GB1373098A - Hydraulic valves for use with reciprocating mechanisms - Google Patents

Abstract

1373098 Percussive tools A F HYDRAULICS Ltd 7 Jan 1972 [8 Oct 1970] 47867/70 Heading B4C [Also in Division F1] A valve assembly for supplying alternating flow to the pressure chamber C of a road hammer H comprises resiliently loaded main and auxiliary valve members 7, 13 automatically reciprocable in a valve body 1 to cause alternate pressurization and depressurization of an outlet 25 to the hammer H. The main valve member 7 reciprocates in a bore 2 provided with an inlet port 18, an outlet port 19 and an intermediate exhaust port 20. When the inlet port 18 is pressurized, liquid flows through a passage 23 and an axial bore 8 in the member 7. This causes lifting of the auxiliary valve 13 and consequential flow to the outlet 25. Eventually a pressure builds up in the outlet 25 which is sufficient to displace the member 7 against the bias of a spring 6. As a result the exhaust port 19 is uncovered to allow the outlet to exhaust; inlet port 18 is closed; and the intermediate exhaust port 20 aligns with a passage 24 to allow the escape of liquid trapped in a chamber 5. The collapse of pressure in the outlet 25 allows the spring 6 to return the member 7 to its original position and the cycle is repeated. A second embodiment is described in which the valve member 7 is biased hydraulically and the auxiliary valve 13 is disposed in a flow passage in the body 1 and not in the member 7.