Patent 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, the table top having an opening through which the saw blade can extend, the system comprising a riving knife mounted to the saw rearwardly of the blade and having a top surface and at least one aperture near the top surface, a blade guard and kickback prevention mechanism that is releasably mounted to the riving knife, the mechanism comprising a mounting channel configured to fit on and be releasably attached to the riving knife, the blade guard portion being pivotally attached to the mounting channel, the kickback prevention portion being pivotally attached to the mounting channel; and a lever mechanism for holding the mounting channel to the riving knife and for releasing the mounting channel for removal therefrom, the lever mechanism including a movable pin member for engaging the aperture of the riving knife.

Full Description:
[0001]     This application is a continuation-in-part of patent application entitled A MODULAR GUARD SYSTEM AND APPARATUS FOR A POWER SAW Ser. No. 11/284,214, filed Nov. 21, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention generally relates to power tools and, more particularly, to power table saws.  
         [0003]     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 attach 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 dogs) 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.  
         [0004]     With all known commercial table saw guard configurations, the end user cannot separate the riving knife from the other components. There are times when this is desirable based on the type of cut being made.  
         [0005]     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 mounting 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 to do so, many users simply leave the guard system off.  
       SUMMARY OF THE INVENTION  
       [0006]     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, the table top having an opening through which the saw blade can extend, the system comprising a riving knife mounted to the saw rearwardly of the blade and having a top surface and a predetermined thickness that is greater than the thickness of the blade body and less than the thickness of the kerf of the blade, the riving knife having at least one aperture near the top surface, a blade guard and kickback prevention mechanism that is releasably mounted to the riving knife, the mechanism having a blade guard portion above the blade and being adjustable to enable a work piece to be moved into cutting position by the blade and a kickback prevention portion 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,  
         [0007]     the mechanism further comprising a mounting member configured to fit on and be releasably attached to the riving knife, the blade guard portion being pivotally attached to the mounting member, the kickback prevention portion being pivotally attached to the mounting member, a lever mechanism for holding the mounting member to the riving knife and for releasing the mounting member for removal therefrom, the lever mechanism including a movable pin member for engaging the aperture of the riving knife. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of the front right side of the preferred embodiment of a modular guard system of the present invention;  
         [0009]      FIG. 2  is a perspective view of the front left side of the system shown in  FIG. 1 , with portions removed;  
         [0010]      FIG. 3  is another perspective view of front right side of the mounting channel and kickback prevention mechanism portion of the system shown in  FIG. 1 ;  
         [0011]      FIG. 4  is an enlarged perspective view of a portion of the mounting channel and kickback prevention mechanism shown in  FIG. 3 ;  
         [0012]      FIG. 5  is a perspective of the right side of the riving knife of the system shown in  FIGS. 1 and 2 ;  
         [0013]      FIG. 6  is a plan view of the right side of the system shown in  FIG. 1 , particularly illustrating the blade guard mechanism hinge in its operating position;  
         [0014]      FIG. 7  is a plan view of the right side of the system shown in  FIG. 1 , particularly illustrating the blade guard mechanism hinge in its raised non-operating position;  
         [0015]      FIG. 8  is an exploded perspective of a portion of the blade guard and kickback prevention mechanism shown in  FIG. 1 ;  
         [0016]      FIG. 9  is a perspective view of the right side of a portion of blade guard and kickback prevention mechanism shown in  FIG. 8 , and particularly illustrating a mounting channel configured to fit on and be releasably attached to the riving knife;  
         [0017]      FIG. 10  is a perspective view of the right side of a portion of blade guard and kickback prevention mechanism shown in  FIG. 8 , and particularly illustrating a lever mechanism for holding the mounting channel to the riving knife and for releasing the mounting channel; and  
         [0018]      FIG. 11  is a plan view of the right side of a portion of blade guard and kickback prevention mechanism shown in  FIG. 8 , and particularly illustrating a movable pin member for engaging the aperture of the riving knife;  
         [0019]      FIG. 12  is a simplified side view of an upper blade guard portion that attaches to the blade guard mechanism hinge. 
     
    
     DETAILED DESCRIPTION  
       [0020]     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.  
         [0021]     A quick attachment mechanism for the riving knife is shown and described in the aforementioned application entitled A MODULAR GUARD SYSTEM AND APPARATUS FOR A POWER SAW Ser. No. 11/284,214, filed Nov. 21, 2004, which is specifically incorporated by reference herein. Because the embodiments described herein have a riving knife with a very similar lower mounting configuration as is shown and described in the above application, the description of the quick attachment mechanism is not provided here.  
         [0022]     With the modular configuration of the embodiments of the present system, the end user is more likely to use the riving knife and the blade guard and kickback prevention mechanism 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 system mechanisms 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.  
         [0023]     While the modular design of the preferred embodiment of the present invention permits the removal of the riving knife mechanism together with the blade guard 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 whenever practicable. 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.  
         [0024]     These specialty cuts cannot be made with known conventional riving knifes, blade guards and kickback dogs 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 some of the specialty cuts described above. For example, It will not need to be removed for a dado cut. It may need to be removed for a cove cut if it goes too deep, and similarly for a plunge cut. If the blade guard and kickback prevention mechanism is 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 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  
         [0025]     Turning now to the drawings and particularly  FIGS. 1-8 , there is shown a major portion of a modular saw guard system, indicated generally at  20 , that includes a riving knife  22 , a blade guard and kickback prevention mechanism, indicated generally at  24 . The blade guard and kickback prevention mechanism  24  has a quick release assembly  26  that enables it to be easily mounted on and removed from the riving knife  22 .  
         [0026]     The riving knife  22  is adjustable so that its elevation relative to the blade can be changed. When it is used as a standard guard, the blade guard and kickback prevention mechanism  24  is attached to it and the system  20  is then easily attached to a designated mounting post which not shown but is located below the top T of the table (see  FIG. 6 ) as is well known to those skilled in the art, and either moves up and down with the movement of the blade when it has an undercarriage mount, or stays in position relative to the top of the table when it is in a rear tool mount position.  
         [0027]     When the system is used as a splitter, the blade guard and kickback prevention mechanism  24  can be removed quickly by using its quick release assembly  26 , and the saw can now perform standard through cuts with the added safety of the riving knife  22  in position. The removal of the blade guard and kickback prevention mechanism is desired on some cuts due to the need for the operator to have more visual guidance, and to avoid any undesirable scratches or markings on the material being cut from the kick back arms. In this position, the riving knife  22  rides directly behind the blade, and is higher than the top of the blade.  
         [0028]     When used as a riving knife for linear moving undercarriage mounts only, the blade guard and kickback prevention mechanism  24  are removed from the riving knife  22  and the riving knife is mounted in an intermediate position where it is operated as a conventional riving knife, as opposed to a separator or splitter. 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  22  is mounted to a motor and arbor gear box assembly (not shown but also well known to those skilled in the art) that drives the blade and is vertically as well as angularly adjustable. Since the elevation and angle of riving knife  22  changes as the motor and arbor gear box assembly changes, the position of the riving knife  22  is constant relative to the blade.  
         [0029]     The riving knife  22  is preferably a steel stamping and has an elongated generally curved thin base portion as shown in  FIG. 5 , with a center slot  30  that extends from the bottom to the center portion of its height. There are two apertures  32  and  34  which are located on opposite sides of the slot  30 , for attaching the riving knife  22  to the mounting post of the saw. The knife  22  also has an aperture  36  positioned near its substantially flat top surface  38  and a slot, indicated generally at  40 , which has a vertical portion  42  defining an opening that merges with a forwardly (i.e., toward the blade) extending portion  44  that define a shelf  46  for retaining the rear end of blade guard and kickback prevention mechanism  24 .  
         [0030]     In this regard, and referring to  FIGS. 1-4 ,  6  and  7 , the blade guard and kickback prevention mechanism  24  has an elongated U-shaped mounting channel  48  that has a top portion  50  and spaced apart legs  52  and  54  that extend downwardly from the top portion.  
         [0031]     As is best shown in  FIG. 9 , an extension  56  from the leg  54  has a transverse first portion  58  a vertical portion  60  and return portion  62 , with portions  58  and  62  having apertures  64  for receiving a hinge pin. A second extension  66  extends outwardly from the leg  54  and then vertically and it has aperture  68  that is aligned with apertures  70  in the legs  54  and  52 . The apertures  68  and  70  are provided to receive a locking pin for locking the channel  48  to the riving knife  22 . Apertures  71  are provided in each of the legs  52  and  54  for attachment to kickback arms and apertures  72  are provided for pivotally supporting the blade guard portion of the blade guard and kickback prevention mechanism  24 . The legs  52  and  54  have curved end portions  74  that terminate in transverse stop surfaces  76  for limiting movement of a plate guard hinge  78  when the blade guard is moved upwardly into a non-protecting, non-operative position.  
         [0032]     As is apparent from the foregoing discussion, and as best shown in  FIG. 3 , the U-shaped channel  48  supports the plate guard hinge  78  which has a lower mounting portion  80  that has two spaced apart legs  82  with apertures for receiving a pair of cylindrical bushings  84  that fit in these apertures and in apertures  72  in the sidewalls  52  and  54 . The bushings  84  are preferably held together with a rivet  86  that is installed into apertures in the bushings, with the reduced diameter portions of the bushings being sized to closely fit in the apertures  72  of the mounting channel  48 . The hinge  78  has a pair of transverse flanges  88  which have apertures  90  which are sized to receive attachment pins, rivets, screws, bolts or other connecting means that permit pivoting movement (not shown) for attaching an upper guard  92  (see  FIG. 12 ) that has an aperture  94  for receiving a connector such as a rivet, bolt or the like for attaching the hinge  78  to the upper guard  92 . The upper guard  92  is preferably made from a clear polycarbonate or other plastic material and covers the blade during cutting operations.  
         [0033]     The quick release assembly  26  enables the U-shaped channel  48  to be easily and quickly attached and removed from the riving knife  22 . Referring to  FIGS. 1, 3 ,  4 ,  10  and  11 , the assembly  26  includes a release lever  102  having a free end portion  104  that presents a handle for an operator, with the lever  102  having a mounting end comprising two spaced mounting portions  106 , each of which have an aperture  108  for receiving a hinge pin  110  that pivotally connects the release lever  102  to the U-shaped channel  48 . Midway between the ends of the release lever  102  is an elongated slot  112  in which a release pin  114  is provided.  
         [0034]     As best shown in  FIG. 11 , the release pin  114  has a reduced diameter portion  116  and it has an aperture  118  which a locking pin  120  is press fit into. The reduced diameter portion  116  defines a shoulder  122  which contacts the interior surface of the release lever  102 . The pin  114  is positioned in apertures  68  and  70  when it is in locking position. However, when the release member lever  102  is pulled away from the riving knife  22 , the release pin disengages from aperture  36  in the riving knife  22 .  
         [0035]     When the blade guard and kickback prevention mechanism  24  is mounted on the riving knife  22 , the assembly  26  is biased to remain secured to the riving knife  22 . As best shown in  FIGS. 4 and 10 , this is done by a torsion spring  124  that has one end  126  bearing upon the sidewall  54  and the other end biased against a bridge portion  128  of the release lever  102 .  
         [0036]     The kickback prevention functionality is provided by a pair of arms  130  that have one or more points  135  in the lower surface thereof that are configured to engage the work piece and prevent it from being expelled back toward the operator if a kickback condition arises. The arms  130  are pivotable around bushings  132  and a rivet  134  is installed between the two bushings  132 . As best shown in  FIG. 8 , the rightward bushing  132  has a reduced diameter left portion  133  that is sized to preferably snugly fit aperture  71  in the legs  52  and  54  of the channel  48  and the openings in plates  142  and  144 . The diameter of this portion  133  also corresponds to the width of the portion  42  and the height of portion  44  of the slot  40  of the riving knife  22 . The length of the portion  133  is sufficient to extend across the gap between the legs  52  and  54  and also to be seated in the apertures  71  of both legs. Alternatively, the bushings  132  as well as bushings  84  may be complimentary in construction so that they can be press fit together without the use of a connecting pin.  
         [0037]     The kickback arms  130  have an aperture  136  on one end thereof together with an end ear  138  that extends away from the aperture  136  that is configured to engage a stop pin  140  to limit the movement of the arms  130  in the downward direction. The apertures  136  of the arms  130  are sized to fit the cylindrical bushings  132 . Also, torsion springs (not shown) are provided and fit around each bushing  132  that have one end that bear against the stop pin  140  and an opposite end that bear against the back edge of each of the arms  130 .  
         [0038]     When the blade guard and kickback prevention mechanism  24  is to be mounted to the riving knife  22 , the channel  48  is placed over the flat portion  38  so that the portion  133  of the bushing that extends between the legs  52  and  54  fits into the slot  40  and is moved forwardly into the horizontal portion  44  so that it is held captive by the shelf  46 . When it is this forward position, the release pin  114  of the assembly  26  is aligned with the aperture  36  of the riving knife  22  and can be inserted to lock the blade guard and kickback prevention mechanism  24  in place. It should be understood that the channel  48  will not seat horizontally unless and until the operator pulls the handle  104  away from the channel  48  to enable the pin  114  to clear the riving knife  22 . Once the channel is properly seated, the operator can release the handle  104  and the spring  124  will drive the pin  114  into the apertures  70  and  36 .  
         [0039]     Removal of the blade guard and kickback prevention mechanism  24  merely requires the operator to pull the handle  104  outwardly to remove the pin  114  from the aperture  36 , which permits sliding the blade guard and kickback prevention mechanism  24  rearwardly (i.e., to the right as shown in  FIG. 1 , for example) so that the bushing  132  can clear the shelf  46  and the mechanism separated from the riving knife  22 .  
         [0040]     It is desirable to have the thickness of the riving knife  22  be a predetermined thickness that is greater than the thickness of the blade body and less than the thickness of the kerf of the blade, (the kerf being the width of cut made by the saw blade). The blade guard and kickback prevention mechanism  24  of the preferred embodiment of the present invention allows the upper guard hinge  78 , upper guard  92  and kickback arms  130  to be used with the U-shaped channel  48  when knives of different thicknesses are used. This is achieved by the use of shims  142  and  144  that are positioned on the inside of the legs  52  and  54 . They are retained by set screws (not shown) that fit within apertures  138  in the sidewalls  52  and  54  that can be adjusted to position the spacing between the shims  142  and  144  to accommodate riving knifes  22  of different thicknesses. The shims have apertures sized and aligned with apertures in the legs  52  and  54  where necessary so that the functionality or operability of the system is not impaired.  
         [0041]     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.  
         [0042]     Various features of the invention are set forth in the appended claims.

Technology Classification (CPC): 1