GB2095425A

GB2095425A - Mine roof support control systems

Info

Publication number: GB2095425A
Application number: GB8137232A
Authority: GB
Original assignee: Dobson Park Industries Ltd
Current assignee: Joy Global Industries Ltd
Priority date: 1981-02-25
Filing date: 1981-12-10
Publication date: 1982-09-29
Also published as: DE3200523A1; FR2500527A1; GB2095425B; DE3200523C2; FR2500527B1

Abstract

Apparatus for controlling operation of a self-advancing pressure-fluid operated mine-roof support has a plurality of pressure-fluid valves 12 each for effecting a different support function. The valves 12 have displaceable valve parts 30, 36 selected for operation according to the position of a selector member 46 movable to effect or allow displacement of a desired valve part 30, 36 by an actuator 54. The selector member 46 is shown as a plunger on an arm 45 driven by a motor 40 also driving a coded disc 44. Position signals from the coded disc are compared with demand signals from a remote location to cause operation of the desired valve 12. Manual control of the selector member 46 and arm 45 is provided by a dead mans handle 81. <IMAGE>

Description

SPECIFICATION Mine roof support control systems This invention relates to self-advancing mine roof support control systems and is especially applicable to such systems enabling the advance of a roof support to be controlled from a remote location.

In longwall mining systems, the mine roof supports are advanced by operating the hydraulic rams and props according to a particular sequence. A typical sequence comprises the functions ram push, rear legs lower and/or front legs lower, ram pull, rear legs raise and/or front legs raise.

Systems are known in which the hydraulic valves which control application of pressure-fluid to the rams and props, to achieve the required functions, are remote from the roof support being operated.

This enables the operator to remain at a position of relative safety, for example under the roof engaging member of an adjacent mine roof support. A drawback of such systems is the need for a set of hoses, one for each function, to extend between the support being operated and the control position, for example an adjacent roof support.

To overcome this drawback it has been proposed (British Patent No. 1,531,246) to locate the hydraulic control valves on the roof support and control their operation by coded electrical signals transmitted from the position remote from the support. The multiplicity of hydraulic interconnections is thus avoided, particularly since the electrical signals can be conveyed to the support along a single cable.

More specifically, the previously proposed system employed a hydraulic motor, or a hydraulic rotary positional servo-mechanism, driving a multi-way hydraulic valve to distribute hydraulic fluid from a supply line to any one, or combination, of several outputs. It has been found, however, that such an arrangement is not entiely satisfactory due to the relatively high force required to operate the multiway valve in view of the high pressure of the fluid acting on the movable selector parts of the valve.

An object of the present invention is to overcome this problem.

According to one aspect of this invention there is provided apparatus for selecting the operation of a pressure-fluid operated mine-roof support from a remote location comprising at that support a plurality fluid flow ports each associated with control means displaceable to control flow of pressure fluid through an associated line to effect operation of a different function or functions of the support, an actuator for the control means, a selector movable between positions whereat it selectively enables and disables displacement of the control means by the actuator, and selection means controlling the selector in accordance with demand signals from the remote location specifying a desired position of the selector member wherein it enables displacement by the actuator of the control means corresponding to the desired position.

According to another aspect of the present invention a control system for controlling operation of a self-advancing mine roof support from a remote location comprises a plurality of fluid flow valves, each including a valve means displaceable by an actuator to control flow of pressure fluid through an associated outlet to effect a particular function of the support, and selection means responsive to signals from the remote location representing a required function to move a selector member to a position in which it enables displacement of the corresponding valve means by the actuator.

In preferred embodiments the selection means comprises a positional servo-mechanism, including a motor, and the actuator at least one hydraulic ram.

The selector may then comprise a plunger which is moved by the motor into position between the selected valve means and the hydraulic ram, the stroke of the ram being insufficient to displace the valve means and operate the valve unless the plunger is interposed.

When a valve is to be selected the appropriate coded signal, preferably in digital form, is sent to the selection means from a transmitter located at a remote position, for example at an adjacent roof support or a control unit at the end of the face. The instant slector position is compared with that required for operation of the selected valve. If they are different, the motor is energised and moves the selector until the two positions correspond. The valve can then be opened by operation of the actuator hydraulic ram.

Advantageously the valves are arranged in a circle and the plunger is carried by an arm on the output shaft of the motor. The actuator may the comprise a circular of annular hydraulic ram, coaxial with the valve circle and motor.

Alternatively the selector may comprise a plate interposed between the valves and a corresponding set of hydraulic rams, at least one opening being provided in the plate. Selection of the required valve is by moving the plate until the opening is in line with the corresponding one of the hydraulic rams to allow the ram to extend therethroug h to displace the valve means of the selected valve.

Conveniently, a series of hydraulic rams may be arranged in a circle, each aligned with one of the valves pistons, and the selector may then comprise a circular or annular plate carried by the motor output shaft.

Where the valves are arranged in a circle the selection means may comprise a rotations servomechanism, conveniently including a coded disc.

Manual operation of the selector may be provided for say way of a "dead man's handle" which can be used to turn the selector to select for operation a chosen valve.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sectional side view of a valve part of the control system Figure 2 is a front view of the apparatus of Figure 1; and Figure 3 illustrates, schematically, part of the control system Referring to the drawings, a valve part 10, to be located at the roof support to be operated, has six fluid flow valves 12 arranged radially in a cylindrical annular valve block 14. Each valve 12 comprises a chamber 16 connected to a hydraulic fluid reservoir (not shown) by common feed and return lines connected to ports, 18 and 20, respectively, and by a service or outlet port 22 to a particular hydraulic ram or prop the function of which is to be controlled.

Each valve chamber 16 houses displaceable valve means in the form of a valve piston 24 urged by a spring 26 onto a seating 28 to close the feed port 18 and leave the return port 20 open to allow fluid to return from the ram or prop via the service port 22. A push rod 30, connected at one end to the valve piston 24, is slidably located in a hole 32 in the body 14 and sealed circumferentially thereto by a seal 34.

The other end of the push rod 30 projects beneath the lower surface of the valve block 16 and can be acted upon to displace the valve piston 24 from seating 28, to open the feed port 18, and onto the seating 36 to close the return port 20.

The cylindrical body 14 contains a small intrinsically safe electric motor 40 having an output shaft 42, its axis of rotation coaxial with the body 14. At its upper end (as shown) the output shaft 42 carries an angular position transducer, comprises a coded disc 44 and a reading head 46. The transducer is connected to a transmitter (not shown) at a remote position from the roof support carrying the control valve apparatus 10.

On the output shaft 42, emerging from the lower side of the motor, is fixed a radial arm 45 carrying a plunger 46 at the radially-outer end thereof, so that rotation of the output shaft 42 can position the plunger with its axis in alignment with any of the valve push rods 30.

The plunger 46 extends slidablythrough a hole in the arm 45 and is retained in the arm 45 by stops 48 and 50, one each side of the arm. A spring 52 acts between the arm 45 and top 50 to urge the plunger 46 away from the valve push rod 30, leaving a small clearance.

An annular hydraulic ram 54, comprising a piston 55 is a cylinder block 56, is supplied with hydraulic fluid via a solenoid-operated pilot-valve 57 which controls admission of fluid to the cylinder block via a port 58. The ram is positioned so that its piston 55 can act on the plunger46, whichever valve push rod 30 it is aligned with, and cause it to displace the associated valve piston 24.

A return spring (not shown) restores the ram 54 to its inoperative position when the fluid is released by the pilot valve.

A simplified schematic diagram of the relevant parts of the control system is illustrated in Figure 3.

The parts to the right of the vertical broken line 59 are located atthe roof support being controlled and comprise the control valve part 10 and a comparator device 60, which has one input 62 connected to the output 64 of the disc reader 46 and another input 66 connected to the remote transmitter 68 by way of an electrical cable 70. One output 72 of the comparator device 60 is connected to the selector drive motor 40 and another output 74 is connected to the pilot valve 57 which operates the plunger 54 by supplying hydraulic fluid along a fluid line 76.

In operation, a signal representing the required function to be effected is generated at the transmitter 68. This may be done manually by an operator moving a selector switch, orby an automatic face control system. Examples of the various functions required are illustrated in Figure 2. Conveniently the signal is the number, in digital form, of the position in the valve block of the valve which controls that particular function.

This signal, and that from the coded disc 44 are compared by the comparator device 60. If the plunger is not already aligned with the valve selected, the device 60 causes the motor to be energised and turn the plunger until it is opposite the required valve, whereupon the correct signal from the coded disc will be received. The motor is then switched off and the pilot valve 57 enabled to be energised. Actual operation of the valve 57 may be by closing a remote push-button 78 manually, or effected automatically. When energised the valve 57 admits hydraulic fluid to the annular ram 54 which then urges the plunger 46 against the valve pushrod 30, opening the valve 12, and supplying fluid to service port 22 to operate the ram or prop connected to it.

Thereafter, the pilot valve is de-energised, the ram 54 returns, and the valve piston 24 returns to its seating 28.

During manual operation the operator will operate the transmitter switch to initiate the required function, watch the support as the function is carried out, and, when it has been completed, terminate the signal by switching to another function orto neutral.

For automatic operation, the selector switch at the transmitter will be switched by the operator to an "auto" position.

In response, the valve part 10, at the roof support, will position the plunger 46 beneath the corresponding "auto" valve 12. Subsequent operation of the solenoid valve 57 and actuator ram 54 to supply fluid through "auto" value 12 will initiate the sequence of functions to advance the support. The sequence will continue and terminate, without further adjustment of the valve part 10, relying instead upon the operation of hydraulic switches and valves associated with the components themselves - i.e. the props and rams.

On normal automatic operation the valve will not usually have moved from the "automatic" position so the selection and operation will be virtually instantaneous and there will be no more delaybetween the "operate" command from the transmitter and its execution than there is in present systems employing several valves, each connected directly to the "transmitter". If the selector is not in the required position, either because a different function is required or the selector has been left in a different position after manual remote operation, there will be a delay before the command is executed. This may be less than one second using either a low inertia dc motor or a stepper motor.

The control unit may be operated manually at the support itself, by means of a "dead man's" handle 81 connected to the end of the shaft 42 via a dog clutch 83 in the opening in the annular ram 54. The positions of the valves 12 are indicated suitably at 80 on the lowermost face 82 of the ram cylinder block 56 to assist manual operation.

When manual operation is required the handle is pushed in and turned until the dog clutch engages.

At this point the position of the handle automatically corresponds to the position of the plunger as indicated on the faceplate. The plunger arm can then be turned manually to the desired position and the selected valve opened by operation of the pilot valve, conveniently by means of a local push-button.

Various modifications are possible within the scope of the invention. For example, instead of an arm and plunger, the selector could comprise a plate, and a set of hydraulic rams, one for each valve, could be provided instead of the annular ram 54, all being powered simultaneously by the pilot valve. A hole in the plate could then be positioned adjacent the selected valve to allow its associated ram to pass through the plate to operate the valve. The remaining rams would merely bear against the underside of the plate.

It is also envisaged that the valves might be arranged linearly and the selector plunger or plate move along the line of valves, perhaps by a linear motor.

An advantage of embodiments of the invention is that the selector, being separate from the actuator and the valve means, can be moved using very little force, for example buy a small motor of the type usually employed with an angular position transducer. Because of the high fluid pressures involved, very high forces are required to move the valve pistons and a large servo motor would be required if the actuator and valve means were directly coupled.

It will be appreciated that only one communication channel may be needed between the roof supportmounted control valve part and the remote transmitter, since the control signal can be in digital form.

However, a multi-core electrical cable could be employed, if digital signals are not preferred.

Claims

1. Apparatus for selecting the operation of a pressure-fluid operated mine-roof support from a remote location comprising at that support a plurality fluid flow ports each associated with control means displaceable to control flow of pressure fluid through an associated line to effect operation of a different function or functions of the support, an actuator for the control means, a selector movable between positions whereat it selectively enables an disables displacement of the control means by the actuator, and selection means controlling the selector in accordance with demand signals from the remote location specifying a desired position of the selector member wherein it enables displacement by the actuator of the control means corresponding to the desired position.

2. Apparatus for controlling operation of a selfadvancing pressure-fluid-operated mine-roof support from a remote location, comprising at that support a plurality of fluid4low valves each including a valve means displaceable to control flow of pressure-fluid through an associated outlet to effect a particular different function of the support, actuator forthe valve means of said valves, a selector member movable between positions whereat it selectively enables and disables displacement of the valve means by the actuator, and selection means responsive to demand signals from the remote location specifying a desired function of the support to move the selector member to a position in which it enables displacement by the actuator of the valve member corresponding to the desired function.

3. Apparatus according to claim 2, wherein the selection means comprises a positional servomechanism for controlling the position of the selector member.

4. Apparatus according to claim 3, wherein the positional servo-mechanism comprises a motor for moving the selector member, and means for controlling motor operation according to comparions of the demand signals and selector position signals representing the actual position of the selector member.

5. Apparatus according to claim 4, wherein the remote location includes means for providing demand signals in the same coded format as selector position signals from a transducer associated with the positional servo-mechanism.

6. Apparatus according to any preceding claim, wherein the actuator comprises at least one ram and the selector member comprises an interposer part slectively positionable relative to a movable-ram part and the displaceable valve means.

7. Apparatus according to claim 6, wherein the interposer part serve selectively to allow passage of said movable ram part to operate the desired displaceable valve means.

8. Apparatus according to claim 7, wherein the interposer part comprises a movable plate having an opening capable of registering between any desired said valve means and corresponding movable ram parts, one for each said valve means.

9. Apparatus according to claim 6, wherein the interposer part serves selectively as an intermediate coupling between the movable ram part and the desired displacement valve means.

10. Apparatus according to claim 9, wherein the interposer part comprises a plunger positionable by the selection means between the desired displaceable valve means and the actuator, the stroke of the ram being insufficient to displace any of the valve means to operate the associated valve unless the plunger is interposed.

11. Apparatus according to claim 2 or any subse quentclaim appendent thereto, wherein the displaceable valve means are disposed spaced about a circle and the selector member is movable around that circle.

12. Apparatus according to claim 11 with claim 4, wherein the motor is of rotary type having an output shaft carrying the slector member.

13. Apparatus according to claim 12, wherein the motor output shaft further drives a coded disc for generating said selector position signals.

14. Apparatus according to claim 11, 12 or 13, comprising a dead-mans handle for operating the selector manually.

15. Apparatus according to claim 2 orto any subsequent claim as appendentthereto, wherein one of said valves serves to effect an automatic self-advancing operation of an associated said support.

16. Apparatus for controlling operation of a self-advancing pressure-fluid-operated mine-roof support from a remote location, substantially as herein described with reference to the accompanying drawings.