Abstract:
A preferred embodiment of the present invention is directed to a modular saw guard system for a power saw of the type which has a table top, a rotatable circular saw blade that is vertically adjustable relative to the table top, the table top having an opening through which the saw blade can extend, the blade being configured to cut a work piece as the work piece is moved forwardly from a forward position to a rearward position, wherein the system comprises a riving knife mechanism releasably mounted to the saw rearwardly of the blade, and being configured to be adjustable between retracted and extended positions relative to the blade, a blade guard mechanism that is releasably mounted to the riving knife mechanism when the riving knife mechanism is at least in its extended position, the blade guard mechanism generally covering the blade and being adjustable to enable a work piece to be moved into cutting position by the blade and a kickback prevention mechanism that is releasably mounted to the riving knife mechanism when the riving knife mechanism is at least in its extended position, the kickback prevention mechanism being configured to engage a work piece as it is being cut by the blade and apply resistance to prevent the work piece from being expelled in the reverse direction.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to power tools and, more particularly, to power table saws. Power table saws typically have guard systems that either attach to the undercarriage of the table saw, to the rear of the table saw or attached to some structure above the table saw. In each of these configurations there are typically three components, namely, a splitter or riving knife, kickback prevention devices, (often called kickback dawgs) and a blade guard that covers the blade. A riving knife is a safety device that reduces the likelihood of a kick-back event where a work piece is somehow caught or bound up during a cutting operation and the inertia of the blade throws the work piece back toward the user. A riving knife is typically considered to function similarly to a spreader or splitter on a blade guard assembly, but does not extend above the top of the blade.  
         [0002]     With all known current commercial configurations, the user cannot separate these three components, which would be highly desirable depending upon particular circumstances, such as the type of cut that was being made.  
         [0003]     There are two basic types of cuts that are generally made with a table saw and those are through cuts and non-through cuts. During a through cut the blade is protruding through the entire thickness of the work piece, and in this type of cut there are few problems with current table saw guard configurations. However, when making a non-through cut, the user must remove the guard system if the guard system is of the type which is attached to the undercarriage or the rear of the table saw. These two configurations are typically utilized on most portable and bench top models that are presently commercialized. Because there is a need to remove the guard system during non-through and other special types of cuts and because special wrenches or the like are often necessary, many users simply leave it off.  
       SUMMARY OF THE INVENTION  
       [0004]     A preferred embodiment of the present invention is directed to a modular saw guard system for a power table saw of the type which has a table top, a rotatable circular saw blade that is vertically adjustable relative to the table top, the table top having an opening through which the saw blade can extend, the blade being configured to cut a work piece as the work piece is moved forwardly from a forward position to a rearward position, wherein the system comprises a riving knife mechanism mounted to the table saw rearwardly of the blade, and being configured to be adjustable between retracted and extended positions relative to the blade, a blade guard mechanism that is releasably mounted to the riving knife mechanism when the riving knife mechanism is at least in its extended position, the blade guard mechanism generally covering the blade and being adjustable to enable a work piece to be moved into cutting position by the blade and a kickback prevention mechanism that is releasably mounted to the riving knife mechanism when the riving knife mechanism is at least in its extended position, the kickback prevention mechanism being configured to engage a work piece as it is being cut by the blade and apply resistance to prevent the work piece from being expelled in the reverse direction.  
         [0005]     Other embodiments are directed to apparatus that are components of the preferred embodiment of the system. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a perspective view of the preferred embodiment of a modular guard system of the present invention;  
         [0007]      FIG. 2  is a perspective view of a portion of the system shown in  FIG. 1 , particularly illustrating a riving knife mechanism as shown in a retracted position wherein the top of the knife is positioned near or below the tabletop surface;  
         [0008]      FIG. 3  is another perspective view of the riving knife mechanism portion of the apparatus shown in  FIG. 1 , particularly illustrating the riving knife mechanism illustrated as installed on a table saw;  
         [0009]      FIG. 4  is a side view of a portion of the riving knife mechanism shown in  FIG. 2 ;  
         [0010]      FIG. 5  is an exploded perspective view of a portion of the riving knife mechanism, particularly illustrating a quick release assembly for the riving knife mechanism;  
         [0011]      FIG. 6  is a perspective view of a portion of the quick release assembly shown in  FIG. 5  and shown in the unlocked position;  
         [0012]      FIG. 7  is a perspective view of a portion of the quick release assembly shown in  FIG. 5  and shown in the locked position;  
         [0013]      FIG. 8  is an exploded perspective of a blade guard mechanism portion of the system shown in  FIG. 1 ;  
         [0014]      FIG. 9  is a perspective view of a portion of a quick release assembly for the blade guard mechanism shown in  FIG. 8 , and particularly illustrating an operating lever;  
         [0015]      FIG. 10  is a perspective view of a portion of a quick release assembly for the blade guard mechanism shown in  FIG. 8 , and particularly illustrating a link;  
         [0016]      FIG. 11  is a plan view of a portion of the quick release assembly of the blade guard mechanism, particularly illustrating the lever and link with the lever being shown in the unlocked position;  
         [0017]      FIG. 12  is a plan view of a portion of the quick release assembly of the blade guard mechanism, particularly illustrating the lever and link with the lever being shown in the locked position;  
         [0018]      FIG. 13  is an exploded perspective view of the kickback prevention mechanism of the system shown in  FIG. 1 ;  
         [0019]      FIG. 14  is a perspective view of a portion of the kickback prevention mechanism and particularly illustrating a latch body thereof;  
         [0020]      FIG. 15  is an end view of the kickback prevention mechanism shown in  FIG. 13 ;  
         [0021]      FIG. 16  is a plan view of the kickback prevention mechanism attached to the riving knife mechanism;  
         [0022]      FIG. 17  is another perspective view of the riving knife mechanism portion of the apparatus shown in  FIG. 1 , particularly illustrating the riving knife mechanism illustrated as installed on the motor and arbor gear box assembly of a table saw;  
         [0023]      FIG. 18  is a cross section of a portion of the kickback prevention mechanism shown in  FIG. 13 ;  
         [0024]      FIG. 19  is an end view of a portion of an alternative embodiment of a quick release assembly of the blade guard mechanism, particularly illustrating the lever and link with the lever being shown in the locked position; and  
         [0025]      FIG. 20  is a cross section taken generally along the line  20 - 20  in  FIG. 19 . 
     
    
     DETAILED DESCRIPTION  
       [0026]     The preferred embodiment of the present invention comprises a modular guard system that has a riving knife mechanism, a blade guard mechanism and a kickback prevention mechanism, all of which can be either quickly adjusted, attached and/or removed. However, the riving knife mechanism must be attached to the table saw in a generally extended position if the blade guard mechanism or the kickback prevention mechanism is used, because these latter two mechanisms are attached to the riving knife mechanism.  
         [0027]     With this type of modular configuration, the end user is more likely to use one or more of the guard system components as is necessary for a particular task being carried out on the table saw, rather than the typical choice a user now has, which is that of attaching or removing all of these components as part of a single guard system. While the illustrated embodiments of the present invention are shown in connection with a power table saw, it should be understood that the various quick release assemblies, as well as the mechanisms with which they are associated, can be utilized in other tools and environments, and that such other applications should be considered to be within the spirit and scope of the present invention. For example, embodiments of the present invention may be used with saws that are known as combo saws and flip saws that are marketed in Europe and possibly elsewhere.  
         [0028]     While the modular design of the preferred embodiment of the present invention permits the removal of the riving knife mechanism, the blade guard mechanism and the kickback prevention mechanism, the design is not meant to encourage such removal. In fact, what is encouraged is the use of these mechanisms at all times. However, the reality of decades of historical use of table saws is that commercial artisans as well as experienced woodworkers want to and do use table saws to make specialty cuts, including plunge cuts, cove cuts and dado cuts, for example. A plunge cut can be made by placing a work piece on the saw with the blade retracted, turning on the motor and cranking the blade upwardly to make a cut more or less in the middle of the work piece. A dado cut is one made with a dado blade that makes a wide cut, and is often used to cut a slot in a work piece, i.e., a non-through cut. A cove cut is a specialty non-through cut, where a work piece is guided by a jig of some type to move the work piece across the blade at an angle (and cutting only an eighth of an inch depth or less per pass) thereby using the curvature of the blade to cut and make a concave surface in the work piece.  
         [0029]     These specialty cuts cannot be made with known conventional riving knifes, blade guards and kickback dawgs being attached. Since commercial artisans and woodworkers remove them for such specialty tasks, the preferred embodiment of the present invention is configured to overcome many of the disadvantages of many conventional designs. One important feature is the elimination of the need to completely remove the riving knife mechanism to make any of the specialty cuts described above. If the blade guard mechanism and kickback prevention mechanism are detached from the riving knife, the riving knife can be easily retracted out of the way. After such specialty cuts are completed, the riving knife can then be easily adjusted to its extended position where the blade guard mechanism and kickback prevention mechanism can be quickly attached. Another benefit of the adjustable riving knife is that it maintains it alignment relative to the blade and therefore does not have to be realigned when it is adjusted to its extended positions  
         [0030]     Turning now to the drawings and particularly  FIG. 1 , there is shown a modular saw guard system, indicated generally at  20 , that includes a riving knife mechanism, indicating generally at  22 , a blade guard mechanism, indicated generally at  24 , and a kickback prevention mechanism, indicated generally at  26 . Each of these mechanisms has a quick release assembly, with the riving knife mechanism  22  having a riving knife quick release assembly indicated generally at  28 , the blade guard mechanism having a blade guard quick release assembly indicated generally at  30 , and the kickback prevention mechanism  26  having a kickback mechanism quick release assembly indicated generally at  32 .  
         [0031]     The blade guard mechanism  24 , as well as the kickback prevention mechanism  26  are both mounted to the riving knife mechanism  22  and each can be separated from the riving knife mechanism quickly and easily by virtue of the quick release assemblies associated with these mechanisms. Similarly, the riving knife mechanism  22  can be quickly and easily adjusted on the table saw. Since the preferred embodiment of the riving knife mechanism can be adjusted among several positions, one of which is a fully retracted position that is below the table top, there is no need to remove it completely from the table saw. When the other mechanisms that are normally mounted to the riving knife mechanism are detached from the saw, the riving knife mechanism can be easily retracted and be completely out of view. This is a desirable feature, because it can be quickly and easily adjusted to one of its extended and intermediate positions. The convenience of this capability encourages the use of these safety features.  
         [0032]     The riving knife mechanism  22  is adjustable by virtue of the quick release assembly  28  so that its elevation relative to the blade can be adjusted. More particularly, it can be positioned to any one of three elevations, including a retracted position where the top of the assembly is completely below the surface of the tabletop, a fully extended position and an intermediate position. In a fully extended position, the top of the riving knife mechanism  22  extends above the elevation of the top of the blade and is in the desired position where the blade guard mechanism  24  and the kickback prevention mechanism  26  can be mounted to the riving knife mechanism.  
         [0033]     The riving knife mechanism  22  can also be installed in an intermediate position that is generally midway between the retracted and fully extended position where it is operated as a conventional riving knife, as opposed to a separator or splitter. For this operating position, it is at a mid-mounting point and has the blade guard mechanism and the kickback prevention mechanism removed. In this position, the top of the riving knife is below the top edge or reach of the blade by a distance that is preferably between 3 and 5 millimeters. In this position, the user has the added security of the riving knife operating as a splitter which prevents the two cut work piece parts from closing on one another behind the blade which can bind the blade and create a kickback condition. It can also be used in the non-through cut mode where the top of the riving blade mechanism will penetrate into the partial cut line. In this regard, it should be understood that the riving knife mechanism  22  is mounted to a motor and arbor gear box assembly  87  (see  FIG. 17 ) that drives the blade and is vertically as well as angularly adjustable. Since the elevation and angle of riving knife mechanism  22  changes as the motor and arbor gear box assembly  87  changes, the position of the riving knife mechanism  22  is constant relative to the blade.  
         [0034]     As previously mentioned, when the riving knife mechanism is in its fully extended position, the blade guard mechanism  24  and kickback prevention mechanism  26  can be easily mounted to the riving knife mechanism  22 . Alternatively, if better visualization is necessary, it is possible to remove the blade guard mechanism  24  and install the kickback prevention mechanism  26  to provide the security of having the splitter and the kickback prevention mechanism  26  be in an operational condition.  
         [0035]     The riving knife mechanism  22  has an elongated generally curved thin knife  34  in addition to the quick release assembly  28 . As best shown in  FIGS. 2 and 4 , the knife  34  is preferably a steel stamping and has a generally curved configuration with a center slot  36  that extends substantially the full length of the knife  34 . There are a number of apertures  38  and  40  which are located on opposite sides of the slot  36 , as well as an aperture  42  located generally in line with the slot  36  and positioned at the bottom of the knife  34 . The apertures  38  are located generally midway between the ends of the knife  34 .  
         [0036]     As best shown in  FIG. 4 , an aperture  44  is located on the left side of the slot  36  and an elongated recess  46  is formed in the outer surface on the opposite side of the slot  36  with the recess  46  having a pair of spaced apart hook configurations  48   a  and  48   b  thereof which cooperate with the blade guard mechanism quick release assembly  30  to mount the blade guard mechanism  24  to the knife  34 . Also, the outside surface adjacent the recess  46  contains a flat surface  50  that terminates in a shoulder  52  that cooperate with an aperture  54  for mounting the kickback prevention mechanism quick release assembly  32  to the knife  34 .  
         [0037]     With regard to the riving knife mechanism quick release assembly, it is shown in its locked position in  FIGS. 2, 3 ,  4 ,  5  and  7  and in the unlocked position in  FIG. 6 . Referring initially to  FIG. 5 , the quick release assembly  28  comprises a lever  56  that has a handle portion  58 , the lever  56  being mounted on a stud  60  and is rotatable as well as axially movable relative to the stud  60  between a locked position where the handle  58  is generally horizontal and an unlocked position where it is generally vertical, as is best shown in  FIG. 6 . The lever  56  preferably moves within the range of approximately 90 degrees to about 115 degrees between its locked and unlocked positions. The stud  60  has a large generally cylindrical portion with a flat end  64  and a generally 45° angled face portion  66  that is provided for the purpose of creating necessary clearance when the blade guard mechanism  24  is installed in a table saw. Similarly, a 45° flat face portion  68  is provided on the lever  56  for similar reasons. It should be understood that with different clearances, such face portions  66  and  68  may be unnecessary.  
         [0038]     The stud  60  has an extension  70  that has a generally square cross sectional configuration that engages a square aperture  72  in a plate member  74  that is positioned to contact the knife  34  as shown in  FIG. 4 , for example. It is also apparent from  FIGS. 2 and 4  that the plate member  74  has a transverse extension  76  that is configured to abut the side of the knife  34  as well as the side of a bracket  78  as best shown in  FIG. 7 . The bracket  78  has an upper transverse extension  80  with apertures  82  and  84  for mounting the bracket to either the frame or the portion of the blade drive structure of the table saw. This is shown in  FIG. 3  where the extension  80  is mounted to such structure by cap nuts  86 .  
         [0039]     The bracket  78  also has a number of relatively short pins  88  which extend from a front face  90  thereof. The front face contacts the knife  34  and the pins  88  are located on the front face  90  so that they can engage the apertures  38 ,  40  and  42  of the knife  34 . In this regard, the plate member  74  also has apertures  92  and  94  that are configured to receive the pins  88  that extend through the apertures in the knife  34 . Thus, when the bracket  78 , knife  34  and plate member  74  are sandwiched together, the pins firmly hold the knife  34  in the desired position.  
         [0040]     It should be apparent from  FIGS. 2 and 5 , that the knife  34  can be positioned in one of three positions, i.e., the lower position where the pattern of pins  88  penetrate the apertures  40  and  42 , the mid position where the pins  88  penetrate the apertures  38  and the lower pin rides in the slot  36  and in the upper position where one of pins  88  penetrates the aperture  44  and another seats in the recess  46 . The front face  90  of the bracket  78  also has a generally square aperture  96  through which a screw  98  passes.  
         [0041]     The screw  98  is configured to fit through the aperture  96 , the slot  36  of the knife  34 , the aperture  72  and into a threaded aperture  100  in the extension  70  of the stud  60 . The configuration of the stud extension  70  is slightly smaller than the size of the square apertures  72  and  96  so that the extension  70  will fit within them, but cannot rotate relative to the plate member  74  or the bracket  78 . Therefore, the stud  60  is locked in position regardless of whether the quick release assembly  28  is in its locked or unlocked position.  
         [0042]     It should also be understood that the length of the extension  70  is sufficient that the plate member  74  can move away from the knife  34  and the knife can move away from the bracket  78  a sufficient distance that the pins are disengaged from the apertures of the knife  34 . This enables the elevation of the knife to be adjusted as desired.  
         [0043]     However, the quick release mechanism  28  is configured to clamp the plate member  74  and knife  34  against the front face  90  of the bracket  78  when the quick release assembly is in its locked position. This is accomplished by the lever  56  having a cam surface  102  that extends approximately ¼ of a rotation between its locked and release position. A pin  104  is located in the cylindrical portion  62  and is sized so that it engages the sidewalls of the cam surfaces  102 . While it is possible for a single cam surface to be used, a pair of opposed cam surfaces is preferred and is used to balance the forces that may be applied during operation. Since the pin  104  is secured to the stud  60  and the stud  60  is incapable of being rotated, as the lever  56  is rotated, it will cause its end face  106  to move toward and away from the plate  74  to lock it in place when it is in its generally horizontal position.  
         [0044]     As shown in  FIG. 3 , the lever is positioned just below the surface of the table top when the motor, gear, and blade assembly is positioned in its upper most and un-beveled position, so that when a typical tabletop insert plate is removed (it is not present in  FIG. 3 ), a user can readily access the lever  56  to rotate the same when it is desired to either remove or reposition the knife  34 . The quick release assembly  28  also has a number of washers  108  to provide wear protection and ease of operation of the assembly  28 .  
         [0045]     With regard to the blade guard mechanism  24 , and referring initially to  FIG. 8 , it is shown in an exploded perspective which includes the blade guard mechanism quick release assembly  30 , as well as a blade guard  120  that is configured to cover the blade of a table saw during operation. In this regard, the blade guard  120  has sidewalls  122  and a top portion  124 , with the sidewalls having apertures  126  through which screws and a collar  128  are configured to pivotally mount the blade guard  120  to a mounting portion  130 , with the screws  128  being inserted into apertures  142  on opposite sides of the mounting portion. While the blade guard  120  is shown to be a unitary structure, it should be understood that it could be two separate sidewalls and that rather than a top wall  124 , the mounting portion  130  could have a forward extension that cooperates with the other components. Such a structure is intended to be within the scope of the present invention as are other blade guard configurations.  
         [0046]     The mounting portion  130  has a center channel  132  in which a link  134  and lever  136  are located. The link  134  has an aperture  138  in which a pin  140  is inserted, with the pin  140  also extending through apertures  142  in the mounting portion  130 . Thus, the link  134  is pivotally attached to opposite sides  144  of the mounting portion  130 . The link  134  has a narrower opposite end portion  146  in which an aperture  148  is located and the lever  136  has a lever handle  150  as well as two sidewalls  152  that are spaced apart from one another by a distance that is slightly greater than the width of the end extension  146 . The sidewalls  152  contain apertures  154  and  156  for receiving pins  158  and  160 , respectively, as well as an elongated horizontal slot  162  sized to receive the pin  160 , which is slideable in it  
         [0047]     As shown in  FIG. 11 , the pin  160  slides in the slot  162 , and when the assembly  30  is in its retracted or unlocked position, the handle  150  of the lever  136  is elevated which causes the end  146  of the link to also be elevated and simultaneously move the outer end of the lever  136  where the pin  160  is located in the apertures  156  to move to the right as shown in  FIG. 8  and to the left as shown in  FIG. 11 . This enables the pin  160  to be retracted from the hook configuration  48   a  of the recess  46  of the knife  34  (see  FIG. 4 , for example). The opposite pin  140  located in the other hook configuration  48   b . When the mounting portion is positioned on the knife  34  with the pin  140  engaging the hook  48   b  and the lever  150  is pushed down so that it is in a generally horizontal position, the pin  160  will move in the slot  162  away from the pin  140  and engage the hook  48   a  to hold the blade assembly to the knife  34 .  
         [0048]     As is best shown in  FIG. 10 , the larger end of the link  134  has a transverse slot  164  that has a width that is slightly larger than the thickness of the knife  34  on which the link  134  is positioned when the blade guard mechanism  24  is attached to the knife  34 . Similarly, the mounting portion  130  has a slot  166  which enables the mounting portion to also fit on the blade  34 . The slots  164  and  166  (see  FIGS. 8 and 11 ) thereby hold the blade guard from rocking from side to side when it is attached to the knife  34 . It should be appreciated that the pin  140  is exposed in the slot  164  when the blade guard mechanism  24  is attached to the knife  34 , and the pin  140  has a diameter that generally conforms to the curvature of the hook  48   b  and the pin  160  also has a diameter that generally conforms to the curvature of the hook  48   a  of the knife  34 .  
         [0049]     The view of the link  134  and lever  150  are shown in the retracted or unlocked position in  FIG. 11  and in the locked position in  FIG. 12 . It is preferred that the distance between the pins  160  and  140  when in the locked position apply at least a minimal amount of force to the opposite hook configurations  48   a  and  48   b  so that the mechanism will exhibit a force tending to hold the mechanism in its locked position. The design creates a lock action via an over-center camming action between the link  134  and the lever  150 . When the three points that comprise these parts are in a straight line, they are in compression. Furthermore when the lever  150  forces the middle point below the center point, it reaches an equilibrium that is held in place by a combination of gravity and the compressive force on the link  134  and the lever  150 . However, it should be understood that when the blade guard is locked, gravity has no effect of the assembly, but when the mechanism is in the unlocked position gravity holds the guard  24  to the knife  34 .  
         [0050]     An alternative embodiment of the quick release assembly  30 ′ is shown in  FIGS. 19 and 20 , which illustrates components that have similar shapes as having the same reference numbers and a prime designation. Thus, the above description with regard to the quick release assembly  30  has applicability to the alternative embodiment. The alternative embodiment enables the assembly  30 ′ to be adjusted so that reliable locking via an over-center camming action between the link  134 ′ and the lever  150 ′ can be achieved even with less stringent manufacturing tolerances. This is achieved by having the pin  140  riding in an elongated slot  141  and being adjustable to effectively vary the length of the link  134 ′ and outer end of the lever  136 ′. This is done by varying the depth of a pair of set screws  135  that are threaded in apertures in opposite sides  144 ′ of the mounting portion  130 ′. Thus, by rotating the set screws  135 , the pin  140  can be moved in the slot to cause the pin  160  to be moved relative to the hook configuration  48   a  of the blade  34 . This embodiment has another pin  161  that is mounted between side portions  144  located below pin  140 , and this pin  161  is inserted into the recess  46  and engages the hook configuration  48   b . By having this additional pin  161  engaging the hook configuration  48   b , adjustment of the pin  140  effectively changes the distance between pins  160  and  161  when the handle  150 ′ is in its locked position as shown, enabling reliable locking action to be achieved.  
         [0051]     Turning now to the kickback prevention mechanism  26  and referring to  FIG. 13  which is an exploded perspective of the mechanism, the mechanism includes a bracket  180  that has transverse leg portions  182  that have cylindrical support sleeves  184  that have apertures  186  for receiving a pair of pivot shafts  188  and  190 . The pivot shafts  188  and  190  are preferably solid steel and are force fit and tightly secured in the apertures  186 , with the left shaft  188  being slightly longer than the shaft  190 . A mounting latch body  192  also shown in  FIG. 14  has a pair of cylindrical extensions  194  on opposite sides thereof, each of which has an aperture  196  therein, with the size of the aperture  196  being slightly larger than the diameter of the pivot shafts  188  and  190  so that the latch body  192  can slide on the pivot shafts  188  and  190 .  
         [0052]     The latch body  192  has side walls  198  and a narrow slot  200  located between them. The slot  200  shown in either  FIG. 13  or the enlarged similar view shown in  FIG. 14  actually extends the entire distance from the front to the rear. The latch body also has a pocket  202  in which one end of a compression spring  204  is placed. The mechanism has a pair of elongated kickback arms  206  which have an aperture  208  on one end thereof together with an end ear  210  that extends away from the aperture  208  that is configured to engage an extension  211  to limit the movement of the arm  206  in the downward direction when attached to the knife  34 . The apertures  208  of the arms  206  are sized to fit on the cylindrical portions  194 .  
         [0053]     A torsion spring  212  is provided and fits around enlarged cylindrical portions  213  and has a center bridge portion  214  that bears against a shoulder  215  on the top of the latch body  192 , and a pair of outer ends  216  that bear against a back edge  218  of the arms  206 . The opposite side of the arms has a number of serrated points  220  that are configured to engage a work piece in the event that it is kicked back in the reverse direction during a cutting operation which could cause injury to the user of the table saw. Since a kickback event is extremely dangerous and can apply a substantial force on the work piece, the pivot shafts  188  are preferably sized to withstand a substantial force and therefore are approximately ¼″ in diameter and made of solid hardened steel.  
         [0054]     As shown in  FIG. 16 , the kickback prevention mechanism  26  sits on and is mounted upon the knife  34  and has a quick release assembly  32  that generally comprises the latch body  192  in combination with the pivot shafts  188  and  190  in connection with the bracket  180 . The slot  200  has a width that is slightly greater than the thickness of the knife  34  and top face  222  of the slot  200  is preferably straight and extends from front to rear so that it will engage the flat surface  50  and shoulder  52  of the knife  34  as shown in  FIGS. 4 and 16 .  
         [0055]     As shown in  FIG. 4 , the aperture  54  is provided adjacent the flat surface  50  and is sized and configured to receive the pivot shaft  188  when it is locked in position. As is best shown in  FIG. 15 , a compression spring  204  is provided and has one end retained by an extension  226  located on the inside of the leg portion  182  as shown in  FIG. 15  with the opposite end seated in the pocket  202  preferably formed on the latch body  192 . Since the latch body is slideable on the pivot shafts  188  and  190 , the compression spring  224  forces the latch body to be right as shown in  FIG. 15  which maintains the kickback prevention mechanism quick release assembly  32  in its locked condition.  
         [0056]     To attach or remove the kickback prevention mechanism  26  from the knife  34 , the user needs to push the latch body  192  to the left relative to the bracket  180  as shown in  FIGS. 15 and 18 . When this is done, the latch body slot  200  moves relative to the pivot shaft  188  so that the shaft  188  is disengaged from the aperture  54  in the knife  34 , enabling the latch body  192  and therefore the kickback prevention mechanism  26  to be lifted from the knife  34 . It should be appreciated that the views of  FIGS. 15 and 18  are from the rear while the view of  FIG. 13  is from the right front. The foregoing description is made from the perspective of  FIGS. 15 and 18 .  
         [0057]     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.  
         [0058]     Various features of the invention are set forth in the appended claims.