Patent GB-949607-A (GB)
Title: Improvements in or relating to pressure responsive valve equipment
Inventor: DENNY DOUGLAS FRANK
IPC: F15B13/07
Filed: 1960-02-08
Abstract: 949,607. Valves. PRATT PRECISION HYDRAULICS Ltd. Jan. 18, 1961 [Feb. 18, 1960], No. 5768/60. Heading F2V. [Also in Division G3] Pressure responsive spool valve equipment comprising a valve body with a cylindrical openended chamber for a movable spring-loaded valve spool, this chamber being closed at both ends by cap members, and wherein the chamber has more than two spaced annular channels affording flow ports controlled by the spool, comprises also a set of alternative, individually replaceable spools each having a different arrangement or disposition of lands thereon, whereby each spool controls the flow ports of the body in a different manner or sequence. In one alternative, Figs. 1 and 8a, the spool 8a has one annular channel 33 between two lands. This channel affords permanent communication between the annular inlet and outlet channels 4, 5 respectively of the body, the outlet channels 5 being in communication directly with one end of the spool and through a restriction 18 with the other end which is provided with an adjustable spring-loaded pilot valve 9 for relieving this end if the spool to an annular drain channel 3 of the body. Normally, the pressures on opposite ends of the spool are in balance and when the pilot pressure is exceeded the spool moves to the left to connect the inlet-outlet channels 4, 5 to drain channel 3. In a modification, the inlet and outlet conduits 12, 13 corresponding to the channels 4, 5 are interconnected through a spring-loaded check valve. In another alternative, Figs. 3 and 8d, the spool 8a of Fig. 1 is replaced by a spool 8d having two annular channels 34, 35 separated by an intermediate land 36. Annular channels 5 and 4 of the body are now inlet and outlet channels, respectively, which in the position shown are isolated by the land 36 whilst outlet channel 34 communicates with drain 3. On opening of the pilot valve 9, the spool moves to connect channels 5, 4 together and to isolate the channels 4, 3 from each other. Two other forms of the single-channel spool are disclosed, of which the first renders the valve a reducing valve wherein the high pressure inlet is connected to chamber 4 and the reduced pressure outlet to chamber 5 and chamber 3 to drain ; whilst the second spool renders the valve a sequence valve wherein the inlet is connected to chamber 5, the outlet to chamber 4, and chamber 3 to drain. Two other forms of the two-channel spool are also disclosed, of which the first renders the valve a restrictor flow control valve wherein the inlet is connected to chamber 3 and the controlled flow outlet to flow chambers 4 and 5 ; whilst the second spool renders the valve a counterbalance valve in which the inlet is connected to chamber 5 and chamber 4 is connected to drain, chamber 3 being blocked. Pressure gauge connections are provided as shown at G. In other combinations, the pilot valve 9 may be omitted and the spool valves therefore may be of the direct-acting type. The construction of Figs. 1 and 8a is illustrated again in a non-diagrammatic form (not shown) wherein, e.g. the ond caps referred to appear.