GB1373848A - Hydraulic breaker operated by oil - Google Patents

Abstract

1373848 Percussive tools YUTANI JUKO KK 14 March 1972 [27 March 1971 17 July 1971 19 July 1971 12 Aug 1971 (2)] 11911/72 Heading B4C A percussive tool comprises a housing 1 slidably accommodating a hammer 17, a piston 6 to which the hammer is secured, and a valve member 5 which is movable relative to the piston to open and close communication between chambers 6a and 8. A tool bit 22 received in bore 4a and slidable between limits defined by pin 24 and recess 22b<SP>1</SP> is impacted by the hammer when the latter is reciprocated by means of oil pressure and spring 21. When in operation with the tool bit contacting a work surface, oil is supplied via check valve 11 to chamber 9 and, via ducts 6b, to chamber 6a, and the piston 6 and valve member 5 are raised against pressure oil acting on the end surface of the valve stem 5b and force of spring 21. When the position of Fig. 2 is reached the pressures in the chambers 8 and 9 are equalized via duct 2c, and upward movement of the valve member 5 continues whilst the piston and hammer are driven downwardly to impact the tool bit. When the piston 6 passes the duct 2d chamber 8 again communicates with sump 13 and the valve member 5 is returned to its Fig. 1 position, and the cycle is repeated. Upon the tool bit encountering a void in a work surface or upon the tool being raised from the work surface, the valve member, hammer and piston will be forced to a position in which the piston blocks supply duct 2b and conduits 12 and 2e communicate via at least one passage 5a in the valve, so that operation of the tool will be terminated. As the piston approaches the latter position oil between frusto-conical surfaces 16a<SP>11</SP> and 6c<SP>11</SP> will form a cushion and prevent an impact between the two surfaces. The length of cylindrical wall of hammer 17a is at least 1À3 times the diameter of the hammer.