Abstract:
A saw having a base assembly having a mounting portion and a saw unit pivotally mounted to the mounting portion. The saw unit is pivotable from an uppermost position away from the base assembly to a lowermost postion towards the base assembly. A locking mechanism locks the saw unit relative to the base assembly when the saw unit is in its uppermost position and in a position closest to the mounting portion.

Description:
BACKGROUND  
       [0001]     The present invention relates to powered saws having a chopping and sliding function.  
         [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]     PCT Application No. WO 98/18588 describes one construction of a sliding compound miter saw. 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.  
         [0005]     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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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.  
         [0009]     The object of the present invention is to provide a locking mechanism for sliding compound miter saws to lock them in a storage position.  
       SUMMARY  
       [0010]     Accordingly there is provided a saw comprising a base assembly connected to a mounting portion, a saw unit pivotally mounted on the mounting portion to allow the saw unit to pivot 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, the axis of rotation of the drive spindle being substantially parallel to the axis of pivot between saw unit and the mounting portion, pivotal biasing means to urge the saw unit to its upper most pivotal position, 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 guide mechanism which enables the saw unit to move linearly relative to the mounting portion in order to change the distance between the axis of rotation of the pivotal guard and the mounting portion; and guide biasing means to urge the saw unit towards a position closest to the mounting portion, and a locking mechanism which is capable of locking the position of the saw unit relative to the base assembly when the saw unit is in its uppermost pivotal position and in the position closest to the mounting portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     An embodiment of the present invention will now be described with reference to the accompanying drawings of which:  
         [0012]      FIG. 1  shows a perspective view of an embodiment of the saw;  
         [0013]      FIG. 2  shows a side view of the saw with the saw assembly in the lower position;  
         [0014]      FIG. 3  shows a side view of the saw with the saw assembly (partially cut away) in the upper position; and  
         [0015]      FIG. 4  shows a partial side view a locking mechanism of the saw. 
     
    
     DETAILED DESCRIPTION  
       [0016]     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 preferably rigidly attached to the base  2  and passes over the circular table  4 .  
         [0017]     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.  
         [0018]     A slide support  22  may be pivotally mounted onto the bevel support  16 . The slide support  22  can pivot about a chopping axis  24  which is substantially parallel to the axis of rotation  26  of a cutting blade  28  (described further below).  
         [0019]     The ends of two straight rods  30 ,  32  may be rigidly mounted within the slide support  22 . 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 .  
         [0020]     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.  
         [0021]     The saw assembly  38  can slide along the two rods  30 ,  32  towards or away from the slide support  22 .  
         [0022]     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.  
         [0023]     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 .  
         [0024]     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 .  
         [0025]     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 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 .  
         [0026]     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 .  
         [0027]     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 .  
         [0028]     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.  
         [0029]     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.  
         [0030]     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 .  
         [0031]     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.  
         [0032]     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.  
         [0033]     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 .  
         [0034]     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.  
         [0035]     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.  
         [0036]     Persons skilled int eh 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.