Abstract:
A saw with a pivotal guard which can pivot from a first position surrounds at least a portion of the lower edge of the saw blade to a second retracted position where the portion of the lower edge of the saw blade is exposed. A biasing mechanism may be provided for biasing the pivotal guard towards the first position. A pivotal guard actuating mechanism is capable of moving the pivotal guard from the first position to the second retracted position. The pivotal guard actuation mechanism includes a hand lever, a cam mechanism comprising a cam and cam follower connected between the hand lever and the pivotal guard wherein the cam is connected to the pivotal guard and the cam follower is connected to the hand lever.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to saws, and in particular to chop saws or saws having a chopping function, for example, a sliding compound mitre saws, and more in particular to guard mechanisms for such saws. 
       BACKGROUND 
       [0002]    Chop saws comprise a cutting unit pivotally mounted on a base assembly. The cutting unit is located above the base and can pivot between a high position where it is located further most away from the base assembly to a low position where a circular saw blade, which is mounted on the cutting unit and which is capable of being rotationally driven by a motor located within the cutting unit, can engage with a work piece located on the base assembly. A spring biases the cutting unit to its uppermost position. 
         [0003]    Such chop saws can have a sliding feature wherein the cutting unit, in addition to be able to perform a pivotal or chopping movement, can slide linearly across the base assembly 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 workpieces located on the base assembly. 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 while 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]    EP0242733 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 cutting unit, which comprises a motor for rotationally driving the circular saw blade mounted on a drive spindle on the motor unit. The sliding movement of the motor unit along the guide rods enables the saw to perform sliding cuts. 
         [0009]    Rigidly mounted to the cutting unit is a fixed guard which surrounds the cutting edge of the top half of the cutting blade. Pivotally mounted to the cutting 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. 
         [0010]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a perspective view of a miter saw; 
           [0012]      FIG. 2  shows the cutting unit together with the pivotal blade guard from a first perspective; 
           [0013]      FIG. 3  shows a portion of the cutting unit from a second perspective, with the pivotal blade guard shown in a first position; 
           [0014]      FIG. 4  shows the pivotal guard activation mechanism; and 
           [0015]      FIG. 5  shows a portion of the cutting unit from the second perspective, with the pivotal blade guard shown in the first position. 
       
    
    
     DESCRIPTION 
       [0016]    Referring to  FIG. 1 , the miter saw comprises a base assembly comprising a base  6  and a rotatable table  100 . The base  6  preferably has two platforms  12  formed symmetrically on either side of the base  6 . The rotatable table  100  is preferably rotatably mounted on the base  6  between the two platforms  12 . The top surface  102  of rotatable  100  preferably lies flush with the top surfaces  104  of the two platforms  12 . The combined surfaces  102 ,  104  of the rotatable table  100  and platforms  12 , respectively, may form a work surface. 
         [0017]    An extension arm  106  is rigidly attached to the rotatable table  100  which extends forward in well-known manner. The rotatable table  100  and extension arm  106  can pivot about a vertical axis through a range of angular positions. The angular movement is preferably restricted by the extension arm  106  engaging with one or other of the sides  108  of the platforms  12 . 
         [0018]    A locking lever  120  can be used to lock the rotatable table  100  and extension arm  106  in desired angular positions. A scale  122  is attached to the base  6  to indicate the angular position of the extension arm  106 . Carrying handles  10  are attached to the sides of the base  6 . 
         [0019]    A mount  27  is preferably pivotally mounted on the rear of the rotatable table  100 . The mount  27  can pivot about a horizontal axis on the rotatable table to enable the saw to perform bevel cuts. Two guide rods (not shown) are rigidly attached to a base  25  which is pivotally attached to the mount  27  via a pivot joint. A cutting unit  50  is preferably slideably mounted on the two guide rods. 
         [0020]    The external housing of the cutting unit  50  may be constructed from four clam shells  300 ,  302 ,  304 ,  306 . The first clam shell  300  preferably forms a motor housing in which an electric motor (not shown) is mounted. The clam shell  300  may be attached to the second clam shell  302  using bolts. The second and third clam shells  302 ,  304  are preferably attached to each other using bolts and form a guide rod support housing, in which the two guide rods are slideably mounted, and half of the fixed blade guard which surrounds the top section of a cutting blade  124  mounted on an output spindle (not shown) of the motor. The fourth clam shell  306  preferably attaches to the third clam shell  304  and forms the second half of the fixed blade guard. 
         [0021]    A pivotal blade guard  308  is preferably mounted on the third clam shells  304  in a pivotal manner and which is described in more detail below. The pivotal guard  308  can be moved from a first position (which is shown in  FIG. 5 ) where it encloses the lower section of the cutting blade  124  (to prevent an operator from touching the lower cutting edge of the cutting blade  124 ) to a second position (which is shown in  FIGS. 2, 3 and 4 ) where it is telescoped inside of the fixed guard  304 ,  306  to expose the lower section of the cutting blade  124  for cutting. 
         [0022]    The pivot joint preferably enables the two rods and the cutting unit  50  to pivot about an axis relative to the mount  27  to enable the two rods  200  and the cutting unit  50  to pivot away from or towards the rotatable table  100  and extension arm  106 . This enables the saw to perform chop cuts. A spring (not shown), which preferably forms part of the pivot joint, biases the mount  27  and guide rods to their highest position. 
         [0023]    A handle  114  may be formed by the second and third clam shells  302 ,  304 , and preferably extends from the front of the cutting unit  50  by which a user moves the cuffing unit  50  towards or away from the rotatable table  100  and extension arm  106 . A pivotal hand lever  116  is preferably mounted on the handle  114  by which an operator can move the pivotal guard  308  and which is described in more detail below. An electric switch  118  may also mounted on the handle  114 , the depression of which preferably activates the electric motor. 
         [0024]    A fixed fence  16  may be rigidly attached on top of the two platforms  12  of the base  6  at the rear of the platforms  12 . The fence  16  preferably extends across the rotatable table  100  but does not interfere with its rotational movement. 
         [0025]    The pivotal guard control mechanism will now be described with reference to  FIGS. 2 to 5 . The pivotal guard  308  preferably includes a central hub  310  which is rotatably mounted on the third clam shell  304  of the cutting unit  50  to enable the pivotal guard  308  to pivot over a range of positions. The pivotal guard  308  can be pivoted (clockwise in  FIG. 4 ) from a first position where it encloses the lower section of the cutting blade  124  to a second position where it is telescoped inside of the fixed guard  304 ,  306 . A helical spring  312  preferably biases the pivotal guard  308  towards its first position. 
         [0026]    The pivotal hand lever  116  is preferably mounted on the handle  114 . The hand lever  116  preferably includes a first section  314  which is located on the outside of the handle  114  (as best seen in  FIG. 2 ) connected to a second section  316  located on the inside of the handle  114  at a pivot point  318 . The pivot point  318  may also comprise two arms  320  which locate in recesses formed in the inner wall of the second and third clam shells  302 ,  304  inside of the handle  114 . The hand lever  116  preferably pivots on the arms  320  about an axis  322 . 
         [0027]    An elongate rod  324  may be pivotally mounted on the inner wall of the third clam shell  304 . The rod  324  is preferably pivotally mounted on a bolt  326  which passes through a hole in the rod  324  and screws into the third clam shell  304 . The rod  324  can pivot about an axis  328 . 
         [0028]    One end of the rod  324  preferably comprises an elongate slot  330 . A lever slot  332  may be formed in the end of the second section  316  of the hand lever  116 . A bar  334  preferably extends across the lever slot  332 . The end of the rod  324  with the elongate slot  330  may pass through the lever slot  332 . The bar  334  preferably extends through the elongate slot  330  of the rod  324 . As the hand lever  116  is pivoted, the end of the second section  316  of the hand lever  116  will pivot towards or away from the pivotal guard  308 , the bar  334  sliding back and forth along the elongate slot  330  as it does so. As the end of the second section  316  moves towards the pivotal guard  308 , the bar  334  will move upwardly relative to the bolt  326  causing the end of the rod  324  with the elongate slot  330  to move upwardly as well. As such, the rod  324  pivots clockwise (as shown in  FIG. 4 ) about the bolt  326 . As the end of the second section  316  moves away from the pivotal guard  308 , the bar  334  will move downwardly relative to the bolt  326  causing the end of the rod  324  with the elongate slot  330  to move downwardly as well. As such, the rod  324  pivots counter-clockwise (as shown in  FIG. 4 ) about the bolt  326 . 
         [0029]    A freely rotatable wheel  340  may be mounted on an axle  328  on the second end of the rod  324 , opposite to the end with the elongate slot  330 . The axes of rotation of the hand lever  116 , the rod  324  and the wheel  340  are preferably parallel to each other. 
         [0030]    A cam wall  344  may be formed on a side wall  342  of the pivotal guard. The wheel  340  and cam wall  344  can act as a cam mechanism with the cam wall  344  acting as a cam and the wheel  340  as a cam follower. The cam wall  344  preferably spirals outwardly around the axis of pivot of the pivotal guard around the central hub  310  with the first end  346  of the cam wall  344  closest to the rear of the saw being closest to the hub  310  while the with the second end  348  of the cam wall  344  furthest from the rear of the saw being furthest away from the hub  310 . The helical spring  312  preferably biases the pivotal guard  308  ant-clockwise as shown in  FIG. 4 . 
         [0031]    This results in the cam wall  344  coming into engagement with the wheel  340 . As the spring  312  urges the pivotal guard  308  counter-clockwise as shown in  FIG. 4 , the wheel  340  is urged to travel along the cam wall  344  towards the first end  346 , the pivotal guard  308  and cam wall  344  rotating as it does so. As the wheel  340  travels along the cam wall  344 , it approaches the first end  346  of the cam wall  344  closest to the hub  310 . This results in the rod  324  pivoting clockwise (as shown in  FIG. 4 ) about the bolt  326  as it does so. This in turn moves the end of the rod  324  with the elongate slot  330  upwards which in turn causes the section  316  of the hand lever  116  to rotate ant-clockwise about the axis  322  (as shown in  FIG. 4 ). This results in the first section  314  also rotating counter-clockwise, moving the end of the first section  314  away from the external wall of the handle  114  (as shown in  FIG. 5 ). As such, when no pressure is applied to the hand lever  116 , the pivotal guard  308  is moved under the biasing force of the spring  312  to its first position, which in turn cause the rod  324  to pivot clockwise (as shown in  FIG. 4 ) and the hand lever  116  counter-clockwise due to the camming action of the wheel  340  and the cam wall  344 . The spring  312  preferably holds the pivotal guard  308  in its first position and the first section  314  of the hand lever  116  away from the handle  114 . 
         [0032]    When an operator wishes to open the pivotal guard  308 , the operator applies a pressure to the first section  314  of the hand lever  116  moving it towards and into engagement with the outer surface of the handle  114 . This results in the hand lever  116  pivoting in a clockwise direction (as shown in  FIG. 4 ). This results in the bar  334  moving downwardly, the bar  334  sliding rearwardly within the elongate slot  330  of the rod  324 . As this happens, the rod  324  is pivoted counter-clockwise (as shown in  FIG. 4 ) forcing the wheel  340  to move away from the hub  310 . This causes the wheel  340  to pivot the cam wall  344 , due to the cam action between the cam wall  344  and wheel  340 , clockwise (as shown in  FIG. 4 ) in order for the second end  348  of the cam wall  344  wheel  340  to move towards the wheel  340  as the second end  348  being located further from the hub  310 , the wheel  340  rolling along the side of the cam wall  344  as the cam wall pivots. The pivotal movement of the cam wall  344  results in pivotal movement of the pivotal guard  308 . This movement is against the biasing force of the spring  312 . This results in the pivotal guard  308  moving to its second position, exposing the lower edge of the, cutting blade  124  as shown in  FIGS. 2, 3 and 4 . 
         [0033]    In order to move the pivotal guard back to its first position, the operator simply removes the pressure of the hand lever  116 , and allow the spring  312  to move the pivotal guard back to its first position. The first section  314  of the hand lever  116  is preferably moved away from the handle  114  by the cam action of the wheel  340  on the cam wall  344  as the wheel  340  moves from the second end  348  towards the first end  346  as shown in  FIG. 5 . 
         [0034]    While the present invention has been described in relation to a sliding compound miter saw, it will be appreciated that it is applicable to any saw with a pivotal guard.