Mitre Saw with Top Table

The present invention relates to saws, and in particular, to powered saws which can perform mitre cuts, chops cuts, sliding cuts or bevel cuts, or any type of powered saw which can perform any combination of these functions.

<patcit id="pcit0001" dnum="WO9818588A"><text>WO98/18588</text></patcit> discloses a sliding compound mitre saw. Such a saw can perform bevel cuts, mitre cuts, sliding cuts and chop cuts. The sliding compound mitre saw disclosed comprises a base 12 (using the same reference numbers as those used in <patcit id="pcit0002" dnum="WO9818588A"><text>WO98/18588</text></patcit>) having a rotatable table 14 mounted within it. The rotatable table 14, in conjunction with a fence 26 fixed to the base 12, enables the sliding compound mitre saw to perform mitre cuts. Connected to the rear of the table 14 is a bevel mount 16 which is able to pivot about a horizontal axis in relation to the table 14. The pivotal movement of the bevel mount 16 in relation to the table 14 enables the sliding compound mitre saw to perform bevel cuts. Slideably mounted onto the bevel mount 16 are two guide rods 34 which are capable of sliding horizontally, back wards and forwards. The rods 34 enable the sliding compound mitre saw to perform sliding cuts. Pivotally mounted on the end of the guide rods 34 is a motor unit 36, which comprises a motor 22 for rotationally driving a circular saw blade 18 mounted on a drive spindle on the motor unit 36. The pivotal movement of the motor unit 36 in relation to the guide rods 34 enable the saw to perform chop cuts.

Rigidly mounted to the motor unit 36 is a fixed guard 40 which surrounds the cutting edge of the top half of the cutting blade 18. Pivotally mounted to the motor unit is a pivotal guard 42 which can pivot between a first position where it surrounds the cutting edge of the lower half of the cutting blade and a retracted position where the cutting edge of the lower half of the blade 18 is exposed for use in cutting.

The pivotal guard is pivoted between its two positions using a mechanical linkage which comprises a series of mechanical arms 48, 50, which are pivotally connected to each other and the saw, and cams 52, 54 which control the movement of the arms 48, 50. As the motor unit is pivoted downwards, the mechanical linkage causes the lower cutting edge of the blade to become exposed due to the retraction of the pivotal guard by the mechanical linkage.

<patcit id="pcit0003" dnum="JP2005178281A"><text>JP2005-178281</text></patcit> describes a chop saw with a table mounted on top of the motor unit.

<patcit id="pcit0004" dnum="US5297463A"><text>US5297463</text></patcit> discloses a compound mitre saw having a adjustable work piece support fence.

Accordingly there is provided a saw comprising: <ul id="ul0001" list-style="none" compact="compact"><li>a base assembly (102, 104) connected to a mounting portion (110);</li><li>a motor unit (118) piotally connected to a motor support (208) which is mounted on the mounting portion (110) to allow the motor unit (118) to pivot towards or away from the base assembly (2, 4) to perform chop cuts, the motor unit (118) having an output drive spindle (289) upon which a circular saw blade (120) can be rigidly mounted to be rotationally driven by the motor unit (118);</li><li>at least one rearward pivotal guard (232) pivotally mounted on the motor unit (118) which can pivot from a first enclosed position, where it surrounds at least a portion of the lower edge of a saw blade (120) when mounted on the spindle (48), to a second retracted position where the portion of the lower edge of the saw blade (28) is exposed; and wherein there is further provided a pivotal guard actuating mechanism which moves the at least one rearward pivotal guard (232) from its first enclosed position to its second retracted position when the motor unit (38) is pivoted towards the base assembly (102, 104); characterised in that the motor support is mounted to two guide rods which are slideably mounted onto the mounting portion to enable the saw to perform sliding cuts.</li></ul>

A "forward pivotal guard", such as the second forward pivotal guard 220 and the fourth forward pivotal guard, is a blade guard which surrounds the front lower portion of the saw blade when the guard is in its enclosed position. Typically, a forward blade guard, when it moves from its retracted position, where the cutting edge of the cutting blade is exposed, to its enclosing position, where it surrounds the cutting edge of the cutting blade, it rotates, relative to the motor unit 118, in the same direction as the cutting blade when driven by the motor to perform a cutting action.

A "rearward pivotal guard", such as the third rearward pivotal guard 232, is a blade guard which surrounds the rear lower portion of the saw blade in its enclosed position. In the embodiment described herein, the rearward pivotal guard pivots in the same direction as a typical forward pivotal guard. However, the axis of pivot of the rearward pivotal guard is located rearward of the axis of rotation of the saw blade. However, it will be appreciated that such a rearward pivotal guard could pivot around the axis of rotation of the saw blade. In such a construction, when the rearward pivotal guard moves from its retracted position, where the cutting edge of the cutting blade is exposed, to its enclosing position, where it surrounds the cutting edge of the cutting blade, it typically rotates, relative to the motor unit 118, in the opposite direction to that of the cutting blade when driven by the motor to perform a cutting action.

Embodiments of the present invention will now be described with reference to the accompanying drawings of which: <ul id="ul0002" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> shows a computer generated drawing of the sliding compound mitre saw with a table from a first perspective;</li><li><figref idref="f0002">Figure 2</figref> shows a computer generated drawing of the sliding compound mitre saw with a table from a second perspective;</li><li><figref idref="f0003">Figure 3</figref> shows a computer generated picture of a side view of the saw showing an example of a guard actuation mechanism and the mechanical linkage which automatically moves the pivotal guards;</li><li><figref idref="f0004">Figure 4</figref> shows a side view of the saw with the blade at its maximum height;</li><li><figref idref="f0005">Figure 5</figref> shows a side view of the saw with the blade touching a work piece;</li><li><figref idref="f0006">Figure 6</figref> shows a side view of the saw with the blade cutting the work piece;</li><li><figref idref="f0007">Figure 7</figref> shows a sketch of the cam mechanism of the second embodiment of the guard actuation mechanism;</li><li><figref idref="f0007">Figure 8A to 8E</figref> show a design diagram of the inner half of the third rearward pivotal guard of an embodiment of guard actuation mechanism;</li><li><figref idref="f0008">Figure 9A to 9D</figref> show a design diagram of the outer half of the third rearward pivotal guard of an embodiment of guard actuation mechanism;</li><li><figref idref="f0009">Figure 10</figref> shows a computer generated picture of the saw (with the first example of the guard actuating mechanism) with an example of the table height adjustment mechanism;</li><li><figref idref="f0010">Figure 11</figref> shows computer generated picture of a top view of the saw showing the height adjustment mechanism (with the table 114 being shown as transparent);</li><li><figref idref="f0011">Figure 12A and 12B</figref> are engineering drawings of the tubular support;</li><li><figref idref="f0011">Figure 13</figref> shows a sketch of the locking mechanism for the second example of the height adjustment mechanism;</li><li><figref idref="f0012">Figure 14</figref> shows a sketch of the table with slots formed through it to enable an operator to see "through" the table to increase visibility of the of the saw below the table114;</li><li><figref idref="f0012">Figures 15A and 15B</figref> show the second forward pivotal guard 220 of the embodiment of guard actuation mechanism;</li><li><figref idref="f0013">Figures 16A to 16E</figref> show the fourth forward pivotal guard of the embodiment of guard actuation mechanism;</li><li><figref idref="f0014">Figure 17</figref> shows a first computer generated picture of the saw from a perspective view with aspects of the saw "cut away" to expose the embodiment of guard actuation mechanism;</li><li><figref idref="f0015">Figure 18</figref> shows a second computer generated picture of the saw from a perspective view with aspects of the saw "cut away" to expose the embodiment of guard actuation mechanism;</li><li><figref idref="f0016">Figure 19</figref> shows a third computer generated picture of the saw from a perspective view with aspects of the saw "cut away" to expose the embodiment of guard actuation mechanism;</li><li><figref idref="f0017">Figure 20</figref> shows a fourth computer generated picture of the saw from a perspective view with aspects of the saw "cut away" to expose the embodiment of guard actuation mechanism;</li><li><figref idref="f0018">Figure 21</figref> shows a fifth computer generated picture of the saw from a perspective view with aspects of the saw "cut away" to expose the embodiment of guard actuation mechanism;</li><li><figref idref="f0019">Figure 22</figref> shows a sketch of the front view of the fence 108;</li><li><figref idref="f0020">Figure 23</figref> which shows a top view of the moveable fence with the upper half 620 removed;</li><li><figref idref="f0020">Figure 24</figref> shows a sketch of the rear of the top section of the moveable part of the fence; and</li><li><figref idref="f0021 f0022 f0023 f0024 f0025 f0026 f0027">Figures 25 to 41</figref> show further views of the fences as shown in <figref idref="f0019 f0020">Figures 22 to 24</figref>.</li></ul>

The invention described herein relates to a sliding compound mitre saw, similar to that described in <patcit id="pcit0005" dnum="WO9818588A"><text>WO98/18588</text></patcit>, which has a table mounted on top of the motor unit to enable the saw to act as a table saw.

Referring to <figref idref="f0001">Figures 1</figref> and <figref idref="f0002">2</figref>, there is provided a sliding compound mitre saw with a table 114 which can perform cuts, mitre cuts, sliding cuts and chop cuts. The sliding compound mitre saw disclosed comprises a base having a rotatable table 104 mounted within it. An extension arm 106 is attached to the periphery of the rotatable table 104 and extends forward in well known manner. The rotatable table 104, in conjunction with a fence 108 fixed to the base 102, enables the sliding compound mitre saw to perform mitre cuts. Connected to the rear of the rotable table 104 is a bevel mount 110 which is able to pivot about a horizontal axis in relation to the rotatable table 104. The pivotal movement of the bevel mount 110 in relation to the rotatable table 14 enables the sliding compound mitre saw to perform bevel cuts. Slideably mounted onto the bevel mount 110 are two guide rods 112, 116 which are capable of sliding horizontally, back wards and forwards. The rods 112, 116 enable the sliding compound mitre saw to perform sliding cuts. Pivotally mounted on the end of the guide rods 112, 116 is a motor unit 118, which comprises a motor (not shown) for rotationally driving a circular saw blade 120 mounted on a drive spindle on the motor unit 118. The pivotal movement of the motor unit 118 in relation to the guide rods 112, 116 enable the saw to perform chop cuts. The motor unit 118 is biased to an upward position by a spring (not shown). A slot 122 extends across the rotatable table 104 and along the extension arm 106.

Mounted on the top of the saw is a table 114 which enables the sliding compound mitre saw to be also used as a table saw. The table 114 is attached to the top side of the motor unit 118. A slot 124 is formed through the table 114 through which the top section of the circular saw blade 120 projects. The motor unit 118 can be locked in a downward position such that the table 114 is horizontal. A work piece such as a piece of wood can then be slid across the top of the table 114 to engage with the top section of the saw blade 120 thus enabling the sliding compound mitre saw to be used as a saw table. A riving knife 126 is located towards the rear of the saw blade 120 and a guard 128 can surround the top of the saw blade 120 when the saw is not being used as a table saw, which includes a shoot 130 for the extraction of wood chips.

The saw comprises a plurality of guards located below the table 114 which are capable of enclosing the lower section of the saw blade for safety purposes when the saw is not being used as a the sliding compound mitre saw for performing chop, mitre, bevel or sliding cuts, for example when the saw is being used as a table saw, with the motor unit 118 locked downwardly.

<figref idref="f0003 f0004 f0005 f0006">Figures 3 to 6</figref> shows a sliding compound mitre saw with a table and with a first example of a guard actuation mechanism.

Referring to <figref idref="f0003 f0004 f0005 f0006">Figures 3 to 6</figref>, a handle 132 is attached to the motor unit 118 by which a user can grip and pivot the motor unit 118 and the circular saw blade 120 downwards towards the rotatable table 104. An electric switch 134 is mounted on the handle 132 for activating the motor.

The motor unit 118 can be locked in its lowest pivotal position (<figref idref="f0003">Figure 3</figref>) against the biasing force of the spring. When the motor unit 118 is in this position, the table 114 is horizontal. In this position the table 114 can be used as a table saw, the work piece 216 being cut by the part of the saw blade 120 which passes through the slot 124.

When the motor unit 118 is free to pivot, the saw can be used as a sliding compound mitre saw in the normal manner.

The height of the table 114, and hence the amount of saw blade 120 passing through it, can be adjusted vertically. This is described in more detail further below.

The lower part of the circular saw blade 120 below the table 114 is surrounded by a guard actuation assembly. A first embodiment of such a guard actuation assembly which will now be described in more detail.

Attached to the motor unit 118 is a first fixed guard 218 which surrounds top and middle sections of the circular saw blade 120. A "fixed guard", such as the first fixed guard, is a blade guard which remains stationary relative to the motor unit 118.

Pivotally attached to the first fixed guard 218 is a second forward pivotal guard 220. The second forward pivotal guard 220 pivots about the axis 222 of the circular saw blade 120. A spring (not shown) biases the second forward pivotal guard 220 downward (clockwise) as shown in <figref idref="f0003">figure 3</figref>. A roller 224 is mounted on the base of the guard 220. The roller 224 engages either the rotary table 104 or extension 106 or a work piece 216 mounted on the support table 104 or extension 106.

A bar 226 is pivotally attached at one end to a motor support 208 attached to the end of the guide rails 112, 116. An elongate slot 228 is formed along a section of the length of the bar 226 at the other end. A pin 230, rigidly attached to the second forward pivotal guard 220 passes through the slot 228 and which is capable of sliding along the slot 228. The biasing spring acting on the second forward pivotal guard 220 causes the guard to pivot until the pin 230 is at the inner end position of the slot where it remains held by the force of the spring. The pin 230 located within the slot 28 of the bar 26 controls the pivotal movement of the second guard 220 on the housing as it pivots upwards and downwards. When the housing 10 is in its upper most pivotal position (<figref idref="f0004">Figure 4</figref>), the second forward pivotal guard 220 surrounds the lower front section of circular saw blade 120. As the motor unit 118 is pivoted downwardly, the bar 226 pushes the pin 230, causing the second forward pivotal guard 220 to telescopically pivot into the first fixed guard 218. The slot 228 allows the guard 220 to pivot freely, against the biasing force of the spring if it encounters a work piece 216 located on the support table 104.

A third rearward pivotal guard 232 is pivotally mounted about a point 234 on the rear of the first fixed guard 218.

A spring (not shown) biases the third rearward pivotal guard 232 backwards (clockwise) as shown in <figref idref="f0003">figure 3</figref>. A slot (not visible) is formed centrally along the length of the guard 232. When the motor unit 118 is pivoted to its uppermost position (<figref idref="f0004">Figure 4</figref>), the third rearward pivotal guard 232 pivots to a maximum rearward (clockwise) position where it surrounds the rear of the circular saw blade 120. When the motor unit 118 is pivoted downwardly, the front tip 236 of the third rearward pivotal guard 232 engages with either the support table 104 or a work piece 216 on the support table 104. Once the front tip 236 is engaged, pivotal downward movement causes the front tip 236 to slide forward, rotating the third rearward pivotal guard 232 about its axis 234 anti-clockwise, the edge of the cutting blade 120 passing through the slot in the third rearward pivotal guard 232 and allowing it to contact a work piece 16 to cut.

When the housing is raised to its upper pivot point (<figref idref="f0004">Figure 4</figref>), the front tip 236 of the third rearward pivotal guard 232 and the rear lower end of the second forward pivotal guard 220 meet so that the whole of the lower section of the cutting blade 120 is surrounded. This, in combination with the fixed guard 218, ensures the whole of the blade 120 surrounded when the motor unit 118 is in the upper position.

When the motor unit 118 is pivoted downwardly, the second forward pivotal guard 220 is moved anti-clockwise as shown in <figref idref="f0005">Figure 5</figref>, against the biasing force of the spring, by the pin 230 located in the inner end position of the elongate slot 228 of the bar 226. The second forward pivotal guard 220 pivots, as the motor unit 118 is pivotally lowered, under the control of the bar 226, until the roller 224 engages the work piece 116 (see <figref idref="f0006">Figure 6</figref>). As the motor unit 118 continues to pivot downwardly, the roller 224 rolls over the top surface of the work piece 216, causing the second forward pivotal guard 220 to pivot at a different rate which would otherwise be caused by the bar 226, resulting in the pin 230 sliding along the elongate slot 228 towards the end located remotely from the bar's pivot point. Thus the front lower section of the saw blade 120 becomes exposed to allow it to cut the work piece 216.

Similarly, the third rearward pivotal guard 232 pivots once the tip 236 has engaged, allowing the edge of the blade 120 to pass through the third rearward pivotal guard 232, thus exposing the rear lower section of the blade 120 to cut the work piece 216 (see <figref idref="f0006">Figure 6</figref>).

An embodiment of a guard assembly according to the present invention will now be described in more detail. Where the same features are present in the embodiment which are present in the first example, the same reference numbers have been used. The embodiment is the same as the first example except for: <ul id="ul0003" list-style="none" compact="compact"><li>the mechanism which moves the third rearward pivotal guard 232 is different; and</li><li>there is an additional fourth forward pivotal guard 320.</li></ul>

The second forward pivotal guard 220 is moved as described previously for the first embodiment. The second forward pivotal guard is moved using the bar 226 via the pin 230 located within the slot 228. However, unlike the first embodiment, there is now an additional fourth forward pivotal guard 320 pivotally mounted about the aperture 324, the wall of which surrounds the drive spindle of the motor unit 118, and into which the second forward pivotal guard can telescope, and which in turn can telescope into the fixed guard 218. The guard 320 can freely pivot into and out of, in a telescopic manner, the first fixed guard 218 (see <figref idref="f0014 f0015 f0016 f0017 f0018">Figure 17 to 21</figref>). <figref idref="f0013">Figure 16A to 16E</figref> show design drawings of the fourth forward pivotal guard 320. The fourth forward pivotal guard 320 is prevented from completely pivoting out of the fixed guard 218 by a catch formed on the fourth forward pivotal guard 320.

A slot 322 is formed through the side of the fourth forward pivotal guard 320 . <figref idref="f0012">Figure 15A and 15B</figref> show the second forward pivotal guard 220. A screw attaches at point 326 on the second forward pivotal guard 220, the body of which passes through the slot 322. As the second forward pivotal guard pivots, due to the pivoting movement of the motor unit 118 which causes the second forward pivotal guard to pivot due to the bar 226, the screw at point 326, which initially is located at the lowest point within the slot 322, slides along the slot 322 of the fourth forward pivotal guard 320 until it reaches the top end of the slot 322. At which point, the pivotal movement of the second forward pivotal guard 220, which is now located within the fourth forward pivotal guard 320 in a telescopic fashion, causes pivotal movement of the fourth forward pivotal guard 320. The two guards 220, 320 pivotally move in unison inside the fixed guard 218 until the two guards located inside of the fixed guard.

The roller 224 mounts on the peg 328 of the guard 220 as shown in <figref idref="f0012">Figure 15A</figref>.

In the first example, the third rearward pivotal guard 232 moved when it engaged with a work piece, as the housing is pivoted downwardly. However, it has been found that this restricts the visibility of the operator during the use of such a design. It is therefore proposed to move the third rearward pivotal guard using a cam system.

<figref idref="f0007">Figures 8A to 8E</figref> show the inner half of the third rearward pivotal guard of the second embodiment; <figref idref="f0008">Figures 9A to 9D</figref> show the outer half of the third rearward pivotal guard of the second embodiment. The two are clamped together to form the guard 232 as shown in <figref idref="f0014 f0015 f0016 f0017 f0018">Figure 17 to 21</figref>.

Formed on the bar 226, which is used to pivot the second forward pivotal guard 220, is a cam 300 (see <figref idref="f0007">Figures 7</figref>, <figref idref="f0014 f0015 f0016 f0017 f0018">17 to 21</figref>). A cam follower 302, in the form of a roller bearing, is mounted on the third rearward pivotal guard 232 at point 350 and which engages with the cam 300. A stop 304 is formed next to the cam 300 creating a slot 306 between them in which the cam follower 302 sits when the motor unit 118 is in its upper most position. The shape of the slot 306 is such that, when the housing is in its raised position, the cam follower 302 is prevented from moving, thus locking the third rearward pivotal guard 232 against any pivotal movement.

As the motor unit 118 is pivoted downwardly causing the bar 226 to move, the cam follower 302 rides out of the slot 306 and over the cam 300 in a direction shown by the arrows in <figref idref="f0007">Figure 7</figref>. When the motor unit 118 is in its lowest position, the cam follower 302 is in the position indicated by the dashed lines in <figref idref="f0007">Figure 7</figref>. The shape of the cam 300 is such to cause the third rearward pivotal guard 232 to initially rise to expose the edge of the blade (to aid visibility) and then fall to engage with the work piece as in the embodiment.

When the motor unit 118 rises, the cam 302, retraces its path over the cam 300 on bar 226, closing the third rearward pivotal guard 232. The end of the drive spindle of the motor unit 118 is shown as reference number 289 in <figref idref="f0014 f0015 f0016 f0017 f0018">Figure 17 to 21</figref>.

Height adjustment mechanism

The first example of height adjustment mechanism will now be described with reference to <figref idref="f0009">Figures 10</figref>, <figref idref="f0010">11</figref> and <figref idref="f0011">12</figref>.

The table 114 is moveably mounted on the motor unit 118 using a tubular support 440. The tubular support 440 allows the table 114 to slide up and down on the motor unit 118.

Referring to <figref idref="f0009">Figure 10</figref>, attached to the edge of the table 114 is a tubular support 440. The longitudinal axis of the support 440 is vertical. The shape of the cross section of tube 40 is rectangular as best seen in <figref idref="f0011">Figures12A and 12B</figref>. Two vertical slots 442 (only one is visible in <figref idref="f0009">Figure 10</figref>) are formed on opposite sides of the tubular support 440 in a corresponding manner. A threaded hole is formed in the metal casting which forms the housing 410 of the motor unit 118. A bolt passes through the two slots 442, passing through the width of the tubular support 400 and is threadedly engaged in the hole in the casting of the housing 410. The head of the bolt was sufficiently large to prevent it passing through the slots 442.

When the bolt is screwed into the threaded hole, it sandwiches the tubular support 440 against the casting 9as the head of the bolt can not pass through the slots 442) and prevents it being able to slide in a vertical manner. In order to raise the height of the table 114 above the housing 410, the bolt is unscrewed slightly, so that the tubular support 440 can slide vertically, the sliding movement of the bolt along the elongate slot 442 controlling the movement of the tubular support 440. The height is then adjusted and then the bolt tightened to hold the tubular support 440, and hence table 114, stationary.

A second example of the height adjustment mechanism is now described with reference to <figref idref="f0011">Figure 13</figref>. Where the same features are present in the second embodiment which were present in the first, the same reference numbers have been used.

The design remains substantially the same. However, the bolt has been replaced by a threaded bar 400 which screws into the metal cast of the housing 410 and a locking knob assembly (described below) which screws onto the threaded bar 400 to sandwich the tubular support 440 against the cast of the housing 410. The purpose is to prevent the vertical tubular support 440 from unnecessary movement during height adjustment.

Enclosed you will find at <figref idref="f0011">Figure 13</figref> a sketch of a horizontal cross section of the threaded bar 400 and support 440.

The assembly comprises a self-locking nut 402 (with nylon insert) being screwed onto the threaded bar 100 which is screwed into the metal cast 410. The threaded bar 100 passes through vertical slots 442 in the vertical tubular support 440. The nut 402 is screwed onto the bar 400 sandwiching a washer 404 between the nut 402 and the vertical support 440. The nut 402 is tightened to apply a predetermined compression force onto the vertical support 440. This allows the support 440 limited movement. A cup shaped washer 406 surrounds, but does not engage with the nut 402 which abuts against the washer 404. A knob 408 is then screwed onto the threaded shaft 400 to sandwich the cup shaped washer 406 against the washer 404. Tightening of the knob 408 results in the vertical support 440 being against the side of the cast 410 to fix its position. The slackening of the knob 408 releases the support 440 and allows it to slide. However, the self-locking nut 402 prevents excessive movement of the support 440.

Slots in table for visibility

Referring to <figref idref="f0012">Figure 14</figref> , it is being proposed to add a plurality of slots 502 in the table 114. The slots 502 enable the user to see through the table 114. The purpose of the slots is to assist the user when they are using the saw as a sliding compound mitre saw. When being used in this manner, the table 11 blocks the vision of the operator who is trying to cut a work piece below the table 114 on the rotatable table 102 or extension 106 below. The slots 502 allow the operator to see "through" the table 114.

Fence Construction

Referring to <figref idref="f0001">Figure 1</figref>, the saw comprises a fence108. The fence comprises two halves, a fixed fence 600 on the right as viewed in <figref idref="f0019">Figure 22</figref> and a moveable fence 602 on the left as shown in <figref idref="f0012">Figure 15</figref>. <patcit id="pcit0006" dnum="US5297463A"><text>US 5297463</text></patcit> discloses a moveable fence and forms relevant prior art.

The fence comprises a base section 604 which spans the full width of the saw. The base section 604 comprises a straight right section 606, which forms the fixed fence 600 and a straight left section 608 which forms the lower half of the moveable fence 602. The two sections 606, 608 are connected to each other by a curved portion 610 (see <figref idref="f0014">Figures 17</figref>). The two sections 606, 608 and curved portion 610 are made as a one piece construction and manufactured from cast steel or aluminium. Such a construction is well known in the art. The base section 602 is rigidly connected to the base 102 of the saw and transverses the rotatable table 104 in well known manner.

Referring to the fixed fence 600, the straight right section 606 is rigidly fixed to the base 102 and crosses slightly less than half of the right hand side of the rotatable table 104. The edge 612 of the fixed fence adjacent the curved portion 610 is vertical. The location of the vertical edge 612 is located such that it does not interfere with the blade 120 and blade guards when motor unit 118 is lowered vertically downwardly. A bulge 614 is added to the base of the vertical edge 612 which projects towards the moveable fence 602. The bulge 614 is the present embodiment is triangular. The bulge 614 moves the fence 600 closer to where the blade 120 cuts a work piece. By doing this, it provides support to the rear of a work piece closer to the area where blade 120 cuts through it. However, the remaining vertical edge 612 of the fixed fence 600 is kept at a greater distance from the blade 120 so that it does not interfere with it or the guards.

Referring to the moveable fence, it comprises two halves, a lower half formed by the straight left straight section 608 of the base section 604 and an upper slideable half 620. The upper half 620 can slide in the direction indicated by Arrows A. As with the straight right section 606, the straight left section 608 is rigidly fixed to the base 102 and crosses slightly less than half of the left hand side of the rotatable table 104. Formed in the top of the straight left section along its length is a elongate slot (see <figref idref="f0020">Figure 23</figref> which shows a top view of the moveable fence with the upper half 620 removed.) A threaded bolt 622 passes through a threaded hole 624 formed in the side of the straight left section 608 from the rear side 626 of the straight left section 608 into the slot 626. The base 628 of the upper slideable half 620 is such that it fits into and is capable of sliding along the slot 626. <figref idref="f0020">Figure 24</figref> shows a sketch of the rear of the top section 620 of the moveable fence. Formed in the base 628 of the upper slideable half 620 along the length of the upper half 620 is a groove 630. The groove 630 has a first depth D1 long the majority 632 of its length. The groove 630 has a second depth D2 along the rest 634 of the groove 630. The second depth D2 is less than the first depth D1. When the base 628 of the upper half 620 is located within the groove 630, the groove 630 faces towards the exit 636 of the threaded hole 624 within the slot 626. The bolt 622 is screwed through the hole 624 until its end 638 passes into the slot 626 and then into the groove 630 of the upper half 620.

Whilst the end 638 of the bolt 622 remains in the groove 630, it is prevents the upper half 620 from being separated from the lower half 608 of the moveable fence. Screwing the bolt 622 into the groove 630 until it hits the base of the groove 630, locks the upper half 620 to the lower half 608.

During normal operation, the end 638 of the bolt 622 is located in the majority 632 of the groove. The bolt is prevented from entering the rest 634 by ensuring the end 638 of the bolt 622 is screwed sufficiently far enough into the groove 630 so that it is unable to travel into the rest 634 of the groove 630 as the rest 634 of the groove is too shallow to accommodate the amount of length of the bolt 622 extending into the groove 630. With the end 638 of the bolt 622 located at this first depth, the movement of the upper half 620 of the sliding fence 602 is restricted by movement of the bolt within the majority 632 of the groove 630 only (the "first range of movement"). If the bolt is then unscrewed slightly, to withdraw the end 638 of the bolt 622 from the groove 630 sufficiently to allow it to travel in the rest 634 of the groove 630, the bolt 622 can then slide the full length of the slot 630, allowing the upper half 620 to slide a greater distance (the "second range of distance").

When the bolt 622 is set so that the upper half 620 can travel the first range of movement, the upper half 620 can move towards or away from the cutting blade of the saw. However, the minimum distance between the end 640 of the upper half 620 of the moveable fence 602 and the blade is that same as that for the end 642 of straight left section 608. However, when the bolt 622 is set so that the upper half 620 can travel the second range of movement, the upper half 620 can again move towards or away from the cutting blade of the saw. However, the minimum distance between the end 640 of the upper half 620 of the moveable fence 602 and the blade is now less than that for the end 642 of straight left section 608.

This allows the upper half 620 of a miter saw to have a bypass mode where it goes closer to the blade for precision cuts.

The advantage of this design of moveable fence is that it allows for a normal type of sliding fence stop for most cutting, while allowing a bypass position which allows the fence to be adjusted closer to the blade when more support is needed. The "stop" between the two regions of travel prevents the user from inadvertently sliding the fence too close to the blade in normal use.

<figref idref="f0021 f0022 f0023 f0024 f0025 f0026 f0027">Figures 25 to 41</figref> show further views of the fences as described above with reference to <figref idref="f0019 f0020">Figures 22 to 24</figref>.