Patent ID: 7891098

Claim:
A knife with a retractable blade, the knife having a housing defining an internal chamber, and having a front end from which the blade is extendable and a rear end opposite the front end, and a locking mechanism movable within the chamber, the locking mechanism comprising: a blade holder for holding the blade, the blade holder being slidable within the housing from a forward position in which the blade partially extends from the front end of the knife, to a backward position in which the blade is withdrawn into the chamber; a biasing element configured to bias the blade holder toward the rear end of the knife; an actuation element for moving the blade holder backwards and forwards, the actuation element partially extending from the housing for manual control, the actuation element being operatively linked to the blade holder; a regulation channel having two opposing walls, and a floor extending from one wall to the other wall, the regulation channel defining a closed circuit; a snag element operatively attached to the housing, the snag element being configured to slide within the regulation channel as the locking mechanism moves within the housing; wherein, the floor of the channel includes a plurality of steps that are configured to compel the snag element to move around the closed circuit in only one direction by allowing the snag element to move over each step in a downward direction, but preventing it from moving in an upward direction; and further wherein, the regulation channel walls define an open holding pocket and a closed holding pocket, the closed holding pocket being spaced forwardly from the open holding pocket, and each holding pocket being configured such that, when the snag element is located in a holding pocket, the snag element cannot move immediately forward in relation to the locking mechanism as the snag element slides within the channel, whereby the locking mechanism is held in equilibrium by the biasing element.