GB1307188A - Hammer with hydraulically reciprocable piston - Google Patents

Abstract

1307188 Percussive tools FREID KRUPP GmbH 19 May 1971 [20 May 1970] 15750/71 Heading B4C A percussive tool comprises a differential hammer piston 1 having opposed annular surfaces F 1 , F 2 , the surface F 1 being constantly acted upon by pressure fluid, e.g., oil, whilst the larger area surface F 2 is alternately acted upon by pressure fluid and connected to exhaust to effect the reciprocations of the piston. With the tool in the illustrated condition the surface F 2 is open to exhaust conduit 13 via the intermediate small diameter portion of the piston 8 of control valve 16, and consequently fluid acting upon the surface F 1 will cause the hammer piston to perform a working stroke. When the hammer piston has moved a sufficient distance on its working stroke inlet conduit 14 will communicate with conduit 4 so that fluid at the inlet pressure P 0 will act on surface F V2 of the valve piston 8 to move the valve piston against bias of fluid at pressure P 1 acting via conduit 5 on the smaller area F V1 of the valve piston. Such movement closes communication between the surface F 2 and the exhaust conduit 13 and opens communication between the conduit 5 and the surface F 2 , so that fluid at pressure P 1 will act on surface F 2 and effect the return stroke of the hammer piston. Coupling of the annular passages 17, 18 via smaller diameter portion 9 of the hammer piston during the return stroke will effect connection of end surface F V2 of the valve piston 8 and the exhaust conduit 13 so that the valve piston will be returned to the illustrated position, thus reconnecting the surface F 2 to the exhaust conduit 13. The hammer piston will subsequently commence another working stroke. Throttle valve 15 includes a piston 20 biased to opposite directions by the inlet fluid pressure P 0 and a spring 23. Thus the pressure P 1 is automatically varied in dependence on the inlet pressure P 0 .