Patent ID: 8250764

Claim:
A knife, comprising: a handle enclosing at least a portion of one or more blades, a blade shuttle, a transmission, and a trigger, the handle comprising a blade aperture; the blade shuttle longitudinally moveable relative to the handle from a rest position to a first extended position and from the rest position to a second extended position, the first extended position differentiated from the second extended position, the blade shuttle moveable longitudinally from the first extended position and the second extended position to a cutting position when the blade is engaged in a workpiece, the knife configured such that the blade shuttle is automatically retracted from the cutting position to the rest position when the blade is disengaged from the workpiece; the blade secured within the blade shuttle, a distal end of the blade protruding a first distance from the blade aperture at the first extended position and a second distance from the blade aperture at the second extended position, the first distance differentiated from the second distance, the knife configured such that when the distal end of the blade protrudes the first distance from the blade aperture, the distal end of the blade moves to a distance from the blade aperture greater than the first distance from the blade aperture when the blade is engaged in the workpiece, and when the distal end of the blade protrudes the second distance from the blade aperture, the distal end of the blade moves to a distance from the blade aperture greater than the second distance from the blade aperture when the blade is engaged in the workpiece, the knife configured such that the blade is automatically retracted to a safe position within the handle when the blade is disengaged from the workpiece; and the trigger adapted to drive the blade shuttle from the rest position to the first extended position and from the rest position to the second extended position via the transmission, wherein the blade shuttle is in a fully extended position relative to the rest position in both the first and second extended positions, wherein the trigger is coupled to the handle at a fulcrum for pivotal movement to drive the blade shuttle from the rest position to the first extended position and from the rest position to the second extended position via the transmission, the trigger rotatably coupled to the blade shuttle through the transmission, and wherein the transmission comprises a pin coupled to the trigger such that a distance from the fulcrum to the pin remains substantially fixed as the trigger pivots to drive the blade shuttle between the rest position and the first extended position or between the rest position and the second extended position.