GB2197678A - Combined forepole and sprag on mine roof support canopy - Google Patents

Description

Mine Roof Supports 2 19 7 C'? 8 The invention relates to mine roof

supports and particularly to mine roof supports for use in the longwall method of mining. This is a method of working coal seams in which the seam is removed in one series of operations utilising a long working face or wall.

Longwall workings advance or retreat along a line which may be several hundreds of metres in length. The space from which the coal has been removed, variously referred to as the gob, goaf or waste, is either allowed to collapse, known as caving, or may be filled with stone and debris. The Nelson Dictionary of Mining gives more detailed descriptions and definitions.

The space from which coal has been removed, prior to the collapse of the roof, is maintained during the removal of the coal by a row of selfadvancing mine roof supports. Between the supports and the long working face is a scraper chain conveyor which serves both as a means of removing the mined coal from the workings and as a track along which the mineral cutting machine traverses during the mining operation. The mine roof supports are each usually provided with a forwarding projecting cantilever roof-engaging member, to support the mine roof above the conveyor. In this way the roof can be fully supported from the coal face to the waste edge of the workings. Under ideal mining conditions as shown in Figure 1 of the accompanying drawings, a simple form of support is adequate during the performance of the mining cycle which includes removing a strip of coal from the face, advancing the conveyor 10a, and then lowering, advancing and resetting the support lla ready for the removal of the next strip of coal.

Where roof and face conditions are not sound, additional support must be provided such as a forepole which can be extended from the cantilever to provide immediate support 2.

2E 3-E for the newly exposed roof until such time as the roof support itself can be advanced. When the roof support is advanced the forepole is retracted as the cantilever portion of the roof engaging member moves forward to take over the role of supporting the roof up to the mine face. Suc-h a forepole device is described in our co-pending U.E. Patent Application No. 8624745.

Further difficulties may be encountered if the roof is sound but the coal itself is unstable and friable. The coal may collapse or spill along cleats in the coal and it- may be necessary to use face sprags such as are shown at 12a in Figure 2.

A particularly complex combination of conditions may be encounzered when the roof and coal face are both unszable. If the instability is unchecked, the condition shown in -s, F-=-ire 3 result where the face 13a is breaking down in advance of the normal face line (see Figure 1 for comparison purposes). Furthermore, the unstable roof breaks, and it becomes difficult to advance the support to a roof engaging pcsition without using wooden blocks or the like above the nc--r-,,al roof engaging structure. It is not unknown to drill the face and rcof and inset wooden dowels to hold the face and rocf in position to allow mining to continue, but this is cos-_ly and tir-ne consuming, a:-,' is no-c considered desirable -n cirent m-ning practice.

The invention provides a mine roof support having a roof engaging member, there being at least two interconnected 'cad bearing members, one of which is pivotally connected to the roof engaging member.

The use of such interconnected load bearing members makes it possible to make use, in a very effective and versatile manner, of a combination of support techniques su2h as forepoling and spragging, in such a manner that it is possible to cope with adverse conditions where the recuired strata control could not otherwise be achieved resorzing to drilling and dowelling.

3.

It is possible with the invention to provide horizontal spragging support, or vertical forepoling support, and/or a combination of both, in varying configurations which can be adjusted to the mining conditions experienced at the mine roof support location.

By pivotally mounting the members on the roof engaging member, it is possible to provide the necessary support for the strata without interfering with the mining cycle, for example without inhibiting the free passage of a mining machine along a conveyor positioned in front of L,he support.

Preferably the two interconnected load bearing members are connected to an extensible part of the roof engaging structure of the mine roof support.

Preferably there is at least one hydraulic jack operable to move the load bearing members from an inoperative position to a load bearing position.

Each load bearing member may be provided with its own associated hydraulic jack.

The load bearing members together with any associated hydraulic jacks are preferably retractable into a compact stowage position on the underside of the roof engaging structure.

Each member may be capable of bearing a load in any position, including a horizontal position, a vertical position, or any inclined position therebetween.

The load bearing members may be provided with a series of links arranged to reduce loads on the hydraulic jacks.

Preferably the roof engaging member of the mine roof support has an extensible forepole, a first load bearing plate is pivotally connected to the forepole and a second load bearing plate is pivotally connected to the first load bearing plate, hydraulic jacks being provided which are operable to move the plates such that each plate is capable of operating as a face sprag and/or as an extension of the forepole.

4.

Preferably means are provided to pivot the forepole, together with the load bearing plates, with respect to the roof engaging member, for example to move the forepole and load engaging members into engagement with a concavity in the mine roof.

By way of example, a specific embodiment of the invention will now be described, with reference to the accompanying drawings, in which:- Figures 1 to 3 illustrate diagrammatically three types of known mining condition; Figure 4 is a diagrammatic side view, partly in crcss-section, cf part of the roof engaging structure of a known form of mine roof support; Figure 5 is the roof engaging support according Figure 6 is scale; Figure 7 is a view similar to Figure 5 but showing the forepole extended; Figure 8 is a view similar to Figure 7 but showing part of the support acting as a face sprag; and Figure 9 is a view similar to Figure 5 but showing the roof engaging structure fully extended.

C C-- Figures 1 to 3 have already been referred to in the in-,roduction tc this specification.

Referring to Figure 4, reference numeral 10 illustrates the canopy part of a roof engaging structure which in use is attached to roof supporting hydraulic jacks (not shown) at 11 and 12.

At the forward end of the canopy 10 is an articulated extension 13 pivotally attached to the canopy 10 at 14. Re.ative movement between the canopy 10 and the extension 13 is con,-rolled by a slidable wedge 15 which is attached to a hydraulic actuator (not shown) at 16. Within the extension 13 is a forepole bar 16 which is slidably operable by a a view similar to Figure 4 but showing structure of an embodiment of mine roof to the invention in a stowed position; a view of part of Figure 5 to a greater hydraulic jack 17. When the forepole bar 16 is at least partially extended from the extension 13 it can be pivoted upwardly slightly to set it to the mine roof by means of a hydraulically operable capsule 18 which is attached to the forepole bar 16.

The underside of the extension 13 is open at 18 which exposes and gives free access to the underside of the forepole bar 16.

According to the invention, a load bearing assembly illustrated generall) by the reference numeral 9 is pivotally connected to an otherwise conventional forepole bar 16 at 20.

The arrangement is shown in more detail in Figure 6.

A first load bearing member comprises a plate-like member 19 which is pivotally attached to the forepole 16 at 20.

A further load bearing member in the form of a second plate-like member 21 is hingedly attached to the plate19 at 22. Both the plate-like members are substantially the same width as the canopy 10.

A primary link 24 is pivotally connected to the underside of the forepole 16 at 23. A secondary link 25 is pivotally connected to the primary link at 26, is pivotally connected to the plate 19 at 27, and is pivotally connected at 28 to the piston of a hydraulic jack 29.

The cylinder 30 of the hydraulic jack is connected to the forepole bar 16 by means of a pivot 31.

A further hydraulic jack 32 has its cylinder connected to the first plate at 33 and has its piston rod connected to the second plate 21 at 34 by means of a bracket 35.

The plates 19 and 21 may be moved to various positions by means of the jacks 30 and 32 to add greatly to the versatility of the mine roof support.

Figure 7 shows that the extension 13 and forepole bar 16 may be used in a conventional manner if desired, the plates 19 and 21 remaining in a stowed position underneath the forepole bar 16.

6.

Alternatively, as shown in Figure 8. the rams 29 and 32 may be actuated such that the plate 19 operates as an extension of the forepole bar 16 while the plate 21 operates as a face sprag.

In the fully extended position shown in Figure 9, both the plates 19 and 21 act as forward extensions of the forepole bar 16.

The mine roof support according to this embodiment is capable of coping with all the mining conditions shown in Figures 1 to 3. For example, plate 19 can be moved to a vertical position to act as a face sprag in a similar manner to the member 12a shown in Figure 2. If it is necessary to provide support in a situation such as that shown in Figure 3, the plate 19 may be moved into a substantially horizontal position, the plate 21 being moved to a position in which it is at an angle of, for example, 70 0 to plate 19. After a strip of coal has been removed the forepole bar 16 can then be extended, with appropriate adjustment of the plates 19 and 21 if necessary, to provide similar support for the newly cut face and roof.

The gives the necessary position of the support shown in Figure 9 of course maximum reach into the workings, which may be for some conditions.

One sequence of opera-Lion of a mine roof support aeccrd-,ng to the invention will now be described with particular application to adverse mining conditions.

In the first stage the mining machine passes a given mine roof support according to the invention and the forepole 16 is extended by means of its associated hydraulic jack (which may be single or double telescopic to meet the distance requirements) after which a capsule such as 18 is operated to set the forepole bar 16 into contact with the mine roof.

7.

During a second stage the hydraulic jack 29 is operated and acts on links 25 and 24 about the pivot point 20. This operation transmits the force to the pin 27 which pivots the plate 29 about the pin 23. In this way the plate 19 can be transposed into a vertical position. Sequentially the jack 32 is extended and if the coal face is vertical then both plates 19 and 21 will exert a supporting force against the face. In other words they will become aligned in the vertical plane.

In a third stagp, if the face is not vertical then plate 19 will pass through the vertical plane and if no resistance is met it will continue to a horizontal plane and will consequently support the mine roof. When the plate 19 reaches an obstruction, which may be the mineral 0 face, for example at an angle of 45, the plate 21 will again become placed against the face by retracting the ram 32 from its previous position. If on the other hand the plate 19 becomes roof engaging, then the ram 32 retracts still further, sufficient to permit plate 21 to operate as a face support sprag.

In a fourth stage, in extreme conditions, where neither plates 19 nor 21 engage with an upwardly extending coal face, then both rams 30 and 31 will continue to extend until both the plates 19 and 21 become roof engaging.

It will be noted that the forces from the rams 29 and 32 are transmitted through links which have a leverage effect, some of the links being self-locking, which relieves load on the rams 29 and 30 but may transmit load to the capsule 18.

The invention is not restricted to the details of the foregoing embodiment. For example, there may be a single centrally located jack 29 and a pair of jacks 32, one arranged at each side of the jack 29.

Although the load supporting members are shown mounted on the forepole bar 16, it may be possible with narrower 8.

searr,s to utilise a mine roof support which has an extension 13 which is not fitted with a forepole bar. In such a case the load bearing members may be connected directly to the extension 13.

-g- CLA 1 MS 1. A mine roof support having a roof engaging member, there being at least two Interconnectedload contacting and bearing members, one of which Is pivotally connected to the roof engaging member.

Claims (1)

1. 2. A mine roof support as claimed In Claim 1, in which the two

   interconnected load bearing members are connected to an extensible part of the roof engaging structure of the mine roof support.

   3. A mine roof support as claimed In Claim 2, In which there is at least one hydraulic jack operable to move the load bearing members from an Inoperative position to a load bearing position.

   4. A mine roof support as claimed In Claim 3, In which each load bearing member is provided with Its own associated jack.

   5. A mine roof support as claimed In Claim 3 or Claim 4 in which the loadbearing members together with any associated hydraulic jacks are retractable Into a compact stowage position on the underside of the roof engaging structure.

   6. A mine roof support as claimed in any one of Claims 3 to 5, in which the load bearing members are provided with a series of links arranged to reduce loads on the hydraulic jacks.

   7. A mine roof support as claimed in any one of the preceding claims, in which each member is capable of bearing a load In any position, including a horizontal X position, a vertical position, or any Inclined position therebetween.

   S. A mine roof support as claimed In Claim 1, In which the roof engaging member of the mine roof support has an extensible forepole, a first load bearing plate Is pivotally connected to the forepole and a second load bearing plate is pivotally connected to the first load bearing plate, hydraulic jacks being provided which are operable to move the plates such that each plate Is capable of operating as a face sprag and/or as an extension of the forepole.

   g. A mine roof support as claimed In Claim 8, in which means are provided to pivot the forepole, together with the load bearing plates, with respect to the roof engaging member, for example to move the forepole and load engaging members into engagement with a concavity in the mine roof.

   10. A mine roof support, constructed and arranged as substantially as described herein, withreference to the accompanying drawings.