GB2155089A

GB2155089A - Mine roof support with rear linkage

Info

Publication number: GB2155089A
Application number: GB08405568A
Authority: GB
Inventors: Archelaius Dawson Allen
Original assignee: Dobson Park Industries Ltd
Current assignee: Joy Global Industries Ltd
Priority date: 1984-03-02
Filing date: 1984-03-02
Publication date: 1985-09-18
Also published as: GB8405568D0

Abstract

A mine roof support has a floor engaging base 10, a roof engaging canopy 14, load bearing hydraulic jack means 17 operable to urge the base and canopy apart, a downward projection 16 from the roof engaging canopy providing a pivot 20 at the lower end thereof, an upward projection 18 from the floor engaging base providing a pivot 19 at the upper end thereof, and a fixed length link 21 connecting the said pivots in such a manner that the canopy pivot is capable of moving higher and/ or lower than the base pivot. <IMAGE>

Description

SPECIFICATION Mine roof supports The invention relates to mine roof supports.

The latest generation of mine roof supports usually have a floor engaging base and a roof engaging canopy interconnected by a so-called lemniscate linkage, i.e. a series of links which influence the position of the roof engaging canopy relative to the floor engaging base and to the coal face. The linkage is usually positioned pivotally adjacent rearmost hydraulic jacks acting between the base and the canopy.

For all practical purposes the linkages of the lemniscate type achieve the objective of relative control, but have the disadvantage that as the canopy is lowered, the linkages project more and more into the goaf. An example of such a known lemniscate linkage is shown in our co-pending Patent Application No.8227327. With such an arrangement the movement of the canopy may be restricted by caved debris behind the support such that the canopy cannot be lowered successfully, an essential operation prior to advancing the support.

Some roof supports are constructed with a reverse lemniscate linkage, in other words one in which the links are inclined forwardly from the base rather than rearwardly. However when such a support is lowered the lemniscate linkage projects further and further into the walkway, thus restricting the movement of men and materials along the walkway.

Problems caused as the canopy is lowered by this gradual projection of the lemniscate linkage is more prominent on narrow seam supports where the horizontal projection into the goaf or walkway is great relative to the vertical movement of the points of attachment of the linkage to the canopy.

The invention seeks to reduce this undesirable projection effect, whilst still enabling the roof engaging canopy to be iaterally restrained.

Accordingly the invention provides a mine roof support having a floor engaging base, a roof engaging canopy, load bearing hydraulic jack means operable to urge the base and canopy apart, a downward projection from the roof engaging canopy providing a pivot at the lower end thereof, an upward projection from the floor engaging base providing a pivot at the upper end thereof, and a fixed length link connecting the said pivots in such a manner that the canopy pivot is capable of moving higher and/or lower than the base pivot.

Thus a single link is located at a position whereby the resultant of the horizontal movement of its moving pivot is smali compared with the vertical movement of the same arcuate moving pivot, i.e.

the chordal length is great compared with the height of the segment produced thereby.

Preferably the working range of the support is such that the distance that the canopy pivot moves above the base pivot during use is equal to the distance that the canopy pivot moves below the base pivot.

For example, the working range of the support from a set position to a lowered position may be six inches, the canopy pivot being capable of moving three inches above the base pivot and three inches below the base pivot.

Although the working range may, for example, be six inches, the canopy may be capable of moving over a greater total range, for example thirty-six inches, for transportation and storage purposes.

Thus the working range is towards the upper end of the total range of movement.

Preferably a link as defined above is provided at each side of the support to offer stability to the load bearing hydraulic jack means.

The load bearing hydraulic jack means may be pivotally connected to the base and to the canopy, to accommodate the resultant horizontal movement of the moving pivot.

Preferably the connections of the load bearing jack means and the links are such that the canopy is stable in all horizontal directions.

The downward projection from the canopy may conveniently be in the form of a "wrap around " shield which also serves to protect the links from caving material, which would otherwise damage or restrict the movement thereof.

The load bearing hydraulic jack means may comprise any desired configuration, for example two jacks arranged in a single row, orfourjacks arranged in a double row.

Where four jacks are used the upward projection may be of the wrap around shield type, there being a link arranged at each-outer side thereof, i.e.

interjacent the upper and lower shields.

Where two jacks are used, the jacks may be inclined towards the leading edge of the support to improve the stability of the support. This reduces the canopy out-of-balance lever effect on the jacks, which would otherwise tend to cause them to lower off too quickly when pressure fluid in the jacks is exhausted to release the canopy from the mine roof in order to advance the support to a new position.

By way of example, two specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic side view of one embodiment of mine roof support according to the invention; Figure 2 is a diagrammatic plan view of the support shown in Figure 1,with the roof engaging canopy removed; and Figure 3 is a diagrammatic side view of an alternative embodiment of mine roof support according to the invention.

The support shown in Figures 1 and 2 comprises a floor engaging base 10 made up of two elongate skids 11 and 12 interconnected at the forward end by a bridge 13. The support also has a rigid roof engaging canopy 14 composed of a substantially planar rigid top portion 15 and an integral downwardly extending projection 16 in the form of a wrap around shield. Four hydraulic jacks 17, arranged in two rows, extend from the base 10 to the canopy 14.

Each of the skids 11 and 12 has an integral upward projection 18 (which may form part of a wrap around shield adjoining skids 11 and 12 at the rear thereof) having a pivot point 19 at its upper end. The lower part of the shield 16 is provided at each side with a pivot point 20. Each pivot point 19 is connected to the adjacent pivot point 20 by a single rigid link 21 of fixed length.

Previously it has always been thought necessary to have a pair of links at each side of a mine roof support in order to give the necessary control of the roof engaging canopy relative to the floor engaging base. However we have discovered, somewhat surprisingly, that it is possible to provide the necessary control and stability with only a single link as shows in Figures 1 and 2, the link extending between projections rigid with the base and canopy.

The support in Figure 1 is shown in its set position, i.e. its highest working position. The movement which the link 21 will make as the canopy is lowered to its lowest wdrking position is illustrated by the arc in Figure 1 and it will be seen that the linkwill sweep through an angle A. In other words the link is horizontal at the central point of its working movement. This in turn has the effect that during the working movement of the link the horizontal component of movement of the moving pivot 20 is very small in relation to the vertical movement of this pivot. In other words the link will not project significantly into the goaf during the working range.

The support also has an advancing ram 22 connected between the skids 11. The piston rod of the ram passes underneath the bridge 13 and has a connection 23 for fastening the ram to a mine conveyor. However this ram 22 is itself conventional and need not be described in further detail.

Although the canopy has been removed in Figure 2, the position which would be occupied by the shield 16 is shown in dotted lines in Figure 2 to illustrate how the shield wraps around the links 21 to protectthem.

Turning now to Figure 3, there is shown an alternative embodiment of mine roof support which operates on the same principle but utilises only one pair of load bearing jacks 17. Once again there is a base 10 having at each side an upward projection 18 carrying a pivot 19 at its upper end. There is a rigid roof engaging canopy 14 having a downwardly extending projection 14a carrying a pivot 20 at each side thereof. Links 21 interconnect each pivot 19 with one of the pivots 20 and the working range of movement of the links 21 is substantially identical to the links 21 of Figures 1 and 2.

The rams 17 are inclined forwardly towards the leading edge of the support. In other words the point where they are connected to the roof engaging canopy 14 lies forwardly of the point where they are connected to the floor engaging base 10.

To provideforthe"working range" of a support being at the upper part of the total travel the upward projection 18 and downward projection 16 may be provided with a series of holes, that may be selectively used as the associated pivot point to ensure the working range being equi-distant about the base position 19.

The invention is not restricted to the details of the foregoing embodiments. For instance means may be provided to restrict pivotal movement of the canopy of Figure 3 about its connection to the rams 17.

Claims

1. A mine roof support having a floor engaging base, a roof engaging canopy, load bearing hydraulic jack means operable to urge the base and canopy apart, a downward projection from the roof engaging canopy providing a pivot at the lower end thereof, an upward projection from the floor engaging base providing a pivot at the upper end thereof, and a fixed length link connecting the said pivots in such a manner that the canopy pivot is capable of moving higher and/or lower than the base pivot.

2. A mine roof support as claimed in claim 1, in which the working range of the support is such that the distance that the canopy pivot moves above the base pivot during use is equal to the distance that the canopy pivot moves below the base pivot.

3. A mine roof support as claimed in claim 2, in which the working range of the support from a set position to a lowered position is six inches, the canopy pivot being capable of moving three inches above the base pivot and three inches below the base pivot.

4. A mine roof support as claimed in any one of the preceding claims in which a link is provided at each side of the support to offer stability to the load bearing hydraulic jack means.

5. A mine roof support as claimed in any one of the preceding claims, in which the hydraulic jack means is pivotaily connected to the base and to the canopy, to accommodate the resultant horizontal movement of the moving pivot.

6. A mine roof support as claimed in any one of the preceding claims, in which the connections of the load bearing jack means and the link or links is such that the canopy is stable in all horizontal directions.

7. A mine roof support as claimed in any one of the preceding claims, in which the downward projection from the canopy may conveniently be in the form of a wrap around shield which also serves to protect the link or links from caving material, which would otherwise damage or restrict movement of the link or links.

8. A mine roof support as claimed in any one of the preceding claims, in which the configuration of the load bearing jack means comprises two jacks arranged in a single row.

9. A mine roof support as claimed in any one of claims 1 to 7, in which the configuration of the load bearing jack means comprises four jacks arranged in a double row.

10. A mine roof support as claimed in any one of the preceding claims, in which the upward projection is of the wrap around shield type.

11. A mine roof support as claimed in claim 10, when dependent on claim 7, in which a link is arranged at each outer side of the upward projection, i.e. interjacent the upper and lower shields.

12. A mine roof support as claimed in any one of claims 1 to 8, in which two jacks are used, the jacks being inclined towards the leading edge of the support to improve the stability of the support.

13. A mine roof support constructed and arranged substantially as herein described, with reference to Figures 1 and 2 of the accompanying drawings.

14. A mine roof support constructed and arranged substantially as herein described, with reference to Figure 3 ofthe accompanying drawings.