GB2308330A - Saw guard arrangement - Google Patents

Abstract

A saw 1 comprises a frame 3, a table 5 mounted in the frame 3 and adapted to adopt two positions, a saw assembly 17 pivoted with respect to the table whose blade 19 protrudes through a slot 21 in the table, in a first of said two positions of the table 5 the saw assembly 17 being above the table, the saw 1 thereby forming a chop saw, and, in a second of said two positions of the table, the saw assembly 17 being below the table 5 and the saw 1 thereby forming a bench saw, the saw 1 further comprising a guard 27 which, when the table 5 is in the second of the two positions, protects a user from the blade 19 protruding through the slot 21, the guard 27 being supported by a linkage which, if a force greater than a predetermined force is applied to the guard 27, releases the guard 27 to prevent damage to the linkage or the guard 27. Such linkage may comprise a spring 79 loaded latch pin 81 holding the guard 27 in its operating position by engaging in a recess 87. This mechanism is located at the pivot joint 59.

Description

CHOP/TABLE SAW ARRANGFMFNT This invention relates to circular saws of the type comprising a table, a pivot member on the table and a saw assembly pivoted about a pivot axis with respect to the pivot member, whereby said saw assembly carrying a motor driven blade can be plunged into a workpiece supported on the table.

Such saws are known and described in published patent documents such as EP-0133666 and EP-0450400. These saws are useful and have numerous possibilities for enhancement to improve the capacity, capability and efficiency not to mention cleanliness and safety of their arrangements. On the other hand, all these features add complexity and cost, and may render the saw user unfriendly.

The present invention is particularly applicable to saws of the type described above but which in addition have the table mounted in a frame such that the table may be inverted, as by pivoting about an axis, so that the saw assembly is then beneath the table. The table is in addition provided with a slot so that the blade can protrude through the slot to render the saw a bench or table saw. Such saws are known and described in DE- 1628992, EP-0502350 and EP-0586172.

Both EP-0133666 and EP-0450400 mentioned above describe saws in which the saw assembly comprises an upper guard and a lower guard for the blade. The upper guard is formed from the housing of the assembly and permanently covers a top part of the blade.

A bottom part of the blade is covered by the lower guard but this must be withdrawn in use so that the blade is exposed when required to perform cutting operations.

A handle is disposed on the upper guard by means of which a user can pivot the saw assembly up and down to perform cutting operations on a workpiece supported on the table. Further, if the table has a rotational portion carrying the saw assembly, mitre cuts can also be made in a workpiece on the table.

The lower guard may be opened entirely by an actuating lever disposed on the handle. Altematively the guard may be opened automatically by pivoting of the saw assembly, there being provided a connection between the guard and the pivot member for this purpose. A further alternative is that the guard may be opened partly by either of these arrangements and only further opened by direct contact with a workp iece.

Means must be provided to bias the saw assembly to a raised upright position when it is at rest so that the user is not required to lift the not-insignificant weight of the saw assembly after completing a plunge cut. Such means is normally in the form of a powerful spring.

Although the upper and lower guards mentioned above provide satisfactory protection for the saw blade when the saw assembly is acting as a plunge or mitre saw, when the table is flipped-over to convert the saw into a bench saw the saw blade is once again exposed.

In this configuration, a separate guard must be provided which, in the past, has been mounted on a riving knife of the bench saw each time the saw is used as a bench saw. This is clearly not satisfactory, not least because many users may simply not bother to attach the guard to the riving knife and will proceed to use the bench saw without any guard in place. Further, if the guard is simply mounted on the riving knife, the guard may obstruct motion of a workpiece past the blade and riving knife during use. Furthermore, the guard may simply pivot about a pivot axis on the riving knife rather than being held in a constant orientation relative to the table surface during lifting.

ln view of the foregoing, the present invention aims to improve upon the prior art saws known to the applicant by providing a chop/table saw including an improved guard arrangement when the saw is being used as a table saw.

According to the present invention there is provided a saw comprising a frame, a table mounted in the frame and adapted to adopt two positions, a pivot member on a first side of the table, a saw assembly pivoted with respect to the pivot member, a blade journalled in said assembly, a motor to drive the blade, and a slot in the table through which said blade is adapted to protrude, in a first of said two positions of the table the saw assembly being above the table, the saw thereby forming a chop saw for performing plunge cuts on workpieces supported on said first side of the table, and, in a second of said two positions of the table, the saw assembly being below the table and the saw thereby forming a bench saw for performing cuts on workpieces passed through the blade on a second opposite side of the table, the saw further comprising a guard which, when the table is in the second of the two positions, protects a user from the blade protruding through the slot, the guard being supported via a linkage which, if a force greater than a predetermined force is applied to the guard, releases the guard to prevent damage to the linkage or the guard.

Preferably the linkage includes a pivot joint which opposes pivotal motion with the predetermined force. Other types of releasable joint may, however, alternatively be used.

The linkage is preferably held in a first position by a spring which exerts the predetermined force. Hence, if a force greater than the predetermined force is applied, the spring is either extended or contracted (depending upon whether the spring is in tension or compression, to release the linkage and thereby prevent damage to the guard or the linkage.

In a preferred embodiment, the spring urges a pin mounted on a first portion of the linkage into a recess formed in a second portion of the linkage, the pin being released from the recess when a force greater than the predetermined force is applied to the guard.

Further, in a preferred embodiment, the spring is mounted in tension b3etween the pin and an end cap, the pin and end cap abutting opposite faces of the second portion of the linkage.

The first portion of the linkage may comprise a tube which carries the pin and has a notch at its free end for receiving a nib of the end cap to prevent rotation of the end cap relative to the tube during use.

Further, a spring holder is preferably provided within the tube threadedly mounted on the end cap such that, when the nib of the end cap is withdrawn from the notch of the tube, the tension in the spring can be adjusted by rotating the end cap relative to the spring holder.

The recess in the second portion of the linkage preferably provides a ramp up which the pin can travel when a force greater than the predetermined force is applied to the guard. Conversely, when the guard is to be snapped back into its operating position, the pin can simply run down the ramp of the recess.

The linkage preferably includes a U-shaped support mounted on the table, the axis of the U extending substantially parallel to the plane of the table to accommodate workpieces passing over the table. If such an arrangement is used, the U-shaped support may be tubular and act as the first portion of the linkage.

The U-shaped support may be retracted for packing or storage. With this in mind, the prong of the U-shaped support not carrying the guard engages a clamp mounted on the table itself. As a result, if the clamp is released, the prong of the support can pass through the clamp to allow either complete removal of the support from the table or complete entry of the prong of the support through the clamp.

Preferably a quadrilateral linkage between the guard and the U-shaped support ensures that as the guard rises, the guard remains at substantially the same orientation relative to the table. In this way, a user of the saw is protected against the blade for all active positions of the guard.

The quadrilateral linkage may be locked to hold the guard in a desired position relative to the table. With this in mind, if the guard is being used as a dust collector when the saw is being used as a chop saw, it is desirable for the guard to be held firmly against the underside of the table. By locking the quadrilateral linkage, this can be achieved prior to flipping-over of the table.

The quadrilateral linkage may comprise a pair of cables extending along an arm, each cable having a first end attached to a roller at one end of the arm and a second end solidly mounted at the other end of the arm such that, as the guard is raised, the roller rotates to retain the guard in the desired position. If this arrangement is used, the quadrilateral linkage is preferably locked by means of a device which squeezes the arm to grip the roller, thereby preventing rotation of the roller.

A specific embodiment of the present invention is now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a saw assembly according to the present invention with the table in chop saw mode; Figure 2 is a schematic side view of the saw of Figure 1, but this time with the table in bench saw mode; Figure 2A is a plan view of the arm of the quadrilateral linkage shown in the saw of Figure 2; Figure 3 is a schematic front view of the saw shown in Figure 2 with the table in bench saw mode; and Figure 4 is an enlarged front view of a portion of the guard support linkage shown in the previous Figures.

With reference to the drawings, a chop/bench (or table) saw 1 according to the present invention comprises a frame 3 supporting a table 5. The table 5 is connected to the frame 3 through an intermediate member 7 which is pivoted to the frame 3. The table has a first wheel 9 fixed thereto and a belt 11 passes around the first wheel 9 and around a second wheel 13 fixed to the frame 3 around the pivot 14 ofthe intermediate member 7. Pivoting of the intermediate member 7 relative to the frame 3 rolls the first wheel 9 inside the belt 11 and rotates the table 5 between the chop saw mode (Figure 1) and the bench saw mode (Figure 2). This mode of operation is described in detail in EP-05861 72.

With specific reference to Figure 1, when the saw 1 is in the chop saw mode, a pivot member 15 is positioned on the upper side of the table 5. A saw assembly 17 incorporating a saw blade 19 is pivotally mounted on the pivot member 15 for plunging through a slot 21 (cf. Figure 3) in the table 5 to snip-off pieces of a workpiece positioned on the table 5. As can be seen in Figure 1, an upper guard 23 and a lower guard 25 (which is withdrawn during use of the chop saw) are provided to protect the user of the saw from the spinning blade 19.

A spring, not shown, is also provided for urging the saw assembly 17 into its raised position so that a user of the saw does not have to hold the saw assembly 17 away from a workpiece when not cutting.

A guard/dust collector 27 can be seen below the table 5 in Figure 1 and above the table 5 in Figure 2 of the drawings. As will be appreciated, when the saw 1 is being used in chop saw mode, the guard/dust collector 27 is positioned below the table 5 so that debris and dust produced from a workpiece during cutting falls through the slot 21 in the table 5 and into the dust collector 27. An exit 29 from the dust collector 27 may be attached to a suction device (not shown) for removing dust from the saw 1.

The dust collector 27 is held firmly against the underside of the table 5 by means of a quadrilateral linkage 31 and a support 33 which will now be described in detail.

As can be seen from Figure 2 of the drawings, the dust collector/guard 27, quadrilateral linkage 31 and support 33 are all carried by the table 5 when the table 5 is rotated from its chop saw position of Figure 1 to its bench saw position shown in Figure 2. As a result, it is unnecessary for a user of the saw 1 to remove or replace the dust collector/guard 27 when the saw 1 is being changed from one arrangement to the other.

With reference to Figure 2, when the dust collector/guard 27 is positioned above the table 5, the exit 29 can once again be used to remove dust and debris from the vicinity of the saw blade 19, if desired.

Further, as a workpiece (not shown) is moved along the table 5 adjacent the fence 35 mounted on the table 5, the workpiece may abut a nose portion 37 ofthe guard 27. When this occurs, due to the angle ofthe nose portion 37 as shown in Figure 2, the guard 27 will be urged upwards away from the table 5 to allow the workpiece to move below the guard 27 into contact with the saw blade 19. The quadrilateral linkage 31 ensures that the guard 27 is held in a substantially constant orientation relative to the table 5 so that the guard 27 is at its most effective throughout motion of the guard 27. More particularly, the quadrilateral linkage 31 comprises an arm 39 mounted about a pivot axis 41 and carrying a roller 43 fixed to the guard 27. A pair of cables 45 each have a first end fixed to the roller 43 by means of a bolt or screw 44 which pinches the ends of the cables 45 and a second end fixed to adjustable stops 47 solidly mounted on a bracket 49 attached to the support 33. Hence, if the guard 27 is raised by a workpiece, for example, the cables 45 ofthe quadrilateral linkage 31 force the roller 43 to rotate anti-clockwise (when viewed in Figure 2), thereby forcing the nose portion 37 of the guard 27 towards the table 5. This results in the guard 27 being held in a substantially constant orientation relative to the table 5, the guard 27 simply being raised.

By virtue of the stops 47 being adjustable, it is possible to set the orientation of the guard 27 during installation, simply by lengthening or shortening the cables 45 as necessary. More particularly, if the upper stop 47 is adjusted to shorten the length of the upper cable 45 whilst the lower stop 47 releases the lower cable 45, the roller 43 will rotate clockwise thereby raising the nose portion 37 of the guard 27.

As can be seen from Figure 3 ofthe drawings, the support 33 comprises a U-shaped support 33 extending outwardly from the bracket 49 in a direction substantially parallel to the plane of the table 5. The return prong of the U-shaped support 33 engages with a clamp 51 mounted below the table 5 in Figure 2. The clamp 51 includes a cradle 53, a bearing portion 55 and means 57 for tightening the bearing portion 55 against the support 33. Thus, the position of the U-shape support 33 relative to the table 5 can be adjusted, thereby allowing the support 33 to be extended fully, removed from the table altogether or withdrawn fully (as shown in phantom lines in Figure 3) to enable the saw 1 to be packed or stored, for example.

As can be seen in Figure 2A, the arm 39 of the quadrilateral linkage 31 comprises two halves 39a, 39b. The roller 43 (not shown in Figure 2A) is mounted between the two halves 39a, 39b of the arm 39.

The two arms 39a, 39b are held together by means of screws 61 towards the support end of the arm 39. As a result, the end of the arm 39 carrying the roller 43 is slightly resilient, the two halves 39a, 39b being free to flex slightly, thereby allowing the roller 43 to rotate if necessary.

A device 63 for squeezing the two halves 39a, 39b of the arm 39 together adjacent the roller 43 is, however, provided to lock the quadrilateral linkage 31. In this regard, the device 63 comprises a shaft or pin 65 straddling the two halves 39a, 39b of the arm 39. One end of the shaft 65 carries a stop 67 in the form of a nut, for example, whilst the other end of the shaft 65 carries an eccentric head 69 pivotally attached to the shaft 65. The eccentric head 69 may be rotated about the pivot on the shaft 65 by means of a handle 71. If the handle 71 is activated, the eccentric head will force one half 39a of the arm 39 into contact with the other half 39b of the arm 39, thereby gripping the roller 43 held by the arm 39. When this occurs, the roller 43 is prevented from rotating, thereby locking the quadrilateral linkage 31.

As will be appreciated, if the guard 27 is to be held above the table 5 a particular amount, for whatever reason, it is simply necessary to raise the guard 27 and to activate the handle 71 of the locking device 63. The guard 27 will then be held in position above the table 5. Further, when the table 5 is to be flipped over from its bench mode to its chop saw mode, the dust collector/guard 27 needs to be held firmly against the table 5 and this can be achieved by lowering the guard 27 into contact with the table 5 and locking the locking device 63 using the handle 71. Thus, when the table 5 is inverted using intermediate member 7, the dust collector/guard 27 is in position below the table 5 for collection of dust or other debris from the slot 21 during chopping of workpieces on the table 5.

With reference to Figure 4 of the drawings, an automatic release joint 59 is shown. This joint 59 is situated between the bracket 49 and the U-shaped support 33. The bracket 49 extends between the two halves 39a,39b of the arm 39 and is retained therein by means of a nut 73 and bolt 75. A coiled spring 77 is carried by the bracket 49 and assists in counter balancing the weight of the arm 39 to give the arm 39 a "weightless" feel.

Turning now to the joint 59, this is included to ensure that no damage is done to the guard 27, the quadrilateral linkage 31 or the support 33 if a workpiece strikes the guard 27 with a force greater than a predetermined force. If a workpiece does strike the guard 27 with a significant force, the joint 59 releases automatically to allow the guard 27 to rise rather than remaining stationary and transferring the force to the support structure. To enable this to occur, the joint 59 is formed between the U-shaped support 33 and the bracket 49 using a spring 79, a pin 81, an end cap 83 and a spring support 85. The pin 81 passes diametrically through the tubular U-shaped support 33 and carries one end 79a of the spring 79 which is situated within the tubular support 33.

The other end of the spring 79 is carried by the spring support 85 which threadedly engages a protrusion 83a of the end cap 83.

The ends of the pin 81 extending outside the tubular support 33 abut one side of the bracket 49 and are received in ramped recesses 87. The end cap 83 abuts the other side of the bracket 49 such that the spring 79 is in tension. The end cap 83 also includes a pair of diametrically opposed nibs 89 which are received in notches 91 formed in the end of the tubular support 33. As a result of the engagement of the nibs 89 in the notches 91, twisting of the spring 79 in the tubular support 33 is avoided.

The spring 79 exerts a predetermined force between the end cap 83 and the pin 81. Hence, the pin 81 is retained in the recesses 87 of the bracket 49 with this predetermined force. Since relative movement between the tubular support 33 and the bracket 49 can only occur if the pin 81 is released from the recesses 87, this will only occur if a force greater than the predetermined force is applied to the guard 27 (and hence the joint 59). To set the predetermined force, it is simply necessary to disengage the nibs 89 of the end cap 83 from the notches 91 of the tubular support 33 such that the end cap 83 can be rotated to thread or unthread the spring support 85. By doing this, the tension in the spring 79 can be adjusted. A hexagonal keyhole 93 is provided in the end cap 83 to facilitate adjustment of the tension in the spring 79.

As will be appreciated, if a force greater than the predetermined force is applied to the guard 27, the joint 59 is released by virtue of the pin 81 being forced out of the recesses 87, thereby allowing the bracket 49 to rotate relative to the U-shaped support 33.

Damage to the guard 27 and/or support brackets/joints is thereby avoided. Further, it is a simple matter to relocate the guard 27 in its correct active position because the position can be found simply by rotating the joint 59 until the pin 81 re-engages the recesses 87 in the bracket 49. Of course, if the bracket 49 is rotated by 1800 relative to the U-shaped support 33, the ends of the pin 81 will re-engage in the recesses 87, but this time in opposite recesses.

It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention.

Claims (15)

1. A saw comprising a frame, a table mounted in the frame and adapted to adopt two positions, a pivot member on a first side of the table, a saw assembly pivoted with respect to the pivot member, a blade journalled in said assembly, a motor to drive the blade, and a slot in the table through which said blade is adapted to protrude, in a first of said two positions of the table the saw assembly being above the table, the saw thereby forming a chop saw for performing plunge cuts on workpieces supported on said first side of the table, and, in a second of said two positions of the table, the saw assembly being below the table and the saw thereby forming a bench saw for performing cuts on workpieces passed through the blade on a second opposite side of the table, the saw further comprising a guard which, when the table is in the second of the two positions, protects a user from the blade protruding through the slot, the guard being supported by a linkage which, if a force greater than a predetermined force is applied to the guard, releases the guard to prevent damage to the linkage or the guard.

2. A saw as claimed in claim 1, wherein the linkage includes a pivot joint which opposes pivotal motion with the predetermined force.

3. A saw as claimed in claim 1 or claim 2, wherein the linkage is held in a first position by a spring which exerts the predetermined force.

4. A saw as claimed in claim 3, wherein the spring urges a pin mounted on a first portion of the linkage into a recess formed in a second portion of the linkage, the pin being released from the recess when a force greater than the predetermined force is applied to the guard thereby releasing the guard.

5. A saw as claimed in claim 4, wherein the spring is mounted in tension between the pin and an end cap, the pin and end cap abutting opposite faces of the second portion of the linkage.

6. A saw as claimed in claim 5, wherein the first portion of the linkage comprises a tube which carries the pin and has a notch at its free end for receiving a nib of the end cap to prevent rotation of the end cap relative to the tube during use.

7. A saw as claimed in claim 6, wherein a spring holder is provided within the tube threadedly mounted on the end cap such that, when the nib of the end cap is withdrawn from the notch of the tube, the tension in the spring can be adjusted by rotating the end cap relative to the spring holder.

8. A saw as claimed in any one of claims 4 to 7, wherein the recess in the second portion of the linkage provides a ramp up which the pin can travel when a force greater than the predetermined force is applied to the guard.

9. A saw as claimed in any preceding claim, wherein the linkage includes a U-shaped support mounted on the table, the axis ofthe U extending substantially parallel to the plane of the table to accommodate workpieces passing over the table.

10. A saw as claimed in claim 9, wherein the U-shaped support can be retracted for packing or storage.

Il. A saw as claimed in claim 9 or claim 10, wherein a quadrilateral linkage between the guard and the U-shaped support ensures that, as the guard rises, the guard remains at substantially the same orientation relative to the table.

12. A saw as claimed in claim 11, wherein the quadrilateral linkage can locked to hold the guard in a desired position relative to the table.

13. A saw as claimed in claim 11 or claim 12, wherein the quadrilateral linkage comprises a pair of cables extending along an arm, each cable having a first end attached to a roller at one end of the arm and a second end solidly mounted at the other end of the arm, such that, as the guard is raised, the roller rotates to retain the guard in the desired orientation.

14. A saw as claimed in claim 13, wherein the quadrilateral linkage is locked by means of a device which squeezes the arm to grip the roller, thereby preventing rotation of the roller.

15. A saw according to claim 1 substantially as hereinbefore described with reference to and as shown in the accompanying drawings.