US Patent 8122605 Utility knife with counter-reciprocating blade and guard

A utility knife has a counter-reciprocating blade and blade guard. Preferred utility knifes have an internal mechanism comprising several components that are advantageously coupled via one or more pivot points. Though an appropriate arrangement of pivot points, both stationary pivot points and translating pivot points, the blade and guard counter-reciprocate such that forced retraction of the guard results in forced extension of the blade. While the internal mechanism is in a locked position, the guard locked. Actuation of a trigger can unlock the internal mechanism, which releases the blade guard. Preferably a single actuation of the trigger provides for a single use of the knife.