Fastener driving tool with automatic return of plunger to firing position

摘要

The gun drives a plug (6) for fixing a part to a support by a plunger weight (10). The plunger is propelled to the front of the gun (9) under the action of combustion gases from a cartridge (11) located in a gun combustion chamber (15). A return chamber, along the plunger, has a front space (30) closed by the plunger front surface (28) and a rear space (22). Both spaces are in communication during displacement of the plunger. The rear space, after a first displacement of the plunger to the front, communicates with the combustion chamber. After communication between the front and rear spaces, the rear space is isolated from the front space after a second displacement towards the front of the plunger. Following this, the rear space communicates with the outside of the gun. The combustion gas expansion is trapped in the front space and returns the plunger to the rear firing position.