Pliers having a manually adjustable, self-locking hinged jaw piece
BACKGROUND OF THE INVENTION 
     A problem that substantially reduces the usefulness of the conventional pliers is that jaws are not parallel to each other when gripping an object thereby causing the jaws to have the tendency to slip off the object. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a pliers having a hinged jaw piece which can be manually adjusted parallel relative to the other jaw and which is self-locking in the adjusted position. 
     It is another object of this invention to provide a pliers of the character described in which the jaws are adapted to be inserted in tight quarters. 
     Further objects and advantages of the invention will appear as the specification proceeds. 
    
    
     The preferred form of my invention adapted to a locking pliers is illustrated in the accompanying drawings in which: 
     FIG. 1 is a side view of the pliers with the jaws being shown in the closed position; 
     FIG. 2 is a partial side view of the pliers with the jaws being shown in the wide open position; and 
     FIG. 3 is a partial sectional view taken at 3--3 of FIG. 2. 
    
    
     While I have shown only the preferred form of my invention, I wish to have it understood that various changes and modifications may be made within the scope of the claims hereto attached without departing from the spirit of the invention. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in detail, the pliers comprise: a fixed jaw 1, a support arm 2 for the fixed jaw 1, a handle 3 attached to the support arm 2, a hinged jaw piece 4, a support arm 5 for the hinged jaw piece 4, the support arm 5 being pivotally attached to support arm 2 with pin 6, a handle 7 pivotally attached to support arm 5 with pin 8, hinged jaw piece 4 being pivotally attached to support arm 5 with pin 9, a toggle mechanism 21, a release 8 lever 11, a thumb screw 12, and a hinged jaw piece adjustment mechanism 13 which includes a link 14 which is threaded for most of its length and is engaged in adjustment nut 15, the link 14 having a hole in one end and being pivotally attached to hinged jaw piece 4 with pin 10. 
     The support arm 5 has a long clearance hole 17 to accept part of the threaded portion of link 14, the length of link 14 being long enough that it does not fall out of clearance hole 17 when the jaws of the pliers are in the wide open position. 
     The support arm 5 has a notch 18 which prevents adjustment nut 15 from moving in an axial direction but does not prevent it from turning. The hinged jaw piece 4 has a face 19 adapted to be clamped on an object, the face 19 preferably having sharp teeth (not shown), a tapered side 20 to permit the hinged jaw piece 4 to be inserted in tight quarters, and two plates 16 spaced apart to form a clevis, the plates 16 being large enough to pivotally attach the hinged jaw piece 4 to support arm 5 with pin 9, and to pivotally attach hinged jaw piece 4 to link 14 with pin 10. 
     The angular position of hinged jaw piece 4 is adjusted by turning adjustment nut 15. The hinged jaw piece 4 stays in adjusted position regardless of the clamping forces because link 14 is threaded and is engaged in adjustment nut 15 thereby making the adjustment mechanism 13 self-locking. 
     An undersireable feature of a pliers having a hinged jaw piece is the fact that when the jaws are in the wide open position, illustrated in FIG. 2, the distance measured from pin 6 to the tip of the hinged jaw piece 4 is substantially less than the distance measured from pin 6 to the tip of the fixed jaw 1. 
     To partially compensate for this condition, the pliers is designed so that the tip of the hinged jaw piece 4 extends beyond the tip of fixed jaw I when the jaws are in the closed position, illustrated in FIG. 1.