GB1130164A - Slide valves - Google Patents

Abstract

1,130,164. Valves. DOWTY HYDRAULIC UNITS Ltd. 19 Nov., 1965 [4 June, 1965], No. 23897/65. Heading F2V. In a parallel slide valve, the slider has a main port 32 in permanent communication with a supply pressure through a passage 35 in the , casing 12 to 16, Figs. 1 to 3 and 5 (not shown). The slider is arranged to direct pressure fluid into one or the other of two service ports 48, 49, Fig. 5, in the casing, or from these ports to exhaust at 24, Fig. 6. The slider includes a pair of unloader ports 54, 55 extending transversely through it. When the slider is in a neutral position, these ports register on one side with ducting 60, 61 in the adjacent casing part 12 which communicates with the valve inlet 19, and on the other side the unloader ports register with ducting 65 communicating with the exhaust 24. Two such slide valves are associated together in one casing. The unloader ducting 60, 61 is bifurcated from the inlet 19, 35. Similarly, the ducting 65 on the other side of the first valve bifurcates into two ducts 62, 63 cooperating with the two unloader ports 54, 55 of the second valve, and these ports co-operate with a single duct 67 communicating with the exhaust 24. The supply to these two valves is commoned through a passage 26, Fig. 3, and individual check valves 20, 22 precede the entry supply ports 35, 34 into the valve chambers. A relief valve 25, Fig. 3, can by-pass the supply directly to exhaust. Balance ports 56, 57 and 58, 59 are provided in association respectively with the supply and unloader ports which in turn have associated inching grooves 70 to 75. In neutral position these balance ports register with the service ports so that the services S 1 , S 2 are held in a state of hydraulic lock.