Abstract:
A bar clamp is provided with a slide bar; a movable housing on the slide bar and including a movable jaw carrier including a first jaw at one end, a handgrip, and a trigger handle; a housing member releasably mounted on the slide bar and including a fixed jaw carrier and a second jaw; and a cam type fastening device on fixed jaw carrier. In an inoperative position thin portions of cam rings are locked allow a slide bar of another bar clamp to freely pass through the fastening device. A clockwise pivotal movement of a lever locks thick portions of the cam rings to fasten the slide bar of another bar clamp.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to bar clamps and more particularly to a bar clamp having a fastening device for temporarily fastening the slide bar of another bar clamp. 
     2. Description of Related Art 
     Clamps of various types have been available for a long time and are used in many applications where it is necessary to hold two or more objects together temporarily. A common problem associated with the use of clamps is that the objects may not be clamped firmly by the jaws. Further, it may sometimes be necessary to use a fixture or other temporary holding device to retain the objects in position so that the desired clamp can be used. However, this is cumbersome and also time consuming. 
     What needed is a clamp (e.g., bar clamp) which is convenient and efficient to use in clamping two or more objects together. The invention discussed below aims to meet the need. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a bar clamp comprising a slide bar; a movable housing slidably mounted on the slide bar and comprising a movable jaw carrier including a first jaw at one end, a handgrip extending in a direction opposing the movable jaw carrier, and a trigger handle disposed in front of the handgrip, one end of the trigger handle being pivotably disposed in the housing; a housing member releasably mounted on a forward end of the slide bar and comprising a fixed jaw carrier and a second jaw at one end of the fixed jaw carrier; and a fastening device comprising a through hole formed through the fixed jaw carrier; a cylindrical urging assembly disposed through the through hole and including a first member having a lengthwise first groove, and a second member having a lengthwise second groove, the second member being a mirror of the first member and spaced from the first member by a gap; and a cam assembly including two arc members wherein one arc member is formed besides one end of the through hole and the other arc member is formed between the other end of the through hole, and a cam member including two spaced, opposite cam rings each having a first portion and a second portion opposing the first portion and larger than the first portion, and a lever formed with the cam rings, wherein each cam ring has an eccentric outer surface, the cam member is put on projecting portions of the first and second members with the cam rings being pivotably contacted the arc members, in an inoperative position the first portions of the cam rings are lockingly engaged with the arc members to allow a slide bar of another bar clamp to freely pass through the first and second grooves, and a clockwise pivotal movement of the lever lockingly engages the second portions of the cam rings with the arc members by drawing the first member toward the second member to fasten the slide bar of another bar clamp. 
     The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a bar clamp according to a first preferred embodiment of the invention in an inoperative position; 
         FIG. 2  is an exploded view of the bar clamp except the housing and its components; 
         FIG. 3  is an enlarged view of the right top portion of  FIG. 1  with a slide bar of another bar clamp loosely disposed through the urging assembly; 
         FIG. 4  is a view similar to  FIG. 3  with the lever being clockwise pivoted about 135-degree to fasten the slide bar; 
         FIG. 5  is a perspective view showing two bar clamps being mounted on a workbench ready for work; 
         FIG. 6  is an enlarged view of the right side portion of  FIG. 1  but showing another configuration of the fastening device which is disposed on an end of an extension opposite to the fixed jaw carrier; 
         FIG. 7  is a side elevation of a right side portion of a bar clamp according to a second preferred embodiment of the invention in an inoperative position; 
         FIG. 8  is a sectional view taken along line  8 - 8  of  FIG. 7 ; 
         FIG. 9  is a view similar to  FIG. 8  showing a slide bar of another bar clamp loosely passing through the urging assembly; 
         FIG. 10  is a view similar to  FIG. 9  showing the lever being clockwise pivoted to cause the urging assembly to fasten the slide bar; and 
         FIG. 11  is a view similar to  FIG. 7  but showing another configuration of the fastening device which is disposed on an end of an extension opposite to the first fixed jaw carrier. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 6 , a bar clamp in accordance with a first preferred embodiment of the invention comprises the following components as discussed in detail below. 
     A slide bar  10  is configured as a flat bar and has a forward through hole  11 . A movable housing  20  is slidably mounted on the slide bar  10  and comprises a movable jaw carrier  21  including a first jaw  22  at one end, a handgrip  23  extending in a direction opposing the movable jaw carrier  21 , and a trigger handle  24  extending in the direction opposing the movable jaw carrier  21  and being forward of the handgrip  23 , one end of the trigger handle  24  being pivotably disposed in the housing  20 . 
     A housing member  30  is disposed on the slide bar  10  and comprises a transverse threaded hole  33 , a longitudinal channel  34  shaped to complementarily receive the slide bar  10  and intersecting the threaded hole  33 , a threaded fastener  35  driven through the threaded hole  33  and the through hole  11  to fasten the housing member  30  and the slide bar  10  together, an extending fixed jaw carrier  31 , and a second jaw  32  at one end of the fixed jaw carrier  31  facing the first jaw  22 . 
     A fastening device  40  comprises a through hole  41  formed through the fixed jaw carrier  31  adjacent the second jaw  32 ; a cylindrical urging assembly  42  disposed through the through hole  41  and including a first member  421  having a lengthwise groove  424   a , a second member  422  having a lengthwise groove  424   b , the second member  422  being a mirror of the first member  421 , and a gap  423  defined between the first member  421  and the second member  422 ; and a cam assembly  43  including two arc members  431  wherein one arc member  431  is formed between the second jaw  32  and one end of the through hole  41  and the other arc member  431  is formed between the second jaw  32  and the other end of the through hole  41 , and a cam member  432  including two spaced, opposite cam rings  4322  and a lever  4321  formed with and interconnecting the cam rings  4322 . 
     The width of the cam ring  4322  is not uniform. That is, the cam ring  4322  has a wide portion, an opposite narrow portion, and two intermediate portions each progressively formed between the wide portion and the narrow portion. A gap defined between the cam rings  4322  is substantially equal to the length of the through hole  41  so that the cam member  432  can be put on the projecting portions of the urging assembly  42  to have its cam rings  4322  rotatably contacting the arc members  431 . 
     In an inoperative position (see  FIGS. 2 and 3 ), the lever  4321  is substantially aligned with the fixed jaw carrier  311  and the narrow portions of the cam rings  4322  are lockingly engaged with the arc members  431 . As shown in  FIGS. 3 and 5 , one bar clamp is secured to a workbench  60  and another bar clamp  50  having its slide bar  51  passing through the fastening device  40  of one bar clamp. That is, the loose slide bar  51  of another bar clamp  50  passes through the grooves  424   a ,  424   b  (see  FIG. 3 ). 
     Further, a person may pivot the lever  4321  clockwise from the position shown in  FIG. 3  to the position shown in  FIG. 4  (i.e., a pivot angle of about 135-degree). After the pivoting, the wide portions of the cam rings  4322  lockingly engage with the arc members  431  with the first member  421  and the second member  422  drawn toward each other by the inward pushing force of the cam rings  4322 . Thus, the width of the gap  423  is decreased to a minimum. As a result, the slide bar  51  is fastened by the first and second members  421 ,  422  (see  FIGS. 4 and 5 ). Therefore, the person may push the jaws of another bar clamp  50  to clamp a workpiece (not shown) disposed therebetween prior to working. 
     To the contrary, an operation of the lever  4321  reversing above can loosen the slide bar  51 . In another configuration (see  FIG. 6 ), the fastening device  40  can be disposed on an end of an extension  312  opposite to the fixed jaw carrier  312 . 
     Referring to  FIGS. 7 to 11 , a bar clamp in accordance with a second preferred embodiment of the invention is shown. The characteristics of the second preferred embodiment are substantially the same as that of the first preferred embodiment except the fastening device  40   a  as detailed below. 
     The fastening device  40   a  is mounted at a portion of an extending fixed jaw carrier  31   a  of a housing member  30 . The fixed jaw carrier  31   a  is implemented as either a first fixed jaw carrier  311   a  in one configuration (see  FIG. 7 ) or a first fixed jaw carrier  311   a  and an extension  312   a  opposing the first fixed jaw carrier  311   a  in the other configuration (see  FIG. 11 ). The fastening device  40   a  comprises an externally threaded extension  45  on the fixed jaw carrier  31  adjacent the second jaw  32 ; a truncated conic through hole  44  through the externally threaded extension  45 ; a truncated conic urging assembly  42   a  movably disposed in the through hole  44  and including a first member  425  having a lengthwise groove  424   a , a second member  426  having a lengthwise groove  424   b , the second member  426  being a mirror of the first member  425 , and a gap  423   a  defined between the first member  425  and the second member  426 ; and a fastening member  46  including an internally threaded hole  461 , an inwardly extending rim  462  on the mouth of the internally threaded hole  461 , and a lever  463 . The internally threaded hole  461  is threadedly secured to the externally threaded extension  45 . The rim  462  has an inner diameter less than an outer diameter of the truncated conic urging assembly  42   a  so that the truncated conic urging assembly  42   a  is prevented from disengaging from the through hole  44 . 
     In an inoperative position (see  FIGS. 7 ,  8  and  9 ), the lever  463  is substantially aligned with the fixed jaw carrier  31   a . As shown in  FIG. 9 , another bar clamp having its slide bar  51  passing through the urging assembly  42   a  of one bar clamp. In detail, the loose slide bar  51  passes through the grooves  424   a ,  424   b.    
     Further, a person may pivot the lever  463  clockwise from the position shown in  FIG. 9  to the position shown in  FIG. 10  by driving the internally threaded hole  461  along the externally threaded extension  45  in a direction of decreasing the distance between the fastening member  46  and the fixed jaw carrier  31   a . And in turn, the urging assembly  42   a  is pushed further inward the through hole  44  by the rim  462  until the fastening member  46  is stopped by the fixed jaw carrier  31   a . The inward moving urging assembly  42   a  may decrease the gap  423   a  to a minimum. As a result, the slide bar  51  is fastened by the first and second members  425 ,  426  (see  FIG. 10 ). Therefore, the person may use the clamps to work on a workpiece (not shown). 
     To the contrary, an operation of the lever  463  reversing above can loosen the slide bar  51 . In another configuration, the fastening device  40  can be disposed on an end of an extension  312   a  opposite to the first fixed jaw carrier  311   a.    
     While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.