Abstract:
An improved riving knife/guard assembly for a table saw allows the guard to be removed and attached without the use of any tools, provides a clear view of the work zone, blade and workpiece, and is easily adjustable to accommodate different size workpieces and cutting angle. The assembly includes a riving knife extending upward from the table substantially coplanar with the saw blade and a guard that releasably attaches to the riving knife with a rotatable latch with the guard at least partially surrounding the saw blade.

Description:
BACKGROUND  
       [0001]     Typical table saws include a base or frame having a flat table top or supporting a flat table top. The table top generally includes a slot through which a cutting member, such as a circular saw, protrudes above the table top. Often, a riving knife, or splitter, is mounted directly in-line with the saw blade. The riving knife operates to keep separate the two portions of the workpiece that have been cut to prevent the workpiece from binding on the saw blade, which reduces the possibility of workpiece kickback. Many table saws also include a guard to protect the operator from potentially serious injury caused by accidental contact with the saw blade. The guard is located to prevent the operator from contacting the saw blade while in use.  
         [0002]     Many types of riving knives and guard assemblies have been used in the past. However, these assemblies have often been difficult to use because they are typically flimsy or obstruct the operator&#39;s view of the workpiece with respect to the saw blade, or reference marks or scales used to align the workpiece. As a result, many users operate the table saw with the guard and the riving knife removed. This results in a higher probability of accidents and injuries that may occur due to accidental user contact with the rotating saw blade. Additionally, the removal and replacement of the guard and the riving knife often requires the use of tools and multiple procedural steps that make the process complicated and difficult, such that the user often removes these components for a specific project and never replaces them.  
         [0003]     Accordingly, it is desired to provide a guard and a riving knife that protect the user from accidentally contacting the rotating saw blade during operation, while providing the user with a sufficient viewing area of the zone of contact between the workpiece and the saw blade. If the user can view the saw blade and the workpiece with the guard installed, the user may not be motivated to operate the table saw with the guard removed.  
         [0004]     Additionally, it is desired to provide a guard that is easily removable and replaceable on the riving knife so that the user will replace the guard on the riving knife after it has been removed, rather than continue to operate the table saw without the guard.  
       BRIEF SUMMARY  
       [0005]     A table saw is provided that includes a table with an aperture to receive a portion of a rotatable saw blade extending from below the table and a riving knife that extends through the aperture from below the table.  
         [0006]     The table saw may have a top guard attached to the riving knife with a latch. The riving knife includes a slot and a tongue and the top guard is provided with a retention pin and a latch to respectively engage the slot and the tongue. The retention pin is inserted into the slot in the riving knife and a first portion of the latch is rotated until it engages the tongue and second portion of the latch is rotated in the opposite direction to place the first portion in tension.  
         [0007]     Advantages of the present invention will become more apparent to those skilled in the art from the following description of the preferred embodiments of the invention that have been shown and described by way of illustration. As will be realized, the invention is capable of other and different embodiments, and its details are capable of modification in various respects. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The features and advantages of the present invention may be better understood by reference to the accompanying drawings in which like reference numerals refer to like elements.  
         [0009]      FIG. 1  is a perspective view of a table saw incorporating a riving knife/guard assembly according to the present invention.  
         [0010]      FIG. 2  is a side view of a riving knife/guard assembly.  
         [0011]      FIG. 3  is a cross-sectional view of the connection between the top guard and the riving knife.  
         [0012]      FIG. 4  is top perspective view of the top guard.  
         [0013]      FIG. 5  is a bottom perspective view of the top guard.  
         [0014]      FIG. 6  is a top view of the top guard.  
         [0015]      FIG. 7  is a perspective view of the latch.  
         [0016]      FIG. 8  is a side view of the riving knife.  
         [0017]      FIG. 9  is a perspective view of the riving knife/guard assembly showing a side guard rotated away from contact with the table surface. 
     
    
     DETAILED DESCRIPTION  
       [0018]     While this invention is susceptible of several different embodiments, this specification and the accompanying drawings disclose only some specific forms as examples of the invention. The invention is not intended to be limited by the descriptions in this specification or the drawings. Instead, the scope of the invention is provided in the claims.  
         [0019]     Turning now to  FIGS. 1-9 , a table saw  10  having one embodiment of the inventive riving knife/guard assembly  20  is provided. The table saw  10  includes a table top  12  with a top surface  13 . The table top  12  includes a slot  14 , or aperture, that extends through the table  12 . A saw blade  16  is conventionally mounted to a motor and carriage (both not shown) that is located under the table top  12 . A portion of the saw blade  16  protrudes through the slot  14 . The portion of the saw blade  16  that protrudes through the slot  14  is the operative portion for cutting a workpiece (not shown). The knife/guard assembly  20  includes a riving knife  30 , a top guard  50 , and a latch  90  to removeably attach the top guard  50  to the riving knife  30 .  
         [0020]     The riving knife  30  extends upward from the top surface  13  of the table saw. The riving knife  30  may be mounted to the table saw  10 . For example, the riving knife  30  may be mounted to the carriage (not shown) under the table top  12  in such a manner so that it is centered behind or aligned with the saw blade  16 . In some embodiments, the riving knife  30  may be mounted for movement in conjunction with the saw blade  16 .  
         [0021]     The riving knife  30  operates to keep the cut portion of the workpiece (not shown) split or separated after it is cut and as the remainder of the workpiece is fed through the saw blade  16 . Splitting or keeping the cut portions of the workpiece separated helps to prevent potential binding of the saw blade  16  and the workpiece during operation. The spacing of the riving knife  30  from the saw blade  16  may range from about 3 mm (0.12 inches) to 8 mm (0.31 inches) to reduce the possibility for binding and kickback.  
         [0022]     A top guard  50  as explained in detail below is attached to the riving knife  30 . Preferably, the top guard  50  is attached to an upper portion of the riving knife  30  so that the workpiece does not contact the top guard  50 . The top guard  50  is formed with a first finger  52  and a second finger  54  that each extend forwardly from the point of contact between the top guard  50  and the riving knife  30 . The two fingers  52 ,  54  are sized to extend past the front edge  17  of the saw blade  16 . Thus, the two fingers  52 ,  54  provide protection from the user contacting the saw blade  16  from above the saw blade  16 . The two fingers  52 ,  54  are spaced from each other to form a gap  53  (best shown in  FIG. 6 ) that provides a view of the saw blade  16  and the workpiece as it is moved toward and makes contact with the saw blade  16 . The gap  53  provides the user with a suitable view of alignment markings (not shown) on the workpiece to allow the user to precisely cut the workpiece with the saw blade  16 .  
         [0023]     The fingers  52 ,  54  may have interior chamfered edges  55  along a portion of their length. The chamfered edges  55  increase the view of the cutting zone, as well as the blade  16  and workpiece, when these are viewed at an oblique angle, while maximizing the distance from the blade  16  to the operator, and minimizing the width of the gap  53 .  
         [0024]     The top guard  50  may also include a side guard  70  that is pivotably mounted to the top guard  50 . The side guard  70  normally contacts the workpiece yet allows the workpiece to move into the cutting zone while providing a protective surface that surrounds the front and the sides of the exposed portion of the saw blade  16 . As best seen in  FIG. 9 , the side guard  70  has two side pieces  72  and  74  that extend beyond the fingers  52 ,  54  of the top guard  50 . The side pieces  72 ,  74  provide protection from the saw blade  16  both before and after the workpiece is cut. Likewise, the side guard  70  has a front portion  76  that contacts an operator&#39;s hands or fingers that are on top of the workpiece as it is fed to be cut, thus providing a tactile warning that the operator&#39;s hands or fingers may be near the saw blade  16 . The side guard  70  is designed not to interfere with measuring, aligning, or setting up the workpiece due to its pivotal mounting.  
         [0025]     In some embodiments, the side guard  70  is provided with a sensing apparatus that provides an audible or visual signal when the user contacts the side guard  70  when the saw blade  16  is rotating. The audible signal can be a bell or an alarm, the visual signal can be a warning light. In other embodiments, the saw blade  16  could stop rotating when the user contacts the side guard  70 . This sensing mechanism could be activated based on a change in capacitance sensed by the side guard  70  or by another type of sensing means that is known to those of ordinary skill in the art.  
         [0026]     Each of the sides  72 ,  74  of the side guard  70  can be independently lifted and rotated onto a pair of stops  62 ,  63  located on either side of the top guard  50 , as best seen in  FIG. 4 . The top guard  50  remains in place when the side guard  70  is rotated into a raised position ( FIG. 9 ) from its lowered position, where it rests on the table surface  12 , or on a surface of the workpiece if present on the table top  12 . The formation of a two-piece side guard allows a further range of potential tilt of the saw blade  16  with respect to the table surface  12  without requiring the side guard  70  to be removed. Similarly, the side guard  70  with discrete side pieces  72 ,  74  can be used with a workpiece that does not have a flat surface that is parallel to the table surface  12 . Because of the convenience of this side guard  70  design, the user is less likely to remove the side guard  70  from the top guard  50 . Additionally, the side guard  70  provides additional protection to the user because a greater amount of the side and front surfaces of the saw blade are enclosed by the side guard  70  during angled cuts (or when cutting workpieces with angled surfaces) than would be available with a side guard having arms that are attached together on either side of the saw blade  16 .  
         [0027]     In one embodiment, the riving knife  30  is formed from a flat plate that extends through the slot  14  in the table top  12 . The riving knife  30  is movably mounted to the table saw  10 . The riving knife  30  is formed to maintain separation between the two portions of the workpiece after the workpiece is cut by the saw blade  16 . The forward edge  32  of the riving knife  30  is formed to be concave with a radius slightly larger than the radius of the saw blade  16 . This shape allows the forward edge  32  of the riving knife  30  to substantially surround the rear edge  19  of the saw blade  16  while the saw blade  16  is rotating to provide protection for the user against accidental contact between the user and the rear edge  19  of the saw blade  16 .  
         [0028]     As best shown in  FIG. 8 , the riving knife  30  includes a top edge  34 . The top edge  34  of the riving knife  30  includes a first slot  38  near the forward most point of the riving knife  30  and a rear slot  36  near the rearward most point of the riving knife  30 . The first slot  38  is preferably formed with a hook or a dogleg shape that extends downward from the top edge  34  and a cavity  38   a  extending rearwardly within the riving knife  30 . The top edge  34  forms a tongue  39  that is above the cavity  38   a  of the first slot  38 . The second slot  36  is formed with substantially the same shape as the first slot  38  although it is oriented in the opposite direction from the first slot  38 . The second slot  36  includes a first portion  36   a  that extends downward from the top edge  34  of the riving knife  30  and a second cavity  36   b  that extends forwardly within the riving knife  30  and substantially perpendicular to the first portion  36   a.    
         [0029]     The top guard  50  is best seen in  FIGS. 4-7 . The top guard  50  includes a first arm  52  and a second arm  54  that each extend above the saw blade  16  when the top guard  50  is attached to the riving knife  30 . The arms  52 ,  54  extend from the riving knife  30  forward the front edge  17  portion of the saw blade  16 . The arms  52 ,  54  are separated from each other to define a gap  53  to allow the user to view the rotating saw blade  16  and its contact with a workpiece when presented to the front edge  17  of the saw blade  16 . The top guard  50  includes a forward cavity  56  and a rear cavity  60  rearward of the first and second fingers  52 ,  54 . The forward and rear cavities  56 ,  60  receive and retain the components of the latch  90 , which are discussed in detail below. In addition to the components of the latch  90 , the rear cavity  60  includes apertures to accept a pin  68 . The pin  68  may be positioned and retained within the second cavity  36   b  of the rear slot  36  in the riving knife  30  when attaching the top guard  50  to the riving knife  30 .  
         [0030]     The top guard  50  additionally includes two stops, a right stop  62  and a left stop  63 . As best seen in  FIG. 4 , the right stop  62  extends outwardly from a right surface  50   a  of the fork and the left stop  63  extends outwardly from a left surface  50   b . The stops  62 ,  63  may each include a beveled surface  62   a ,  63   a , respectively. Each of the beveled surfaces  62   a ,  63   a  limit the potential range of rotation of the two side guards  72 ,  74  (discussed above).  
         [0031]     The top guard  50  further includes apertures  67  that extend blindly into the side surfaces  50   a ,  50   b  of the top guard  50  and that accept pins, or other similar fasteners that are known to those of skill in the art, to attach the right side piece  72  of the side guard  70  to the right side surface  50   a  and the left side piece  74  of the side guard  70  to the left side surface  50   b  of the top guard  50 . Preferably, the apertures  67  are formed forward of the right and left stops  62 ,  63 , in a position to allow the side pieces  72 ,  74  to rotate to a position where they do not contact the workpiece when it contacts the saw blade  16  but also to avoid contacting the workpiece after it has passed beyond the riving knife  30 .  
         [0032]     The top guard  50  includes a projection  65  that extends rearwardly into the rear cavity  60 . The projection  65  includes holes that blindly extend through the projection  65  and the side surfaces  50   a ,  50   b  to accept a pin  97  that extends through the locking member  96 , to rotatably connect the latch  90  to the top guard  50 . Alternatively, the latch  90  can be rotatably connected to the top guard  50  by other methods that are understood by those of ordinary skill in the art.  
         [0033]     As best shown in  FIG. 5 , the bottom surface  50   d  of the top guard  50  preferably includes a groove  69  that accepts the top edge  34  of the riving knife  30  when the top guard  50  is positioned on the riving knife  30 .  
         [0034]     Referring now to  FIGS. 3 and 7 , the latch  90  includes a swinging member  92  and a locking member  96 . The swinging member  92  is rotatably connected to the locking member  96  with a pin  98  that is inserted into holes formed within the locking member  96  and holes formed at a first end  93 , or proximal end, of the swinging member  92 . The second end  94 , or distal end, of the swinging member  92  is formed with a hook  95 , or a curve. The hook  95  has an inner radius slightly larger than the radius of a distal end of the tongue  39  on the top edge  34  of the riving knife  30 . The swinging member  92  is formed with a curved surface along the length of the swinging member  92 . Specifically, the swinging member  92  is formed so that its top surface  92   a  is convex when viewed from the top of the top guard  50  (with the latch  90  connected to the top guard  50 ).  
         [0035]     A locking member  96  is additionally provided on the latch  90 . The locking member  96  is rotatably connected to the projection  65  in the top guard  50  with a pin  97  that extends through a first end of the locking member  96  as discussed above and forms a rotational axis  97   a  with respect to the top guard  50 . The locking member  96  is also rotatably connected to the swinging member  92  to allow the swinging member  92  to engage the tongue  39  on the top edge  34  of the riving knife  30  about a second rotational axis  98   a  through the pin  98 . After the swinging member  92  engages the tongue  39 , the locking member  96  may be rotated in the opposite direction, until the locking member  96  contacts the bottom surface  60   a  of the second cavity  60  of the top guard  50 . In this position an imaginary line, or axis,  92   b  through a proximal end  93  of the swinging member  92  and the hook  94 , or distal end, of the swinging member  92  is substantially in-line with a longitudinal axis  96   b  of the locking member  96 . This position of the locking member  96  places the swinging member  92  in tension and retains the engagement between the top guard  50  and the riving knife  30 .  
         [0036]     As can be understood by those of ordinary skill in the art, in other embodiments, the longitudinal axes  92   b ,  96   b  of each of the swinging member and the locking member  92 ,  96  may be at a pre-defined angle A with respect to each other when the locking member  96  contacts the bottom surface  60   a  of the second cavity  60  of the top guard  50  to retain the engagement between the swinging member  92  and the riving knife  30 . In some embodiments, the pre-defined angle A may be oblique, and in other embodiments the pre-defined angle A may be zero degrees, such that the axes  92   b ,  96   b  are substantially parallel with each other. In still other embodiments, the locking member  96  may retain the swinging member  92  in position on the riving knife  30 , with the locking member not contacting the bottom surface  60   a  of the second cavity  60  of the top guard.  
         [0037]     A handle  99  extends from an end of the locking member  96  at an oblique angle and provides a surface that the user may hold to rotate the locking member  96  out of the second cavity  60 . Rotation of the locking member  96  removes the tension in the swinging member  92  and allows it to be disengaged from the tongue  39 . When the swinging member  92  is disengaged from the tongue  39 , the top guard  50  can be slid rearwardly with respect to the riving knife  30  to allow the pin  68  to be removed from the second slot  36  in the riving knife  30 , which allows the top guard  50  to be removed from the riving knife  30 .  
         [0038]     The foregoing disclosure is the best mode devised by the inventors for practicing this invention. It is apparent, however, that apparatus incorporating modifications and variations will be obvious to one skilled in the art. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include aforementioned obvious variations and be limited only by the spirit and scope of the following claims.  
         [0039]     It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.