Abstract:
A saw including a base assembly, and a saw unit moveably mounted on the base assembly. The saw unit is movable towards or away from the base assembly. A pivotal guard is pivotally mounted on the saw unit. The guard can be pivoted from a first position surrounding at least a portion of the lower edge of a saw blade to a second retracted position exposing the portion of the lower edge of the saw blade. A flexible member is connected to the guard for moving the guard from the first position to the second retracted position when the saw unit is pivoted towards the base assembly.

Description:
BACKGROUND  
       [0001]     The present invention relates to power tools and in particular to chop saws or saws having having a chopping function, for example, a sliding compound miter saw.  
         [0002]     Chop saws typically comprise a motor unit pivotally mounted on a base. The motor unit is located above the base and can pivot between a high position where it is located further most away from the base to a low position where a circular saw blade, which is mounted on the motor unit and which is capable of being rotationally driven by a motor located within the motor unit, can engage with a work piece located on the base. A spring biases the motor unit to its upper most position.  
         [0003]     Such saws can have a sliding feature wherein the motor unit, in addition to be able to perform a pivotal or chopping movement, can slide linearly across the base to perform a slide cut. Furthermore, these types of saw can include mechanisms by which they are able to perform miter and/or bevel cuts on work pieces located on the base. A saw which is capable of performing chop, sliding, bevel and miter cuts is known as a sliding compound miter saw.  
         [0004]     All of these types of saw usually comprise guards which surround at least a part of the edge of the saw blade in order to prevent the operator from touching the cutting edge. Typically, such saws comprise a fixed guard which surrounds the cutting edge of the top half of the cutting blade and a pivotal guard which is capable of surrounding the cutting edge of the lower half of the cutting blade. The pivotal guard is capable of being pivoted from a first position where it surrounds the cutting edge of the lower half of the cutting blade to a retracted position where the cutting edge of the lower half of the cutting blade is exposed so that the cutting blade can be used to cut a work piece. The purpose of the pivotal guard is to enable the cutting edge of the lower half of the circular saw blade to be surrounded when the saw blade is not being used to provide protection to the operator whilst allowing the cutting edge of the lower half of the circular saw blade to be exposed when it is required to perform the cutting function.  
         [0005]     There are numerous mechanisms by which the pivotal guard can be pivoted from its first position to a retracted position.  
         [0006]     European Application No. EP 1380395 shows a chop saw which can also have a miter saw function. The saw comprises a saw assembly  20 H,  20 M,  17  (using the same reference numbers as those used in European Application No. EP 1380395) pivotally mounted onto a base  11  and which can pivot about an axis parallel to that of the axis of rotation of the cutting blade  17  away from or towards the base  11 . The saw assembly comprises a fixed upper blade guard  15  which surrounds an upper part of the cutting edge of the cutting blade  17 . A lower pivotal guard  16  surrounds the lower cutting edge of the cutting blade  17  when the saw assembly is in its upper most position. A mechanical linkage  16 L connects between the pivotal lower guard  16  and the base  11  such that, upon pivotal movement of the saw assembly downwards towards the base  11 , the lower pivotal guard  16  is pivotally retracted to uncover the lower cutting edge of the cutting blade  17  in order to allow it to be used to cut a work piece located on the base  11 .  
         [0007]     The mechanical linkage comprises a rigid link lever with pivot and cam type connectors. Due the rigid nature of the mechanical linkage and its way of operating, the saw assembly and base together with the pivot mechanism connecting the two, have to be so designed in order to accommodate it and as such, the way in which such saws using these types of rigid link levers are constructed is restricted.  
         [0008]     PCT Application No. WO 98/18588 describes another such mechanism. PCT Application No. WO 98/18588 discloses a sliding compound miter saw which comprises a base  12  (using the same reference numbers as those used in PCT Application No. WO 98/18588) 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 miter saw to perform miter 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 miter saw to perform bevel cuts.  
         [0009]     Slideably mounted onto the bevel mount  16  are two guide rods  34  which are capable of sliding horizontally, backwards and forwards. The rods  34  enable the sliding compound miter 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.  
         [0010]     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.  
         [0011]     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.  
         [0012]     As with the saw disclosed in European Application No. EP 1380395, the saw disclosed in PCT Application No. WO 98/18588 comprises rigid mechanical levers and therefore, due the rigid nature of the mechanical linkage and its way of operating, the saw assembly has to be so designed in order to accommodate it. As such, the way in which such saws using rigid link levers are constructed is restricted.  
         [0013]     European Application No. EP 0242733 discloses a different construction for a sliding compound mite saw to that disclosed in PCT Application No. WO 98/18588. European Application No. EP 0242733 discloses a sliding compound miter saw which comprises a base having a rotatable table mounted within it. The rotatable table, in conjunction with a fence fixed to the base, enables the sliding compound miter saw to perform miter cuts. Connected to the rear of the table is a bevel mount which is able to pivot about a horizontal axis in relation to the table. The pivotal movement of the bevel mount in relation to the table enables the sliding compound miter saw to perform bevel cuts.  
         [0014]     Pivotally mounted onto the bevel mount are two guide rods which are capable of pivoting about an axis, parallel to the axis of rotation of the saw blade of the saw, between an upper and lower position. This enables the saw to perform chop cuts.  
         [0015]     Slidingly mounted on the guide rods is a motor unit, which comprises a motor for rotationally driving the circular saw blade mounted on a drive spindle on the motor unit  36 . The sliding movement of the motor unit along the guide rods enables the saw to perform sliding cuts.  
         [0016]     Rigidly mounted to the motor unit is a fixed guard which surrounds the cutting edge of the top half of the cutting blade. Pivotally mounted to the motor unit is a pivotal guard 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 is exposed for use in cutting.  
         [0017]     The pivotal guard is pivoted between its two positions using a switch mounted on the handle which is mechanically linked to the pivotal guard. In use, the switch is depressed retracting the pivotal guard and then the saw can be operated. Unlike the saw in PCT Application No. WO 98/18588, there is no device disclosed which causes the pivotal guard to retract when the motor unit is pivoted towards the base. The use of such a mechanical linkage as described in PCT Application No. WO 98/18588 cannot be applied to saw in European Application No. EP 0242733 as the distance between the motor unit and the pivot axis, which is parallel to that of the axis of rotation of the cutting blade and about which the motor unit pivots towards or away from the base to perform a chopping action, varies as the motor unit slides along the two guide rods. This is in contrast to the design of saw in PCT Application No. WO 98/18588 where the distance between the motor unit and the pivot axis, parallel to that of the axis of rotation of the cutting blade and about which the motor unit pivots towards or away from the base to perform a chopping action, is fixed at a preset distance.  
         [0018]     The object of the present invention is to provide an alternative and more versatile design of mechanical linkage for a chop saw or a saw having a chopping function in order to move at least one pivotal guard from an enclosed position to a retracted position by pivotal movement of the saw blade unit during a chopping action and/or to provide such a linkage capable of being utilised on a saw as described in European Application No. EP 0242733.  
       SUMMARY  
       [0019]     Accordingly there is provided a saw comprising a base assembly a base assembly connected to a mounting portion, a saw unit connected to a support portion which is moveably mounted on the mounting portion to allow the saw unit to move towards or away from the base assembly, the saw unit having an output drive spindle upon which a circular saw blade can be rigidly mounted to be rotationally driven by a motor, at least one pivotal guard pivotally mounted on the saw unit which can pivot from a first position, where it surrounds at least a portion of the lower edge of a saw blade when mounted on the spindle, to a second retracted position where the portion of the lower edge of the saw blade is exposed, and a pivotal guard actuating mechanism which is capable of moving the at least one pivotal guard from its first position to its second retracted position when the saw unit is pivoted towards the base assembly, wherein the pivotal guard actuating mechanism comprises at least one Bowden cable comprising an inner cable slideable within an outer sleeve and which has two ends, each end comprising two parts, one part being one end of the inner cable and the other part being a corresponding end of the outer sleeve, wherein one part of the first end of the Bowden cable is connected to the base assembly and the other part of the first end of the Bowden cable is connected to the saw unit so that movement of the saw unit towards the base assembly causes relative movement of the cable of the Bowden cable within the sleeve of the Bowden cable; and one part of the second end of the Bowden cable is connected to the at least one pivotal guard and the other part of the second end of the Bowden cable is connected to the saw unit and is arranged so that the relative movement of the cable of the Bowden cable within the sleeve of the Bowden cable due to the movement of the saw unit towards the base assembly causes the at least one pivotal guard to move from its first position to its second retracted position.  
         [0020]     A person skilled in the art will appreciate that such arrangement can be used on any type of saw having a pivotal guard and which performs chopping function to provide a simple yet flexible design of pivotal guard actuating mechanism. Due to the flexible nature of a Bowden cable, the mechanical movement of the chopping action of the saw unit can easily be transferred to and converted into pivotal movement of the pivotal guard.  
         [0021]     One part of the first end of the Bowden cable can be connected to the base assembly via the mounting portion. The other part of the first end of the Bowden cable can be connected to the saw unit via the support portion. The mounting portion may be able to pivot relative to the base assembly to allow the saw to perform bevel cuts.  
         [0022]     A further advantage of using a Bowden cable is that it allows the saw unit to be able to be moved relative to the support portion to change the distance between the axis of rotation of the pivotal guard and the support portion. For example, the saw disclosed in European Application No. EP 0242733 could utilise a pivotal guard actuating mechanism as disclosed in this specification without any of its functions being impaired.  
         [0023]     Preferably, the support portion is pivotally mounted on the mounting portion to allow the saw unit to pivot towards or away from the base assembly, the axis of rotation of the drive spindle being substantially parallel to the axis of pivot between support portion and the mounting portion, wherein the one part of the first end of the Bowden cable is connected to the base assembly and the other part of the first end of the Bowden cable is connected to the saw unit so that pivotal movement of the saw unit towards the base assembly causes relative movement of the cable of the Bowden cable within the sleeve of the Bowden cable, and the one part of the second end of the Bowden cable is connected to the at least one pivotal guard and the other part of the second end of the Bowden cable is connected to the saw unit and is arranged so that the relative movement of the cable of the Bowden cable with in the sleeve of the Bowden cable due to the pivotal movement of the saw unit towards the base assembly causes the at least one pivotal guard to move from its first position to its second retracted position.  
         [0024]     Ideally, the saw unit can move relative to the support portion to change the distance between the axis of rotation of the pivotal guard and the axis of pivot between the support portion and the mounting portion.  
         [0025]     The support portion can be connected to the saw unit via at least one rail. If so, either the support portion or the rest of the saw unit can be fixed to the at least one rail and the other slides along the at least one rail to change the distance.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     Three embodiments of the present invention will now be described with reference to the accompanying drawings of which:— 
         [0027]      FIG. 1  shows a perspective view of the first embodiment of the saw;  
         [0028]      FIG. 2  shows a side view of the first embodiment with the saw assembly in the lower position;  
         [0029]      FIG. 3  shows a side view of the first embodiment with the saw assembly (partially cut away) in the upper position;  
         [0030]      FIG. 4  shows a side view of part of the locking mechanism of the saw;  
         [0031]      FIG. 5  shows a side view of the second embodiment of the saw with the saw assembly in its lower position;  
         [0032]      FIG. 6  shows a side view of the second embodiment of the saw with the saw assembly in its upper position;  
         [0033]      FIGS. 7A and 7B  show the pivotal bracket in its two angular positions;  
         [0034]      FIG. 8  shows a side view of the third embodiment of the saw with the saw assembly in its lower position;  
         [0035]      FIG. 9  shows a side view of the third embodiment of the saw with the saw assembly in its upper position;  
         [0036]      FIG. 10A  shows the cam follower of the third embodiment; and  
         [0037]      FIG. 10B  shows a cross section of the cam follower of  FIG. 10A  in the direction of Arrows N.  
     
    
     DETAILED DESCRIPTION  
       [0038]     The first embodiment of the invention will now be described with reference to FIGS.  1  to  4 . Referring to  FIG. 1 , the saw preferably comprises a base  2  to which a substantially circular table  4  may be mounted thereon. The circular table  4  can rotate about a vertical axis. An arm  6  is attached to the front of the circular table  4  which extends through a recess  8  formed in the front of the base  2  and then forward of the base  2 . As the circular table rotates, the arm  6  preferably swings within the recess  8 , the maximum amount of pivotal movement being limited by the sides  10  of the recess  8 . A latch  12  may be attached to the underside of the end of the arm  6  which is capable of releasably locking the angular position of the arm  6  within the recess  8  in well known manner. A fence  14  is rigidly attached to the base  2  and passes over the circular table  4 .  
         [0039]     A bevel support  16  may be pivotally attached to the rear of the circular table  4 . The bevel support  16  can pivot about a horizontal bevel axis  18 . The bevel support  16  can be locked in a range of angular positions relative to the circular table  4  using a locking handle  20 . The mechanism by which the locking handle  20  locks the bevel support  16  is of no relevance to the present invention and therefore shall not be described in more any detail.  
         [0040]     A slide support  22  may be pivotally mounted onto the bevel support  16  is. The slide support  22  can pivot about a chopping axis  24  which is parallel to the axis of rotation  26  of a cutting blade  28  (described further below).  
         [0041]     Rigidly mounted within the slide support  22  are the ends of two straight rods  30 ,  32 . The rods  30 ,  32  are preferably prevented from sliding or rotating within the slide support  22 . The rods  30 ,  32  may be located one above the other and are parallel to each other. A spring  36  may be attached to the end  34  of the top rod  30 . The other end of the spring  36  is preferably attached to the bevel support  16 . The spring  36  is preferably under tension, biasing the end  34  of the top rod  30  downwardly, biasing the ends of the two rods  30 ,  32  located remotely from the slide support  22  upwardly due to the pivotal connection of the slide support  22  to the bevel support  16 .  
         [0042]     A saw assembly  38  is preferably slideably mounted onto the two rods  30 ,  32 . The saw assembly  38  preferably comprises a motor housing  40  in which is mounted an electric motor (not shown). The electric motor is powered via an electric cable  42 . A handle  44  may be mounted on the rear of the motor housing  40 . A trigger switch  46  is preferably mounted within the handle  44 , which when depressed, activates the motor. A drive spindle  48  may project from the housing  40 . A circular saw blade  28  is preferably rigidly mounted onto the drive spindle  48 . When the motor is activated, the drive spindle rotates, rotatingly driving the saw blade  28 . A fixed guard  52  may be rigidly mounted onto the motor housing  40  and surrounds the top cutting edge of the saw blade  28 . A pivotal guard  54  is preferably pivotally mounted on the motor housing  40  and can pivot about the axis of rotation  26  of the saw blade  28 . The pivotal guard  54  can pivot between an enclosed position where it surrounds the lower cutting edge of the saw blade  28  and a retracted position where it exposes the lower cutting edge of the saw blade  28 . When the pivotal guard is in the retracted position, it is telescopically pivoted into the fixed guard  52 . A pivotal guard spring (not shown) biases the pivotal guard  54  to the enclosed position.  
         [0043]     The saw assembly  38  can slide along the two rods  30 ,  32  towards or away from the slide support  22 .  
         [0044]     In use, a work piece may be placed on the base  2  and circular table  4  against the fence  14 . The pivotal movement of the circular table  4  about the vertical axis allows the saw to perform miter cuts on the work piece. The pivotal movement of the bevel support  16  in relation to the circular table  4  about the bevel axis  18  allows the saw to perform bevel cuts on the work piece. The pivotal movement of the slide support  22  on the bevel support  16  about the chopping axis  24  allows the saw to perform chop cuts on the workpiece. The sliding movement of the saw assembly  38  along the two rods  30 ,  32  allows the saw to perform sliding cuts on the work piece.  
         [0045]     The saw preferably comprises a pivotal guard actuating mechanism. The pivotal guard actuating mechanism may cause the pivotal guard to pivot to its retracted position when the saw assembly is pivoted about the chopping axis  24  from its upper position to its lower position. The spring  36  preferably biases the saw assembly  38  to pivot about the chopping axis  24  to its uppermost position. In this position, the pivotal guard  54  encloses the lower edge of the cutting blade  28 . As the saw assembly is pivoted downwardly towards the circular table  4 , the pivotal guard actuating mechanism causes the guard  54  to retract into the fixed guard  52 , exposing the lower cutting edge of the blade  28 .  
         [0046]     The pivotal guard actuating mechanism will now be described in more detail with references to  FIGS. 1, 2  and  3 . The pivotal guard actuating mechanism preferably comprises a Bowden cable  60 . The Bowden cable  60  may comprise an outer sleeve  62  and an inner cable  64 . The Bowden cable  60  preferably has two ends, each end comprising two parts, one part being one end of the inner cable  64  and the other part being a corresponding end of the outer sleeve  62 .  
         [0047]     The first end of the Bowden cable  60  is preferably connected across the pivot joint formed between the bevel support  16  and the sliding support  22 . The end  66  of the sleeve  62  of the first end of the Bowden cable  60  is preferably rigidly connected to the sliding support  22  via a fixed support  68 . The end  70  of the cable  64  of the first end of the Bowden cable  60  is connected to the bevel support  16 .  
         [0048]     The second end of the Bowden cable  60  may be connected across the pivot joint formed between the fixed guard  52  and the pivotal guard  54 . The end  72  of the sleeve  62  of the second end of the Bowden cable  60  is preferably rigidly connected to the fixed guard  52 . The end  74  of the cable  64  of the second end of the Bowden cable  60  is preferably connected to the pivotal guard  54 . The cable  64 , between its second end  74  and the fixed end  72  of the sleeve  62 , may wrap around a tube  76  which surrounds the drive spindle  48 .  
         [0049]     The pivotal guard actuating mechanism operates as follows: The saw assembly is preferably biased to its upper position (as shown in  FIG. 3 ) by the spring  36  acting on the end  34  of the upper rod  30  (not shown in  FIG. 3 ). The pivotal guard spring preferably biases the pivotal guard  54  to its enclosed position where it surrounds the lower cutting edge of the saw blade  28 . When the pivotal guard is in this position, the end  74  of the cable  64  of the second end of the Bowden cable  60  is preferably pulled the furthest distance from the end  72  of the sleeve  62  of the second end of the Bowden cable  60  by the pivot guard spring. In contrast, the end  70  of the cable  64  of the first end of the Bowden cable  60  is preferably pulled into the sleeve  62 , causing it to be at the shortest distance from the end  66  of the sleeve  62  of the first end of the Bowden cable  60 .  
         [0050]     However, when the saw assembly is pivoted to its lowest position as shown in  FIG. 2 , the distance between the end  70  of the cable  64  of the first end of the Bowden cable  60  from the end  66  of the sleeve  62  of the first end of the Bowden cable  60  is forced to increase. This is due to the fact that the position of the end  70  of the cable  64  attached to the bevel support  16  remains stationary while the end  66  of the sleeve  62  attached to the sliding support  22  moves due to the relative pivotal movement between the bevel support  16  and the sliding support  22 . The increase in this length results in a decrease in the length of cable  64  between the end  72  of the sleeve  62  connected to the fixed guard  52  and the end  74  of the cable  64  attached to the pivotal guard  54 . As the cable  64  is retracted into the sleeve  62  at the second end of the Bowden cable  60 , it travels around the tube  76 , preferably causing the pivotal guard  54  to pivot to its retracted position.  
         [0051]     When the saw assembly is pivoted to its highest position, the distance between the end  70  of the cable  64  of the first end of the Bowden cable  60  from the end  66  of the sleeve  62  of the first end of the Bowden cable  60  is preferably reduced allowing the pivotal guard  54  to pivot to its enclosed position due to the biasing force of the pivotal guard spring.  
         [0052]     The saw also comprises a locking mechanism which will now be described with reference to  FIG. 4 . When the saw is not in use, it is desirable to be able to lock the position of the saw assembly  38  relative to the bevel support  16  in a storage position. When the saw is not in use, the saw assembly moves to its uppermost position ( FIG. 3 ) due to the biasing force of the spring  36 . The saw assembly  38  then preferably slides under gravity along the rods  30 ,  32  which are inclined due to the spring  36 , towards and abuts against the sliding support  22 . It is desirable to lock the saw assembly in this storage position and prevent accidental movement of the saw assembly  38  in relation to the bevel support  16 .  
         [0053]     The locking mechanism preferably comprises a retracting rod  80  slideably mounted within the handle  44 . The retraction rod  80  can slide along axis  82  in the direction indicated by Arrow A as shown in  FIG. 4 . Formed on one end of the retraction rod  80  is a finger pad  84  which projects through the handle  44  and by which a user can engage the retraction rod  80  to release the locking mechanism.  
         [0054]     Pivotally connected about point  86  to the other end of the retraction rod  80  is a locking rod  88 . The locking rod  88  preferably extends pass the fixed guard  52  towards the bevel support  16 . A hook  90  is preferably formed on the end of the locking rod  88  closest to the bevel support  16 . A catch  92  (as seen in  FIGS. 2 and 3 ) may be mounted on the bevel support  16 . When the saw assembly  38  is in its storage position as shown in  FIG. 3 , the hook  90  preferably engages with the catch  92  to lock the saw assembly  38  in this position. When the saw assembly is locked in this position, it cannot pivot downwardly about axis  24  or slide along the rods  30 ,  32 . The hook  90  is preferably kept in engagement with the catch  92  via a spring  94 , connected between the locking rod  88  and the motor housing  40 , which biases the hook  90  downwardly.  
         [0055]     A cam surface  96  may be formed on the locking rod  88  in close proximity to the hook  90 . A peg  98  is formed on the motor housing  40  which engages with the cam surface  96 . The spring  94  biases the peg  98  and the cam surface  96  into engagement. When the hook  90  is engaged with the catch  92 , the peg  98  is preferably located in the uppermost position along the cam surface  96  as shown in  FIG. 4 .  
         [0056]     In order to release the hook form the catch  92 , an operator preferably depresses the finger pad  84 , moving it away from the bevel support  16  and causing the retraction rod  80  to slide along the axis  82 . This in turn pulls the locking rod  88  away from the bevel support  16 . This preferably results in the peg  98  sliding along the cam surface  96  causing the locking rod  88  to move upwards against the biasing force the spring  94 . This causes the hook  90  to be moved above the catch  92 , allowing the operator to move the saw assembly  38  using the handle  44  either by pivoting it about axis  24  or sliding it along rods  30 ,  32 . When the operator ceases to depress the finger pad  84 , the biasing force of the spring  94  moves the hook downwardly.  
         [0057]     In order to re-engage the hook  90  with the catch  92 , the operator preferably places the saw assembly in the storage position. As the saw assembly moves into the storage position, the hook  90  preferably rides over and then engages with the catch  92  due to its shape.  
         [0058]     The second embodiment of the present invention will now be described with reference to  FIGS. 5, 6  and  7 . Where the same features are present in the second embodiment are present in the first embodiment, the same reference numbers have been used.  
         [0059]     The second embodiment of the present invention is the same as the first embodiment except for the mechanism by which the end  70  of the cable  64  of the Bowden cable  60  is connected to the bevel support  16 . In the first embodiment, the end  70  is connected directly to the bevel support  16 . In the second embodiment, it is preferably connected to the bevel support  16  via a pivotal bracket  200 . The pivotal bracket is shown in  FIGS. 7A and 7B .  
         [0060]     The pivotal bracket  200  preferably comprises two arms  202 ,  204  which extend from a central pivot point  206  as best seen in  FIGS. 7A and 7B . The pivotal bracket  200  is preferably made from a sheet of metal and of a substantially uniform thickness across its length.  
         [0061]     A straight slot  208  may be formed in the lower arm  202 . A curved slot  210  may be formed in the upper arm  204 . The pivotal bracket  200  is preferably pivotally mounted on the bevel support  16  at its central pivot point  206  and is capable about a pivot axis, which passes through the pivot point  206  perpendicularly to the surface of the page on which  FIGS. 7A and 7B  are located.  
         [0062]     The end  70  of the cable  64  of the Bowden cable  60  preferably connects to the lower arm  202  by engaging with the slot  208 . The end  70  of the cable is preferably located and held at the end of the slot  208  which is furthest away from the central pivot  206 , as shown in  FIGS. 5 and 6 . The end  70  is preferably held in this position by the tension on the cable  64 . Though the end  70  is held at the end of the slot  208 , the end  70  can pivot relative to the end of the lower arm  202  as shown in  FIGS. 5 and 6 . This is to accommodate the changes in both the orientation of the cable  64  of the Bowden cable  60  and the pivotal bracket  200 .  
         [0063]     A peg  212  is preferably rigidly mounted on the sliding support  22 . The peg  212  preferably locates within the curved slot  210  of the upper arm  204  of the pivotal bracket  200 . The peg  212  may be capable of sliding along the curved slot  210 . As the sliding support  22  pivots as the saw assembly moves from its upper position ( FIG. 6 ) to its lower position ( FIG. 5 ), the peg  212  is preferably forced to slide from the bottom end of the curved slot  210  ( FIG. 6 ) to the top end ( FIG. 5 ).  
         [0064]     As the peg  212  slides within the slot  210 , the pivotal bracket  200  preferably pivots about the central pivot point  206  due to the position of the slot  210  following the peg  212 , in order to enable peg  212  to slide within the slot  210 . The pivotal movement of the pivotal bracket  200  is preferably dependent on the profile of the slot  210 . The profile or edge of the slot  210 , in effect, acts as a cam surface and the peg  212  acts as cam follower, which follows the cam surface as it slides down the slot  210 .  
         [0065]     In this particular design, the profile of slot  210  is preferably that of a curve, as best seen in  FIGS. 7A and 7B .  
         [0066]     Pivotal movement of the pivotal bracket  200  preferably results in pivotal movement of a lower arm  202  which in turn results in pivotal movement of the end  70  of the cable  64  of the Bowden cable  60 .  
         [0067]     The profile of the slot  210  is preferably designed so that as the saw assembly is pivoted from its upper position ( FIG. 6 ) to its lower position ( FIG. 5 ), the end of the lower arm  202  and hence the end  70  of the cable  64 , first pivots downwardly (first part of the movement) and then subsequently pivots upwardly slightly (second part of the movement). As such, the distance between the end  70  of the cable  64  of the first end of the Bowden cable  60  and the end  66  of the sleeve  62  of the first end of the Bowden cable  60  is altered both by the end  66  of the sleeve  62  moving upwards and the end  70  of the cable  64  moving downwards. Movement of the end  66  of the sleeve  62  of the first and of the Bowden cable  60  is directly dependent pivotal position of the sliding support  22 . Movement of the end  70  of the cable  64  is dependent on the profile of the slot  210 .  
         [0068]     The movement of the end  70  of the cable  64  due to the curved slot  210  disclosed in  FIGS. 7A and 7B  is preferably first downward and then return slightly upwards. When the sliding support  22  pivots on the bevel support  16  at a uniform rate to move the saw assembly from its upper position to its lower position, and when the end  70  is travelling downwardly (during the first part of the movement), the rate at which the end  66  of the sleeve  62  is moving away from the end  70  of the cable  64  is increased. This results in the pivotal guard pivoting its retracted position at an increased rate. When the sliding support  22  pivots on the bevel support  16  at a uniform rate to move the saw assembly from its upper position to its lower position, and when the end  70  is travelling upwardly (during the second part of the movement), the rate at which the end  66  of the sleeve  62  is moving away from the end  70  of the cable  64  is decreased. This results in the pivotal guard pivoting towards its retracted position at a decreased rate.  
         [0069]     This enables the pivotal guard to be retracted at a quicker rate initially, thus exposing the cutting edge sooner when the saw assembly  38  is at a higher position, and then retracted at a slower rate over the latter stage of the pivotal movement as the saw assembly approaches the circular table  4 .  
         [0070]     When the saw assembly pivots from its lowest position ( FIG. 5 ) to its highest position ( FIG. 6 ) the peg  212  follows the slot  210  in the opposite direction, causing the reverse movement of the pivotal guard  54 , its rate of movement from its retracted position to its enclosed position being altered by the pivotal movement of the pivotal bracket  200 .  
         [0071]     A third embodiment will now be described with reference to  FIGS. 8, 9  and  10 . Where the same features are present in the third embodiment which are present in the second embodiment, the same reference numbers have been used. The third embodiment is the same as the second embodiment except that the design of the pivotal bracket  200  in the second embodiment together with the peg  212  has been changed.  
         [0072]     The pivotal bracket  200  has been replaced by a pivotal lever  300  as shown in  FIGS. 10A and 10B . The pivotal lever  300  is preferably pivotally mounted on the bevel support  16 . The pivotal lever  300  is shown in  FIGS. 10A and 10B .  
         [0073]     The pivotal lever  300  preferably comprises an arm  302  which extends from a pivot point  306  as best seen in  FIG. 10A . The pivotal lever  300  is preferably made from a sheet of metal and of a substantially uniform thickness across its length.  
         [0074]     A straight slot  308  may be formed at the end of the arm  302  remote from the pivot point  306 . A curved bulge  310  is preferably formed on the side of the arm  302 .  
         [0075]     The pivotal lever  300  is preferably pivotally mounted on the bevel support  16  at its pivot point  306  and is capable of pivoting about a pivot axis  304  (see  FIG. 10B ), which passes through the pivot point  206 , in the direction perpendicular to the surface of the page on which  FIG. 10A  is located.  
         [0076]     The end  70  of the cable  64  of the Bowden cable  60  preferably connects to the arm  302  by engaging with the slot  308 . The end  70  of the cable is preferably located and held at the upper end of the slot  308  as shown in  FIG. 10A , which end is furthest away from the pivot point  306 , as shown in  FIGS. 8 and 9 . The end  70  is preferably held in this position by the tension on the cable  64 . Though the end  70  is held at the end of the slot  308 , the end  70  can pivot relative to the end of the arm  302  as shown in  FIGS. 8 and 9 . This is to accommodate the changes in both the orientation of the cable  64  of the Bowden cable  60  and the end of the pivotal lever  300 .  
         [0077]     A roller  312  may be rotatably mounted on the sliding support  22 . The roller  312  is preferably mounted using ball bearings to minimise any rotational friction and is capable of freely rotating about its axis. The roller  312  preferably locates against the outer edge of the curved bulge  310  of the arm  302  of the pivotal lever  300 . The roller  312  is capable of rolling around the edge of the curved bulge  210 . The tension on the cable  64  preferably pulls on the end of the pivotal lever  300  biasing the end of the lever upwards (ie the lever  300  is pivotally biased about the pivot point  306  in a clockwise direction) as shown in  FIGS. 8 and 9  causing the curved bulge  310  to abut against and be held in contact with the roller  312 . As the sliding support  22  pivots as the saw assembly moves from its upper position ( FIG. 9 ) to its lower position ( FIG. 8 ), the roller  312  is preferably forced to roll from the right side of the curved bulge  310  ( FIG. 9 ), over the bulge  310 , to the left side of the bulge  310  ( FIG. 8 ).  
         [0078]     As the roller  312  rolls around the bulge  310 , the pivotal lever  300  preferably pivots about the central pivot point  206  due to the position of the curved bulge  310  following the roller  312 , in order to enable roller  312  to roll over the bulge  210 . The pivotal movement of the pivotal lever  300  is preferably dependent on the profile of the bulge  310 . The profile or edge of the bulge  310 , in effect, acts as a cam surface and the roller  312  acts as a cam follower, which follows the cam surface as it rolls around the bulge  210 .  
         [0079]     In this particular design, the profile of bulge  310  is that of a curve, as best seen in  FIG. 10A .  
         [0080]     Pivotal movement of the pivotal lever  300  preferably results in pivotal movement of the arm  302  which in turn results in pivotal movement of the end  70  of the cable  64  of the Bowden cable  60 .  
         [0081]     The profile of the bulge  310  is preferably designed so that as the saw assembly is pivoted from its upper position ( FIG. 9 ) to its lower position ( FIG. 8 ), the end of the arm  302  and hence the end  70  of the cable  64 , first pivots downwardly (first part of the movement) and then subsequently pivots upwardly slightly (second part of the movement), as shown in the  FIGS. 8 and 9 . As such, the distance between the end  70  of the cable  64  of the first end of the Bowden cable  60  and the end  66  of the sleeve  62  of the first end of the Bowden cable  60  is altered both by the end  66  of the sleeve  62  moving upwards and the end  70  of the cable  64  moving downwards. Movement of the end  66  of the sleeve  62  of the first end of the Bowden cable  60  is directly dependent pivotal position of the sliding support  22 . Movement of the end  70  of the cable  64  is preferably dependent on the profile of the bulge  310 .  
         [0082]     The movement of the end  70  of the cable  64  due to the curved bulge  310  disclosed in  FIG. 10A  is preferably first downward and then return slightly upwards. When the sliding support  22  pivots on the bevel support  16  at a uniform rate to move the saw assembly from its upper position to its lower position, and when the end  70  is travelling downwardly (during the first part of the movement), the rate at which the end  66  of the sleeve  62  is moving away from the end  70  of the cable  64  is increased. This results in the pivotal guard pivoting its retracted position at an increased rate. When the sliding support  22  pivots on the bevel support  16  at a uniform rate to move the saw assembly from its upper position to its lower position, and when the end  70  is travelling upwardly (during the second part of the movement), the rate at which the end  66  of the sleeve  62  is moving away from the end  70  of the cable  64  is decreased. This results in the pivotal guard pivoting towards its retracted position at a decreased rate.  
         [0083]     This enables the pivotal guard to be retracted at a quicker rate initially, thus exposing the cutting edge sooner when the saw assembly  38  is at a higher position, and then retracted at a slower rate over the latter stage of the pivotal movement as the saw assembly approaches the circular table  4 .  
         [0084]     When the saw assembly pivots from its lowest position ( FIG. 8 ) to its highest position ( FIG. 9 ) the roller  312  follows the bulge  310  in the opposite direction (left to right in  FIGS. 8 and 9 ), causing the reverse movement of the pivotal guard  54 , its rate of movement from its retracted position to its enclosed position being altered by the pivotal movement of the pivotal lever  300 .  
         [0085]     The second and third embodiments of this invention describe how the end  70  of the cable  64  of the Bowden cable  60  is attached to the bevel support  16  via a cam mechanism which operates when the saw unit  38  is pivoted towards the circular table  4  to cause movement of the end  70  of the cable  64  relative to the bevel support  16 . The end  66  of the sleeve  62  of the Bowden cable  60  is preferably connected directly to the sliding support  22  and moves relative to the bevel support  16  due to the pivotal movement of the sliding support  22  on the bevel support  16  only. However, a person skilled in the art will appreciate that the end  66  of the sleeve  62  of the Bowden cable  60  can be connected via a cam mechanism to the sliding support  22  so that it moves relative to the sliding support  22  by operation of the cam when the saw unit  38  is pivoted towards the circular table. This movement would be in addition to the movement caused by the pivotal movement of the sliding support  22  on the bevel support  16 . This use of a cam with the end  66  of the sleeve  62  can be in addition to or instead of the use of a cam with the end  70  of the cable  64  of the Bowden cable  60 . The construction of such a cam for use with the sleeve  62  can be the same as or similar to that described in the second and third embodiments used with the end  70  of the cable  64 .  
         [0086]     Persons skilled in the art may recognize other alternatives to the means disclosed herein. However, all these additions and/or alterations are considered to be equivalents of the present invention.