Patent GB-452484-A (GB)
Abstract: 452,484. Fluid-pressure servomotorcontrol systems. WELLMAN SMITH OWEN ENGINEERING CORPORATION, Ltd., Victoria Station House, Victoria Street, Westminster, and HOWARD, J. R., 116, Coalway Road, Wolverhampton. Feb. 22, 1935. No. 5713. [Class 135] In relay apparatus of the kind comprising means 13 for supplying liquid under pressure through passages 12 to two operatively connected opposed motors or to the ends of a double-acting motor 8 and valve means 19 controlling the exhaust of pressure liquid from the motor or motors through ports, one of which is opened while the other is closed, the valve means are the sole means controlling the pressure in the passages 12, 14 connected to the motor or motors and control the ports by a gradually variable sliding movement across them. The invention is applicable to the automatic control by a valve of gas flow or pressure, to the control of temperature, to the remote control of means indicating pressure differences or differences in liquid level, and to the control of conveying plant. A valve 4, Fig. 1, by regulating the flow in a main 2 in accordance with the changes in pressure in the two mains 2, 3 maintains a constant composition of gases in the common main 1. Such pressure changes, through pilot tubes 24<1>, influence interconnected diaphragms 22 which operated a slide valve 19 controlling the exhaust of pressure liquid through pipes 14 from the ends of a cylinder 8 containing a double-acting piston 7 connected to the valve 4. The ends of the cylinder 8 are supplied with pressure fluid such as oil in impulses by means of reciprocating pumps 13 delivering alternately or by a rotary pump having an associated rotary distributing valve. The slide valve 19 which is adjustable on a connecting rod 20 normally half covers each of two slit-like outlets in a plate 17 which may be adjustable relatively to a plate 16 to which the pipes 14 are connected. These outlets diverge towards the plate 16 where they communicate through other ports with the pipes 14. Adjustable stops 25 limit the displacement of the rod 20. Should the oil pressure fail, the ends of the cylinder 8 are each cut off from pipes 12, 14 by a spring-pressed valve 26, 27, Fig. 2, having two seating faces. Oil escaping past the slide valve 19 returns to the pumps by a pipe 19<1>. In the simple control of pressure in a single main, only one diaphragm 22 is required. To control two gas pressures or flows differentially, the valve 4 would be coupled to a valve in the main 3 so as to move oppositely thereto. The diaphragms 22 may be replaced by baffles directly deflected by the flow in the mains. Fig. 6 shows an arrangement in which the exhaust from the cylinder ends through pipes 14 is controlled by two rotary sleeve valves 30 connected by arms 34 to a member 35 subject to variable impulses. The valves have two, four or six ports 32 normally half covering corresponding ports 33 in inner sleeves 31 which are coupled by arms 36, a rod 37, and a lever of selected leverage to the rod of the servo-piston so as to follow-up the movement of the valves 30. This follow-up arrangement may be dispensed with by fixing the inner sleeves 31. The valve means may be formed as a rotary sliding disc, the motors may be vanes or diaphragms. According to the Proyisional Specification, the movement of the slide valve may be damped by a vane depending in a sump of exhaust oil.