Abstract:
An offset force clamp is provided for securely holding a workpiece to a table of a cutting machine. The clamp is a modified clamping pliers having a planar base jaw and an elongate upper jaw oriented perpendicular to one another. The base jaw is preferably mounted fixedly to a first handle of the clamp and the upper jaw is preferably mounted pivotably to a second handle of the clamp. The base jaw is configured to engage the table as the upper jaw applies an offset force to hold the workpiece so that the clamp is not cut during the cutting operation.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of clamping devices, and more particularly to clamps using a pair of handles for causing a connected pair of jaws to engage a workpiece. 
     BACKGROUND OF THE INVENTION 
     A clamp is a tool useful either for holding two parts together during an assembly operation, e.g. gluing, or for holding one or more pieces in place on a table for machining, that is drilling, cutting, etc. A significant advance in the design and utilization of clamps was the creation of the clamping pliers, most popularly known as Vice Grip® pliers. The Vice Grip® pliers has a first handle that is rigidly connected to a first jaw and a second handle that is pivotably connected to a second jaw with an intermediate link that is pressed past a pivot center point to hold the jaws closed against the workpiece. Since the introduction of the Vice Gripe pliers, many variations of jaw configuration have been developed for specific applications. In all known configurations of the clamping pliers or other types of clamps, the two jaws are symmetrical and linearly opposed to one another to apply the clamping force to the workpiece. 
     In many cutting operations involving machines, e.g. water jet cutters, band saws, milling machines, etc., it is necessary to clamp the workpiece to the machine table during the cutting operation to improve accuracy and safety. Water jet cutters operate at high rates of water flow generated by pressure of 50,000 psi to 60,000 psi, and are able to cleanly cut through steel plates. When the piece being cut is large enough, the clamping point can be remote from the cutting implement and hold the workpiece securely. When the piece being cut is small, clamping is difficult and the clamp may be cut by the water jet along with the workpiece. Attempting to perform a cutting operation without a mechanical clamp can result in personal injury to the machine operator. Therefore, a need exists for a clamp that is able to securely hold a small workpiece during a cutting operation without the clamp being damaged. 
     SUMMARY OF THE INVENTION 
     The present invention provides an offset force clamp for holding a workpiece on a table of a cutting machine. The clamp utilizes a pair of non-symmetrical jaws that are actuated by a clamping pliers mechanism. A first jaw is affixed to one handle of the pliers and configured to releasably engage a table of a Cutting machine. A second jaw is pivotably connected to the second handle of the pliers and configured to apply a clamping force at a location remote from the first jaw. The second jaw is relatively long and narrow. The first jaw is placed into engagement with the table in a location remote from the cutting implement, the workpiece is placed on the table in a location for cutting, and the pliers&#39; handles are moved together to cause the second jaw to hold the workpiece against the table. The typical adjusting screw of the clamping pliers is effective to increase or decrease the jaw clamping force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is best understood in conjunction with the accompanying drawing figures in which like elements are identified by similar reference numerals and wherein: 
         FIG. 1  is a front perspective view of the offset force clamp of the present invention. 
         FIG. 2  is a side perspective view of the offset force clamp shown in  FIG. 1  with a first jaw engaging a table of a cutting machine, e.g. a water jet cutter. 
         FIG. 3  is a side elevation view of the offset force clamp of  FIG. 1  with the first jaw engaging a cutting machine table and the second jaw open, the table and a workpiece shown in dashed lines. 
         FIG. 4  is a view of the offset force clamp of  FIG. 3  with the first jaw engaging a cutting machine table and the second jaw closed to hold the workpiece. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , an offset force clamp  10  of the invention is shown in front perspective view. Clamp  10  has a fixed handle  12  and a pivoted handle  20  that are operable to press an elongate upper jaw  32  against a workpiece as a substantially planar base jaw  30  engages a table, as will be described below. Fixed handle  12  and pivoted handle  20  are oriented in a plane that is substantially perpendicular to the plane of base jaw  30 . Upper jaw  32  is oriented in a plane that is substantially parallel to handles  12  and  20  and is perpendicular to the plane of base jaw  30 . The operation of clamping a workpiece involves moving pivoted handle  20  in the direction indicated by arrow A toward fixed handle  12 . This movement of pivoted handle  20  daises upper jaw  32  to move in the direction indicated by arrow B. A link  26  is pivotably connected to pivoted handle  20  and engages a stop within fixed handle  12  to hold pivoted handle  20  in a locked position and apply a force for holding the jaws together. A release  22  is mounted pivotably to pivoted handle  20  for opening clamp  10  and removing the workpiece. 
     Referring further to  FIG. 1 , base jaw  30 , according to the preferred embodiment of the invention, is substantially planar and formed in the configuration of the letter “I” with a central column, an upper cross bar  30   a , and a lower cross bar  30   b . Upper cross bar  30   a  and lower cross bar  30   b  are separated by a height H that is sufficient to engage a table, as will be described below. Upper jaw  32  extends a distance X outwardly perpendicular from the plane of base jaw  30  to apply an offset force for holding the workpiece to the table. The dimensions for height H and distance X are determined according to the parameters of the cutting equipment used. 
     Referring now to  FIG. 2 , clamp  10  is illustrated as being engaged with a table of a water jet cutting machine, designated as grate  38  and formed of a plurality of parallel plates  40 . It is typical to form the table of a water jet cutting machine as a grate in order to allow the substantial quantity of water discharged by the water jet to drain, although some water may be permitted to accumulate over grate  38 . To engage clamp  10  onto grate  38 , the machine operator orients lower cross bar  30   b  of base jaw  30  above and approximately parallel with plates  40 , passes lower bar  30   b  between a pair of adjacent plates  40  in the direction indicated by arrows C, and rotates clamp  10  in the direction indicated by arrow D to orient lower cross bar  30   b  approximately perpendicular to plates  40 . In this position upper cross bar  30   a  rests on the top surface of plates  40  of grate  38 , and lower cross bar  30   b  is spaced marginally below the bottom surface of plates  40 . As illustrated, the weight of the handles of clamp  10  will cause base jaw  30  to rest at an acute angle to vertical after base jaw  30  is inserted through plates  40 . 
     Referring now to  FIG. 3 , offset force clamp  10  is positioned with base jaw  30  engaging plates  40 , shown in dashed lines. A workpiece  44  is positioned on plates  40  for being cut, and is also shown in dashed lines. By forming base jaw  30  with height H (see  FIG. 1 ) that is greater than the height of plates  40 , bate jaw  30  can be readily rotated from being oriented parallel to plates  40  to being oriented perpendicular thereto. In the preferred embodiment, a gap G remaining between the bottom surface of plates  40  and lower cross bar  30   b  is on the order of ⅛ inch to ¼ inch. Elongate upper jaw  32  is positioned with the tip portion  34  thereof above a portion of workpiece  44 . According to the preferred embodiment of the invention, clamp  10  is oriented with pivoted handle  20  above fixed handle  12 . This preferred orientation of clamp  10  permits pivoted handle  20  to rise when clamp  10  is opened, rather than to go down, therefore avoiding contact with or close proximity to the top surface of plates  40 . Closing clamp  10  involves pressing pivoted handle  20  toward fixed handle  12 , as indicated by arrow E, causing upper jaw  32  to move in the direction indicated by arrow F toward workpiece  44 . 
     Referring now to  FIG. 4 , offset force clamp  10  is illustrated in closed and clamped condition with tip  34  of upper jaw  32  holding workpiece  44  against plates  40 . As illustrated, tip  34  extends lower than the adjacent body portion of upper jaw  32  to enable tip  34  to securely contact different thickness workpieces. In this clamped condition, upper cross bar  30   a  is pressed against the top surface of plates  40 , lower cross bar  30   b  is pressed against the bottom surface of plates  40 , and base jaw  30  resides at an acute angle Y. The resultant forces applied by clamp  10  are base jaw force f 1  and upper jaw force f 2 . Forces f 1  and f 2  are offset from one another by a horizontal distance O. With workpiece  44  held securely to plates  40 , the nozzle  50  of the water jet cutting machine or another machine cutting implement is actuated to cut the desired pattern in workpiece  44 . The offset position of base jaw  30  and the small size of upper jaw  32  avoids either jaw being damaged by the cutting operation. According to the cutting operation being performed, additional offset force clamps may be used to securely hold different areas of the workpiece being cut. 
     Referring further to  FIG. 4 , when the cutting operation is complete, release  22  is lifted, allowing pivoted handle  20  and upper jaw  32  to move up and return to the positions shown in  FIG. 3 . Unless clamp  10  is intentionally removed from plates  40 , base jaw  30  remains engaged with plates  40 . Offset force clamp  10  is ready for holding an additional workpiece for another cutting operation. 
     In an alternate use of the offset force clamp  10  of the present invention, base jaw  30  is configured as an inverted “T” to engage a slot that is commonly provided in milling machine tables and the like. A lower cross bar of the inverted “T” is inserted into the “T” slot and clamp  10  is rotated to orient lower cross bar  30   b  perpendicular thereto and prevent accidental removal. Clamp  10  is then operated as described above to apply an offset force to a workpiece. 
     While the description above discloses preferred embodiments of the present invention, it is contemplated that numerous variations and modifications of the invention are possible and are considered to be within the scope of the claims that follow.