Release mechanism for a riveting gun comprising an overhead valve

Claim 1

A release mechanism for compressed air riveting or nailing guns comprising an overhead valve and a pilot valve which controls a duct for feeding compressed air to the overhead valve and comprises a valve plug mobile between three positions, namely a first gun activation position in which it connects the feed duct to a duct for discharge to atmosphere and closes the compressed air supply, a second gun resetting position in which it connects the feed duct to a compressed air supply and closes the discharge duct, and a third gun neutralization position, intermediate between the preceding, in which the valve plug closes the discharge duct and compressed air supply, said mechanism also comprising a feeler supported mobile in the gun and able to undergo a movement stroke when the gun is rested on a piece to be nailed, a main trigger hinged to said gun, and a lever hinged in said main trigger in such a manner as to act on the valve plug and be controllable by the feeler, movement of the valve plug by the lever being determined by the combined operation of the main trigger and feeler, characterized in that the release mechanism comprises an auxiliary trigger hinged in the main trigger and cooperating with said lever in such a manner that when the main trigger and auxiliary trigger are pressed simultaneously, the lever causes the valve plug to move into its intermediate position and prevents the resetting of the gun.