Fuente: WIPO "rice" 423. Rice, J. V. Jan. 7. Rock drills.-A hydrocarbon or gas actuated rock drill has an elongated piston 12, which is hollow to receive the piston-rod 18 and has diagonal slots 14, which engage projections 15 on a sleeve 19 held on the rod by a plate 27 and recessed to contain spring-pressed balls or rollers 20 to constitute a friction clutch for rotating the piston-rod on the return stroke of the piston. In order to cushion the blow and to cause the rotation by retarding the rod, the rod 18 has a slightly rounded or concaved part 17, which engages antifriction balls 24 carried in cup bearings 23 in the free ends of a single leaf-spring or a number of leaves 22. The inner ends of the springs may be bent, and are fixed to the piston by a sectional bevelled ring 26, which is tightened by an interiorly bevelled sleeve 25 screwed on the piston extension. In a modification, the sleeve 25 is elongated, and the springs are riveted to it at one end and rest free at the other end against the sleeve, and the bearing-rollers are journaled in clips which are carried on the springs. The piston is guided by blocks at each side, which slide in slots in the extension 7 and are connected by a pair of journals or return connecting-rods and crank-pins to the flywheel shaft 3. This shaft drives the cam shaft 29 by worm gearing, the cams operating the inlet and outlet valves 33, 32 for the explosive mixture.