Two-Stage Valve Arrangement for Hydraulic Control of a Piston-Cylinder Arrangement of a High- or Medium-Voltage Power Switch

Abstract

A valve arrangement for hydraulic control of a piston-cylinder of a power switch (7) contains a main stage having a first main valve (31) and a second main valve (32), and a pilot stage having at least one pilot valve (3, 4). In order to permit the first main valve (31) to remain securely in the opened state, even in the event of pressure oscillations, the main valve has a total of four control surfaces, of which a second (F5) and a third (F6) control surface operate in a closing manner and a fourth control surface (F7) operates in an opening manner. For this purpose, the second control surface (F5) is connected to the high-pressure line (P), the third control surface (F6) is connected to the low-pressure line (T), and the fourth control surface (F7) is connected to the output-side valve connection (35) of the first main valve (31). The size ratio of the opening control surfaces (F4, F7) to the closing control surfaces (F5, F6) is selected such that in the open condition of the first main valve (31) an opening resulting force is maintained.

Claims

1. A two-stage valve arrangement for the hydraulic actuation of a piston in a cylinder of a high voltage or medium voltage power switch, the two-stage valve arrangement comprising: a main stage with a first main valve configured as a 2/2-way valve and a second main valve configured as a 2/2-way valve, a high pressure line configured to conduct a fluid under high pressure being connected directly to an inlet-side valve connector of the first main valve, and a low pressure line configured to conduct a fluid under low pressure being connected directly to an inlet-side valve connector of the second main valve, an outlet-side valve connector of the first main valve and an outlet-side valve connector of the second main valve being connected hydraulically to one another and to a space situated on one side of the piston, and a pilot control stage with at least one pilot control valve having two connectors on the inlet side, one of the two connectors being connected to the high pressure line and the other of the two connectors being connected to the low pressure line, a hydraulic pilot control outlet of the pilot control stage being connected both to a first control face of the first main valve, to act in an opening manner, and to a first control face of the second main valve, to act in a closing manner, wherein the pilot control stage is configured to establish a connection between the high pressure line and the hydraulic pilot control outlet in a first position of the at least one pilot control valve, such that the high pressure acts on the first control face of the first main valve and on the first control face of the second main valve to cause an opening of the first main valve and a closing of the second main valve, with the result that fluid under high pressure is fed to the space which is situated on the one side of the piston wherein the pilot control stage is configured to establish a connection between the low pressure line and the hydraulic pilot control outlet in a second position of the at least one pilot control valve, such that the low pressure acts on the first control face of the first main valve and on the first control face of the second main valve to cause a closing of the first main valve and an opening of the second main valve, with the result that fluid is discharged in a direction of the low pressure line from the space which is situated on the one side of the piston, wherein the first main valve further comprises a second control face configured to act in a closing manner, a third control face configured to act in a closing manner, and a fourth control face configured to act in an opening manner, the second control face of the first main valve being connected to the high pressure line, the third control face of the first main valve being connected to the low pressure line, and the fourth control face of the first main valve being connected to the outlet-side valve connector of the first main valve, and wherein a size ratio of the first and fourth control faces of the first main valve with respect to the second and third control faces of the first main valve is configured such that a resulting force which acts in an opening manner remains in force in an open state of the first main valve.

2. The two-stage valve arrangement as claimed in claim 1, wherein a sum of an area size of the first control face of the first main valve and an area size of the fourth control face of the first main valve is greater than an area size of the second control face of the first main valve.

3. The two-stage valve arrangement as claimed in claim 2, wherein the sum of the area size of the first control face of the first main valve and the area size of the fourth control face of the first main valve is equal to a sum of the area size of the second control face of the first main valve and an area size of the third control face of the first main valve.

4. The two-stage valve arrangement as claimed in claim 1, wherein the second control face of the first main valve is at least as large as the fourth control face of the first main valve.

5. The two-stage valve arrangement as claimed in claim 1, further comprising a spring-based latch configured to latch in an open state of the second main valve.

6. (canceled)

7. The two-stage valve arrangement as claimed in claim 1, wherein the second main valve further comprises a second control face connected to the low pressure line and a third control face connected to the outlet-side valve connector of the second main valve.

8. The two-stage valve arrangement as claimed in claim 1, wherein the pilot control stage comprises two 2/2-way valves as pilot control valves.

9. The two-stage valve arrangement as claimed in claim 1, wherein the first main valve is provided with a manual restoring option.

10. The two-stage valve arrangement as claimed in claim 1, wherein the second main valve is provided with a manual restoring option.

11. The two-stage valve arrangement as claimed in claim 1, wherein the first and second main valves are each provided with a manual restoring option.

Description

[0031] The invention and its possible configuration are to be described in greater detail using the exemplary embodiments which are shown in the further drawings, in which:

[0032] FIG. 1 shows a first known two-stage valve arrangement for the actuation of a piston and therefore of a high voltage power switch,

[0033] FIG. 2 shows a second known two-stage valve arrangement having an orifice for discharging a leakage flow,

[0034] FIG. 3 shows a third two-stage valve arrangement in accordance with the invention,

[0035] FIG. 4 shows one embodiment of the first main valve from FIG. 3, and

[0036] FIG. 5 shows one embodiment of the second main valve from FIG. 3.

[0037] FIG. 3 shows one possible embodiment of a two-stage valve arrangement in accordance with the invention. The two-stage valve arrangement serves for the hydraulic actuation of a piston 6 in a cylinder 12 of a high voltage or medium voltage power switch 7. Here, the two-stage valve arrangement comprises a main stage with two 2/2-way valves which are called a first main valve and a second main valve 32, and a pilot control stage with two 2/2-way valves which are called a first pilot control valve 3 and a second pilot control valve 4. Here, identical designations are used for the consistent elements in FIGS. 1 and 2.

[0038] A high pressure line P which conducts a fluid under high pressure is connected directly to an inlet-side valve connector 33 of the first main valve 31, and is fed from a high pressure accumulator 9. The fluid is preferably a hydraulic oil, but can also be compressed air, for example. A low pressure line T is connected directly to an inlet-side valve connector 34 of the second main valve 32, the low pressure line T conducting the fluid under low pressure and being connected to a low pressure tank 8.

[0039] On the inlet side, the pilot control stage has two connectors, one of the connectors, to be precise the inlet-side connector 37 of the first pilot control valve 3, being connected to the high pressure line P, and the other one of the connectors, namely the inlet-side connector 38 of the second pilot control valve 4, being connected to the low pressure line T.

[0040] An outlet-side valve connector 35 of the first main valve 31 and an outlet-side valve connector 36 of the second main valve 32 are connected to one another at a hydraulic connecting node Z, and are connected via the latter to a space 10 which is situated on one side of the piston 6, that is to say the outlet-side valve connectors 35, 36 of the main valves 31, 32 feed directly into the space 10.

[0041] The pilot control stage has a hydraulic pilot control outlet X which is connected in each case to the outlet-side connector of the first and second pilot control valve 3, 4. The pilot control outlet X in turn is connected to a first control face F4, acting in an opening manner, of the first main valve 31 and to a first control face F8, acting in a closing manner, of the second main valve 32.

[0042] In a first position of the pilot control valves 3, 4, the pilot control stage establishes a connection between the high pressure line P and the hydraulic pilot control outlet X. In said first position, the first pilot control valve 3 is open and the second pilot control valve 4 is closed. The high pressure which thereupon acts on the first control faces F4, F8 of the main valves 31, 32 brings about opening of the first main valve 31 and closing of the second main valve 32, with the result that the fluid under high pressure is fed to the space 10 which is situated on one side of the piston 6, as a result of which the high voltage or medium voltage power switch 7 is switched on, that is to say is closed.

[0043] In a second position of the pilot control valve 3, 4, the pilot control stage establishes a connection between the low pressure line T and the hydraulic pilot control outlet X. In said second position, the first pilot control valve 3 is closed and the second pilot control valve 4 is open. The low pressure which thereupon acts on the first control faces F4, F8 of the main valves 31, 32 brings about closing of the first main valve 31 and opening of the second main valve 32, with the result that fluid is discharged in the direction of the low pressure line T from the space 10 which is situated on one side of the piston 6, which leads to switching off, that is to say opening, of the high voltage or medium voltage power switch 7.

[0044] According to the invention, the first main valve 31 has three further control faces, as can also be gathered from FIG. 4 which shows one possible embodiment of the first main valve 31. In addition to the first control face F4 of the first main valve, which first control face F4 acts in an opening manner, there are a second and a third control face F5 and F6 of the first main valve which both act in a closing manner. A fourth control face F7 of the first main valve in turn acts in an opening manner.

[0045] The second control face F5 of the first main valve is connected within the two-stage valve arrangement to the high pressure line P; the third control face F6 of the first main valve is connected to the low pressure line T, and the fourth control face F7 of the first main valve is connected to the outlet-side valve connector 35 of the first main valve 31.

[0046] In accordance with the invention, the area ratio of the control faces F4 and F7, acting in an opening manner, of the first main valve with respect to the control faces F5 and F6, acting in a closing manner, of the first main valve is such that a resulting force which acts in an opening manner remains in force in the open state of the first main valve, with the result that the first main valve 31 remains reliably in the open state, even if pressure fluctuations should occur in the high pressure line P.

[0047] In the following text, the area size of the first control face F4 of the first main valve is denoted by AF4, and the area sizes of the remaining control faces F5, F6, F7 of the first main valve are denoted analogously by AFS, AF6 and AF7. In the embodiment in accordance with FIG. 4, the area sizes AF4, AFS, AF6 and AF7 are selected in such a way that the sum of the size of the first control face (AF4) of the first main valve and the size of the fourth control face (AF7) of the first main valve is precisely as great as the sum of the size of the second control face (AF5) of the first main valve and the size of the third control face (AF6) of the first main valve, that is to say AF4+AF7=AF5+AF6. In this way, the condition is also met at the same time that the sum of the size of the first control face (AF4) of the first main valve and the size of the fourth control face (AF7) of the first main valve is greater than the size of the second control face (AF5), that is to say AF4+AF7>AF5. Moreover, the second control face of the first main valve is at least as large as the fourth control face of the first main valve, that is to say AF5AF7. In the refinement in accordance with FIG. 4, the former size ratio ensures that, in the open state of the first main valve 31, if high pressure prevails against the first (F4), second (F5) and fourth (F7) control face, an unexpected increase in the pressure at the second control face F5 does not lead to undesired closing of the first main valve. The latter size ratio ensures that, at the beginning of a desired closing operation of the first main valve 31, if a change is made from high pressure to low pressure at the first control face F4, the high pressure at the second control face F5 is sufficient to initiate the closing operation.

[0048] As shown in FIGS. 3 and 4, moreover, the first main valve 31 has a latching means 40 which is based on spring force and ensures that the first main valve 31 remains as reliably as possible in the open state, until a sufficiently great closing force counteracts this.

[0049] Moreover, the first main valve 31 is provided with a manual restoring option 42, with the aid of which the first main valve can be moved into the closed state again after a transport-induced movement.

[0050] FIG. 5 shows one possible refinement of the second main valve 32. Said second main valve 32 has a total of three control faces, that is to say, in addition to the first control face F8, a second control face F9 of the second main valve, and a third control face F10 of the second main valve. In the two-stage valve arrangement in accordance with FIG. 3, the second control face F9 of the second main valve is connected to the low pressure line T, and the third control face F10 of the second main valve is connected to the outlet-side valve connector 36 of the second main valve 32.

[0051] The second main valve 32 is also provided with a latching means 39 which is based on spring force and latches in in the open state of the second main valve. Here, said latching means 39 which is based on spring force counteracts, in particular, the introduction of force of the restoring spring 41, with the result that a switching position memory can be realized in this way, that is to say the second main valve is held in the open state even after the high voltage or medium voltage power switch 7 is switched off, if the second main valve is completely without pressure.

[0052] In the case of the second main valve 32 of FIG. 5, the restoring spring 41 is also supplemented by a manual restoring option 42, with the result that the second main valve can also be moved into the closed state again after a transport-induced movement and undesired latching in of the latching means 39.