Patent GB-929742-A (GB)
Title: Improvements in or relating to control of hydraulic power systems
IPC: H01H33/34
Filed: 1961-11-22
Abstract: 929,742. Hydraulic actuation of switches. J. L. GRATZMULLER. Nov. 22, 1961 [Nov. 28, 1960], No. 41743/61. Class 38 (5). [Also in Group XXIX] A control device for an hydraulic power system having a service line 3, Fig. 2, which may lead to a single-acting jack controlling a circuit-breaker, and an exhaust line 4 or receiver, an hydraulic accumulator with a free piston 2, a selector valve assembly 5 selectively movable by external agency to a first position in which the service line is vented to exhaust and the accumulator is isolated and a second position in which the service line is connected to the accumulator and the exhaust line or receiver is isolated, and a mechanical element 18 on the device engageable by the free piston of the accumulator at a predetermined position of its liquid-expelling stroke and movable thereby to select temporarily an intermediate setting of the valve assembly in which the service line and the accumulator are both vented to exhaust. The valve assembly may consist of a spool having lands 6, 7 which control the service line 3, the exhaust line 4 and a line 11 leading to the accumulator. The line 11 has a cock 15 controlling the connection to a line 12 leading to the upper end of a cylinder 9 having a piston 8 joined by a rod to the land 6, 7 and the element 18. A cock 16 and line 14 join the line 12 to the exhaust line 4 and a line 13 having a restriction 17 joins the cylinder 9 to the service line 3. With the accumulator charged, the service line leading to the jack of the circuit-breaker is pressurized by temporarily opening cock 15 to connect the accumulator to the cylinder 9 to move the piston 8 downwardly against the pressure of a spring 10 so that land 7 closes the exhaust line 4 and land 6 opens the line 11 to the service line 3. The pressure in cylinder 9 when the cock is first opened does not pass to the service line because of the restriction 17 but the restriction does not prevent the pressure in the cylinder from eventually building up to that in the service line to hold the piston and lands in their lower positions so that the cock 15 can be re-opened. Opening of the cock 16 connects the cylinder 9 to the exhaust line to permit the spring 10 to raise the piston 8 and lands 6, 7 to their upper position wherein the accumulator is isolated and the service line 3 is connected to the exhaust line 4. If, when the accumulator is connected to the service line, i.e. when the piston 8 and lands 6, 7 are in their lower position, the quantity of liquid in the accumulator drops to a predetermined low level, the piston 2 engages the element 18 to move the lands 6, 7 to an intermediate position wherein both the accumulator and service line are connected to exhaust. The line 13 vents the cylinder 9 to the exhaust line and enables the piston 2 and spring 10 to raise the piston 8 and lands 6, 7 to their upper position wherein the accumulator is isolated to enable it to be recharged with liquid. The embodiment shown in Fig. 4 operates in the same manner as the embodiment described above but the selector valve assembly has separate conical parts 6, 7 engageable on seatings in a plug 5 mounted in a block 19 forming a mount for the accumulator 1 and a receiver 24, the exhaust line consisting of annular passageway between a nut 37 and the plug 5. The element 18 engageable by the piston 2 is urged away from the part 6 by a spring 26, and a rod 25 is secured to the part 7 to displace the part 6 from its seating where a cock 15 is temporarily opened to connect the accumulator to a line 12 leading by way of a one-way valve 28 to the cylinder 9 and piston 8, the accumulator then being connected to the service line 3. Thereafter, the cock 15 can be closed, the valve parts being retained in position by pressure from the service line acting through line 13 and restriction 17 on the piston 8. The pressure in cylinder 9 can be connected by a passage 35 to the receiver 24 when a ball valve 38 is lifted from its seating by operation of a solenoid 36 to permit the piston 8 to move upwardly and valve part 6 to re-engage its seating and valve part 7 to lift from its seating thus connecting the service line to the receiver. If, when the service line is connected to the accumulator, the quantity of liquid in the accumulator falls to a predetermined low level, the piston 2 moves the element 18 upward, the movement being transmitted by the spring 26 to the part 6 and by the rod 25 to the part 7 so that both valve parts are unseated and the accumulator and service line are both connected to the receiver 24. When the pressure ,has dropped in cylinder 9, the piston 8 is raised to its upper position by the spring 10 to permit valve 6 to close and the accumulator to be recharged. An excess pressure valve 31 may be provided for the cylinder 9. Specification 801,346 is referred to.