GB2329429A

GB2329429A - Improvements in and relating to roof supports

Info

Publication number: GB2329429A
Application number: GB9719968A
Authority: GB
Inventors: Peter Elliot-Moore
Original assignee: JOY MINING MACHINERY Ltd
Current assignee: JOY MINING MACHINERY Ltd
Priority date: 1997-09-20
Filing date: 1997-09-20
Publication date: 1999-03-24
Also published as: ZA988351B; GB9719968D0; DE19842460A1; AU8608698A

Abstract

The present invention provides a roof support arrangement (100) having a roof support leg (128), means for hydraulically extending the leg (128), a valve (126) connected to a hydraulic fluid supply for controlling the flow of hydraulic fluid into the roof support leg (128), actuator means (122) for opening and closing the valve (126) according to a control signal, means for determining the pressure (134) on the leg and for transmitting a signal dependent on the pressure to a control means (120), which control means (120) generates a control signal according to the pressure determined by the pressure determining means (134), which control signal actuates the actuator means (122) to open a valve (126).

Description

2329429 - 1 IMPROVEMENTS IN AND RELATING TO ROOF SUPPORTS

Field of the Invention

The present invention relates to roof support arrangements, to the control thereof and, in particular, to support legs used as part of hydraulic mine roof supports and to methods of controlling the same.

Background to the Invention

Hydraulic mine roof supports are well known and generally comprise a ground engaging base, a roof engaging canopy and a plurality of support legs each comprising a hydraulic jack acting between the base and the canopy. Each leg is controlled by a control unit coupled to a hydraulic system.

In a known leg control arrangement as shown in Figure 1 of the accompanying drawings, a control unit 2 is connected to a first solenoid 4 and a second solenoid 6. The first solenoid 4 actuates a first hydraulic spool valve 8 to fill a head side 9 of leg 10 with hydraulic f luid through a Pilot Operated Check Valve (POCV) 12. The second solenoid 6 actuates a second hydraulic spool valve 14 to fill an annulus 15 of the leg 10 of hydraulic fluid through a valve (not shown) to lower the leg. The spool valves 8, 14 are connected to a pressurised source of hydraulic fluid (not shown). The actuation of second hydraulic spool valve 14 also opens POCV (via line 13) 12 so that as the annulus 15 is filled with hydraulic fluid, corresponding hydraulic fluid drains from head side 9.

These are power-up and power-down operations respectively.

2 A pressure transducer 16 provides a pressure signal from the head side 9 to control unit 2. The control unit 2 is conf igured so that upon receipt of a command signal it activates first solenoid 4 to actuate first hydraulic spool valve 8 to fill head side 9 to extend leg 10. When the signal from the pressure transducer 16 reaches a predetermined level, the control unit 2 deactivates the first solenoid 4 thus closing first hydraulic valve 8 after a further predetermined time period, thus stopping the movement of leg 10. The predetermined time period can be varied to alter the final set pressure of the leg, but it is an imprecise means for doing so. The control unit 2 then transmits a signal to the next unit in sequence for it to begin its operation.

is To accommodate pressure surges on the leg 10 in use, a yield valve 18 is provided on the leg 10. The yield valve 18 comprises a mechanically biased non-return valve which remains closed under normal operating conditions, but which is forced open during abnormally high pressure loads to vent hydraulic fluid. The yield valve 18 thus protects the leg 10 from damage during pressure surges.

The arrangement further comprises a guarantee set valve 20 which ensures that the settling pressure in the leg reaches the maximum supply level at the face.

In such an arrangement it is impossible reliably to achieve 100% set to yield ratios as there is no feed back from the yield mechanism. The yield valves and guarantee set valves are an additional cost and complexity when manufacturing a support leg. If the yield mechanism fails to operate at set pressure, it could lead to structural damage (yield high) or loss of roof control (yield low). Furthermore, since the face setting and yield pressures are determined at the factory, there is no real control of these variables by users.

It is aim of preferred embodiments of the present invention to obviate or overcome at least one disadvantage of the prior art whether referred to herein or otherwise.

Summary of the Invention

According to the present invention in a first aspect, there is provided a roof support arrangement comprising a roof support leg, means for hydraulically extending the leg, a valve connected to a hydraulic fluid supply for controlling the flow of hydraulic fluid into the roof support leg, actuator means for opening and for closing the valve according to a control signal, means for determining the pressure on the leg and for transmitting a signal dependent on the pressure to a control means, which control means generates a control signal according to the pressure determined by the pressure determining means, which control signal actuates the actuator means to open a valve.

A roof support arrangement according to the f irst aspect of the invention dispenses with the need for the known yield valves, making the roof support arrangement mechanically less complex, simpler to produce and cheaper.

Suitably, the control means comprises comparator means to determine whether the pressure signal from the pressure determining means indicates a pressure on the leg exceeding a predetermined valve in which case the valve is opened.

Suitably, the valve opened permits hydraulic fluid to flow from the leg, whereby the leg is lowered.

Suitably, the pressure determining means comprises a 5 transducer which emits an electrical signal.

Suitably, the pressure determining means is calibrated to give substantially an absolute pressure determination. By being able to measure the actual pressure on the leg, set to yield ratios can be established more reliably and closer than previously if possible.

Suitably, the arrangement further comprises a user interface whereby the control means can be configured to open the valve at different pressures. Thus more accurate control of both the set and yield pressures can be obtained.

In a second aspect of the present invention, there is provided a method of controlling a roof support leg, which method comprises measuring the pressure on the leg thereby to generate a pressure signal and using the pressure signal to reduce resistance of the leg to further pressure if the pressure signal exceeds a predetermined value.

Suitably, the resistance of the leg to further pressure is reduced by releasing hydraulic fluid in the leg.

Suitably, the resistance of the leg to further pressure is reduced by adding hydraulic fluid to the leg to force it away from the direction of increased pressure.

- Suitably, a valve is provided through which hydraulic fluid is allowed into the leg to raise the leg and through which hydraulic fluid is drained from the leg to lower the leg, which valve is used during controlled and yield lowering.

Brief Description of the Drawin-qs

The present invention will now be described, by way of example only, with reference to the drawings that follow; in which:

Figure 1 is a schematic functional diagram of a known roof support leg arrangement.

Figure 2 is a front elevation of a roof support leg for use with the present invention.

Figure 3 is a schematic functional diagram showing connections between different parts of a roof support leg arrangement according to the present invention.

Description of the Preferred Embodiment

Referring to Figure 2 of the drawings that follow, there is shown a mine roof support 100 having a ground engaging base 102 and roof engaging canopy 104, interconnected by a rear shield 106 and pivoting links 108. A pair of hydraulic support legs 110 act between the base 102 and the canopy 104. The angle between the canopy 104 and the shield 106 is controlled by a compensating ram 112 which can be hydraulically locked. Each leg includes a yield valve 114.

Referring to Figure 3 of the drawings that follow, there is shown a schematic diagram of a leg control arrangement according to the present invention. In the diagram, a high speed input/output controller 120 is electrically connected to a first solenoid 122 and a second solenoid 124. The first solenoid 122 actuates a first hydraulic spool valve 126 (other valves can be used) to fill a head side (or raise annulus) 127 of a roof support leg 128 through a POCV 130. The second solenoid 124 actuates a second hydraulic spool valve 132 to fill a lowering annulus 133 of leg 128 and to empty the leg 128 of hydraulic fluid through POCV 130 which is opened via line 131 by the actuation of second hydraulic spool valve 132. A pressure transducer 134 transmits to high speed I/0 controller 120 an electrical signal dependent on the hydraulic fluid pressure on leg 128 which it measures at the hydraulic fluid input port (not shown) between POCV 130 and head side 127.

operation of the arrangement shown in Figure 3 will now be described.

A leg raise signal is input to the controller 120 from a previous leg having finished its lower/raise operation or manually by an operator. Upon receipt of the raise signal, the controller 120 instructs first solenoid 122 to actuate first hydraulic spool valve 126, allowing hydraulic fluid to flow into head side 127 of leg 128.

During the lift operation, controller 120 constantly monitors the signal output from pressure transducer 134.

The controller 120 and pressure transducer 134 may be calibrated so that the controller determines an absolute pressure, but in any event when the signal from the pressure transducer 134 reaches a predetermined value against which controller 120 continuously runs a comparator operation, a signal is sent to solenoid valve 122 to deactivate first hydraulic spool valve 126 thus closing off the flow of fluid through POCV 130 to leg 128. The pressure at which the flow of hydraulic fluid into the head side 127 is cut off can be determined to be substantially equal to the yield pressure, or just slightly lower.

If it is desired to power lower the leg 128, controller 120 signals second solenoid 124 to actuate second hydraulic spool valve 132 permitting the flow of hydraulic fluid into lowering annulus 133 of leg 128. The hydraulic pressure also opens the POCV 130 to a return line so that hydraulic fluid can flow out from head side 127.

If the leg 128 is subject to a pressure surge, for instance as a result of a shift in the roof geology, this is determined by the pressure transducer 134. The pressure signal from pressure transducer 134 therefore will exceed the predetermined value and the high speed I/0 controller 120 immediately transmits a signal to second solenoid 124 to open second hydraulic spool valve 132 both to power down the leg 128 and open the return line on POCV 130 so that, in addition to the power down of leg 128, additional pressure on the leg 128 can simply drive hydraulic fluid from head side 127 out through POCV 130.

The option is normally provided by some extra control valves (not shown) to switch the power to the leg retract annulus OFF during support advance. When the pressure measured by controller 120 and pressure transducer 134 is equal to or less than the set pressure, solenoid 124 deactivates second hydraulic spool valve 132 stopping the power down of leg 128 (if activated) and release of fluid from head side 127. If the pressure is lower than the set - 8 pressure, the first solenoid 122 is signalled to actuate first hydraulic spool valve 126 to permit the flow of hydraulic fluid through POCV 130 into head side 127 of leg 128. Thus, the system described dispenses with the need for normal yield valves and can automatically react to face geology.

If for any reason the pressure on leg 128 decreases, for instance due to a change in roof geology or leakage, the pressure reduction is determined by the pressure transducer 134 and the controller 120 reacts by signalling first solenoid 122 to open first hydraulic spool valve 126 to further fill the head side 127 until the desired pressure is reached once more.

is The high speed I/0 controller 120 can easily include manual and/or electronic means for altering the set and/or yield pressure (s) enabling face setting and yield profiles to be set by users dependent upon local conditions.

Additionally, the guarantee set valve arrangement can be dispensed with because whenever the leg pressure reduces to below the set pressure, the system can determine if the legs should be pressurised to achieve 25 setting pressure, dependent on the status of the support.

By suitable calibration of the pressure transducer 134, face convergence can be measured based on the pressure change.

Such a system provides active roof control of roof support legs for mines.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A roof support arrangement comprising a roof support leg, means for hydraulically extending the leg, a valve connected to a hydraulic fluid supply for controlling the flow of hydraulic fluid into the roof support leg, actuator means for opening and for closing the valve according to a control signal, means for determining the pressure on the leg and for transmitting a signal dependent on the pressure to a control means, which control means generates a control signal according to the pressure determined by the pressure determining means, which control signal actuates the actuator means to open a valve.

2. A roof support arrangement as claimed in Claim 1, in which the control i means compnses comparator means to determine whether the pressure signal 15 from the pressure determining means indicates a pressure on the leg exceeding a predetermined valve in which case the value is opened.

3. A roof support arrangement as claimed in Claim 1 or Claim 2, in which the valve opened permits hydraulic fluid to flow from the leg, whereby the leg is lowered.

4. A roof support arrangement as claimed in any one of the preceding claims, in which the pressure determining means comprises a transducer which emits an electrical signal.

5. A roof support arrangement as claimed in any one of the preceding claims, in which the pressure determining means is calibrated to give substantially an absolute pressure determination.

6. A roof support arrangement as claimed in any one of the preceding claims, further comprising a user interface whereby the control means can be configured to open the valve at different pressures.

7. A method of controlling a roof support leg, which method comprises measuring the pressure on the leg thereby to generate a pressure signal and using the pressure signal to reduce resistance of the leg to further pressure if the pressure signal exceeds a predetermined value.

8. A method as claimed in Claim 7, in which the resistance of the leg to further pressure is reduced by releasing hydraulic fluid in the leg.

9. A method as claimed in Claim 7, in which the resistance of the leg to further pressure is reduced by adding hydraulic fluid to the leg to force it 15 away from the direction of increased pressure.

10. A method as claimed in Claim 7, in which a valve is provided through which hydraulic fluid is allowed into the leg to raise the leg and through which hydraulic fluid is drained from the leg to lower the leg, which valve is used during controlled and yield lowering.

11. A roof support arrangement, constructed and arranged substantially as herein described, with reference to Figure 2 and 3 of the accompanying drawings.

12. A method of controlling a roof support leg, substantially as herein described, with reference to Figures 2 and 3 of the accompanying drawings.