US3911686A

US3911686A - Mineral mining installations

Info

Publication number: US3911686A
Application number: US459986A
Authority: US
Inventors: Kunibert Becker; Norbert Holken; Lubomir Plevak; Egon Wojaczek
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1973-04-19
Filing date: 1974-04-11
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: BE812443A; DE2319909C2; CA990959A; JPS5014127A; GB1470436A; FR2226550A1; HU169525B; DE2319909A1; ES425435A1; FR2226550B1; PL90458B1; CS208168B2; JPS5743720B2; AU6752774A; SU588930A3

Abstract

A support assembly for a mine installation which has a floor sill connected to a goaf shield with the aid of a pivotable support member. Telescopic props are articulated between the shield and the floor sill and the shield carries a roof cap. A piston and cylinder unit is provided to swing the support member and hence the shield towards or away from the associated mineral face. A hydraulic ram used to shift the assembly is connected between the sill and the centre of a thrust member. The thrust member is pivotably linked to a coupling element which can connect with a longwall conveyor. Each end of the thrust member is connected to a resilient guide bar which extends through guide members secured to the floor sill. The arrangement is such as to permit a degree of vertical or angular displacement between the floor sill and the conveyor. The goaf shield is constructed from a main wall and separate side walls which have portions overlapping the main wall. One of these side walls is displaceable in relation to the main wall and is preferably resiliently displaceable.

Description

United States Patent Becker et al.

Oct. 14, 1975 MINERAL NHNING INSTALLATIONS 1,037,734 8/1966 United Kingdom 61/45 D Primary Examiner-Paul R. Gilliam Assistant ExaminerDavid H. Corbin Attorney, Agent, or FirmSughrue, Rothwell, Mion,

Zinn & Macpeak [73] Assignee: Gewerkschaft Eisenhutte Westfalia,

Wethmar, near Lunen, Westphalia, Gemany [57] ABSTRACT [22] Filed; Apr. 1 1 1974 A support assembly for a mine installation which has a floor sill connected to a goaf shield with the aid of a pp 459,986 pivotable support member. Telescopic props are articulated between the shield and the floor sill and the [30] Foreign Application Priority Data shield carries a roof cap. A piston and cylinder unit is A r 19 1973 German 2319909 prov1ded to swing the support member and hence the p y shield towards or away from the associated mineral face. Av hydraulic ram used to shift the assembly is 3 g i i connected between the s1ll and the centre of a thrust [58] Fieid 299/31 member. The thrust member is pivotably linked to a 7 coupling element which can connect with a longwall conveyor. Each end of the thrust member is connected to a resilient guide bar which extends through [56] References Clted guide members secured to the floor sill. The arrange- UNITED STATES PATENTS ment is such as to permit a degree of vertical or angu- 3,376,707 4/1968 Dommann 61/45 D lar displacement between the floor and the con- 34l8814 12/1968 Groetschel 61/45 D veyor. The goaf shield is constructed from a main wall 5 2 2 g 2 2 and separate side walls which have portions overlapgg g g 641973 D ping the main wall. One of these side walls is displace- 3837l70 9/1974 g'' 'g 61/45 D able in relation to the main wall and is preferably resilv ientl dis laceable.

FOREIGN PATENTS OR APPLICATIONS y p 1,211,437 3/1960 France 61/45 D 21 Clam, 5 D'awmg 33 52 ll 52 53 "I 5 so 6 6 51 5Q 1 l 1 I k l TII'IIA US. Patent Oct. 14, 1975- Sheet1of3 3,911,686

@N N H a R 2 MINERAL MINING INSTALLATIONS BACKGROUND TO THE INVENTION The present invention relates to a mineral mining installation and more particularly to a support assembly therefor.

Support assemblies are known with a variety of constructions. It is known to provide an assembly with a shield structure which is arranged to provide a screen at the goaf side of the assembly. The assembly normally employs telescopic props connected between a floor engaging member and or a roof girder. Hence the shield must be designed so that it can move as the props are extended or retracted. In a complete mine working several assemblies would be arranged side-by-side and it is generally desirable to have their shields co-operate in screening off the stowage. This has, however, generally involved a number of difficulties. Another problem encountered with such asssemblies is the provision of reliable guidance and alignment when the assemblies are shifted up to follow the working progress.

With regard to the foregoing a general object of the present invention is to provide an improved form of support assembly.

SUMMARY OF THE INVENTION In one aspect the invention provides a mineral mining installation or support assembly which comprises a floor sill, a shield, the shield being composed of a main wall and side walls, at least one hydraulically operated telescopic prop operably disposed between the floor sill and the shield, means for moving the shield in relation to the floor sill, and means permitting at least one of the side walls to move relative to the main wall.

In another aspect the invention provides a mineral mining installation or support assembly which comprises a floor sill, a shield, at least one hydraulically operated telescopic prop operably disposed between the floor sill and the shield,a thrust member, means for selectively connecting the thrust member to a longwall conveyor, a hydraulic ram operably connected between the floor sill and said thrust member and operable thereon during use to effect relative movement between the floor sill and the conveyor and guiding and alignment means in the form of a plurality of guide bars and associated guide members, the guide bars being connected to the thrust member with the ram being disposed between the guide bars and the guide members being attached to the floor sill with the guide bars extending through the guide members.

A support member also provided with side walls which overlap with the side walls of the shield can be pivotably connected to the floor sill and to the shield.

A piston and cylinder unit used to move the shield can be interposed between the floor sill and the support member.

In general, the invention provides a support assembly which is robust and reliable in operation. It is notable that where several assemblies are arranged side-by-side the provision of the displaceable side walls for the shields enables the shields to contact one another, to

provide a more or less continuous screen. Moreover, the engagement between the shields provides an advantageousguiding facility which serves to mutually align the assemblies during shifting even where the floor of the working inclines considerably. The main guiding and alignment is however provided by the guide bars and the thrust member which operate near the floor of the working. Preferably the guide bars are resilient and the movable side wall of the shield is also acted on by spring means to urge the side wall laterally outwards. This combined resilience inhibits the assemblies from becoming jammed during shifting, even where the floor is uneven and inclined. To enable the assembly to adapt to unevenness in the floor it is preferable for the guide members to have apertures therein through which the guide members extend, the apertures permitting vertical displacement of the guide bars in relation to the guide members. In a preferred construction each guide bar extends through two guide members which are spaced apart in a direction extending along the longitudinal axis of the guide bar, the aperture in the guide member nearest the thrust member being of greater length than that of the other guide member so that the guide bar can move vertically in relation to the guide member nearest the thrust member by a greater amount than that in relation to the other guide member. The guide bars are then pivotably connected to the thrust member in such manner as to permit a degree of vertical displacement between each guide bar and the thrust member. The thrust member may be connected by means of a vertical pivot pin to a coupling piece or element which is adapted to connect to the goaf side of the longwall conveyor. Normally the conveyor would support a winning machine such as a plough and to enable the conveyor to move vertically in relation to the floor sill of an assembly as the plough is moved alongside the assembly, it is desirable for the thrust member to have slots extending generally in the longitudinal direction of the ram, the ram being connected to a pin which is slidably received within the slots of said thrust member.

Preferably the movable side wall of the shield is connected to a hydraulic piston and cylinder unit usable to displace the wall. More particularly, each side wall of the shield may connect to a rod whichis slidably guided through a guide block carried by the main wall, the rods connected to the side walls being interconnected through a hydraulic piston and cylinder unit. Each rod may carry a detachable stop member engageable on a face of the associated guide block to limit the outward displacement of the side walls. A sleeve can be provided on the rod connected to the other of the side walls, said sleeve engaging on a further face of the associated guide block which is opposite the firstmentioned face, the sleeve and the stop member serving to fix said side wall in position. In contrast a spring can be provided on the rod connected to said at least one side wall, said spring engaging on a further face of the associated guide block which is opposite the firstmentioned face thereto and serving to urge said side wall outwardly. The sleeve and stop member can thus make one side wall essentially rigid but adjustable while the spring and piston and cylinder unit makes the other side wall adjustable and resiliently movable during operation. In a complete working the rigid side wall of one assembly can engage on the movable side wall of the next assembly.

The invention may be understood more readily and various other features of the invention may become more apparent from consideration of the following description:

BRIEF DESCRIPTION OF DRAWINGS An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic side view of a support assembly of a mineral mining installation made in accordance with the invention, the view being taken in the direction of a longwall working;

FIG. 2 is a schematic side view of a lower part of the assembly showing the associated conveyor;

FIG. 3 is a plan view of the part of the assembly depicted in FIG. 2.

FIG. 4 is an end view of the assembly,-the view being taken in the direction of arrow IV in FIG. 1; and

FIG. 5 is a sectional view taken along the line V-V of FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENT As shown in the drawings a mineral mining installation employs a goaf support assembly which has a floor sill which is disposed, during use, at the goaf side of a longwall conveyor, denoted 45 in FIGS. 2 and 3. As is known the conveyor 45, which is omitted from FIG. 1, is arranged alongside a mineral face 25 and a winning machine such as a plough can be moved along the conveyor 45 to detach the mineral from the face 25. Returning now to the assembly, the floor sill 10 carries a number of, in this case two, hydraulically operated telescopic props 12 arranged side-by-side, i.e., generally equi-distant from the conveyor 45. The props 12 carry, at their upper ends a goaf screen or shield 11 described in more detail hereinafter. The props 12 are each connected to the floor sill 10 and the goaf shield 11 with the aid of ball-and-

socket type joints

13, 14 respectively permitting a certain degree of angular mobility between these components. The props 12 are designed to cant into non-vertical positions as shown in FIG. 1. The lower end of the shield 11 is pivotably connected by means of a pivot pin 17 to the upper end of a support member 15 which effectively forms a continuation of the shield 11. The lower end of the support member 15 is similarly pivotably connected by means of a pivot pin 16 to the goaf end of the floor sill 10.

A double-acting piston and cylinder unit 18 is interposed between the floor sill 10 and the support member 15. The support member 15 has side walls 70 which effectively enclose and protect the unit 18. The sill 10 also has side plates 71 which lie within the side walls 70. The cylinder of the unit 18 is pivotably connected to a bracket 20 at the upper side of the floor sill 10 by means of a pivot pin 19 and the piston rod 21 of the unit 18 is pivotably connected tothe upper end part of the member 15 by means of a pivot pin 22. As can be appreciated by retraction or extension of the unit 18 the support member 15 can be pivoted about the pin 16 to bring the shield 11 towards or away from the mineral face 25. The props 12 can also tilt towards or away from the face to follow the movement of the shield 11.

At the forward end of the shield 11 nearest the face 25 there is provided a roof cap or girder 23. This girder 23 has depending brackets on its underside which serve to receive pivot pins 24 used to pivotably interconnect the girder 23 to the shield 11. The pins 24 are located so that their axes extend generally parallel to the face 25 and thereby form a fulcrum for the girder 23. The

portion of the girder 23 extending forwardly from the pins 24 is somewhat longer than the portion extending rearwardly thereof so that the girder 23 tends to swing about the pin in the direction of arrow 26. In order to limit the amount by which the girder 23 tilts in this manner, a cable 27 has one end 28 fixed to a lug at the underside of the rearwardly extending portion of the girder 23. This cable 27 extends through an aperture 29 in the shield 11 and is guided over a deflector 30 to extend within the shield 11. At the other end, the cable 27 passes over a further deflector 31 and is secured with its end 32 to the bracket 20. The

deflectors

30, 31 can take the form of shaped pieces of sheet metal or blocks or rollers or sheaves. Preferably some form of device, such as a toggle-screw or the like (not shown) is provided for adjusting the tension in the cable 27. In order to bring the girder 23 into contact with the roof of the working, and thereby to form an advance lining or support, the unit 18 is subjected to pressure medium so as to retract. The support member 15 then pivots about the pin 16 towards the face 25 whilst the props l2 tilt towards the face 25 as depicted in FIG. 1. The props 12, which can extend or retract to swing the shield 11 about the pin 17, would then be extended to cause the girder 23 to engage on the roof. When the girder 23 is set in this fashion the unit 18 is preferably locked hydraulically by sealing off its working chambers although it is advisable to provide pressure relief valves which open either of these chambers in the event of overloading. As the props 12 extend or retract the cable 27 moves to maintain the girder 23 in a more or less horizontal disposition. As shown in FIGS. 1 to 3, a double-acting shifting ram 35 is provided for effecting relative movement between the support assembly and the conveyor. This ram 35 is disposed centrally of the floor sill 10 and just above the latter. The ram 35 has its piston rod 36 pivotably connected to the bracket 20 by means of a pivot pin 37. The cylinder of the ram 35 is connected to a guide and coupling arrangement as will now be described. The cylinder is pivotably connected to a thrust member 39 by means of a pivot pin 38 which is received in elongate slots 41 in the two arms of a central fork portion 40 of the member 39. These slots 41 extend horizontally. At the centre of the member 39 there is a vertical pivot pin which connects with a coupling element 42. As shown in FIG. 2, this element 42 defines a shaped reception space which receives an upstanding limb of a T-shaped bar 44 affixed to the goaf side of the conveyor 45. The coupling element 42, which extends over the bar 44 in the manner of a claw, thus permits a sliding movement of the bar 44 in the longitudinal direction of the conveyor 45 whilst movement laterally of the conveyor 45 is limited. The provision of the vertical pivot pin interconnecting the member 39 to the coupling element 42 permits angular displacement of these components and it is designed that such angular movement does not exceed about 5 to 8. Each end of the thrust member 40 is coupled by means of a pivot pin 47 which extends parallel to the pin 38, to a resilient guide bar 46. The coupling is such that the pins 47 can be displaced vertically to a limited extent. Each guide bar 46 extends through

guide members

48, 49 attached to the floor sill 10. These

members

48, 49 which are spaced apart in a direction laterally of the conveyor 45 are each provided with an aperture through which the associated guide bar 46 extends.

The apertures in the members 48 have a somewhat greater vertical dimension that the apertures in the members 49 so that the bars 46 can move vertically by a greater distance in the members 48. The guide and

coupling arrangement

39, 42, 46, etc., permits the conveyor 45 to move vertically in relation to the floor sill I0 to an extent sufficient to cope with any unevenness in the floor. Assuming the props 12 are set so that the girder 23 is urged against the roof the ram 35 can be extended by the admission of pressure fluid so that initially the pin 38 slides within the slots 41 to engage the front ends thereof. Thereafter the force of the ram 35 will act through the member 40 and the element 42 to shift the associated sections(s) of the conveyor 45 towards the face 25 in the direction of arrow R in FIG. 3. In a complete working a number of support assemblies would be provided and normally the rams 35 would be operated successively to snake" the conveyor 45 towards the face 25. The shifting movement is controlled and guided by the gudie bars 46. Normally, as is known, the conveyor 45 would support and guide a winning machine such as a plough and as this machine is moved along the conveyor 45, the clearance provided by the slots 41 enables the conveyor 45 to move to a sufficient extend to provide for the so-called breathing of the conveyor 45.

When it is desired to shift the support assembly the props 12 are retracted and pressure fluid is fed to the ram 35 to effect retraction thereof. In this case the floor sill is induced to slide in the direction of the arrow R.

The construction of the shield 11 will now be described in more detail with reference to FIGS. 4 and 5.

As shown, the shield 11 has a main wall in the form of a hollow rectangular box-like structure and side walls, 50, 51 each of L-shaped configuration. Each

side wall

50, 51 has a portion 52 which overlaps the main wall and preferably is in sliding contact therewith. Each

side wall

50, 51 also has recesses 53 at its outer corner and these recesses 53 are intended to ensure that reactive forces are transmitted to the portions 52. At the inside of the main wall there is provided upper and lower guide blocks 54 and each block 54 is provided with an aperture which slidably receives a

rod

57, 63. The

rods

63, 57 associated with the upper guide blocks 54 are interconnected by means of a hydraulic piston and cylinder unit 55 and similarly the

rods

57, 63 associated with the lower guide blocks 54 are also interconnected by means of a hydraulic piston and cylinder unit 55. Each rod 57 has a head 58 at its outer end affixed to the associated side wall 50 and is articulated, as at 56, at its inner end to the cylinder of the associated unit 55. A helical compression spring 59 is arranged on each rod 57 and each spring 59 engages on the head 58 of the rod 57 at one end and the associated guide block 54 at the other end. The springs 59 thus act to bias the side wall 50 outwardly in the direction denoted by arrow s. Each rod 57 carries a stop member 60 in the form of a pin which can engage on the inner face of the associated guide block to determine the maximum distance by which the side wall 50 is urged outwards by the springs 59 or by the units 55.

associated guide block 54 at the other end. The sleeves 65 thus set the minimum distance between the side wall 51 and the adjacent guide blocks 54. Each rod 63 carries a stop member 66 in the form of a pin which can engage on the inner face of the associated guide block 54 to determine the maximum distance between the side wall 51 and the adjacent guide blocks 54. The sleeves 65 and locking members 66 serve to clamp the side wall 51 in position. Sleeves 65 of different lengths can be provided so that by interchanging these sleeves 65 the side wall 51 can be set at various position. In this case the rod 63 would have a series of bores spacedapart by distances commensurate with the difference in length of the sleeves 65 so that the stop member 66 can be re-positioned when the sleeve 65 is replaced by another sleeve 65. As shown in FIGS. 4 and 5 the lefthand side wall is displaceable whereas the righthand side wall 51 is essentially fixed. It can be appreciated that alternatively the sleeves 65 can be positioned on the rods 57 and the springs 59 positioned on the rods 63 so that in this case the left hand side wall 50 is fixed and the right-hand side wall 51 is movable.

As discussed a complete working would usually employ a number of support assemblies constructed as described. Where the floor of the working is inclined the rigid side wall (51 is depicted in FIGS. 4 and 5) is positioned on the side of the assembly which is uppermost in relation to the inclination of the floor and the displaceable side wall (50 as depicted in FIGS. 4 and 5) is disposed on the side of the assembly which is lowermost. The assemblies are then arranged so that the displaceable side wall 50 is supported against the fixed side wall 51 of an adjacent assembly or is closely adjacent thereto. In this way the side walls 50 of the assemblies can close the gaps between the shields ll of adjacent assemblies. The movement of the side walls 50 in the direction of arrow s is determined by the stroke of the units 55. An assembly which has slipped or tilted in view of the inclination of the floor can be re-aligned by removing the locking members 60 and subjecting the units to pressure fluid to effect extension thereof so that the side wall 50 of the assembly in question can then bear on the rigid side wall 51 of the next assembly. The engagement of the

side walls

50, 51 of adjacent assemblies can also provide alignment and guiding of the assemblies during shifting and this facility supplements the action'of the guide and

alignment arrangements

39, 42, 46, etc., at the lower part of the assemblies as described hereinbefore.

The units 55 can be provided with hydraulic means to effect locking thereof to effectively secure the movable side wall 50 in a desired position. It is also possible to provide pressure-sensitive devices so that the locking is effected when a certain pressure prevails on the side wall 50. Finally it should be mentioned that a pressure device can be coupled to one or both chambers of each unit 55 to provide a reactive pressure, in the manner of a controlled throttle for example, when the units 55 are retracted. This would then provide an analogous action to that of the springs 59 and these items can then be dispensed with.

We claim:

1. A mineral mining installation comprising:

a goaf shield composed-of a main wall and a pair of detachable 'L-shaped side walls, one of the side walls being disposed on one side of the main wall,

the other ofthe side walls being disposed on the opposite side of the main wall from said one side wall, each side wall having a portion overlapping the main wall, resilient guide means for permitting said one of the side walls to move laterally inwardly in relation to the main wall, means for permitting the other side wall to move laterally inwardly in relation to the main wall, means for selectively fixing the lateral position of the other side wall in relation to the main wall, and means for adjusting the distance between the side walls;

a floor sill;

at least one hydraulically operated telescopic prop operably disposed between the floor sill and the shield;

a support member pivotably connected to the floor sill and to the shield to effectively form a continuation of the shield; and,

means for displacing the support member relative to the floor sill to alter the position of the shield.

2. An installation according to claim 1, wherein the means for displacing the support member is a hydraulic piston and cylinder unit.

3. An installation according to claim 1, wherein said adjusting means is at least one hydraulic piston and cylinder unit.

4. An installation according to claim 1, wherein said resilient guide means is at least one spring operable to urge said one side wall laterally outwards relative to the main wall.

5. An installation according to claim 1, wherein each side wall of the shield is connected to a rod which is slidably guided through a guide block carried by the main wall, the rods connected to the side walls being interconnected through a hydraulic piston and cylinder unit operable to effect relative movement between the side walls and constituting said adjusting means.

6. An installation according to claim 1, wherein each side wall is connected to upper and lower rods, each rod being slidably guided through a guide block carried by the main wall, the upper rods connected to the side walls being interconnected through a first hydraulic piston and cylinder unit and the lower rods connected to the side walls being interconnected through a second hydraulic piston and cylinder unit, said first and second piston and cylinder unit constituting said adjusting means.

7. An installation according to claim 5, wherein each rod carries a detachable stop member engageable on a face of the associated guide block to limit the outward displacement of the side walls.

8. An installation according to claim 7, wherein a spring, constituting said resilient guide means is provided on the rod connected to said one side wall, said spring engaging on a further face of the associated guide block which is opposite the first-mentioned face thereof and serving to urge said one side wall outwardly.

9. An installation according to claim 8, wherein a sleeve is provided on the rod connected to the other of the side walls, said sleeve engaging on a further face of the associated guide block which is opposite the firstmentioned face, the sleeve and the stop member serving as the means for fixing said other side wall in position.

10. An installation according to claim 6, wherein each rod carries a detachable stop member engageable on a face of the associated guide block to limit the outward displacement of the side walls, a spring, constituting said guide resilient means is provided on each rod connected to said one side wall, said springs each engaging on a further face of the associated guide block which is opposite the first-mentioned face thereof so that said springs tend to urge said one side wall outwards, and a sleeve is provided on each rod connected to the other of the side walls, each of the sleeves engaging on a further face of the associated guide block which is opposite the first-mentioned face so that the sleeves and stop members serve as the means for fixing the other of the side walls in relation to the main wall.

1 1. An installation according to claim 1, wherein said support member has side walls and the side walls of the shield overlap the side walls of the support member.

12. An installation according to claim 11, wherein the floor sill has upstanding side wall plates and the side walls of the support member overlap the side walls of the support member.

13. An installation according to claim 1, wherein each side wall has a recessed portion at its corner.

14. An installation according to claim 1, wherein the shield carries a roof cap which serves, during use, to contact the roof of a mine working when said prop is extended.

15. An installation according to claim 1 and further comprising a thrust member, means for selectively connecting the thrust member to a longwall conveyor, a hydraulic ram operably connected between the floor sill and said thrust member and operable thereon during use to effect relative movement between the floor sill and the conveyor, and guiding and alignment means in the form of a plurality of guide bars and associated guide members, the guide bars being connected to the thrust member with the ram being disposed between the guide bars and the guide members being attached to the floor sill with the guide bars extending through the guide members.

16. An installation according to claim 15, wherein the guide bars are resilient.

17. An installation according to claim 15, wherein the guide members have apertures therein through which the guide bars extend, the apertures permitting vertical displacement of the guide bars in relation to the guide members.

18. An installation according to claim 17, wherein each guide bar extends through two guide members which are spaced apart in a direction extending along the longitudinal axis of the guide bar, the aperture in the guide member nearest the thrust member being of greater length than that of the other guide member so that the guide bar can move vertically in relation to the guide member nearest the thrust member by a greater amount than that in relation to the other guide member.

19. An installation according to claim 15, wherein the guide bars are pivotably connected to the thrust member in such manner as to permit a degree of vertical displacement between each guide bar and the thrust member.

20. An installation according to claim 15, wherein the thrust member has a central fork portion provided with slots extending generally in the longitudinal direction of the ram, the ram being connected to a pin which is slidably received within the slots of said fork portion.

21. An installation according to claim 15, wherein said connecting means comprises a coupling element for coupling to a bar at one side of the conveyor, the coupling element being pivotably connected to the thrust member so that the thrust member can be angularly displaced about a vertical axis in relation to the coupling element.

Claims

1. A mineral mining installation comprising: a goaf shield composed of a main wall and a pair of detachable L-shaped side walls, one of the side walls being disposed on one side of the main wall, the other of the side walls being disposed on the opposite side of the main wall from said one side wall, each side wall having a portion overlapping the main wall, resilient guide means for permitting said one of the side walls to move laterally inwardly in relation to the main wall, means for permitting the other side wall to move laterally inwardly in relation to the main wall, means for selectively fixing the lateral position of the other side wall in relation to the main wall, and means for adjusting the distance between the side walls; a floor sill; at least one hydraulically operated telescopic prop operably disposed between the floor sill and the shield; a support member pivotably connected to the floor sill and to the shield to effectively form a continuation of the shield; and, means for displacing the support member relative to the floor sill to alter the position of the shield.

9. An installation according to claim 8, wherein a sleeve is provided on the rod connected to the other of the side walls, said sleeve engaging on a further face of the associated guide block which is opposite the first-mentioned face, the sleeve and the stop member serving as the means for fixing said other side wall in position.

11. An installation according to claim 1, wherein said support member has side walls and the side walls of the shield overlap the side walls of the support member.