Patent ID: 8707566

Claim:
A knife comprising: a housing; a blade; a blade holder in the housing adapted to hold the blade and shiftable in the housing between a safety position in which the blade is wholly recessed in the housing, a first cutting position in which the blade projects at least partially from the housing, and a second cutting position in which the blade also projects at least partially from the housing and into which the holder is shifted when a cutting force is effective on the blade with the blade holder in the first cutting position; an actuating element shiftable in the housing between a starting position and an actuating position; a connecting linkage comprising at least one connecting element having one end pivoted at a first axis on the blade holder and another end pivoted at a second axis on the actuating element, the first and second axes being spaced in the first cutting position of the blade holder at a first spacing from each other in a first orientation and in the second cutting position of the blade holder the linkage is in an intermediate orientation, the linkage in the first orientation transmitting force from the actuating element to the blade holder to retain the blade holder from moving into the safety position of the blade holder from the first cutting position of the blade holder, the linkage in an intermediate orientation not retaining the blade holder against movement into the safety position of the blade holder from the second cutting position of the blade holder, the first and second axes being at a second spacing in a second orientation when the actuating element is in the actuating position and the blade holder is in the safety position; and biasing means for urging the blade holder into the safety position.