Patent GB-780763-A (GB)
Title: Improvements in and relating to the hydraulic control of electric circuit breakers
IPC: F15B13/04
Filed: 1955-01-14
Abstract: 780,763. Actuation of switches. GRATZMULLER, J. L. Jan. 14, 1955 [Jan. 15, 1954; Dec. 28, 1954], No. 1205/55. Class 38 (5). [Also in Group XXIX] Hydraulic control means for a circuit-breaker comprises a resiliently loaded single-acting main hydraulic jack 3, Fig. 2, operative on the circuitbreaker, a main valve 25 for selectively connecting the main jack to a source 1 of hydraulic pressure or to exhaust, a resiliently loaded auxiliary jack 9 whereof the power stroke moves the main valve to connect the main jack to the source of hydraulic pressure, a first control valve 29 to admit hydraulic pressure to the auxiliary jack, a second control valve 24 to exhaust the auxiliary valve, and a restricted hydraulic connection 35 between the main and auxiliary jacks, such connection maintaining hydraulic pressure in the auxiliary jack after the main valve has been moved to connect the main jack to the pressure source and the first control valve has been allowed to close, and until the second control valve has been opened to exhaust the auxiliary jack. The main valve 25 comprises ball valves 25a, 25b controlling an inlet conduit 2b and an exhaust conduit 44 respectively. The valves are operated by a jack piston 8 loaded by a spring 10. The space below the piston 8 may be connected on the one hand to the source 1 through a normally closed feed valve 29 or on the other hand to exhaust through a normally closed exhaust valve 24 and a conduit 54, the valves 29, 24 being operated by the respective electromagnets 6, 15. Once the jack piston 8 is raised to the feed position by the operation of the valve 29, it is maintained in this position although the electromagnet 6 is deenergized by pressure from the circuit 2c leaking through a restriction 35 in a conduit 11a, 11b leading to the jack 9. The restriction 35 is small in comparison with the outlet of the valve 24 so that the jack 9 exhausts easily in the time the electromagnet 15 is energized. The ball valves 25a, 25b are spaced by a tappet rod 26 between them. Non-return valves 30, 31 opening towards the jack 9 are located between the valve 29 and the jack 9 and between the restriction 35 and the jack 9. A separate exhaust valve 38 is associated with the valve 29 to drain off any leakage past the latter, both valves being operated by the electromagnet 6 through a tappet rod 39. A restricted orifice 27 is provided between the source 1 and the valve 25. A pressure-responsive device 34 associated with the supply conduit 2a may be arranged to trip the exhaust valve 24 or to prevent the operation of the valve 29 if the pressure of the source 1 is inadequate. A pressure-responsive device 41 associated with the outlet duct 2c may be utilized to give a pressure reading indicative of the position of the circuit-breaker operating jack. Fig. 3 shows a complete system for operating a circuit-breaker D connecting conductors C<SP>1</SP>, C<SP>2</SP>. The circuit-making operation is effected against a spring Rp by a jack Vp associated with the rapid release device described in Specification 755,096. The jack Vp is supplied with pressure liquid from the pilot jack Va which has a spring-loaded jack piston integral with a lift-type exhaust valve Cp. An integral tappet on the valve Cp opens the feed valve Ap supplied from the source S. The pilot jack is controlled by an inlet valve Aa and an exhaust valve C<SP>1</SP>p operated by electromagnets Ee and Ed respectively. The electromagnet Ed may be energized under the control of a micro-switch operated by a pressure-responsive device M<SP>2</SP> on a fall of pressure in the source S. The same device M<SP>2</SP> may be similarly arranged to prevent the electromagnet Ee from being energized. A further pressure-responsive device may operate through micro-switches to interrupt the circuit to the electromagnet Ee when the main circuit is safely established and to interrupt the circuit of the electromagnet Ed when the main circuit is safely broken. Pressure in the pilot jack is maintained through a restriction 35 in a conduit G. Specification 777,750 also is referred to.