US3872678A

US3872678A - Mine roof supports

Info

Publication number: US3872678A
Application number: US377305A
Authority: US
Inventors: Peter Shuttleworth
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-07-14
Filing date: 1973-07-09
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25
Also published as: AU5782673A; GB1408429A; CA995908A

Abstract

A mine roof support comprising, in combination, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, hingedly connected to the rigid canopy so as to be angularly adjustable relative thereto and a lever arm pivotally supported by said rigid canopy and serving to locate and support the canopy extension relative to said rigid canopy.

Description

United States Patent .1191

Shuttleworth Mar. 25, 1975 MINE ROOF SUPPORTS 3.686.874 8/1972 Bell 61/45 1) [76] Inventor: Peter Shuttleworth, The Paddock, FOREIGN PATENTS OR APPLICATIONS Eastgmei Hornsear Yorksh're 1.146.464 4 1963 Germany 61/45 1) land 1.547.489 lO/l9o8 France.. (31/45 I) [22] Filed: y 9, 1973 1.233.188 /1972 United Kingdom .i 61/45 D PP NOJ 377,305 Primary Examiner-Dennis L. Taylor Attorney. Agent. or Firm-Diller. Brown. Ramik & Foreign Application Priority Data wlght July 14, 1972 United Kingdom 1. 33001/72 M [57] ABSTRACT [52] US. Cl 61/45 D A ine roof support omprising, in combination. a [51] Int. Cl. E2111 15/44 base, a rigid anopy hydraulic props between said 1 Field Of Search 61/45 base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base. a canl l References Cited opy extension, hingedly connected to the rigid canopy UNITED STATES PATENTS so as to be angularly adjustable relative thereto and a 3,113,661 12/1963 Linke et 61/45 1) x lever arm Pivotally Supported y Said rigid py and 3.328.967 7 1967 Wilkenloh 61/45 D ng t locate and support the canopy extension 3.490.243 1/1970 Groetsche1.... 61/45 D relative to said rigid canopy. 3.5l2,364 5/1970 Holland 61/45 D 9 D F, 3.534.559 10/1970 Seddon et a1. 61/45 D 22 Clams rawmg 2 a 2 2.2 i 370 g 5 li i o 1 39 L0 r\ op h fi' 56 I ,3 28C L6 u 5 1 i l 6a 111 i 15 1. l i 1 i :3; 1 1 1 |1 l3 1 l I 1 f. ,L I

1, 1 ii I 2 I f H $1 1 [f I E '1, 1G 7 7 .1

r 1 I l I r I {a :11 31/ l 23 ifl I11;

r 220 l! 0 1M PATENTED HARE 5

IQTS SHEET

1 or 7 MINE ROOF SUPPORTS This invention concerns mine roof supports and has particular application to self advancing mine roof supports.

In one known self advancing mine roof support for long wall mining a rigid roof-canopy is supported above a sledge base by a plurality of substantially vertical hydraulic props and the height of the roof canopy above the base can be varied by adjusting the supply of hydraulic fluid to the props. A double acting piston and cylinder arrangement is disposed in a longitudinal recess in the sledge base with the cylinder mounted for retention with the sledge base and the ram extendable forwardly from the cylinder. A relay bar is connected to the outer end of the ram.

ln long wall mining operations a plurality of self advancing mine roof supports are arranged in side by side relationship and the relay bars of all the self advancing mine roof supports are connected to a conveyor which extends from end to end of the assembly of supports parallel with the coal face being worked. When all the supports are set against the roof, the conveyor can be advanced forwardly of the assembly of supports by extending the rams of all the double acting ram and cylinder arrangements in the support bases. When the rams have been fully extended each support is individually advanced up to the conveyor by lowering the roof canopy of the support, reversing the flow of hydraulic fluid to the double acting ram and cylinder arrangement to drag the mine roof support towards the conveyor and extending the hydraulic props until the canopy is again set against the roof. When all the supports have been advanced the conveyor can again be displaced relative to the assembly of supports.

Mining equipment ofthe type described above is generally used in combination with a face cutting machine which travels along the mine face forward of the conveyor and the face cutting machine is guided from end to end of the face being worked by the conveyor. As the face cutting machine travels backwards and forwards along the face being worked the cut material is conveyed by the conveyor towards one end of the array of mine roof supports for conveyance, by other means, away from the mining area.

It will be appreciated that in the mining arrangement described above the rigid roof canopy provides protection against roof falls above the base and,- in some cases, it has been proposed to extend the rigid canopy forwardly of the base to support the roof in that area.

In another method of mining a plurality of self advancing mine roof supports are arranged in side by side relationship with the coal face to be worked forward of the supports. A continuous miner travels along the length of the coal face, cutting a face substantially at right angles to the length ofthe coal face, and the continuous miner discharges the cut coal into shuttle cars which travel backwards and forwards along the roadway cut by the miner. The entry to the face could be curved to facilitate movement of the continuous miner and shuttle cars. l

The mine roof supports are provided to support the roof above the roadway cut by the continuous miner and as such roadways are often in the region of 9' and 6 In both the above methods of mining different working conditions required on different faces, or different conditions on the same face due to variations in the material being mined can require different lengths of roof canopy and, with a continuous rigid canopy providing an overhang forward of the base, a change of canopy length requires a change of the complete canopy and in practice this is a relatively long, awkward, and dangerous operation.

Further as the mine roof is very seldom flat and level, the newly cut roofcan include areas ofdifferent density and irregularities due to the fall of loose material from the roof, long, rigid canopies affording a substantially flat and continuous upper surface can be subjected to greatly differing forces over said upper surface and thus to avoid distortion of the canopy substantial reinforcement of the canopy is necessary and such reinforcement makes the roof canopy heavier and more difficult to manipulate.

An object of the present invention is to provide a mine roof support including a rigid canopy and a canopy extension arranged to be displaceable relative to the rigid canopy.

According to the present invention there is provided a mine roof support comprising a base, a rigid canopy supported on hydraulic props above the base, and a canopy extension hingedly connected to the rigid canopy and angularly adjustable relative thereto by a lower arm pivotally supported by the rigid canopy.

Preferably the lever arm comprises a double arm lever having one arm extending from the rigid canopy to afford support for the canopy extension and an arm extending substantially inwardly relative to the rigid canopy and engaged by a lever arm locating means.

Preferably the lever arm locating means comprises a piston and cylinder arrangement acting between the inner arm of the lever arm and the rigid canopy. By expanding the piston and cylinder arrangement the lever arm can be rotated in one direction to elevate the canopy extension and, by contracting the piston and cylinder arrangement the canopy extension can be lowered.

In one preferred embodiment in accordance with the present invention the canopy extension comprises two spaced parallel beams independently pivotally con-' nected to the rigid canopy by a common pivot pin. The lever arm is pivotally supported on the common pivot pin between the two spaced parallel beams and the outwardly extending arm of the lever arm carries a cross link engaged with and supporting the parallel beams.

In one construction for the embodiment described above the cross link is rigidly connected to the lever arm whereby the two beams are displaced in unison by the lever arm. In another form of construction for the embodiment the cross link is pivotally supported on the lever arm to permit alimited degree of independent pivotal displacement between the parallel beams.

Preferably each beam includes a stop plate, conveniently a leaf spring, secured thereto and engageable with the rigid canopy to support the beam in a lowest position for the beam relative to the canopy. Conveniently this lowermost position of the beams is attained before the piston and cylinder arrangement defining the lever arm locating means is fully retracted.

According to a further feature of the present invention the canopy extension includes at least one extendable roof support and, conveniently, when the canopy extension comprises two parallel beams, each beam includes an extendable roof support.

Preferably the beams are of hollow rectangular section in which case an extendable roof support is slidably disposed in each beam and each extendable roof support is slidably displaceable outwardly of its beam housing to afford support for a roof forward of the beam.

The extendable roof support may be freely slidable in its supporting beam, whereby said extendable roof support may be manually pushed out or retracted by an operator standing beneath the rigid canopy and engaging the extendable roof support with a hook ended pole.

Alternatively each extendable roof support may be slidably located relative to its supporting beam by a hydraulic piston and cylinder arrangement.

According to another aspect of the present invention there is provided a piston and cylinder arrangement, for connection between a mine roof support and a rear chock said piston and cylinder arrangement having one end adapted for pivotal connection to the rear chock and hydraulic means attached to the piston and cylinder arrangement and arranged to act between said piston and cylinder arrangement and the rear chock to effect pivotal displacement of the piston and cylinder arrangement about the pivotal connection relative to the rear chock.

Preferably the piston and cylinder arrangement includes a steering beam which presents arms extending from each side of the arrangement, and each arm supports a hydraulic jack engageable with the rear chock. Conveniently each arm supports the cylinder of its associated hydraulic jack so that the rams of said jacks are displaceable parallel to the longitudinal axis of the piston and cylinder arrangement.

In one embodiment in accordance with this aspect of the present invention the piston cylinder is adapted for connection between the mine roof support and the rear chock with the pivotal connection provided on the free end of the piston rod for connection to the rear chock. The cylinder is supported by the mine roof support and restrained against transverse displacement relative thereto.

A steering bar is secured on the pivotal end of the piston rod and presents an arm extending transversely at each side of the piston rod. A hydraulic jack cylinder is supported near the outer end of each arm and the jack rams are engageable with strong points on the chock.

Conveniently, the free end of the piston rod is rigidly secured to a relay bar which includes the means for making the pivotal connection with the rear chock and includes the arms forming the steering bar.

The invention will now be described further by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows a longitudinal centre line section through a mine roof support in accordance with the invention,

FIG. 2 shows a perspective view of the roof support shown in FIG. 1,

FIG. 3 shows a vertical transverse section through the mine roof support on the line Il-II of FIG. 1,

FIG. 4 shows a side elevation of a mine roof support according to the invention adapted for working with a rear chock,

FIG. 5 is a plan view of the assembly shown in FIG. 4,

FIG. 6 shows a plan view of the assembly shown in FIG. 4 with the canopy removed,

FIG. 7 shows a perspective view of a canopy extension including manually displaceable extendable roof supports FIG. 8 shows a side view of a canopy extension with hydraulically actuated extendable roof supports, and

FIG. 9 shows a schematic plan view of a steering arrangement for a mine roof support and rear chock arrangement.

The self advancing mine roof support illustrated in FIGS. 1 and 2 comprises a sledge base, generally indicated by reference numeral 11, a rigid canopy 12 supported above the sledge base 11 by four hydraulic props 13, l4, l5 and 16 and a canopy extension, generally indicated by reference numeral 17, hingedly attached to the canopy 12.

The sledge base 11 comprises two substantially parallel sledge-

like members

20 and 21 rigidly connected by front and rear bridging parts. The rear bridging part comprises inner and outer bridging parts 220 and 22b respectively which afford support for the lower parts of the rear hydraulic props 13 and 14 a forward bridging part 23 which provides support for the two forward props and 16.

A double acting piston and cylinder arrangement. comprising a cylinder 24, a piston (not shown) and a piston rod 25, is located between the sledge-like mem bers and 21 with the cylinder 24 connected to the base 11 and the piston rod 25 extending forwardly from the cylinder 24 for connection through a relay bar 26 to a coal face conveyor (not shown).

The

hydraulic props

13, 14, 15 and 16 extend upwardly from the base 11 to support the rigid canopy 12 on their upper ends. The rigid canopy 12 comprises top and

bottom plates

27 and 28 respectively connected by front and

rear channels

29 and 30 respectively and

side walls

31 and 32. Prop bearing blocks, such as the blocks 33 shown in FIG. 1, are located within the rigid canopy between top and

bottom plates

27 and 28 and each block 33 has a downwardly opening spherical recess 34 into which the upper end of its

respective prop

13, 14, 15 or 16 is seated and located thereby.

Extensions to the

side walls

31 and 32 of the canopy 12 extend forwardly beyond the front wall 29 and are bored to receive and support a shaft 35. The canopy extension 17, comprising two

beams

36 and 37, are pivotally supported on the shaft 35 in spaced parallel relationship to be pivotable relative to the rigid canopy 12 and, in the embodiment illustrated in FIGS. 1, 2 and 3 the two

canopy beams

36 and 37 are independently pivotable on the shaft 35.

The shaft 35 also pivotally supports a double arm lever 38 between the

beams

36 and 37 and the lever 38 presents a forwardly extending arm 39 which rotatably supports a cross link plate 40 having

lobes

41 and 42 which engage respectively beneath

webs

36a and 37a of the canopy beams 36 and 37 respectively to support said

beams

36 and 37. The rear arm 43 of the double arm lever 38 extends downwardly and rearwardly from the shaft 35 and is pivotally attached to a lever arm locating means, generally indicated by reference numeral 44.

The cross link plate 40 is, as will be seen from FIG. 3, mounted on a shaft 390 extending forwardly from arm 39, the shaft 39a passes through a bore 40a in the cross link plate 40, and a key 39b projecting from the underside of the shaft 39a, engages in an arcuate enlargement 40b of bore 40a, to limit the angular displacement of cross link plate 40 on the shaft 390.

The lever arm locating means comprises a hydraulic piston and cylinder arrangement including a cylinder 45 with a piston (not shown) and a piston rod 46, the piston rod 46 having its forward end pivotally connected through a pivot pin 47 to the arm 43 and the cylinder 45 having a hemispherical formation 48 on its rear end engaged in a hemispherical recess 49 in a bearing block 50 secured to the top plate 27 of the rigid canopy 12. The bottom plate 28 has a slot 28a therein to allow free movement of the piston and

cylinder arrangement

45, 46 between the extreme positions of said

arrangements

45, 46.

The beam 36 also has a stop plate 51, conveniently a spring plate, secured to its underside and engageable with the undersurface of the rigid canopy 12 when the beam 36 is angularly displaced to a predetermined lower limit. The beam 37 also has a stop plate 52 secured thereon and arranged to act in identical manner to the plate 51. The

stop plates

51 and 52 abuts canopy l2 and fully supports the weight of their

respective beams

36 and 37 before the piston and

cylinder arrangement

45, 46 attains its fully retracted condition and thus permits the piston and cylinder arrangement to be readily removed from the support for servicing and/or replacement.

In long wall mining a plurality of mine roof supports of the type shown in FIGS. 1, 2 and 3 are arranged in side by side relationship with a conveyor, parallel with the coal face, located forwardly of the bases of the array of mine roof supports and the relay bar 26 of each mine roof support is connected to the conveyor. A coal cutting machine traverses along the coal face and the coal cut by the machine is discharged onto the conveyor and conveyed towards one end of the array of mine roof supports for removal by conventional means (not shown).

As the coal cutting machine travels backwards and forwards along the coal face and with the mine roof supports actively supporting the roof the piston and

cylinder arrangements

24, 25 of the mine roof supports are extended to advance the conveyor towards the coal face and thereby away from the bases 11. The canopy extensions 17 are preferably long enough to support the roof above the conveyor.

When the conveyor has been fully advanced by the piston and

cylinder arrangement

24, 25 the mine roof supports are individually advanced up to the conveyor. To advance a mine roof support up to the conveyor the lever arm locating means 44 of the support is partially retracted so that the piston 46 withdraws into the cylinder 45, thus permitting the canopy extension 17 to pivot clockwise about the shaft 35, thereby lowering the canopy extension from engagement with the mine roof, the

hydraulic props

13, 14, and 16 are lowered to lower the rigid roof canopy l2 and thereby disengage the support from the roof, and the piston 25 is retracted into the cylinder 24 whereby the mine roof support is drawn towards the conveyor by the piston and

cylinder arrangement

25, 24.

As will be seen from FIGS. 1 and 2 the outer bridging part 22b comprises an inclined rear wall 53 and

side walls

54 and 55 which define a wrap-around shield for the lower rear regions of the support. A flap 56, pivotally attached to a rear edge region of the canopy 12 by a pin 57, hangs down in sliding engagement with the outer surface of the inclined rear wall 53, thus forming a rear wall for the support. If required the flap 56 can include side walls, capable of embracing the

side walls

54 and 55, to obtain a wrap-around shield for the rear regions of the support. The flap 56 may also include side cheeks 56a shown in broken lines in FIG. 2, to provide a wrap-around configuration.

In order to provide for a degree of free movement between the flap 56 and the wrap-around

shield

53, 54, to prevent jamming due to the ingress of dirt, the pivot pin 57 between the flap 56 and canopy 12 is engaged in an elongate slot 58 in a lug 59 carried by or formed at the upper end of the flap 56. A pivot pin 57 and a lug 59 is conveniently provided on opposite sides of the flap 56.

When the mine roof support has been advanced by the desired amount the retraction of piston 25 into cylinder 24 is terminated, the

props

13, 14, 15 and 16 are extended to bring the rigid canopy 12 into a roof supporting condition and the lever arm locating means 44, is extended to rotate the lever arm 38 anticlockwise and thus cause the canopy extension to be rotated anticlockwise into a roof engaging condition.

As the mine roof above the overhange 17 may be at a slightly different level than the roof above the rigid canopy 12 the articulation of the canopy extension allows the canopy extension to adopt a roof supporting piston different from the plane of the upper plate 27 of the rigid canopy and, further, because the cross link plate 40 has limited angular displacement on the arm 39, the two

beams

36 and 37 can adopt different height positions to accommodate localised variations in the mine roof. In the event that a change of canopy length is required it is only necessary for the two

beams

36 and 37 to be replaced.

To replace the canopy beams 36 and 37 with other beams of different length the lever arm locating means 44, is retracted to lower the canopy extension 17, the

beams

36 and 37 are supported, the shaft 35 is withdrawn to release the

beams

36 and 37 preferably by drawing the shaft 35 first one way and then the other Way whereby the

beams

36 and 37 can be disengaged from the shaft 35 without disengaging the lever arm 38 from said shaft 35.

The disengaged beams 36 and 37 can then be easily removed, and the

new beams

36 and 37 attached to the rigid canopy 12 by reversing the procedure described above.

It will be observed that when changing the

beams

36 and 37 the rigid canopy 12 is not affected and the personnel involved in the beam change can take advantage of this protection afforded by the roof canopy 12 for the greatest part of the beam change operation.

The mine roof support illustrated in FIGS. 4, 5 and 6 comprises a mine roof support with a rear chock interconnected by a double acting hydraulic ram.

The roof support comprises, as in the embodiment of FIGS. 1, 2 and 3 above, and a rigid canopy l2 supported above the base 11 by a front pair of

hydraulic props

15, 16 and a rear pair of hydraulic props l3, 14. The canopy 12 presents a continuous surface for supporting the roof above the area of the base 11. A can opy extension 17 forwardly of the rigid canopy 12 comprises two

beams

36 and 37 pivotally attached to the rigid canopy 12 with a double arm lever 38 supporting the

beams

36 and 37 and positionally controlled .by a lever arm locating means 44.

The essential difference between the embodiment shown in FIGS. 1, 2 and 3 and the embodiment shown in FIGS. 4, 5 and 6 is that in the latter construction the cross-link plate 40 is fixed on the arm 39 and the

beams

36 and 37 are connected at their outer ends by a loading plate 60 so that

beams

36 and 37 are rigidly connected for mutual displacement. One further modification of the latter embodiment is that the double-acting piston and

cylinder arrangement

24, 25, 26 is reversed so that the piston rod 25 extends rearwardly from the cylinder 24.

The rear chock comprises a base generally designated 111, a pair of rear

hydraulic props

113, 114, a pair of front hydraulic props 115 and 116 and a solid roof canopy 112 carried on the

props

113, 114, 115 and 116. The base 111 is formed from a pair of parallel spaced apart, sledge-

like runners

120, 121 which are joined together by a bridging structure 122.

The rear of the chock is protected from flushing waste by means of a shield extension 123 and by means of a flap 125 hinged at its upper end to the rear end of the canopy 112 so as to hang in a generally vertically inclined manner to rest against the rear shield extension 123.

The

props

113, 114, 115 and 116 of the rear chock are supported in clamps 133. As best seen in the plan view in FIG. 6, these clamps 133 are of two part construction, each part being in the form of a complementary semi-circle and securable to the other part by means of bolts (not shown). One part of each clamp is secured to or formed integrally with the bridging structure 122, and the other part is bolted thereto to form the complete ring. A rubber ring (not shown) is provided on each prop and the ring is located between the prop and its supporting clamp 133 to provide a small degree of flexibility for the mounting.

A prop on the rear chock can be removed by releasing or at least partly releasing the chock from a roof engaging condition, breaking the clamp holding the prop, and swinging the prop sideways to allow the prop to be removed. The

props

13, 14, and 16 of the mine roof support are connected to the bridging

pieces

22 and 23 in similar manner to the props of the rear chock but are arranged to be removable from the support by displacement parallel to the longitudinal axis of the roof support.

The mine roof support and the rear chock are interconnected by means of a double acting hydraulic piston and cylinder arrangement comprising a cylinder 24, a piston (not shown) and a piston rod 25, the forward end of the cylinder 24 is secured to the forward end of the base of the mine roof support and the rear end of the piston rod 25 is connected to a relay bar 26 pivotally attached to the forward end of the base 111 of the rear chock.

By advancing or retracting the double acting piston and

cylinder arrangement

24, 25, relative movement between the mine roof support and chock is obtained. Thus, by setting, for example, the chock to the mine roof and lowering the

props

13, 14, 15 and 16 on the mine roof support, so that the canopy 12 no longer engages the mine roof, the mine roof support can be advanced by extending the piston and

cylinder arrangement

24, 25. The chock can then be brought up to the mine roof support by reversing the process. Thus, the

mine roof support is set to the mine roof, the props 113, I14, 1 l5 and 116 of the chock are lowered so that the canopy 112 of the chock becomes disengaged from the roof and the piston and

cylinder arrangement

24, 25 is retracted so that the chock is moved forwardly towards the mine roof support.

In the event that the chock and mine roof support are to be spaced apart for a length of time, it is necessary to provide support for the roof between the two supports and to this end a cantilevered extension member is pivotally attached at 166 to the front of the canopy 112 of the chock. Movement of the cantilevered extension member 165 is achieved by means of a hydraulic piston and cylinder arrangement 167 situated below the canopy 112 and secured to a lug 168 on the underside of the extension member 165.

Alternatively the roof between the canopy of the mine roof support and the canopy of the chock can be supported by a bar or plate slidably mounted within one of the canopies, conveniently the rear canopy, and displaceable outwardly of its respective canopy, conveniently by hydraulic power means, into the space between the canopies. Further, the bar or plate may, when extending outwardly of its supporting canopy, be arranged for vertical displacement, conveniently under the action ofa power capsule such as a hydraulic piston and cylinder arrangement, to upset saidbar or plate against the roof.

Hydraulic connections between the props 13, 14, I5 and 16,

props

113, 114, 115 and 116, and the

cylinders

45, 24 and the cylinder of arrangement 167 are pro vided with hydraulic pressure fluid in known manner and by for example supply lines 169 on the mine roof support of looped flexible pipe lines 170, of which only one is shown in FIG. 4 by way of example, providing hydraulic connections between the mine roof support and the chock.

It will be appreciated that the embodiment shown in FIGS. 1, 2 and 3 having a pivotally supported link plate 40 affecting independent angular displacement of the

beams

36 and 37, can have the cross link plate 40 rigidly secured on the arm 39, in the manner described with respect to the embodiment of FIGS. 4, 5 and 6, whereby the

beams

36 and 37 will be moved in unison.

Further, the link plate 40 of the embodiment shown in FIGS. 4, 5 and 6 can be mounted for angular displacement on its supporting arm 39 and the

beams

36 and 37 may have individual loading plates 60 thereon whereby the

beams

36 and 37 can be independently pivoted about their respective pivotal connections.

The

beams

36 and 37 can also be adapted to support extendable roof supports.

In the example shown in FIG. 7 the

beams

36 and 37 comprises hollow box girders open at their free ends and each

beam

36 and 37 has a box girder support member slidably inserted into its open end. Each support member 175 has an end plate 176 on its free end and the box girder support members 175 are extended from or retracted into their

respective beams

36 and 37 manually i.e. by an operator engaging a support member 175 to be adjusted with a suitable hand tool.

In the embodiment shown in FIG. 8 the support members 175 are slidably arranged in their

respective beams

36 and 37 and each support member 175 is slidably adjusted to its

respective beam

36 or 37 by a double acting hydraulic piston and cylinder arrangement generally indicated by reference numeral 180. Each arrangement 180 comprises a hydraulic cylinder 181 secured to its

respective beam

36 or 37 by a bracket 182 and a double-acting piston 183 slidably arranged in the cylinder 181 and connected at its free end to the support member 175. Thus, by driving the piston 183 outwardly with respect to the cylinder 181 the support member 175 is extended from its supporting beam and by retracting the piston 183 the member 175 is retracted into its supporting beam.

The embodiment illustrated in FIGS. 4, and 6, can be provided with steering means as shown in FIG. 9.

As illustrated in FIG. 9 the forward end of the cylinder 24 is attached to the forward part of the base 11 by a horizontal pivotal connection and the rear end region of the cylinder 24 lies between abutment blocks 201 and 202. The piston and

cylinder arrangement

24, 25 can thus pivot about the forward horizontal axis but the transverse movement of the piston and cylinder arrangement is severley limited.

The relay bar 26, rigidly secured on the end of piston rod 25, is pivotally attached to the base 111 of the rear chock and the relay bar 26 has a steering beam rigidly secured thereon. The steering beam presents two

transverse arms

203 and 204, the arm 203 supports the cylinder 205 of a hydraulic jack the ram 206 of which is engageable with a strong point, comprising a plate 207, mounted on the runner 121 of base 111, and the arm 204 supports the cylinder 208 of a hydraulic jack the ram 209 of which is engageable with a strong point, comprising a plate 210, mounted on the runner 120 of base 111.

Thus, when the rear chock is set against the mine roof and the forward mine roof support is disengaged from the roof, hydraulic fluid can be supplied selectively to the

cylinders

205 and 208 of the jacks to cause the steering beam, and thereby the piston rod 25, cylinder 24, and the forward mine roof support to be angu' larly displaced about the pivotal connection of the relay bar 26 with the base 111 to one side or the other side of the longitudinal axis of the rear chock.

The controlled articulation of the front support relative to the rear chock thus allows the support to be steered and a considerable advantage is obtained thereby.

In an alternative embodiment to that shown in FIG. 9 the piston rod 25 is attached to the base 11, restrained against transverse displacement, and the cylinder 24 extends rearwardly from the piston rod 25 and has its rearmost regions entered into and rigidly secured with the steering beam.

The steering beam is of box girder construction and the

cylinders

205 and 208 of the hydraulic jack are at least partially housed in the steering beam.

The centre limb 212 shown in broken line in FIG. 9 can be slidably disposed between the members and 21 of the base 11 thus to relieve the piston and cylinder arrangement of side loading.

1 claim:

1. A mine roof support comprising, in combination, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, comprising two spaced parallel beams, a common pivot pin hingedly independently connecting the beams to the rigid canopy for angular adjustment relative thereto and for individual replacement, a lever arm comprising a double arm lever separating pivotally supported relative to said rigid canopy by the common pivot pin between the two arms in a position protected by both said rigid canopy and the two beams, said double arm lever having one arm extending between the two beams to locate and support the canopy extension relative to said rigid canopy, said one arm having a cross-link member disposed remote from said common pivot pin extending transversely between the two beams and supporting the two beams, and lever arm control means acting between said rigid canopy and the second arm of said boule arm lever for locatingthe said lever arm and thereby said canopy extension relative to said rigid canopy.

2. A mine roof support according to claim 1 and wherein said arm of said lever arm supporting said canopy extension lies wholly within the confines of the canopy extension defined by said two beams.

3. A mine roof support according to claim 1 and wherein said cross-link member is rigidly connected to the lever arm.

4. A mine roof support according to claim 1 and wherein said cross-link member is pivotally supported on said lever arm for permitting relative movement between said two beams, and wherein stop means is provided between the cross-link member and said second arm for limiting the angular displacement of said crosslink member relative to said lever arm.

5. A mine roof support according to claim 1 and wherein stop plate means is provided between each of said beams and said rigid canopy for limiting the downward rotation of each of the beams relative to the rigid canopy.

6. A mine roof support according to claim 1 wherein each of said beams includes an upper inwardly directed flange, and each beam is supported by the flange thereof resting on said cross-link member.

7. A mine roof support according to claim 1 together with an adjustable extendable roof support member individual to and supported by each of said two beams.

8. A mine roof support according to claim 7 and wherein each of said beams has a hollow rectangular cross section and each beam is open at its forward end, and the adjustably extendible roof support member associated with each beam is slidably disposed in the hollow beam section to be outwardly or inwardly displaceably of its beam.

9. A mine roof support according to claim 7 and wherein each adjustably extendible roof support is dis placeable relative to its supporting beam by a piston and cylinder arrangement acting between the support member and said beam.

10. A mine roof support comprising, in combination, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension comprising two parallel beams hingedly connected to the rigid canopy so as to be angularly adjustable relative thereto, an adjustable extendible roof support member individual to and supported by each of said two beams, a lever arm pivotally supported by said rigid canopy and serving to locate and support the canopy extension relative to said rigid canopy, and lever arm control means acting between said canopy extension and said rigid canopy for causing displacement of the canopy extension relative to said rigid canopy.

11. A mine roof support according to claim and wherein each of said beams has a hollow rectangular cross section and each beam is open at its forward end, and the adjustably extendible roof support member associated with each beam is slidably disposed in the hollow beam section to be outwardly or inwardly displaceably of its beam.

12. A mine roof support according to claim 10 and wherein each adjustably extendible roof support is displaceable relative to its supporting beam by a piston and cylinder arrangement acting between the support member and said beam.

13. A mine roof support according to claim 10 and wherein a flap is pivotally attached to that end of said rigid canopy remote from the canopy extension, the flap hangs downwardly from said rigid canopy towards the base, and the base beneath the flap supporting end of the rigid canopy includes an upstanding wraparound shield comprising a rear wall and side walls, said flap engaging the outer surface of said rear wall and being a in sliding engagement therewith.

14. A mine roof support according to claim 13 and wherein said flap comprises a rear wall and side walls and said side walls of said flap embrace the side walls of said wrap-around shield.

15. A mine roof support comprising, in combination, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, hingedly connected to the rigid canopy so as to be angularly adjustable relative thereto, a lower arm pivotally supported by said rigid canopy and serving to locate and support the canopy extension relative to said rigid canopy, lever arm control means acting on said lever arm for locating the canopy extension relative to said rigid canopy, a hydraulic cylinder rigidly attached to the base, a piston slidably disposed in said cylinder and displaceable relative thereto, a coupling on the end of the piston remote from the cylinder for coupling the piston to equipment externally of the base and a steering beam supported by the piston and cylinder arrangement and capable of acting between said piston and cylinder arrangement and said equipment to effect lateral displacement between the mine roof support and said equipment.

16. A mine roof support according to claim 15 and wherein said piston rod is extensible outwardly from that end of the base adjacent the canopy extension.

17. A mine roof support according to claim 15 and wherein said piston rod is extensible outwardly from the base end remote from the hinged canopy extension.

18. A mine roof support according to claim 15 and wherein said steering beam includes two opposite laterally extending arms and two hydraulic jacks each hydraulic jack being supported by a laterally extending arm individual thereto and being extensible for engagement with said apparatus.

19. A mine roof support according to claim 18 and wherein each of said laterally extending arms supports the cylinder of its associated hydraulic jack and the rams of the jacks are displaceable parallel to the longitudinal axis of the piston.

20. In combination, a forward mine roofsupport and a rear mine roof support each of said mine roof supports comprising, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, hingedly connected to the leading edge regions of the rigid canopy so as to be angularly adjustable relative to the rigid canopy, a lever arm pivotally supported by said rigid canopy and serving to locate and support the canopy extension relative to said rigid canopy, and a lever arm locating means, said forward and rear mine roof supports being connected together by a piston and cylinder arrangement, the cylinder of which is secured to the base of said forward support and restrained against lateral displacement relative thereto, and the piston being extensible rearwardly from the base of the forward support and pivotally connected to the base of said rear mine roof support.

21. A mine roof support combination according to claim 20 and wherein said piston supports a steering beam and said steering beam includes hydraulic jack means capable of acting between said piston and said rear mine roof support to cause relative displacement between the axis of said piston and the longitudinal axis of the base of said rear mine roof support.

22. A mine roof support combination according to claim 21 and wherein said hydraulic jack means includes hydraulic jacks capable of acting between the steering beam and the rear mine roof support on both sides of the coupling between the piston and the rear

Claims

1. A mine roof support comprising, in combination, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, comprising two spaced parallel beams, a common pivot pin hingedly independently connecting the beams to the rigid canopy for angular adjustment relative thereto and for individual replacement, a lever arm comprising a double arm lever separating pivotally supported relative to said rigid canopy by the common pivot pin between the two arms in a position protected by both said rigid canopy and the two beams, said double arm lever having one arm extending between the two beams to locate and support the canopy extension relative to said rigid canopy, said one arm having a cross-link member disposed remote from said common pivot piN extending transversely between the two beams and supporting the two beams, and lever arm control means acting between said rigid canopy and the second arm of said boule arm lever for locating the said lever arm and thereby said canopy extension relative to said rigid canopy.

4. A mine roof support according to claim 1 and wherein said cross-link member is pivotally supported on said lever arm for permitting relative movement between said two beams, and wherein stop means is provided between the cross-link member and said second arm for limiting the angular displacement of said cross-link member relative to said lever arm.

9. A mine roof support according to claim 7 and wherein each adjustably extendible roof support is displaceable relative to its supporting beam by a piston and cylinder arrangement acting between the support member and said beam.

11. A mine roof support according to claim 10 and wherein each of said beams has a hollow rectangular cross section and each beam is open at its forward end, and the adjustably extendible roof support member associated with each beam is slidably disposed in the hollow beam section to be outwardly or inwardly displaceably of its beam.

13. A mine roof support according to claim 10 and wherein a flap is pivotally attached to that end of said rigid canopy remote from the canopy extension, the flap hangs downwardly from said rigid canopy towards the base, and the base beneath the flap supporting end of the rigid canopy includes an upstanding wrap-around shield comprising a rear wall and side walls, said flap engaging the outer surface of said rear wall and being a in sliding engagement therewith.

20. In combination, a forward mine roof support and a rear mine roof support each of said mine roof supports comprising, a base, a rigid canopy, hydraulic props between said base and said rigid canopy serving to support said rigid canopy above said base and to afford vertical displacement of said rigid canopy relative to said base, a canopy extension, hingedly connected to the leading edge regions of the rigid canopy so as to be angularly adjustable relative to the rigid canopy, a lever arm pivotally supported by said rigid canopy and serving to locate and support the canopy extension relative to said rigid canopy, and a lever arm locating means, said forward and rear mine roof supports being connected together by a piston and cylinder arrangement, the cylinder of which is secured to the base of said forward support and restrained against lateral displacement relative thereto, and the piston being extensible rearwardly from the base of the forward support and pivotally connected to the base of said rear mine roof support.

22. A mine roof support combination according to claim 21 and wherein said hydraulic jack means includes hydraulic jacks capable of acting between the steering beam and the rear mine roof support on both sides of the coupling between the piston and the rear mine roof support.