Abstract:
A power tool with a base assembly, and a table supported by the base assembly, where the table has a workpiece supporting surface. A saw assembly is pivotably supported by the table via a trunnion assembly. The table includes a post having a first curved surface having a first radius. The trunnion has a first surface contacting the first curved surface. The trunnion is movable along the first curved surface. The first radius is larger than the distance between the first surface and the workpiece supporting surface.

Description:
REFERENCE TO CROSS-RELATED APPLICATION 
   The present application derives priority under 35 USC § 119(e) from U.S. Patent Application No. 60/606,935, filed Sep. 3, 2004. 

   FIELD OF THE INVENTION 
   This invention relates generally to a trunnion assembly for a saw and more specifically to a trunnion assembly for a combination table/miter saw. 
   BACKGROUND OF THE INVENTION 
   Typical miter saws have a trunnion assembly that allows the saw assembly to be beveled relative to a table. Typically, the bevel axis is coplanar with the table. In a combination table/miter saw, such arrangement may be undesirable, as, when the saw is used in table saw mode, the bevel axis will be underneath the table surface supporting the workpiece. It is an object of the invention to provide a trunnion assembly for such combination table/miter saw. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, an improved trunnion assembly is employed. The power tool has a base assembly, a table supported by the base assembly, the table having a workpiece supporting surface, and a saw assembly pivotably supported by the table via a trunnion assembly, wherein the table includes a post having a first curved surface having a first radius, the trunnion having a first surface contacting the first curved surface, the trunnion being movable along the first curved surface, the first radius being larger than the distance between the first surface and the workpiece supporting surface. 
   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 trunnion assembly according to the invention, where  FIGS. 2A-2B  are cross-sectional and rear perspective views, respectively, and FIG.  2 Ashows a cross-sectional view taken along plane II-II in  FIG. 2B ; and. 
       FIG. 3  illustrates an alternate trunnion assembly according to the invention, where  FIGS. 3A-3B  are cross-sectional and front perspective views, respectively, and  FIG. 3A  shows a cross-sectional view taken along plane II-III in  FIG. 3B . 
   

   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 assembly  21  disposed on the table assembly  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 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 and 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 . 
   Referring to  FIG. 2 , table assembly  11  may have a post  11 P with a curved flange  11 A. Trunnion assembly  21  may include a trunnion  21 T which pivotally supports arm  22 . Trunnion  21 T has two bearing surfaces  21 S sandwiching curved flange  11 A and contacting surfaces  11 AS of curved flange  11 A. Preferably surfaces  11 AS,  21 S are machined to minimize play therebetween. 
   A bolt  21 B extends through post  11 P and trunnion  21 T. A nut  21 N threadingly engages bolt  21 B to capture trunnion  21 T between nut  21 N and post  11 P. A washer  21 W may be provided between nut  21 N and trunnion  21 T to minimize friction therebetween. 
   Trunnion  21 T may also have a flange  21 F contacting a surface  11 B of post  11 P. Such contact reduces the forces acting on surfaces  11 AS,  21 S. 
   Persons skilled in the art will recognize that saw assembly  20  can be beveled by moving surfaces  21 S (and thus trunnion  21 T) along surfaces  11 AS of curved flange  11 A. Trunnion  21 T does not pivot about bolt  21 B because trunnion  21 T has an arcuate slot  21 AS that allows trunnion  21 T to change its rotational position, even though bolt  21 B does not move therealong. 
   Surfaces  11 AS are preferably curved and concentric. Preferably, the radii IR, OR of surfaces  11 AS are larger than the distance D between curved flange  11 A and table surface  11 S. Persons skilled in the art will recognize that curved flange  11 A thus defines a bevel axis A that is underneath table surface  11 S. 
   It is preferable to provide a bevel lock assembly  40  to lock trunnion  21 T in a desired bevel position. Bevel lock assembly  40  preferably comprises a lock lever  41 , which is rotatably disposed on bolt  21 B. Lock lever  41  may include a handle  41 H for rotating lock lever  41 . A locking plate  42  is disposed between lock lever  41  and trunnion  21 T. Bolt  21 B preferably extends through locking plate  42 . 
   Lock lever  41  and locking plate  42  preferably have corresponding cam surfaces  41 C,  42 C, respectively. With such arrangement, the user need only rotate lock lever  41  to fix the bevel angle of trunnion  41 T. When lock lever  41  is rotated, cam surfaces  41 C,  42 C contact, forcing locking plate  42  into trunnion  21 T and sandwiching trunnion  21 T into locking contact between locking plate  42  and post  11 P. 
   A nut  44  may be disposed on bolt  21 B to limit movement of lock lever  41  along the axis of bolt  21 B. A spring  43 , washers  42  and thrust bearing  45  may be disposed between nut  44  and lock lever  41 . During the locking operation, rotation of lock lever  41  does not cause rotation of nut  44  as washers  42  and thrust bearing  45  minimize any rotational movement transmitted to nut  44 . 
   Persons skilled in the art will recognize that, during the locking operation, the biasing force of spring  43  is increased due to the cam separation. Such bias forces lock lever  41  into contact with locking plate  42 . 
   Referring to  FIG. 2B , trunnion  21 T may carry a first bevel stop assembly  50 . Bevel stop assembly  50  may include a body  51  which is pivotally attached to trunnion  21 T. Body  51  may be rotated between a first position contacting a screw  11 ZS extending from table assembly  11 , and a second position not contacting screw  11 ZS. 
   Persons skilled in the art will recognize that, when body  51  is in the first position, trunnion  21 T will stop beveling when body  51  contacts screw  11 ZS. Preferably, screw  11 ZS will be adjusted so that trunnion  21 T stops beveling when trunnion  21 T is at the zero degrees position, i.e., blade  23  will be substantially perpendicular to table assembly. When the body  51  is moved to the second position, trunnion  21 T will effectively go past screw  11 ZS, as body  51  does not contact screw  11 ZS allowing a bevel angle of −3 degrees, for example. 
   Trunnion  21 T may carry a second bevel stop assembly  55 . Bevel stop assembly  55  may include a body  56  which is pivotally attached to trunnion  21 T. Body  56  may be rotated between a first position contacting a screw  11 FS extending from table assembly  11 , a second position contacting screw  11 CS extending from table assembly  11  (and not contacting screw  11 FS), and a third position not contacting either screw  11 FS,  11 CS. 
   Persons skilled in the art will recognize that, when body  55  is in the first position, trunnion  21 T will stop beveling when a surface  56 F contacts screw  11 FS. Preferably, screw  11 FS will be adjusted so that trunnion  21 T stops beveling when trunnion  21 T is at the 45 degrees position. When the body  56  is moved to the third position, trunnion  21 T will effectively go past screw  11 FS, as body  56  does not contact screw  11 FS, allowing a bevel angle of 48 degrees, for example. 
   Persons skilled in the art will recognize that, when body  55  is in the second position, trunnion  21 T will stop beveling when a surface  56 C contacts screw  11 CS. Preferably, screw  11 CS will be adjusted so that trunnion  21 T stops beveling when trunnion  21 T is at a predetermined angle. Such angle can be about 30 degrees, which is typically used when making compound cuts on crown molding. Preferably surface  56 C is inclined relative to surface  56 F. 
   Persons skilled in the art will recognize that the third position of body  56  is preferably between the first and second positions. 
     FIG. 3  illustrates an alternate embodiment of bevel lock mechanism  40 ′, where like numerals refer to like parts. The teachings of the previous embodiment are incorporated herein by reference. 
   In this embodiment bolt  21 B is preferably press-fit or threaded into post  11 P. A washer  46  is preferably disposed on bolt  21 B for contacting trunnion  21 T. 
   A cup assembly  47  is preferably disposed on bolt  21 B next to washer  46 . Cup assembly  47  preferably includes a cup  47 C which contacts the washer  46 . Cup assembly  47  may also include an elastic stop nut  47 N which is disposed within cup  47 C. Stop nut  47 N is preferably threadingly engaged to bolt  21 B, thus capturing trunnion  21 T between stop nut  47 N and post  11 P. 
   A pair of washers  48 W is preferably disposed on bolt  21 B next to cup assembly  47 . Preferably a thrust bearing  48 B is disposed on bolt  21 B between the pair of washers  48 W. Thrust bearing  48 B may be a ball bearing. 
   A handle  49  may be threadingly engaged to bolt  21 B and contacting one of washers  48 W. With such construction, the user can lock the bevel position of trunnion  21 T (and thus of saw assembly  20 ) by rotating handle  49 . 
   Upon rotation of handle  49 , a translational force is directed through washers  48 W unto cup  47 C. Persons skilled in the art will recognize that thrust bearing  48 B preferably isolates cup  47 C from any rotational motion imparted upon the washer  48 W which contacts handle  49 . Cup  47 C in turns moves washer  46  (and thus trunnion  21 T) towards post  11 P, locking trunnion  21 T (and thus saw assembly  20 ). 
   Persons skilled in the art will recognize that the thread pitch of bolt  21 B and/or handle  49  is preferably small to increase the clamping force for a given amount of torque. Persons skilled in the art will recognize that thrust bearing  48 B may also increase the clamping force for a given amount of torque. 
   Persons skilled in the art will also recognize that the bolt  21 B is used for both (a) capturing the trunnion  21 T and maintaining it within a certain distance to post  11 P, even when unlocked (by virtue of stop nut  47 N) and (b) assisting in the locking process. 
   Referring to  FIG. 3B , a crown bevel stop assembly  60  may be used to stop trunnion  21 T (and thus saw assembly  20 ) at a position between the two ends of the beveling range. Such position can be the bevel angle of about 30 degrees, which is typically used when making compound cuts on crown molding. 
   Crown bevel stop assembly  60  may include a body  61  which is pivotally attached to post  11 P, and a screw  62  which moves towards body  61  when trunnion  21 T (and thus saw assembly  20 ) is beveled. Body  61  may be rotated between a first position which would intercept and contact screw  62  as trunnion  21 T is rotated and a second position not intercepting and contacting screw  62  as trunnion  21 T is rotated. 
   Persons skilled in the art will recognize that, when body  61  is in the first position, trunnion  21 T will stop beveling when screw  62  contacts body  61 . Preferably, screw  62  will be adjusted so that trunnion  21 T stops beveling when trunnion  21 T is at the crown cutting position, i.e., about 30 degrees. 
   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.