Various types of clamps are known. The common “C” clamp is a simple low cost device. A “C” shaped body includes an elongated screw at one end. The screw is advanced toward the opposite end of the clamp to hold an object between. Another well-known type of clamp is a screw actuated pivoted clamp, or cantilevered clamp. A typical version is shown in U.S. Pat. No. 2,726,694. This design allows a large opening size in a relatively compact form, except that the screw and cantilevered arm protrude greatly from the actual clamping structure. A similar clamp is disclosed in U.S. Pat. No. 4,258,908, except that a quick release screw is included to enable faster size closing action.
A more self-contained shape is shown in the clamp of U.S. Pat. No. 5,570,500. A sliding cam is hammered to move it along a triple pivot arrangement. Two pivoted arms move to squeeze an object. It is a specialty device that has a limited clamping range.
A “Spring Chuck” is shown in U.S. Pat. No. 6,212,977. A plier-like clamp includes pivoting jaw pads and a stepless locking mechanism including a bar and surrounding wedge to bind the bar. The maximum opening size is limited since the pivot or hinge is relatively close to the jaw. A similar design is shown in Exhibit A under the brand name “Quick-Grip Handi-Clamp”. The Handi-Clamp uses an arcuate locking bar rather than the straight bar of '977. A related type of locking plier is shown in U.S. Pat. No. 3,313,190. A conventional steel plier includes a stepless locking bar and related wedge at the handle distal end. The locking bar is curved as in the “Handi-Clamp”. The opening size is very linited since the hinge is very near to the jaws, as is typical is a plier. In the above plier style clamps there is a clear trade-off between available force and clamping force. More leverage or force leads to less possible opening size.
Another design uses a two stage closing process to enable fast action and high force. U.S. Pat. No. 2,838,973 is an example of this well known design for locking pliers. A high force clamping action follows a high speed closing motion. However since the hinge is very near to the jaw the possible opening size is small.
The prior art all have either limited opening capacity or are not compact in size. Most require two hands to operate. It is desirable to have a clamp that is: compact, one handed, large capacity and have high force.