Holding arrangement for punching tool insert

FIELD OF THE INVENTION

0001The invention relates to a holding arrangement for securing a punching tool insert in a recess opening of a holder with the aid of a ball, the ball being movably held in a conduit that extends obliquely to the recess opening and which opens into the recess opening, the width of the conduit opening at the recess opening being less than the ball diameter, and in the locked position the ball rests, under the influence of a compression spring, in an indentation in an outer face of the punching tool insert.

BACKGROUND OF THE INVENTION

0002As an example, one such holding arrangement is known by the name "ball-lock" and is used among other purposes in punching/embossing machines for large-scale mass production with a fixed tool arrangement. In this application, the known holding arrangements have the purpose of enabling rapid replacement of the tool insert, if the wear limit is reached or in the event of failure, without having to remove the holder from the machine.

0003Fundamental advantages of the above-described holding arrangement are the simple fastening of the tool insert in the holder, the secure hold against falling out that is achieved by self-locking, very good rotary angle adjustment and securing of the tool insert relative to the holder during the snap-in operation.

0004In the known versions, to hold the tool insert, the spring is defected inward as a unit over a plurality of thread courses mounted on the conduit wall. This makes it difficult to adapt the holding arrangement to other holders with a lesser depth, since a certain minimum spring trave! must be available in order, on the one hand to provide secure locking of the tool insert and on the other hand to push the ball back to a position that completely uncovers the tool insert so that it can be removed. Nor can the spring travel be lengthened by increasing the inclination of the conduit relative to the recess opening, because then the self-locking action for securing the punching tool insert may under some circumstances no longer exist.

0005From <patcit id="pcit0001" dnum="US5839183A"><text>US-A-5 839 183</text></patcit>, <patcit id="pcit0002" dnum="US5357835A"><text>US-A-5 357 835</text></patcit>, <patcit id="pcit0003" dnum="US4558620A"><text>US-A-4 558 620</text></patcit> and <patcit id="pcit0004" dnum="US3245654A"><text>US-A-3 245 654</text></patcit> it is known that, the upper opening of the conduit in the holder is covered by a holding element which forms an abutment for the compression spring.

0006With this arrangement, the spring need not be compressed over a certain length as a unit and secured to the conduit wall, so that compared to the known variants, considerable spring travel gains are achieved, which make it possible to use the holding arrangement in thinner holders. As a rule, it is not a problem to provide the holding element at a certain point on the top of the holder and optionally to remachine the receptacle for the holder in the machine tool.

SUMMARY OF THE INVENTION

0007An object of the present invention is to omit remachining.

0008According to the invention, this object is attained by a holding arrangement, in which the holding element is embodied as a key which is seated in a groove in the holder and with which the holder can be fixed in a defined way in the correct angular position in the receptacle of a punching machine. In many known holders, such as holders made by the Trumpf system, a key is provided on the top side of a calibration ring. In a holding arrangement of the invention this key is given the further function of forming an abutment for the compression spring. The groove for the key and the conduit for guiding the ball are fabricated in a vise, so that with the aid of the key and the holding arrangement of the invention, a defined angular position of the tool insert relative to the receptacle for the holder in the machine tool simultaneously exists without further action being taken.

0009As a further preferred provision to increase the spring travel, in a holder in accordance with or similar to the Trumpf system, the calibration ring is thicker than in normal holders, and the projection distance of the punching tool out of the holder is correspondingly less.

0010In the usual holders regrinding of the formed-on punching tool is possible in order to lower tool costs. In this case a considerable projection distance of the tool out of the holder is unavoidable. In contrast, the holding arrangement of the present invention allows the use of disposable tools in a re-usable holder, so that a considerable reduction in cost can be achieved compared to the holders previously made in one-piece with the punching tool, and remachining of the punching tool insert can be omitted. The punching tool insert is preferably provided with a coating that increases its service life, such as TiN. In the punching tool insert in the form of a disposable element, the coating can develop its full effect, since while a coating is also possible in the known holders, the requisite regrinding of the tool means that the optimal effect is achieved only in new tools.

0011In this connection, it is also a cost advantage that the costs for a coating do not depend on the area to be coated but rather on the volume of the workpiece, so that the small punching tool inserts can be coated in the region of the tool blade at substantially more favorable cost than integral holders with a formed-on tool.

0012In a further preferred embodiment of the invention, the shaft end of the punching tool insert behind the indentation, which for instance is a convex elongated rounded indentation, is shortened. The reduction in the length of the shaft end is available especially in very thin holders, in order to enable an introduction of force into the holder from the end face of the punching tool insert. By comparison, if recess openings are too deep, excessive weakening of the remaining material could occur.

0013In very thin holders, it can be expedient to provide a holding arrangement in which the indentation is adjoined by a groove which extends as far as the end of the shaft and is shallower and narrower than the indentation. This groove can make it possible to remove the tool insert from the recess opening even if the ball cannot be pushed all the way back into the conduit, for instance because it was not possible to achieve an adequate length of spring travel. It is understood that the groove must be embodied as correspondingly shallow and narrow, so that the hold of the tool insert in the holder to prevent it from falling out is assured under all circumstances, even under the tensile forces that occur in operation.

0014To make it possible to move the ball out of the locked position into a released position, in which the punching tool insert can be removed, openings or bores, for instance parallel or vertical to the recess opening, can be provided, through which bore a pin or the like can be introduced to press the ball back, counter to the force of the compression spring, into a position that uncovers the punching tool insert.

0015In a vertical arrangement an oblong slot is preferred, so that with the pin, using leverage, the ball can be moved into its unlocked position.

0016A further advantageous provision for making the process of disassembling the punching tool insert easier can be that the holder has a through bore which opens into the recess opening approximately centrally in the end face. By introducing an expulsion tool into this through bore, even solidly fixed punching tool inserts can easily be removed from the recess opening once the ball has been released.

BRIEF DESCRIPTION OF THE DRAWINGS

0017An exemplary embodiment of the invention will be described in detail below in conjunction with the accompanying drawings, wherein:

0018<figref idref="f0001">Fig. 1</figref> is a cross sectional view through a holder without a punching tool insert;

0019<figref idref="f0001">Fig. 2</figref> is a side view of the holder of <figref idref="f0001">Fig. 1</figref>;

0020<figref idref="f0001">Fig. 3</figref> shows a detail of the tool of <figref idref="f0001">Fig. 2</figref>;

0021<figref idref="f0002">Fig. 4</figref> is a side elevational view of a punching tool insert;

0022<figref idref="f0002">Fig. 5</figref> is a partial cross-sectional view taken along line 5-5 of <figref idref="f0002">Fig. 4</figref>; and

0023<figref idref="f0003">Fig. 6</figref> is a cross sectional view through a device for expelling a punching tool insert from the holder of <figref idref="f0001">Fig. 1</figref>.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0024<figref idref="f0001">Fig. 1</figref> shows a holder 10 for a punching tool insert (an example of which is shown in <figref idref="f0002">Figs. 4 and 5</figref>), which, as in the Trumpf system comprises a suitable shaft 14 and a calibration ring 16 so that it can be received in a punching machine. The calibration ring 16, which as will be described in further detail hereinafter, is thicker, compared to the usual tools of the Trumpf system wherein the holder and the tool insert are made in one piece. The calibration ring 16 is provided with a recess opening 18, into which the punching tool insert can be introduced with the end face of the tool insert resting on a bearing face 20 to transmit the punching forces to the holder.

0025A key 22 is secured in a groove 24 on the top of the calibration ring with the aid of a screw 26, which fixes the angular position of the holder 10 in the punching machine. At the same time, the inner end of the key covers an upper opening of a conduit 28, which is inclined at an angle α, which may be about 15°, in the calibration ring 16, such that this conduit opens at 30 into the recess opening 18. The width of the opening 30 into the recess opening 18 is less than the full width of the conduit 28. As a result, a ball 32 movably guided in the conduit 28 is prevented from falling out into the recess opening 18. The ball 32 is urged into the position shown in <figref idref="f0001">Fig. 1</figref> by a prestressed compression spring disposed in the conduit 28. In this position, the ball 32 protrudes with part of its circumference into the recess opening 18. The key 22 forms the abutment for the compression spring, which may be a helical spring, as shown at 42.

0026In the punching tool insert inserted in the recess opening 18, the ball 32 rests in an elongated rounded convex indentation in the surface of the tool insert. In conjunction with an inclination β of about 19 in the wall of the indentation, a self-locking effect ensues, which prevents the tool insert from falling out of the recess opening 18, even under the tensile forces occurring in operation. At the same time, the ball 32 assures angular alignment of the punching tool insert, so that in conjunction with the key 22, a defined position of the tool insert relative to the receptacle of the punching machine is obtained. To avoid production variations, it is expedient for the groove 24 for retaining the key 22 in the calibration ring 16 and the conduit 28 for receiving the ball 32 to be held in a vise.

0027A suitable tool insert 43 is shown in <figref idref="f0002">Figs. 4 and 5</figref>. This tool insert 43 is relatively short in length, for reasons described above. It includes a shaft 44 and an end face 45 which abuts bearing face 20 of recess opening 18. An indentation 46 for receiving the ball 32 in the locked position is curved in cross section and its walls extend downwardly at an angle β to the vertical of approximately 11°. An 11 angle of indentation 46, coupled with the 15° inclination of conduit 28 assures locking of the ball 32 in indentation 46. For easing insertion of tool insert 43 into recess opening 18, the tool insert includes a tapered portion 47 in the form of a conical guide extending downwardly from the shaft end 45. This conical guide 47 joins with indentation 46 at transition point 48 which, lying essentially on the circumference of shaft 44, can be felt as the shaft is pushed in and the ball 32 rides over it and snaps into its locking position in indentation 46.

0028Using the alignment key 22 as an abutment for the compression spring 42 disposed in the conduit 28 makes an adequate spring travel possible, even though, in comparison to similar holding devices calibration ring 16 is very thin. With this arrangement, the ball 32 can be moved back into a position in which the punching tool insert can be removed from the recess opening 18 without difficulty. A through bore 34 in the shaft 14 of the holder 10 optionally allows the introduction of an expulsion pin, for forcing out a tool insert that has become jammed. (See <figref idref="f0003">Fig. 6</figref>.)

0029To move the ball 32 out of its locking position into a released position counter to the load of the compression spring, a first opening, aligned parallel with the recess opening 18, is provided in the form of a bore 36, through which a pin can be introduced to force the ball 32 back up the conduit 28.

0030To enable moving the ball 32 into the released position when tool inserts in which the blade distances are greater than the diameter of the recess opening 18 to be used as well, a further, second opening 38 is provided, disposed transversely to the recess opening 18 and the bore 36. This second opening is in the form of an oblong slot 38, the width of which is narrower than the diameter of the ball 32, so as not to hinder the motion of the ball 32 in the conduit 28. By introducing a pin 40 (see <figref idref="f0001">Fig. 3</figref>), the ball can be lifted into the released position shown in <figref idref="f0001">Fig. 3</figref>, and optionally the outer edge of the oblong slot 38 can be used as a bearing surface for the pin 40 in order to achieve leverage (see also <figref idref="f0003">Fig. 6</figref>).

0031The punching tool insert used with the present invention, an example of which is shown in <figref idref="f0002">Figs. 4 and 5</figref>, has a shorter shaft than the inserts used in comparable, previously known holding arrangements. This is because otherwise, i.e., if the shaft were longer, the transitional region between the shaft 14 and the calibration ring 16 would be weakened too much to allow the forces occurring in punching to be reliably transferred to the punching machine. In comparison with the known holders that have a formed-on tool, the projection distance of the punching tool insert out of the recess opening 18 is reduced to the extent by which the calibration ring 16 is made thicker. Since the punching tool insert is intended as a disposable tool without regrinding, this reduced length is not significant.

0032<figref idref="f0003">Fig. 6</figref> shows the removal of the punching tool insert from the holder 10 with the aid of a changing device 50. The changing device 50 has a receptacle 52, which in terms of geometry is made similar to the receptacle of a punching machine, with a resilient locking bolt element 54 that engages the recess 55 provided in the shaft 14 of the holder 10 to fix the holder 10 on the device 50. A lever 56 of the changing device 50 acts on a linearly guided expulsion element 58, which has a pin 60 that protrudes through the through bore 34 as far as the inside of the recess opening 18 and that by actuation of the lever 56 can expel the punching tool insert. First, however, it is necessary for the pin 40 to be introduced through the oblong slot 38, and by pivoting about the pivot point described above for the ball 32 to be moved into its retracted position, in which the punching tool insert is removable. In tool inserts with a small blade diameter, it is also possible to introduce the pin 40 through the opening 36 from the underside of the calibration ring 16, in order to unlock the ball 32 before the tool insert is forced out of the recess opening 18 with the aid of the lever 56.

0033The introduction of a new tool insert is done by simply pressing it in. The tool insert first forces the ball 32 backward until the ball can snap into the indentation provided.