GB2074223A - Root and coal face support - Google Patents

Abstract

A mine roof support (10) has a roofing bar structure (12, 17) supported from a base (11). The roofing bar structure (12, 17) comprises a first part (12) located relative to the base (11 )and an extension member (17) extendible forwardly relative to the first part (12) and then may also be extendible upwardly so as to support the mine roof immediately after the passage of a coal cutting machine (14) and before the roof support (10) itself can be advanced. A coal face support sprag (18) is mounted on the extension member (17) and is extendible and retractable by means of an hydraulic jack (19) whose body is mounted on the extension member (17) and is slidably located on the first part (12) of the roofing bar structure (12, 17). <IMAGE>

Description

SPECIFICATION Roof and coal face support This invention relates to mine roof supports, and in particular to self advancing roof supports used along a coal face.

A plurality of such supports are placed side-byside along the coal face to support the roof in that region whilst the coal is being cut. The conveyor for the cut coal and the track for the coal cutting machine pass across the front of each support.

As the coal cutting machine passes along the coal face there is a region behind the machine in which there is no support for the roof until the roof supports can be moved forward to support that part of the roof. Due to the presence of the aforementioned conveyor and cutting machine track the support immediately behind the coal cutting machine cannot be moved forwardly through the complete distance to the new coal face which is being created behind the coal cutting machine. In practice it is customary to move forwardly through such complete distance a support which is several supports removed from that at which the coal cutting machine is located at any given time, such distance being known as the snaking distance and is the distance by which the conveyor may be advanced from its existing to a new position for the next cutting cycle.The conveyor and the coal cutting machine track take up a snake-like configuration in pian view, and are constructed to take up, and be operable whilst having, such a configuration.

However, such progressive forward movement of the supports does not entirely remove the problem of there being a region behind the coal cutting machine of roof which is unsupported.

There is also a further problem, particularly acute in circumstances wherein the coal is soft and friable, of the tendency of coal to fall from the coal face which is being created behind the coal cutting machine. Apart from the danger factor related to such falls in that there are created further areas of roof which are unsupported there is also the problem of moving the mine roof supports forwardly to support such roof areas due to build up of the loose material in front of the supports.

It is an object of the present invention to provide a mine roof support which enables such aforementioned problems to be overcome or at least substantially alleviated.

The invention provides a mine roof support having a base and a roofing bar structure supported from said base, wherein said roofing bar structure has an extension member mounted thereon and extendible forwardly thereof and a coal face supporting sprag mounted on said extension member.

By means of a support of the present invention the extension member may be extended so that coal face and the roof may be supported in the region behind the coal cutting machine immediately after the passage of the coal cutting machine and before moving the support forwardly to the new coal face. As the support is moved into position adjacent the new coal face the extension member is retracted and the roof support structure and the sprag support the roof and the coal face in the normal manner. The sprag may be set against the coal face whilst the roofing bar is in its extended or retracted position.

Preferably both the extension member and the sprag are extendible and retractable by means of hydraulic jacks, and the hydraulic jack operable to extend and retract the sprag may be secured to the extension member and may also be mounted on the roofing bar structure so as to be slidable therealong as the extension member is extended and retracted. Such spray operating jack may have at least one trunnion secured to the jack body, whereby each such trunnion is adapted to cooperate with a corresponding slot in the roofing bar structure.

One embodiment of the invention will now be further described with reference to the accompanying drawings in which: Fig. 1 is a side elevation of the mine roof support; Fig. 2 is a side elevation of the extension member and sprag of the support of Fig. 1 when in their retracted positions; Fig. 3 is a side elevation of the extension member and sprag of the support of Fig. 1 when in their extended positions.

Referring now to Fig. 1 there is shown a mine roof support 10 having a base 11 and a roofing bar structure 12, the latter being supported from the base by extendible props 13. A coal cutting machine 14 and conveyor 1 5 for the cut coal are shown in dotted lines adjacent a coal face 1 6.

Mounted on the roofing bar structure 12 are an extension member or bar 1 7 and a coal face supporting sprag 1 8. In the configuration shown in Fig. 1 the extension bar 1 7 is retracted and the sprag 1 8 is in its operating or extended position supporting the upper part of the coal face 1 6 whilst the coal cutting machine 14 cuts coal from the lower part of coal face 16.

After coal has been cut from the upper part of the coal face 1 6 the mine roof and the newiy created coal face would be unsupported until the support 10, if of conventional form, could be moved forward to take up a position with respect to the new coal face corresponding to the position shown in Fig. 1 with respect to the coal face 1 6.

Such forward movement could not take place immediately after passage of the coal cutting machine without causing too severe change of direction between adjacent supports of the conveyor 1 5 and track for the cutting machine 14.

However, by means of the support 10 of the present invention the mine roof and coal face may be supported immediately behind the cutting machine 1 4 by extending the extension bar 1 7 and placing the sprag 1 8 against the newly created coal face, until such time that the cutting machine 1 4 is sufficiently removed from the support 10 for that support to be moved forwardly to the new coal face.

The construction of the extension bar 17 and sprag 18 is shown in Figs. 2 and 3. The extension bar 17 is slidably mounted in the roofing bar structure 12, and is actuated to move between the retracted position shown in Fig. 3 to the extended position shown in Fig. 4 by means of an hydraulic jack (not shown). The guides governing the sliding movement of the extension bar 17 are of a form such that the extension bar as it reaches the end of its extension travel, is caused to move upwardly to contact and support the roof, and is lowered before commencing the retraction movement.

In either position of the extension bar 17 the coal face supporting sprag 18 may be moved between its retracted position shown in Fig. 2 and its supporting position shown in Fig. 3. The sprag 18 is moved between these positions by means of hydraulic jack 19. The forward end of the jack 1 9 is supported on the extension bar 17 by means of trunnions 20 in mounting plates 21 whilst the rearward end of the jack 1 9 is supported on the roofing bar structure 12 by means of trunnions 22 which are slidable in slots 23 in guide rails 24. By this means the jack 1 9 can move with the extension bar 1 7 and the rearward end of the jack 1 9 is supported throughout the range of such movement.

A cam plate 25 is provided on the extension bar 17 and is contacted by a spigot 26 on the sprag 1 8 when the sprag is retracted so as to rotate the sprag and retain it in the retracted position shown in Fig. 2 whilst not required in use.

Claims (9)

1. A mine roof support comprising a base and a roofing bar structure supported from said base, said roofing bar structure comprising a first part which is supported by and located relative to said base and an extension member which is extendible forwardly relative to said first part, a coal face supporting sprag mounted on said extension member, sprag extending means mounted on said extension member and location means whereby said sprag extending means is slidably located relative to said first part.

2. A mine roof support according to claim 1 characterised in that said extension member is extendible by means of an hydraulic jack or jacks.

3. A mine roof support according to claim 1 or claim 2 characterised in that said sprag extending means comprises at least one hydraulic jack.

4. A mine roof support according to claim 3 characterised in that said location means comprises at least one trunnion secured to the or each sprag extending jack body and a respective slide secured to the first part of said roofing bar structure.

5. A mine roof support according to any one of claims 1 to 4 characterised in that said extension member is slidably mounted on said first part by means of guides.

6. A mine roof support according to claim 5 characterised in that said guides are adapted to guide said extension member in a path longitudinally of said first part from a retracted position to an extended position, and then upwardly to a roof supporting position.

7. A mine roof support according to any one of claims 1 to 6, charactensed in that a cam means is provided on said extension member, which cam means is adapted to rotate said sprag when being retracted or extended.

8. A mine roof support according to claim 7 characterised in that said cam means is adapted to retain said sprag in a position adjacent said extension member when said cam is retracted.

9. A mine roof support substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.