Abstract:
An hydraulic expansion tube is provided which may be inserted into bore holes and expanded to break apart rock. An expandable tube is secured at its ends with end caps and sleeves which are carried on a support shaft. The end caps and sleeves form a tight interference fit with the ends of the expandable tube. Hydraulic fluid is ported through the support shaft into the interior of the expandable tube. The end caps and sleeves may be provided with threads to better grip the expandable tube and prevent it from pulling away from the end caps after repeated expansion. Additionally, an expandable sheath may be provided to surround the ends of the expandable tube to limit the expandable tube from flowing around the end caps when pressurized.

Description:
FIELD OF THE INVENTION 
     This invention relates to hydraulic expansion tubes which may be used in mining, construction and excavation. 
     BACKGROUND OF THE INVENTION 
     In mining, construction and excavation operations it is often necessary to break apart large portions of solid rock. Traditionally, surface pieces of rock could be broken away using rock chisels and/or hammers. In order to break apart larger portions of rock a wedge may be used to split the rock apart. However, these methods are both labour intensive and time consuming. 
     Since the advent of explosives, dynamite has often been used to break apart larger portions of rock. Typically, the dynamite is inserted into a bore hole that is drilled into the rock. When the dynamite explodes the pressure generated by the explosion or blast inside the bore hole splits the rock apart. Such explosions may be used alone or in conjunction with each other to break apart large portions of rock in a short period of time. 
     However, the explosive nature of dynamite makes it very dangerous to work with. Extensive safety precautions must be employed in the storage, transportation and use of dynamite. Additionally, when dynamite explodes it destroys itself, the detonating caps and much of the detonating wire. Accordingly, these components are non-reusable and must be replaced with each new use. Furthermore, the explosion of dynamite creates a shockwave that is both loud and potentially damaging to sensitive structures. As such, dynamite blasting is often prohibited in urban areas. 
     SUMMARY OF INVENTION 
     In accordance with an aspect of the present invention there is provided an expander, comprising a support shaft, a pair of sleeves received on the support shaft proximate either end of the support shaft, an expandable tube disposed about the support shaft and the sleeves, a pair of end caps proximate either end of the support shaft surrounding the expandable tube such that proximate each end of the support shaft an end cap and a sleeve sandwich said expandable tube so as to make an interference fit with the expandable tube, and a port for porting hydraulic fluid between said support shaft and said expandable tube. 
     In accordance with another aspect of the present invention there is provided an expander an described above further comprising an expandable sheath disposed about said expandable tube at each said end cap for minimizing expansion of said expandable tube over said end cap. 
     The present invention may be inserted into a bore hole to split apart rock. An advantage of the present invention is that is it quiet, reusable and does not generate an explosive shock wave. The absence of an explosion makes the present invention safer to use and better suited for use in urban areas. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be further understood from the following detailed description, with reference to the drawings in which: 
     FIG. 1 illustrates in cross-section a side view of an unexpanded expander in accordance with an embodiment of the present invention. 
     FIG. 2 illustrates in cross-section an enlarged side view of the left hand end of the unexpanded expander shown in FIG.  1 . 
     FIG. 3 illustrates an exploded view of the expander in FIG. 1 absent the sheathes and with a portion of the expandable tube cut away to expose the support shaft inserted there through. 
     FIG. 4 illustrates in cross-section an enlarged side view of the support shaft shown in FIG.  1 . 
     FIG. 5 illustrates in cross-section a side view of an expander of FIG. 1 when expanded and confined by a bore hole. 
     FIG. 6 illustrates in cross-section a side view of an unexpanded expander in accordance with a second embodiment of the present invention. 
     FIG. 7 illustrates in cross-section a side view of the expander of FIG. 6 when expanded and not confined by a bore hole. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referencing FIGS. 1 to  4 , an expander  10  comprises a support shaft  12  with a pair of sleeves  14   a ,  14   b  received thereon proximate either end  15   a ,  15   b  of the shaft. An expandable tube  16  is disposed about the support shaft and the sleeves  14   a ,  14   b . The tube is preferably elastic, being preferably formed of rubber, and most preferably nitrile rubber. A pair of sheathes  18   a ,  18   b  near each end of the support shaft  12  surround the rubber tube and a pair of end caps  20   a ,  20   b  proximate each end of the shaft surround the rubber tube and a portion of the sheathes  18   a ,  18   b . The sheathes have some elasticity, but are preferably less elastic than the rubber tube. The sheathes may be made of nylon. The ends of the support shaft are threaded and receive end nuts  24   a ,  24   b . Nut  24   a  has a tab  26  with an opening  28  therein. 
     The support shaft has an hydraulic port  30  through end  15   a  which connects with an input conduit  32   a  that ends in radial stub conduits  34   a  which open to the outside of the shaft. The end  15   b  of the shaft  12  has a bleed port  38  connected to a bleed conduit  32   b  which ends in radial stub conduits  34   b  which open to the outside of the shaft. A bleed end cap  40  seals the bleed port  38 . A series of O-rings  42  provide seals against hydraulic fluid leakage. 
     As best seen in FIG. 2, a portion  46  of the exterior of each sleeve  14  is threaded and a portion  48  of the interior of each end cap  20  is also threaded. The sleeve and end cap are configured so that these threaded portions mate so that the sleeve may be threaded to the end cap. A further portion  50  of the end cap  20  is threaded with a thread opposite in orientation to that of the threaded portion  46  of the sleeve, and it will be noted that each end of the rubber tube is sandwiched between an end cap and sleeve at their threaded portions  46 ,  50 , respectively, in order that the grip on the tube by the end cap and sleeve combination is enhanced. 
     The end cap  20  terminates in an apical unthreaded lip portion  52  with a rounded edge  53  under which the sheath  18  extends. The outside surface of the end cap  20  tapers from a wide apex  54  at lip portion  52  to a narrow base  56 . The end cap also has a shoulder  58 . 
     The sleeve  14  has a basal flange  60  which abuts against shoulder  58  of the end cap and an apical interior radially stepped portion  62 . The sleeve  14  is spaced from the shaft  12  along portion  62  and portion  62  extends over the radial stub conduits  34  of the shaft. The sleeve  14  also has a shoulder  68  which abuts a corresponding shoulder  70  of shaft  12 . 
     Turning to FIG. 5, in operation, expander  10  may be inserted in a bore hole through rock. Pressurised hydraulic fluid is then injected into the expander through port  30 . The fluid squirts through conduit  32   a  and stub conduits  34   a  exiting the support shaft  12  at portion  62  of sleeve  14   a . Portion  62  of the sleeve redirects the fluid flow so that the pressurised fluid does not squirt directly onto the rubber tube  16  (which could damage the tube). The fluid fills the annular space  66  between the support shaft and the rubber tube and the fluid pressure forces the medial section of the rubber tube between the end caps  20   a ,  20   b  to expand against the sides of the borehole. It has been found that pressures of 2,000 to 10,000 psi are typically required to fracture the rock through which such a borehole extends. Once the rock fractures, the pressure quickly drops as the rubber tube is freed to expand; this pressure drop may be used as a feedback signal to cut off the hydraulic fluid supply. It is also contemplated that several expanders  10  may be connected in series (by coupling the bleed port  38  of one expander to the hydraulic port of the next through a suitable coupling) to extend the operational length. 
     While the rubber tube  20  expands, each sheath  18   a ,  18   b  acts to minimize expansion of the expandable tube  16  over the outside surface of the end cap  20   a ,  20   b  with which it is associated. This greatly reduces fatigue of the rubber and therefore prolongs the life of the rubber tube  16 . 
     After the rock has been fractured and the hydraulic fluid cut off, the expander  10  may be removed from the borehole by a suitable hook received through opening  28  in tab  26 . 
     When expander  10  is first hooked up to an hydraulic supply, the expander will contain air rather than hydraulic fluid. Pressurising this air to the working pressures of the expander could result in dangerous failure. Consequently, after first hooking the expander to an hydraulic supply, bleed end cap  40  is removed and low pressure fluid is introduced into the expander. This forces the air out of the expander through bleed conduit  32   b . Once fluid begins to emerge from bleed port  38 , the bleed end cap  40  may be reinserted to close bleed port  38 . 
     The size of the bore hole is such that the wide apex  54  of the end caps makes a close tolerance fit with the sides of the bore hole. This further assists in ensuring that the rubber of the tube does not expand around the outside of the end caps. Lip  52  is provided with a rounded edge  53  to prevent sheaths  18  and expandable tube  16  from being pinched and damaged during expansion. The end caps are tapered from their wide apices to ease manipulation of the expander in the borehole. 
     The interference fit that the threaded end cap and sleeve portions make with the ends of the rubber tube provides a strong bite on the rubber tube which minimized its creep away from the base  56  of the end caps with repeated use. 
     The expander may be assembled as follows. First the end caps  20   a ,  20   b  are turned while they are pressed against the ends of the rubber tube so that they “screw” onto the tube. Next the support shaft is inserted through the rubber tube. After this, each sleeve  14   a ,  14   b  is screwed into its end cap  20   a ,  20   b  until the shoulder  68  of the sleeve abuts the shoulder  70  of the shaft  12 . This pinches the rubber tube between the sleeves and end caps. Lastly the end nuts  24   a ,  24   b  are threaded to the threaded ends  15   a ,  15   b  of the shaft  12 . When it is necessary to replace a fatigued rubber tube  16 , this process is reversed. 
     Optionally, the bleed end cap  40  may be replaced by a spring loaded valve which may be opened by a user applying external pressure. Optionally, instead of tapering the end caps, they may simply have an enlarged apical lip. 
     The nylon sheathes have the disadvantage that they may slowly break down in a caustic environment. Optionally, therefore, the nylon sheathes may be replaced with a coil spring or by a flat steel spring. Further, the sheathes may optionally not be overlapped by the end caps but, instead, terminate at the apical edge of the end caps. This option is not preferred, however, as sheathes so positioned provide less protection against the rubber tube expanding over the outside of the end caps. 
     A simplified embodiment of an expander made in accordance with this invention is illustrated in FIG.  6 . Turning to FIG. 6, wherein like parts have been given like reference numerals, expander  100  has sleeves  114   a ,  114   b  which are not threaded. Each sleeve abuts basal portion  156  of an end cap  120   a ,  120   b . The end caps  120   a ,  120   b  are also not threaded. And no sheathes are employed in expander  100 . Expander  100  is assembled by placing sleeves  114   a ,  114   b  over the end portions of the support shaft  12  until the shoulders  68  of the sleeves abut the shoulders  70  of the shaft  12 , pushing the rubber tube  16  onto the shaft  12  then forcing on the end caps  120   a ,  120   b . In forcing an end cap overt the rubber tube, air will become trapped between the end of the rubber tube and the basal portion  156  of the end cap. To avoid this potential problem, preferably a bleed conduit (not shown) is provided through the base of the end cap to allow this air to escape. After the end caps are in place, the end nuts  24   a ,  24   b  may be threaded to the assembly. 
     Referencing FIG. 7, after assembly, hydraulic fluid may then be injected into port  30 . The fluid will squirt through stub conduits  34   a  and be redirected by apical portion  162  of sleeve  114   a . The fluid in annular space  66  will then cause the rubber tube  16  to expand. The tight interference fit between the sleeves  114   a ,  114   b  and the end caps  120   a ,  120   b  minimizes creep of the tube away from the basal portions  156  of the end caps. 
     Other modifications will be apparent to those skilled in the art.