GB516565A - Improvements in or relating to hydraulic circuits and unitary hydraulic devices for use in hydraulic circuits - Google Patents

Abstract

516,565. Hydraulic apparatus. WAHLMARK, G. A. May 4, 1938, No. 13305. Convention date, May 7, 1937. [Class 69 (ii)] A hydraulic device for connection in a hydraulic circuit, e.g., for reciprocating a machine tool table, comprises a pump for supplying the pressure fluid to the operating device, e.g., the piston and cylinder for reciprocating the table, and valve mechanism for governing the pressure and volume of the output of the pump, the pump and governing mechanism being housed in a casing, within which passages for the flow of the' liquid are formed. The governing mechanism is controlled from a suitable distant point by a pilot valve which is adjustable manually, automatically or by a solenoid operated valve. As shown, applied to a circuit for imparting in succession to a machine table a fast approach, a fast feed, a slow speed, and a fast return motion, the device comprises a unit, Fig. 1, having a casing in five parts 17-21 secured together, the central part 19 containing the valve mechanism, the part 20, a constant output rotary pump 13, and the part 18, a variable output pump 14 supplied from the pump 13 and controlling the supply to the cylinder operating the machine table. The pump 14 comprises a number of cylinders 61, the inner end of each of which communicate through oppositely acting non-return valves 64, 65 with supply and exhaust chambers 54, 76 respectively. The pistons 62 bear against a wobble plate 80 pivoted on a ball joint 83 and having a roller connection 87 with an inclined slot 86 in the end of the driven shaft 36 which also drives the rotary pump 13. The ball 83 is carried by a plunger 88 and the position of the roller 87 in the slot 86 and thus the angularity of the plate 80 and the stroke of the pistons 62 can be varied by changing the position of the plunger 88 in its housing cylinder 89. For this purpose, the plunger 88 carries a rod 94, Figs. 1 and la, extending through slots 95' in the cylinder 89 and engaging between cam surfaces 92', 93<1> on a pair of worm-wheel rings 92, 93 mounted on the cylinder 89. By adjusting one or both of the rings by means of worms 95, 96 the limit positions of the plunger 88 in both directions may be varied. The plunger 88 is held in one end position by the pressure of the pistons 62 on the wobble plate and, during a certain period of the operation of the hydraulic device, in the other end position by high-pressure liquid applied through the connection 99, overcoming the pressure in the cylinders 61. In a modification, the plunger 88 can assume any of three positions, a third position being determined by a hydraulic cylinder acting on the end of the plunger. The governing valve-mechanism is shown diagrammatically in Fig. 9, the broken line representing the casing 19-21. The casing section 19 is provided with three borings 115, 187, 160. The boring 115 contains a starting valve 121, a valve 135 for controlling the pressure of the liquid supplied to the pump 14, and a valve 154 for controlling the supply of liquid to the connection 99. The bore 160 contains a reversing valve 178 for the cylinder 231 driving the machine table, and the bore 187 contains a valve 201 for controlling the exhaust from the cylinder 231 and a valve 217 acting to relieve abnormal pressure in the system. These valves are controlled by a pilot valve 15 which may be actuated manually or by dogs 237a, 237b, 237c, 237d, 237e on the machine table to assume five different positions corresponding to fast approach, fast feed, slow feed, fast return and stop. The initiation of the movement and the return movement of the table during a feed movement may also be effected by means of a solenoid-actuated valve 16. The valves 15, 16 are connected by pipes to connections 1, 2', 3, 5 and 6 in the casing part 19. In the "stop" position of the parts, which is that shown, and with the pump 13 running and drawing liquid from the tank 238, the pumped liquid in the passage 54 presses open the valve 121 against the action of a weak spring 123 and returns to the tank through passage 119. Liquid' passes through a small hole 128 in the valve but escapes to the tank by way of pipe 1, valve 16, pipe # 1', groove 248 in casing of valve 15, ports 260, 259, 258 in valve body, groove 246 and pipe # 8. Liquid also passes through a small hole 140 into the back of the valve 135 which is connected by passage 175, groove 174 in bore 160 and pipe # 2 to groove 249 in casing of valve 15, but as the groove 249 is blocked, pressure builds up within valve 135 to hold valve closed. In this " stop " position the pressure in passages 54, 55 is insufficient to open the inlet valves 64 of the pump 14. In the " fast approach " position of the valve 15, the groove 248 is blocked as well as the groove 249 and pressure builds up behind valve 121 to hold this valve closed., Maximum pressure then obtains in the passage 55 sufficient to open both sets of valves 64, 65 and then passes through passage 76, grooves 165, 164 in bore 160 and pipe 240 to cylinder 231 to drive the table at high speed. In the " fast feed " position of the valve 15, the groove 249 leads to the tank through ports 259, 258, groove 246 and pipe # 8to relieve the back of valve 135 of pressure. The valve is thus opened by the pressure liquid against the action of a strong spring 136 to allow part of the liquid to exhaust, the resulting pressure in the passage 55 being sufficient to open valves 64 but insufficient to open valves 65. The pump 14 thus acts to deliver a definite quantity of liquid to the cylinder 231. In this position the stroke of pump 14 is a maximum as the connection 99 is exhausted through passage 147, groove 146 in bore 115, ports 157 in valve 154 and passage 149. In the " slow feed position of valve 15, groove 248 connects to adjacent groove 247 leading by pipe # 3 to back of valve 154. Pressure from pipe # 1 thus causes movement of valve 154 to connect passage 147 by way of groove 156 in valve 154 to passage 152 connected to the delivery passage 76 from the pump 14. Pressure is thus applied to the plunger 89 to reduce stroke of pump 14 to its minimum. In the "fast return" position of valve 15, a groove 251 in casing of valve 15, connected by pipe # 6 to passage 54, connects to adjacent groove 250 so that pressure liquid passes to the end of bore 160 to cause reversal of the valve 178. In the reversed position the valve blocks the passage 175 so that valve 135 is again closed and maximum pressure obtains in the passage 55. At the end of the movement the valves return to the "stop" position shown. The initiation of the movement from "stop" position may be effected by an actuation of the solenoid valve 16. This actuation breaks the connection between pipes # 1 and 1<1> and thus causes the pressure to build up behind valve 121. At any time during the feed movement of the table, an actuation of the valve 16 will cause reversal of the valve 178 by pressure liquid passing from pipe # 6 to a pipe # 7 through the grooves 251, 252' which at that time are bridged, and through pipe # 5<1> to connection 5. The exhaust from the cylinder 231 takes place through passage 172, valve 201 and passage 119. The valve 201 is held open to an extent depending upon the pressure in the passage 76 by a projection 214<1> on a plunger 214 actuated by pressure liquid passing through a small hole 216, leaving by passage 199 to passage 76.