Patent Publication Number: US-2006011038-A1

Title: Miter lock assembly for miter saws

Description:
REFERENCE TO CROSS-RELATED APPLICATION  
      The present application derives priority under 35 USC § 119(e) from U.S. Patent Application No. 60/587,621, filed Jul. 13, 2004. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to a miter lock assembly for a miter saw and more specifically to a miter lock assembly for a combination table/miter saw.  
     BACKGROUND OF THE INVENTION  
      Typical miter saws have a table that is rotatable relative to a base assembly. Typically, miter lock assemblies extend below the workpiece supporting surface of the table. Unlike typical miter saws, the table of a combination table/miter saw is used on both sides thereof. Accordingly, it is an object of the invention to provide a miter lock assembly that can be used when the combination table/miter saw is in miter saw mode, and that does not block the movement of a workpiece along the table when the combination table/miter saw is in table saw mode.  
     SUMMARY OF THE INVENTION  
      In accordance with the present invention, an improved miter lock assembly is employed. The power tool has a fixed table, a rotatable table rotatably disposed on the fixed table, a saw assembly supported by the rotatable table, and a miter lock assembly comprising a housing attached to the rotatable table, and a knob engaging the housing, wherein the location of the rotatable table relative to the fixed table is locked when the knob is moved along a direction substantially perpendicular to at least one of the fixed table and the rotatable table.  
      Another feature of the invention calls for a power tool has a base assembly, a fixed table rotatably connected to the base assembly, a rotatable table rotatably disposed on the fixed table, a saw assembly supported by the rotatable table, and a miter lock assembly attached to the rotatable table, wherein the fixed table is movable between a first position where the saw assembly is above the fixed table and a second position where the saw assembly is below the fixed table. The fixed table may have a workpiece support surface for supporting a workpiece when the fixed table is in the second position. The miter lock assembly is preferably substantially coplanar with or below the workpiece support surface when the fixed table is in the second 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  illustrates a miter lock assembly according to the invention, whereas  FIGS. 2A-2B  are top and bottom plan views, respectively;  
       FIG. 3  is a partial cross-sectional view along line III-III of  FIG. 2A ; and  
       FIG. 4  is a partial cross-sectional view along line IV-IV of  FIG. 2A . 
    
    
     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.  
      Persons skilled in the art will recognize that the invention described below can be applicable to non-combined miter 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 table assembly  11  which can support a workpiece on both sides of table assembly  11 . Referring to  FIG. 2 , table assembly  11  comprises a fixed table  16  which is connected to joint  15 , and a rotatable table  17  rotatably disposed on fixed table  16 . Persons skilled in the art will recognize that saw assembly  20  will be preferably disposed on rotatable table  17  so that saw assembly  20  can be mitered when in the miter saw mode. Rotatable table  17  may have a kerf opening  17 K to allow blade  23  to extend therethrough.  
      As shown in  FIGS. 1-4 , a miter lock assembly  40  can be used to fix the rotational position of rotatable table  16  relative to fixed table  17 . Miter lock assembly  40  preferably includes a housing  41  attached to rotatable table  17  via screws  17 S. Housing  41  may be made of aluminum.  
      Miter lock assembly  40  may also include a knob  42 K overmolded on a screw  42 S. As discussed below, it is preferable that screw  42 S be substantially hollow. Screw  42 S may be made of steel. Screw  42 S may threadingly engage a threaded portion  41 S of housing  41 . Preferably threaded portion  41 S is a steel insert disposed in housing  41 .  
      Screw  42 S may contact a bracket  43 . Bracket  43  may be loosely trapped by a screw  43 S, which in turn may be threadingly engaged to housing  41 . Bracket  43  is substantially L-shaped. When screw  42 S is moved downwardly, it contacts bracket  43 , forcing bracket  43  to rotate towards a raised portion  16 R and/or a flange  16 F of fixed table  16 .  
      Bracket  43  may be connected to a contact pad  44 . Contact pad  44  may be made of plastic and may have a flange  44 F that is captured by a screw  44 S threadingly engaging a boss  44 S. Flange  44 F is slidingly disposed on screw  44 S.  
      It may be preferable to cover part of housing  41  with a plate  49  to diminish the amount of dust entering the area with the link  48 L, lever  46 , bracket  43 , etc. Plate  49  may be fixed to housing  41  via screw  44 S threadingly engaging boss  41 B and/or other screws threadingly engaging bosses  49 B. As shown in  FIG. 4 , plate  49  may extend underneath flange  16 F. Such arrangement may prevent housing  41  from being pulled off fixed table  16  and/or rotatable table  17 .  
      Referring to  FIGS. 1 and 4 , plate  49  is the lowest part of miter lock assembly  40 . When saw  100  is used in table saw mode, plate  49  and miter lock assembly  40  are not higher than the workpiece supporting surface of table  11 , as to not block or impair the motion of a workpiece into blade  23 . Plate  49  may be substantially coplanar with or below the workpiece supporting surface of table  11 .  
      Plate  49  may also fix the rotational position of rotatable table  17  relative to fixed table  16 . When screw  42 S is rotated and moved downwardly, it contacts bracket  43 , forcing bracket  43  to move towards flange  16 F. Such movements lifts housing  41  relative to fixed table  16 , causing plate  49  to contact the underside flange  16 F, locking miter lock assembly  40  (and thus rotatable table  17 ) relative to fixed table  16 .  
      Persons skilled in the art will recognize that screw  42 S is moved towards the locking position in a direction substantially perpendicular to fixed table  16  and/or rotatable table  17 . Persons skilled in the art will also recognize that plate  49  is lifted towards flange  16 F and to the locking position when knob  42 K is moved in a direction substantially perpendicular to fixed table  16  and/or rotatable table  17 . Such result can also be achieved through other means, where screw  42 S is replaced by a non-threaded shaft, etc.  
      Housing  41  may also support a miter detent assembly. Such detent assembly preferably includes a spring  45 . Spring  45  may be made of steel plate. Spring  45  may be fixedly attached to housing  41  via screws  45 S.  
      Spring  45  may have a detent protrusion  45 D. Detent protrusion  45 D preferably engages notches  18 N disposed on a detent plate  18 . Detent plate  18  may be disposed on raised portion  16 R.  
      Detent plate  18  may have said notches  18 N at predetermined common miter positions, such as 0 degrees, 45 degrees, etc. Detent plate  18  may also have indicia  181  to indicate the rotational position of rotatable table  17  relative to fixed table  16 .  
      Detent plate  18  may have slots  18 SS for receiving screws  18 S therethrough. With such arrangement, the user can loosen screws  18 S, adjust detent plate  18  to accurately show the rotational position of rotatable table  17  relative to fixed table  16 , and tighten screws  18 S, locking detent plate  18  in place.  
      Persons skilled in the art will recognize that detent protrusion  45 D may be moved between a first position engaging notch  18 N and a second position not engaging notch  18 N. Spring  45  preferably biases detent protrusion  45 D towards the first position.  
      Detent protrusion  45 D may be moved to the second position via a detent override  48 . Detent override  48  may include a button  48 B connected to a link  48 L. Preferably button  48 B is disposed within knob  42 K.  
      As mentioned above, screw  42 S is preferably hollow. This allows link  48 L to extend through screw  42 . Link  48 L may also extend through bracket  43 .  
      Link  48 L may be engaged to a lever  46  at one end. Lever  46  is preferably pivotably connected to housing  41 . The other end of lever  46  preferably contacts spring  45  and/or detent protrusion  45 D. Lever  46  may have two protrusions  46 P along its rotational axis. Protrusions  46 P are captured within ribs  41 R of housing  41 . Screws  47 S preferably capture protrusions  46 P (and lever  46 ). A spring  47  biases lever  46  (and protrusions  46 P) towards screws  47 S.  
      Persons skilled in the art may recognize that lever  46  may be constructed by inserting a pin therethrough. The ends of the pin which protrude from lever  46  would constitute protrusions  46 P.  
      With such arrangement, the user can move detent protrusion  45 D towards the second position (and allow the rotational movement of rotatable table  17  relative to fixed table  16 ) by pushing button  48 B downwardly, thus moving link  48 L downwardly, causing lever  46  to rotate and lift detent protrusion  45 D.  
      A spring  48 S may be disposed between button  48 B and knob  42 K. Persons skilled in the art will recognize that it is preferable to capture button  48 B within knob  42 K. With such arrangement, spring  48 S will bias button  48 B away from knob  42  and thus bias link  48 L upwardly, allowing detent protrusion  45 D to be biased towards the first position and/or engaged to detent notch  18 N.  
      Persons skilled in the art will also recognize that, to move detent protrusion  45 D towards the second position, button  48  is moved along a direction substantially perpendicular to rotatable table  17  and/or fixed table  16 .  
      Persons skilled in the art will recognize that housing  41  preferably has a channel  41 C that allows housing  41  to clear detent plate  18  and/or raised portion  16 R. Persons skilled in the art will recognize that detent protrusion  45 D may be within channel  41 C.  
      Housing  41  may have an opening  41 O above channel  41 C, allowing the user to see detent plate  18  underneath housing  41 . A transparent piece  41 P may be attached to housing  41  and extend into opening  41 O. Piece  41 P may have an indicia  41 PI. With such arrangement, the user can determine the rotational position of rotatable table  17  relative to fixed table  16  by looking through opening  41 O and using indicia  41 PI,  18 I to indicate such position.  
      Persons skilled in the art will recognize that housing  41  may be shaped around kerf opening  17 K to allow blade  23  to extend therethrough.  
      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.