GB1391796A - Hydraulic impactor apparatus - Google Patents

Abstract

1391796 Percussive apparatus HUGHES TOOL CO 22 March 1972 [5 April 1971] 13335/72 Heading B4C [Also in Division F1] A hydraulic percussive apparatus comprises a tool having a housing 11, and a hammer piston 59 reciprocable within the housing to apply impacts to a tool bit 27 slidably received in the housing; and a hydraulic pump 39 for supplying liquid, e.g. oil, alternately to chambers 61, 63 defined within the tool by the piston and the housing. The pump 39 includes a wobble plate 88 rotated by a rotary hydraulic motor 31 connected to the output of a pump 81, and two banks of piston and cylinder units B 1 , B 2 , the pistons of each bank being reciprocated under the action of the wobble plate and return springs, and the cylinders of each bank being connected to a respective pipe 43, 51. Each piston includes a check valve 47 so as to permit liquid to flow from the housing of pump 39 into each cylinder during a piston return stroke, and each of a selected number (but not all) of the cylinders in each bank includes a check valve 49 which prevents a return flow of liquid in pipe 43 or 51 into the cylinder during a piston return stroke. Thus a pressure pulse is supplied alternately to the chambers 61, 63 by the pistons of the banks B 1 , B 2 , and during the return strokes of the pistons in each bank a return flow of liquid from the respective chamber to that bank takes place. Liquid in the chambers passes to tank 77 via passages 71, 73 67 and a restriction 69 which may be adjustable, and which prevents cavitation in the chambers. The tool bit includes a flange 89 and is slidably mounted in bushings 95, 99 separated by a spacer ring 97. The bushings and spacer ring are retained in the housing 11 by a retainer ring 104 which itself it retained in the housing by pins 105 located in bores 106 and extending into an annular groove in the ring. Any liquid passing between the hammer piston and bushings 109, 133 is returned to drain via conduits 119. Sealing rings 123, 125 are positioned adjacent annular grooves 117 communicating with the conduits and the bushings 109 is provided with a wiper ring 127.