WO2006063369A2

WO2006063369A2 - Rock breaking cartridge

Info

Publication number: WO2006063369A2
Application number: PCT/ZA2005/000181
Authority: WO
Inventors: Edward Walenty Tota
Original assignee: NXCO International Ltd
Current assignee: NXCO International Ltd
Priority date: 2004-12-08
Filing date: 2005-12-08
Publication date: 2006-06-15
Anticipated expiration: 2007-06-08
Also published as: WO2006063369A3

Abstract

A rock breaking cartridge /1OA) which has a tubular housing (12A) with a closure (30A) which is releasably engaged with an opening at one end of the housing. Propellant (52) is contained within the housing. In one mode the closure is slidable within the housing.

Description

ROCK BREAKING CARTRIDGE

BACKGROUND OF THE INVENTION

[0001] This invention relates to a rock breaking cartridge.

[0002] As used herein the word "rock" includes rock, ore, coal, concrete and any similar hard mass, whether above or underground, which is difficult to break or fracture. It is to be understood that "rock" is to be interpreted broadly.

[0003] Various techniques have been developed for the breaking of rock using non- explosive means. Most of these techniques rely on the generation of high gas pressures to initiate a tensile fracture at the bottom of a relatively short drill hole in rock. If the force which is generated by the high gas pressure can be optimally used then the efficiency with which the rock is broken is increased.

[0004] High gas pressure, in turn, is dependent on a number of factors including an efficient sealing of the gas which is produced, in the hole. Effective sealing of the propellant contains the gas which is released by ignition of the propellant, at least initially, until an optimal pressurisation level has been reached.

[0005] Due at least to the aforementioned factors it is therefore important for a cartridge which contains the propellant, to be effectively sealed. This practical requirement is however associated with a disadvantage which is that, when the cartridge is to be transported, it becomes necessary to adhere to safety regulations which apply to high explosives as opposed to regulations which apply to propellants which, by way of comparison, are low energy substances. It is permissible to transport a propellant which is not confined, for example in the aforedescribed manner, in accordance with safety regulations which are less stringent than the regulations which apply to high energy explosives or confined propellants. [0006] The invention is concerned with a rock breaking cartridge which, at least partly, addresses the aforementioned situation.

SUMMARY OF INVENTION

[0007] The invention provides a rock breaking cartridge which includes a housing inside which is formed an enclosure, at least one opening into the enclosure, a closure which is releasably engageable with the opening, a propellant inside the enclosure, and means for igniting the propellant.

[0008] The housing may be of any appropriate shape and size but preferably comprises a tube. The tube may have at least one opening at one end. In one version of the invention an opposing end of the tube is permanently sealed. In a different form of the invention the tube has open opposed ends and a respective closure is releasably engageable with each opening.

[0009] The closure may be of any suitable kind and, for example, the closure may be engaged by means of a screw thread with the tube.

[0010] In one form of the invention each closure and the tube are formed with corresponding interengageable bayonet-type formations. For example the tube may have at least one groove on an inner wall which extends generally in a longitudinal sense with respect to the tube and at least one transverse locking formation, and the closure may be in the nature of a plug with at least one corresponding projection which is slidably engageable with a respective groove.

[0011] A tool may be provided for exerting a pushing and twisting force on the closure.

[0012] In another form of the invention at least one locking member is used, when required, to fix the closure to the housing. This may be done in any appropriate way. For example the locking member may be fixed to one of the housing and the closure and then be engageable with the other of the housing and the closure. In a variation the locking member is engageable with formations on the housing and closure which are brought into register. These formations may be holes and the locking member may be a pin or rod which is passed through the holes.

[0013] The cartridge may include, in respect of each closure, a cap which is slidably engaged with the housing and which, preferably, is located inside the enclosure adjacent the closure.

[0014] The cap may be cup-shaped and an end wall of the cap may abut the respective closure.

[0015] The means for igniting the propellant may be any suitable igniter and a lead for actuating the igniter may extend between an interface of the closure and, where applicable, of the cap, on the one hand and an inner wall of the housing on the other hand. The lead may for example be positioned inside a groove which is formed in an outer surface in a closure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention is further described by way of examples with reference to the accompanying drawings in which:

Figure 1 is a side view in cross section of a rock breaking cartridge according to the invention;

Figure 2 is a perspective view on an enlarged scale of a closure for use in the cartridge of

Figure 1 ;

Figure 3 is an end view of the cartridge shown in Figure 1;

Figure 4 is a view on a reduced scale of a tool for use with the closure; and Figures 5 and 6 show other cartridges according to the invention. DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] Figure 1 of the accompanying drawings illustrates a cartridge 10 according to the invention which includes a housing 12 which is made from a tube 14 of an appropriate length and diameter. The tube can be made of plastic or steel or any other tough material which will not easily rupture when subjected to high gas pressure.

[0018] The tube is open at opposed ends 16 and 18. Each end is formed with two diametrically opposed grooves 20 and 22 respectively which extend for a short distance on an inner surface 24 of the tube in its axial direction. Each groove terminates in a corresponding transverse locking formation 26 and 28 respectively much in the nature of a bayonet-type arrangement.

[0019] Closures 30 and 32 are respectively engageable with the ends 16 and 18. 20 Figure 2 illustrates in perspective the closure 30. The closure 32 has a similar construction.

[0020] The closure 30 is in the nature of a plug which includes a stout body 38 consisting of a substantially circular base 40 with diametrically opposed projections 42 and 44, and a centrally positioned upstanding rectangular section 46. The body 38 is insertable into the end 16 with a fairly tight fit. The projections 42 and 44 slide along the corresponding grooves 20 and 22 and then, if the body is turned the projections 42 and 44 slip into the locking formations 26 and 28 respectively.

[0021] The tube 14 forms an enclosure 50 which is occupied by a propellant 52. As used herein "propellant" is to be interpreted broadly to include a propellant, a blasting agent, an explosive, a gas-evolving substance or any similar energetic material which, when initiated, generates high pressure combustion products typically at least partly in gaseous form.

[0022] An igniter 54 of a kind which is known in the art and which therefore is not further described herein is positioned inside the propellant. A lead or igniter wire 56 extends from the igniter and through a groove 58 which is formed in an outer surface of the base 40 to a location which is external to the tube. This enables the igniter to be actuated, when desired. Again this aspect is known in the art and is therefore not further described herein.

[0023] The propellant 52 is located between opposed caps 60 and 62. The cap 60 has an end wall 66 which abuts the closure 30 and a side wall 68 which is slidably engaged with a relatively tight fit inside the tube 14. The cap 62 is for all practical purposes the same as the cap 60.

[0024] Figure 4 illustrates a tool 70 which includes a handle 72 and a fork-shaped formation 74 which can be fitted over the rectangular section 46 of a closure. By using the tool it is possible to exert a pushing force on the closure so that the projections 42 and 44 are moved to the ends of the grooves 20 and 22 and then to twist the closure so that the projections move into the respective locking formations. In respect of the closure 30 this can be done without interfering with the lead 56 which passes inside the groove 58.

[0025] During transport and storage the cartridge is kept in a mode in which the closures 30 and 32 are engaged with the tube 14 but the projections 42 and 44, on each closure, are not engaged with the respective locking formations. Consequently if the cartridge is accidentally initiated during storage or transport gas which is evolved by the propellant 52 can escape from the cartridge for the closures 30 and 32 are simply pushed out of the tube, by the gas pressure with a sliding action. An explosive release of the gas does not take place.

[0026] When the cartridge is to be used in a blast hole (not shown) the closures 30 and 32 are activated to place the cartridge in an operative mode. This is done in the manner described in that each closure is pushed inwardly so that the projections 42 and 44 can be engaged in bayonet-type fashion, with the corresponding locking formations. When this has been done the closures can no longer slide within the tubular housing. The cartridge then becomes a pressure-containment device which contains the gas which is evolved upon initiation of the propellant 52, until a relatively high pressure has been attained, at which point the cartridge ruptures. When this happens the wall of the tubular housing breaks, for the closures remain locked in position. The pressure containment makes the breakage of fractured or jointed rock more efficient than the breakage which is produced by a normal propellant cartridge where the gas can escape to cracks and joints in the rock before sufficient pressure has been reached in the cartridge.

[0027] The cartridge of the invention does not rely on the hole in the rock to contain the gas which is evolved by the propellant for the tube 14, itself, is a pressure containment device which acts largely independently of the characteristics of the rock in which the hole is located.

[0028] The tube 14 is relatively thick walled, for example with a wall thickness of 5mm or more, and is made of a tough yet malleable material. It is therefore capable of containing substantial gas pressure before rupturing, and of expanding into close contact with a wall of a hole in which the cartridge is placed.

[0029] The use of the releasable closures means that a potential high pressure cartridge can be transported and stored in a safe manner using normal transport and storage means and without complying with additional safety requirements which apply to high pressure explosives. The cartridge can rapidly be converted between its transport/storage mode and operative mode with ease, in an effective and reliable manner.

[0030] Figure 5 shows another cartridge 10A in two modes. A cartridge portion on the right is shown disassembled. A cartridge portion on the left is shown in an operative mode.

[0031] The cartridge has a tubular housing 12A and closures in the form of cup- shaped caps 3OA and 32A respectively which can fit with a frictional location onto respective ends 16A and 18A of the housing. [0032] Holes 80 and 82 are formed in the housing, near its ends, and in the closures, respectively.

[0033] For transport and storage purposes the cartridge is in a mode in which the caps are engaged with the housing but are not fixed thereto.

[0034] When the cartridge is to be used the closures are pushed home onto the respective ends and the various pairs of holes 80 and 82 are brought into register with each other. Small pins 84 are then pushed through the holes to lock the closures to the housing. The cartridge is then used in the same way as the cartridge 10 and, in use, exhibits the features which have been described.

[0035] Figure 5 shows that the caps 3OA and 32A fit over the respective ends of the housing 12A. It is also possible to shape the components so that the caps slide into the respective ends of the housing.

[0036] Figure 6 shows a variation 10B of the arrangement in Figure 5. A tubular housing 12B which contains propellant 52 is sealed at opposing ends by means of cup-shaped caps 88 which slide into the respective ends of the housing.

[0037] When the cartridge is to be used a relatively thick disk 90 is placed over a base 92 of each cap and is locked in position, when the cartridge is to be used, by means of a pin 94 which is passed through holes 96 in the housing.

Claims

1. A rock breaking cartridge which includes a housing inside which is formed an enclosure, at least one opening into the enclosure, a closure which is releasably engageable with the opening, a propellant inside the enclosure, and means for igniting the propellant.

2. A rock breaking cartridge according to claim 1 wherein the housing comprises a tube and the opening is at an end of the tube.

3. A rock breaking cartridge according to claim 2 wherein the closure and the tube are formed with corresponding interengageable bayonet-type formations.

4. A rock breaking cartridge according to claim 3 wherein the tube has at least one groove on an inner wall which extends generally in a longitudinal sense with respect to the tube and at least one transverse locking formation, and the closure is a plug with at least one corresponding projection which is slidably engageable with a respective groove.

5. A rock breaking cartridge according to claim 2, 3 or 4 which includes a cap which is slidably located inside the enclosure adjacent the closure.

6. A rock breaking cartridge according to any one of claims 1 to 5 wherein the means for igniting the propellant includes an igniter and a lead for actuating the igniter extends between an interface of the closure and a wall of the housing.

7. A rock breaking cartridge according to claim 1 or 2 which includes, for each closure, at least one locking member to fix the closure to the housing.

8. A rock breaking cartridge according to claim 7 wherein the locking member is .engageable with registering formations on the housing and the closure.

9. A rock breaking cartridge according to claim 8 wherein the formations are holes and the locking member is a pin which is inserted into the holes.

10. A rock breaking cartridge according to claim 7, 8 or 9 wherein each closure is cup- shaped.

11. A rock breaking cartridge according to claim 5 wherein the cap is cup-shaped with an end wall which abuts the enclosure.

12. A rock breaking cartridge which includes a tubular housing with opposed openings at first and second ends of the housing, first and second caps located in the housing respectively adjacent the first and second ends, a propellant inside the housing between the caps, an igniter in the propellant, a lead which extends to the igniter through one of the openings and through an interface between the adjacent cap and an opposing inner wall of the housing, and two closures which are respectively releasably engageable with the openings.

13. A method of using a rock breaking cartridge which includes a tubular housing, a propellant in the housing and a closure engaged with an opening at one end of the housing, the method including the steps of transporting and storing the rock breaking cartridge in a mode in which the closure is slidable relatively to the housing, and using the rock breaking cartridge in an operative mode in which the closure is locked in the housing.