The present discovery relates to a hydraulic shield support such as may be used in underground mining. The shield support includes at least two adjustable-length hydraulic props borne on base shoes and supporting a shield, which may be connected through a control bank to a hydraulic fluid supply system. A pressure in excess of the pressure of the hydraulic fluid may be applied in the set condition of the shield support. The shield support may be a stope shield support, but the present discovery is not limited thereto.
In deep mining, hydraulic supports are used to keep the face or working area free and to support the so-called roof. In particular, they may take the form of lemniscate shields, as for example, disclosed in U.S. Pat. Nos. 4,815,898, 6,056,481 or 5,743,679, all of which are hereby incorporated by reference. The main or roof shield is supported by double acting, preferably multiple-stage hydraulic props, which are counter-borne on the base shoes. Setting or removing the shields takes place as a function of pilot signals from an electrical control unit, which automatically activates the actuators, such as e.g. electromagnets, allocated to the hydraulic actuation valves in the control banks. In the hydraulic shield supports currently used in deep mining, a setting pressure of approximately 320 bar may be applied to the hydraulic props and may subsequently be increased to a maximum pressure of approximately 400 bar to support the load of the rock. Both pressures are applied through the control bank.
Provision of the increased pressure through a second, supplementary supply system is known from DE 101 16 916 A1, hereby incorporated by reference. The provision of a principal supply system for a pressure of approximately 300 bar may keep the volume flows, which the supplementary supply system must be able to deliver for the pressure of approximately 400 bar, low, and mean that the supplementary supply system can be embodied with comparatively small cross-sections. This approach requires the laying of a second hydraulic supply system throughout the entire face, in addition to the principal supply system.
There is a constant demand for longer faces and higher-capacity winning and conveyor systems for the economic mining of coal or other minerals from deep faces. Consequently, the roof surface area to be supported by shield supports in the face area increases constantly. To support the rock, it is thus necessary to increase the resistance which can be applied to the shield by the hydraulic props. Fundamentally, the number of hydraulic props, their effective diameter or the pressure of the hydraulic fluid may be increased for this purpose.
The present discovery aims to create a hydraulic shield support with which greater support resistance may be achieved than with existing solutions, preferably without having to change the prop diameter and without additional outlay for piping for a supplementary supply system at a deep face.
The various exemplary embodiments described herein allocate at least one pressure intensifier to a hydraulic shield support, located in the hydraulic pipe system between the hydraulic supply and the hydraulic props. The pressure intensifier utilizes an oscillating intensifying piston, such as in the form of a differential piston which increases the pressure. An increase in pressure to almost any level can be achieved in each shield support by the pressure intensifier with an oscillating intensifier piston allocated to each shield support without having to lay an additional pipe designed for the high pressure throughout the entire face. The pressure intensifiers can supply an increased or intensified pressure which is proportional to the pressure in the supply system and thus to the pressure present at the low-pressure inlet of the pressure intensifier.
In one aspect according to the present discovery, a hydraulic shield support system is provided which is adapted for underground mining. The shield support system comprises one or more base shoes, a shield, and at least two adjustable length hydraulic props disposed on the base shoes. The props are adapted to support the shield. The shield support system further comprises a hydraulic fluid supply and a control bank in fluid communication with the hydraulic fluid supply and the hydraulic props. The system additionally comprises a hydraulic pipe system that provides fluid communication between the hydraulic fluid supply and the hydraulic props. The system further comprises at least one pressure intensifier in fluid communication with the hydraulic pipe system. The pressure intensifier includes an oscillating intensifier piston in the form of a differential piston for effecting an increase in pressure. The discovery includes various configurations of this system.
Further advantages and embodiments of the present discovery emerge from the following description of the exemplary embodiments shown in diagrammatic form in the drawings. The drawings show the following:
In one aspect of the discovery, pressure intensifiers are used which have a directional control valve for oscillating an intensifier piston. The piston includes a valve spool, and is preferably in the form of a differential piston. The hydraulic fluid from the supply system can be applied at one end of the piston, and preferably as a function of the control position of the valves in the control bank.
It is particularly advantageous if there is a pressure reducing valve and/or choke upstream of the pressure intensifier in each shield support, so that a constant level of high pressure may be achieved, irrespective of pressure fluctuations in the supply system and despite the unchangeable, proportional intensification of pressure. In an exemplary embodiment, the pressure intensifier on the hydraulic shield support is located in the pipe system between the control bank and the hydraulic props. As is known for a shield support, the control bank for each hydraulic prop may have a dedicated actuation valve connected to the allocated pressure chamber in the hydraulic prop by a separate branch pipe (setting pressure pipe) for supplying hydraulic fluid at setting pressure. In order to obtain a rapid accumulation of pressure in the hydraulic props to set the shield support, it is particularly favorable if both the actuation valves for the hydraulic props supporting the roof shield are actuated by a single, common pilot valve. In particular, the hydraulic props are designed as double acting and/or cylinders which telescope in multiple stages, to either end of which hydraulic fluid may be applied. It is also preferable for a common, particularly pilot-controlled actuation valve to be located in the control bank for removal of both the hydraulic props. A hydraulically releasable non-return valve, which can be released hydraulically by the pressure of the hydraulic fluid, may be located in the branch pipe of the setting pressure pipe for each hydraulic prop, for removing the hydraulic props.
In the exemplary embodiment of a shield support, a pressure intensifier dedicated to each hydraulic prop is located in the branch (setting pressure) pipe of the hydraulic prop. With a corresponding shield support, the outlay for additional pipes to be laid in the shield support is extremely low and the pressure intensifier may be located immediately at the inlet of the pressure chamber of the hydraulic prop, thus obviating the need for any hoses for hydraulic fluid at an increased level of high pressure. It is then particularly favorable to connect the low-pressure inlet of the pressure intensifier upstream of the non-return valve and the high-pressure outlet of the pressure intensifier downstream of the non-return valve to the appropriate branch pipes of the setting pressure pipes.
Alternatively, the entire shield support may have only one pressure intensifier, allocated to both hydraulic props. In one embodiment, the low-pressure inlet of the pressure intensifier on the branch (setting pressure) pipe of one of the two hydraulic props may be connected to the hydraulic prop upstream of the relevant non-return valve. Alternatively, the low-pressure inlet of the pressure intensifier may be connected directly, i.e. without an intermediate actuation valve, to the hydraulic fluid supply system at the low or outlet pressure, through a hydraulically releasable non-return valve. In order to nevertheless guarantee an application of pressure to the pressure chambers of both hydraulic props with hydraulic fluid at the intensified high-pressure level in both alternative embodiments, it is practical to connect the high-pressure outlet of the pressure intensifier to both branch (setting pressure) pipes, in both cases downstream of the releasable non-return valve provided for the relevant hydraulic prop. It is then recommended that a non-releasable non-return valve be located between the high-pressure outlet and the connecting points on both branch pipes.
In an embodiment in which the low-pressure inlet of the pressure intensifier is connected directly to the hydraulic supply system, the upstream releasable non-return valve can either be releasable by any setting pressure intensified by the pressure intensifier or an additional actuation valve may be located or provided in the control bank, by the operation of which the hydraulically-releasable non-return valve may be released. Hydraulic fluid at a pressure of 200 bar or 300 bar may be provided throughout the entire face. Alternatively, the supply system for each shield support or a group of shield supports may have a pump which brings the necessary pressure to the first level for initial setting of the hydraulic props and which is then increased to the high-pressure level by the pressure intensifier. Moreover, the high-pressure outlet of the pressure intensifier could also be connected to the pressure chamber of adjusting cylinders for a front cantilever.
The shield support 1 is actuated from an electronic control unit 11 mounted on the shield 5, by means of which directional control valves in control bank 40 can be actuated to control operation of the shield support 1. The control bank can include a collection of selectively positionable control valves, each of which can be positioned to one or more control positions. A valve chest 14 is mounted on each hydraulic prop 8 and contains a non-return valve for the alternative application of pressure to the pressure chamber or annulus, to which hydraulic fluid for applying pressure in the pressure chamber to the hydraulic prop 8 may be fed through the pressure pipe (setting pressure pipe) 13 and to which hydraulic fluid may be fed to apply pressure to the annulus through another hydraulic pipe (removal pressure pipe) 15. The hydraulic fluid is supplied by a hydraulic fluid supply (not shown). As at least two hydraulic props 8 are provided, at least one other hydraulic pipe (setting pressure pipe) not shown leads to the hydraulic prop concealed in
At a deep mine face, the face area is supported by numerous hydraulic shield supports 1 located alongside each other and between each shield support 1 and the working face not shown in greater detail is a winning system, also not shown, such as e.g. a coal plough or drum cutter-loader with a chain dragline scraper. The winning system can be advanced towards the working face by the advancing ram 16. An angle cylinder 9 is interposed between the back shield 6 and the shield 5, to push or pull the principal or roof shield 5 against the roof or floor, either in parallel or at an angle to the roof or floor, as is generally known to a person skilled in the art. The supply of pressure to all the hydraulic shield supports 1 at the face, and thus the supply of hydraulic fluid to the control bank 40, takes place through a hydraulic supply system not shown here in greater detail, in which a pump may be provided for one or more shield supports 1, to provide the pressure chamber of the hydraulic props 8 with two different setting pressures during the setting process or in their set state, whereby working at an initial setting pressure (pressure of approximately 300 bar) and a second setting pressure (pressure of approximately 400 bar) is known in the state of the art.
At least one pressure intensifier is provided in the hydraulic pipe system for each shield support 1, which has an oscillating intensifier piston in the form of a differential piston which intensifies pressure. An inventive pressure enhancer is shown in diagrammatic form in
The hydraulic high-pressure intensifier with the overall number 20 in
In the exemplary embodiment in accordance with
Hydraulic fluid at the intensified pressure H can thus be supplied to the feed pipes 152A, 152B to pressure chamber 18 of the hydraulic props 8 through the central pressure intensifier 120 for both hydraulic props 8.
In the embodiment in accordance with
In the exemplary embodiment in
Modifications and variations on the above described embodiments will be apparent to a person skilled in the art and still within the scope of the present discovery which is defined by the appended claims. Both the branch pipes and the setting pressure pipes also could be actuated separately by means of separate pilot control valves. The fluid under high pressure available at the high-pressure outlet of the pressure intensifier could also be used to operate other cylinders, such as adjusting cylinders for front cantilevers or similar. The present discovery includes combining features and aspects of the various exemplary embodiments described herein.
The foregoing description is, at present, considered to be the preferred embodiments of the present discovery. However, it is contemplated that various changes and modifications apparent to those skilled in the art, may be made without departing from the present discovery. Therefore, the foregoing description is intended to cover all such changes and modifications encompassed within the spirit and scope of the present discovery, including all equivalent aspects.
Number | Date | Country | Kind |
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103 28 286 | Jun 2003 | DE | national |
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Number | Date | Country | |
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20040258487 A1 | Dec 2004 | US |