Patent GB-978113-A (GB)
Title: Improvements in or relating to fluid control valves
IPC: F15B13/01
Filed: 1961-07-26
Abstract: 978,113. Valves. CLARK EQUIPMENT CO. July 26, 1961 [Jan. 30, 1961], No. 27000/61. Heading F2V. [Also in Division G3] General.-The body 10, Fig. 2, of an opencentre type valve contains spool valves 12, 14 in bores 16, 20 controlling a double and a singleacting ram, respectively. The body has a supply port 23 leading to a supply passage 24 that is open to passages 26-28, which latter are also open to an exhaust passage 40 when the spools are in the neutral position shown; passages 24, 40 are also interconnected by a pressure relief valve 42 and passage 40 is open to a return passage 32. Both spools 12, 14 are manually operable and centred by spring means 74, which in the case of spool 14 has a lever 204, Fig. 4 associated therewith. Spool valve for a double-acting ram.-The bore 16, Fig. 2, incorporates grooves 56, 62 each leading via a valve 100, 102, Fig. 3, to a different end of the ram. These valves are of identical construction and each comprises a hollow cylindrical element 112, 112<SP>1</SP> with an annular conical surface 114, 114<SP>1</SP> co-operating with a seat 110, 110<SP>1</SP>, and a hollow stem 116, 116<SP>1</SP> which, to provide a gradual increase of fluid flow, contains axially-spaced graduated holes 118, 120, 122 and 118<SP>1</SP>, 120<SP>1</SP>, 122<SP>1</SP>. A pilot valve 132, 132<SP>1</SP> coacts with a bore 130, 130<SP>1</SP> through the element 112, 112<SP>1</SP> the skirt of which embodies a restricted orifice 146, 146<SP>1</SP>; the valves 100, 102 are in a common bore 106 which also houses a piston 154 with pins 158 whereby the pilot valve may be unseated. Upon the spool 12 being moved to the left, supply pressure passes into groove 62 and acts firstly to open the pilot valve 132<SP>1</SP> and then the element 112<SP>1</SP> whereby fluid is supplied to one side of the ram; concomitantly, the supply pressure moves the piston 154 to the right so unseating pilot valve 132, in consequence fluid returning from the other end of the ram passes into groove 56 via orifice 146, the resulting pressure reduction behind the element 112 then causing the latter to unseat and the flow into groove 56 passes through one or more of the holes 118, 120 and 122. When the spool 12 is urged leftwardly the roles of the valves 100, 102 are reversed. Spool valve for a single-acting ram.-The bore 20, Fig. 2, incorporates a groove 176, Fig. 4, leading to the one end of the single-acting ram via a valve 220 similar to the valves 100, 102, Fig. 3. Upon moving spool 14, Fig. 4, rightwardly, the supply pressure in groove 176 firstly opens the pilot valve 244 and then the element 232 which latter remains open only so long as fluid is flowing therethrough. When the spool 14 is translated to the left the lever 204 is moved counter-clockwise so urging a piston 262 to the right and unseating the pilot valve 244 and enabling fluid from the ram to flow to exhaust through groove 176 and passage 32, Fig. 2. The reduction in pressure behind the element 232, Fig. 4, then causes the latter to unseat. The gradual increase in fluid flow is, in this case, obtained by an annular member 270 on the piston stem 260. During rightward movement of the spool 14 the lever 204 does not pivot but serves as a fixed abutment for compression of the centralizing spring. Relief valve.-The relief valve comprises a casing 280, Fig. 2, in which is a main-spring- loaded valve element 292 and a variably spring-loaded pilot-valve 302; the casing 280 is open to supply pressure via a restricted orifice 298 and to exhaust passage 40 by a port 300. When the supply pressure exceeds that required the pilot valve 302 is unseated and connects the space behind the element 292 to the part 300 so that the supply pressure acting on a surface 310 unseats the element 292 so that passages 24 and 40 are connected through a further port 312 in the casing 280 and the seat 284 of the element 292.