GB1130162A - Slide valves - Google Patents

Abstract

1,130,162. Valves. DOWTY HYDRAULIC UNITS Ltd. 19 Nov., 1965 [3 March, 1965; 23 April, 1965 (2)], Nos. 9076/65, 17163/65 and 17164/65. Heading F2V. In a parallel slide valve, the slider 20 has a main port 38 which is in permanent communication with the pressure supply port 27, Figs. 3 and 6 (not shown). There is at least one service port in the housing, which aligns with a balance port in the slider, e.g. the port 45, in a neutral position as shown. By movement in either direction, the service port is placed in communication alternatively with the supply port 38 or with an exhaust chamber 21 by an end control edge 47 of the slider. In the embodiment a second balance port 46 corresponds to a second service port, for controlling a double-acting jack S 1 , Fig. 5 (not shown). The valve is centred by a spring device 25 and operated manually by a lever 23. Two such valves for controlling separate jacks are incorporated in a unitary casing comprising spaced slider frames 13, 15 assembled with casing members 12, 14, 16. With both valves in neutral, the supply inlet 27 is in direct communication with the exhaust outlet 28 through an unloader port 49 in each slider and passages 52, 53, 54 in the casing members. The supplies to the valve chambers go through individual check valves 39, 40. A two-stage type relief valve 35 relieves pressure directly from a common pressure passage 34 to the exhaust outlet 28. Inching slots 55 to 60 are provided respectively at the two ends of the pressure port 38, at the two ends of the unloader port 49, and at the opposite end control edges 47, 48 of the slider in line with ports 38, 45, and 46. Two balance ports 50, 51 are provided on either side of the unloader port 49. In modifications, Figs. 7-11 (not shown), the arrangement of the inching slots is varied to cater for different requirements as to precision of control.