GB973139A - A percussive demolition tool with shock attenuating means - Google Patents

Abstract

973,139. Percussive drills. CHICAGO PNEUMATIC TOOL CO. May 21, 1963 [June 14, 1962], No. 20150/63. Heading B4C. A percussive tool such as a road breaker, comprises a casing 11 having a cylinder 13 in which a hammer piston 14 is adapted to reciprocate in order to pound, during a working stroke, the striking portion 35 of an anvil 15 which, in a low position, is seated on a shoulder 41 in the casing, and elastic yieldable means 19 in the easing for restricting the movement of the piston on its working stroke before the piston strikes the anvil while the latter is in its low position. The yieldable means 19 is in the form of two tubes 24, 25 bonded to a resilient material 26 such as neoprene, the ends of the outer tube 24 being clamped between the cylinder 13 and the front portion 12 of the casing 11. The anvil 35 is slidable in a sleeve 18 located within the tube 25 and provided with a flange normally held between one end of the latter tube and a shoulder 23 in the cylinder. In operation, if the drill bit 45 becomes stuck in the material 48 being drilled, the casing is lifted by handles 8 until further lift is prevented by an abutment 54 engaging with a flange 52 on the stem 45 of the bit as shown in Fig. 4. In this position the anvil drops on to the shoulder 39 so that the surface 42 of the upper striking portion 35 of the anvil is below the level of a chamfered surface 31 of the sleeve. If now the piston 35 is driven downwardly by pressurized fluid, instead of the piston striking directly the anvil and thereby transmitting the shock through the latter to the casing, the greater part of the force is taken up by the piston first striking the upper end of the sleeve and so distorting the resilient material 26 to absorb the energy.