Patent GB-490450-A (GB)
Title: Improvements relating to liquid pressure systems
IPC: B60T13/14
Filed: 1936-12-10
Abstract: 490,450. Hydraulic accumulators. ROCKWELL, E. A. Dec. 10, 1936, No. 33915 [Class 69 (ii)] In a liquid-pressure system, particularly for the actuation of accessories on automotive vehicles, an intermittently operating electrically driven pump delivers liquid to an accumulator comprising a chamber or cylinder and movable means, including a movable wall or piston, for storing the pressure energy created by the pump, a presser plate, a spring or springs bearing on the presser plate, a support for the spring or springs mounted on the chamber or cylinder, and a housing mounted on the latter and enclosing the spring or springs and the presser plate, and a device actuated by said movable means for stopping the pump when the movable means reaches a predetermined position. Return liquid from the actuated mechanism enters by port 1 a filter chamber 2, Fig. 1, of thin metal, and passes through filter cloth 9, passage 18 and inlet port 19 to the pump. The pump comprises two gear-wheel pumps in series. It is provided with an impact cushionchamber 57 formed in a removable dome 58 on the pump casing which acts as an air cushion chamber to relieve the load on the pump when starting. It also comprises a radial passageway, formed in a spacing member, for conveying any oil that may leak along the shaft away from an end opening and from a rubber seal on the end of the shaft to a peripheral passageway and so back to the inlet port. The pump delivers past a rubber one-way valve 59 into cylinder 61 having an outlet port 62 and a piston 65 carrying the presser plate 67 which bears against the springs 17 situated in the filter chamber 2, these springs being supported by tubes 16 serving also to guide the presser plate and to support the filter cloth. The springs are under considerable initial compression. The piston 65 carries a member 68 which actuates a snap-acting switch also contained in the filter chamber for interrupting, when the accumulator is fully charged, the circuit of the electric motor 20 driving the pump. A tell-tale dash light 108 indicates when the motor of the pump is running. The pump casing has a screw 6 mounted by rubber washers 5 on a bracket 4 secured to the chassis. In a modification, Fig. 6, the accumulator plunger 110 is provided with a packing 111 and a clearance 112 to avoid scoring thereof by any dirt which may be present. The accumulator cylinder 113 extends into the exterior of the filter chamber, the presser plate 118 being suitably shaped to allow this. The switch actuating mechanism is, as before, situated in the filter chamber, but the switch itself is outside the said chamber. The filter chamber is provided with a vent opening 166 closed by a vented receptacle 167 packed with horsehair and covered with a ribbed cap 168 to permit the passage of air between the ribs thereof. The pump is slightly modified; in addition to the dome 114d, it is provided, Fig. 11, with a radial pulsation chamber 114m for balancing pulsations between the first and second gearwheel pumps. A floating or unloader valve 114e is also provided. During pumping, the valve 114e is raised by the high flow to permit passage of liquid into the annular discharge passage 114g. When the flow of liquid drops, as e.g. after the pump ceases to operate, the valve falls, causing a constricted portion 114f to establish communication between the annular discharge passage 114g and the inlet 114c through the passage 114l, thus permitting the liquid under pressure trapped between the pumps and the closed delivery valve in the passage 114g to escape to the inlet to reduce back pressure at starting of the pump. The system may be provided with any known control circuit, e.g. Delco-Remy, containing a magnetic switch, which upon operation of the pump control switch will permit the passage of a current, for example 7 amperes, sufficient to start the pump motor, and then as the magnetic switch cuts in, a greater current is supplied, for example about 40 or 50 amperes. Specification 473,568 is referred to.