Abstract:
A directional gas pressure device ( 1 ) comprises a body including an elongate slot ( 2 ) extending in the axial direction of the body the body providing a chamber having an opening ( 2   c ) in at least one end thereof; at least one closure member ( 3 ) adapted to engage with the at least one opening of said chamber; a tie member including an elongate element ( 6 ) and spaced apart stop members. The elongate slot of the body is adapted to receive the elongate element of the tie member.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to directional gas pressure devices, typically for use in the breaking of rock or concrete, and in particular to a directional gas pressure device that does not require backfilling with sand or other sealants. The present invention also relates to a method of breaking rock from a face (a mine face or quarry face) using a directional gas pressure device of the invention. 
       BACKGROUND OF THE INVENTION 
       [0002]    High explosives are widely used for breaking rock during quarrying and mining, and in demolition. Whilst explosives are effective, they are not particularly efficient in terms of their energy use, they are dangerous and hence are subject to specific regulation relating to their use, storage and transport. Where explosives are used for demolition, it is necessary to clear a large area around the site because of the distance both large and small particles are dispersed by explosive material. Where explosives are used in underground mines the whole mine must be cleared of personnel during blasting. Further, it is necessary to allow a certain period of time to elapse following blasting because of the possibility of rockfalls, and where blasting takes place underground, the existence of dangerous gases. 
         [0003]    High explosives have detonation speeds in the order of 6000 to 9000 metres per second which induces a shock wave in rock, thereby breaking it. In certain circumstances high explosives may limit the depth of rock which may be removed during one blasting episode. This is because if the charge is placed too deeply beyond the surface of the rock back fractures may occur, making the mine or quarry unsafe. In such applications it is generally considered that high explosive charges should not be placed more than 1.2 m beyond the rock face. 
         [0004]    An alternative to splitting rock with explosive is the directional gas pressure system. In this system a hole is bored in a rock and a directional gas pressure device is inserted therein. The bore is backfilled with sand or another suitable sealant. When the device is fired, rather than exploding, a chemical reaction is started which evolves a large volume of gas. The pressure within the bore builds up and is relieved by the rock splitting. The detonation speed of the pyrotechnic charges used in directional gas pressure devices is in the order of 40 to 60 metres per second. These devices do not create a shock wave. Therefore, it is possible to locate such devices further from the rock surface, thereby allowing a greater quantity of material to be removed from the face during one blasting episode. 
         [0005]    The directional gas pressure system is more efficient than explosive charges in terms of the amount of energy released to split a rock or demolish a building or structure. For example, when using the directional gas pressure system compared to an explosive charge, significantly less dust is produced. This has two benefits. First, it is possible to work in closer proximity to rock being broken using the directional gas pressure system than it is where explosive charges are used. In the case of an underground mine, generally the whole mine would be cleared whilst blasting is taking place, whereas where the directional gas pressure system is used work can continue much closer to the area where rock is being broken. Another benefit of the directional gas pressure system is that the charges are intrinsically much safer than explosives. Their classification and rules relating to their use reflect this. A further benefit of this system is that they create much less noise than high explosives and do not cause problematic emissions of toxic gases. 
         [0006]    As mentioned above, the directional gas pressure device is inserted into a bore and the bore backfilled with sand or another suitable sealant material. Back filling with sand is inexpensive in terms of materials, but requires labour and a supply of sand where the rock is being broken. Further, sand may only be used where the direction of the bore is inclined above the horizontal, otherwise the sand may run out of the bore, in which case the rock would not be broken and the directional gas pressure device would not be safe. Also, the consistency of the sand used in stemming is critical. For example, if the sand is too dry or too wet a ‘blow out’ may occur. A blow out may also occur if the sand grains are too big or of inconsistent shape. 
         [0007]    Other back filling materials may be used, but these may be expensive. For example, resin based fillers may be used, but even with such filler materials there remains the problem that where the bore lies below the horizontal it is difficult to be certain that the bore is filled adequately without pockets of air for example. When using resins sometimes residual oil or water from the drilling machine can have an adverse effect on the resin and subsequently cause ‘blow outs’. 
         [0008]    Gas pressure devices that require stemming agents can only be used where a bore of sufficient depth can be formed. For example, where a gas pressure device of 30 mm length is to be used, this must be packed with a 1 metre depth of stemming agent. Hence, such a gas pressure device cannot be used to break a relatively narrow concrete component of a building, such as a concrete girder. 
         [0009]    United Kingdom patent application published under number 2341917 describes a directional gas pressure device of the type described above. 
         [0010]    International patent application number WO 2006/063369 describes a container for a pyrotechnic device. This invention relates to closing the container of a pyrotechnic device so that the device may be subject to less stringent rules when transported than is the case for other closure arrangements. 
         [0011]    It would therefore be desirable to provide a directional gas pressure device the operation of which does not require backfilling. 
         [0012]    A rock breaking cartridge is described in U.S. 2008/0047455. In the device described the charge is housed in a tube which is closed at one end by a cap. The mid part of the tube is filled with stemming material (such as sand) and the other end is closed by a pair of wedges. When the device is inserted into a bore in rock to be broken one of the wedges is driven further into the tube thereby securing the device in the bore. The device may be used without the intermediary filler, in which case the device is held in the bore by the wedges which are forced further apart by the gas pressure within the device. 
         [0013]    Whilst the above-mentioned device does not require backfilling its use may be limited to relatively low gas pressures. This is because the device relies on the gas pressure to be contained by the wedges. If the wedges fail, it is likely that the increased gas pressure would fire the device out of the bore. 
         [0014]    Mining typically involves breaking up material to be extracted at a face, loading such material on to a transport means and delivering the material to a processing plant. As mentioned above, explosives may be used to break material from the face, but the use of explosives typically requires clearance of the mine. Blasting would usually be done whilst miners are not present, for example before the miners start work each morning or between shifts. However, this means that a comparatively large amount of material must be broken from the face to provide sufficient work for the miners to move during their shift. Also, there is the danger that unauthorised personnel may be present during blasting. 
         [0015]    It would therefore be desirable to be able to mine material without using explosives. 
         [0016]    Some mining does take place without blasting, using machines for example. Patent application no CA 2060288 describes a machine which uses multiple cutting blades to cut away material from a face. However, such machines may not be used in all situations, require the installation of rails and other infrastructure, and are very expensive. 
         [0017]    Where blasting is used it is nevertheless possible to automate the blasting process to a certain extent. For example, patent application no WO97/21068 describes a vehicle adapted to drill bores in a material face and insert explosive charges. 
         [0018]    The directional gas pressure device described in GB2468133 describes a directional gas pressure device that does not require backfilling with sand. 
         [0019]    The directional gas pressure device described in GB2468133 represents a significant step forward insofar as no backfilling is required. Not only does this remove a step and therefore reduce labour and cost, but the directional gas pressure can also be used effectively when oriented in the horizontal plane, whereas devices requiring backfilling are known to not function well in such an orientation. 
         [0020]    However, it would be desirable to provide a direction gas pressure device having the advantages of the device described in GB2468133, yet which is simpler to assemble. 
       SUMMARY OF THE INVENTION 
       [0021]    According to one aspect of the invention there is provided a directional gas pressure device comprising a body having openings at each end thereof, a closure member for each end thereof, a tie member extending through the body, the closure members being attached to the tie member, wherein the closure members are adapted to increase in size upon detonation of a pyrotechnic charge material contained within the body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    In the drawings, which illustrate preferred embodiments of a directional gas pressure device according to the invention: 
           [0023]      FIG. 1  is a schematic representation of a directional gas pressure device according to the invention; 
           [0024]      FIG. 2  is a schematic representation of the directional gas pressure device illustrated in  FIG. 1  with a cover thereof opened; 
           [0025]      FIG. 3  is a schematic representation of a component of the directional gas pressure device illustrated in  FIGS. 1 and 2 ; 
           [0026]      FIG. 4  is a schematic representation of another component of the directional gas pressure device illustrated in  FIGS. 1 and 2 ; 
           [0027]      FIG. 5  is a schematic representation of end seals of the directional gas pressure device illustrated in  FIGS. 1 and 2 ; 
           [0028]      FIG. 6  is a schematic representation of an encasing component in a closed configuration; 
           [0029]      FIG. 7 a    is a schematic representation of lower collar elements of the directional gas pressure device illustrated in  FIGS. 1 and 2 ; 
           [0030]      FIG. 7 b    is a schematic representation of upper collar elements of the directional gas pressure device illustrated in  FIGS. 1 and 2 ; 
           [0031]      FIG. 8  is a schematic representation of the encasing component illustrated in  FIG. 6 ; 
           [0032]      FIG. 9  is a schematic representation of a device according to an alternative embodiment of the invention; and 
           [0033]      FIG. 10  is a schematic representation of a part of the device illustrated in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Referring now to  FIGS. 1 and 2 , which illustrate a directional gas pressure device  1  in assembled form or substantially assembled form, the device  1  comprises a tube member  2 , end caps  3 ,  3 ′, collars  4 , bosses  6 ,  6 ′ and a cover  5 . 
         [0035]    The tube member  2  is illustrated in greater detail in  FIG. 4  and comprises a chamber  2   c  formed by wall members  2   a,    2   b.  The wall member  2   a  is curved and is of constant radius, the ends of the wall member  2   a  intersecting the wall member  2   b.  The wall member  2   b  comprises two substantially parallel sides  2   b ′ joined together by a substantially semi-circular end portion  2   b ″. The sides  2   b ′ and the semi-circular end portion  2   b ″ together define a slot  2   d  extending axially along the tube member  2 . The inner surface of the wall member  2   a  and the outer surface of the wall member  2   b  together provide a chamber  2   c,  the ends of which are open. 
         [0036]      FIGS. 5 a  and 5 b    illustrate end caps  3 , which are adapted to engage with and close the open ends of the tube member  2 . Each of the end caps  3  includes a lip portion  3   a  and axially extending walls  3   b,    3   c  forming a tube engaging portion. Each of these portions has a cross-sectional shape corresponding to the cross-sectional shape of the chamber  2   c  of the tube  2 . The walls  3   b,    3   c  of the tube engaging portion have an external dimension corresponding to the internal dimension of the chamber  2   c  of tube  2 , such that the end cap  3  is a push fit in the chamber  2   c.  The lip  3   a  limits the extent to which the end cap  3  may be pressed into the chamber  2   c.    
         [0037]    The end cap  3  includes stiffening elements  3   f  extending between the walls  3   b  and  3   c  of the tube engaging portion and resist forces acting on the wall  3   b  to collapse the said wall. 
         [0038]    The end cap  3  illustrated in  FIG. 5 b    differs from the end cap  3  illustrated in  FIG. 5 a    in that the end cap  3  illustrated in  FIG. 5 b    includes a slot  3   e,  which is provided to receive the wire(s) of an electrical initiator. When an electric current is passed through the initiator, the pyrotechnic material is heated and a chemical reaction evolving gas initiated. 
         [0039]    Referring now to  FIGS. 7 a  and 7 b   , in each of these Figures there is illustrated a collar element  4 , which in the illustrated example is substantially semi-circular in cross-section. Whilst the collar elements  4  are semi-circular, they could be of different shape, and there may be more collar elements  4 . The collar elements  4  illustrated in the respective figures being arranged to co-operate with one another. The collar element  4  of  FIG. 7 a    comprises an substantially flat end face  4   a  including a first detent  4   b  of substantially semi-circular cross section, and a second detent  4   c  of substantially square cross-section, both having an open edge. The outer surface of each collar element  4  is provided with a slot  4   d  extending circumferentially around the said outer surface. 
         [0040]    The collar element  4  illustrated in  FIG. 7 a    includes bores  4   f  situated in a wall  4   e  of the collar element  4 . The bores  4   f  are configured to receive protrusions in the form of pegs  4   f  of the collar element  4  illustrated in  FIG. 7 b   . The pegs  4   f  are a push fit into the bores  4   f.  Hence, when the bores  4   f  of the collar element  4  of  FIG. 7 a    are aligned with the pegs  4   f  of the collar element of  FIG. 7 b    and the two elements are pressed together, the two collar elements will become attached to one another. 
         [0041]    Each collar element  4  includes a sloping surface  4   g.  The function of this sloping surface is described below. 
         [0042]    Referring now to  FIG. 3 , there is shown a rod member  6  supporting a boss  6 ,  6 ′ at each end thereof. The bosses  6 ,  6 ′ are joined together by a stem  6   e.  The boss  6  and boss  6 ′ are both frusto-conical in shape providing a sloping wall  6   a,    6   a ′ extending around the boss. The boss  6 ′ mounts a T-shaped member  6   b  extending from the end face of said boss  6 ′. The member  6   b  includes a stem  6   c.  The function of the T-shaped member  6   b  is to provide a means by which a line may be tied to the device, allowing it to be retrieved in the event of a mis-fire. 
         [0043]    The boss  6 ′ also includes a detent  6   d  extending parallel with the longitudinal axis of the rod member  6 . 
         [0044]    A cover  5  which secures the component parts of the device together is best appreciated from  FIGS. 2, 6 and 8 . The cover  5  includes first and second elements  5   a,    5   b  attached together by a hinge  5   f,  the first and second elements  5   a,    5   b  and the hinge  5   f  being formed of a single plastics moulding in the present example. Protrusions  5   e  extend inwardly of the inner surface of first and second elements  5   a,    5   b  at each end thereof. In the illustrated example, these protrusions extend circumferentially around the first and second elements  5   a,    5   b.  The inner surface of the first element  5   a  is provided with additional protrusions  5   e ″ extending in the axial direction of the cover  5 . The protrusions  5   e  are so shaped and dimensioned as to engage with the slot  4   d  of the collar element  4  and prevent any relative movement between the collar elements  4  and the cover  5 . The protrusions  5   e ′ are so shaped and dimensioned as to engage with the slot  4   c  of the collar element  4 . 
         [0045]    The cover  5  includes a tamper proof fastening arrangement comprising protrusions  5   c  extending from the free edge of the first element  5   a  which are configured to engage with recesses  5   d  located proximate the free edge of the second element  5   b.  The protrusions  5   c  are of the type that cannot be released from the recesses  5   d  without fracturing at least one of the protrusion  5   c,  the recess  5   d  or a part of one of the first and second elements  5   a,    5   b.    
         [0046]    Assembly of the directional gas pressure device of the invention is described below. 
         [0047]    First, an end cap  3  is fitted to one end of the tube member  2 . The chamber  2   c  of the tube member  2  is then filled with pyrotechnic material, typically in powder form. Once filled, the other end of the tube member  2  is closed by a cap  3 . 
         [0048]    The stem  6   e  of rod member  6  is then aligned with the slot  2   d  of the tube member  2 . 
         [0049]    A pair of co-operating collar elements  4  is mounted on the rod member  6  at each end thereof such that the sloping surface  4   g  of the collar element  4  engages with the correspondingly sloped surface  6   a,    6   a ′ of the boss  6 ,  6 ′ of said rod member. The collar elements  4  are pressed together so that pegs  4   f  engage with the bores  4   f.    
         [0050]    The assembly is then placed within a part of the cover  5 , which is then closed to secured the assembled components together. 
         [0051]    The embodiment illustrated in  FIGS. 9 and 10  does not include the cover  5 . The tube member  2  is held in place without aid of a cover  5 . The stem  6   e  comprises four ribs  6   e ′ extending at ninety degrees to one another. The end cap  3  includes a detent  3   g  which one of the ribs  6   e ′ of the stem  6   e  engages. The end cap  3  also includes protrusions  3   h.  Two of the ribs  6   e ′ engage with these protrusions. To fit the tube member  2  to the stem  6   e,  the slot  2   d  is aligned with the stem  6   e,  which is pushed into the slot  2   d  with one of the ribs  6   e ′ aligned with the detent  3   g  of end caps  3 ,  3 ′. The two ribs  6   e ′ extending perpendicular to the rib  6   e ′ aligned with the detent  3   g  will first engage one side of the protrusions  3   h  and will then ride over those protrusions as the stem  6   e  is pushed further into the slot  2   d.  The ribs  6   e ′ then engage the other side of the protrusions  3   h,  securing the stem  6   e  in position in the tube member  2 . 
         [0052]    In the embodiment shown in  FIG. 9 , the collar elements  4 ,  4 ′ are joined together by a hinge  4   h,  which is preferably a live hinge formed during the moulding process which forms the collar elements  4 ,  4 ′, that is element of plastics material joining the two collar elements and permitting pivoting therebetween. In such an embodiment, the walls  4   e  distal from the hinge of the collar elements  4 ,  4 ′ are provided with co-operating holes  4   f  and pegs  4   f  respectively. 
         [0053]    To use the device  1 , a hole is bored in a rock face for instance and the device inserted into the hole. An electric current is passed through the electrical initiator to initiate the pyrotechnic material contained within the tube member  2 . Gas released from the pyrotechnic material and a force is therefore exerted on the end caps  3 , the force pushing the end caps  3  axially out of the tube member  2 . However, movement of the end caps  3  in the axial direction is constrained by the collars  4 , the sloping surfaces of which co-operate with the sloping surface of the bosses  6 ,  6 ′. The collars  4  are pushed outward against the wall of the hole into which the device has been inserted. The movement of the collars  4  and end caps  3  is not sufficient to allow the end caps to release from the tube member  2 , these components being held in place by the stem  6   e  of the rod member  6 . 
         [0054]    The directional gas pressure device of the invention offers significant advantages over those of the prior art, including that described in GB2468133. Not only is the device of the invention less costly to manufacture, because there is no need to provide any threaded elements or fasten together threaded elements, but the device allows filling with pyrotechnic material to take place separately of assembly of the device. This is a major step forward, since it allows factories already set up to fill pyrotechnic materials to do so without having to engage in assembly of the more complex aspects of the device. Conversely, the device of the invention allows another party not necessarily concerned with filling pyrotechnic material to assemble filled tubes and the other components of the device.