GB932224A - Piston-ram assembly - Google Patents

Abstract

932,224. Percussive tools. BLACK & DECKER MANUFACTURING CO. Feb. 9, 1962 [May 5, 1961], No. 5128/62. Class 124. A percussive tool comprises a reciprocable ram 18 and a reciprocable piston 16, a chamber 21 between the piston and ram whereby a compressive gas, such as air, may be trapped therein, and a protrusion 24 on the piston and a recess 26 on the ram normally out of engagement, whereby, when a sufficient amount of gas leaks from the chamber and the ram initially bottoms against the piston, the protrusion acquires a press fit in the recess thereby coupling the piston and ram together for movement in unison and preventing further bottoming of the ram and piston. As shown in Fig. 1, the ram is freely slidable in a cylinder 17 secured by screws 28 to the gear-box 13 of an electrically-driven percussive tool, the piston being reciprocated via the gear-box through a shaft 14 and a crosshead 15. In the inoperative position of the tool, the ram takes up the position shown in Fig. 3. Upon movement of the piston, the air in the chamber 21 is compressed until, at a certain pressure, the ram rapidly moves and strikes the tool bit 19; retraction of the piston causes a suction in the chamber 21 and the ram returns. After considerable use, a sealing ring 23 on the piston wears and thereby permits leakage of the air from the chamber until the piston and ram abut and lock together as previously described in order to prevent damage by continual hammering of the drive elements in the tool. A groove 29 is provided in the ram wall so that at a certain relative position of the ram and piston, the air pressure in the chamber is able to adjust to its normal working level.