Abstract:
A saw including a base assembly having a work surface, a cutting unit mounted on the base assembly capable of cutting a work piece located on the work surface, and a fixed fence mounted on the base assembly for supporting the work piece when it is being cut. The base assembly has a rib abutting the fixed fence, The fixed fence abuts against the rib in a direction of a force applied to the fixed fence by the work piece when it is being cut.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a saw having a fixed fence for supporting a work piece. 
       BACKGROUND 
       [0002]    Numerous types of saw comprise a base structure upon which a work piece is located in order for it to be cut. For example, on chop saws, miter saws, bevel saws, sliding saws and compound miter saws, the work piece is held stationary on the base while the saw blade is moved towards or across the base structure in order to cut the work piece located on it. On other types of saw, for example, a table saw or band saw, the work piece is slid across the base structure in order for it to engage with a cutting blade having an overall stationary position. In all of these types of saws, the position of the work piece is controlled by a fence which is attached to the base structure. Some fences are permanently fixed in a non-moveable manner to the base and are referred to as a “fixed fence.” Others are mounted in a moveable manner on the base structure so that their position can be adjusted and are known as a “moveable fence.” 
         [0003]    The present invention relates to a fixed fence and the mechanism by which it is mounted to a base structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a perspective view of a miter saw; 
           [0005]      FIG. 2  shows a rear view of the base and fixed fence only according to the first embodiment; 
           [0006]      FIG. 3  shows a front exploded view of the base and fixed fence; 
           [0007]      FIG. 4  shows a rear view of part of the base and fixed fence; and 
           [0008]      FIG. 5  shows a schematic diagram of a vertical cross section of part of a side portion of the fence with a recess according to a second embodiment; 
           [0009]      FIG. 6  shows a rear view of the fence according to a third embodiment; 
           [0010]      FIG. 7  shows a vertical cross section of a bolt which attaches the fence as shown in  FIG. 6 ; and 
           [0011]      FIG. 8  shows a schematic diagram of an exploded view of the bolt and the aperture through the side portion of the fence as shown in  FIG. 7 . 
       
    
    
     DESCRIPTION 
       [0012]    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. 
         [0013]    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 . 
         [0014]    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 . 
         [0015]    A mount  27  is preferably pivotally mounted on the rear of the rotatable table  100 . Two guide rods (not shown) may be pivotally attached to the mount  27 . A cutting unit  50  may be mounted to the mount  27  and/or slideably mounted on the two guide rods. Cutting unit  50  preferably includes a motor housing  68  in which is mounted an electric motor (not shown), guide rod support housing  110  in which are slideably mounted the two guide rods, and a blade guard  112  which surrounds a cutting blade  124  which is mounted on an output spindle (not shown) of the motor. The mount  27  can pivot about a horizontal axis on the rotatable table to enable the saw to perform bevel cuts. The rods can pivot on the mount about a horizontal axis to move the two rods and the cutting unit  50  vertically away from or towards the rotatable table  100  and extension arm  106  to enable the saw to perform chop cuts. A spring (not shown) preferably biases the mount  27  and guide rods to their highest position. 
         [0016]    A handle  114  may be attached to the front of the cutting unit  50  by which a user moves the cutting unit  50  towards or away from the rotatable table  100  and extension arm  106 . The mount  27  preferably locks in automatically its uppermost pivotal position by a latch mechanism (not shown). A pivotal lever  116  may be mounted on the handle  114  by which an operator can release the latch mechanism. A switch  118  is preferably mounted on the handle  114 , the depression of which activates the electric motor. 
         [0017]    A fixed fence  16  is preferably 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. 
         [0018]    Referring to  FIGS. 2 to 4 , the fixed fence  16  may comprise two side portions  126 , having flat faces  18 , the planes of which are flush (i.e., co-planar) with each other. Side portions  126  may be attached to the platforms  12  and extend towards and partly over the rotatable table  100 . Side portions  126  may be connected by a semi-circular portion  128  in well-known manner. The side portions  126  and semi-circular portion  128  are preferably manufactured in a one piece construction. 
         [0019]    When the fixed fence  16  is mounted on the platforms  12 , the vertical axis of rotation of the rotatable table  100  is preferably located in the plane of the faces  18  of the side portions  126 . The center of the semi-circular portion  128  preferably aligns with the vertical axis of the rotatable table  100 . 
         [0020]    A threaded aperture  150  is preferably formed in the top of each platform  12 . An aperture  152  may be formed through the rear of each side portion  126 . When the fixed fence  16  is mounted on the platforms  12 , each of the two apertures  152  preferably aligns with a threaded aperture  150 . A threaded bolt  154  is preferably passed through each of the two apertures  152  and screwed into a threaded aperture  150  to secure the fixed fence  16  to the base  6 . 
         [0021]    During the use of the saw, a work piece is placed on the work surface  102 ,  104  and is placed against the flush surfaces of the side portions  126  of the fixed fence. After activating the motor to rotate the cutting blade  124 , the cutting unit  50  is pivoted towards the work piece to engage the rotating cutting blade  124  with the work piece. As the cutting blade  124  cuts the work piece, it presses the work piece against the fixed fence  16  in a direction perpendicular to the plane of the flush surfaces of the side portions  126  of the fixed fence  16 . The work piece in turn applies a force against the fixed fence  16  in the same direction. The cutting blade  124  cuts the work piece while it is pressed against the fixed fence  16 . 
         [0022]    The first embodiment of the present invention will now be described. An elongate rib  160  is preferably formed on the rear of each platform  12 . Rib  160  preferably extends vertically upwards from the top surfaces  104  of the platforms  12  at the rear of the platforms  12 . When the fixed fence  16  is mounted on the base, the ribs  160  locate against the rear wall  164  of the side portions  126  to locate the fence  16  in the correct position and prevent rearward movement while the fixed fence  16  is being attached to the base  6  and provide additional support against rearward movement of the fence  16  when the fixed fence  16  is being used. 
         [0023]    A second embodiment of the present invention will now be described with reference to  FIG. 5 . Where the same features are present in the second embodiment which were present in the first embodiment, the same reference numbers have been used. The second embodiment comprises elongate ribs  160  which are of the same design as in the first embodiment. Additionally, a recess  162  is preferably formed in each of the rear walls of the side portions  126  of the fixed fence  16 . This recess  162  is preferably open rearwardly (direction A, parallel to the work surface) as well as downwardly (direction B, perpendicularly to the work surface). 
         [0024]    Preferably the size of the recesses  162  correspond to the size of the ribs  160 . When the fixed fence  16  is mounted on the base  6 , the ribs  160  locate in and engage with the recesses  162  to locate the fixed fence  16  in the correct position while it is being assembled and provide additional support against rearward movement when the fixed fence  16  is being used. As the recesses  162  are preferably open rearwardly, the fixed fence  16  can be moved forward slightly during assembly to accommodate manufacturing tolerances. 
         [0025]    It will be appreciated by a person skilled in the art that the recesses  162  can be replaced with grooves which only open downwardly. 
         [0026]    A third embodiment of the present invention will now be described with reference to  FIGS. 6 to 8 . Where the same features are present in the second embodiment which were present in the first embodiment, the same reference numbers have been used. 
         [0027]    The difference between the third embodiment and the first embodiment is basically the design of the bolts  154  and the apertures  152  formed through the rear of each side portion  126  of the fixed fence  16 . Preferably each bolt comprises a tapered head  300  which is attached to a threaded body  302 . The tapered head  300  comprises an angled side wall  304 . Each aperture  152  comprises a frusto-conical entrance  306  connected to a tubular section  308 . The frusto conical entrance  306  comprises an angled wall  310 . The dimensions of the angled wall  304  of the tapered head  300  and the angled wall  310  of the frusto-conical entrance  306  are substantially the same. When the fence  16  is attached to the base  6 , the threaded body  302  of the bolt  154  is passed through the aperture  152  to threadedly engage the threaded aperture  150 . The bolt  154  is then rotated, resulting the threaded body  302  of the bolt  154  screwing into the threaded aperture  150 , the bolt  154  moving in the direction of Arrow P as it does so. As the bolt  154  screws into the threaded aperture  150 , the angled side wall  304  of the tapered head  300  engages with the angled wall  310  of the frusto-conical entrance  306 . As the bolt  154  continues to screw into the threaded aperture  150 , the angled side wall  304  of the tapered head  300  and the angled wall  310  of the frusto-conical entrance  306  act as a cam and cam follower and slide along each other in order to move into alignment to allow the bolt  154  to continue to move in the direction of Arrow P. As the angled side wall  304  of the tapered head  300  aligns with the angled wall  310  of the frusto-conical entrance  306 , the side portion  126  of the fixed fence  16  is urged in the direction of Arrow Q into engagement with the rib  160 . As the bolt  154  is tightened, the side portion  126  of the fixed fence  16  is pushed against rib  160 . When the bolt  154  is screwed to its maximum amount into the threaded aperture  150 , the side portion  126  of the fixed fence  16  is held firmly against the rib  160 . 
         [0028]    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 which uses a fixed fence to support a work piece on a base such as a chop saw, a bevel saw, a table saw, a band saw, a slide saw or a radial arm saw.