US3240021A - Mine roof supporting structure - Google Patents

Description

March 15, 1966 M. MERIAUX ETAL MINE ROOF SUPPORTING STRUCTURE 3 Sheets-Sheet 1 Filed July 20, 1962 M. MERIAUX ETAL 3,240,021

mm ROOF surronwme STRUCTURE 3 Sheets-Sheet 2 9 N u A mi; i

March 15, 1966 Filed July 20, 1962 MINE ROOF SUPPORTING STRUCTURE Filed July 20, 1962 3 Sheets-Sheet 3 Fig.4

United States Patent 3,24%,ti21 MHNE RUUF SUPPQRTlNG STRUQTURE Michel Meriaux and Michel habiachoflombier, Witteh sheim, France, assignors to Mines Domaniales do Potasse dAlsace, Mulhouse, Ham-Rhine, France, a French society Fitted .luiy 20, 1962, Ser. No. 211,344 Claims priority, application France, July 22, 1961, 868,738 3 Claims. (Cl. 6145) The conventional form of support in mine roof supporting structures essentially comprises, at the edge of the blasting region, a very highly resistant supporting line made up of piles or props, and usually, an auxiliary support in the working passage, usually made up of props with or without extensions.

In mechanised workings, in which a working passage is required to be kept clear as possible, auxiliary support for overhang by extensions on props or piles is being adopted to a greater and greater extent, since it makes it possible to have a free front line of props along which a cutting machine, such as a plane or undercutter, can run without any trouble.

However, a large labour force is required for using a system of mechanical extensions on props or piles, since extremely large tonnages of equipment have to be handled each time the supporting system is moved.

Systematic use of hydraulic control means in working faces having moving supporting systems has enabled the operation of placing the extensions in position to be fully mechanised, with all the desired flexibility and convenience in use.

To this end, movable supporting elements in present day embodiments are very often equipped with extensions of different types, intended to support the roof above the working passage; these extensions are usually clamped against the roof by a mechanical system; sometimes they are of the hydraulic-lift type.

However, there is very often only a little free height remaining between the cutting machines and the roof; the extensions then become a great nuisance, and have to be dismantled for the cutting machine to pass. Even if the cutting machine can run below the extensions under normal conditions, the latter abut against the machine as soon as the roof subsides abnormally, and have to be dismantled or folded back.

The present invention seeks to allow these disadvantages to be overcome, and in accordance with the invention, a mine roof supporting structure comprises an extension which is adapted to be slidably mounted in a recess in a roof supporting member for movement between a retracted position and an extended position in which it projects forwardly from the said member, and a hydraulic clamping device which is operative to force the extension, in its extended position, against a mine roof.

Preferably, a second extension is provided which is housed in the first extension, and is movable between a retracted position and an extended position, and can be clamped in its extended position between the first extension and the mine roof.

Such a structure can be so arranged that, when the said extensions are fully extended, they can immediately sup port the roof which is uncovered after the cutting machine has passed; in addition, the extensions may be capable of being fully retracted into the cover of the main supporting element should the roof subside or also should the cutting machines be particularly bulky, and this possibility enables the working passage to be completely cleared for the said machines to pass. Moreover,

the extension system may be retracted at the last moment, that is to say even if the front part of the cutting machine is already engaged under the said extensions; in addition to this great flexibility in use conferred on it by its mechanical design, this system of extensions is designed to be hydraulically clamped against the roof, that is to say it exhibits all the advantages of the hydraulic supporting system.

Features and advantages of the invention will become clear from the following description of two preferred forms thereof which are illustrated in the accompanying drawings.

FIGURE 1 is a sectional elevation of a supporting structure in accordance. Wtih the invention;

FIGURE 2 is a part-sectioned elevation, similar to FIGURE 1, showing some parts in different relative positions;

FIGURE 3 is an elevation similar to FIGURE 1, showing parts in other different relative positions; and

FIGURE 4 is an elevation of a variant of embodiment.

With particular reference to FIGURE 1 of the drawing, the supporting structure comprises a first extension l which can retract fully into the cover 2 of a main roof supporting element, and a second extension 3 which can be fully retracted into the extension 1. However, the second extension 3 need not be provided unless there is a large degree of overhang to be supported; if less protection is suflicient, the structure need comprise only the single extension l.

The first extension it consists of a steel box-girder element, of a profile which enables heavy stresses to be withstood, while leaving the internal space la required for the second extension 3 to be able to be fully accommodated therein. At its forward end, the first extension ll comprises bearing portion 1b which is forced against the roof when clamping takes place, and, if required lugs (not illustrated), intended to facilitate extending and retracting movements of the said extension. At its rear end the extension 1 is formed with a stroke-limiting abutment 1c which can cooperate with a cross-member 2a mounted in the cover 2 in order to prevent the extension from emerging from the said cover when not required to do so. If required, this abutment may be used to guide the extension 1 inside the recess 2b in the cover 2. In its lower face, the extension 1 has a spherical cavity 1d intended to receive the head 4a of a hydraulic jack 4 which will be described later.

In the retracted or non-operative position, only the handling lugs of the extension ll protrude from the cover 2; in the extended or Working position, the extension comes to bear under the action of the jack 4 against the abutment 1c and against the head 4:: of the jack, while the bearing portion 1b comes into contact with the roof 5 of the working passage (see FIGURE 2). The stroke of the stern of the jack 4 and the dimensions of the extension 1 are so calculated that this contact can be made with large amounts of inclination between the extension and the cover 2: for example, angles of 7 to 8 may easily be obtained for extension lengths of 800 to 1000 mm. The aperture in the cover 2 may also be made of flared shape in order to give increased possibilities of clearance to the extension l, and to enable the system of extensions to be adapted to very undulating roofs (see positions A, B, C, FIGURE 2).

The second extension 3 is intended to lengthen the extension 1 up to the face of the workings in order to support the new roof uncovered by the cutting machine, just after the latter has passed. In view of the fact that the stresses to be taken into consideration are much less heavy in the case of the extension 3, the latter may be a single strip of spring steel, or ordinary steel, according to the roofs encountered. If circumstances require, it may also be a profiled member of any shape. This secnd extension 3 retracts fully into the internal space 1a of the extension 1; it is furthermore fitted with a strokelimiting abutment 3a which can cooperate with a shoulder 16 on the upper wall of the recess 1a in order to prevent the extension 3 from emerging completely from its recess. In the telescoped or retracted position, this extension 3 may be clamped against the roof, without any need to touch the extension 1, by virtue of an auxiliary clamping system using a wedge 6. This clamping device enables the extension 3 to be correctly clamped against the roof 5, even if the latter comprises undulations or irregularities (see FIGURE 3).

This make it possible to embody a system of extensions enabling support to be provided, for example, for a load of 500 kg., which is assumed to be concentrated at the end of the second extension 3, in addition to a load of one ton at the end of the first extension 1 on the carrier plate 1b.

The operation of sliding the extensions is particularly easy, since these pieces move in a horizontal plane.

The hydraulic clamping device is intended on the one hand to clamp the whole telescopic unit against the roof, and on the other hand to control lowering of the roof by offering a definite resistance. It takes the form of a hydraulic jack mounted on a bracket 7 fast with the cover 2 of the supporting element.

The jack 4 may be a single-acting hydraulic jack, the weight of the extensions as a whole being quite sufficient to force the ram into the cylinder when the jack is re lieved of pressure. Its stroke must be sutficient to give clearance for the higher extensions (positions A, B, C, FIGURE 2), and the force which it develops is clearly a function of the loads which it is desired to support at the end of the extensions 1 and 3, and must consequently be adapted to the resistance to bending exhibited by the said extensions. For example, for the loads envisaged above on the extensions 1 and 3, a force of 8 to 9 tons for the jack 4 is very suitable. The jack may be fed by a single conduit which gives both feed and return, inlet (when the feed pump is running) or exhaust (when the pump is stopped) being via the same Valve (needle-tap, poppet valve or any other similar device).

In order to prevent undue bending stresses to be set up in the extensions due to collapsing of the mine roof, there is provided a safety valve (not shown) for relieving the pressure in the jack whereby to allow the jack to telescope under a predetermined mine roof pressure. The pressure required for clamping purposes must be very close to the pressure at which the valve will open in order to limit as far as possible the effects due to elastic deforma tion of the extensions. For example, if clamping is to take place at 200 kg./cm. the safety valve may be set for a pressure of 250 kg./cm.

The safety valve may be mounted on the jack unit itself, and may exhaust to atmosphere. In view of the small cross-section of the jack, the volume of liquid to be discharged if sliding occurs will remain practically negligible.

The auxiliary clamping device 6 enables the extension 3 to be locked or unlocked independently of the extension 1.

This device is a simple wedge which can be attached by a small chain to the end of the extension 1. For clamping purposes, this wedge is inserted and clamped under the extension 3 at the entrance to the recess 1a; the extension 3 is then forced against the roof 5, and bears against the stroke-limiting abutment 3a and the wedge 6.

The system of extensions is furthermore so calculated that if a load is applied at any point on one of the extensions 1 or 3 when they are fully extended the jack 4 will collapse before the elastic limit of one of the said extensions is reached.

The lengths of the two extensions 1 and 3, their profiles, their mechanical resistances, and the force developed by the jack 4 and its stroke are clearly a function of the local conditions of the roof, the width of the working passage, and the depth of cut of the cutting machine.

For optimum operation, the various features of the system of extensions must therefore be adapted to the characteristics of the workings; the extensions are made and designed to work normally in the fully extended state, and they must be calculated for these conditions, which are the most unfavourable.

However, it must be noted that each of the extensions 1, 3 may be clamped against the roof in any position intermediate its retracted and fully extended positions, which clearly gives the system very great flexibility in use by allowing the bearing portion of the extension 1 or of the extension 3 to be placed at a carefully chosen point. For example it may be desired to support a particular portion of the roof which is cracked or fractured or is otherwise of doubtful strength. Similarly, if the working passage is abnormally contracted one or other of the two extensions, or both, may be used partially or fully extended.

The following examples illustrate the use of the above described structure in various circumstances.

(1) Before the cutting machine arrives, the first extension 1 (FIGURE 2) is fully extended from the cover 2 of the main supporting element; the extension 1 is clamped against the roof 5 by the jack 4; with the second extension 3 normally in its retracted position in the extension 1, the wedge 6 being simply lodged under the extension 3 at the entrance to the recess 1a. If roof conditions are difiicult, the extension 3 may be extended from the extension 1 as far as the face of the workings, thus giving protection to the whole working passage.

(2) As the cutting machine approaches, two cases are then possible:

(a) If the roof is normal, and the cutting machine is not too bulky as regards height, so that there is a clear ance of more {than about ten centimetres between the roof and the said machine; in this case, the extension 1 may be left in place, and will continue to support the roof above the machine all the time it is moving. Immediately after the machine has passed, the extension 3 is fully extended from the extension 1 and clamped against the roof by its wedge 6; the roof which has just been uncovered is therefore immediately supported.

(b) If the roof has subsided abnormally, in consequence of a blasting operation, for example, or even if, under normal conditions, the cutting machine does not leave sutficient clearance between itself and the roof, the extension 1 cannot be kept above the machine while the latter is moving.

In these circumstances, the extensions 1 is retracted into the cover 2 at the last moment. The jack 4 is exhausted and the extension 1 is freed and can thus be retracted into the cover 2, the extension 3 still remaining inside the extension 1. This operaion may be carried out in all cases at the very last moment, even if the front part of the machine is already engaged under the extension, and this is a considerable advantage with respect to known pivoting or demountahle extensions, the removal of which involves insoluble problems once the machine is engaged. If the roof is very unsafe after the extension 1 has been fully retracted and re-clamped by restoring pressure to the jack 4, the extension 3, which is much less thick than the extension 1, may in certain cases be extended and re-clamped against the roof; this additional protection may be advantageous with very difficult roofs.

After the cutting machine has passed, the jack 4- is unclamped, the extension 1 is brought fully extended from the cover 2 again, the extension 3 is extracted from the extension 1, the wedge 6 is placed in position, and the whole is re-clamped against the roof by the jack 4; as in the foregoing case, the roof which has been uncovered is supported immediately the machine has passed.

(3) To return the cutting machine, in the case of cutting machines working in a single direction along the front, the machine will in most cases be able to pass below the fully spread out system of telescopic extensions without any operation having to be carried out; as a general rule, in fact, the cutting machine is considerably lower in the return position than in the cutting position.

If this were not the case, or if the roof had subsided considerably in consequence of a blasting operation, the same operations as those described in Example 2 above could be carried out upon return.

(4) Upon moving the supporting system at the instant when the pile is moved, the cover 2 is disengaged from the roof; the whole telescopic unit is therefore automatically unlocked. The only additional operation consists in returning the extension 3 into the extension 1 (fully or otherwise), after the cover has been disengaged. The cover 2 being again clamped against the roof in its new position, all that remains is to restore pressure to the jack 4 of the telescopic unit.

Since the telescopic device is intended most of the time to complete a moving hydraulic supporting system, suitable connection of the hydraulic means can automatically restore pressure to the jack 4 at the instant when the pile is moved; the telescopic unit will be automatically re-clamped at the instant when the pile is re-locked, excess liquid from inside the jack 4 being discharged via the safety valve, operation of the device being thus further simplified.

In the second embodiment illustrated in FIGURE 4 of the drawing, the jack 4', instead of being mounted on a bracket fast with the cover 2, is fixed at the end of the first extension 1, and moves in unit with the said extension. This jack may be fed by a flexible pipe 472 which is fitted inside the cover 2 in order not to hinder movement of the system of extensions.

In addition, a bearing plate is pivoted at the entrance of the recess 2b. In the telescoped or retracted position, the jack 4' acts vertically upwardly on the upper wall of the recess 2b to bring the extension 1 to bear both against the piece 20 and the head 4a of the said jack. This system of extensions is used in the same way as the system of extensions described above.

The advantage of this variant is that it is less bulky, enabling it to be used in shallow seams.

The advantages exhibited by the structure described above are various when the roof is used for the support of unsafe roofs.

The structure primarily is intended for incorporation in any hydraulic supporting system, in particular a moving supporting system; however, it may be adapted to any kind of supporting system comprising a cover which will enable the extension 1 to be accommodated in the retracted position.

Because it enables practically any working passage to be covered, and also allows for strict control of lowering of the roof, the structure described above gives virtually complete safety in working faces in return for very simple operations. Its flexibility and convenience in use are its essential qualities: it makes it possble to uncover only the very minimum required for the cutting machine to pass, which is an indispensable condition in the case of poor roofs.

Its operation is particularly simple when it is used on a moving supporting system, and when it is itself controlled by a hydraulic jack.

Various modifications in the structure described above can of course be made within the scope of the invention; for example the wedges 6 could be replaced by any equivalent clamping means.

We claim:

1. In a mine roof supporting structure, the combination comprising a mine roof supporting member having a hollow interior defining a recess, an extension member slidably disposed in said recess in a telescoping arrangement, said extension member being movable from a retracted position in the recess to an extended position relative to the recess, one end of said extension member remaining Within said recess, a bearing member positioned within said recess adjacent one end of said supporting member, said bearing member adapted to engage said extension member intermediate the ends thereof to thereby provide a fulcrum for the extension member when at the extended position, hydraulic clamping means secured to said extension member in proximity to said one end thereof, said hydraulic clamping means being carried as a. unit by the extension member and movable therewith, said hydraulic clamping means including a hydraulic jack having a ram element, said ram element being movable into engagement with the interior of said supporting member, whereby said extension member is pivoted about the bearing member such that said one end of said extension member moves in one direction and the opposite end of said extension member is moved in the opposite direction and forced against a mine roof.

2. The combination as recited in claim 1, wherein said extension member is hollow and a second extension member is slidably disposed therein.

3. The combination as recited in claim 2 wherein wedging means is operatively disposed between said extension member and said second extension member.

References Cited by the Examiner UNITED STATES PATENTS 3,127,748 4/1964 Cooke 61-45.2

FOREIGN PATENTS 1,192,849 4/1959 France.

1,245,142 9/1960 France.

1,077,618 3/1960 I Germany.

823,586 11/1959 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, EARL I. WITMER,

Examiners.

Claims (1)

1. IN A MINE ROOF SUPPORTING STRUCTURE, THE COMBINATION COMPRISING A MINE ROOF SUPPORTING MEMBER HAVING A HOLLOW INTERIOR DEFINING A RECESS, AN EXTENSION MEMBER SLIDABLY DISPOSED IN SAID RECESS IN TELESCOPING ARRANGEMENT, SAID EXTENSION MEMBER BEING MOVABLE FROM A RETRACTED POSITION IN THE RECESS TO AN EXTENDED POSITION RELATIVE TO THE RECESS, ONE END OF SAID EXTENSION MEMBER REMAINING WITHIN SAID RECESS, A BEARING MEMBER POSITIONED WITHIN SAID RECESS ADJACENT ONE END OF SAID SUPPORTING MEMBER, SAID BEARING MEMBER ADAPTED TO ENGAGE SAID EXTENSION MEMBER INTERMEDIATE THE ENDS THEREOF TO THEREBY PROVIDE A FULCRUM FOR THE EXTENSION MEMBER WHEN AT THE EXTENDED POSITION, HYDRAULIC CLAMPING MEANS SECURED TO SAID EXTENSION MEMBER IN PROXIMITY TO SAID ONE END THEREOF, SAID HYDRAULIC CLAMPING MEANS BEING CARRIED AS A UNIT BY THE EXTENSION MEMBER AND MOVABLE THEREWITH, SAID HYDRAULIC CLAMPING MEANS INCLUDING A HYDRAULIC JACK HAVING A RAM ELEMENT, SAID RAM ELEMENT BEING MOVABLE INTO ENGAGEMENT WITH THE INTERIOR OF SAID SUPPORTING MEMBER, WHEREBY SAID EXTENSION MEMBER IS PIVOTED ABOUT THE BEARING MEMBER SUCH THAT SAID ONE END OF SAID EXTENSION MEMBER MOVES IN ONE DIRECTION AND THE OPPOSITE END OF SAID EXTENSION MEMBER IS MOVED IN THE OPPOSITE DIRECTION AND FORCED AGAINST A MINE ROOF.

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