Patent Publication Number: US-2006005683-A1

Title: Depth control mechanism for table saw

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      The present application derives priority under 35 USC § 119(e) from U.S. Application Ser. No. 60/688,401, filed Jul. 7, 2004. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to a depth control mechanism for a table saw and more specifically to a depth control mechanism for a combination table/miter saw.  
     BACKGROUND OF THE INVENTION  
      Typical table saws have a depth control mechanism to change the height of the blade relative to the table. It is an object of the invention to provide a depth control mechanism that is usable in combination table/miter saws.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, an improved power tool with a depth control mechanism is employed. The power tool has a base assembly, a table supported by the base assembly, a saw assembly pivotably supported by the table via a trunnion, a link attached to the saw assembly, and a shaft threadingly engaged to the link, wherein the shaft is engagable to the trunnion, so that, when the shaft is engaged to the trunnion, the saw assembly is pivoted relative to the trunnion when the shaft is rotated.  
      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; and  
       FIG. 2  is a side view of the depth control mechanism according to the invention;  
       FIG. 3  is a partial exploded view of a component of the depth control mechanism of  FIG. 2 ; and  
       FIG. 4  illustrates a down stop assembly according to the invention, where  FIGS. 4A-4B  are side views of the down stop assembly when in the miter saw and table saw modes, respectively. 
    
    
     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 assembly  21  disposed on the table  11 , a pivotable arm  22  pivotably attached to trunnion assembly  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 .  
      It is preferable to provide a means for adjusting the depth of blade  23  when saw  100  is in table saw mode that does not substantially affect the chopping motion when saw  100  is in miter saw mode. The depth control mechanism  40  shown in  FIGS. 2-3  will meet such requirement.  
      Depth control mechanism  40  may include a link  41  pivotally attached to arm  22  via pivot joint  41 P. Link  41  may have a threaded portion.  
      Link  41  may be made of aluminum. Preferably, link  41  carries a threaded bushing  42 . Bushing  42  may be sandwiched between link  41  and a plate  42 P. Plate  42 P is attached to link  41  via screws  42 S. Bushing  42  may be made of steel.  
      A shaft  43  may be threadingly engaged to bushing  42  and/or to link  41 . Shaft  43  may have a threaded portion  43 S to threadingly engage bushing  42 . Shaft  43  may have a handle  45  for rotating shaft  43  relative to bushing  42 .  
      Persons skilled in the art will recognize that, when shaft  43  is rotated, shaft  43  will move axially along its longitudinal axis. Shaft  43  may have a shoulder  43 SS adjacent to the threaded portion  43 S and a nut  43 SN threadingly engaged to threaded portion  43 S to limit the range of movement along the longitudinal axis of shaft  43 .  
      A sleeve  44  may be rotatably disposed on shaft  43 . Bearings  43 B may be disposed between sleeve  44  and shaft  43 . Sleeve  44  may have at least one protrusion  44 P.  
      Trunnion  21  may have at least one (and preferably two) arm(s)  21 A with slot(s)  21 AS. Protrusion(s)  44 P are received in slot(s)  21 AS.  
      A latch  21 L may be pivotally attached to one arm  21 A. Latch  21 L may have a hook portion  21 AH to capture protrusion  44 P in slot  21 AS. Preferably latch  21 L may be pivoted between a capture position capturing protrusion  44 P and an open position not capturing protrusion  44 P. A spring (not shown) preferably biases latch  21 L towards the capture position.  
      With such arrangement, when changing the mode of saw  100  from miter saw mode to table saw mode, the user moves the shaft  43  downwardly so that protrusion  44 P is in slot  21 AS. Latch  21 L may have an inclined surface  21 LC, so that when protrusion  44 P is moved into latch  21 L, contact between protrusion  44 P and surface  21 LC cause latch  21 L to move towards the open position. When protrusion  44 P is in slot  21 AS, the spring will cause latch  21 L to return to the capture position.  
      The user can then pivot table  11  to change the mode of saw  100 . Referring to  FIG. 1B , handle  45  will be towards the front of saw  100 , accessible by the user. In order to adjust the height of blade  23  relative to table  11 , the user needs to rotate handle  45 .  
      As handle  45  is rotated, shaft  43  rotates. Due to the engagement between threaded portion  43 S and bushing  42 , shaft  43  will move along its longitudinal axis relative to bushing  42 . Because the position of one end of shaft  43  is fixed (at protrusion  44 P), the movement of shaft  43  relative to bushing  42  will cause the distance between protrusion  44 P and bushing  42  to vary. Because bushing  42  is part of link  41 , which in turn is connected to arm  22 , arm  22  will move relative to trunnion  21 . Because arm  22  is part of saw assembly  20 , which includes blade  23 , blade  23  will move relative to table  11 .  
      A compression spring  46  may be pivotally attached to link  41  at one end and to arm  22  at the other end at a point between pivot point  41 P and bushing  43 . Such compression spring  46  will maintain link  41  (and shaft  43 ) in an upper position (shown in solid lines in  FIG. 2 ) so that saw assembly  20  can be pivoted downwardly for chopping a workpiece when saw  100  is in miter saw mode, and a lower position (shown in broken lines in  FIG. 2 ) for use to control the depth of blade  23  when saw  100  is in table saw mode, as explained above. Persons skilled in the art will recognize that compression spring  46  should be strong enough to maintain link  41  and shaft  43  in the upper position against the force of gravity, but not strong enough that a user cannot move shaft  43  to the lower position.  
      Referring to  FIG. 4 , link  41  may have a leg  41 L. Trunnion  21  may have a stop surface  21 SS which contacts leg  41 L to limit the downward motion of the saw assembly  20  during the chopping operation. Person skilled in the art will recognize that leg  41 L and stop surface  21 SS in effect provide a down stop assembly when saw  100  is in the miter saw mode.  
      As shown in  FIG. 4A , when saw  100  is in miter saw mode, the saw assembly  20  (and link  41 ) will be in an upward position (as shown in broken lines). When saw assembly  20  is pivoted downwardly in a chopping action, leg  41 L will contact stop surface  21 SS, thus limiting the range of downward motion.  
      As shown in  FIG. 4B , when saw  100  is in table saw mode, protrusion  44 P will be captured by latch  21 L. In such position, leg  41 L will bypass (and not contact) stop surface  21 SS, allowing a greater degree of travel so that more of blade  23  can extend through the table  11  for a greater depth of cut.  
      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.