Abstract:
A table saw includes two guide bars movable along two opposite sides of a worktable to carry a table extension, and a locking mechanism for locking the guide bars in position. The locking mechanism includes a handle pivoted to a coupling block at the bottom side of the worktable, two eccentric members reversely mounted in the handle, and two links respectively coupled between the eccentric members and the guide bars and movable with the handle to force a respective stop block against or to release the respective stop block from the guide bars to further lock or unlock the guide bars and the table extension.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a table saw and more particularly, to a table extension locking structure for table saw.  
         [0003]     2. Description of the Related Art  
         [0004]     A conventional table saw, as shown in  FIGS. 1 and 2 , comprises a worktable  1 , two guide bars  2  and  2 ′ respectively slidably coupled to two opposite lateral sides of the worktable  1  to carry a table extension (not shown), and a locking mechanism  3  provided at the bottom side of the worktable  1  for operation by the user to lock/unlock the guide bars  2  and  2 ′. According to this design, the locking mechanism  3  comprises a handle  4 , a fixed guide block  5 , a link  6 , an adapter  7 , and a stop member  8 . The handle  4  has a beveled push face  4   a  formed in the back side and disposed in contact with a spiral guide face  5   a  of the fixed guide block  5 , and a front side fixedly connected to one end of the link  6 . The other end of the link  6  is coupled to the stop member  8  through the adapter  7 . The stop member  8  is suspending inside one guide bar  2 .  FIGS. 1 and 2  show the stop member  8  not in contact with the inside wall of the guide bar  2 . At this time, the guide bars  2  and  2 ′ can be moved relative to the worktable  1 . When the user turned the handle  4  to move the beveled push face  4   a  over the spiral guide face  5   a  of the fixed guide block  5 , the stop member  8  is forced to displace and to further stop against the inside wall of the guide bar  2 , thereby locking the guide bars  2  and  2 ′ to the worktable  1 .  
         [0005]     The aforesaid locking mechanism  3  can be operated to lock/unlock the guide bars  2  and  2 ′. However, the handle  4  tends to be forced away from the locking position to release the stop member  8  from the guide bar  2  accidentally by an external force, thus the working safety is not ensured  
         [0006]     Therefore, it is desirable to provide a table extension locking structure for table saw that eliminates the aforesaid problem.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a table extension locking structure for table saw, which provides a positive locking force to lock the table extension of the table saw.  
         [0008]     To achieve this object of the present invention, the table saw comprises a worktable; at least one rail provided at the worktable; a coupling block fixedly provided at a bottom side of the worktable; at least one guide bar coupled to the at least one rail and movable along the at least one rail relative to the worktable; and a locking mechanism for locking the at least one guide bar to the at least one rail. The locking mechanism comprises a pivot pin fastened to the coupling block, and a handle coupled to the pivot pin and turnable about the pivot pin between a locking position where the locking mechanism locks the at least one guide bar to the at least one rail and an unlocking position where the at least one guide bar is unlocked from the at least one rail. The handle has a grip at a rear end thereof for the holding of the hand. At least one eccentric member having an actuating edge is mounted in the handle. At least one link has a hook disposed at one end thereof and fitting the actuating edge of each of the at least one eccentric member respectively and a stop portion disposed at an opposite end thereof for stopping against the at least one rail. The stop portion is forced against the at least one rail when the handle is moved to the locking position, and the stop portion is disengaged from the at least one rail when the handle is moved to the unlocking mechanism. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a sectional assembly view of a table saw according to the prior art.  
         [0010]      FIG. 2  is a schematic bottom view of the prior art table saw.  
         [0011]      FIG. 3  is an exploded view of a table saw according to the present invention.  
         [0012]      FIG. 4  is an exploded view of the locking mechanism according to the present invention.  
         [0013]      FIG. 5  is a perspective view in an enlarged scale of a part of the locking mechanism, showing the structure of the handle and the relative positioning of the two eccentric members in the handle.  
         [0014]      FIG. 6  is a top plain view of  FIG. 5 .  
         [0015]      FIG. 7  is a sectional assembly view of the present invention, showing the locking status of the locking mechanism.  
         [0016]      FIG. 8  is an enlarged view of a part of  FIG. 7 .  
         [0017]      FIG. 9  is an enlarged view of another part of  FIG. 7 .  
         [0018]      FIG. 10  is similar to  FIG. 7  but showing the unlocking status of the locking mechanism.  
         [0019]      FIG. 11  is an enlarged view of a part of  FIG. 10 .  
         [0020]      FIG. 12  is an enlarged view of another part of  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring to  FIGS. 3-6 , a table saw  100  in accordance with the present invention is shown comprised of a worktable  10 , a first rail  12 , a second rail  14 , a coupling block  20 , a first guide bar  24 , a second guide bar  26 , a table extension  28 , and a clamping mechanism  30 .  
         [0022]     The worktable  10  is a flat rectangular table. The first rail  12  is formed integral with one long side, namely, the first long side of the worktable  10 . The second rail  14  is formed of a plurality of guide blocks longitudinally arranged in line at the other long side, namely, the second long side of the worktable  10 . Alternatively, the second rail  14  can be a long bar formed integral with the second long side of the worktable  10 . Further, a mounting block  16  is formed integral with the bottom wall of the worktable  10  adjacent to the first rail  12  (see also  FIG. 7 ).  
         [0023]     The coupling block  20  is a frame member having a top wall  21  and two parallel sidewalls  22 . The top wall  21  has two through holes  211 . The sidewalls  22  each have a locating hole  221 . Two screws  23  are respectively mounted in the through holes  211  and threaded into the mounting block  16  to affix the coupling block  20  to the bottom side of the worktable  10 .  
         [0024]     The first guide bar  24  and the second guide bar  26  are straight bars, each having a longitudinal sliding groove  241  or  261  extending through the respective two distal ends. The first guide bar  24  is coupled to the first rail  12 . The second guide bar  26  is coupled to the second rail  14 . The table extension  28  is connected between the distal ends of the guide bars  24  and  26 . When the user pulls the table extension  28 , the guide bars  24  and  26  are moved with the table extension  28  along the rails  12  and  14 . Further, friction-resistant pads  40  are provided between the first guide bar  24  and the first rail  12  to reduce friction resistance.  
         [0025]     The clamping mechanism  30  comprises a handle  31 , a pivot pin  32 , a first eccentric member  33 , a second eccentric member  34 , a first link  35 , a second link  36 , and two stop blocks  37 .  
         [0026]     The handle  31  comprises a front base  311 , a rear grip  312  backwardly extending from the front base  311 , two front sidewalls  313  and  314  respectively upwardly extending from the front side of the front base  311  and substantially arranged in parallel, and a through hole  315  cut through the front sidewalls  313  and  314 . The front sidewalls  313  and  314  each have a first stop edge  313   a  or  314   a,  and a second stop edge  313   b  or  314   b  extending from one end of the first stop edge  313   a  or  314   a.    
         [0027]     The pivot pin  32  is fastened to the locating holes  221  and the through hole  315  to pivotally secure the handle  31  to the coupling block  20 , allowing the handle  31  to be turned about the pivot pin  32  between the locking position P 1  where the first stop edges  313   a  and  314   a  are stopped against the top wall  21  of the coupling block  20  (see  FIG. 7 ), and the unlocking position P 2  where the second stop edges  313   b  and  314   b  are stopped against the top wall  21  of the coupling block  20 .  
         [0028]     The first eccentric member  33  is fastened to the inner side of one front sidewall  313 , having an arched and slightly recessed actuating edge  331 . The second eccentric member  34  is fastened to the inner side of the other front sidewall  314 , having an arched and slightly recessed actuating edge  341 . As shown in  FIG. 8 , the first eccentric member  33  and the second eccentric member  34  are turnable with the handle  31  about the pivot pin  32 . The actuating edges  331  and  341  are disposed at two opposite sides remote from the pivot pin  32 .  
         [0029]     The first link  35  has an elongated shank  351 , and a hook  352  formed integral with one end of the elongated shank  351  to fit the actuating edge  331 . As shown in  FIG. 9 , one end (the end without the hook  352 ) of the shank  351  of the first link  35  is perpendicularly inserted through the second guide bar  26  across the longitudinal sliding groove  261  and then mounted with one stop block  37 , forming a first stop portion. According to this embodiment, the stop block  37  is fastened to the shank  351  through a screw joint.  
         [0030]     The second link  36  is comprised of a first rod member  361 , a second rod member  362 , a connecting member  363 , and two nuts  364 . The first rod member  361  has a hook  361   a  at one end and a screw tip  361   b  at the other end. The hook  361   a  is adapted to fit the actuating edge  341 . The second rod member  362  is a headed screw bolt perpendicularly inserted through the first guide bar  24  across the longitudinal sliding groove  241  and then mounted with the other stop block  37 , forming a second stop portion (see  FIG. 9 ). Further, the second rod member  362  has a threaded tip  362   a.  The connecting member  363  comprises a horizontal panel  363   a  and two vertical panels  363   b  arranged in parallel at two sides of the horizontal panel  363   a.  The vertical panels  363   b  each have a through hole  363   c  for the passing of the threaded tip  361   b  of the first rod member  361  and the threaded tip  362   a  of the second rod member  362  respectively. The two nuts  364  are respectively threaded onto the threaded tip  361   b  of the first rod member  361  and the threaded tip  362   a  of the second rod member  362  and stopped inside the connecting member  363  to secure the first rod member  361  and the second rod member  362  to the connecting member  363 . By means of rotating the nuts  364  relative to the threaded tips  361   b  of the first rod member  361  and the threaded tip  362   a  of the second rod member  362  respectively, the total length of the second link  36  is adjusted.  
         [0031]     After understanding of the component parts of the table saw  100  and their relative positioning, the operation of the locking mechanism  30  is described hereinafter.  
         [0032]      FIGS. 7 and 8  show the locking status of the locking mechanism  30  where the first guide bar  24  and the first rail  26  are locked. At this time, the first stop edges  313   a  and  314   a  of the front sidewalls  313  and  31  are stopped against the top wall  21  of the coupling block  20  (see  FIG. 7 ), holding the mechanism in the locking position P 1 ; the first link  35  and the second link  36  are respectively constrained by the first eccentric member  33  and the second eccentric member  34  to force the stop blocks  37  against the inner side of the first guide bar  24  and the inner side of the second guide bar  26  (see  FIG. 9 ), and therefore the first guide bar  24  and the first rail  26  are locked, i.e., the table extension  28  is locked.  
         [0033]     Referring to  FIGS. 10-12 , when the user turns the handle  31  downwards to move the second stop edges  313   b  and  314   b  into contact with the top wall  21  of the coupling block  20 , the mechanism is stopped in the unlocking position P 2 . Because the first eccentric member  33  and the second eccentric member  34  are moved with the handle  31 , the relative position between the actuating edges  331  and  341  is changed at this time. This relative position change releases the first link  35  and the second link  36  from the constraint of the first eccentric member  33  and the second eccentric member  34 , i.e., the stop blocks  37  are disengaged from the first guide bar  24  and the second guide bar  26 , allowing the user to move the table extension  28  to the desired position.  
         [0034]     As indicated above, the locking mechanism  30  has a simple structure and is inexpensive to manufacture. Further, the handle  31  can be turned to move the locking mechanism  30  between the locking position and the unlocking position and to have the locking mechanism  30  be positively positioned in the locking position or unlocking position, preventing a false action of the mechanism.  
         [0035]     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.