Patent GB-266579-A (GB)
Title: Improvements in mechanism for controlling valves
IPC: F16K1/12
Filed: 1926-05-31
Abstract: 266,579. Blakeborough, R. A., (Larner Engineering Co.). May 31, 1926. Valves controlled by pilot or relay valves.-A valve device particularly adapted for use on hydraulic pipe lines and to close automatically to prevent back flow, or to close in the event of an abnormal flow is actuated by a piston working in a cylinder provided with means whereby either end of which can be connected to the pipe line above or below the main valve, a blow-off valve being fitted adapted to release the upstream pressure on the piston when conditions become abnormal. Fig. 1 shows the application of the invention to a valve of the kind in which a valve member 7 is formed integrally with a piston 8 adapted to work in an inner cylinder 6 arranged axially in the pipe line, so that the valve member may co-operate with a seat formed on a contracted part of the main conduit. The space inside the plunger is connected through port 10, pipe 23, throttle valve 25, non-return valve 24, and pipe 20 to the upstream side 1 of the main valve, while the annular space 9 around the plunger is connected through a port 11 and pipe 27 to a blow-off valve 29 of any suitable electrical, mechanical, or hydraulic construction. The pipe 27 is also connected through a non-return valve 22, pipes 21 and 20 with the upstream pipe 1, and through a non-return valve 32, throttle valve 33, and pipe 30 with the actuating cylinder 31. The actuating cylinder houses a piston 17 having a rod 16 connected to a rack 15 engaging a pinion on a shaft 12 carrying a second pinion engaging a rack on the main valve spindle 14, which spindle carries a pilot valve co-operating with a seat in the nose of the plunger. The piston is subject to up and down stream pressures under the control of coupled auxiliary cocks 36, 44 and in the position shown upstream pressure admitted through valve 38 and pipe 34 passes through a passage 47 in the cock 36 and pipe 35 with a throttle valve 37 to the right hand side of the piston. Downstream pressure admitted through a pipe 45 and throttle valve 46 passes through passage 49 in a cock 44, pipe 43, passage 48 in cock 36 and pipe 41 with throttle valve 42 to the left hand side of the piston. This distribution of pressures holds the piston towards the left and the main valve in the open position. If the pressure upstream is not maintained as for example by the interruption of the power supply to a motor driven pump the blow off valve 29 is opened by an electric solenoid, so reducing the pressures in the chambers 9 and 31 causing the valve 7 to close. When the upstream pressure is restored pressures will build up in the chambers 9 and 31 and the main valve automatically re-open. To enable the valve to close automatically in the event of an abnormal velocity of flow the valves 36, 44 are connected together and to a piston 56 by a link 57. The piston 56 works in a cylinder 63 provided with an adjustable stop 61 and having upstream pressure supplied to both ends, directly to the lift hand end through a pipe 58, and through a throttle valve 60 and pipe 59 to the right hand end. The right hand end is also connected through a pipe 62 and valve 62<a> to the valve chamber 64 of a control valve 68. This valve is actuated by a piston subject to up and down stream pressures admitted through pipes 73, 71 and when the difference between these two pressures exceeds a predetermined minimum owing to an increased velocity of the flow the valve 68 opens to vent the chamber 63, thus reversing the valves 36, 44 and closing the main valve. A pipe connection 27a controlled by a valve 27b connects the pipe 27 with the valve chamber 64, so that by closing the valve 62<a> and opening the valve 27<b> the cylinder 63 can be put out of action and the valve 68 directly control the pressures in the chambers 9 and 31. If the pressure in the downstream conduit is to be restored by pressure past the main valve, the cylinder 55 is temporarily put out of commission by closing cocks 53, 52, and 27<b> and the valves 36, 44 reversed by hand the throttle 60 being opened up to facilitate this movement. An auxiliary pressure supply pipe 51, and stop valves 52, 53 are provided so that the main valve may be actuated when no pressure exists in the main conduit. To control the main valve for throttling purposes the actuating piston 17 is arranged to open an escape aperture for the actuating fluid after the piston and therefor the main valve has made a predetermined movement. In the form shown in Fig. 6, a tube 74 having an enlarged head 74<a> with side ports 74b co-operating with the piston is mounted within the piston rod 16 and is adjusted to give the required opening of the main valve by hand actuated bevel and screw gear 75, 77. In a modification a solid rod attached to the piston co-operates with an adjustable ported tube. Fig. 5 shows an alternative construction for actuating the valves 36, 44. Upstream pressure is supplied through pipes 163, 164 to both sides of a piston 162 connected by lever mechanism to the link 57. When the pipe line pressure drops due to an increased velocity the valve 167 is opened by the weighted lever 168, so connecting the space above the valve to a drain pipe 16 and permitting the conduit pressure beneath the piston to raise the same and reverse the valves 36, 44. Modifications are described in which an horizontal or vertical cylinder containing a piston controlled by a blow off valve similar to the valve 29 and coupled valves similar to the valves 36, 44 is linked to a butterfly valve in the main conduit. In a further modification the piston is directly connected to a sluice valve and the connection to the lower part of the cylinder made to a number of ports cause the main valve to seat gently. A Venturi pipe or Pitot tubes may be fitted to the main conduit to increase the pressure difference available for actuating the main valve.