Patent Publication Number: US-8117953-B2

Title: Stop rule with hold-down device for circular saw benches

Description:
FIELD OF THE INVENTION 
     The present invention relates to a stop rule having a holddown for table saws. More particularly, the present invention relates to a stop rule for table saws, which includes a hollow profile that extends in a longitudinal direction and that has a guidance limb extendable from one side. 
     BACKGROUND OF THE INVENTION 
     Applicant&#39;s DE-B 10 2005 024 111 (US 2008/0092707) discloses a stop rule for table saws that can be used in both an upright and a laid-down position, so that, in addition to tall workpieces, low and narrow workpieces can also be processed. In the latter case, the risk exists that the workpieces may lose their contact with the saw table in the region of the saw blade and deviate upward, which can result not only in inaccuracy and improper processing, but also in accidents. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a remedy to the above defined problem and to configure a stop rule so that narrow and low workpieces can be held at their free ends so that they cannot move away from the saw table during processing. 
     In order to achieve this object, according to the invention a vertically displaceable holddown, which is fastened on a horizontal support surface of the lateral extension of the stop rule when in the laid-down position, is attached to the stop rule. 
     The holddown is preferably made up of a profiled bar having a limb that protrudes vertically upward, which limb is fastened via a scissor linkage on the horizontal support surface of the extension or on a baseplate of the holddown, which baseplate can in turn be fastened removably on the support surface. 
     The essential advantage of the invention is the fact that the stop rule is equipped with a holddown that, principally thanks to the scissor linkage, is of such compact construction that it can be accommodated on the relatively narrow support surface of the stop rule and also requires little installation space vertically. The holddown can be an integral constituent of the stop rule or can be fastened via its baseplate removably on the rule&#39;s support surface. The scissor linkage is braced against the support surface and baseplate via elastic return means. The return means are preferably made of leaf springs, which likewise require little space. 
     Immobilization of the scissor linkage in its compression position resting on the workpiece is achieved by a catch lever that extends parallel to the vertical limb of the profiled bar and is fixedly connected to the articulation axis of the scissor linkage, the articulation axis having a thread that clamps the two levers of the scissor linkage against one another in the immobilized position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention are evident from the description below of exemplifying embodiments that are depicted in the drawings, in which: 
         FIG. 1  is a perspective view of a stop rule having an integrated holddown, according to the invention; 
         FIG. 2  is a perspective rear view of the holddown at an enlarged scale; 
         FIG. 3  is a rear view axonometrically depicting the holddown; 
         FIG. 4  is a plan view of the holddown; 
         FIG. 5  shows a variant of  FIG. 3 ; 
         FIG. 6  shows the removable holddown of  FIG. 5 ; and 
         FIG. 7  is a partly sectioned depiction of a securing screw at enlarged scale. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
       FIG. 1  shows a stop rule  10  that is embodied similarly to the stop rule in accordance with DE-B 10 2005 024 111 (US 2008/0092707) and that can be fastened on a saw table  12  of a table saw, where it serves for the guidance of bar-shaped workpieces. 
     Stop rule  10  is made up of a hollow profile  14  that extends in a longitudinal direction and has a substantially rectangular or square cross section with a central cavity  16  and a smaller lateral cavity  18 . Embodied on hollow profile  14 , in known fashion, are profile grooves  20 ,  20 ′ that serve for the engagement of fastening means (not further depicted) on saw table  12 . 
     One side of hollow profile  14  is embodied as a guidance limb  22  having an extension  24 , protruding in coplanar fashion, that comprises at its front edge a guidance rule  26  for low workpieces. Small cavity  18  is embodied in extension  24  that protrudes laterally from hollow profile  14 . With stop rule  10  in the laid-down position shown in  FIG. 1 , guidance limb  22  rests on saw table  12  so that guidance rule  26  protrudes at right angles upward from saw table  12 . 
     Supported in larger cavity  16 , having a rectangular or square cross section, is a slide (not shown) that can be shifted, by means of a slider  28  having a handle  30 , in the longitudinal direction of stop rule  10 . Further details thereof are presented and explained in DE-B 10 2005 024 111 (US 2008/0092707). By way of slider  28 , which engages into a passthrough groove  32 , a follower finger  34  can be shifted in a longitudinal groove  35  of guidance rule  26  in order to advance a low workpiece on saw table  12  when stop rule  10  is in the laid-down position. 
     In the exemplifying embodiment of  FIGS. 1 to 4 , stop rule  10  is equipped with an integrated holddown  36  that is fastened on horizontal support surface  38  of laterally protruding extension  24 . Holddown  36  is made up of an approximately Z-shaped profiled bar  40  that is associated with the front (in the advance direction) part of stop rule  10 . Profiled bar  40  has a vertically upwardly protruding limb  42  that is fastened via a scissor linkage  44  on horizontal support surface  38  of extension  24 . Projecting from the lower edge of vertical limb  42  is an angled bar  46  having a downwardly protruding contact bar  48 , as is evident from  FIG. 2 . Contact bar  48  is arranged at a very small distance in front of guidance rule  26 , so that even very narrow workpieces can be grasped and processed. 
     Scissor linkage  44  is assembled from two levers  50  that are interconnected via an articulation axis  52  indicated schematically in  FIG. 2 . The upwardly facing ends of the two levers  50  are articulated onto vertical limb  42  of holddown  36 . A left (in  FIGS. 2 and 3 ) articulation point  54  serves this purpose for the one lever  50 , while an elongated hole  56  is provided for the other lever  50  on the right side. 
     Because scissor linkage  44 , as a result of the above-described articulation points on profiled bar  40  visible especially in  FIG. 3 , does not project above the upper edge of vertical limb  42 , the overall vertical height is also sufficiently limited that stop rule  10  can be used without restrictions even in its upright position, in which guidance limb  22  stands vertically on saw table  12 . 
     The lower ends of the two levers  50  of scissor linkage  44  are each braced in a bearing bracket  58  that is fastened on horizontal support surface  38 . As is apparent from  FIG. 3 , one of the two levers  50  is in turn supported in pivotably movable fashion in the associated bearing bracket  58  via a fixed articulation pin  60 , whereas the other lever  50  is supported with its articulation pin  60 ′ shiftably in an elongated hole  62 . 
       FIG. 3  further shows that a leaf spring packet  64  is fastened in each bearing bracket  58 , the free end  66  of said packet engaging on the underside of the associated lever  50  of scissor linkage  44 . 
     A catch lever  68 , which extends parallel to vertical limb  42  of profiled bar  40 , is provided in order to immobilize scissor linkage  44  in the compression position of holddown  36  resting on the workpiece. One end of catch lever  68  is fixedly connected to articulation axis  52  of scissor linkage  44 , said articulation axis  52  having a thread (not further depicted), known per se, that in the immobilizing position clamps the two levers  50  of scissor linkage  44  against one another. 
     As  FIG. 4  shows, the free end of catch lever  68  is angled with respect to vertical limb  42  so that it can be grasped manually, in the narrow space between vertical limb  42  and the oppositely located vertical wall  70  of hollow profile  14  (see  FIG. 1 ), in order to pivot catch lever  68  out of its disengaged position into the immobilized position and vice versa. The angled free end of catch lever  68  is equipped with a grip recess  72  (see  FIG. 2 ). 
     Fastened on the upper edge of vertical limb  42  of profiled bar  40  is a pressure plate  74 , with which profiled bar  50  can be displaced downward by thumb pressure, against the spring force, in order to press contact bar  48  against the workpiece. Holddown  36  is locked in this position by actuating catch lever  68 . During sawing, the workpiece is advanced to the saw blade via follower finger  34 , which passes through under the lower edge of contact bar  48 . To release holddown  36 , catch lever  68  is pivoted back into its disengaged position in which leaf springs  64  then, via scissor linkage  44 , raise profiled bar  40  into its initial position. 
     In the variant shown in  FIGS. 5 and 6 , holddown  36  is fastened removably on support surface  38  of stop rule  10  so that it can be removed quickly when the table saw blade is set obliquely. Holddown  36  has for this purpose a horizontal baseplate  76  from which the two bearing blocks  58 , which are embodied integrally therewith, protrude upward. The two leaf spring packets  64  are each fastened in a cutout of baseplate  76  beneath the associated bearing block  58 , specifically by means of a hex socket screw  78  whose threaded portion is screwed into a centering pin  80 . Two lossproof securing screws  82 , one of which is depicted in  FIG. 7 , serve to fasten baseplate  76 , and thus holddown  36 , on support surface  38 . It is evident here that securing screw  82  is made up of a sleeve  86  that is screwed, with a threaded shaft  88 , into a threaded orifice of baseplate  76 . Arranged in vertically movable fashion in sleeve  86  is a flanged stud  90  whose threaded end  92  is screwed into a threaded orifice of extension  24  of guidance limb  22  when holddown  36  is in the installed position. The upper end of flanged stud  90  is fastened in a knurled nut  94 , e.g. adhesively bonded therein. When securing screw  82  is loosened, it can be raised only until its flange  96  comes to a stop against an internal shoulder  98  of sleeve  86 . 
     With holddown  36  in the installed state, the two centering pins  80  engage into corresponding centering orifices of support surface  38 . 
       FIGS. 5 and 6  show that two resilient end stop elements  100  made of polyamide, which prevent catch lever  68  from impacting sharply onto baseplate  76  or onto support surface  38 , are fastened on baseplate  76 . 
     Lastly, it is indicated in  FIGS. 1 and 6  that a step  84  is machined into one part of the upper edge of vertical limb  42  of profiled bar  40 ; when stop rule  10  is in the upright position, handle  30  can be introduced into this step if follower finger  34  needs to be shifted as far forward as possible.