Abstract:
A riving knife mounting assembly is provided that rigidly and accurately positions the riving knife relative to the cutting blade by way of a simple and intuitive mechanism. Interaction between a clamping plate and a locking plate engage opposite sides of the riving knife to hold the riving knife in place, and provides a sensible indication that the two components are properly mated. A cam lever assembly allows loosening or tightening the clamping plate and locking plate together about the riving knife by simply rotation of the lever. A spring assembly maintains pressure on the riving knife even in the loosened position to maintain proper positioning of the components. The clamping plate is part of a mounting bracket that is mounted to a motor arm movable with the drive assembly, and includes adjustment screws for adjusting the orientation of the riving knife relative to the cutting blade in multiple degrees of freedom.

Description:
REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM 
       [0001]    This application is a utility filing from and claims priority to provisional application No. 62/047,979, filed on Sep. 9, 2014, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The disclosure relates to power tools and particularly to power tools integrated into a table that provides a work surface for supporting the workpiece, such as power table saws. 
         [0003]    A number of power tools have been produced to facilitate forming a work piece into a desired shape. One such power tool is a table saw. A wide range of table saws are available for a variety of uses. Some table saws, such a cabinet table saws, are very heavy and relatively immobile. Other table saws, sometimes referred to as jobsite table saws, are relatively light and portable so that a worker can position the table saw at a job site. Some accuracy is typically sacrificed in making a table saw sufficiently light to be mobile. The convenience of locating a table saw at a job site, however, makes job site table saws very desirable in applications such as general construction projects. 
         [0004]    All table saws, including cabinet table saws and job site table saws, present a safety concern because the saw blade of the table saw is sharp and moving at a high rate of speed. Accordingly, severe injury such as severed digits and deep lacerations can occur almost instantaneously. A number of different safety systems have been developed for table saws in response to the dangers inherent in an exposed blade moving at high speed. One such safety system is a riving knife which functions to restrain the workpiece from kickback. If the riving knife is poorly or loosely adjusted its function is compromised. Typical riving knives exhibit excessive play when in the unlocked position which hampers the ability of the operator to readily and securely fix the riving knife in its locked position. Another difficulty encountered by operators using a table saw arises in mounting and adjusting the riving knife. There is thus a need for a riving knife mounting arrangement that is intuitive to the operator and that allows the component to be easily and accurately engaged to the power tool. 
       SUMMARY 
       [0005]    A mounting assembly for mounting a riving knife of a table saw to a motor arm of the table saw comprises a mounting bracket mountable to the motor arm of the table saw, the mounting bracket including a clamping plate defining a clamping surface facing the riving knife and a locking plate defining a locking surface facing the riving knife and the clamping plate, for clamping the riving knife therebetween. A tab and recess arrangement is defined between the mounting bracket and the locking plate, in which the tab is sized to extend through the arcuate slot of the riving knife and the recess is sized to receive the tab when the tab extends through the arcuate slot. The tab and recess arrangement maintains the clamping plate, locking plate and riving knife in a proper position even as the angular orientation of the riving knife is adjusted. 
         [0006]    The mounting assembly further comprises a lever assembly engaged between the mounting bracket and locking plate that is operable to press the mounting bracket and locking plate together about the riving knife to clamp the riving knife between the clamping surface and the locking surface In one aspect, the lever assembly includes an elongated locking shaft extending through shaft openings in the mounting bracket and the locking plate, the locking shaft configured to extend through the arcuate slot in the riving knife. One end of the locking shaft is fastened to the clamping plate while the opposite end of the locking shaft includes a lever hub rotatably mounted thereon. The lever hub includes a manually engagable lever for rotating the lever hub relative to the locking shaft. A spring arrangement is mounted on the locking shaft between the lever hub and the locking plate. In one aspect, the lever assembly includes a cam arrangement between the locking shaft and the lever hub operable to pull the locking shaft toward the lever hub upon rotation of the lever hub, to thereby pull the clamping plate toward the locking plate against the force of the spring arrangement to thereby clamp the riving knife between the clamping surface and locking surface. 
         [0007]    In one aspect, the spring arrangement can include two bevel washers opposing each other. In a further aspect, the lever hub defines a bore therethrough and an arcuate cam slot in communication with the bore, and the locking shaft includes a shaft hub at the opposite end of the shaft that is received within the bore of the lever hub to permit rotation of the lever hub relative to the shaft hub. The shaft hub includes a pin projecting from the shaft hub and into the arcuate cam slot, with the cam slot configured to move the pin toward or away from the clamping plate upon rotation of the lever hub. 
         [0008]    In another feature, one of the clamping plate and the locking plate includes a pair of bosses corresponding to a pair of openings in the riving knife that flank the arcuate slot. The other of the clamping plate and the locking plate includes a pair of openings to receive the pair of bosses passing through the pair of openings in the riving knife but only when the riving knife is clamped between the clamping plate and locking plate. A shoulder screw may be provided that extends through the locking plate and through the arcuate slot in the riving knife, and fastened to the clamping plate at a position below the elongated locking shaft relative to the length of the riving knife. A spring disposed between the head of the shoulder screw and the locking plate applies a spring force between the clamping plate and locking plate that is insufficient to clamp the riving knife between the clamping plate and the locking plate. However, the spring force is sufficient to push the pair of bosses into the matched pairs of openings when in alignment. 
         [0009]    The locking shaft includes a keyed portion extending through the shaft opening in the clamping plate and the shaft opening of the clamping plate is complementary configured to the keyed portion to prevent rotation of the locking shaft relative to the clamping plate. 
         [0010]    The mounting bracket includes a mounting plate defining at least one fastener opening to receive a fastener for engaging the motor arm of the table saw. The mounting plate may further include at least one adjustment screw extending through a threaded adjustment opening in the mounting plate and arranged to bear on the motor arm when the mounting plate is engaged to the motor arm to adjust the position of the mounting bracket relative to the motor arm. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of a table saw according to the disclosure. 
           [0012]      FIG. 2  is a side view of the table saw shown in  FIG. 1 . 
           [0013]      FIG. 3  is side cut-away view of the table saw shown in  FIGS. 1-2  incorporating a safety mechanism and drive belt assembly according to one aspect of the disclosure, with the cutting blade in a first operating position. 
           [0014]      FIG. 4  is a side cut-away view of the table saw shown in  FIG. 3 , with the cutting blade in a second retracted position. 
           [0015]      FIG. 5  is a side cut-away view of the table saw shown in  FIG. 4 , with the cutting blade in a further retracted position. 
           [0016]      FIG. 6  is a perspective partial cut-away view of an undercarriage assembly with a riving knife assembly according to one aspect of the disclosure. 
           [0017]      FIG. 7  is a rear perspective view of the motor assembly and riving knife assembly depicted in  FIG. 6 . 
           [0018]      FIG. 8  is an enlarged view of the riving knife mounting assembly for the riving knife shown in  FIGS. 6-7 . 
           [0019]      FIGS. 9 and 10  are rear and front perspective views of the riving knife with the mounting assembly engaged to the knife according to one aspect of the disclosure. 
           [0020]      FIG. 11  is an exploded view of the riving knife and mounting assembly shown in  FIGS. 9-10 . 
           [0021]      FIGS. 12-14  are front, top and side views of the riving knife and mounting assembly shown in  FIGS. 9-11 . 
           [0022]      FIGS. 15   a ,  15   b  are perspective views of the riving knife and mounting assembly shown with the mounting assembly in the locked and unlocked positions, respectively. 
           [0023]      FIG. 16  is an enlarged perspective view of the mounting bracket for the riving knife mounting assembly depicted in the prior figures. 
           [0024]      FIG. 17  is an enlarged perspective view of the locking plate for the riving knife mounting assembly depicted in the prior figures. 
           [0025]      FIG. 18  is a side cross-sectional view of the mounting assembly engaged to the riving knife. 
           [0026]      FIG. 19  is a side cross-sectional view of the mounting assembly and riving knife shown in  FIG. 18 , depicting disengagement of the riving knife from the mounting assembly. 
           [0027]      FIG. 20  is a side view showing the relative orientation of the motor arm and the mounting assembly according to the disclosure. 
           [0028]      FIG. 21  is a top perspective view of the riving knife engaged to the mounting assembly disclosed herein. 
           [0029]      FIG. 22  is a top view of an alternative configuration to reduce riving knife play. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one skilled in the art to which this disclosure pertains. 
         [0031]    A power tool, and particularly a table saw  10  is shown in  FIGS. 1-2  that incorporates certain features disclosed herein. The table saw  10  includes a base  12  that is configured to be supported on a work surface and is further configured to enclose and contain the working components of the saw, as is conventional in the art. It is understood that the base  12  may be configured for portability, as shown in the figures, or may be a cabinet base that is kept in a generally fixed location. The base  12  supports a table  14  that provides the working surface  15  on which the workpiece is supported for the cutting/shaping operation. The table  14  defines a blade slot  16  for receiving a rotary saw blade  20 . A riving knife assembly  22  is supported above the saw blade and a blade guard  24  may be pivotably mounted to the riving knife. The riving knife and blade guard are conventional safety features to reduce the likelihood of injury to the tool operator and to help prevent the operator from moving his/her hands into the saw blade. 
         [0032]    A general schematic of the components of the table saw  10  is shown in  FIG. 3 . In particular, the table saw includes an undercarriage assembly  30  that includes an undercarriage component  34  configured to support the working components of the tool underneath the table  14 . The undercarriage assembly may be supported on the table by a pair of pivot brackets  36  that allow the assembly  30  as well as the saw blade  20  to be pivoted to a desired bevel angle, as is known in the art. An elevation and bevel mechanism  32  is provided that can be used to adjust the bevel angle (or the amount of pivot about the brackets  36 ) as well as the height of the saw blade  20  above the surface  15  of the table. For instance, the mechanism  32  may include a hand crank  43  that can be used to rotate elevation screw  44 . A nut  45  traverses the length of the elevation screw as the screw rotates. An elevation link  46  is mounted at one end to the elevation nut and at an opposite end to a drive assembly  42  that supports the saw blade. Thus, as the screw  44  is rotated in one direction the nut  45  advances toward the free end of the screw, which in turn moves the link  46  from the angled position shown in  FIGS. 4-5  to the generally perpendicular position shown in  FIG. 3 . The elevation mechanism can thus move the saw blade from the maximum height above the work surface  15  shown in  FIG. 3  to the maximum depth below the work surface shown in  FIG. 5 . 
         [0033]    As further shown in  FIGS. 4-5 , the table saw  10  includes a belt and arm drive assembly  42  that couples the saw blade  20  to a drive motor, as described herein. In one aspect of the disclosure, the belt and arm drive assembly  42  is pivotably mounted at a pivot axis  43  to the undercarriage  34  so that the entire assembly, including the saw blade, can pivot, as depicted in  FIGS. 4-5 . The drive assembly  42  is connected to a riving knife linkage assembly  60  that is configured to maintain the riving knife at a consistent distance from the saw blade  20 , even as the drive assembly and blade are pivoted between the maximum height and the maximum depth positions described above. 
         [0034]    According to one aspect of the disclosure, the table saw  10  of  FIGS. 1-3  may be provided with a riving knife mounting assembly  210  shown in  FIGS. 6-11  that allows efficient and intuitive engagement with the riving knife to mount the riving knife to the power tool in proper alignment and spacing relative to the saw blade. As shown in  FIG. 6 , the motor gear train  40  extending from motor  41  may include a motor arm  47  extending parallel to the saw blade (not shown) to provide a base for mounting the riving knife  22 . It is contemplated that the motor arm  47  may be part of the riving knife linkage assembly  60  described above, and in particular may constitute the horizontal link. The mounting assembly  210  is engaged to the motor arm  47  by a mounting bracket  212  and provides structure for engaging and clamping to the riving knife. A lever assembly  220  is provided within the housing  90  that allows the operator to unlock and lock the mounting assembly  210  as needed to adjust the position of the riving knife relative to the saw blade. As shown in  FIG. 8 , the mounting assembly includes a pair of mounting screws  214  that are threaded into corresponding bores in the motor arm  47 . The mounting assembly further includes an adjustment screw  217  that is operable to adjust the alignment of the riving knife with the saw blade, and an adjustment screw  219  that is operable to adjust the gap between the riving knife and the saw blade. 
         [0035]    As best shown in the exploded view of  FIG. 11 , the mounting bracket  212  of the riving knife mounting assembly  210  includes a mounting plate  213  that defines slotted openings  214   a  to receive the mounting screws  214 . The slotted openings are elongated in the lateral direction to allow the mounting bracket  212  to be adjusted laterally relative to the saw blade. The openings  214   a  may also be wider than the screws  214  to allow some forward-backward adjustment (i.e., parallel to the saw blade) to aid in providing a proper gap between the riving knife and the saw blade. The mounting plate  213  further defines a threaded bore  217   a  for receiving a threaded adjustment screw  217 . The set screw  217  may bear against a rib  48   a  ( FIG. 20 ) on the motor arm which allows the mounting bracket  212  to rock about the rib. The adjustment screw  217  bears against a boss  48   b  ( FIG. 20 ) on the motor arm to control the angular orientation of the plate  213  on the rib  48   a , and thereby accurately control the alignment of the riving knife relative to the saw blade. 
         [0036]    Another alignment screw  219  may be provided that is threaded into one of the two threaded bores  219   a  in the mounting plate  213 . The alignment screw  219  bears against the motor arm  47  to adjust the rocking position of the riving knife (i.e., the angular orientation in a plane parallel to the blade) to further assist in establishing a proper gap. It can be appreciated that the mounting bracket  212  is initially loosely engaged to the motor arm  47  by the mounting screws  214 . With the bracket loosely supported the adjustment screws  217 ,  219  can be adjusted to achieve the proper orientation and spacing of the riving knife. Once the adjustment screws have been set, the mounting screws  214  can be tightened to fix the mounting assembly  110  to the motor arm  47 . A locking nut  217   b  may be provided for the rocking movement adjustment screw  217 . 
         [0037]    As in a typical riving knife, the riving knife  22  includes an arcuate slot  23  for engagement with the mounting assembly  210  that allows adjustment of the angular position of the riving knife relative to the saw blade and to the workpiece being cut by the blade. Once the riving knife is positioned for use it is imperative that the knife be solidly locked so that it cannot come loose during operation of the power tool. The mounting assembly  210  thus includes a clamping plate  215  that is part of the mounting bracket  212  and a locking plate  216 , in which the two plates are configured to sandwich the riving knife therebetween, as depicted in  FIGS. 13-14 . The clamping plate and locking plate include generally planar surfaces  215   a ,  216   a  facing each other that bear against opposite sides of the riving knife  22 . As illustrated in the detail views of  FIGS. 16-17 , the clamping plate  215  defines a tab recess  252  and the locking plate  216  includes a tab  254  that extends from the plate. As best seen in  FIGS. 18 and 21 , the tab  254  extends through the slot  23  of the riving knife and into the recess  252  of the clamping plate. This tab-recess interface ensures proper alignment of the clamping plate  215  and locking plate  216 , and provides a further alignment feature for the riving knife by the close running fit between the tab  254  and the slot  23 . It can also be appreciated that the tab-recess interface helps hold the riving knife to the mounting assembly as the assembly is engaged to or adjusted relative to the motor arm  47 . 
         [0038]    The disclosure contemplates aspects of the mounting assembly  210  that facilitates and simplifies the locking and unlocking of the riving knife to the mounting assembly when the mounting assembly is fastened to the motor arm. Returning to  FIG. 11 , the mounting assembly  210  includes a lever assembly  220  that can be manually actuated to loosen or tighten the clamping and locking plates about the riving knife. The lever assembly  220  includes a locking shaft  222  that passes through a bore in the locking plate  216  and through the slot  23  to engage the clamping plate  215 . In one aspect, the locking shaft  222  includes a threaded post  223  that passes through an opening  225  in the clamping plate for engagement with a nut  223   a . The locking shaft  222  further includes a keyed portion  224  having one or more flats  224   a  that are configured to engage complementary configured surfaces of the opening  225  in the clamping plate  215 . As shown in  FIG. 16 , the opening  225  may be generally square to receive the keyed portion  224  and prevent relative rotation between the locking shaft and the clamping plate once the nut  223   a  has been tightened onto the threaded post  223 . 
         [0039]    Proper alignment of the riving knife to the mounting assembly may be maintained by locking bosses  250  ( FIG. 16 ) projecting from the clamping plate  215  toward the riving knife. The riving knife  22  includes corresponding pairs of openings  25  flanking the slot  23  ( FIG. 15   a ) that are sized to receive the locking bosses  250  when the riving knife is clamped to the mounting assembly. A plurality of the pairs of openings  25  may be provided along the length of the riving knife flanking the arcuate slot  22  corresponding to different angular positions of the riving knife relative to the saw blade. As shown in  FIG. 19 , the lever assembly must be in the unlocked position to allow the riving knife to disengage from the locking bosses  250 . In this unlocked position, pressure is maintained on the locking plate  216  by a spring arrangement  227 . In one embodiment the spring arrangement  227  includes facing bevel washers that are threaded onto the locking shaft  222 . The spring arrangement  227  is held between the locking plate  216  and a hub  226   b  of the locking shaft. When the locking shaft is tightened by the nut  223   a  the hub  226   b  may compress the spring arrangement  227  against the locking plate  216 , which in turn exerts a clamping force against the riving knife to clamp the riving knife against the clamping plate  215 . When the locking shaft  222  is loosened but not disengaged, pressure on the spring arrangement is reduced allowing the riving knife to be pivoted outward against the spring arrangement  227 , as illustrated in  FIG. 19 . 
         [0040]    In order to provide an intuitive and easily operated clamping mechanism, the lever assembly  220  is provided with a lever  230  having a hub  232  defining a bore  232   a  for receiving the hub  226   b  of the locking shaft  222 , as shown in  FIG. 11 . The lever hub  232  further defines an arcuate cam slot  234  that receives a cam pin  226 . The cam pin  226  is fixed within a bore  226   a  defined in the locking shaft hub  226   b . The cam pin is thus configured to ride within the cam slot  234  in the lever, or more precisely the cam pin interacts with the cam slot to translate rotation of the lever  230  to linear movement of the lever hub  232 . As illustrated in  FIG. 11 , the arcuate slot  234  extends from an unlocked baseline portion  234   a  to a locked baseline portion  234   b . The unlocked baseline portion  234   a  is positioned nearest the spring arrangement  227  while the locked baseline portion  234   b  is positioned farthest away from the spring arrangement with the lever  230  mounted on the locking shaft hub  226   b . The two baseline portions  234   a ,  234   b  are preferably generally horizontal to provide a resting position for the cam pin  226  that cannot be dislodged except by deliberate rotation of the lever  230 . The cam slot  234  thus provides an arcuate path between the two baseline portions so that rotation of the lever causes the cam slot to travel along the cam pin. 
         [0041]    When the cam pin  226  is positioned within the locked baseline portion  234   b , as illustrated in  FIG. 15   a , the hub  232  of the lever is at its closest position to the locking plate  216  so that the inner rim  232   b  of the hub exerts the maximum pressure against the spring arrangement  227 . In this position the riving knife is solidly locked in position on the mounting assembly  210 , as illustrated in  FIG. 18 . When the lever is rotated in the clockwise direction ( FIG. 15   a ), the cam slot rotates with the lever hub  232  until the cam pin  226  is positioned within the unlocked baseline portion  234   a , as illustrated in  FIG. 15   b . In this position, the lever hub  232  exerts a minimal pressure against the spring arrangement  227  so that the riving knife can be disengaged is desired, as depicted in  FIG. 19 . It can thus be appreciated that the lever assembly  220  provides an intuitive system for locking and unlocking the riving knife from the mounting assembly. Since the clamping and locking plates  215 ,  216  are always held together with the riving knife by the locking shaft  222 , there is little opportunity for misalignment of the riving knife after the mounting adjustments have been made and it is desired to clamp the riving knife in position. 
         [0042]    To enhance the intuitive feel for positive engagement of the riving knife to the mounting assembly, a shoulder screw  244  may be provided, as shown in  FIG. 18 , that passes through the riving knife slot  23  and that includes a threaded end  244   a  configured to engage a threaded bore  248  in the clamping plate  215 . The shoulder screw retains a biasing spring  246  between the head  244   b  of the shoulder screw and the locking plate  216 . The spring  246  maintains a continuous pressure on the locking plate  216  and thereby on the riving knife  22  toward the locking bosses  250 . This constant pressure allows the operator to move the riving knife slightly side-to-side until the bosses  250  fall into the openings  25  in the riving knife. The operator thus feels the engagement and is thus assured that the riving knife is properly positioned. 
         [0043]    In one modification, a U-shaped spring  262  may be mounted to bear on the outside of the clamping plate  215  and locking plate  216  as depicted in  FIG. 22 . A post  260  may be provided to fix the location of the leaf spring. In the manner of a cotter pin arrangement, the spring  262  may incorporate openings to receive the post. The post may have the configuration of the shoulder screw  244  described above. 
         [0044]    The present disclosure should be considered as illustrative and not restrictive in character. It is understood that only certain embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the disclosure are desired to be protected.