> is a schematic end view of a die holder in accordance with certain embodiments;

<figref idref="DRAWINGS">FIG. 18</figref> is a perspective view of a die holder in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 19</figref> is a perspective view of another die holder in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 20</figref> is a perspective view of a die holder on which is mounted a die in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 21</figref> is an exploded perspective view of the die holder and die of <figref idref="DRAWINGS">FIG. 20</figref>;

<figref idref="DRAWINGS">FIG. 22</figref> is a schematic cross-sectional view of the die holder and die of <figref idref="DRAWINGS">FIG. 20</figref>;

<figref idref="DRAWINGS">FIG. 23</figref> is a schematic perspective view of the die holder and die of <figref idref="DRAWINGS">FIG. 20</figref>;

<figref idref="DRAWINGS">FIG. 24</figref> is an end view of a die holder in accordance with certain embodiments of the invention;

<figref idref="DRAWINGS">FIG. 25</figref> is a cross-sectional view of the die holder of <figref idref="DRAWINGS">FIG. 24</figref>; and

<figref idref="DRAWINGS">FIG. 26</figref> is a broken-away perspective view of a press brake on which is mounted a die holder in accordance with certain embodiments of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0042The following detailed description is to be read with reference to the drawings, in which like elements in different drawings have like reference numerals. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Skilled artisans will recognize that the given examples have many useful alternatives, which fall within the scope of the invention.

0043The die holder is designated by the reference numeral <b>10</b>. Typically, the die holder is adapted for being mounted (or is mounted) on a lower beam of a press brake. Reference is made to U.S. Pat. No. 6,119,503 (Peloquin et al.) and U.S. Pat. No. 6,516,649 (Mika et al.), the teachings (including the drawings) of which concerning exemplary ways to mount a die holder on the lower beam of a press brake are incorporated herein by reference. In some (though not all) cases, the die holder is mounted on a stationary lower bean (or table) LT of a press brake PB. In these cases, the die holder <b>10</b> is a vertically-fixed die holder (i.e., one that is not moveable (and does not move) vertically during the press brake's pressing/punching stroke). In these embodiments, the die holder <b>10</b> will typically be located directly below a vertically-moveable punch holder PH mounted on an upper beam (or table) of the press brake PB.

0044<figref idref="DRAWINGS">FIG. 26</figref> schematically illustrates a press brake PB utilizing a die holder <b>10</b> in accordance with certain embodiments of the present invention. The press brake includes a series of horizontally aligned upper clamps, which are used to clamp punches (not shown) against a support plate. The clamp is brought into clamping engagement with the punch by means of an upper handle. Useful press brake punch holders are described in PCT International Publication No. WO 99/01240 (the salient teachings of which are incorporated herein by reference). The punches disclosed in this PCT Publication are solely for purposes of illustration. The present die holder can be used on any press brake without requiring any specific punches or punch holders.

0045The die holder <b>10</b> is mounted on a lower table LT of the press brake PB. The die holder <b>10</b> is shown with a base block BB. The base block may be attached to the lower table LT in any suitable fashion. For example, the base block may be held in place on the lower table by means of a pair of opposed brackets BR. (Only one of the opposed brackets is shown in <figref idref="DRAWINGS">FIG. 26</figref>, the other of the pair being positioned behind the die holder <b>10</b> and thus being obscured from view.) The bracket desirably can be adjusted to release the base block <b>30</b>. This releasable attachment of the die holder <b>10</b> to the lower table LT permits the die holder <b>10</b> to be selectively retrofitted to any standard press brake. It is to be understood that many different crowning systems can be provided with the present die holder.

0046The die holder <b>10</b> is adapted for holding a press brake die D. Typically, the die D has an upper, workpiece-contact portion and a lower, elongated tang T. Many different types of press brake dies can be used. <figref idref="DRAWINGS">FIGS. 1</figref>, <b>2</b>, <b>9</b>, and <b>10</b> depict one exemplary press brake die D, of known design, which includes an upper portion having a generally V-shaped groove <b>24</b> defined by upwardly divergent, intersecting walls <b>26</b>, <b>28</b>. These walls terminate upwardly at edge surfaces <b>27</b>, <b>29</b>, which may be smooth and gently rounded to enable a workpiece to slide readily over these surfaces during a bending operation. This, however, is merely one useful die configuration. People knowledgeable in this field of technology will appreciate that many different types of dies can be used.

0047In some embodiments, the die D has downwardly-facing shoulders that define surfaces <b>21</b>. These surfaces <b>21</b> preferably are adapted to be (and in some cases, are) carried against corresponding upwardly-facing surfaces <b>66</b>, <b>76</b> of the die holder <b>10</b>. In other cases, the bottom surface <b>221</b> of the die's tang T is carried against the die holder's base <b>62</b> during operation. For example, some useful dies do not have mounting shoulders, but rather use the bottom surfaces <b>221</b> of their tangs as mounting surfaces.

0048The die D has, at its lower end, a tang T. In some cases, the tang T is generally square or generally rectangular in cross section (i.e., in vertical cross section). As is perhaps best seen in <figref idref="DRAWINGS">FIGS. 2 and 10</figref>, the tang T has opposing (in some cases, generally parallel) walls <b>144</b>, <b>146</b>, which are adapted to be clamped by the die holder. For some types of dies, the walls <b>144</b>, <b>146</b> may have grooves, angled surfaces, or other contours.

0049The die D is configured for use with a corresponding punch. In some cases, the punch has a downwardly facing, V-shaped tip, which during a bending operation is pressed into the V-shaped groove <b>24</b> of a die D like that described above. In such cases, it will be understood that a workpiece (such as a piece of sheet metal) is positioned between the punch and die, and is bent when the punch descends into the die. The present die holder, however, is not limited to use with any particular type of die. Rather, many different types of dies can be used.

0050The die holder <b>10</b> includes a first shoulder <b>82</b>, a second shoulder <b>64</b>, and a base <b>62</b>. The die holder <b>10</b> has an elongated channel <b>55</b>, which is adapted to receive the tang T of a die D. Preferably, the channel <b>55</b> is upwardly open (e.g., is an upwardly-open slot). In some embodiments, the channel <b>55</b> is generally square or generally rectangular in cross section (e.g., in vertical cross section taken perpendicular to clamping wall <b>65</b>). In certain embodiments, the channel's width (which extends along the die holder's X axis, or “lateral axis”) can be varied by moving a locking bar <b>70</b> (described below) selectively toward or away from the die holder's second shoulder <b>64</b>.

0051In the illustrated embodiments, the die holder's second shoulder <b>64</b> and base <b>62</b> are parts of a single (i.e., integral) block <b>60</b>. In other cases, the base <b>62</b> and the second shoulder <b>64</b> are separate bodies attached together to form the block <b>60</b>. Either way, the block <b>60</b> preferably is formed of metal or another rigid material. For example, P20 grade prehard material with a hardness of 28-32 and nitrided surface treatment to a 70 HRC can be used. Of course, other materials can be used, and this example is by no means limiting.

0052The illustrated base <b>62</b> and shoulder <b>64</b> together have a generally L-shaped configuration. For example, the illustrated shoulder <b>64</b> (a clamping wall <b>65</b> thereof, or a planar portion of such clamping wall) may extend away from one end of the base <b>62</b> at an angle that is at least generally normal (e.g., about 90 degrees). When the die holder is operatively assembled and mounted on the lower beam of a press brake (<figref idref="DRAWINGS">FIG. 26</figref>), the shoulder <b>64</b> rises vertically upwardly from one end of the base <b>62</b>. As is perhaps best seen in <figref idref="DRAWINGS">FIG. 2</figref>, in addition to the L-shaped configuration of the base <b>62</b> and shoulder <b>64</b>, the block <b>60</b> may have a downwardly extending tang <b>61</b>. Moreover, in some embodiments, the block <b>60</b> defines a U-shaped configuration. Reference is made to the exemplary embodiments of <figref idref="DRAWINGS">FIGS. 18-23</figref>. People familiar with this area of technology will understand that the precise configuration of the block <b>60</b> will vary, e.g., depending upon the manner in which the die holder is to be mounted on the lower beam of a press brake.

0053Certain embodiments provide a die holder having an elongated locking bar. In these embodiments, the locking bar <b>70</b> is adapted to move (e.g., laterally) toward the die holder's second shoulder <b>64</b> so as to positively clamp the tang T when the tang is positioned in the channel <b>55</b>. The locking bar <b>70</b>, for example, may have a long axis parallel to the die holder's longitudinal axis (e.g., parallel to the die holder's channel <b>55</b>), and this bar <b>70</b> may be adapted to move (e.g., laterally) in a horizontal plane perpendicular to the locking bar's long axis during clamping and unclamping actions of the die holder.

0054The locking bar <b>70</b> can optionally have a generally square or generally rectangular cross section (taken in a vertical plane perpendicular to clamping wall <b>65</b>). In the illustrated embodiments, the locking bar <b>70</b> has an upwardly-facing (e.g., planar) top surface <b>76</b> that (when the die holder is operatively mounted on the lower table of a press brake) lies in substantially the same horizontal plane as (e.g., is at least generally flush to, is at least substantially flush to, or is flush to) the upwardly-facing top surface <b>66</b> of shoulder <b>64</b> (and/or to the upwardly-facing top surface <b>86</b> of shoulder <b>82</b>).

0055In some cases, the locking bar <b>70</b> also has a downwardly-facing (e.g., planar) surface <b>74</b> that is adapted to slide against the die holder's base <b>62</b> during clamping and unclamping actions of the die holder.

0056The length of the locking bar (i.e., its major dimension) preferably extends parallel to the length of the die holder's channel <b>55</b>. In some embodiments, the locking bar <b>70</b> has a length of at least 4 inches, or at least 5 inches.

0057Certain embodiments of the invention provide an arrangement wherein one locking bar, or a plurality of locking bars disposed serially in an end-to-end fashion, extends alongside (and bands one side of) the entire length (or substantially the entire length) of the die holder's channel. When provided, the (or each) locking bar <b>70</b> preferably defines a clamping wall <b>75</b> that is adapted to contact the die's tang T during the tool holder's clamping action. Preferably, the clamping wall <b>75</b> extends along the entire length, or substantially the entire length, of the locking bar <b>70</b>.

0058The locking bar <b>70</b> preferably is formed of metal or another rigid material. Again, P20 grade prehard material with a hardness of 28-32 and nitrided surface treatment to a 70 HRC can be used. However, other materials can be used, and this example is by no means limiting.

0059In <figref idref="DRAWINGS">FIGS. 1-8B</figref>, the die holder's first shoulder <b>82</b> is part of a camming actuator unit (optionally, a manually-operable camming actuator unit, as described below). Here, the first shoulder <b>82</b> is defined by a block <b>80</b>, which in these figures is not integral to (i.e., is a different body than) the block <b>60</b> comprising the base <b>62</b> and second shoulder <b>64</b>. The block <b>80</b> preferably is formed of metal or another rigid material. Here again, P20 grade prehard material with a hardness of 28-32 and nitrided surface treatment to a 70 HRC can be used. Other materials can be used, of course, and this example is by no means limiting.

0060In <figref idref="DRAWINGS">FIGS. 1-8B</figref>, the block <b>80</b> defining the first shoulder <b>82</b> preferably is adapted for being removably attached to the block <b>60</b> comprising the base <b>62</b> and second shoulder <b>64</b>. Between the illustrated removable first shoulder <b>82</b> and the second shoulder <b>64</b> are located the laterally-moveable locking bar <b>70</b> and the channel <b>55</b>. In more detail, the illustrated locking bar <b>70</b> is located between the first shoulder <b>82</b> and the channel <b>55</b>.

0061The blocks <b>60</b>, <b>80</b> can be removably attached to each other in different ways. Referring to <figref idref="DRAWINGS">FIGS. 2 and 7</figref>, it can be seen that one option involves a plurality of fasteners <b>405</b> that can be extended through respective openings <b>402</b> in the die holder's base <b>62</b> and into corresponding openings <b>403</b> in block <b>80</b>. More generally, though, it should be appreciated that many different removable fastening systems can be used.

0062In the embodiments exemplified by <figref idref="DRAWINGS">FIGS. 1-8B</figref> and <b>18</b>-<b>23</b>, the die holder's first shoulder <b>82</b> carries at least one cam member <b>100</b> adapted to be moved (optionally rotated) so as to cause a camming action between such cam member and the locking bar <b>70</b>. This camming action forces the locking bar <b>70</b> to move toward the second shoulder <b>64</b> of the die holder (hence decreasing the width of the channel <b>55</b>). Various arrangements can be used to provide this type of camming action.

0063Referring to <figref idref="DRAWINGS">FIGS. 1-8B</figref>, <b>18</b> and <b>19</b>, the illustrated locking bar <b>70</b> has a rear wall <b>74</b> facing the first shoulder <b>82</b> of the die holder <b>10</b>. Here, the camming action involves each of a plurality of cam members <b>100</b> camming against the rear wall <b>74</b> of the locking bar <b>70</b> so as to force the locking bar to move toward the second shoulder <b>64</b> of the die holder <b>10</b>. In other embodiments, the camming action involves a single cam member camming against the rear wall of the locking bar.

0064One group of embodiments involves a cam member <b>100</b> that is adapted to protrude from a cavity <b>119</b> that opens through an inner wall (i.e., a wall facing the direction of the channel) <b>85</b> of the die holder's first shoulder <b>82</b>. In some embodiments of this nature, during the die holder's camming action, the cam member <b>100</b> protrudes from the opening <b>119</b> while moving (optionally rotating) so as to cam with the locking bar <b>70</b> (optionally camming with the locking bar's rear wall <b>74</b>). Embodiments of this nature can advantageously involve a plurality of cam members <b>100</b> adapted to function in this way.

0065As noted above, the die holder's camming action may be initiated by rotation of the cam member. This may involve rotational non-linear motion. However, the cam member's movement can alternatively be linear motion. For example, this may involve linear non-rotational motion. Further, the cam member's movement may involve simultaneous linear and rotational motion. Still further, the die holder may include cam members that move in different manners to initiate camming (e.g., one cam member may undergo rotational non-linear motion, while another cam member undergoes linear non-rotational motion).

0066As camming occurs (and as the locking bar moves toward the die holder's second shoulder <b>64</b> in response to the camming), the distance between the locking bar <b>70</b> and the second shoulder <b>64</b> decreases (hence the width of the channel decreases). When the camming action is initiated at such time as the tang T of a die D is in the channel <b>55</b>, the resulting movement of the locking bar <b>70</b> positively clamps the tang of the die.

0067In some embodiments, the die holder's camming action involves a cam member <b>100</b> moving so as to cam with an interior wall (i.e., a wall bounding an interior cavity <b>177</b>) of the locking bar <b>70</b>. Reference is made to <figref idref="DRAWINGS">FIGS. 20-23</figref>. Here, the cam member <b>100</b> has a generally planar wall section <b>105</b> and a concave wall section <b>107</b>. When the end <b>109</b> of the illustrated handle <b>106</b> is inserted into the cam member's cavity <b>104</b>, and the handle is then moved horizontally, the cam member rotates between first and second configurations (or “orientations”). When the cam member <b>100</b> is in its first configuration, the planar wall section <b>105</b> directly faces the locking bar <b>70</b>. When the handle <b>106</b> is then turned so as to move the cam member <b>100</b> from its first configuration to its second configuration, the convex wall section <b>107</b> cams with the interior wall <b>174</b> of the locking bar <b>70</b> in such a way that the locking bar is forced to move toward the die holder's second shoulder <b>64</b>.

0068<figref idref="DRAWINGS">FIGS. 20-23</figref> exemplify a broad group of embodiments wherein the die holder <b>10</b> has a lateral width of 80 mm or less, perhaps more preferably 75 mm or less, and perhaps optimally 65 mm or less (such as about 60 mm). The design of <figref idref="DRAWINGS">FIGS. 20-23</figref> lends itself nicely to the slim dimensions noted in this paragraph. More generally, though, any design/embodiment disclosed in this specification can optionally have a width in any one or more of the noted ranges.

0069Referring again to <figref idref="DRAWINGS">FIGS. 1-8B</figref>, the illustrated die holder <b>10</b> has a plurality of cam members <b>100</b>. These cam members <b>100</b> are spaced apart along the length (which extends along the die holder's Z axis, or “longitudinal axis”) of the die holder's first shoulder <b>82</b>. In alternate embodiments, a single longitudinally elongated cam member may be provided.

0070With continued reference to <figref idref="DRAWINGS">FIGS. 1-8B</figref>, the die holder's camming action results when the (or each) cam member <b>100</b> is moved from a first configuration to a second configuration. <figref idref="DRAWINGS">FIGS. 8A and 8B</figref> depict exemplary first and second configurations. Here, the cam member <b>100</b> moves rotationally between its first and second configurations. In <figref idref="DRAWINGS">FIG. 1</figref>, when all the illustrated cam members <b>100</b> are in their first configurations, the locking bar <b>70</b> is held against (e.g., directly against) the first shoulder <b>82</b> of the die holder, and when all the cam members are in their second configurations, the locking bar <b>70</b> is spaced apart from the die holder's first shoulder <b>82</b> (and/or is closer to the die holder's second shoulder <b>64</b>). In these particular embodiments, the locking bar <b>70</b> is resiliently biased toward the die holder's first shoulder <b>82</b> such that, when all the cam members <b>100</b> are in their first configurations, the locking bar is held resiliently against the first shoulder. Thus, the locking bar <b>70</b> may have a default position in which it is held against the die holder's first shoulder <b>82</b> unless the die holder's camming action is initiated (or the resilient bias on the locking bar is otherwise overcome). This can advantageously give the die holder a fully-open default configuration, which facilitates positioning tools on the die holder.

0071In some of the present embodiments, the die holder <b>10</b> undergoes its camming action in response to a press brake operator performing a manual tool-free operation. Reference is made to <figref idref="DRAWINGS">FIGS. 1-8B</figref>, <b>18</b>-<b>23</b>, and <b>26</b>. The die holder, for example, can have one or more cam members <b>100</b> adapted to rotate in response to movement of a manually operated handle <b>106</b>. One end <b>109</b> of the handle <b>106</b> may be adapted to be received (e.g., removably) by the cam member. Thus, a press brake operator may simply insert the end <b>109</b> of the handle <b>106</b> into each cam member (e.g., into a cavity <b>104</b> therein), then manually turning the handle (so as to rotate such cam member) to positively clamp the die holder <b>10</b> on the tang T of a die D. This allows the operator to clamp the die holder easily, positively, and without having to use screwdrivers, allen wrenches, or other tools.

0072In one group of embodiments, the die holder <b>10</b> includes at least one cam member <b>100</b> that is adapted to rotate about a vertical axis to initiate the die holder's camming action. Reference is made to <figref idref="DRAWINGS">FIGS. 1-8B</figref>, <b>19</b>-<b>23</b>, and <b>26</b>. Here, the die holder's camming action may be initiated by turning the handle <b>106</b> horizontally. Horizontal handle control is particularly practical and advantageous.

0073The cam member(s) <b>100</b> can be provided in various forms. One group of embodiments provides a cam member <b>100</b> having a generally-cylindrical configuration. <figref idref="DRAWINGS">FIG. 3</figref> depicts one useful cam member <b>100</b> with a generally-cylindrical configuration. Here, the cam member <b>100</b> has a post-like bottom section (or “neck”) <b>102</b> and an upper head <b>101</b> having a larger diameter than the post-like bottom section. The illustrated head <b>101</b>, which is adapted to cam with the locking bar <b>70</b>, has a generally planar wall section <b>105</b> and a convex wall section <b>107</b>. Many different configurations can be used for the cam member. In some cases, only a portion of the (or each) cam member has a cylindrical (or generally cylindrical) configuration. If desired, the die holder can have different cam members with different configurations.

0074<figref idref="DRAWINGS">FIGS. 20-23</figref> depict another useful cam member configuration. Here, when the die holder is operatively assembled, the cam member <b>100</b> (or at least a head portion <b>101</b> thereof) is received in an interior cavity <b>177</b> defined by the locking bar <b>70</b>. This design represents a broader group of embodiments wherein (whether or not any part of the cam member is received in a cavity of the locking bar) the die holder's first shoulder <b>82</b> has a width less than the width of the die holder's second shoulder <b>64</b>. In the exemplary embodiments of <figref idref="DRAWINGS">FIGS. 20-23</figref>, the width (e.g., average width, or maximum width) of the first shoulder <b>82</b> is less than half the width (average or maximum) of the second shoulder <b>64</b>. This is perhaps best seen in <figref idref="DRAWINGS">FIG. 22</figref>.

0075<figref idref="DRAWINGS">FIG. 18</figref> depicts another useful cam member design. Here, the die holder's first shoulder <b>82</b> carries a rotatable rod <b>1100</b>. The rod <b>1100</b> has a long axis parallel to the die holder's channel <b>55</b>. A plurality of cam members <b>100</b> are carried by (e.g., rigidly attached to) the rod <b>1100</b> at locations spaced apart along the length of the die holder's first shoulder <b>82</b>. The rod <b>1100</b> preferably has a cavity into which an end of a handle <b>106</b> can be inserted, whereupon a press brake operator can turn the handle (in this case, by moving the handle in a vertical plane) to cause the cam members <b>100</b> to rotate together with the rod. During this rotation, the cam members <b>100</b> simultaneously cam with the locking bar <b>70</b>. This camming action forces the locking bar to move toward the die holder's second shoulder <b>64</b>.

0076<figref idref="DRAWINGS">FIG. 19</figref> depicts another useful cam member design. Here, the cam member <b>100</b> can have the same shape as the cam members <b>100</b> shown in <figref idref="DRAWINGS">FIGS. 1-8B</figref>. In <figref idref="DRAWINGS">FIG. 19</figref>, though, the locking bar <b>70</b> comprises two elongated bars (both desirably being metal or another rigid material) carried against each other. One of these bars defines the locking bar's rear wall <b>74</b>, while the other bar defines the locking bar's clamping wall <b>75</b>. Other multi-part locking bar designs can be used as well.

0077The die holder's first shoulder <b>82</b> can optionally have a vertically-extending generally-cylindrical opening <b>119</b> in which a cam member <b>100</b> is rotatably received. Reference is made to <figref idref="DRAWINGS">FIGS. 3 and 19</figref>.

0078In some preferred embodiments, the cam member <b>100</b> is adapted to be nested within (or is nested within) an opening <b>119</b> defined by the die holder's first shoulder <b>82</b>. <figref idref="DRAWINGS">FIGS. 1-8B</figref> and <b>19</b>, for example, depict embodiments wherein a wall section <b>89</b> of the die holder's first shoulder <b>82</b> surrounds more than 180 degrees of the cam member's head portion <b>101</b>. Perhaps more preferably, this wall section <b>89</b> surrounds more than 240 degrees (optionally more than 270 degrees) of the cam member's head portion <b>101</b>. In some embodiments, this surrounding extent of the wall section <b>89</b> is measured in a horizontal cross section that also passes through the head portion <b>101</b> of the cam member <b>100</b>. This is perhaps best appreciated by referring to <figref idref="DRAWINGS">FIG. 6</figref>.

0079The die holder <b>10</b> in <figref idref="DRAWINGS">FIGS. 1-8B</figref> has a first shoulder <b>82</b> defining a plurality of cavities <b>119</b> in which respective cam members <b>100</b> are received. Each cam member <b>100</b> is adapted to be rotated in such a way that a portion of the rotating cam member (e.g., a wall section <b>107</b> thereof) is caused to protrude from an inner wall <b>85</b> (e.g., from a cavity <b>119</b> that opens through the inner wall <b>85</b>) of the first shoulder <b>82</b> and cam with the locking bar (e.g., with a rear wall <b>74</b> of the locking bar), thereby forcing the locking bar to move toward the die holder's second shoulder <b>64</b>.

0080In <figref idref="DRAWINGS">FIGS. 1-8B</figref>, <b>18</b>-<b>23</b>, and <b>26</b>, an outer wall (i.e., a wall facing away from the channel) of the die holder's first shoulder <b>82</b> has a cam-access opening (or “window”) <b>81</b> through which one end <b>109</b> of a manually-operable handle <b>106</b> can be passed when inserting the end <b>109</b> of the handle into a cavity <b>104</b> in the side of the cam member <b>100</b>. In the illustrated embodiments, the outer wall (e.g., a vertical cross section thereof) of the first shoulder <b>82</b> entirely surrounds each cam-access opening <b>81</b>. This contributes to the particularly stable manner in which the illustrated cam members are nested in the wall.

0081The die holder <b>10</b> in <figref idref="DRAWINGS">FIGS. 1-8B</figref> has a plurality of spaced-apart cam-access openings <b>81</b>. This, however, is not required in other embodiments.

0082<figref idref="DRAWINGS">FIG. 3</figref> provides a fairly detailed view of one exemplary cam member <b>100</b> that can be used. This cam member <b>100</b> has a first exterior wall section <b>105</b> that is generally planar, and a second exterior wall section <b>107</b> that is convex. The convex wall section here is contiguous to the generally planar wall section, although this is not required. To initiate the die holder's camming action, the cam member <b>100</b> is rotated from a first configuration (shown in <figref idref="DRAWINGS">FIG. 8A</figref>), where the generally planar wall section <b>105</b> directly faces the locking bar <b>70</b>, to a second configuration (shown in <figref idref="DRAWINGS">FIG. 8B</figref>), where the convex wall section <b>107</b> directly faces and bears forcibly against the locking bar. As noted above, the cam member <b>100</b> in <figref idref="DRAWINGS">FIG. 19</figref> can have the same shape (e.g., the same wall sections <b>105</b>, <b>107</b>, head <b>101</b>, and neck <b>102</b>) as the cam members <b>100</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>. It can also rotate (so as to cam with the locking bar) in the same manner described above for the cam members <b>100</b> in <figref idref="DRAWINGS">FIG. 3</figref>.

0083The cam member <b>100</b> can optionally have a major diameter and a minor diameter. (A major diameter, of course, is greater than a minor diameter.) In embodiments like those of <figref idref="DRAWINGS">FIGS. 3</figref>, <b>19</b>, and <b>20</b>-<b>23</b>, the minor diameter is perpendicular to the generally planar wall section <b>105</b>, and the major diameter is perpendicular to the convex wall section <b>107</b>. The major diameter may be greater than the minor diameter by, for example, at least 1/36 inch, or by at least 1/18 inch.

0084Thus, in the embodiments of <figref idref="DRAWINGS">FIGS. 1-8B</figref>, a plurality of cam members <b>100</b> are received in respective cavities <b>119</b> spaced-apart along a length of the die holder's first shoulder <b>82</b>. Each illustrated cam member <b>100</b> has an opening <b>104</b> into which one end <b>109</b> of a manually-operable handle <b>106</b> can be inserted, as noted above. In these embodiments, each cam member <b>100</b> can be caused to cam with the locking bar <b>70</b> by inserting the end <b>109</b> of the handle <b>106</b> into the cavity <b>104</b> in such cam member and then moving the handle in a horizontal manner (see <figref idref="DRAWINGS">FIGS. 8A</figref>, <b>8</b>B).

0085In the embodiments described above, the die holder includes a camming actuator unit. Some of the related drawings show embodiments wherein this camming actuator unit is adapted for being (or is) attached removably to the die holder's base. This, however, is not required. For example, some embodiments involve the camming actuator unit being adapted for removable attachment to another component of the die holder, to the lower table of a press brake, or to an adaptor or other mounting structure used to secure the die holder on the lower table of a press brake. Further, some embodiments involve the camming actuator unit being permanently attached to (e.g., being built into a block integral to) the die holder's base (<figref idref="DRAWINGS">FIGS. 18-23</figref>), to another component of the die holder, to the lower table of a press brake, or to an adaptor or other mounting structure used to secure the die holder on the lower table of a press brake.

0086In the exemplary embodiments of <figref idref="DRAWINGS">FIGS. 1-8B</figref>, the first shoulder <b>82</b> of the die holder is part of a manually-operable camming actuator unit attached removably to the die holder's base <b>62</b>. In some embodiments of this nature, the die holder <b>10</b> is also provided with a hydraulically-operable actuator unit adapted for being attached removably to the die holder's base <b>62</b> (i.e., once the manually-operable camming actuator unit has been removed from the base). In these embodiments, when the hydraulic actuator unit HOA is operably connected to the die holder's base <b>62</b>, the die holder can be operated such that, in response to delivering a sufficient pressure of hydraulic fluid into a hydraulic line HL of the actuator unit HOA, at least one moveable body MB (optionally carried by an inner wall <b>85</b> of the actuator unit HOA) bears forcibly against the locking bar <b>70</b> and thereby moves the locking bar toward the second shoulder <b>64</b> of the die holder.

0087Thus, in some embodiments, the die holder <b>10</b> is provided with (e.g., is part of a combination including) both a mechanically-operable actuator unit MOA and a hydraulically-operable actuator unit HOA. Preferably, the two units MOA, HOA are separate components that can be selectively attached to the die holder (e.g., to the die holder's base <b>62</b>). In combination embodiments of this nature, both actuator units MOA, HOA may be packaged or otherwise bundled together (optionally with the blocks <b>60</b>, <b>80</b>, locking bar <b>70</b>, and/or other components) and/or delivered/transported to a customer together.

0088In <figref idref="DRAWINGS">FIGS. 1</figref>, <b>2</b>, <b>9</b>, and <b>10</b>, it can be appreciated that the illustrated die holder <b>10</b> can be used selectively with either a manually-operable actuator unit MOA or with a hydraulically-operable actuator unit HOA. In more detail, the die holder <b>10</b> in these embodiments is adapted for conversion (i.e., it is convertible) between a first operatively-assembled configuration (exemplified in <figref idref="DRAWINGS">FIG. 1</figref>) that includes the manually-operable actuator unit MOA and a second operatively-assembled configuration (exemplified in <figref idref="DRAWINGS">FIG. 9</figref>) that includes the hydraulically-operable actuator unit HOA.

0089Convertible die holder embodiments are advantageous in that they can be readily changed from being manually actuatable to being hydraulically actuatable, or vice versa. Thus, a press brake operator can assemble the die holder one way to allow for manual clamping and another way to allow for hydraulic clamping.

0090In some convertible die holder embodiments, the die holder <b>10</b> comprises a base <b>62</b>, a shoulder <b>64</b>, a locking bar <b>70</b>, a rigid fastening system <b>400</b>, and a resilient fastening system <b>300</b>. This group of components can be provided in a combination/embodiment that does not actually include either or both actuator units, although one of them would, of course, be used during operation.

0091In the present embodiments, a block (optionally a single, integral block) <b>60</b> defines base <b>62</b> and shoulder <b>64</b>. As is perhaps best seen in <figref idref="DRAWINGS">FIG. 10</figref>, the base <b>62</b> and shoulder <b>64</b> together may have a generally L-shaped configuration, although this is not required. Shoulder <b>64</b> preferably has a clamping wall <b>65</b>. The locking bar <b>70</b> (described above) preferably has a clamping wall <b>75</b> as well.

0092The convertible die holder preferably includes a rigid fastening assembly <b>400</b> that can (i.e., is adapted to) rigidly attach the block <b>60</b> (optionally the base <b>62</b>), as desired, either to the manually-operable actuator unit MOA (optionally to a lower portion thereof) or to the hydraulically-operable actuator unit HOA (optionally to a lower portion thereof). The convertible die holder preferably also includes a resilient fastening assembly <b>300</b> that can (i.e., is adapted to) resiliently attach the locking bar <b>70</b>, as desired, either to the manually-operable actuator unit MOA (optionally to an upper portion thereof) or to the hydraulically-operable actuator unit HOA (optionally to an upper portion thereof).

0093When provided, the rigid fastening system <b>400</b> preferably includes a plurality of fastener openings <b>402</b> defined by the base <b>62</b> and configured to be alignable, as desired, either with corresponding openings <b>403</b> in the lower portion of the manually-operable actuator unit MOA or with corresponding openings <b>403</b> in the lower portion of the hydraulically-operable actuator unit HOA. Preferably, the rigid fastening system <b>400</b> also includes a plurality of rigid fasteners <b>405</b> each adapted to be extended through one of the fastener openings <b>402</b> defined by the base <b>62</b> and into an aligned one of the corresponding openings <b>403</b> in, as desired, either the lower portion of the manually-operable actuator unit MOA or the lower portion of the hydraulically-operable actuator unit HOA. The fasteners <b>405</b>, for example, can be cap screws (e.g., socket head cap screws), such as M8-1.25 socket head cap screws. This example, of course, is by no means limiting, as other fasteners can be used.

0094The resilient fastening system <b>300</b>, when provided, preferably includes a plurality of fastener openings <b>303</b> defined by the locking bar <b>70</b> and configured to be alignable, as desired, either with corresponding openings <b>302</b> in the upper portion of the manually-operable actuator unit MOA or with corresponding openings <b>302</b> in the upper portion of the hydraulically-operable actuator unit HOA. Preferably, the resilient fastening system <b>300</b> also includes a plurality of fasteners <b>305</b> each coupled with a spring member <b>307</b> and each adapted to be extended through one of the openings <b>302</b> in, as desired, either the upper portion of the manually-operable actuator unit MOA or the upper portion of the hydraulically-operable actuator unit HOA and into an aligned one of the fastener openings <b>303</b> in the locking bar <b>70</b>. The fasteners <b>305</b>, for example, can be shoulder bolts, such as M8×16 mm shoulder bolts with an M6 thread. Music wire gage springs can be used as the spring members <b>307</b>. Other fasteners and springs can be used, of course, as these examples are by no means limiting.

0095<figref idref="DRAWINGS">FIGS. 9-14</figref> show one example of a hydraulic actuator unit HOA. In <figref idref="DRAWINGS">FIG. 9</figref>, the hydraulic actuator unit HOA is operably connected to the base <b>62</b> of the die holder <b>10</b>. Here, the die holder's first shoulder <b>82</b> is part of the hydraulic actuator unit HOA. This shoulder <b>82</b> is defined by a block <b>80</b>, which in the present embodiments preferably is not integral to (i.e., is a different body than) the block <b>60</b> comprising the die holder's base <b>62</b> and second shoulder <b>64</b>. Here again, the block <b>80</b> preferably is formed of metal or another rigid material. For example, P20 grade prehard material with a hardness of 28-32 and nitrided surface treatment to a 70 HRC can be used. Of course, other materials can be used, and this example is by no means limiting.

0096In the present figures (as well as in <figref idref="DRAWINGS">FIGS. 1-8B</figref>, <b>15</b>A-<b>17</b>, and <b>24</b>-<b>26</b>), block <b>80</b> is adapted for being removably attached to block <b>60</b>. These blocks <b>60</b>, <b>80</b> can be removably attached to each other in different ways. As noted above, one option involves a plurality of fasteners <b>405</b> that can be extended through respective openings <b>402</b> in the die holder's base <b>62</b> and into corresponding openings <b>403</b> in block <b>80</b>. More generally, though, it should be appreciated that many different removable fastening systems can be used.

0097When the convertible die holder is in its second operatively-assembled configuration, the hydraulic actuator unit HOA preferably can be operated such that, in response to delivering a sufficient pressure of hydraulic fluid into a hydraulic line HL of the actuator unit HOA, at least one moveable body MB (optionally carried by the actuator unit HOA) bears forcibly against the locking bar <b>70</b>, thereby moving the locking bar toward the die holder's second shoulder <b>64</b>. In some cases, the locking bar <b>70</b> is resiliently biased toward the hydraulic actuator unit HOA (e.g., toward block <b>80</b>) such that the locking bar is held resiliently against the hydraulic actuator unit (e.g., against inner surface <b>85</b> of block <b>80</b>) unless a sufficient pressure of hydraulic fluid is delivered into the hydraulic line HL.

0098In some of the present embodiments, the hydraulic actuator unit HOA includes a plurality of hydraulically-actuated moveable bodies MB that (when the actuator unit HOA is operatively assembled with the die holder) are adapted to move (optionally in a plane that is generally or substantially horizontal) toward the die holder's channel <b>55</b> (i.e., when actuated). Thus, the moveable bodies (e.g., pistons) MB of the hydraulic actuator unit HOA may move directly toward the channel <b>55</b> in a horizontal direction in response to delivery of sufficient hydraulic fluid into the hydraulic actuator unit. In some of these embodiments, the moveable bodies MB do not bear directly against the die's tang T during clamping, but rather are adapted to bear against a locking bar <b>70</b>, which then bears against the die's tang to deliver the die holder's clamping force.

0099<figref idref="DRAWINGS">FIG. 9</figref> depicts a hydraulic actuator unit HOA operably connected to the base <b>62</b> of the die holder. Here, a hydraulic line HL extends through block <b>80</b>. The hydraulic line HL can optionally extend along an axis lying in a horizontal plane that passes through the die holder's channel <b>55</b> (and/or through clamping walls <b>65</b>, <b>75</b>), although this is by no means required. In some embodiments, the hydraulic line HL is defined by the block <b>80</b> itself (e.g., by a metal wall thereof). These embodiments avoid having (i.e., are devoid of) a resilient bladder, hose, or tube defining the hydraulic line. When it is desired to initiate the die holder's clamping action, hydraulic fluid (e.g., oil) is delivered through the hydraulic line HL and into a plurality of hydraulic reservoirs HR defined by block <b>80</b> (e.g., by a metal wall thereof). Reference is made to <figref idref="DRAWINGS">FIG. 14</figref>. The hydraulic fluid then bears forcibly against moveable bodies (such as pistons) MB that are in fluid communication with the hydraulic fluid in the reservoirs HR. This causes each moveable body MB to move toward an extended position (exemplified in <figref idref="DRAWINGS">FIG. 14</figref>). As the bodies MB move to their extended positions, they bear forcibly against the locking bar <b>70</b>, thus forcing the locking bar to move toward the die holder's second shoulder <b>64</b>.

0100In <figref idref="DRAWINGS">FIG. 14</figref>, block <b>80</b> defines a cavity CV in which the illustrated moveable body MB is disposed. One part of the cavity CV receives the moveable body MB, while another part of the cavity serves as the hydraulic reservoir HR. The illustrated moveable body MB carries an O-ring and is retained in the cavity CV by virtue of a ring R. These features, however, are merely exemplary.

0101In <figref idref="DRAWINGS">FIGS. 9-13</figref>, the hydraulic actuator unit HOA includes a plurality of moveable bodies MB. These moveable bodies MB are spaced-apart along the length of the die holder's first shoulder <b>82</b>. In other embodiments, though, a single moveable body may be provided.

0102Thus, in embodiments like those of <figref idref="DRAWINGS">FIGS. 9-13</figref>, the die holder's clamping action results when a plurality of moveable bodies (optionally piston-like moveable bodies) MB are forced hydraulically to move from retracted to extended positions. (In the process, the bodies MB may move toward the direction of the die holder's channel <b>55</b>). The extended position of one exemplary body MB is shown in <figref idref="DRAWINGS">FIG. 14</figref>. Here, the moveable body MB has a rear wall RS against which hydraulic fluid bears forcibly when the hydraulic actuator is operated. In more detail, when hydraulic pressure in the reservoir HR reaches a sufficiently high level, the moveable body MB is forced to slide to its extended position. As the body MB moves in this manner, a leading wall LS of the moveable body MB bears forcibly against the locking bar <b>70</b> (e.g., against wall <b>74</b>), thereby causing the locking bar to move toward the die holder's second shoulder.

0103Thus, certain embodiments provide a rigid block <b>80</b> that defines the first shoulder <b>82</b> of the die holder, where a hydraulic line HL is built into the rigid block <b>80</b>, where a moveable locking bar <b>70</b> is located between the first shoulder <b>82</b> and the die holder's channel <b>55</b>, where a plurality of moveable bodies (optionally pistons) MB carried by the block <b>80</b> are adapted to move to extended positions (in the process bearing forcibly against the locking bar <b>70</b> and moving it toward the die holder's second shoulder <b>64</b>) in response to delivery of a sufficient pressure of hydraulic fluid through the hydraulic line HL in the rigid block <b>80</b> (which is part of a hydraulic actuator unit). May different embodiments of this nature can be provided.

0104Preferably, the locking bar <b>70</b> is resiliently biased toward the die holder's first shoulder <b>82</b> such that, when the moveable bodies MB are in their retracted positions, the locking bar is held resiliently against the first shoulder <b>82</b>. Thus, the locking bar <b>70</b> may have a default position in which it is held against the die holder's first shoulder <b>82</b> unless the hydraulic actuator unit HOA is operated (or the resilient bias on the locking bar is otherwise overcome). Thus, the die holder can have a fully-open default configuration, which can facilitate due positioning.

0105Thus, certain embodiments of the invention provide two rigid walls (e.g., block <b>80</b> and bar <b>70</b>) located side-by-side, where both of these walls are located on the same side of the die holder's channel <b>55</b> while another rigid wall (e.g., shoulder <b>64</b>) is located on an opposite side of the channel <b>55</b>. In embodiments of this nature involving a hydraulic actuator unit HOA, of the two side-by-side blocks, the one (e.g., block <b>80</b>) furthest from the channel <b>55</b> preferably is part of the actuator unit HOA while the one (e.g., bar <b>70</b>) closest to the channel <b>55</b> preferably is caused to move (e.g., toward the rigid wall on the opposite side of the channel) in response to hydraulically-actuated movement of a plurality of moveable bodies (e.g., pistons) MB carried by that one of the two side-by-side blocks furthest from the channel.

0106Some embodiments of the invention provide a press brake die holder <b>10</b> having a die-contact body <b>300</b> that delivers a downward force to the tang T of a die D when the tang is positively clamped by the die holder. This downward force urges the tang T downwardly toward a base <b>62</b> of the die holder. (As noted above, the base <b>62</b> typically extends between the confronting clamping walls <b>65</b>, <b>75</b> of the die holder.) Embodiments of this nature are advantageous in that the downward force, or “die-pulling force”, tends to offset any bow, twist, or camber of the die. This die-pulling force is also advantageous in that it helps pull down the sectional pieces when the die holder is used to clamp sectional tooling.

0107In some of the present die-pulling embodiments, the die holder <b>10</b> has a height (from bottom surface <b>60</b>B to top surface <b>66</b>) of less than 4 inches, less than 3 inches, or less than about 2.6 inches. Additionally, the die holder's width (from surface <b>80</b>F to surface <b>60</b>R) can optionally be within any of the width ranges noted herein.

0108Preferably, the die holder <b>10</b> is adapted to deliver the downward force to the tang even when the tang's opposed clamping surfaces <b>144</b>, <b>146</b> consist of (i.e., simply are) parallel planar surfaces. Exemplary tangs T of this nature are shown, for example, in <figref idref="DRAWINGS">FIGS. 2</figref>, <b>10</b>, and <b>21</b>-<b>23</b>. During positive clamping of the die's tang T between the two confronting walls <b>65</b>, <b>75</b>, the die-contact body <b>300</b> preferably delivers the downward force as a frictional force. Some of the present embodiments involve both confronting walls <b>65</b>, <b>75</b> carrying die-contact bodies <b>300</b> that are adapted to deliver the downward force. In embodiments of this nature, the die-contact bodies <b>300</b> can optionally be mounted on the confronting walls <b>65</b>, <b>75</b> so as to have limited range freedom of movement relative to the confronting walls.

0109In some of the present embodiments, the die holder <b>10</b> includes a die-contact body <b>300</b> that is moveable between an upper position and a lower position. Here, the die-contact body <b>300</b> can be optionally be resiliently biased toward its upper position by a spring member <b>340</b>. The die-contact body <b>300</b> preferably is exposed to (e.g., mounted next to) the die holder's channel <b>55</b>, and preferably has a contact surface <b>350</b> (which can optionally be planar) that engages the tang T of a die D during the clamping action of the die holder.

0110<figref idref="DRAWINGS">FIGS. 24 and 25</figref> depict exemplary embodiments wherein the die-contact bodies <b>300</b> are wedge members WM. During positive clamping of the die's tang T between the die holder's two clamping walls <b>65</b>, <b>75</b>, the illustrated wedge members WM move downwardly (e.g., generally toward the die holder's base <b>62</b>) relative to the clamping walls <b>65</b>, <b>75</b>. Here, each wedge member WM can optionally have a default position that is the highest position in such wedge member's limited range of motion. Each illustrated wedge member WM is held in this default position by a spring member <b>340</b> (which can be received, for example, in a bore <b>325</b>B defined by block <b>60</b>). When the tang T of a die D is positioned in the die holder's channel <b>55</b>, and one of the confronting walls is moved toward the other confronting wall (so as to positively clamp the die's tang therebetween), the wedge members WM cam with corresponding cam surfaces <b>75</b>C (shown as angled surfaces) of the die holder. This camming action causes the wedge members WM to move downwardly, while sliding along (i.e., camming with) the die holders' cam surfaces <b>75</b>C. Preferably, this camming action continues at least until one or more loading surfaces <b>21</b>, <b>221</b> of the die's tang T is/are pulled firmly against the die holder (e.g., at least until tang shoulder surfaces <b>21</b> engage die holder surfaces <b>66</b>, <b>76</b>, or at least until tang bottom surface <b>221</b> engages the die holder's base <b>62</b>). This camming action between the wedge members WM and the die holder's cam surfaces <b>75</b>C may continue (at the same time, the contact surfaces <b>350</b> of the wedge members WM may slide downwardly against the die's tang) for some time after one or more loading surfaces <b>21</b>, <b>221</b> of the die's tang T is/are pulled firmly against the die holder. Perhaps optimally, this camming action ceases once planar vertical surfaces <b>65</b>′, <b>75</b>‘of the die holder’s clamping walls <b>65</b>, <b>75</b> clamp forcibly upon the die's tang T.

0111In the embodiments of <figref idref="DRAWINGS">FIGS. 24 and 25</figref>, a first group of wedge members WM are mounted on a locking bar <b>70</b>, which is laterally moveable itself (i.e., toward and away from the die holder's second shoulder <b>64</b>). Here, the wedge members WM of the first group project from the locking bar <b>70</b> into the channel <b>55</b>, and the locking bar is located between the channel and the die holder's first shoulder <b>82</b>. The die holder's first shoulder <b>82</b> is adapted to force (hydraulically, by camming, etc.) the locking bar <b>70</b> to move toward the die holder's second shoulder <b>64</b>. Exemplary configurations, manners of lateral movement, etc., have been described for the locking bar <b>70</b>.

0112When provided, the wedge member(s) WM can have many different configurations. In some cases, the contact surface <b>350</b> is oriented at an oblique angle relative to the wedge member's camming surface <b>301</b>, which slides along cam surface <b>75</b>C as the tang T of the die D is forcibly clamped by the die holder.

0113Each wedge member WM or other die-contact body <b>300</b> can optionally be formed of metal or another rigid material. In one group of embodiments, the die holder includes one or more die-contact bodies <b>300</b> each comprising (optionally having a portion comprising) polymer, perhaps together with a filler. One useful polymer is nylon, such as nylon 66. Torlon or ultra high molecular weight polyethylene may also be suitable. If desired, the polymer can comprise a filler, such as glass fibers. Nylon 66 with 20% glass filler may be suitable. The die-contact body <b>30</b> may, in some cases, consist essentially of any of the noted materials.

0114The invention provides some embodiments wherein a press brake die holder is provided with a resilient body <b>40</b> that engages the tang T of a die D when the die holder closes upon the die's tang. The resilient body <b>40</b> is another useful type of die-contact body <b>300</b>. When provided, the resilient body <b>40</b> preferably is configured such that when the die holder closes upon the die's tang T, the resilient body delivers a net downward force to the tang. This downward force, or “die-pulling force”, urges the die downwardly toward the base <b>62</b> of the die holder.

0115In the present embodiments (those involving a resilient body <b>40</b> or any other die-contact body <b>300</b>), the die holder can take many different forms. It can have one of the designs disclosed above (a design with camming action on a locking bar, and/or a design convertible between manually and hydraulically actuatable states, etc.). More generally, it can have any die holder design that provides positive clamping.

0116The present embodiments involve a die holder with two confronting walls between which a die's tang can be positioned. At least one of the two walls (a “desired” one of the walls) is adapted for being moved toward the other wall, e.g., so as to positively clamp the tang when the tang is positioned between the two walls. In the present embodiments, the die holder is provided with a resilient body that delivers a net downward force to the tang during clamping (i.e., when the tang is positively clamped between the two walls). This net downward force urges the tang downwardly toward the die holder's base <b>62</b>, which preferably extends between the two clamping walls of the die holder. This can be appreciated by referring to <figref idref="DRAWINGS">FIGS. 15A</figref>, <b>15</b>B, and <b>17</b>.

0117In some embodiments, the resilient body (or “plug”) <b>40</b> is an elongated resilient bar extending lengthwise along the desired wall. Reference is made to <figref idref="DRAWINGS">FIGS. 1</figref>, <b>2</b>, <b>10</b>, and <b>23</b>. Embodiments of this nature are advantageous, for example, because they enable the die holder <b>10</b> to clamp sectional tooling.

0118The resilient bar <b>40</b> has a face <b>45</b> that engages the tang T during clamping (i.e., when the tang is positively clamped between the walls <b>65</b>, <b>75</b>). Preferably, this face <b>45</b> is adapted to deliver a net downward force to the tang during clamping. To accomplish this, the resilient body <b>40</b> can have a variety of different configurations and orientations. For example, the resilient body <b>40</b> can be downwardly oriented and/or its face <b>45</b> can be downwardly angled (optionally forming an oblique angle with respect to one of the clamping walls, such as clamping wall <b>75</b>). If desired, part (or all) of the face <b>45</b> may form an angle of at least 2 degrees, at least 3 degrees, or at least five degrees relative to the clamping wall <b>65</b>, <b>75</b> on which it is carried. The face <b>45</b> may have a generally downwardly-facing plan or configuration (as shown), a generally downwardly-facing convex configuration, a generally downwardly-facing polygonal configuration, a generally downwardly-facing irregular configuration, etc. If desired, the entire face <b>45</b> (or substantially the entire face) can define a downwardly angled surface.

0119In certain embodiments, as shown in <figref idref="DRAWINGS">FIGS. 15A and 17</figref>, the downward orientation (e.g., downward angle) of the face <b>45</b> is achieved by mounting the resilient body <b>40</b> in a cavity <b>71</b> that opens (through a clamping wall/to the channel) in a downward and sideward direction. The cavity <b>71</b> is defined by one of the clamping walls (optionally by clamping wall <b>75</b>). In <figref idref="DRAWINGS">FIGS. 15A and 17</figref>, the cavity <b>71</b> is downwardly and sidewardly angled from its closed end to its open end (which opens into the channel <b>55</b>), so as to cause face <b>45</b> to be generally downwardly angled (or “downwardly and sidewardly angled”). Alternatively, the cavity <b>71</b> can extend horizontally through one of the clamping walls <b>65</b>, <b>75</b>, and the resilient body <b>40</b> can be shaped so as to have its face <b>45</b> generally downwardly angled (or “downwardly and sidewardly angled”).

0120In connection with the term “net downward force”, it is contemplated that, for some embodiments, when the resilient body is compressed during clamping, part of the body (e.g., an upper part) may deliver a small upward force component (e.g., frictional force), even though the overall vertical force will be downward (i.e., the downward force component will be greater than any upward force component).

0121The die holder <b>10</b> has an elongated configuration. Its confronting walls <b>65</b>, <b>75</b>, for example, commonly each have a length of at least 4 inches, or at least 5 inches. For embodiments involving an elongated resilient bar, the resilient bar desirably extends along at least 75% of the length of the wall on which it is carried. Perhaps most preferably, the resilient bar extends along the entire length (or substantially the entire length) of the desired wall. Embodiments of this nature are particularly advantageous, for example, in applications where the die holder is used to clamp sectional tooling.

0122As noted above, the resilient body <b>40</b> preferably is received in a cavity <b>71</b> formed by one of the confronting walls of the die holder. Part of the resilient body <b>40</b> protrudes outwardly from the cavity <b>71</b>. It may be preferred that the resilient body <b>40</b> extend into the channel by a distance of between about 0.001 inch and about 0.015 inch. Thus, the resilient body protrudes into the channel <b>55</b> by a certain distance, and the width of the channel measured from the face <b>45</b> of the resilient body <b>40</b> to the confronting wall is therefore slightly less than the width of the channel measured between the clamping walls <b>65</b>,<b>75</b>. This way, when the tang is positively clamped between the two walls, the resilient body compresses slightly.

0123In the illustrated embodiments, the cavity <b>71</b> that receives the resilient body <b>40</b> is a longitudinal cavity defined by the locking bar <b>70</b>. Here, the cavity <b>71</b> is formed so as to open through the locking bar's clamping wall <b>75</b> and into the channel <b>55</b>. The cavity <b>71</b> can be made using any convenient means, e.g., a Woodruff cutter. In the illustrated embodiments, the cavity <b>71</b> extends along the die holder's elongated direction (along the longitudinal axis of the die holder), that is, parallel to the channel <b>55</b>.

0124As noted above, the resilient body <b>40</b> preferably protrudes into the channel <b>55</b> a sufficient distance to encounter and resiliently press against a confronting wall <b>146</b> of the die's tang T, thus urging the tang's other wall <b>144</b> into contact with the die holder's other clamping wall <b>65</b>. The resilient body <b>40</b> may be a single length of material, such as a polyurethane elastomer, or it may comprise a plurality of discrete sections. Thus, although a single plug <b>40</b> is shown, two or more plugs can be used. Some embodiments involve at least one resilient body <b>40</b> carried by each of the two clamping walls <b>65</b>, <b>75</b>.

0125A variety of materials can be used for the resilient body <b>40</b>. Polyurethane or other resilient polymers may be used. Thus, in some cases, the resilient body <b>40</b> comprises (or consists essentially of) polyurethane or another resilient polymer. In one group of embodiments, urethane is used. Thus, the resilient body <b>40</b> can optionally comprise, consist essentially of, or be formed of urethane.

0126The face <b>45</b> of the resilient body <b>40</b> that protrudes into the channel <b>55</b> can optionally have a hardness in the range of 60-95 Durometer A, such as a hardness in the range of about 85-90 Durometer A. Put another way, the resilient body <b>40</b> may be sufficiently resilient so its face <b>45</b> can be slightly dented by fingernail pressure.

0127In the illustrated embodiments, the resilient body <b>40</b> has an elongated bar shape. While this is advantageous, the resilient body <b>40</b> can have many different configurations. For example, it can take the form of a button, sphere, or the like. In such cases, the resilient body <b>40</b> preferably is configured to deliver a net downward force on the tang T of a die D during clamping.

0128If desired, an adhesive can be provided between the resilient body <b>40</b> and the cavity <b>71</b>. This may be desired to prevent the resilient body <b>40</b> from escaping the cavity <b>71</b>. Additionally or alternatively, the cavity <b>71</b> can be sized and/or shaped so as to grip and retain the resilient body <b>40</b> in the cavity <b>71</b> without any adhesive or other attachment means.

0129In some of the present embodiments, the die holder <b>10</b> has a first shoulder <b>82</b>, a second shoulder <b>64</b>, a base <b>62</b>, and an elongated channel <b>55</b>. In these embodiments, the resilient body may be carried by an elongated locking bar <b>70</b> (such that the “desired wall” is defined by the locking bar, and the “other wall” is defined by the second shoulder <b>64</b>). As noted above, the locking bar <b>70</b> preferably is adapted for movement toward the second shoulder <b>64</b> so as to positively clamp the tang T of a die D. Thus, the locking bar <b>70</b> preferably has a clamping wall <b>75</b> facing the die holder's second shoulder <b>64</b>, and this wall <b>75</b> preferably defines the cavity <b>71</b> in which the resilient body <b>40</b> is received. In other cases, though, clamping wall <b>65</b> defines the cavity <b>71</b>. Either way, part of the resilient body <b>40</b> preferably protrudes from the cavity <b>71</b> into the channel <b>55</b> so as to be engageable with the tang T during clamping.

0130The invention also provides embodiments wherein coating features are incorporated into a press brake die holder. In these embodiments, the die holder can take many different forms. It may be one of the designs disclosed above (a design with camming action on a locking bar, and/or a design convertible between manually and hydraulically actuatable states, etc.). However, the present coating features can be incorporated into any press brake die holder. The coating features are particularly advantageous for die holders that offer positive clamping and have parts (e.g., walls) that slide against one another during clamping.

0131Generally, the die holder <b>10</b> of the present embodiments has a coating over at least one surface. In some cases, the coating is provided on a moveable surface (e.g., a surface that moves during clamping or unclamping) of the die holder.

0132Typically, the die holder <b>10</b> has a block <b>60</b> that includes a base <b>62</b> and a shoulder <b>64</b>. The base <b>62</b> and shoulder <b>64</b> together may have a generally L-shaped configuration, as noted above. In some cases, the die holder <b>10</b> includes an elongated locking bar <b>70</b>. When provided, the locking bar <b>70</b> preferably has a first clamping wall <b>75</b>, while shoulder <b>64</b> preferably has a second clamping wall <b>65</b>.

0133In the present embodiments, coating may be provided on one or more of the following surfaces: (1) the locking bar's bottom wall <b>73</b>, which preferably is adapted to slide along the die holder's base <b>62</b> during clamping and unclamping; (2) an upwardly-facing surface <b>63</b> of the die holder's base; (3) one or each of the die holder's upwardly-facing loading surfaces <b>66</b>, <b>76</b>, along which loading surfaces <b>21</b> of certain types of dies D are adapted to slide (e.g., during positioning of the die when the die holder is unclamped).

0134In certain embodiments, the clamping wall <b>75</b> of the locking bar <b>70</b> is defined by uncoated metal. Additionally or alternatively, the die holder's second clamping wall <b>65</b> can be defined by uncoated metal. Such uncoated clamping wall features can be provided to reduce the likelihood of any slippage between the die's tang and the die holder's clamping walls. It is contemplated, though, that some embodiments may involve coatings on the clamping walls, perhaps high-friction-coefficient coatings that facilitate clamping.

0135In one group of embodiments, coating <b>770</b> is provided on the locking bar's bottom surface <b>73</b>, coating <b>670</b> is provided on the die holder's base <b>60</b> (e.g., on an upwardly-facing surface <b>63</b>), and on the die holder's upwardly-facing loading surfaces <b>66</b>, <b>76</b>. Perhaps ideally, coating <b>870</b> is also provided on block <b>80</b>. Reference is made to <figref idref="DRAWINGS">FIG. 17</figref>.

0136When provided, the coating can optionally be a dry lubricant coating. For example, the coating can comprise nickel (e.g., nickel alloy) and/or a low friction polymer. In some cases, the coated surface has one or more of the following features: (i) a coefficient of static friction below 0.35, below 0.3, or even below 0.2; (ii) a coefficient of dynamic friction below 0.3, below 0.25, below 0.18, or even below 0.1. Useful dry lubricant coatings are available commercially from, for example, General Magnaplate Corporation (Linden, N.J., USA) and Poeton Industries, Ltd. (Gloucester, England). As one example, the coating can be a NEDOX® coating.

0137In some cases, the coating comprises a nitride and/or a carbide. One commercially available nitride coating is the Nitrex® coating, which is a high endurance surface enhancement available commercially from Nitrex, Inc. (Aurora, Ill., USA). Particularly useful nitriding and nitrocarburizing enhancements are described in U.S. Pat. No. 6,327,884, the salient teachings of which are incorporated herein by reference.

0138Nitriding and nitrocarburizing processes are known in the field and need not be described in great detail. Reference is made to U.S. Pat. Nos. 4,790,888 and 4,268,323, the teachings of which regarding such enhancements are incorporated herein by reference. The latter patent refers to the use of a fused salt bath to enable nitrogen and carbon to diffuse into the surface of a steel piece suspended in the bath to form a carbonitride case. Reference is made also to U.S. Pat. No. 5,234,721 (referring to methods of forming carbonitride coatings), the teachings of which regarding such coatings are incorporated herein by reference.

0139Nitriding processes, both plasma (ion) nitriding and liquid nitriding, are described in detail in the ASM Handbook prepared under the direction of the ASM International Handbook Committee, Revised vol. 4<i>: Heat Treating</i>, pp. 410-424 (1994), the teachings of which concerning nitriding enhancements are incorporated herein by reference. Plasma or ion nitriding involves the use of glow discharge technology to provide nascent nitrogen to the surface of a heated steel part. Here, the part is subjected to a nitrogen plasma in a vacuum chamber. Nascent nitrogen diffuses into the surface of the part to form an outer “compound” zone containing γ(Fe₄N) and ε(Fe_2,3N) intermetallics, and an inner “diffusion” zone which may be described as the original core microstructure with some solid solution and precipitation strengthening. Liquid nitriding involves immersing a steel part in a molten, nitrogen-containing fused salt bath containing cyanides or cyanates, e.g., NaCN or NaCNO. Tool components can be enhanced by liquid nitriding through a wide variety of commercial coating manufacturers, such as Metal Treaters Inc. of St. Paul, Minn., USA. The term coating includes discrete coatings on the surface of a part, diffusion of material into the part so as to enhance its surface, etc.

0140While a preferred embodiment of the present invention has been described, it should be understood that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.