Patent Publication Number: US-2005121842-A1

Title: C-clamp having dual fastening mechanism

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to clamps and more particularly to an improved C-clamp having dual fastening mechanism for increasing reliability.  
      2. Description of Related Art  
      Clamps are well known devices such as those disclosed in U.S. Pat. Nos. 5,217,213, 6,240,815 B1, 6,474,632 B1, and 6,450,489 B1. A prior clamp  10  is shown in  FIG. 1 . The clamp  10  comprises a movabl jaw  111 , a fixed jaw  11 , a hollow fixed handle  12 , a pivotal handle  18  adjacent the fixed handle  12 , a movable section  14  in an upper portion of the pivotal handle  18 , a spring biased quick release  19 , a lengthwise channel  13  through the upper portions of the handles  12  and  18 , a lengthwise shaft  15  inserted through the channel  13 , the shaft  15  having a forward end secured to a lower portion of the movable jaw  111 , and two engaged fastening members  16  put on the shaft  15  and disposed in an upper cavity of the fixed handle  12 , and a spring  17  put on the shaft  15  and biased between a rear side of the fastening members  16  and a wall of the cavity in the fixed handle  12 .  
      In operation, an object is first placed between the jaws  111  and  11 . Next, press the pivotal handle  18  rearwardly to pivot about and receive in the hollow fixed handle  12  so as to cause the movable section  14  to exert a force to pivot the fastening members  16  from a slanted position to a vertical position with the spring  17  being compressed. At this position, the shaft  15  is unfastened. Thus, a user can slide the shaft  15  until the object is held by the jaws  111  and  11 . Next, release the pivotal handle  18  to cause the spring  17  to expand for disposing the fastening members  16  in a slanted position again. At this position, the shaft  15  is fastened and the object is held firmly by the jaws  111  and  11 . However, the prior art suffered from several disadvantages. For example, the fastening is not reliable since there is no way for the user to feel an appropriate fastening of the object. This in turn may damage the object if it is not structurally strong and an excessive force is exerted. Furthermore, an unintentional contact with the quick release  19  may unfasten the object and even cause the object to fall on the ground. This is not safe.  
      Another prior clamp  20  is shown in  FIG. 2 . Its characteristics are that a ratchet  33  is formed on a bottom of the clamp body adjacent the fixed jaw  22 . The spring biased quick release  30  has a top end shaped as a pawl  32  caught and held by a tooth of the ratchet  33 . The unfastening or fastening of the shaft  25  is controlled by a spring biased fastening member  281  by pressing the pivotal handle  28  or not. The pawl  32  moves backward a tooth with the shaft  25  being unfastened when the pivotal handle  28  is pressed. That is, the shaft  25  is slidable at this position. By repeating the above procedure, it is possible of stepwise firmly holding an object between the jaws  26  and  21 . To the contrary, a pressing of the quick release  30  will disengagement the pawl  32  from the tooth of the ratchet  33 . At this position, it is possible of unfastening the shaft  25  for removing the object. However, the prior art still suffered from a disadvantage. For example, the fastening is not reliable since it is provided by a single fastening member  281 . Hence, a need for improvement exists.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a C-clamp having dual fastening mechanism for increasing-reliability in operation.  
      To achieve the above and other objects, the present invention provides a C-clamp comprising a body; a forward fixed jaw; a rear movable jaw coupled to an upwardly extending portion of the body, the movable jaw including a ball shaped projection and a pivotal engagement member having a recess shaped to fitly receive the projection so that an object having a flat side surface or a slanted side surface is adapted to be held firmly between the fixed jaw and the engagement member; a rear fixed handle extended downwardly from the body; a forward pivotal handle extended downwardly from the body to form an acute angle between the handles, the fixed handle having an upper, transverse pin; a forward first cavity in the body; a first fastening member in the first cavity proximate the pin; a spring having a forward end held by the first fastening member; a rear second cavity in the body; a hollow resilient member in the second cavity; a ratchet on a bottom of the body; a lengthwise channel through the body; a spring biased quick release pivotably coupled to the pivotal handle, the quick release having a top pawl adapted to be caught and held by the ratchet; a lengthwise shaft through the channel, the second cavity, the resilient member, the first cavity, and the first fastening member, the shaft having a forward end secured to a lower portion of the movable jaw wherein in an inoperative state of the pivotal handle, the shaft is unfastened as the first fastening member is vertically disposed in the first cavity; a hollow abutment member in a forward end of the second cavity with the shaft being passed therethrough, the abutment member being coupled to a rear end of the spring; and a hollow second fastening member put on the shaft, the second fastening member having a bottom in contact with bottoms of both the resilient member and the abutment member, and a top received and held captive in a recessed wall of the second cavity, whereby pivoting the pivotal handle about the fixed handle will cause the pin to contact and move the first fastening member to a slanted position by compressing the spring, move the pawl backward along the ratchet, and move the abutment member backward to cause the second fastening member to be disposed vertically by urging against the resilient member, thereby fastening the shaft by the first fastening member and the second fastening member since the second fastening member is slanted immediately after releasing the pivotal handle, and stepwise fastening the object; and pressing the quick release will disengage the pawl from the ratchet so as to pivot the pivotal handle to return the second fastening member to the vertical position through an activation of the abutment member, and return the first fastening member to the slanted position respectively, thereby enabling a removal of the object.  
      The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side elevational view of a conventional clamp;  
       FIG. 2  is a side elevational view of another conventional clamp;  
       FIG. 3  is a side elevational view of a preferred embodiment of C-clamp according to the invention;  
       FIG. 4  is an exploded perspective view of abutment member, second fastening member, and resilient member all put on the shaft;  
       FIG. 5  is a side elevational view in part section of the movable jaw;  
       FIG. 6  is a side elevational view illustrating the fastening of an object; and  
       FIG. 7  is a side elevational view illustrating the fastening of an object having a slanted side surface. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to FIGS.  3  to  7 , there is shown a C-clamp constructed in accordance with the invention. The clamp comprises a body  20 , a fixed jaw  26 , and a movable jaw  21  including a ball shaped projection  210  and an engagement member  211  having a recess  212  shaped to fitly, pivotably receive the projection  210 . An object, having a flat side surface (see  FIG. 6 ) or slanted one (see  FIG. 7 ), is adapted to be held firmly between the toothed surfaces of the jaw  26  and the engagement member  211  since the engagement member  211  is slightly pivotal similar to a universal joint.  
      The body  20  comprises a fixed handle  22 , a pivotal handle  28  adjacent the fixed handle  22 , the pivotal handle  28  having an upper, transverse pin  281 , a forward first cavity  24 , a first fastening member  27  in the first cavity  24  proximate the pin  281 , a spring  241  having a forward end held by the first fastening member  27 , a rear second cavity  24 A, a gable, hollow resilient member  29  in the second cavity  24 A, a ratchet  33  formed on a bottom of the body  20  adjacent the fixed jaw  22 , a quick release  30  pivotably coupled to the pivotal handle  28 , the quick release  30  having a top end shaped as a pawl  32  being adapted to be caught and held by a tooth of the ratchet  33 , and a lower spring  31  interconnected the quick release  30  and the pivotal handle  28  so as to smoothing the pivoting, a lengthwise shaft  25  through a lengthwise channel  23  of the body  20 , the second cavity  24 A, the resilient member  29 , the first cavity  24 , and the first fastening member  27 , the shaft  25  having a forward end secured to a lower portion of the movable jaw  26 , a hollow abutment member  35  in a forward end of the second cavity  24 A with the shaft  25  passed therethrough, the abutment member  35  being coupled to a rear end of the spring  241 , and a hollow second fastening member  34  put on the shaft  25 , the second fastening member  34  having a bottom in contact with bottoms of both the resilient member  29  and the abutment member  35 , and a top received and held captive in a recessed portion in the wall of the second cavity  24 A.  
      In an inoperative state of the pivotal handle  28 , the shaft  25  is unfastened since the first fastening member  27  is vertically disposed in the first cavity  24 . At this position a user can slide the shaft  25  for holding an object between the toothed surfaces of the jaw  26  and the engagement member  211 . For fastening the object press the pivotal handle  28  rearwardly to pivot about the fixed handle  22  so as to cause the pin  281  to exert a force to move the first fastening member  27  to a slanted position by compressing the spring  241 . As such, the shaft  25  is fastened. At the same time, the pawl  32  moves backward a tooth and is always caught and held by the ratchet  33 . Also, the abutment member  35  moves backward as biased by the compressed spring  241 . This in turn causes the second fastening member  34  to be disposed vertically by urging against the resilient member  29 . Further, the shaft  25  is fastened by the second fastening member  34  since the second fastening member  34  is slanted immediately after releasing the pivotal handle  28 . By repeatedly pivoting and releasing the pivotal handle  28 , it is possible of stepwise firmly holding the object between the toothed surfaces of the jaw  26  and the engagement member  211 . This process can prevent the forward movement of the pivotal handle  28 , maintain the first fastening member  27  to be urged by the pin  281 , and maintain the shaft  25  to be fastened by both the first and the second fastening members  27  and  34 . This is a dual fastening design. Hence, the fastening of the object is more reliable. Note that an unintentional contact with the quick release  30  (i.e., unfastening the shaft  25  secured by the first fastening member  27 ) will not unfasten the object since the shaft  25  is still fastened by the second fastening member  34 . For removing the object, press the quick release  30  to disengage the pawl  32  from the tooth of the ratchet  33 . At this position, it is possible of pivoting the pivotal handle  28  to return the second fastening member  34  to the vertical position through the activation of the abutment member  35 , and return the first fastening member  27  to the slanted position respectively. At this position, a forward sliding of the shaft  25  is made possible, thereby enabling the removal of the object.  
      While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.