Patent GB-1168655-A (GB)
Title: Improvements in Control Devices for Hydraulic Fluids.
IPC: F15B11/16
Filed: 1966-11-18
Abstract: 1, 168, 655. Hydraulic control circuits. ROBERT BOSCH G.m.b.H. Nov. 18, 1966 [Nov. 20, 1965], No.51757/66. Heading FIP A device for controlling the supply and exhaust of hydraulic fluid to a plurality of actuators (not shown) comprises a bank of six three-position spool valves 1 to 6 Fig. 1, (one for each actuator) each having service chambers 43, 44 flanking a pressure inlet chamber 42 and being flanked by exhaust chambers 45, 46 having neutral chambers 39, 41 which when all the valve spools 36 are in their central neutral position are in open series communication through passages 49, 51 and connect a single supply pump 10 to a return passage 84, 85; each spool also having control chambers 37, 38 connected in series by passages 23, 47, 48 between a pressure discharge valve 13 and the return line 84, 85 and which valve 13 located in a by-pass line 16 of the pump delivery line 9 becomes closed when one or other of the controls chambers 37, 38 of one or more of the valves 1 to 6 is blocked by lands 57, 58 on spools 36. The valve 13 together with a flow-dividing valve 15, supplied through a branch 27 of supply conduit 9 are located in a plate 7. The inlet chamber 42 of valve 1 receives a small flow from divider 15 through a passage 29 and a non return valve 67, whereas chamber 42 of valve 2 receives a large flow from divider 15 through a passage 28 and valve 67 together with flow through a branch passage 70 of passage 49. Inlet chamber 42 of valve 3 is in parallel with chamber 42 of valve 2. Chamber 42 of valve 4 is supplied through a branch passage 73 of neutral passage 49 and chamber 42 of valve 5 is in parallel therewith, whereas inlet chamber 42 of valve 6 is supplied through a branch 76 of neutral passage 49. In operation and with all six spools 36 in neutral the pump 10 delivery opens the throttled slide 19 of valve 13 and passes through a passage 12, 24 to reservoir and on partially displacing spool 36 of valve 1 in either direction from its neutral position, say to the right, control chamber 38 is first blocked to cause a pressure rise in discharge valve chamber 21 to balance the slide 19 in its closed position and to cause flow of pressure fluid through passage 26 and the neutral chambers 39, 41 of all the valves leading to the return passage 84, 85. Complete displacement of spool 36 of valve 1 to the right blocks neutral chamber 39 and opens service chamber 44 to the inlet chamber 42, which is connected to the small flow end of divider 15 to effect movement of the actuator connected thereto. The large flow from divider 15 is relieved through the neutral circuit of valves 2 to 6. With spool 36 of valve 1 in an operative position, actuation of the spool of any one of valves 2 to 6 results in its neutral circuit being closed and a large flow of pressure fluid being fed to its inlet chamber 42. With spool 36 of valve 1 in neutral, actuation of the spool 36 of any valves 2 to 6 results in full flow being fed to its inlet chamber 42. With spool 36 of valve 3 in one or other end position flow of pressure fluid to the inlet chamber 42 of all the subsequent values is effectively blocked. In a modified device comprising a bank of three spool valves 103, 104, 105, Fig. 2, the pressure discharge valve 112 is of the spool type and is held open when the spools 142 of valves 103, 104, 105 are in neutral by fluid admitted through a quantity limiting valve 121 and a throttle 119 to a chamber 114. Pump delivery is thus returned to sump through a conduit 107. In operation and on moving spool 142 of valve 103 to the right, a control chamber 139 is connected to an exhaust chamber 137 and the spool 112 of the discharge valve then closes to allow full pump pressure to pass from supply conduit 106 to the inlet chamber 134, service chamber 136 of valve 103 and also to the inlet chamber 134 of each valve 104, 105.