Stapler

A stapler for stapling a workpiece, comprising a base part for supporting the workpiece and a stapling head connected to the base part in a manner that permits the stapling head and the base part to move toward and away from one another in a reciprocating stapling movement that has a first point in the movement at which the stapling head and the base part are remote from one another and a second point in the movement at which the stapling head and the base part are closer to one another,

• wherein the stapling head accommodates staples and has a staple driver supported for sliding in the direction of stapling movement for driving a staple into the workpiece,
• wherein the stapler comprises an activating mechanism supported on the base part, which, in the course of a driving stroke that is part of the stapling movement, drives the stapling head and the base part toward one another to bring the stapling movement from a starting point to the second point, at which the stapling head and the base part are at their shortest distance from one another and are in clamping contact with the workpiece,
• wherein, during the driving stroke, a staple is driven into the workpiece, after which a return stroke is performed back to the starting point,
• wherein the activating mechanism includes a first coupling and a second coupling, each coupling having a pair of cooperable parts adapted to form an effective connection between its parts, and wherein the activating mechanism operates so that the first coupling moves toward the second coupling and the base part, whereby the distance between the first and second couplings is reduced during the stapling movement from a first extreme position in which the stapling movement is at the first point, to an opposite second extreme position, in which the stapling movement is at the second point,
• wherein the second coupling is a releasable coupling constructed so that the effective connection between its parts is releasable and so that, in the course of the stapling movement, it loses its effective connection if the driving stroke is prevented from reaching the second point because of excess thickness of the workpiece, and
• wherein the parts of the releasable coupling comprise first coupling surfaces of one of its parts immovably fixed to the base part and second coupling surfaces of the other of its parts movable with respect to the first coupling surfaces and the base part.