Abstract:
Embodiments of the invention comprise an adjustable fence assembly for use with a power tool, that further comprise an elongated lower fence for attachment to the power tool, the lower fence having a base with an upper support and locking surface configuration extending along a substantial portion of the length of the base and a vertical front face for positioning a work piece, an elongated upper fence having a bottom surface configuration for engaging the surface configuration of the lower fence, the upper fence being releasably attached to the lower fence and adjustable relative to the lower fence along its lengthwise direction, the upper fence having a front face that is substantially coplanar with the front face of the lower fence when secured thereto, and a locking mechanism carried by the lower fence and operatively connected to the upper fence for selectively applying at least a downward force and a face biasing force for securing the upper fence to the lower fence in a manner whereby a coplanar relationship of the front faces of the upper and lower fence is substantially assured.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to miter saws, and more particularly to an adjustable fence assembly for a miter or similar saw. 
         [0002]    Most power miter saws that are presently being commercialized are capable of cutting work pieces at different miter angles as well as bevel angles. While all miter saws have a fence for positioning a work piece to be cut, the configuration of the fence can have various designs and capabilities. Since some miter saws have a bevel angle that can be adjusted from a straight cut to bevel angled cuts on one or both sides of vertical orientation, the design of the fence must be able to accommodate such capability. 
         [0003]    Many current miter saws also have a compound action whereby the blade and motor assembly can be physically moved relative to the table in a direction parallel with the plane of the blade, rather than just a pivoting or chop saw type of cutting action. With such compound motion, the blade and motor assembly will move from a rearward position to one forwardly of it either preparatory to the cut or during the cut. The fence must therefore be configured for these types of saws as well as saws that do not have compound motion capability to enable the blade and motor assembly to be operated through its range of motion without interference. It is also common place for current miter saws to have a lower fence on both sides of the blade. Because it is desirable to have a fence with some appreciable height, both regular and compound miter saws often have at least one upper upper fence that is attached on top a lower generally lower fence. The upper fence adds height to the lower fence and can also be adjusted to be closer to the blade for transverse cuts and can be moved away from the blade so that the blade and motor assembly can be adjusted for making miter angled cuts without interference with the upper fence. 
         [0004]    An important consideration is that the front face of the upper fence be coplanar with the front face of the lower fence to a high degree of accuracy when they are secured to one another and that they do not become out of square when the attachment mechanism is tightened. It is also important that the upper fence section be easily removed so that extreme compound angled cuts can be made that would otherwise not be possible. 
       SUMMARY OF THE INVENTION 
       [0005]    Embodiments of the invention comprise an adjustable fence assembly for use with a power tool, that further comprise an elongated lower fence for attachment to the power tool, the lower fence having a base with an upper support and locking surface configuration extending along a substantial portion of the length of the base and a vertical front face for positioning a work piece, an elongated upper fence having a bottom surface configuration for engaging the surface configuration of the lower fence, the upper fence being releasably attached to the lower fence and adjustable relative to the lower fence along its lengthwise direction, the upper fence having a front face that is substantially coplanar with the front face of the lower fence when secured thereto, and a locking mechanism carried by the lower fence and operatively connected to the upper fence for selectively applying at least a downward force and a face biasing force for securing the upper fence to the lower fence in a manner whereby a coplanar relationship of the front faces of the upper and lower fence is substantially assured. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a front left perspective view of a compound miter saw having an adjustable fence assembly embodying the present invention; 
           [0007]      FIG. 2  is a left rear perspective view of the compound miter saw shown in  FIG. 1 ; 
           [0008]      FIG. 3  is a left rear perspective view of a portion of the adjustable fence assembly illustrating the adjustable upper fence being shown in its outwardly extended position, and a cover plate in a position that prevents separation of the upper fence from the lower fence; 
           [0009]      FIG. 4  is a perspective view similar to  FIG. 3  but illustrating a cover plate in a position that permits removal of the upper fence from the lower fence; 
           [0010]      FIG. 5  is a perspective view similar to  FIG. 3  but illustrating the adjustable fence in its fully retracted position, with a cover plate in a position preventing separation of the upper fence from the lower fence; 
           [0011]      FIG. 6  is a cross section taken generally along the line  6 - 6  of  FIG. 5 ; 
           [0012]      FIG. 7  is a perspective view of the sleeve of the adjustable fence assembly and shown with a bolt in place; 
           [0013]      FIG. 8  is a perspective view of the sleeve shown in  FIG. 7 ; and 
           [0014]      FIG. 9  is a perspective view of the cover plate shown in connection with the adjustable fence assembly shown in its locking position and an attachment mechanism shown in section. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Embodiments of the present invention are particularly appropriate for use with power miter saws. However, it should be appreciated that the present invention may be used with non-powered miter saws or with other tools where a fence is used to position or guide the movement of a work piece in connection with cutting, shaping or other operation. 
         [0016]    While fence assemblies having adjustable upper fences that attach to a lower fence are used on many currently available miter saws, including compound miter saws, a frequent problem of such upper fences that are attached to a lower fence is that they tend to go out of square when the tightening mechanism is tightened too much or they are designed so that the upper fence cannot be quickly removed from the lower fence. Such removal is often required for making cuts at extreme compound angles. Embodiments of the present invention enable quick removal of a upper fence from a lower fence and also have the capability of firmly tightening the upper fence to the lower fence without causing the fences to go out of square relative to one another as a result of the tightening process. 
         [0017]    Turning now to the drawings, and particularly  FIGS. 1 and 2 , a miter saw, indicated generally at  10 , has a base  12  with a generally circular portion on which a rotatable table  14  is attached. A miter arm control assembly, indicated generally at  16 , is either integrally formed with the rotatable table  14  or is attached to it and is provided for adjusting the horizontal angular position of the table  14  for setting the miter angle for cutting a work piece that would be placed on the table  14 . 
         [0018]    A saw blade and motor assembly, indicated generally at  18 , is operatively connected to the table  14  by a linear guide mechanism, indicated generally at  20 . The saw blade and motor assembly  18  has an electric motor  22  that is operatively connected through a gear mechanism that drives a saw blade  26 , the gear mechanism not being shown but located within a housing portion  24 . The blade and motor assembly  18  is pivotable about a horizontal shaft  28 . A handle  30  is provided for use by an operator to bring the blade and motor assembly  18  from a rest position shown in  FIGS. 1 and 2  where it is elevated relative to the table to a lowered cutting position if a work piece is placed on the table  14 . 
         [0019]    The miter arm control assembly  16  has a slot  32  that extends across the table  14  and enables the blade  26  to be lowered to a position below the top surface of the table  14  so that the blade can cut completely through the work piece during a cutting operation. The linear guide mechanism  20  has a pivot head  34  to which the shaft  28  is mounted and the pivot head  34  is connected to a pair of rods  36  that are slidable in a support frame  38  to provide a compound miter type of operation. The support frame  38  has a bottom portion  40  that is attached to and is pivotable around a bevel pivot shaft  42  that is supported by a rear portion  44  of the table  14 . 
         [0020]    From the foregoing it should be understood that the support frame  38  which carries the linear guide mechanism  20  as well as the blade and motor assembly  18  will pivot around the bevel pivot shaft  42  for the purpose of orienting the blade  26  at the appropriate bevel angle for making bevel cuts on a work piece that may be placed on the table  14 . The saw shown in  FIGS. 1 and 2  is in a neutral position where vertical cuts are made. 
         [0021]    During operation, an operator places a work piece on the table  14 , brings the handle  30  down into cutting position after activating the motor  22  and makes a chop cut on the work piece. However, if the work piece to be cut is wide, the operator will typically use the handle  30  to pull the blade and motor assembly forwardly to some forward position where the work piece will be engaged, activated the motor and bring the handle down into a cutting position, and then push the handle  30  toward the work piece to cut it. 
         [0022]    An adjustable fence assembly, indicated generally at  50 , is provided to correctly position a work piece relative to the blade  26 . The fence  50  is shown to comprise a rightward stationary fence  52 , a lower fence  54 , and an adjustable and removable upper fence  56  that is attached to the lower fence  54 . As best shown in  FIG. 1 , the right stationary fence  52  is higher and its left end  58  is generally perpendicular or vertical relative to the table top surface  14 . The significance of this is that the illustrated miter saw is designed so that the miter saw has a single bevel operation as opposed to a dual bevel operation, meaning that the bevel angle can be adjusted only to the left as shown in  FIG. 1  from the normal or zero angle or position where the plane of the blade  26  is perpendicular to the plane of the top surface of the table  14 . 
         [0023]    It should be appreciated that if the saw  10  were a dual bevel operating saw, the right stationary fence  52  would likely be lower and may have an upper fence attached thereto and the angle of the end  58  would be slanted to the right as shown from the front view of  FIG. 1 . The fence assembly  50  is preferably designed so that the left and right stationary fences  52  and  54  are cast as a metal unit, with the two fences being interconnected by a curved bridge portion  60 . The bridge portion  60  has a front curved upper surface  62  that is designed to enable the blade and motor assembly to be moved rearwardly so that the blade  26  can cut through a work piece immediately forward of the fences without contacting the bridge portion  60 . 
         [0024]    The lower fence  54  has a front surface  64  and the upper fence  56  has a front face  66 . The front faces  64  and  66  are substantially coplanar to a high degree of accuracy so that the accuracy of cuts made with the saw is not compromised because of misalignment of the front faces  64  and  66 . 
         [0025]    As previously mentioned, the upper fence  56  can be adjusted and is designed be slidable relative to the lower fence  54  from the position shown in  FIGS. 1 and 2  where its right end  68  is close to the plane of the blade  26  but not interfering with it. The upper fence  56  can also be extended away from the blade a substantial distance as shown in  FIGS. 3 and 4 . The lower fence  54  has an angled inner end surface  70  which is designed to permit the linear guide mechanism  20  to rotate about the bevel pivot shaft  42  to make extreme bevel cuts without interference. 
         [0026]    The adjustable fence assembly  50  has a locking mechanism, indicated generally at  80 , which includes a locking lever  82  that can be manipulated to release the locking mechanism so that the upper fence  56  can be adjusted relative to the lower fence  54 . In this regard, the lever  82  is shown in an unlocked position in  FIGS. 1 and 2  and in a locked position in  FIGS. 3 ,  4 , and  5 . 
         [0027]    The locking mechanism  80  comprises the lever  82  and a hub structure  84  with a generally cylindrical inner chamber  86  that has a lower annular shelf  88  as well as an annular space  90  with an aperture  92  in which a cylindrical shank  94  of a bolt, indicated generally at  96 , is located. The bolt  96  has reverse threads  98  which engage complimentary threads  100  of the hub  84 . By using reverse threads, the lever  82  will be tightened when moved to the left as shown in  FIGS. 3 and 4  and will not be sticking out to possibly interfere with the operation of the saw. The lower fence  54  has a boss  102  that is generally cylindrically shaped and extends downwardly from a main portion  104  that is cast as a single piece, with a front wall  106  having the front surface  64 . 
         [0028]    The main portion  104  has an elongated channel defined by a rear face  108  of the front wall  106 , a facing wall  110  and a bottom shelf  112  that extends between the spaced walls  106  and  108 . The adjustable fence  56  has a front wall  114  with its front face  66 , the front wall  114  extending from a main portion  116  that has a recess defined by a vertical face  118  and a horizontal face  120  located near the front wall  114  and a second rear recess defined by a vertical face  122  and horizontal face  124 . The top surface  126  of the main portion  116  is slanted upwardly from the left to the right where it interfaces with the front wall  114 . 
         [0029]    The main portion  116  includes an elongated slot  128  which is sized and configured to receive a sleeve, indicated generally at  130 , which has a shank portion  132  that is slideable in the slot  128 . Referring to  FIGS. 7 and 8 , the sleeve has an enlarged generally rectangular top configuration that has an aperture  136  with sidewalls  138  that define a 12 point socket for receiving a hexagonal head  140  of the bolt  96  as best shown in  FIG. 7 . The shank  132  has curved opposite end portions  142  and flat sides  144 , the distance between which is only slightly less that the width of the slot  128  in the main portion  116  of the adjustable frame portion  56 . The shank  132  also fits within a similarly shaped opening in the boss  102 , which preferably has closer tolerances than in the slot  128  in the upper fence. This is designed so that the resistance to rotation of the sleeve  130  is provided by the lower fence structure. Also, by having the lower fence maintain the angular orientation of the sleeve  130 , the upper fence can be easily removed and replaced, inasmuch as the sleeve  130  will always be correctly angularly positioned relative to the slot  128 . As shown in  FIG. 8 , the aperture  136  has an annular shelf  146  which surrounds an aperture  148  which is sized to receive the cylindrical shank  94  of the bolt  96 . As shown in  FIG. 6 , the underside of the hex head  140  defines an annular flange  148  that contacts the annular shelf  146  of the sleeve  130 . A bottom surface  150  of the top portion  134  of the sleeve is also similarly angled as the top surface  126  of the main portion  116 . 
         [0030]    The boss  102  on the lower fence  54  has an annular shelf  152  that is in position to contact the shelf  88  of the lever  82 . Care is taken to assure that the annular shelves  88  and  152  are accurately formed or ground to be perpendicular to the true axis of the bolt  96 . Similarly, the annular shelf  146  and flange  148  are parallel to the shelves  88  and  152 . Therefore, when the lever  82  is rotated to pull the bolt  96  downwardly, the forces are applied in the direction of the axis of the bolt and this causes the head of the bolt to pull down on the sleeve  130  in a manner whereby there is a face biasing force tending to move the upper fence  56  to the right. 
         [0031]    Also, the bottom shelf  112  of the lower fence  54  is also formed or ground to be perpendicular to the front face  64  and the bottom surface  154  of the main portion  116  of the adjustable fence  56  is also accurately perpendicular to the front face  66  thereof. When the upper fence  56  is tightened in place, the bottom surface  154  is in contact with the bottom shelf  112  which correctly orients the front faces  64  and  66  so that they are coplanar to one another to a high degree of accuracy. This is achieved by virtue of the close tolerances between the rear face  108  of the front wall  106  of the lower fence  54  and the vertical face  118  of the main portion  116  of the upper adjustable fence  56 . 
         [0032]    Stated in other words, because the bolt  96  pulls the sleeve down and due to its angular orientation of the surface  150  that contacts the top surface  126 , a face biasing force is produced which causes the fence  56  to move forwardly so that the surfaces  108  and  118  are in close contact. 
         [0033]    When the lever  82  is placed in its unlocked position, the bolt  96  and sleeve  130  are free to move upwardly and a compression spring  156  is provided to urge the sleeve  130  upwardly so that the fence  56  is free to slide one way or another if desired. The sliding movement is possible because of the fact that the shank  132  of the sleeve can slide in the elongated slot  128  when the fence  56  is moved, as is evident from  FIGS. 3 ,  4 , and  5 . 
         [0034]    A desirable attribute of the adjustable fence assembly  50  is the fact that the upper adjustable fence  56  can be easily removed from the lower fence  54 . Also desirable is the fact that it cannot be removed without a conscious manipulation to do so. In this regard, the head  134  of the sleeve  130  is wider than the slot  128  and a cover plate, indicated generally at  160 , is preferably provided at the left end of the fence  56  as shown in  FIGS. 3 ,  4 , and  5 . The cover plate  160  has a flat central portion  162  of relatively small thickness that fits within a comparable recess  164  in the top surface  126  of the upper fence  54  so that the top surface of the flat central portion  162  is coextensive with the bulk of the surface  126 . The cover plate  160  also has a slot  166  that has a width substantially the same as the width of the slot  128 . Therefore, when the cover plate  160  is in locking position as shown in  FIG. 3 , the top portion  134  retains the fence  56  so that it cannot be vertically lifted from the fence  54 . 
         [0035]    The cover plate  160  is retained by a screw  168  that is secured to the fence  56  and also has a compression spring  170  provided between the underside of the head of the screw  168  and the cover plate  160  as best shown in  FIG. 9 . This provides a resilient holding force for the cover plate  160  and also provides a pivot point for about which the cover plate  160  can be rotated. The cover plate  160  also has a raised handle portion  172  which enables a user to easily grip the cover plate and rotate the same. When this is done and as shown in  FIG. 4 , the cover plate exposes a preferably rectangular opening  174  that is sized larger than the profile of the top portion  134  of the sleeve  130  thereby enabling the fence  56  to be pulled up and removed from the fence  54 . The cover plate  160  also has a downwardly directed tab  174  that fits into a hole  176  on the upper fence  56 . This prevents the cover plate  160  from moving due to vibration. To rotate the cover plate  160  so the upper fence  56  can be removed, the user must provide both a rotational force as well as a slight upward force to do so. 
         [0036]    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. 
         [0037]    Various features of the invention are set forth in the following claims.