GB2235234A

GB2235234A - Mine roof supports

Info

Publication number: GB2235234A
Application number: GB8928149A
Authority: GB
Inventors: Robert Graham Harris
Original assignee: MECO ELECTRONICS Ltd
Current assignee: MECO ELECTRONICS Ltd
Priority date: 1989-12-13
Filing date: 1989-12-13
Publication date: 1991-02-27
Anticipated expiration: 2009-12-13
Also published as: GB8928149D0; GB2235234B

Abstract

A mine roof support comprises a canopy, a shield section pivotally connected to the canopy at or adjacent to the rear end thereof, a base section, a link arrangement pivotally interconnecting the base section and the shield section, front hydraulic prop means (14) connected between the base section and the canopy, and rear hydraulic prop means (15) connected between the base section and one of the canopy and the shield section. The mine roof support also comprises means for detecting the attitude of the canopy, e.g. one or more tilt switches (28, 29) and means responsive to the attitude detecting means, e.g. one or more solenoid operated valves (26, 27) for controlling the operation of at least one of the front and rear hydraulic prop means. <IMAGE>

Description

MINE ROOF SUPPORTS This invention relates to a mine roof support.

Known mine roof supports include a canopy, a shield section pivotally connected to the canopy at or adjacent to that end of the canopy which is, in use, remote from the mine face (hereinafter referred to as the rear end of the canopy), a base section, a link arrangement pivotally interconnecting the base section and the shield section,, and hydraulic props between the base section and the canopy/shield section for raising and lowering the canopy relative to the base section and for setting the canopy against a mine roof. Typically, these known roof supports have four hydraulic props, two of which (hereinafter referred to as the rear props) act between the base section and either the rear end of the canopy or the shield section, and the other two of which (hereinafter referred to as the front props) act between the base section and a part of the canopy intermediate its ends.

These known mine roof supports also include an advancing mechanism, which generally comprises a relay bar arrangement and an advancing ram, for advancing the roof support towards the mine face. As a mine roof support is advanced towards the mine face, the mine roof falls away behind the canopy. There will therefore be a break line between sound and unsound sections of the roof, and ideally, this break line is at or close to the rear end of the canopy.

It is important to maintain contact between the front end of the canopy and the mine roof in order to adequately support the area of the roof between the canopy and the mine face. If the break line between sound and unsound sections of the mine roof progresses too far forwards beyond the rear edge of the canopy, the rear props will act on the canopy behind the break line.

In this event, if all four props are used to set the roof support, the front end of the canopy could tip downwards with the result that the front end of the canopy will move away from the roof.

In circumstances when this is likely to take place, it is known for roof support operators to intervene and set the front props only. To do this the operator must get into the roof support at a time when the roof above is unsupported. This can be dangerous.

According to the present invention there is provided a mine roof support comprising a canopy having front and rear ends, a shield section pivotally connected to the canopy at or adjacent to the rear end thereof, a base section, a link arrangement pivotally interconnecting the base section and the shield section, first hydraulic prop means connected between the base section and the canopy, and second hydraulic prop means connected between the base section and one of the canopy and the shield section, the connection(s) between the first hydraulic prop means and the canopy being closer to the front end of the canopy than the connection(s) between the second hydraulic prop means and the canopy or the shield section, means for detecting the attitude of the canopy and means responsive to the attitude detecting means for controlling the operation of at least one of the first and second prop means.

Preferably, the attitude detecting responsive means controls the operation of the first and second prop means so that the attitude of the canopy is such that a pre-selected end of the canopy is always initially set against the mine roof.

This may be achieved by selectively operating (a) only the one of the first and second prop means closer to the pre-selected end of the canopy and (b) the other prop means and/or (c) both the first and second prop means according to the detected attitude.

Advantageously, the attitude detecting responsive means controls the operation of the first and second prop means so that the attitude of the canopy is maintained substantially within a predetermined attitude range during an initial setting operation.

This may be achieved by selectively operating (a) only one of the first and second prop means and (b) the first and second prop means together and (c) only the other of the first and second prop means according to the detected attitude.

The attitude detecting means may be in the form of one or more tilt switches and the attitude detecting responsive means may be in the form of one or more solenoid operated valves.

In an alternative arrangement, means are provided to sense the pressure of the hydraulic fluid in one of the first and second prop means and the attitude detecting means is arranged to operate the other of the first and second prop means or the first and second prop means together when the pressure sensed by the pressure sensing means reaches a predetermined value and the attitude detected by the attitude detecting means is within a predetermined range.

Thus, a preselected end of the canopy can be set initially against the mine roof by operating only the one of the first and second prop means closer to the pre-selected end of the canopy and then, when the pressure in said one prop means reaches said predetermined level, the other of the first and second prop means or the first and second prop means together is/are operated until the canopy attains a desired, e.g.

level, attitude.

In most cases, there will be a requirement to set the front end of the canopy first, but there are circumstances in which it may be required to set the rear end of the canopy first.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a mine roof support, Figure 2 is a schematic view of a control circuit for operating the roof support of Figure 1, Figure 3 is a schematic view used to explain the operation of the roof support in accordance with the control circuit of Figure 2, and Figure 4 is a schematic view of another control circuit for operating the roof support of Figure 1.

Referring firstly to Figure 1 of the drawings, the roof support shown therein comprises a canopy 10, a shield section 11, a lemniscate linkage arrangement 12, a base section 13 comprising two spaced apart pontoons, a pair of front hydraulic props 14, and a pair of rear hydraulic props 15.

The shield section 11 is pivotally connected at one end to the rear end of the canopy, and the lemniscate linkage arrangement 12, which includes four links 16, is pivotally connected at one end to the other end of the shield section, and at the other end to the pontoons making up the base section 13.

The roof support also comprises an advancing mechanism in the space between the two pontoon members, the advancing mechanism comprising a relay bar arrangement 17, and an advancing ram (not shown) connected between the relay bar arrangement 17 and the base section 13.

The rear props 15 are pivotally connected at their lower ends to respective pontoons of the base section 13 and are pivotally connected at their upper ends to the canopy 10 at positions adjacent to the rear end thereof. The front props 14 are also pivotally connected at their lower ends to respective pontoons of the base section 13 and are pivotally connected at their upper ends to the canopy 10 at positions intermediate the ends thereof.

A canopy extension 18, commonly referred to in the art as a tip, is hingedly connected to the front end of the canopy 10 so as so be angularly adjustable relative to the canopy by an hydraulic piston and cylinder unit 19.

The relay bar arrangement 17 is connected to a conveyor 20 which is arranged in juxtaposition to the mine face or seam 21.

As described so far, the mine roof support is entirely conventional and the canopy of this conventional roof support is set against a mine roof 22 by supplying hydraulic fluid under pressure to all four hydraulic props 14 and 15 simultaneously.

As described previously, the mine roof falls away behind the canopy as the canopy is advanced towards the mine face. There is therefore a break line 23 between sound and unsound sections of the roof 22.

Ideally, this break line is at or close to the rear edge of the canopy 10. However, it often progresses forwards of the rear edge of the canopy and can, as shown in Figure 1, progress forwards of a centroid position of the points of action of the four props 14 and 15 on the roof 22. In this event, if all four props are used to set the roof support, the rear end of the canopy can enter space occupied by the unsound roof section with the result that the front end of the canopy tips downwards and moves away from the roof.

In order to lessen the risk of this happening, the roof support shown in the drawings is provided with an attitude control circuit as shown in Figure 2 of the drawings.

The attitude control circuit includes two solenoids 24 and 25 which, when energised, operate valves 26 and 27, respectively, to supply hydraulic fluid under pressure to the front and rear props 14 and 15 respectively. Electric current is supplied to the solenoids 24 and 25 via mercury tilt switches 28 and 29, respectively. The tilt switch 29 is shown in an open condition but this switch closes when the inclination of the canopy falls to a first predetermined angle of inclination to the horizontal, typically +5 , measured from the front to the rear of the roof support and indicated in Figure 3 by line A.The tilt switch 28 is shown in a closed condition but opens when the inclination of the canopy rises to a second predetermined angle of inclination to the horizontal, typically +10e, measured from the front to the rear of the roof support and indicated in Figure 3 by line B.

The attitude control circuit will thus operate to try to keep the canopy 10 at an attitude which is between the first and second predetermined angles of inclination, i.e. between 5" and 10" to the horizontal during initial setting of the canopy with the result that the front end of the canopy extension 18, or, if no extension is provided, the front end of the canopy 10 always sets against the mine roof. If the angle of inclination of the canopy falls to +5, the tilt switch 29 will open to de-energise the solenoid 25 and close off the supply of fluid to the rear props 15.The canopy 10 will then be raised only by the front props 14 and this will have the effect of increasing the inclination of the canopy until it once again exceeds an angle of at least +5". If the angle of inclination of the canopy rises to +lox, the tilt switch 28 will open to de-energise the solenoid 24 and close off the supply of fluid to the front props 14. The canopy 10 will then be raised only by the rear props 15 and this will have the effect of decreasing the inclination of the canopy until it once again falls below an angle of +lOt.

After the front end of the extension 18, or, if no extension is provided, the front end of the canopy 10 has been set against the mine roof, the canopy 10 can be brought to a level attitude by appropriate energisation of the solenoids 24 and 25.

In an alternative embodiment, an inclinometer instrument could be used instead of mercury tilt switches to detect attitude and control the energisation of the solenoids.

Where coal faces are inclined to rise or dip, attitude detector(s) can be positioned on the canopy at such an angle as to compensate for the face attitude.

In the case of analogue sensing using inclinometers, electronic signal conditioning can be applied to provide the necessary compensation.

A further embodiment of an attitude control circuit which may be preferred in some conditions will now be described with reference to Figure 4. In this embodiment, a pressure responsive switch 30 is provided to selectively energise the solenoids 24' and 25'. The solenoid 24', when energised, operates a respective valve 26' to supply hydraulic fluid under pressure to the front props 14 and the solenoid 25', when energised, operates a respective valve 27' to supply hydraulic fluid under pressure to the rear props 15. The solenoid 25' is connected to the switch 30 via a mercury tilt switch 31 which opens when the angle of inclination of the canopy 10 (as hereinbefore defined) falls to a predetermined value, typically 0".

The switch 30 has two fixed contacts 3Oa and 30b and a movable contact 30c which is responsive to the pressure of hydraulic fluid in the front props 14.

When the fluid pressure in the front props 14 is below a preset value, typically 100 bar, the movable contact 30c makes contact with fixed contact 3Oa to connect solenoid 24', as shown in Figure 4, to a supply of electric current and in this case hydraulic fluid will be supplied under pressure to the front props 14. When the fluid pressure in the front props 14 exceeds the preset value, the movable contact 30c will move into contact with fixed contact 30b to connect the solenoid 25' to the supply of electric current as long as tilt switch 31 remains closed and to disconnect solenoid 24' from the supply of electric current. Hence, hydraulic fluid will be supplied under pressure to the rear props 15.Thus, the front props 14 always achieve a minimum acceptable setting pressure determined by the pressure responsive switch 30 before the rear props 15 are brought into play, and hydraulic pressure ceases to be supplied to the rear props 15 if the rear of the canopy 10 tries to move above the front of the canopy as may happen if the mine roof above the rear of the canopy is unsound.

If required, a diode 32 can be connected across the pressure responsive switch 30 as shown in broken lines in Figure 4 to provide simultaneous setting of both the front and rear props 14 and 15 once a minimum pressure has been achieved in the front props 14.

The above mine roof supports are particularly advantageous when used in automatically controlled support systems where the absence of men requires that supports automatically compensate for difficult conditions. Without such automatic compensation such roof conditions could cause the support to set at an angle such that the canopy position could prevent progress of the coal winning machine.

As described above, the front end of the canopy is initially set against the mine roof. There are, however, circumstances in which it is desirable to ensure that the rear end of the canopy is set against the mine roof, and in this case appropriate changes could be made to the control circuits shown in Figures 2 and 4, respectively. This is desirable, for example, where the roof support is situated at the end of an access or "gate" road to the mine face.

The embodiments described above are given by way of example only and various modifications will be apparent to persons skilled in the art without departing from the scope of the invention. For example, the front props 14 or the rear props 15 could be replaced by a single prop. Also, as is sometimes the case, the rear props 15 could be connected between respective pontoons of the base section 13 and the shield section 11 instead of between respective pontoons and the canopy 10.

Claims

1. A mine roof support comprising a canopy having front and . rear ends, a shield section pivotally connected to the canopy at or adjacent to the rear end thereof, a base section, a link arrangement pivotally interconnecting the base section and the shield section, first hydraulic prop means connected between the base section and the canopy, second hydraulic prop means connected between the base section and one of the canopy and the shield section, the connection(s) between the first hydraulic prop means and the canopy being closer to the front end of the canopy than the connection(s) between the second hydraulic prop means and the canopy or the shield section, means for detecting the attitude of the canopy, and means responsive to the attitude detecting means for controlling the operation of at least one of the first and second hydraulic prop means.

2. A mine roof support as claimed in Claim 1, wherein the attitude detecting responsive means is arranged to control the operation of the first and second prop means so that the attitude of the canopy is such that a pre-selected end of the canopy is always initially set against the mine roof.

3. A mine roof support as claimed in Claim 1 or Claim 2, wherein the attitude detecting responsive means is arranged to control the operation of the first and second prop means so that the attitude of the canopy is maintained substantially within a predetermined attitude range during an initial setting operation.

4. A mine roof support as claimed in Claim 1, wherein means are provided to sense the pressure of the hydraulic fluid in one of the first and second prop means and the attitude detecting means is arranged to operate the other of the first and second prop means or the first and second prop means together when the pressure sensed by the pressure sensing means reaches a predetermined value and the attitude detected by the attitude detecting means is within a predetermined range.

5. A mine roof support as claimed in any one of Claims 1 to 4, wherein the attitude detecting means is in the form of one or more tilt switches.

6. A mine roof support as claimed in any one of Claims 1 to 5, wherein the attitude detecting responsive means is in the form of one or more solenoid operated valves.

7. A mine roof support substantially as hereinbefore described with reference to Figures 1 and 2, or Figures 1 and 4, of the accompanying drawings.