Abstract:
A power miter saw comprising a base having a center portion configured to support a rotatable table and side portions on opposite sides of the center portion, the side portions having a flat working surface for supporting a work piece, a table rotatably connected to the saw base and having a zero miter angle position, a saw blade and motor assembly operatively connected to the table, the fence positioning surfaces being configured to accurately position a fence assembly relative to the table, a fence assembly extending between the base side portions having a front vertical contacting surface and an opposite rear surface, each of the base side portions having a generally vertical fence positioning surface extending downwardly substantially perpendicularly from the flat working surfaces, and a securing mechanism for applying a substantially horizontal holding force for holding the fence assembly securely to the vertical fence positioning surfaces.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention is generally related to power miter saws. 
         [0002]    The attachment method for a fence on all known miter saws is generally the same. Such known fence systems are attached to the saw from the top. The fence bolts drop through holes on the fence and thread into holes in the base. With few known exceptions, the fence sits on the same surface that holds the work piece during cutting. 
         [0003]    The majority of miter saws rely on limited movement of the fence to make it square to the blade. While this system is simple, it poses several problems. First, the fence is allowed to move left to right, front to back, and rotate about a vertical axis. All that is truly needed to bring the fence square to the blade is the rotation about a vertical axis. The extra movement makes adjustment difficult. To square the saw, the user is required to hold a square against the moving fence while positioning it in three directions, making a simple task very difficult. Second, the fence can easily go out of square when the bolts are tightened. As the bolt begins to grab the fence, the fence will begin to rotate with the bolt. The user must prevent the fence from moving while tightening the bolts. A third problem relates to the addition of a sacrificial fence. Many users will add a sacrificial fence to the front of the fence provided with the miter saw. A sacrificial fence usually consists of a custom cut piece of wood about ¾″ thick. Because this piece bolts on to the front of the fence provided with the tool, the capacity of the tool is reduced. 
       SUMMARY OF THE INVENTION 
       [0004]    A power miter saw comprising a base having a center portion configured to support a rotatable table and side portions on opposite sides of the center portion, the side portions having a flat working surface for supporting a work piece, a table rotatably connected to the saw base and having a zero miter angle position, a saw blade and motor assembly operatively connected to the table, the fence positioning surfaces being configured to accurately position a fence assembly relative to the table, a fence assembly extending between the base side portions having a front vertical contacting surface and an opposite rear surface, each of the base side portions having a generally vertical fence positioning surface extending downwardly substantially perpendicularly from the flat working surfaces and being coplanar with one another and perpendicular to the plane of the blade when the table is in the zero miter position, and a securing mechanism for applying a substantially horizontal holding force for holding the fence assembly securely to the vertical fence positioning surfaces. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a left front perspective view of a power miter saw embodying the present invention; 
           [0006]      FIG. 2  is a right front perspective of the base and fence assembly of a power miter saw embodying the present invention; 
           [0007]      FIG. 3  is left rear exploded perspective of the base and fence assembly of the power miter saw shown in  FIG. 2 ; 
           [0008]      FIG. 4  is a left plan view, partially in section, of the base and fence assembly shown in  FIGS. 2 and 3 ; 
           [0009]      FIG. 5  is a rear perspective of an embodiment of a portion of a fence assembly shown in  FIGS. 2 ,  3  and  4 ; 
           [0010]      FIG. 6  is cross section of the portion shown in  FIG. 5 , with a bolt and spherical washer set attached thereto; 
           [0011]      FIG. 7  is a rear perspective of an alternative embodiment of a portion of a fence assembly shown in  FIG. 5 ; 
           [0012]      FIG. 8  is a right plan view, partially in section, of the base and the alternative fence assembly shown in  FIG. 7 , shown with the fence in an unlocked position; 
           [0013]      FIG. 9  is a right plan view, partially in section, of the base and the alternative fence assembly shown in  FIG. 7 , shown with the fence in a locked position; and 
           [0014]      FIG. 10  is left rear perspective of the base of the power miter saw similar to  FIG. 2 , illustrating a sacrificial fence attached to the base rather than a supplied fence. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Embodiments of the rear mounted miter saw fence of the present invention attach to the rear of the miter saw base instead of the top surface. There are several advantages to this configuration including easier installation, better clamping to the base, and the ability to add a sacrificial fence without reducing the capacity of the saw. 
         [0016]    Various embodiments of the rear mounted miter saw fence address all of these issues. The new fence embodiments do not attach to the base of the miter saw with vertically oriented bolts. Instead, the bolts are oriented in a horizontal direction. The bolts are inserted through horizontal holes in the back of the fence and thread into holes in the rear of the base. When the bolts are tightened, the face of the fence is tightened against the rear of the base. 
         [0017]    With the rear mounted fence, squaring the blade to the fence is an easy task, because the fence is not moved during adjustment. The rear mounted fence necessitates a system where the miter detents move. This type of system only allows rotation of the detents about a vertical axis. 
         [0018]    When the bolts are tightened on the rear mounted fence, the face of the fence is pressed against the rear of the base. Two critical alignment surfaces are perpendicular to the axis of the bolts as opposed to parallel as in all known fence designs. A small horizontal surface on the base helps to align the fence horizontally. Directly behind the horizontal surface is an inclined surface which significantly reduces the amount of required machining. This arrangement eliminates alignment issues caused by tightening the bolts. As long as the bolts are tight, the critical alignment surfaces will be in contact. 
         [0019]    The rear mounted fence eliminates the capacity reduction caused by the addition of a sacrificial fence. Embodiments of the present invention allow for a sacrificial fence to be attached using the same method as current miter saw fence designs. However, an improved embodiment is available to the user. Instead of attaching the sacrificial fence to the front of the fence provided with the tool, a sacrificial fence can be installed in place of the provided fence. To do this, a piece of preferably ¾″ thick wood (preferably plywood) is cut to a shape similar to the provided fence. The provided fences are removed from the saw. The sacrificial fence is then bolted onto the base in the same manner as the provided fence. Because the fence is not adjusted to square the blade and it will always install in the same position and therefore the removal of the provided fence causes no hardship for the user. 
         [0020]    Turning now to the drawings and particularly  FIG. 1 , a miter saw, indicated generally at  10 , is shown and comprises a base, indicated generally at  12 , on which a table indicated generally at  14  is rotatably connected and which has a front miter control arm  16  which is used by an operator to adjust the horizontal miter angle and to lock the angle in the desired position. The saw  10  includes a fence assembly, indicated generally at  18 , as well as a rear hub  20  which includes a horizontal pivot shaft (not shown) on which a vertical stand  22  is attached. The saw includes a motor and blade assembly, indicated generally at  24 , is pivotable around a horizontal pivot shaft so that the operator can grasp a handle  26  and lower the blade into cutting relationship with a work piece (not shown) that is positioned on the table and portions of the base for cutting. The horizontal shaft enables bevel angles to be cut in the work piece. 
         [0021]    The rotatable table  14  has a top surface  28  which has a slot  30  coextensive with the plane of the blade and is provided so that the blade can have a downward reach below the top surface  28  to be able to cut completely through a work piece that is being cut. The base  12  has side portions indicated generally at  34 , each of which has a top surface  36 . It is preferred that the plane of the top surfaces  36  of the side portions  34  be coextensive with the plane of the top surface  28  of the table so that a flat work piece will be supported by all three components when positioned for cutting. 
         [0022]    As best shown in  FIG. 2 , the fence assemblies  18  are connected to the side portions  34  and include a stationary fence portion  38  as well as a removable fence portion  40  that can be slideably positioned relative to the stationary portion  38  to accommodate various types of miter and bevel cuts. In this regard, each of the slideable portions has a reduced height portion  42  that transitions along an incline  44  to a maximum height portion  46 . This configuration is provided to enable the saw to be usable at maximum miter and bevel angles without the plate and motor assembly interfering with the fence assemblies  18  during operation. 
         [0023]    The removable fences  40  can be slidably adjusted to accommodate the particular angle that a work piece is being cut while providing the necessary support for positioning the work piece during cutting. It is a common practice to have sacrificial fences for providing support generally continuously between the two fence assembles, the only gap being that which is cut by the blade during operation. Such sacrificial fences are typically used by cutting an appropriate board or piece of plywood and attaching it to a fence assembly, such as fence assemblies  18  shown in  FIG. 2 , with apertures  48  being provided for such purpose. However, as previously indicated, when a sacrificial fence is placed in front of the fence portions  38  and  40 , the thickness of the fence reduces the effective area for supporting the work piece on the top surface  28  of the table and top surface  36  on the side portions  34 . This also reduces the effective length of cuts that can be accomplished by the blade and motor assembly  24 . 
         [0024]    The adjustment of the removable fence  40  on the stationary fence  38  is shown and described in copending application Ser. No. 12/220,347 entitled AN ADJUSTABLE FENCE ASSEMBLY FOR A MITER SAW, filed Jul. 24, 2008 which is incorporated by reference herein. 
         [0025]    As is apparent from the exploded respective view of the base  12  and fence assemblies  18  shown in  FIG. 3 , the fence assemblies are symmetrical in their construction and therefore identical numbers are used for each of the two fence assemblies, it being understood that they are generally mirror images of one another. The leftward stationary fence portion  38  is shown in  FIGS. 5 and 6  and has a rear surface  50  as well as a front surface  52 . The rear surface  50  has a rectangular lower extension  54  that is relatively thin as shown in  FIG. 6  and has a bottom surface  56  that is slightly angled to correspond to a mating surface on the base  12 . The stationary fence portion  38  has a pair of apertures  56  which extend through the entire width of the stationary fence portion as shown in  FIG. 6 . The preferred embodiment also includes an enlarged cylindrical recess  58  that is sized to receive a spherical washer set which comprises a concave washer  60  and a convex washer  62  which fit together as shown in  FIG. 6 . A bolt  64  has a head  66  with an internal hex configuration is also shown in  FIGS. 5 and 6 . When installed as shown in  FIG. 6 , the head  66  bears against the washer  62 . 
         [0026]    As shown in perspective in  FIG. 3 , the side portions  34  have a vertical fence locating surface  70  that includes a pair of apertures  72  that are threaded and sized to receive bolts  64  for mounting the fence assemblies  18  and particularly the stationary fence portion  38  to the side portions  34  of the base  12 . The side portions also have a horizontal narrow surface  74  which then merges with a downwardly inclined surface  76 . The narrow horizontal surface  74  is provided to engage a bottom surface  78  of the front of the stationary fence portion  38  (see  FIGS. 4 and 5 ) to properly position the same horizontally when the fence assemblies  18  are mounted to the side portions  34 . 
         [0027]    As previously mentioned, the downwardly inclined surface  76  is provided so that it need not be machined to a high tolerance because it is essentially out of contact when the fence assemblies  18  are installed. However, the narrow horizontal surface  74  is relatively small in area and can be easily machined to accurately position the stationary fence portion and enable convenient insertion of the bolt  64  in the aperture  72 . 
         [0028]    While the preferred embodiment has a narrow horizontal locating surface  74 , it should be understood that other embodiments may not have such a horizontal surface and in fact may have a space or a gap between the bottom of the stationary fence portion and adjacent surface such as the surface  74  and that the vertical positioning of the stationary fence would be determined by the placement of the apertures and use of the bolts to bring the front face  52  of the stationary fence portion  38  into contact with the vertical fence locating surface  70  which is machined to a close tolerance. Also, while the bolts  64  are shown to have an internal hexagonal configuration, other configurations may be employed, such as an external hex head or other configuration. It should also be understood that regular washers  80 , as shown in  FIG. 3  may be used. 
         [0029]    While the embodiments shown in  FIGS. 1-5  have apertures  56  and  58  for receiving bolts  64 , an alternative embodiment may be used and is shown in  FIGS. 7 ,  8  and  9  wherein the stationary fence portion  38 ′ has a pair of slots  82  that extend from the location of an aperture  56  downwardly to the bottom surface  78  of the front of the stationary fence portion  38 ′. This configuration may utilize a cam lock bolt, indicated generally at  84 , to hold the stationary fence portion to the side portions  34 . The cam lock bolt  84  has a threaded shank  86  that engages the threaded openings  72  in the vertical fence locating surface  70  and has a cam lever  88  that can bear against the rear surface  50  to tighten the stationary fence to the side portions  34 . In this regard, the cam lever  88  is shown in its untightened position in  FIG. 8  where the front face  52  of the stationary fence portion  38 ′ is out of contact with the vertical fence locating surface  70 .  FIG. 9  shows the lever  88  in its locked position. 
         [0030]    The sacrificial fence  90  is shown in  FIG. 10  and is preferably made of wood, plywood or the like and is cut to have a lower rectangular extension  54 ′ that is similar to the shape of the stationary fence portions  38  and is provided with apertures so that bolt  64  can secure the fence  90  to the side portions  34 . 
         [0031]    While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
         [0032]    Various features of the invention are set forth in the following claims.