GB2236788A - Mine roof supports - Google Patents

Abstract

A mine roof support has a base comprising two parallel, relatively vertically moveable floor engaging members 12 and 13, support advancing means 25 and base lifting means 56, 57, the support advancing means comprising a hydraulic jack 25, pivotally attached to the floor engaging members, and the base lifting means comprising link means 50 which enables the base lifting means to lift both floor engaging members 12 and 13 while compensating for any relative vertical movement therebetween. <IMAGE>

Description

MINE ROOF SUPPORTS Underground mine roof supports, primarily for the long wall method of mining, are temporary supports which are advanced sequentially as mineral, for example, coal, is removed from the mineral bearing face. The supports are usually installed in a side by side relationship in a row which runs parallel to the mine face, and during the advancing sequence, when a support is lowered, advanced towards an abutment (usually a scraper chain conveyor) and re-set to the mine roof, each support is guided by the supports on either side which remain set to the mine roof during the advance of the interjacent support.

Not only do the adjacent supports help to guide the interjacent support but they serve to stabilise the support in the vertical plane during its advance. This stabilising effect is particulatly advantageous when the support is being advanced over uneven mine floors and also when the front end of the support is lifted during its advance to clear debris or steps in the mine floor resulting from the passage of the mineral cutting machine along the mine conveyor in front of a row of mine roof supports during the cutting cycle.

Base members of such mine roof supports are usually designed to meet various criteria of which load bearing on and load distribution to, the mine floor are important. Other factors to be considered are the minimum restrictive effect to operatives passing along the row of supports and the provision of a suitable structure to provide a base for the hydraulic legs which are attached to, and support, the mine roof support superstructure. The superstructure may be in the form of a mine roof engaging canopy and horizontal control means for the canopy, usually in the form of a lemniscate linkage at the rear end of the support. Such a linkage usually incorporates an inclined shield to prevent inflow of debris from the rear of support as caving takes place behind the support.

The base of such a mine roof support also provides an attachment and mounting for hydraulic ram means which serves to advance the conveyor when the support is set to the mine roof and to advance the support relative to the conveyor when the roof support is lowered, and is free from the mine roof. The connection between the hydraulic ram means and the conveyor is often by means of a clevis and an elongate link, the elongate link being known as a relay bar.

Mine roof support bases are of three main types (a) rigid; (b) semi-rigid; and (c) flexible. To date it has often been a matter of opinion as to which type of base should be used relative to the particular conditions of a mine floor and the underlying strata which are experienced.

The majority of roof supports in current use are of the rigid type, and examples of these may be found in U.K. Patent No. 2 115 046 and U.K. Patent No. 2 143 882.

Frequently, the bases incorporate a pair of parallel floor engaging skids. The rigid type of base has a tendency to crush any parts of the floor which are slightly above other parts of the floor, and which are directly under the mine base. Where this crushing effect is not possible, the support base may eventually be in contact with three high spots of the floor (or even two, if the support is held vertical by the adjacent supports, whence a hogging effect may result), and such parts of the floor become highly stressed which may result in a breaking of the mine floor which in turn could adversely affect the underlying strata.

Under certain circumstances the cracks and stresses in the strata may extend in the direction of forward movement of the supports, up to the mineral face, eventually creating difficult conditions for the mining operation. It is also a burden on the roof support designer to design a support base which is strong enough to withstand the full load bearing capacity of the support when it may only have a three or two point contact with the mine floor.

For the designer to achieve such strength, the base must have a greater resistance to bending, and have a thicker cross-section than would be otherwise required if the load was evenly distributed over the full area of the base member or members, but this increased thickness makes it more difficult for the operatives to proceed along the row of supports especially in the lower seam heights.

To mitigate the damage to the mine floor and the consequential deterioration in mining conditions, it is often preferable to adopt a semi-rigid base structure, for example of the type described in U.K. Patent No.

1,512.001 (see for example Figure 10) or to provide appropriate working clearance between pivot pins and their corresponding holes in a lemniscate linkage, the cumulative effect of such clearance thus allowing relative vertical movement at the front of the parallel base members, and such movement may for example be 100mm.

This will usually be sufficient to accommodate the variations in the height of the uneven floor level encountered beneath the base area. This degree of flexibility allows the base members not only to be made of thinner cross-section, but it also achieves a far better load distribution on the mine floor and the underlying strata. Whilst the clearance in the linkage pins is beneficial with regard to relative vertical displacement of the base members, it does however produce unacceptable displacement in the horizontal plane and the resultant splaying effect of the base members is often controlled by a pivotal link, such as, for example, the link shown at 74 in Figure 13 of U.K. Patent No. 1 512 001.

Fully flexible bases have extremely limited applications because of their instability during the advance and resetting of the supports, and although their load distribution properties are often better than most other types of supports, any such benefits are outweighed by the disadvantages during the supports advance and -therefore because the invention is not directed to this type of support, such bases will not be discussed further.

Despite the disadvantages of the rigid base supports, insofar as load distribution is concerned, their inherent rigidity simplifies the mounting of an advancing ram between the parallel base members.

Furthermore, the same rigidity means that a simple lifting device for the front end of the support during its advance may be adopted, since the front end can be lifted bodily without the problems associated with one base member being lower than the other, a situation which can occur in a semi-rigid base unit.

The invention seeks to provide a mine roof support having a semi-rigid base, which is able to use an advancing ram and a base lifting arrangement and which has fewer or smaller problems than known arrangements.

Accordingly, the invention provides a mine roof support having a base comprising two parallel, relatively vertical moveable floor engaging members, support advancing means and base lifting means, the support advancing means comprising a hydraulic jack pivotally attached to the floor engaging members, and the base lifting means comprising link means which enables the base lifting means to lift both floor engaging members while compensating for any relative vertical movement therebetween.

The relative vertical movement may comprise initial relative vertical displacement prior to lifting.

The link means may comprise a yoke extending between the floor engaging members.

The yoke may have a central cradle portion to receive the advancing means.

The yoke may be arranged to remain horizontal in spite of relative vertical displacement of the floor engaging members.

Preferably the base lifting means includes- a pair of lifting rams, one mounted on each floor engaging member, each ram acting on an associated end of the yoke.

The advancing means may comprise a relay bar which passes underneath the yoke to take the downward load applied by the lifting rams, via the ends of the yoke.

Preferably, the ends of the yoke engage with the floor engaging members to tie them together and prevent splaying.

Each end of the yoke may be attached to the associated floor engaging member by a connection which allows not only pivotal movement but also sliding vertical movement.

The connection may comprise a pin and slot connection.

A vertical slot may be provided on the floor engaging member in which a pin of the yoke can pivot and slide.

The slot may be provided by a vertical strap.

Means may be provided to reduce friction between the relay bar and the yoke as the relay bar slides under the yoke in the fore and aft direction.

Abutment means may be provided to reduce any tendency for the yoke to be moved in the fore and aft direction by its sliding engagement with the relay bar.

The abutment means may comprise the strap.

There may be two straps, on each floor engaging member, one in front of the yoke, and one behind the yoke, each.end of the yoke having a pair of pins, one engaging in each strap.

The pins may be provided by the two ends of a single rod welded or otherwise secured to the associated end of the yoke.

The relay bar may be pivotally connected to an advancing ram of the purport advancing means, the relay bar having an elongate extension which extends rearwardly of the said pivotal connection, underneath the yoke and the advancing ram.

The front end of the relay bar may have means for connecting the relay bar to an abutment, for example a conveyor, which causes the advancing ram to act, during.

advancement of the abutment, along a line extending above the centre of gravity of the abutment.

The advancing ram may have means for connecting the ram to the base of the support, the connection comprising a gimbal arrangement.

The advancing ram may be connectable at more than one location, the locations being spaced apart in the vertical direction.

The gimbal arrangement may comprise shear pins which shear off to protect the advancing ram from damage, in the event of excess twisting of the base of the support.

The shear pins may be connected to the base by fixing means spaced forwardly of the shear pins themselves.

While it is preferred to use base lifting means comprising two separate lifting rams, it is possible to use a single ram, for example acting on a yoke of the type illustrated, or on a yoke which can tilt to accommodate relative vertical displacement of the floor engaging members.

By way of example, a specific embodiment of hydraulic mine roof support will now be described, with reference to the accompanying drawings, in which : Figure 1 is a side view of part of the base of the support, showing the support connected to the front part of a mine face conveyor by means of an advancing ram and relay bar; Figure 2 is a view similar to Figure 1 but showing the advancing ram in the extended position; Figure 3 is a plan view of the parts shown in Figures 1 and 2; Figure 4 is a front view of the front end of the base, showing how a connection between the front ends of the base can cope with relative vertical movement between the front ends of the base; Figure 5 is a side view of the relay bar; Figure 6 is a plan view of the relay bar; Figure 7 is a front view of the connection between the front ends of the base;; Figure 8 is an underplan view of the components shown in Figure 7; Figure 9 is a side view of a component for mounting the relay bar; Figure 10 is a plan view of the component shown in Figure 9; Figure 11 is a plan view of a rear pivotal link of the support; Figure 12 is a cross-section on line XII-XII of Figure 11; Figure 13 is a cross section line XIII-XIII of Figure 11; Figure 14 illustrates a complete support; and Figure 15 is a view similar to Figure 1 but showing the advancing ram mounted in a different position.

The mine roof support forming the subject of this embodiment is designed as self advancing mine roof support, for connection to the trailing edge 10 of a mining conveyor 9 by means of a clevis 11. The clevis 11 can pivot about a vertical axis 12 to accommodate slight misalignment of the support with respect to the conveyor 10.

The base of the support comprises essentially two parallel skids 12 and 13. Each pair of skids has, at its rear end, an upper pivot hole 14 and a lower, rear pivot hole 15. Each hole 14 is pivotally connected, by a separate, associated link, with a rear shield member (see Figure 14). Holes 15 are also pivotally connected to the shield member, but by a single unitary member 16 shown in Figures 11 and 12.

A first pair of plates 17 form a first link which is pivotally connected to the skid 12, and a second pair of plates 18 form a second link which is pivotally connected to the skid 13. All the plates 17 and 18 are rigidly cross-braced by an upper plate 19 and a lower plate 20. Between the inner plate 17 and the inner plate 18 there are additional cross-bracing members 21 and 22.

Between each pair of plates 17 and each pair of plates 18, there is further cross-bracing 23 and 24.

The shield member 8 is pivotally connected to an upper, roof engaging canopy 7, in a conventional manner, and a pair of hydraulic support legs 6 extend between the base and the canopy (see Figure 14).

The self-advancing ram for the support comprises a cylinder 25 from which projects a piston rod 26. The rear end of the cylinder 25 is supported in a gimbal arrangement shown generally at 27.

Each side of the cylinder 25 is provided with a bracket 28 from which projects a horizontal pivot pin 29.

Each of the skids 12 and 13 has, at its rear end, on its inner face, a bracket 30 having an upwardly facing mouth 31 to receive the pins 29.

Once the pins 29 have been dropped into the mouths 31, each bracket can be closed by the insertion of a pair of shear pins 32, 33, which are best shown in Figures 9 and 10. Each pair of pins 32, 33, is welded to a short vertical plate 34 which is, in turn, welded to a horizontal plate 35 having two vertical fixing holes 36.

The shear pins 32 and 33 are pushed into receiving holes in the arms of the bracket 30 and the plate 36 is then bolted to the associated skid as best shown in Figure 3.

The area of the gimbals, which lies in the region of the rear pivot links, is very restricted. The provision of the elongate plates 35 means that the fixing holes 36 are moved considerably forward with respect to the position of the gimbals, to a point where access is easier. This facilitates the mounting of the advancing ram, and the removal of the advancing ram when necessary, for example for repair or maintenance.

The linkage arrangement at the rear of the support, including the composite link shown in Figures 11 to 13, holds the rear ends of the skid substantially in the same horizontal plane, but the skids can pivot slightly with respect to one another, about the rear transversely extending pivotal axes, so that it is possible for the front end of the skids to move vertically with respect to one another, as is demonstrated in Figure 4. This gives the base the facility to align itself to an uneven mine floor, to a certain extent.

During any relative pivotal movement of the skids, the cylinder 25 is still able to move freely, since it can pivot about a transverse axis by means of the pins 29, and since these pins 29 can rock slightly on the shear pins 32 or 33, the cylinder can also accommodate any slight relative vertical movement between the rear ends of the skids, since all relative vertical movement at the rear end will not be totally eliminated.

The provision of two shear pins 32 and 33 on each connection member makes it possible to mount the pins 29 in a selected one of two vertical positions, depending on the line of action which it is desired to give to the ram. The first position, in which the pins 29 are shown positioned underneath the shear pins 33, is shown in Figures 1 and 2. In the alternative position, in which the pins 29 are positioned between the shear pins 32 and 33, the rear end of the cylinder 25 is raised slightly, and this may, for example, be useful with a particularly loose mine floor, when it will be easier for loose debris to pass underneath the cylinder 25 as the mine support advances.

If there is any excessive twisting at the rear of the support, one or other of the pins 32 or 33 will shear off, thus protecting the ram from damage.

The front end of the piston rod 26 is connected to the clevis 11 by a relay bar 37.

The clevis 11 has an inclined slot 38, a pivot pin 39 passes through this slot and through a hole 40 in a front lug 41 of the relay bar 37. When the advancing ram retracts, to pull the support forwardly, the pin 39 will engage the right hand end of the slot 38 as viewed in Figure 1. However, when the ram extends to push the conveyor 10 forwardly, an upper nose 42 of the lug 41 will engage a curved plate 43 of the clevis 11. This ensures that the force applied by the advancing ram acts along a line which is above the centre of gravity of the conveyor, thus tending to lift the trailing edge of the conveyor slightly as it moves forwardly, facilitating its scraping and collecting movement over the mine floor.

The relay bar is shown in detail in Figures 5 and 6. It will be seen that the connection between the conveyor and the piston rod is relatively short, since the piston rod is pivotally connected at 43. Thus the relay bar has along rearward extension 44 which passes underneath the support, as shown in Figure 1.

This rearward extension of the relay bar serves three functions. Firstly, it gives considerable guidance to the movement of the relay bar and makes it possible to use a thinner relay bar than in known constructions, which has advantages, particularly with regard to thin mineral seams, where very littlesspace is available.

Secondly, the relay bar tends to protect the advancing ram for a substantial part of its movement.

Thirdly, the relay bar provides a sliding abutment to receive the force from a pair of front lifting rams, which form a very important part of this invention, as will be described below.

To assist in locating the support when the advancing ram returns to its closed position, the relay bar has a pair of wedge portions 45 at its front end, which co-operate with chamfered portions 46 at the front end of the skids.

As the roof support moves forwards, it can encounter significant obstructions, either in the form of large pieces of debris or, more commonly, in the form of slight steps in the mine floor, caused by the transverse passage of the mining machine as it cuts away a web of mineral, and in so doing follows the contour of the band of mineral in the surrounding strata.

It is therefore desirable to have some means of lifting the front end of the skids as the support advances and arrangements are known in which a vertically acting ram is provided which pushes down on a relay bar, thus raising the front of the base with respect to the relay bar.

As can be seen in Figure 4, this embodiment provides for noticeable relative vertical movement between the front end of the skids. We have developed a novel arrangement which interconnects the front ends of the skids, thus preventing them from splaying apart as the support advances, and also provides a means of lifting and aliging the front ends of the skids, while allowing for relative movement such as that shown in Figure 4.

On the inner face of the skid 12, there is provided a first pair of straps 47. The inner face of the skid 13 has a similar pair of straps 48.

Figures 7 and 8 show in detail a connecting yoke comprising a plate 49 which has a curved central portion 50 to accommodate the piston rod 26. At each end there is a projecting rod 51, 52. The rods 51 and 52 fit within the pairs of straps 47 and 48 respectively. Thus the yoke 49 can remain horizontal, even if the front ends of the skids move vertically with respect to one another, as can be seen from Figure 4.

Although the yoke 49 permits relative vertical movement between the front ends of the skids, it ties them together and prevents them from splaying apart in the transverse direction.

Each end of the yoke 49 has, on its upper surface, a pair of lugs 53, 54. The lugs 53 are pivotally connected to the lower end of the piston rod 55 of a first lifting ram 56. The lugs 54 are pivotally connected to the lower end of the piston rod of a second lifting ram 57. The ram 56 is pivotally mounted on the inner face of the skid 12 and the ram 57 is pivotally mounted on the inner face of the skid 13. The pivotal axis is horizontal, in the direction of travel of the support, as can be seen from the pivot pins 58 of the ram 56 in Figure 1.

The yoke has, underneath each pair of lugs 53, 54, at the points 59, 60, a pair of pressure pads which engage slidably on the top of the relay bar 37.

When it is desired to raise the front of the support, as the support is moving forward, hydraulic pressure is applied simultaneously to the rams 56 and 57.

When this pressure is applied, both rams 56 and 57 extend to their fullest extent. The pressure pads bear down on the relay bar and this provides the necessary reaction force which lifts the cylinders of the rams, and hence the front ends of the skids, until the front ends of the skids are both positioned at their maximum height above the relay bar for convenient movement over the mine floor. Because the pressure pads are of low friction material, the relay bar 37 can still slide freely under the loaded pressure pads.

If, at the start of base lift, one skid has its front end higher than the other skid, for example because of an uneven mine floor, the base lifting arrangement still operates efficiently, although of course one of the rams 56, 57 does not have to extend as much as the other.

For example, in Figure 4, the left hand skid is already at a higher position because of an obstruction on the mine floor, and so the ram 56 only needs to extend for the final part of its stroke, whereas the ram 57 will extend for its full stroke.

The arrangement shown makes it possible to use two small lifting rams, rather than one large lifting ram, and this provides a further space saving, which, coupled with the thinner relay bar, makes the support particularly suitable for thin seam working.

The arrangement also, coupled with the arrangement of the clevis 11, makes it possible to provide efficient forward movement of the conveyor and support, without using an inclined advancing ram, which provides further space saving in the vertical direction.

A further advantage of using two, smaller, spaced apart lifting rams, rather than one large central lifting ram, is that greater space is provided for dirt clearance through the support as the support moves forwardly.

The yoke serves three purposes. Firstly, it relieves any lateral load on the rams 56 and 57.

Secondly, it prevents the front ends of the skids from splaying apart.

Thirdly, it guides the skids during any relative vertical movement.

Although the pressure pads are of low friction material, there is nevertheless a slight tendency for the pads to be pushed forwardly as the relay bar moves forwardly. However, the straps 47 and 48 not only provide guides for the bars 51 and 52, but they also provide abutments which locate the yoke 49 and prevent any forward or rear movement of the yoke 49. Thus any tendency for the pressure of the pads to be pushed forwardly is prevented, relieving any tendency for the piston rods of the rams 56 and 57 to bend forwardly or rearwardly.

Although the embodiment shown is intended to accommodate two hydraulic lifting legs, the embodiment may be modified for use with hydraulic mine roof supports having more than two legs, for example four legs.

In other embodiments, where there is no tendency for the front ends of the skids to splay apart, or where other means are provided to prevent splaying, the rods 51 and 52 at the ends of the yoke may be dispensed with, although it may still be desirable to have the straps 47 and 48, or at least other abutments, to locate the yoke in the fore and aft direction, and prevent the application of fore and aft bending stresses to the piston rods of the rams 56 and 57.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification 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 (24)

1. A mine roof support having a base comprising two parallel, relatively vertically moveable floor engaging members, support advancing means and base lifting means, the support advancing means comprising a hydraulic jack pivotally attached to the floor engaging members, and the base lifting means comprising link means which enables the base lifting means to lift both floor engaging members whilst compensating for any relative vertical movement therebetween.

2. A mine roof support as claimed in Claim 1, in which the relative vertical movement comprises initial relative vertical displacement prior to lifting.

3. A mine roof support as claimed in Claim 1 or Claim 2, in which the link means comprises a yoke extending between the floor engaging members.

4. A mine roof support as claimed in Claim 3, in which the yoke has a central cradle portion to receive the advancing means.

5. A mine roof support as claimed in Claim 3 or Claim 4, in which the yoke is arranged to remain horizontal in spite of relative vertical displacement of the floor engaging members.

6. A mine roof support as claimed in any one of Claims 3 to 5, in which the base lifting means includes a pair of lifting rams, one mounted on each floor engaging member, each ram acting on an associated end of the yoke.

7. A mine roof support as claimed in any one of Claims 3 to 6, in which the advancing means comprises a relay bar which passes underneath the yoke to take the downward load applied by the lifting rams, via the ends of the yoke.

8. A mine roof support as claimed in any one of Claims 3 to 7, in which the ends of the yoke engage with the floor engaging members to tie them together and prevent splaying.

9. A mine roof support as claimed in Claim 8, in which each end of the yoke is attached to the associated floor engaging member by a connection which allows not only pivotal movement but also sliding vertical movement.

10. A mine roof support as claimed in Claim 9, in which the connection comprises a pin and slot connection.

11. A mine roof support as claimed in Claim 10, in which a vertical slot is provided on the floor engaging member in which a pin of the yoke can pivot and slide.

12. A mine roof support as claimed in Claim 11, in which the slot is provided by a vertical strap.

13. A mine roof support as claimed in any one of Claims 9 to 12, in which means are provided to reduce friction between the relay bar and the yoke as the relay bar slides under the yoke in the fore and aft direction.

14. A mine roof support as claimed in any one of Claims 9 to 13, in which abutments means are provided to reduce any tendency for the yoke to be moved in the fore and aft direction by its sliding engagement with the relay bar.

15. A mine roof support as claimed in Claim 15, in which the abutment means comprises a strap.

16. A mine roof support as claimed in Claim 15, in which there are two straps, on each floor engaging member, one in front of the yoke, and one behind the yoke, each end of the yoke having a pair of pins, one engaging in each strap.

17. A mine roof support as claimed in Claim 16, in which the pins are provided by the two ends of a single rod welded or otherwise secured to the associated end of the yoke.

18. A mine roof support as claimed in any one of Claims 7 to 17, in which the relay bar is pivotally connected to an advancing ram of the support advancing means, the relay bar having an elongate extension which extends rearwardly of the said pivotal connection, underneath the yoke and the advancing ram.

19. A mine roof support as claimed in any one of Claims 7 to 18, in which the front end of the relay bar has means for connecting the relay bar to an abutment such as a conveyor, which causes the advancing ram to act, during advancement of the abutment, along a line extending above the centre of gravity of the abutment.

20. A mine roof support as claimed in any one of the preceding Claims in which the advancing jack has means for connecting the jack to the base of the support, the connecting comprising a gimbal arrangement.

21. A mine roof support as claimed in Claim 20, in which the advancing ram is connectable at more than one location, the locations being spaced apart in the vertical direction.

22. A mine roof support as claimed in Claim 20 or Claim 21, in which the gimbal arrangement comprises shear pins which shear off to protect the advancing jack from damage, in the even of excess twisting of the base of the support.

23. A mine roof support as claimed in Claim 22, in which the shear pins are connected to the base by fixing means spaced forwardly of the shear pins themselves.

24. A mine roof support constructed and arranged substantially as herein described, with reference to the accompanying drawings.