Patent GB-545947-A (GB)
Title: Improvements in or relating to power transmissions
IPC: F04C11/00
Filed: 1941-02-12
Abstract: 545,947. Hydraulic power transmissions ; rotary pumps. VICKERS, Inc. Feb. 12, 1941, No. 1902. Convention date, Jan. 10, 1940. [Class 69 (ii)] [Also in Group XXVI] In a hydraulic power transmission system in which a plurality of motors are operated to control devices in connection with machine tools, ejection moulding and other apparatus, a multiple pump unit is employed which may take the form of a pair of rotary vane pumps 16, 18 driven from a common shaft 24, the pump being mounted in a single body 10 which is formed with separate delivery conduits 46, 82, and a relief conduit 108 normally separated from the conduit 46 by a valve 148, Fig. 4, which is normally closed by action of an adjustable spring 158 and is capable of being opened by means responsible to pressure in either one or other of the delivery conduits. The conduits 46, 82 are provided with a connecting passage which is either fitted with a spring-controlled relief valve 88 permitting liquid to pass from the conduit 46 to conduit 82, or with a plug which prevents such passage. The device is shown in Figs. 4 and 10 for use in a circuit which requires a large volume of liquid to be delivered at a relatively low pressure and under another condition with a smaller volume at a relatively high pressure as in the operation of machine tools. At the commencement of operations the valve 148 is closed and the delivery from both pumps is led to a common outlet pipe 216. As the pressure in the delivery conduit 82 of pump 18 rises pressure upon a piston 184 connected to the conduit by passages 194, 196, 188 increases until it is large enough to raise the valve 148 by acting upon an extension 178 thereof. The conduit 46 is thus connected to the conduit 108 with which is associated a relief pipe 218 leading to a reservoir. As the pressure drops in conduit 46 relief valve 98 closes cutting-off connection with conduit 82, and the rise of pressure in conduit 82 maintains this valve closed and the pressure rises until at a predetermined pressure a relief valve 116, Fig. 4, operates to relieve the pressure in the delivery conduit 82. The valve 148 may be operated by the pressure in conduit 46 instead of the conduit 82, the passage 188 in this case being closed by a screwed plug, and a similar passage opened from the conduit 46 by removing a screwed plug. Or the valve 148 may be operated from a pilot tube inserted in a screwed connection 212, Fig. 4, with passages leading to the passage in which a land 150 on the valve slides. The control of the delivery of pump 16 may thus be effected at a distance. The pumps may deliver to separate pipes by removing a stopper 56, Fig. 1, and inserting a delivery pipe instead. The valve 98 is replaced by a screwed stopper, and the valve 148 arranged to act as a relief valve for the delivery pipe of the pump 16 by arranging for the plunger 184 to be controlled from the conduit 46. A modification of the circuit is employed for operating a work clamp from the delivery pipe of pump 16, and arranging that the tool slide is operated from the delivery of both pumps by replacing the valve 98 so as to allow the pump 16 to reinforce the pump 18 until pressure has built up in the feed system of the tool slide whereupon the valve 98 closes and the conduit 46 maintains a predetermined pressure on the clamp. The screw 162 which controls the action of valve 148 passes through a cap 160 formed with an aperture 170 which normally registers with a breathing aperture 172. The cap can be fixed in a secured position displaced at an angle of 90 degrees to the first, and when in this position a pilot tube is connected to an aperture normally closed by a plug 174. In a circuit otherwise as in Fig. 10, this pilot tube is used in connection with the operation of an injection moulding-machine to apply pressure to prevent the valve 148 from lifting while the injection ram moves in at high speed, and so ensures the full delivery of both pumps to the injection cylinder. In a further modification in which a pilot tube 226, Fig. 16, is connected to the connection 186, Fig. 4, a valve 228 controls connections 230, 232 connected to the delivery pipes 216, 220 of the pumps 18, 16 respectively, the valve 148 may be made to act as an unloading valve in response to pressure in the conduit 82 or as a relief valve in response to pressure in the conduit 46. Other modifications of the hydraulic circuit may be made.