GB1272226A - Improvements in or relating to alternating flow hydraulic systems - Google Patents

Abstract

1,272,226. Percussive tools. A. F. HYDRAULICS Ltd. 6 Nov., 1969 [11 Nov., 1968; 1 March, 1969], Nos. 53416/68 and 11069/69. Heading B4C. [Also in Division F1] An hydraulic pulse generator 1, Fig. 1, is connected by a long flexible power line 3 to the pressure space 10 of a receiver, e.g. a percussive drill having a control by-pass valve 19 which when moved by a lever so into its open position shown, i.e. drill inoperative connects the power line 3 to a return line 6, and control means at the generator end of the line 3 senses flow conditions in line 6 and serves to prevent the pressure pulses from reaching the major length of the line 3. The control means comprises a pilot valve 27 which when urged upwardly to the position shown against a spring 33 by return pressure upstream of a restrictor 25 connects a make-up pump 4 with the underside of a main control valve 26 to lift the same whereby pulses are directed from line 3 into an accumulator 28. On releasing lever 20 valve 19 closes and the pressure drop in line 6 results in valves 26, 27 assuming their inoperative positions and the pressure pulses being transmitted to space 10. The return stroke of the drill is effected by pressurized liquid in a chamber 13. In a modification wherein the generator 1, Fig. 2, is a cam actuated differential piston 1a, the main valve 55 when in its operative position connects line 3 with the generator chamber 52 which results in piston 1a being lifted from cam 51. In a further modification the generator 1, Fig. 3, is driven through a clutch 60 which is disengaged by flow from the make-up pump 4 passing through the main valve 62 in its operative position; the pilot valve being dispensed with. In a modification the return line includes a cooling radiator for the circulating oil.