GB2139327A

GB2139327A - Hydraulic valve arrangement

Info

Publication number: GB2139327A
Application number: GB08411514A
Authority: GB
Inventors: Weirich Walter; Detthers Michael
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1983-05-07
Filing date: 1984-05-04
Publication date: 1984-11-07
Also published as: GB8411514D0; ES8502518A1; ES532258A0; DE3316736A1; PL247573A1; BE899566A; GB2139327B; PL145069B1; DE3316736C2

Abstract

A hydraulic valve arrangement for a mine roof support unit comprises a valve block 1 housing a valve 17 for controlling the flow of pressurised hydraulic fluid from a hydraulic pressure line to a hydraulic ram. The valve 17 has a closure member 23 which can be opened by a thrust piston 29. The outlet side of the valve 17 is connected to a relief duct 31 provided with an auxiliary valve 33,35. A control member 30 is provided for actuating the auxiliary valve 33,35. The arrangement is such that the auxiliary valve 33,35 closes the relief duct 31 when the valve 17 is open, and opens the relief duct when the valve 17 is closed. <IMAGE>

Description

SPECIFICATION Hydraulic valve arrangement This invention relates to a hydraulic valve arrangement for a hydraulic high-pressure system, and in particular to a hydraulic valve arrangement associated with a hydraulic consumer unit of a mine roof support unit.

A hydraulic valve arrangement is used as a safety valve in mines where a hydraulic ram is required to be locked against unintentional extension or retraction, which might occur, for example, when an associated hydraulic control system fails, or when a valve develops a leak.

It is known to provide the roof bar of a mine roof support unit with a roof bar extension, which can be slidably advanced towards the workface by means of a hydraulic ram or rams. In a roof support system constituted by a plurality of such mine roof support units, it is known to provide a synchronised control means, which is used to control the advance of the roof bar extensions automatically in dependence upon the advance distance of the mine roof support units or the advance distance of the associated longwall conveyor.In order to prevent any unrequired extension of the roof bar extensions (which would lead to difficulties in operation of the equipment), in the event of faulty operation of the hydraulic control system, for example in the event of a valve developing a leak, safety valves are incorporated in the connections between the advance rams for the roof bar extensions and the associated hydraulic pressure line.

The aim of the invention is to provide a valve arrangement for a hydraulic ram of a mine roof support unit which, even when its safety valve develops a leak, ensures that the hydraulic ram is hydraulically locked with respect to the associated hydraulic pressure line.

A further aim is to provide a valve arrangement which is relatively simple, and whose operating parts can be easily assembled.

The present invention provides a hydraulic valve arrangement for a mine roof support unit, the valve arrangement comprising a valve for controlling the flow of pressurised hydraulic fluid from a hydraulic pressure line to a hydraulic consumer unit associated with the mine roof support unit, the valve having a closure member which can be opened by an actuating member, wherein the outlet side of the valve is connected to a relief duct provided with an auxiliary valve, a control member being provided for actuating the auxiliary valve, the arrangement being such that the auxiliary valve closes the relief duct when the valve is open, and opens the relief duct when the valve is closed.

The relief duct permits control of the operation of the valve arrangement since, if the valve develops a leak, the leakage fluid is discharged at the downstream end of the relief duct, thereby indicating to the operator that the valve arrangement is not functioning correctly. The relief duct also prevents, in the event of the valve developing a leak, the build-up of back-pressure at the outlet end of the valve. Such a build-up of back-pressure could interfere with the actuation of the valve.

Alternatively, if the valve arrangement was in the blocking position, build-up of back-pressure could lead to an undesirable application of pressure to the associated hydraulic consumer unit (ram).

Advantageously, the actuating member is a control piston which is subjected to the pressure of hydraulic fluid in a hydraulic control line. The relief duct is automatically closed when the valve is opened by the associated control piston. Thus, when the valve is in the open position, no pressurised hydraulic fluid can flow away along the relief duct.

Preferably, the arrangement further comprises a second valve positioned on the outlet side of the first-mentioned valve, the relief duct being connected to the inlet side of the second valve, the arrangement being such that the pressure of the hydraulic fluid in the hydraulic pressure line tends to close the firstmentioned valve and open the second valve.

The second valve, therefore, blocks flow in both directions as long as it is not activated.

Advantageously, each of the valves is a spring-loaded ball valve.

In a preferred embodiment, the closure member of the auxiliary valve is arranged on the control piston. Advantageously, the arrangement further comprises a thrust piston arranged between the control piston and the first-mentioned valve, the thrust piston being provided with a through bore which interconnects the spaces at the opposite ends of the thrust piston, and wherein the relief duct extends from the space between the thrust piston and the control piston, the arrangement being such that the control piston has lost motion with respect to the thrust piston. Preferably, the end of the thrust piston adjacent to the control piston is provided with a valve seat for the auxiliary valve, the closure member of the auxiliary valve being arranged on the control piston.Conveniently, the closure member of the auxiliary valve is constituted by a ball which is seated in a recess formed in the control piston.

The entire valve arrangement, with its various valves and other operating parts, may form an enclosed component. Preferably, the arrangement is housed in a valve block, and the first-mentioned valve is constituted by a valve cartridge which is screwed into the valve block, the valve block being provided with respective ports for the hydraulic pressure line, the hydraulic control line, and a line leading to the hydraulic consumer unit. Advantageously, the first-mentioned valve and the second valve are arranged respectively in first and second bores in the valve block, said bores intersecting at right-angles, the first bore being a stepped bore, and the relief duct intersecting the first bore at right-angles. The first bore may also accommodate the control piston.

In a preferred embodiment, the valve cartridge comprises a bush fitted in the first bore of the valve block, the bush accommodating the closure member of the first-mentioned valve at one end thereof, and the thrust piston being inserted into the bush from the opposite end.

A valve arrangement constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing, the single figure of which is a sectional view of the arrangement.

The drawing shows a valve arrangement having a cuboidal valve block 1, one surface of which is provided with ports 2, 3, and 4.

The port 2 is an inlet port which is connected to a hydraulic pressure line (not shown), the port 3 is an inlet port which is connected to a hydraulic control line (not shown), and the port 4 is an outlet port connected to a hydraulic ram (not shown). The valve block 1 is provided with three mutually-parallel, coaxial bores 5, 6 and 7, which terminate respectively at the ports 2, 3 and 4. The bore 6 is a stepped bore. The inner end of the bore 5 leads into a transverse bore 9, the external end of which is closed by a screw plug 8, and the internal end of which establishes connection with the bore 6. The bore 7 is likewise connected to the bore 6 by way of a transverse bore 10. A valve 11 is fitted in the transverse bore 10, the valve 11 having a closure member 12 in the form of a ball.The closure rnember 12 is pressed against a valve seat 14 by a spring 13, and is located within a valve housing 1 5. The valve housing 1 5 is a screw-threaded plug which is screwed, from the exterior, into the transverse bore 10. The valve housing 1 5 has a stepped, axial bore which accommodates the closure member 12 and the spring 13, and also defines the valve seat 14. The valve 11 can be opened by the pressure of hydraulic fluid supplied by the hydraulic pressure line via the inlet port 2, and against the force of the spring 1 3.

The port 3 is constituted by a connector which is screwed into the bore 6, a valve cartridge 1 6 being screwed into the other end of the bore 6. The valve cartridge 16 houses a valve 17, and comprises a cylindrical housing 1 8 which accommodates a valve spring 19, a valve cap 20, and a bush 21. One end of the bush 21 is screwed into the open end of the housing 18, and the other end of the bush is screwed, at 22, into the bore 6, sealing means being provided between the bush and the bore 6. The bush 21 accommo- dates a ball which constitutes the closure member 23 of the valve 17, and the bush also constitutes a valve seat 24 for the closure member 23. The spring 1 9 acts on the closure member 23 by way of the valve cap 20 and a push rod 25 which is displaceably guided in the bush 21.The bush 21 has radial bores 26 which establish connection between the transverse bore 9 and the interior of the bush 21 at the inlet end of the valve 17.

The space 27 at the outlet end of the valve 1 7 communicates, through radial bores 28, with the transverse bore 10 which accommodates the valve 11. A thrust piston 29 is displaceably guided within the bush 21 (or within an axial extension thereof). A control piston 30 is provided between the thrust piston 29 and the port 3, the control piston having a predetermined amount of lost motion in relation to the thrust piston 29. The control piston 30 is guided in a cylindrical, widened portion of the stepped bore 6, and the thrust piston 29 can be acted upon by pressurised hydraulic fluid supplied via the port 3. A relief and leakage-control duct 31 extends from the space between the control piston 30 and the thrust piston 29, and terminates at an outer face of the valve block 1.The duct 31 extends at right-angles to the bore 6, and communicates with the atmosphere at its outer end. The thrust piston 29 has a through bore 32 which hydraulically connects the spaces at its two opposite ends. The space 27 at the outlet end of the valve 1 7 is, therefore, hydraulically connected, by way of the bore 32, to the space located between the thrust piston 29 and the control piston 30, and hence to the relief and leakage-control duct 31.

An auxiliary valve is associated with the duct 31, the auxiliary valve having a closure member 33 constituted by a small ball. The closure member 33 fits into a recess 34 formed in the control piston 3t, and bears against a valve seat 35 when the auxiliary valve is in the closed position, the valve seat being formed integrally at that end face of the thrust piston 29 that is presented to the control piston 30.

In use, the port 2 is connected to the hydraulic pressure line, the port 4 is connected to the cylindrical working chamber of the associated hydraulic ram, and the port 3 is connected to the hydraulic control line.

Under normal conditions, the valve 1 7 is held, in the illustrated closed position, by the force arising from the hydraulic pressure from the hydraulic pressure line, and the force exerted by the spring 19. In this closed position, the valve 1 7 prevents the flow of pressurised hydraulic fluid to the downstream valve 11. The valve 11 is also held in the closed position, by its spring 1 3 (and possibly also by the hydraulic pressure exerted by the associated hydraulic ram). It is, therefore, impossible for the hydraulic pressure fluid from the hydraulic pressure line to pass through the valve arrangement to the outlet port 4, even upon failure of the control valve associated with the hydraulic ram or of some other valve forming part of an associated automatic control means or an associated synchronised control means.If the valve 1 7 develops a leak, pressurised hydraulic fluid can pass through the bores 5 and 9, and into the space 27 at the outlet end of the valve 17. However, the space 27 communicates with the relief and leakage-control duct 31, by way of the bore 32 and the open auxiliary valve 33 and 35, so that back-pressure (which could adversely affect valve operation) cannot build up at the outlet end of the valve 17. Leakage fluid flows outwards through the duct 31, and the discharge or dripping of the leakage fluid provides the operator with a visible indication that the valve arrangement, that is to say its valve 17, is not operating correctly.

In order to apply pressurised hydraulic fluid to the hydraulic ram connected to the outlet port 4, pressurised hydraulic fluid is applied to the control piston 30 via the hydraulic control line and the inlet port 3. When this happens, the control piston 30 first takes up the lost motion, during which time the ball 33 of the auxiliary valve lies against its valve seat 35, and thus cuts off communication between the space 27 and the relief and leakagecontrol duct 31.When the control piston 30 moves further, the thrust piston 29 moves with it and lifts the closure member 23 away from its seat 24, against the return force of its spring 1 9. Hydraulic pressure fluid can then flow from the inlet port 2 to the valve 11 via the open valve 1 7. The closure member 1 2 of the valve 11 is lifted from its valve seat 14 by the hydraulic pressure, against the return force of its spring 13, so that hydraulic communication with the outlet port 4 (and therefore with the cylindrical working chamber of the associated hydraulic ram) is established.

Since the auxiliary valve 33, 35 is closed when the valve arrangement is open, no pressurised hydraulic fluid can flow out through the bore 32 and the relief and leakage-control duct 31 when the arrangement is in this operating position.

The valve arrangement remains open as long as pressurised hydraulic fluid is applied to the control piston 30. When the control pressure ceases, the valve 1 7 closes under the force of its spring 19, and the valve 11 also closes under the force of its spring 1 3. At the same time, the auxiliary valve 33, 35 opens to establish communication between the space at the outlet end of the valve 1 7 and the relief leakage-control duct 31.

Claims

1. A hydraulic valve arrangement for a mine roof support unit, the valve arrangement comprising a valve for controlling the flow of pressurised hydraulic fluid from a hydraulic pressure line to a hydraulic consumer unit associated with the mine roof support unit, the valve having a closure member which can be opened by an actuating member, wherein the outlet side of the valve is connected to a relief duct provided with an auxiliary valve, a control member being provided for actuating the auxiliary valve, the arrangement being such that the auxiliary valve closes the relief duct when the valve is open, and opens the relief duct when the valve is closed.

2. An arrangement as claimed in claim 1, wherein the actuating member is a control piston which is subjected to the pressure of hydraulic fluid in a hydraulic control line.

3. An arrangement as claimed in claim 1 or claim 2, wherein the valve is a spring-loaded ball valve.

4. An arrangement as claimed in any one of claims 1 to 3, further comprising a second valve positioned on the outlet side of the firstmentioned valve, the relief duct being connected to the inlet side of the second valve.

5. An arrangement as claimed in claim 4, wherein the arrangement is such that the pressure of the hydraulic fluid in the hydraulic pressure line tends to close the first-mentioned valve and open the second valve.

6. An arrangement as claimed in claim 4 or claim 5, wherein the second valve is a springloaded ball valve.

7. An arrangement as claimed in claim 2, or in any one of claims 3 to 6 when appendant to claim 2, wherein the closure member of the auxiliary valve is arranged on the control piston.

8. An arrangement as claimed in claim 2, or in any one of claims 3 to 7 when appen dant-to claim 2, further comprising a thrust piston arranged between the control piston and the first-mentioned valve, the thrust piston being provided with a through bore which interconnects the spaces at the opposite ends of the thrust piston, and wherein the relief duct extends from the space between the thrust piston and the control piston.

9. An arrangement as claimed in claim 8, wherein the arrangement is such that the control piston has lost motion with respect to the thrust piston.

10. An arrangement as claimed in claim 8 or claim 9, wherein the end of the thrust piston adjacent to the control piston is provided with a valve seat for the auxiliary valve, the closure member of the auxiliary valve being arranged on the control piston.

11. An arrangement as claimed in claim 10, wherein the closure member of the auxiliary valve is constituted by a ball which is seated in a recess formed in the control piston.

1 2. An arrangement as claimed in claim 2, or in any one of claims 3 to 11 when appendant to claim 2, wherein the arrangement is housed in a valve block, and wherein the firstmentioned valve is constituted by a valve cartridge which is screwed into the valve block, the valve block being provided with respective ports for the hydraulic pressure line, the hydraulic control line, and a line leading to the hydraulic consumer unit.

1 3. An arrangement as claimed in claim 12, wherein the first-mentioned valve and the second valve are arranged respectively in first and second bores in the valve block, said bores intersecting at right-angles.

14. An arrangement as claimed in claim 13, wherein the first bore is a stepped bore.

1 5. An arrangement as claimed in claim 1 3 or claim 14, wherein the relief duct intersects the first bore at right-angles.

16. An arrangement as claimed in any one of claims 1 3 to 15, wherein the first bore also accommodates the control piston.

1 7. An arrangement as claimed in any one of claims 1 3 to 16, wherein the valve cartridge comprises a bush fitted in the first bore of the valve block, the bush accommodating the closure member of the first-mentioned valve at one end thereof, and the thrust piston being inserted into the bush from the opposite end.

18. A hydraulic valve arrangement substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawing.