A number of devices are known for clamping workpieces which are fed into a machine.
U.S. Pat. No. 3,073,589, issued Jan. 15, 1963 to G. Hohwart discloses a work clamping fixture which is commonly used to hold a workpiece during a machining operation. The workpiece is clamped between a stationary and a movable jaw. The movable jaw is carried by and reciprocially actuated to and from the clamping position by slidably mounted posts through a rack and pinion which also acts to operate double cone locks when the work is clamped to hold the work securely by friction.
U.S. Pat. No. 2,667,903, issued Feb. 2, 1954 to R. A. McCallum describes a sawing machine with a sequentially operated holder-guard and saw. The McCallum saw is used primarily to cut mine timbers to the proper size. The saw guard also serves as a work holder, and a single fluid actuated motor performs the sequential operations of moving the saw guard into position to hold timber, and then advancing the saw against the timber for the cut. A reverse set of sequential operations takes place after the cut is completed.
U.S. Pat. No. 3,939,746, issued Feb. 24, 1976 to G. W. Rogers, et al. discloses a saw guard for a circular saw having a workpiece holder that moves relative to the saw blade. The saw guard is mounted on the leading edge of the workpiece holder, and is moved into a shielding position adjacent the cutting edge of the blade while the work piece holder is being restocked.
U.S. Pat. No. 4,206,672, issued June 10, 1980 to W. A. Smith describes yet another type of work holder in combination with a saw guard. The combination guard and work holder comprise two parallel plates pivotally attached to a jig and operable to swing downward on opposite sides of a through-slot to clamp the workpiece and to enclose the saw blade as the workpiece is advanced into the blade.
U.S. Pat. No. 1,600,604, issued Sept. 21, 1926 to A. Sorlien discloses a board holder for sawing machines. The board holder is attachable to the saw guide and is adjustable towards or away from the saw so that it may be disposed over any desired part of the board. A serrated eccentric mounted in a sleeve holds the board in place and prevents the board from being kicked back out by the rotating saw blade.
None of the aforementioned patents actively prevents the user of a saw from advancing his off-hand in the vicinity of the blade when the blade is operating. Therefore, numerous accidents occur wherein the operator of such a blade structure loses one or more of his fingers or other parts of his off-hand due to just such an accident.