US3399927A - Self-advancing mine roof support including a protective mat for the roof - Google Patents

Description

Sept. 3. 1968 K. M. GROETSCHEL 3,399,927

SELF-ADVANCING MINE ROOF SUPPORT INCLUDTLNG A PROTECTIVE MAT FOR THE ROOF Filed April 21, 1966 7 Sheets-Sheet 1 Inventor: KourL mcurLa. Gvoeisckzel. P flttovnag 7 Sheets-Sheet 2 I lluhllul.

K. M. GROETSCHEL SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF Sept. 3, 1968 Filed April 21, 1966 Sept. 3, 1968 K. M. GROETSCHEL 3,399,927

SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF Filed April 21, 1966 7 Sheets-Sheet 3 5 .3 vw S S o \nvankon KavL maxi-q, GvoeiscizaL 3 gram 1;. Rate.

Sept. 3, 1968 K. M. GROETSCHEL 3,399,927

SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF Filed April 21, 1966 7 Sheets-Sheet 4 N l e I I no v on Q

N O I lnveMaov:

Sept. 3. 1968 K. M. GROETSCHEL 3,399,927

SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF 7 Sheets-Sheet 5 Filed April 21, 1966 l+ll|l lllllullllllllllnr Llulil.

QN QN n v I 1 I I l :1

P n n I I I I HH L H Sept. 3, 1968 K M. GROETSCHEL SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF Filed April 21, 966 7 Sheets-Sheet 6 m En Em 9% a a w n V V Gwm .m a Mr M S pt- 3, 1968 K. M. GROETSCHEL 3,399,927

SELF-ADVANCING MINE ROOF SUPPORT INCLUDING A PROTECTIVE MAT FOR THE ROOF Inventor: KowL ma -w. Gvoecsc\ l.

United States Patent ABSTRACT OF THE DISCLOSURE A flexible mat is stored and an extended portion is led off from the mat. The extended portion is supported in an elevated position adjacent to the roof and the elevated portion is held stationary while the stored portion is moved along a lower path to withdraw a further length of the-mat from the stored portion to increase the length of the extended portion. The extended portion of the mat is then provided with underpinnings at intervals along its length by a prop-supported superstructure.

This invention relates to a method of and apparatus for supporting the roof of an underground mine working.

The invention has been developed primarily in relation to the support of the roof-of an underground coal mine working of the form encountered when coal is mined by the method of long wall coal mining.

In this method a coal winning machine is traversed along a coal face and coal thus removed from the face is discharged or deflected on to a conveyor which extends along the coal face, and which includes a trackway along which the coal winning machine is moved under power.

The roof of themine working'extending over the top of the coal winning machine and in a direction away from the coal face andincludes the portion which is newly exposed as the coal winning machine cuts the coal away from the face, requires to be supported.

In many mine workings the condition of the strata im- I .mediately adjacent to the roof is such that falls of roof material cannot entirely be prevented by the installation of roof supports at intervals along the coal face. Falls of roof material mayoccur in between such supports and may cause injury to personnel and possibly damage to equipment operating in this region.

One of-the main objects of the present invention is to provide a new or improved method of supporting a roof and an apparatus for performing this method, whereby this problem will be overcome or reduced.

According to the invention a method of supporting the roof of an-underground mine working comprises stationing, beneath said roof, a flexible mat having a stored portion and an extended portion leading off from. said stored portion, supporting said extended portion at an elevated position adjacent to said roof, holding said elevated portion stationary while moving said stored portion along a path therebeneath to withdraw a further length of said mat from said stored portion and increasing the length of said extended portion, and underpinning said extended portion of said mat at intervals along its length by'prop supported superstructure.

' In a preferred manner of carrying outthis method where the roof to be supported is newly'exposed by the passage of a' winning machine along 'an upright face of the workingfsaid stored portion ofthe mat is disposed adjacent to saidwinni'ng machine and is moved in coordination therewith along said face, said extended portion is held in a position to underlie said newly exposed ice roof, and underpinning of said extended portion is effected by cantilever elements moved into a position beneath said extended portion, and supporting said elements by props offset rearwardly from said extended portion of said mat.

Further according to the invention I provide a roof supporting apparatus for supporting the roof of an underground mine working comprising the combination of mobile means for storing a portion of a flexible mat while permitting an extended portion of said mat to be led off from said stored portion, supporting means for maintaining said extended portion of said mat at an elevated position adjacent to said roof, and means for underpinning said extended portion of said mat at intervals along its length.

In a preferred form of such apparatus applicable primarily to use in the method of long wall mining, said mobile means comprise a substantially horizontal arm for carrying said stored portion of said mat in coiled form, and means for mounting said arm on a trackway for movement therealong, said supporting means comprises a roller element and a roller element support carried by said mounting means and serving to support said roller element for rotation about an axis parallel to said arm and at an elevated position adjacent to said roof, said means for underpinning said extended portion of said mat comprises a plurality of self-advancing roof supports each including a base, a plurality of power operated props thereon and a superstructure carried by said props, said superstructure having a rear part and a fore part of which the latter projects as a cantilever forwardly of said base, and traction means to advance said support to move said fore part beneath said extended portion of said mat.

The early underpinning of the extended portion of the mat is of importance. Supports heretofore available are not suitable for this purpose by reason of the fact that advancement of the fore part of the superstructure of such roof supports the mat being contingent upon being able to advance at least that part of the base which carries the prop for supporting the fore part of the superstructure.

Where the base is a single base element the whole of the base has to be advanced for this purpose, and this requires that the conveyor, normally situated adjacent the coal face, should be pushed towards the newly exposed coal face and the base then drawn up to the conveyor in its new position by the traction means, normally a hydraulic ram provided in the base. If the base comprises two base elements operatively connected by a traction means, such as a hydraulic ram, there must be suflicient space in front of the forward base element between this and the conveyor to permit of advancement of this base element. This again normally requires that the conveyor itself should be advanced towards the newly exposed coal face before any advancement of the forward base element can take place.

A further object of the present invention is to provide a new or improved form of self-advancing roof support which may be employed in the method of the invention or as part of the apparatus hereinbefore described to overcome or avoid this problem, but which may also be independently employed for supporting the roof especially where it is of importance to provide early support to a newly exposed roof even if no mat should be utilised.

With this object in view and from a further aspect the invention resides in the provision of a self-advancing roof support for supporting the roof of a mine working comprising a base, a plurality of power-operated extensible props mounted on said base, a roof engaging superstructure carried by said props at their upper ends, said superstructure including a rear part comprising laterally spaced longitudinally extending roof bars connected by laterally extending channel presenting an open end forwardly, said superstructure further including a fore part comprising an elongated beam having its rear portion disposed in said channel and its forward portion projecting forwardly beyond said base and supported by one of said props thereon, an auxiliary means for urging upwardly at least the portion of said beam situated forwardly of the supporting prop therefor, and traction means including a part operative at the level of said superstructure for advancing said beam relatively to said rear part of the superstructure.

The invention will now be described by way of example with reference to the accompanying drawings wherein:

FIGURE 1 is a view in side elevation showing one embodiment of apparatus in accordance with the invention for carrying out the method thereof.

FIGURE 1A is a fragmentary view in front elevation and partly in cross section illustrating one form of roller for supporting the mat at an elevated position adjacent to the roof.

FIGURE 1B is a view similar to FIGURE 1A showing an alternative construction.

FIGURE 2 is a plan view of the embodiment shown in FIGURE 1.

FIGURE 2A is a fragmentary plan view of an alternative structure of mat which may be employed.

FIGURE 3 is a fragmentary view in side elevation partly in vertical cross section illustrating a modification of the forward end portion of the beam which forms the fore part of the superstructure.

FIGURE 4 is a view in side elevation of one form of a second embodiment of self-advancing roof support which may be part of the apparatus shown in FIGURES 1 and 2 in substitution for the self-advancing roof support therein shown.

FIGURE 5 is a plan view of the second embodiment of the self-advancing roof support.

FIGURE 6 is a fragmentary view in end elevation and partly in cross section showing a modification of the guide means of FIGURES 4 and 5 operative between the rearward end of the beam which forms the fore part of the superstructure and the roof bars which form the rear part of the superstructure.

FIGURE 7 is a view corresponding to FIGURE 1 of a third embodiment of self-advancing roof support forming part of an apparatus for performing the method.

FIGURE 8 is a plan view of the embodiment shown in FIGURE 7.

FIGURE 9 is a view corresponding to FIGURE 1 of a fourth embodiment of self-advancing roof support forming part of an apparatus for performing the method of the invention.

FIGURES 10 and 11 are fragmentary views in side elevation and plan showing a modification of the fourth embodiment.

Referring to FIGURES 1 and 2 the apparatus thereshown is intended to be utilised for performing the method of supporting the roof in accordance with the invention in a mine working, for example a coal mine, in which the coal is extracted by the method of long wall coal mining.

In this method of coal mining coal is cut by a coal winning machine 10 having a cutter (not shown) to form an upright coal face 11, and the coal winning machine is traversed along a trackway 12 forming part of a conveyor 13 extending for the length of the coal face which may typically be 200 yards long. Movement of the coal winning machine 10 is effected by power operated means, for example endless driving chains extending along the trackway of a conveyor.

The coal winning machine normally includes or is associated with a deflector means or plough for deflecting coal cut from the face on to the deck plate 14 of the conveyor.

The portion of the roof newly exposed by passage of the coal winning machine is indicated at 15 and the apparatusrnow described provides support for this newly exposed portion of the roof on the trailing side of the coal winning machine.

For this purpose the apparatus comprises a means for storing a portion of a mat hereinafter described in more detail. Such means may comprise an arm in the form of a spindle 16 extending horizontally towards the coal face 11 from a mounting means in the form of gibs 17 projecting horizontally towards the trailing side of the coal winning machine 10. As shown, the gibs 17 are formed as integral extensions of a body part 25 mounted on the coal winning machine.

The spindle 16 may be of substantial diameter so that the coiled or stored portion of the mat can be supported directly thereon in a manner permitting of rotation of the coil on the spindle, or alternatively the coiled portion of the mat may be wound on to a drum which is rotatably supported on the spindle 16.

Although not illustrated the spindle 16 together with the drum or coil may be carried by the gibs 17 in such a manner as to permit of axial adjustment of the spindle to position the coil nearer to or further from the coal face 11 as desired.

As a possible alternative to providing a spindle on which a mat in coiled form is rotatable, the means for storing the mat could be in the form of a container. In this case the stored portion of the mat may be either in the form of a coil or the mat could be folded concertinawise in the container.

In any of the foregoing cases a portion of the mat adjacent to its free end can be led off from the coil or folded stored portion. The portion which is led off in this case is herein referred to as the extended portion of the mat. The coiled stored portion of the mat is indicated at 18 and the extended portion at 19 including the extended portions applied in preceding traverses. The extended portions applied in preceding traverses may be connected to each other by cables or other fastening means. The extended portion is maintained at an elevated position in contact with the roof by a support means comprising a roller 20 journalled for rotation about a horizontal axis on a spindle 21 which is, in turn, carried by a yoke 22 at the upper end of a post 23. The post 23 may be of rectangular cross section and may be vertically adjustable in a guide opening of corresponding cross sectional shape formed adjacent to the forward end of an arm 24 projecting forwardly from the body part 25 to which it is secured.

The roller 20 may be urged upwardly towards the roof by a leaf spring 26 projecting forwardly from a mounting block 27 on top of the body part 25 and secured thereto as a cantilever, the forward end of the spring being bifurcated to engage around the post 23 beneath the yoke 22.

The roller 20 can be mounted on the spindle 21 for free rotation thereon but is preferably subjected to a braking torque by means of a brake device. Such an arrangement is illustrated in FIGURE 1A wherein a brake device 28 is mounted on the spindle 21 so as to be held fast therewith, the spindle itself being held fast against rotation with respect to the yoke 22. The brake device has brake elements 29 movable radially bybrake operating mechanism into contact with inner surface of the roller 20. The brake operating mechanism may be mechanical, for example spring, screw or wedge mechanism, or it may be hydraulic and may be preset in any of these cases to provide predetermined braking torque.

The surface of the roller may be presented by a tire 30 of rubber or other suitable material providing a high coefiicient of friction with respect to the mat, such tire, if desired, being formed with a thread pattern.

Alternatively, as illustrated in FIGURE 1B, the outwardly presented surface of the roller 30 may be equipped with radially extending projections 31 for engaging in apertures presented by the mat. The spindle 21 may be adjustable axially-to vary the position of the roller 20 towards and away from the coal face.

The mat itself, as seen particularly in FIGURE 2, may be a mesh structure composed of elongated filamentary elements maintained in the desired positional relationship to each other by virtue of a woven relationship, that is to say each element passes alternatively above and below those whichextend transversely to it.

Alternatively all the parallel elements of one set may lie above or below the parallel elements of the other set, the elements contained in the two sets respectively being secured to each other at crossing points by fusion.

The elements themselves may be composed of wire, for example mild steel wire, but other materials may be employed if desired.

Although the roller 20 presents a continuous cylindrical surface in a direction axially of the roller, it will be understood that if desired such surface could bediscontinuous in the axial direction either by forming the roller with axially spaced radially projecting collar parts of greater diameter externally than the intervening parts of the roller, or by employing a plurality of separate axially spaced roller elements. In each case the collar parts or the roller elements may be equipped with a tire, as shown in FIGURE 1A, or radial projections as shown in FIGURE 1B, and subjected to the action of a braking device as shown inthese figures. I

An alternative form of mat which may be employed is shown in FIGURE 2A.

In this form the mat. comprises a plurality of longitudinally spaced parallel slat elements 32 which may be either wood or metal, such asmild steel, and longitudinally extending connecting elements 33 which may be cables, preferably stranded wire rope, connected to the slats at the positions at which these cross the cables in any suitable manner, for example, by clips, such as those illustrated at 34. Either of the constructions illustrated, namely the mesh structure shown in FIGURE 2 or the slat structure shown in FIGURE 2A, may be supplemented by the provision of a lining member forming a component of the mat. Such lining member may be formed of a Web of flexible material possibly of continuous, that is to say imperforate, form, for example a web of a woven textile fabric or a flexible synthetic resin. The lining member may be disposed either above or below the extended portion of the mat as desired.

If desired either form of mat may be supplemented by one or more longitudinally extending cables, in the latter case spaced apart laterally of the mat. Such cables may be interleaved with the mat when in its stored form so that they are unwound with the mat. Such cables may be disposed either above or below the extended portion of the mat.

The apparatus may further comprise a means'for applying a settable material to the extended portion of the mat after this has been applied against the roof. Such means may, for example, comprise a gun for spraying concrete or like cementitious material a bulk supply of which is carried in acontainer mounted at any convenient position on the body part 25. Such gun would preferably have .anoutlet or nozzle towards that part of the extended portion of the mat lying on the trailing side of the roller 29 so as to project concrete or cementitious material into such intersp'acebetween the mat'and the roof as may exist when the roof affords cavities or recesses. The concrete or cementitious material may also invest the mesh of the mat itself, the latter serving as a reinforcement to the concrete or cementitious material when the latter has set.

Preferably a quick setting concrete or ccmentitous material is employed, but other materials may also be utilised, for example a quick setting synthetic resin.

If desired the apparatus may incorporate a plurality of storage means, for example a plurality of spindles such as the spindle 16, the additional spindle or spindles being for example disposed parallel to the spindle 16 on the trailing side thereof and supported from extensions of the gibs 17 in a manner similar to the spindle 16.

This permits a corresponding number of mats to be stored, and permits two or more mats in superposed, that is to say fully overlapped, or partially overlapped relation to be applied against the roof by the roller 28 common to both such mats.

These mats, or certain of them may difler from the other or others in respect of their constructional or mechanical characteristics. Thus, for example, if all the mats are in the form of a mesh structure the aperture size of each mat may differ from that afforded bythe other or others. Alternatively, the cross sectional dimensions of the elongated elements of which the mesh is composed may differ for each mat in comparison with the other or others.

This allows a particular type of mat to be employed to suit given roof conditions and allows the numbers of mats applied in superposed or overlapped relation to be varied in accordance with roof conditions.

Whilst it is convenient to employ a single roller, such as 20 to apply on such mats more thanone such roller could be provided if desired.

Referring now to the form of self-advancing roof support illustrated in FIGURES l and 2, this comprises a base in the form of a single base element 35 including raised parts 36 and 37 adjacent to its rearward and forward ends, in the former of which are disposed two laterally spaced props 38 and in the latter of which is accommodated a single multi-section prop 39. These props are hydraulic props which can be extended by admission of hydraulic fluid to the chamber of the prop or each chamber in the case of the multi-section prop, such fluid being derived from a power-operated pump or possibly a manually or foot-operated pump.

Reference herein to power-operated props. is to be deemed to include manual or foot operation of the pump.

The multi-section prop 39 includes an inner prop unit 40 and an outer prop unit 41.

The outer prop unit 41 carries at its upper end a generally oval frame-like yoke, lateral extremities of which are provided with upwardly projecting posts 43 and carried on these posts and on the two rearward props 38 is the rear part of a superstructure indicated generally at 44.

The rear part of the superstructure is in the form of a frame including laterally spaced, longitudinally extending, roof bars 45. These roof bars may be either of single box section or, as illustrated, formed of two box section girders welded together along laterally projecting flanges which are continuations of their upper and lower horizontal webs. The roof bars 45 are connected at their rearward ends by a downwardly cranked cross member 46 also of box section and at their forward ends by a similar downwardly cranked box section cross member 47.

The superstructure further comprises a fore part' in the form of a long beam 48. This comprises laterally spaced roof bars 49 also of box section connected at intervals along their lengths by cross members 50, 51, 52. The long beam 48 has its rear portion disposed in the upwardly presented channel defined by the roof bars and cross members of the rear part of the superstructure, such channel being open at the forward end by virtue of the downwardly cranked form of the cross member 47, thereby allowing the forward portion of the long beam to project forwardly beyond the base element 35 and into a region above the coal winning machine.

The expression rear part as used herein means the part of the superstructure which is positioned to engage and support the roof in a rearward zone on the side of the conveyor remote from the coal face.

The long beam 48 is supported from the inner prop unit 40 of the multi-section prop 39 through the intermediary of a shoe 53 which engages the downwardly presented surface of a plate 54 welded or otherwise secured to the roof bars 49 of which the longer beam is formed. Such plate 54 is at onee nd connected to the cross member 51 and at the opposite end to an apertured block 55 through which extends the piston rod 56 of a double-acting hydraulic ram 58, the cylinder 57 whereof is pivotally connected to the cross member 52 about a horizantal axis transverse to the length of the long beam. The stroke of the rams 58 and 59 may be equal to each other and correspond to the advancement stop to be made for each traverse of the coal winning machine. The ram 58 may have an effective diameter less than that of the inner prop unit 40. The setting load exerted by the latter would then be decreased during advancement of the long beam member by the ram 58. Alternatively the effective diameter of the ram 58 may be increased if necessary beyond that of prop unit 40 to permit of advancement of beam 48 under a full value of setting load exerted by prop unit 40.

The double-acting hydraulic ram 58 forms the upper part of traction means, the lower part of which comprises a pair of double-acting hydraulic rams mounted in the base element 35, one of these being seen at 59 and having its piston rod 60 provided with a forked termination for pivotal connection at 61 to a bracket on the trackway 12 of the conveyor 13.

At its rearward end the long beam 48 is provided with a box section member 62 of internal dimensions to receive the rear end portion of the long beam. Such box section member has laterally projecting arms 63 and its side walls are formed with horizontal, longitudinally extending, slots 64 in which engage a horizontally transverse pin 65 secured to, and projecting laterally from, the long beam. The member 64 can thus slide relatively to the long beam between limits determined by engagement between the pins 65 and the ends of the slots 64. The internal dimensions of the member 64 are such that there is little or no free lateral or upward and downward movement between this member and the long beam but sliding movement can take place easily.

The member 22 can be moved slidably relatively to the long beam by means of a double-acting hydraulic ram 66 the piston rod 68 of which is pivotally connected to a medial lug 67 projecting downwardly from the top wall of the member 22 and the cylinder 69 whereof is pivotally connected about a horizontal axis to the cross member 51. Initially the member 22 may be held back by frictional engagement with the roof during advancement of the long beam 48 and thereafter drawn forwardly of the ram 66.

The arms 63 of the member 62 are equipped, adjacent to their outer ends, with relatively short hydraulic piston and cylinder units 70, the cylinders whereof are secured to the arms at their undersides and the piston rods or plungers whereof, as indicated at 71, project upwardly through the apertures in the arms 63 to engage contact surfaces presented downwardly at the undersides of the roof bars 45. The units 70 may be connected hydraulically with the ram 58, so as to enable the rearward end of the beam to be depressed automatically during its advancement by the ram 58 and thereby increase the support applied in the forward zone of the roof.

Forwardly of the inner prop unit 40 and associated shoe 53, the long beam 48 is further supported by a carrier means underlying the long beam in the form of a cross member 72 having an upwardly presented face engaging contact faces at the undersides of the two roof bars 49 and itself carried by cantilever arms 73 secured to the cross member 33 and to a downward connection 74 at the forward end of each roof bar 45 of the rear part of the superstructure. The cantilever arms 73 are preferably formed as leaf springs of a material such as spring steel and with the parts in the position shown in FIGURE 1 are stressed so that the cross member 72 exerts an upthrust or preload against the underside of the long beam 48.

In utilising the apparatus to carry out the method of roof support, the coal winning machine will be disposed initially at one end of the trackway 12 of the conveyor 13. The extended portion 19 of the mat is passed above the roller 20 and is suitably secured to an anchorage adjacent the roof, for example by being clamped thereagainst by the long beam 48 of the self-advancing roof support situated on the trailing side of the coal Winning machine.

As the coal winning machine moves along the coal face by the power-operated driving means provided on the conveyor 13, coal is cut from the coal face and a portion of the roof is newly exposed as indicated at 15.

The mat is unwound from the stored portion on the spindle 16 and, due to the operation of the brake device 28 acting on the roller 20, the mat is not only applied against the roof by the roller 20 but is maintained in a state of tension so that it lies closely against the roof and does not sag.

If a gun for applying settable material is provided such gun is operated continuously to apply the settable material, as already referred to, to form a filling for any cavities in the roof above the mat and to invest the mat itself.

As soon as the roller 20 has passed each selfadvancing roof support the long beam of the latter is advanced by appropriate pressurisation by hydraulic fluid of the ram 58 to extend the ram into the position shown in FIGURE 1 in full lines. The initial non-advanced position of the long beam is indicated in FIGURE 1 in chain lines.

During such advancement the inner prop unit 40 may be depressurised partly or wholly and upthrust applied to the long beam is then derived from the cross member 72 and springs 73. Further upthrust may be derived by pressurisation of the piston and cylinder units 70, the plungers of which, when extended, depress the rearward end of the long beam and cause the forward end to tilt upwardly about a transverse horizontal axis defined by engagement between the shoe 53 and the head of the inner prop unit 40.

This arrangement permits selected preload to be exerted against the underside of the mat by the long beam during sliding engagement of the latter and moving into a position in which it underpins the mat. When it has been moved into its advanced position, as shown in FIGURE 1, the long beam can be repressurised to the full seating value.

When the coal winning machine and apparatus carried thereby has moved sufliciently far beyond the self-advancing roof support to permit advancement of the conveyor 13, the latter being composed of articulately connected selections to be snaked or displaced towards the newly exposed coal face, this is effected by pressurisation of the rams 59 to extend their piston rods.

Subsequently the outer prop unit 41 and the rear props 38 are pressurised and the rear part of the superstructure lowered and the rams 59 again pressurised to draw the base and rear part of its support up to the new position of the conveyor section concerned preparatory to repressurising these props and the outer prop unit.

If desired long beam 48 may be equipped with an extension piece 75 preferably of T shape in plan having its narrower stem portion 76 between the roof bars 49 and resting on the upper edge face of the cross member 53. The plate 75 may be supported by leaf spring assemblies 77 engaged slidably in the interiors of the roof bars 49. The plate 75 can be used for supporting part of the roof exposed by a scarped fall of material from the face as shown in chain lines in FIGURE 1.

The plate 75 may be advanced manually if desired. Hydraulic rams may be provided in the interiors of the roof bars 49 and the piston rods 79 being connected to the rearward ends of the leaf springs 77. These rams may be single-acting to produce extensions which are returned subsequently when the long beam as a whole is advanced. Alternatively, double-acting rams may be utilised.

In the modification illustrated in FIGURE'3 the trac- 9 tion ram 58 is replaced by an adjustable length strut 80 having telescopically assembled components 81 and 82 capable of being secured in any of a plurality of relative positions varying the effective length of the strut, asfor example by the provision of holes 83 in one of these components, and a cross pin insertable through any of the selected holes 83, and an aligned hole in the component 81. In this case advancement of the long'beam tounderpin the mat would be deferred until the coal winning machine had moved beyond the self-advancing roof support sufficiently to permit the adjacent conveyor section to be displaced or snaked towards the coal face and the support as a whole to be drawn up after depressurisation of both the multisection prop 39 and the rearward props 38, support being then furnished by the cross member 72 and spring 73 acting on the underside of the long beam and by any selected pressurisation of the piston and cylinder units 70. i A plate 84may be mounted for universal pivotal movement at the forward end of the long beam to provide for application of preload to a selected roof area corresponding to that of the plate 84 while the beam itself bears hollow with respect to the roof. In the hollow bearing Zone forepoling arm may provide support as described with reference to FIGURES 4 and 5. Instead of providing the plate 85 the beam 48 may be curved upwardly adjacent to its forward end. In the construction of self-advancing roof supports illustrated in FIGURES 4, and 6 arts corresponding to those already described in the self-advancing roof support illustrated in FIGURES 1 and 2 are designated by like numerals with the prefix 1 and the preceding description is deemed to be applicable thereto. Reference, therefore, willbe made only to the modified features of construction. I 5 In this form of roof support the cross member 172, instead of being supported by spring arms, is supported by a strut member 185. The strut member is preferably of telescopic form including an outer element 186 pivotally connected to a bracket 187 on the base element 135 and an inner element 188 pivotally connected to a bracket at the underside of the cross member 172. A clamping device in the form of a screw 189 operating through a collar 190 at the upper end of the element 186 bears directly through the intermediary of a shoe against the inner element 188 to secure it against sliding movement. The inner element may be a hydraulic ram or it may be a rigid inextensible part such as a tubular member.

The outer element may comprise a leaf springassembly providing for yieldable lateral movement of the inner element.

Forward movement of the cross member 172 during advancement of the long beam 148 is prevented by tie members 191 which may be in the form of rods or a cable-secured to the cross member 172 and passing round the inner prop unit 140 or otherwise secured to the rear part of the superstructure; v

,The cross member itself 172 is provided at its lateral extremities with upwardly projecting lugs 191 which .present inwardly facing guide surfaces contactingthe outer sides of the long beam.

At its rearward end the long beam 148 is guided laterally in the channel afforded between the roof bars 145 of the rear part of the superstructure by means of laterally projecting guide elements 192. These comprise plungers contained in openings formed in the rearward end portions of theroof bars 149 and urged outwardly *by a coiled compression spring 193 disposed between the inner ends of the plungers and supported by an apertl lred-bracket 194. Alternatively as shown in'FIG- The plunger or plungers maintain the rearward end of the long beam in a selected lateral position in the channel and prevent any, or any excessive, lateral deflection thereof when the roof support is used in mine workings in which the floor and roof slope in the direction longitudinally of the coal face. The heads of the plunger or plungers contact inwardly presented side faces of the roof bars 145. These faces are bounded at the top and bottom by flanges which limit vertical movement of the plunger heads and hence vertical movement of the rear end of the beam. They are deep enough however to provide the requisite degree of vertical movement for maintaining contact and upward preload between the forward end of the beam and the mat or roof. As a further alternative the plungers or the single plunger may be operated by hydraulic piston and cylinder units.

The rear part of the superstructure is further provided in this construction with forepoling arms 195 pivotally connected about horizontal axes to the enlargements 174 of the roof bars 145 of the rear part of the superstructure and raised and lowered by wedge mechanisms oper ated by a hydraulically energised piston and cylinder unit (omitted for the sake of clarity from the drawings).

At its rearward end the long beam is further supported by an auxiliary prop 196 which is suspended from the rearward end of the long beam during advancement of the latter, as disclosed in my co-pending application No. 511,511 to which reference may be had for further particulars. The base element is slotted to accommodate the lower end of this prop and a separate floorengaging element 197 therefor.

In the construction of self-advancing roof support illustrated in FIGURES 7 and 8 parts corresponding to those already described are designated by like numerals of reference with the prefix 2 and the preceding description is to be deemed to be applicable thereto. Reference, therefore, will be made only to the modified features of construction.

In this form of self-advancing roof support the base comprises separate rearward and forward base elements 235a, 235b, the former supporting the two rearward props 238 and the outer prop section 241 of the multisection prop, the inner prop unit 240 whereof is removed and accommodated in the forward base element 235. A forward extension of the enlargement 274 engages the rearward side of the inner prop unit to stabilize this against rearward deflection during advancement of the long beam 248 by ram 258. The inner prop unit 24 may advantageously be provided with a booster device comprising a short piston and cylinder unit of larger effective diameter than the inner prop unit and having a hollow piston in which the lower end of this unit is received as shown.

The traction rams 259 in the base element 235 serve to connect this with the forward base element 235b.

Auxiliary preload in the long beam, at a position forwardly of the inner prop unit 240, is provided by a cross member 272 supported by cantilever arms 273 each composed of a plurality of leaf springs.

A single piston and cylinder unit 270 is provided adjacent to the rearward end of the long beam, the cylinder of such unit being secured between the roof bars 249 of the long beam 248 and the plunger extending downwardly and being connected centrally to the laterally projecting arms 263, the outer end portions of which operate in guideways 263a defined between the roof bars 245 at the rear part of the superstructure and guide brackets 245a secured to the undersides of the latter in downwardly spaced relation thereto.

Referring now to the embodiment of self-advancing roof support shown in FIGURE 9, parts corresponding to those already described are designated by like numerals of reference with the prefix 3, and the preceding description is to be deemed to be applicable thereto. Reference,

therefore, will be made only to the modified features of construction.

In this construction support for the long beam 348 forwardly of the inner prop unit 340 is provided by a cross member 372 underlying the main beam and carried by a pair of rigid arms 398 piv-otally connected at 399 at their rearward ends to the rear part of the superstructure. These arms are themselves further supported by strut members 400 preferably in the form of hydraulic rams extending downwardly and rearwardly from points of pivotal connection 401 to the arms, and pivotally connected at their lower ends to brackets 402 on the rear base element 335a. If desired further support to the cross member 372 may be provided by a laminated leaf spring assembly 373 secured as a cantilever to the enlargement 372 at the forward end of each roof bar 345 of the rear part of the superstructure.

Alternatively the strut members 400 can each comprise the combination of hydraulic rams and support elements such as the leaf spring assembly 186 shown in FIGURE 4.

FIGURES 10 and 11 illustrate a modification of the self-advancing roof support of FIGURES 7 and 8 which may be made to incorporate supporting structure for the cross member underlying the long beam similar to that provided in the embodiment of FIGURES 4 and 5.

Parts corresponding to those already described are designated by like numerals of reference with the prefix 5 and the preceding description is to be deemed to be applied thereto.

In this construction the carrier means instead of comprising a single cross member comprises separate shoes 572a and 572k anchored against forward movement by rods or cables 590 and supported by telescopic struts 585. Such struts have clamping mechanism 589 for retaining the outer element 586 and the inner element 588 in any selected position of adjustment.

In operating the supports illustrated in FIGURES 7 to 10 the long beam is advanced under preload to underpin the mat while both base elements remain stationary. The forward base element and the inner prop unit carried thereby is then advanced with the latter partly or wholly depressurised. The hydraulic rams incorporated in the struts 400 may be pressurised as may also the piston and cylinder unit 270 to cause the forward end of the beam to exert preload against the roof at this stage. The inner prop unit is then again pressurised up to its full setting load value. The prop units supporting the rear part of the superstructure are then depressurised and the rear base element drawn forwardly by the rams provided thereon, preparatory to re-pressurising these prop units to their full setting loads.

In any of the foregoing constructions piston and cylinder units 70, and 270 may be used to assist or accelerate lowering of the rear part of the superstructure to reduce the overall time for a complete sequence of operation.

What I claim then is:

1. A method of supporting the roof of an underground mine working comprising:

(A) stationing, beneath said roof, a flexible mat having a stored portion and an extended portion leading off from sard stored portion,

(B) supporting said extended portion at an elevated position adjacent to said roof,

(C) holding said elevated portion stationary while moving said stored portion along a path therebeneath to withdraw a further length of said mat from said stored portion and increase the length of said extended portion, and

(D) underpinning said extended portion of said mat at intervals along its length by prop supported superstructure.

2. A method according to claim 1 wherein:

(A) the roof to be supported is newly exposed by passage of a winning machine along an upright face,

(B) said stored portion of said mat is disposed adjacent to said winning machine and is moved in coordination therewith along said face,

(C) said extended portion is held in a position to underlie said newly exposed roof, and

(D) underpinning of said extended portion is etfected by moving cantilever elements into a piston beneath said extended portion and supporting said elements by props offset rearwardly from said extended portion of said mat.

3. A method according to claim 2 further comprising the step of urging said cantilever elements in an upward direction yieldably against the underside of said extended portion of said mat while advancing said elements from a position ofiset rearwardly from said mat to a position therebeneath.

4. A method according to claim 1 wherein said extended portion of said mat held at an elevated position adjacent to said roof is subject to tension in a direction longitudinally of said path of movement of said stored portion.

5. A method according to claim 4 wherein:

(A) said extended portion of said mat is held in its elevated position and the tension in said extended portion is established by engaging said extended portion at its underside with a roller element,

(B) urging said roller element upwardly to bring said extended portion into contact with the roof and,

(C) moving said roller element bodily with said stored portion of said mat along said face while applying a braking torque to said roller element.

6. A method according to claim 1 wherein:

(A) a plurality of said flexible mats are stationed beneath said roof,

(B) two at least of said mats differ in respect of their physical characteristics,

(C) two at least of said mats are applied against said roof in at least partly overlapped relation with each other.

7. A method according to claim 1 further comprising the step of applying a settable filling material in flowable form between said extended portion of said mat and said roof.

8. A method according to claim 1 further comprising the steps of:

(A) effecting said movement of said stored portion in a plurality of traverses extending generally parallel to each other in side-by-side relation to effect application to the roof of a corresponding number of lengths of the extended portion of said mat in like relation,

(B) connecting each of said lengths of extended portion of said mat at least to the lengths adjacent thereto.

9. A roof supporting apparatus for supporting the roof of an underground mine working comprising the combination of:

(A) mobile means for storing a portion of flexible mat while permitting an extended portion to be led off from said stored portion,

(B) supporting means for maintaining said extended portion at an elevated position adjacent to said roof, and

(C) means for underpinning said extended portion at intervals along its length.

10. Apparatus according to claim 9 wherein:

(A) said mobile means comprise a substantially horizontal arm for carrying said stored portion of said mat in coiled form and means for mounting said arm on a trackway for movement therealong,

(B) said supporting means comprise a roller element and a roller element support carried by said mounting means and serving to support said roller element for rotation about an axis parallel to said arm and at an elevated position adjacent to said roof,

(C) said means for underpinning said extended por- 13 tion of said mat comprises a plurality of self-advancing roof supports each including a base, a plurality of power operated props thereon, and a superstructure carried by said props, said superstructure having a rear part and a fore part of which the latter projects as a cantilever forwardly of said base and traction means to advance said support to move said fore part beneath said extended portion of said (B) said supporting means for maintaining said extended portion of said mat at an elevated position is disposed in trailing relation to said cuter element to enable it to apply said extended portion of said mat.

11. Apparatus according to claim 9 wherein said mat 10 comprises a mesh structure composed of elongated elements.

12. Apparatus according to claim 9 wherein said mat comprises a succession of slat elements extending paralmat progressively to the newly exposed portion of the roof as same is exposed.

References Cited UNITED STATES PATENTS lel to each other and spaced apart longitudinally of the 1 31O7902 10/1963 Calder 299-11 mat and extending transversely thereof, and connecting FOREIGN PATENTS elements disposed at least adjacent to opposite lateral 810,151 8/1951 Germany boundaries of the mat and connecting successive ones of 714,992 9/1954 Great Britain said slat ClQIIlClltS 110 each other. 90 329 2 19 2 Great Britain.

13. Apparatus according to claim 9 wherein: 20 44,600 11/1961 Poland.

(A) said mobile means is operatively connected with a winning machine for movement along a trackway ERNEST R. PURSER, Primary Examiner. therewith, 'said trackway extending along an upright

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