Patent GB-250417-A (GB)
Title: Improvements in control means for valves
IPC: F16K1/12
Filed: 1925-06-02
Abstract: 250,417. Blakeborough, R., A., (Larner Engineering Co.). June 2, 1925. Valves controlled by pilot or relay valves.-A valve actuated by fluid pressure under the control of auxiliary valves has the primary control valve actuated by hand or by an electric or rotary hydraulic motor under the control of an electric switch or secondary auxiliary valve actuated automatically by the pressures in the main or by main pressure under the control of a further hand actuated auxiliary valve. Fig. 1 shows the application of the invention to the control of a main valve of the type comprising an axially arranged valve plunger P slidably mounted in an inner casing so as to form actuating chambers A. B. The supply and exhaust of pressure to and from the chambers A B are controlled by a piston valve 13 adapted in one position to connect an inlet pipe 3 to a pipe 2, leading to the chambers A, and simultaneously connect a pipe 4 leading to the chamber B to the exhaust pipe 15, in an intermediate position to shut off both pipes 2 and 4, and in a third position to reverse the connections. The auxiliary valve spindle 5 is connected by a lever 6 to a screw 7 mounted in brackets 20 so as be capable of slight endwise movement. The screw is provided with a nut 8 mounted on the indicator rod 12 secured to the main valve and is rotated either bv a hand wheel 19 or an electric motor 18 acting through reducing and bevel gear. When the motor is rotated the auxiliary valve is moved to operate the main valve the movement of which transmitted through the indicator rod 12 and nut 8 restores the control valve to its neutral position. The motor is controlled by hand actuated switches 21-24 and an automatic switch 25 actuated by a piston 28 subject to inlet and outlet pressure transmitted through pipes 60, 64. The piston also actuates a secondary control valve 37, the supply of inlet pressure to which is throttled by a valve 35. In view of the fact that the main outlet is smaller than the inlet and the provision of the valve 37 the piston normally remains in its lower position, but in the event of an abnormal out flow the piston rises, closes the switch 25 and so closes the main valve. The switch may be fitted with catches to hold it in the closed position. The chamber 29 above the piston may be fitted with a relief valve loaded by a rolling ball so that the main valve is closed by an abnormal rise of pressure. A hand operated valve may be fitted to this chamber to enable the valve to be closed by hand. The valve 37 may be used for controlling the supply to an impulse wheel which may be used in place of the electric motor. A bye-pass connection 44 provided with a throttling valve 43 and non-return valve 56 connects the chamber A with the outlet to counteract the rapid drop of pressure beyond the main valve as it nears its seat. The pipes 60 64 may lead to the same side of the main valve, in which case the pipe 64 would be fitted with a Pitot tube. In the modification shown in Fig. 6 the control valve spindle 5<1> is connected to a lever 70 pivoted to a bracket on the base-plate and to a differential piston 73 working in a cylinder 72. The cylinder is slidably mounted on fixed tubular supports 75, 76 having inlet ports 77, 78 for pressure fluid so that the piston is biassed to the right and the cylinder to the left. The cylinder is connected by linkage mechanism 86 to the indicator rod and carries a bearing for the hand actuating nut 84 which engages a screwed spindle 83 linked to the lever 70. Operating the hand wheel moves the control valve to actuate the main valve in the appropriate direction which movement shifts the cylinder and allows the biassing pressure to restore the control valve to its neutral position. The relay valve 37 acts to release the pressure from the chamber a and so initiate the closing of the main valve. To throw the relay valve out of action when the hand control is being employed a cock 111 on the conduit 77 is closed by lever 110, which lever is moved to an inoperative position by a link 112 secured to the bearing 80 when automatic control is being used.