Patent GB-487680-A (GB)
Title: Improvements in or relating to fluid pressure relay mechanism
IPC: G05D16/18
Filed: 1936-12-18
Abstract: 487,680. Fluid-pressure servomotors. ASKANIA - WERKE AKT. - GES. VORM. CENTRALWERKSTATT DESSAU UND C. BAMBERG-FRIEDENAU, and BLASIG, K. Dec. 18, 1936, No. 34885. [Class 135] A fluid-pressure relay for controlling a servomotor has a control member adapted to distribute pressure-fluid in varying amounts, according to controlling impulses, between two receiving conduits, either of which may serve as a supply conduit to the servo, motor and the other as exhaust, outlets in the conduits intermediate the ends thereof through which the pressure fluid passes only in the direction of discharge, and means for alternatively allowing passage of the pressure fluid through said outlets in accordance with the direction of the difference of pressure in said receiving conduits. As applied to a jet-pipe relay, an adjustable jet pipe 10 extends into an oil catcher 11 on a block 12 having conduits 13, 14 communicating with pressure conduits 15, 16 leading to opposite ends of a control device comprising a cylinder 18 with a piston 19. A valve 22 slidable in a cylindrical bore 21 in a housing 17 is adapted to byepass the oil exhausted from the cylinder 18 to a reservoir whence it is again pumped to the jet pipe, thus preventing the low pressure oil from flowing along the whole length of the return conduit 15, or 16 and setting up back pressure or interfering with the action of the jet pipe. The valve which is normally held centrally by springs 30, has cored passages 23, 24, one end of each of which is in communication with conduit 15 or 16, the other end of each being adapted to register with an annular passage 27 in the cylinder wall which is in communication with the reservoir. Projections 29 limit the valve movements. As shown, pressure oil is being delivered through conduits 13, 15 to left-hand side of piston 19 with the result that the valve is forced to the right. In this position, the exhausted oil, through conduit 16, passes through cored opening 24 and annular passage 27 to the reservoir and does not reach conduit 14. It is desirable to maintain a liquid level in the oil catcher 11 and this is effected by having the openings 23, 24 somewhat smaller than the orifices a, b into which the jet pipe discharges. In a modification, Figs. 3, 4 (not shown), each conduit has a separate valve, each valve having a tapering internal passage from the inlet to the outlet end. The valves do not entirely close the passage leading back to the jet pipe, so that a small amount of oil is permitted to return and maintain a level in the catcher 11. In the modification, Fig. 5, the relief valves 65, 66 are combined with the distributer block. The lower end of the jet pipe is surrounded by a conical tube 52. The oil is discharged into passages 53, 54 leading to conduits 57, 58. The casing 55 has cylindrical bores 61, 62 communicating at their inner ends with the passages 53, 54 and near their outer ends with conduits 57, 58 through lateral openings 63, 64. Hollow piston valves 65, 66 are inserted in the bores and have end ports 67, 68 adapted to be closed by spring-loaded valves 69, 70. The valves 65, 66 are biassed to move outwardly by tension springs 73, 74 and when in this position, cover annular ports 75, 76 leading to byepass conduits 77, 78 in communication with the oil catcher 51. As shown, oil is being discharged into conduit 53 and pressure has opened the valve 69 to allow oil to flow to opening 63 and conduit 57. The oil returning through conduit 58 enters right-hand cylinder through opening 64 and moves piston valve 66 to the left to uncover the port 76 and permit oil to pass to the oil catcher from which excess overflows into a reservoir. A similar action takes place when the flow and the positions of the valves are reversed. The modification, Fig. 8, is particularly adapted for use in relay systems operating with low-pressure fluid such as air and wherein a certain pressure must be maintained in the low-pressure line. A jet pipe 80 discharges into conduits 81, 82 leading to the cylinder 83. The valves, which are adapted to relieve only partly the pressure on the return side, each has a casing in sections 85, 86 with a diaphragm 87 clamped between them. The upper section 85, of the casing has a pressure relief conduit 88, the inner end of which terminates in a seat for a valve 91 having an extension 92 guided in a sleeve 93 in the casing section 86. This valve is normally held closed by a spring 94 and is of larger diameter than the seat 90 in order to provide a seat for an annular valve plate 96 secured to and held normally seated by the diaphragm, but adapted to be opened by the flow of fluid. The righthand valve 96 is shown open and fluid can pass to the right-hand end of cylinder 83. The fluid from the left-hand end is relieved through conduit 88 until its pressure balances that of spring 94 plus the pressure in conduit 82 on the jet side of the diaphragm. Thus a pressure is maintained in the lower pressure line. A series of radial bars 97 limits the opening of the diaphragm valve. U.S.A. Specification 1,558,529 is referred to.