Patent Publication Number: US-2006011034-A1

Title: Riving knife assembly for table saws

Description:
REFERENCE TO CROSS-RELATED APPLICATION  
      The present application derives priority under 35 USC 119(e) from U.S. patent application Ser. No. 60/587,622, filed Jul. 13, 2004. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to a riving knife assembly for table saws and more specifically to a riving knife assembly for a combination table/miter saw.  
     BACKGROUND OF THE INVENTION  
      It is well known in the table saw field to provide a riving knife assembly behind the table saw blade. Typically the riving knife assembly is difficult to remove from the table saw. Accordingly, it is an object of the invention to provide an enhanced riving knife assembly.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, an improved support assembly is employed. The power tool has a base assembly, a table supported by the base assembly, a saw assembly supported by the table, and a riving knife assembly attached to the saw assembly, the riving knife comprising a body having an edge placed adjacent to a blade, and a bracket connected to the body, wherein the bracket is inserted into a support assembly disposed on the saw assembly.  
      Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below. 
    
    
     DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings illustrate preferred embodiments of the invention according to the practical application of the principles thereof, and in which:  
       FIG. 1  illustrates a combination table/miter saw according to the invention, whereas  FIGS. 1A-1B  are side views of the combination table/miter saw in the miter saw and table saw modes, respectively;  
       FIG. 2  is a perspective view of a riving knife assembly according to the invention;  
       FIG. 3  is a partial perspective view along line III-III of  FIG. 2 ;  
       FIG. 4  is a perspective view of the riving knife assembly stored in the combination table/miter saw;  
       FIG. 5  is a partial perspective view of a blade guard assembly installed unto the riving knife assembly; and  
       FIG. 6  is a partial cross-sectional view of the blade guard and riving knife assemblies along a center plane of the body of the riving knife assembly. 
    
    
     DETAILED DESCRIPTION  
      The invention is now described with reference to the accompanying figures, wherein like numerals designate like parts. Referring to  FIG. 1 , a combination table/miter saw  100  may include a base assembly  10 , a table  11  supported by base assembly  10 , and a saw assembly  20  supported by the table  11 . Saw assembly  20  may include a trunnion  21  disposed on the table  11 , a pivotable arm  22  pivotably attached to trunnion  21 , a motor  24  supported by the arm  22  and driving a blade  23 . Arm  22  also supports upper blade guard  27 , which covers an upper part of blade  23 . Lower blade guard  25  is pivotally attached to upper blade guard  27 . An auxiliary blade guard  26  may be pivotably connected to lower blade guard  25 .  
      Preferably, table  11  is pivotally attached to base assembly  10  via joint  15  so that, when the table  11  is in the orientation of  FIG. 1A , the saw assembly  20  can act as a miter saw, i.e., saw assembly  20  can be pivoted downwardly towards table  11  to cut a workpiece placed on table  11 .  
      On the other hand, when table  11  is rotated via joint  15  to the orientation of  FIG. 1B , the saw  100  acts as a table saw, i.e., saw assembly  20  will be supported by and disposed underneath the table  11 . In such orientation, blade  23  extends through the table  11 , so that a user can dispose a workpiece on table  11  and push it towards blade  23  for cutting.  
      Persons skilled in the art will recognize that the invention described below can be applicable to non-combined table saws.  
      Preferably, base assembly  10  has at least one wheel  13  thereon.  
      Base assembly  10  may also support four leg assemblies  30 . Preferably leg assemblies  30  are pivotally attached to base assembly  10 .  
      Because the saw  100  can be used as either a table saw or a miter saw, it is preferable to provide a riving knife assembly  50  which can be easily installed when saw  100  is to be used as a table saw and easily removed when saw  100  is to be used as a miter saw.  
      Referring to  FIGS. 2-5 , riving knife assembly  50  comprises a main body  51 , with a curved blade edge  51 B which will be placed adjacent to blade  23 .  
      A bracket  52  is connected to main body  51 . Bracket  52  can be inserted into a slot of support assembly  56 . A thumbscrew  57  is threadingly engaged to support assembly  56 . With such construction, a user would lift lower blade guard  25 , allowing the user to insert bracket  52  into the slot  56 S. The user can then lock the bracket  52  (and thus riving knife assembly  50 ) in place by rotating thumbscrew  57 , which pushes bracket  52  into locking contact with support assembly  56  and/or upper blade guard  27 .  
      A spring  58  may be disposed between the knob of thumbscrew  57  and support assembly  56 . Spring  58  preferably prevents thumbscrew  57  from unscrewing due to vibration, such as when riving knife is not in place.  
      Preferably support assembly  56  has upper and lower walls  59 , which form a tapered joint with bracket  52 . The mating surfaces of bracket  52  and walls  59  may also be beveled, creating a dovetail junction as well. Such tapered junction will automatically locate the riving knife assembly  50  along the vertical and horizontal axes.  
      The area between walls  59  (of support assembly  56  and/or upper blade guard  27 ) is preferably machined. When thumbscrew  57  is tightened, the bracket  52  is pushed into such machined area along a third axis. Such arrangement preferably ensures that the riving knife assembly  50  is disposed in the same position every time it is installed unto saw  100 , thus eliminating the need for readjustment.  
      Persons skilled in the art will recognize that it is desirable to place blade edge  51 B relatively near blade  23 . Accordingly, it is preferable to make blade edge  51 B adjustable relative to bracket  52  so that, when bracket  52  is inserted into support assembly  56 , blade edge  51 B is in the desired position. Persons skilled in the art will recognize that body  51  can be connected to bracket  52  via screws  54 , and that adjustability can be provided by providing slots on body  51  and/or bracket  52  so that screws  54  can move along such slots.  
      Alternatively, a plate  53  can be sandwiched between body  51  and bracket  52 . Adjustability can be provided by providing slots on body  51 , bracket  52  and/or plate  53 , so that screws  54  can move along such slots. Preferably, body  51  can move relative to bracket  52  along axes A and/or B. Preferably, slots are provided in body  51  and bracket  52 . Screws  54  go into plate  53  through said slots. Said slots are preferably perpendicular to each other and thus provide independent adjustment in their respective axes.  
      It is preferable to provide a place to store riving knife assembly  50 . Referring to  FIGS. 1 and 4 , base assembly  10  may have bosses  12  to receive riving knife assembly  50  thereon. Rotatable retainers  11  with protrusions  11 R may be pivotally attached to base assembly  10 . Preferably, a retainer  11  can be moved between a first position where protrusion  11 R overlaps riving knife assembly  50  (as shown in solid lines in  FIG. 4 ), thus holding it in place, and a second position where protrusion  11 R does not overlap riving knife assembly  50  (as shown in broken lines in  FIG. 4 ), thus allowing a user to remove riving knife assembly  50  from base assembly  10 .  
      Persons skilled in the art will recognize that that other means of retaining the riving knife assembly  50  in place, such as spring clips or magnets, could be substituted for retainer  11  and are considered to be equivalents of the present invention.  
      Persons skilled in the art will recognize that it may be advantageous to provide a blade guard assembly  60  that can be installed unto riving knife assembly  50 . Referring to  FIGS. 1 and 5 - 6 , blade guard assembly  60  comprises a body  61 , which is preferably substantially hollow, with a dust exhaust  62  connectable to a vacuum hose for extracting dust and chips generated during the cutting operation.  
      Body  61  may have two split portions  61 E at one end thereof for receiving body  51  of riving knife assembly  50 . A bolt  63  extends through both split portions  61 E. A thumbscrew  64  may be provided at the end of the bolt  63  for sandwiching the portion of body  51  inserted between split portions  61 E. Body  61  may also have a boss  65  disposed underneath bolt  63 .  
      Preferably body  51  of riving knife assembly  50  has a substantially perpendicular slot  51 S and an arcuate slot  51 AS disposed adjacent to slot  51 S. Persons skilled in the art will recognize that bolt  63  and boss  65  are preferably received by slots  51 S,  51 AS, respectively. Accordingly, it is desirable to ensure that the distance between slots  51 S and  51 AS are substantially similar to the distance between bolt  63  and boss  65 .  
      Preferably, boss  65  has a screw that goes through the boss  65  and threadingly engages a hole in the body  61  on the opposite side. This increases the strength of boss  65 .  
      With such arrangement, the user would insert bolt  63  into slot  51 S (thus disposing body  61  unto body  51 ). Boss  65  would be automatically disposed in or near arcuate slot  51 AS. The user would then rotate body  61  about bolt  63  so that boss  65  moves along arcuate slot  51 AS, until a desired position is reached or boss  65  contacts the end of arcuate slot  51 AS. The user can then lock blade guard assembly  60  by rotating thumbscrew  64 .  
      Persons skilled in the art may recognize other additions or alternatives to the means disclosed herein. However, all these additions and/or alterations are considered to be equivalents of the present invention.