Patent Publication Number: US-2006005678-A1

Title: Table latch assembly for saws

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present application derives priority under 35 USC § 119(e) from U.S. Application Ser. No. 60/585,947, filed Jul. 7, 2004. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to a table latch assembly for a saw and more specifically to a table latch assembly for a combination table/miter saw.  
     BACKGROUND OF THE INVENTION  
      Typical combination table/miter saws have a table that is rotatable relative to a base assembly. It is an object of the invention to provide a table latch assembly for latching the table relative to the base.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, an improved table assembly is employed. The power tool has a base assembly, a table rotatably supported by the base assembly between two positions, a saw assembly supported by the table, wherein in the first position the saw assembly is movable from an upper position to a lower position towards the table and in the second position, the saw assembly is underneath the table, and a table latch assembly for latching the table in the first and second position, the table latch assembly preventing movement to the second position when, in the first position, the saw assembly is in the upper position.  
      Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below. 
    
    
     BRIEF 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 the table latch assembly according to the invention;  
       FIG. 3  is a side view of the cam plate of the table latch assembly of  FIG. 2 ; and  
       FIG. 4  is a side view of the lock plate of the table latch assembly of  FIG. 2 . 
    
    
     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 assembly  11  supported by base assembly  10 , and a saw assembly  20  supported by the table assembly  11 . Saw assembly  20  may include a trunnion  21  disposed on the table assembly  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 assembly  11  is pivotally attached to base assembly  10  via joint  15  so that, when the table assembly  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 assembly  11  to cut a workpiece placed on table assembly  11 .  
      On the other hand, when table assembly  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 assembly  11 . In such orientation, blade  23  extends through the table assembly  11 , so that a user can dispose a workpiece on table assembly  11  and push it towards blade  23  for cutting.  
      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 table latch assembly  40  that facilitates the movement of table assembly  11  to switch between the table saw and miter saw modes. Referring to  FIGS. 2-4 , the table latch assembly  40  may include a link  41  pivotally attached to base assembly  10 .  
      Link  41  may be sandwiched between base assembly  10  and holders  42 . Preferably, link  41  has a vertical portion  41 V so that link  41  can rotate about the longitudinal axis A of the vertical portion  41 V. Preferably axis A is substantially vertical.  
      Link  41  may have a portion  41 C that is connected to vertical portion  41 V. Portion  41 C may pivotably support a cam plate  43  and a lock plate  44 . Preferably cam plate  43  and lock plate  44  are pivotally attached to base assembly  10  via a shaft  45 , which may be captured unto base assembly  10  by screws  45 S.  
      Persons skilled in the art will recognize that, due to the rotational motion of vertical portion  41 V along axis A, link  41 , cam plate  43  and lock plate  44  are movable towards and away from base assembly  10 . Preferably springs  46  may be provided on base assembly  10  to contact cam plate  43  and/or lock plate  44  to bias link  41 , cam plate  43  and lock plate  44  away from base assembly  10 . Similarly, spring  47  may be provided on base assembly  10  to contact link  41  to bias link  41 , cam plate  43  and lock plate  44  away from base assembly  10 .  
      As shown in  FIG. 3 , cam plate  43  may have cam surfaces  43 C which may contact table assembly  11 . As table assembly  11  is moved between positions, such movement will push cam plate  43  towards base assembly  10 . The movement of cam plate  43  in turn causes the movement of lock plate  44  and link  41  towards base assembly  10 .  
      Referring to  FIGS. 1 and 3 , persons skilled in the art will recognize that saw  100  may be changed from miter saw mode ( FIG. 1A ) to table saw mode ( FIG. 1B ) by rotating table assembly  11  in the rotational direction X shown in  FIG. 1A . In such motion, a side edge on the front portion of table assembly  11  may contact the second uppermost cam surface  43 C shown in  FIG. 3 , moving lock plate  44  and link  41  towards base assembly  10 . As the rotational movement of table assembly  11  approaches 180 degrees, a side edge on the originally rear portion of table assembly  11  (and now becoming the front portion of table assembly  11 ) contacts the lowermost cam surface  43 C, as shown in  FIG. 3 , moving lock plate  44  and link  41  towards base assembly  10 .  
      Similarly, saw  100  may be changed from table saw mode ( FIG. 1B ) to miter saw mode ( FIG. 1A ) by rotating table assembly  11  in the rotational direction Y shown in  FIG. 1B . In such motion, the side edge on the originally rear portion and now front portion of table assembly  11  may contact the second lowermost cam surface  43 C shown in  FIG. 3 , moving lock plate  44  and link  41  towards base assembly  10 . As the rotational movement of table assembly  11  approaches 180 degrees, the side edge on the originally front portion of table assembly  11  (and now returning) contacts the uppermost cam surface  43 C shown in  FIG. 3 , moving lock plate  44  and link  41  towards base assembly  10 .  
      Preferably a trough  43 V will be provided between the uppermost cam surfaces  43 C and the lowermost cam surfaces  43 C. In this manner, when table assembly  11  moves towards trough  43 V (and possibly ride along the middle cam surfaces  43 C), springs  46  and/or  47  may push cam plate  43 , lock plate  44  and link  41  away from base assembly  10 .  
      Preferably, table assembly  11  is not captured by trough  43 V. Instead, base assembly  10  may have table stop assemblies  50 . Referring to  FIG. 2 , table stop assembly  50  may include a pad  51 , and a screw  52  attached to pad  51 and threadingly engaging base assembly  10  for adjusting the height of pad  51 . A nut  53  may be used to fix the location of screw  52  relative to base assembly  10 .  
      Table stop assemblies  50  may be disposed towards the front of saw  100  to stop rotation of table assembly  11  along direction Y. Similarly, table stop assemblies  50  which may be disposed towards the rear of saw  100  will preferably stop rotation of table assembly  11  along direction X. Persons skilled in the art will recognize that table stop assemblies  50  may be arranged and table assembly  11  may be shaped so that table stop assemblies  50  only contact those portions of table assembly  11  necessary to stop rotation and to avoid contact with other portions of table assembly  11  which may prevent the full rotation between modes.  
      Referring to  FIGS. 2 and 4 , lock plate  44  is used to prevent the undesired rotation of table assembly  11 . Lock plate  44  has a hook portion  44 H that overlaps table assembly  11  (see position shown in broken lines in  FIG. 4 ) to prevent it from moving in direction X unless such movement is desired. Hook portion  44 H forces the user to move link  41  (and thus hook portion  44 H) towards base assembly  10  in order to unlatch table assembly  11 .  
      As shown in  FIG. 1A , when saw  100  is in miter saw mode, the saw assembly  20  will preferably have its center of gravity CG behind joint  15  when saw assembly  20  is in an upper position, and in front of joint  15  when saw assembly  20  is in a lower position (shown in broken lines). Accordingly, if table assembly  11  were to be released when saw assembly  20  is in the upper position, table assembly  11  would pivot along direction.  
      It is desirable to prevent such rotation of table assembly  11 . Table assembly  11  may thus be provided with a hook portion  11 H, which is preferably below the workpiece supporting surface of table assembly  11 . If the user were to move link  41  towards base assembly  10  while saw assembly  20  was in the upper position, table assembly  11  would quickly rotate, catching hook portion  44 H with hook portion  11 H (see position of lock plate  44  shown in solid line in  FIG. 4 ). Such engagement would stop the rotation of table assembly  11 .  
      To avoid such engagement, the user is preferably forced to move saw assembly  20  to the lower position and lock saw assembly  20  in such position. Because the center of gravity CG of saw assembly  20  is now in front of joint  15 , table assembly  11  does not rotate when released. If anything, table assembly  11  is biased away from hook portion  44 H due to the relation of center of gravity CG relative to joint  15 . Persons skilled in the art will recognize that at least one table stop assembly  50  will prevent further rotation of table assembly  11  even with such bias.  
      In such situation, when the user moves link  41 , lock plate  44  is moved from the position shown in broken lines in  FIG. 4  to the position shown in dots and dashes. The user&#39;s movement of link  41  and/or the interaction of table assembly  11  with cam surface  43  may further move lock plate  44  to the position shown in dots in  FIG. 4 , thus completely clearing table assembly  11  and allowing the user to rotate table assembly  11 .  
      Persons skilled in the art will recognize that lock plate  44  has two cam surfaces  44 C that function in a manner similar to cam surfaces  43 C to assist in the movement of cam plate  43 /lock plate  44 /link  41 .  
      Referring to  FIGS. 1-2 , link  41  may have a handle  41 H to enable the user to move link  41  (and thus lock plate  44 ) towards base assembly  10 . Handle  41 H may extend through a housing  60  supporting an on/off switch (not shown).  
      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.