AU2002100905B4 - Cartridge for breaking or fracturing hard materials - Google Patents

Description

P00/0lI Regulation 32B

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR AN INNOVATION PATENT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: ROCKTEK LTD Lot 333, Harries Way, Pinjarra, Western Australia 6208, Australia Edward TOTA Nigel ROGERS Griffith Hack, Patent and Trade Mark Attorneys, 6th Floor, 256 Adelaide Terrace, Perth, Western Australia, 6000.

Complete Specification for the invention entitled: CARTRIDGE FOR BREAKING OR FRACTURING HARD

MATERIALS

Details of Parent Application for Divisional Applications: Australian Patent Application No. 2001235240 22 February 2001 The following is a full description of this invention, including the best method of performing it known to me:- Cartridge for Breaking or Fracturing Hard Materials Field of the Invention 10001] The present invention relates to a cartridge shell and a corresponding cartridge for blast holes for the purpose of fracturing hard materials. The invention further relates to a method of use of such a cartridge and in particular a method of charging blast holes with the cartridge.

Bacground of the Jnvention [0002] A typical cartridge shell for a blast hole is in the form of a cylindrical tube closed at both ends. Some cartridges may contain only an energetic substance while others may contain both an energetic substance and an initiator. The cartridge will be inserted to reside near the toe of a blast hole drilled or otherwise formed in a rock or other hard material to be fractured. The hole may then be stemmed with a particulate stenuning material. When the energetic material in the cartridge is initiated there is a rapid generation of gas and thus a rapid build up of gas pressure near the toe of the hole.

Provided that the gas generated is contained for a short period of time the resulting gas pressure may cause fractures to be propagated from the hole through the hard material.

100031 The efficiency and effectiveness of this process is largely determined by factors such as the provision and quality of a gas seal formed on an end of the cartridge nearest the collar of the blast hole and the ability to hold the seal in position. Clearly if the seal is poor, gas will escape around the seal thereby reducing gas pressure as well as the rate of gas pressure increase. Further, the escaping gas has adverse effects in terms of ejecting stemming. from the blast hole, generation of recoil and producing flyrock. However, even if the seal is one of high integrity, if the seal is not held firmnly in place and is able to be pushed back toward the collar of the hole then the physical volume of the confined space within the hole in which the gas acts increases, thereby decreasing the gas pressure.

Summga of the Invention [00041 It is an object of the present invention to provide a cartridge and associated 2 cartridge that in use may assist in alleviating the above noted deficiencies.

[00051 According to one form of the present invention there is provided a cartridge for use in breaking or fracturing hard material by the insertion of said cartridge followed by a particulate stemming material in a hole formed in the bard material, said cartridge including a shell, an initiator and a quantity of propellant, said shell having a main body, and first and second ends with a volume being defined within said main body between said first and second ends and containing said quantity of propellant, said second. end of said shell including a surface for exerting a radial compressive force on said particulate stemming material when said propellant is ignited; said initiator disposed in said propellant and provided with a lead which passes through a hole fanned either in said surface or through said first end.

[0006] Preferably said surface is a surface of a member which narrows in a direction along said main body away from said first end.

10007] Preferably said shell, for a length between a point where the surface of said member commences to narrow said first end, has a constant outer diameter.

[00081 Preferably said member is fanned separately of said main body and attached to said main body.

[00091 Preferably said surface is composed of first and second planar surfaces which are inclined toward each other in said direction along said main body away from said first end.

Brief Description of the Drawing 10010] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an exploded sectional view of a cartridge shell in accordance with the present invention; Figure 2 is a bottom view of an end cap incorporated in the cartridge shell; Figure 3 is a view of section A-A of Figure 1; Figure 4 is a view of sectio P 1 -Pi of Figure 1; Figure 5 is a view of section P 5 2 of Figure 1; Figure 6 is a view of section PI-Pi of a second embodiment of the cartridge shell; Figure 7 is a view of section P2-? 2 of the second embodiment of the cartridge shell; Figure 8 is a section view of an upper end of a third embodiment of the cartridge shell; Figure 9 is a section view of a bottom part of the cartridge shell of Figure 1 showing the layout of an initiator and initiator lead; Figure 10 is a section view of a fourth embodiment of the cartridge shell; Figure 11I is a section view of a bottom part of a fifth embodiment of the cartridge shell; Figure 12 depicts one method of use of a cartridge made from a cartridge shell in accordance with embodiments of this invention; Figure 13 illustrates the second method of use of a cartridge incorporating the cartridge shell in accordance with embodiments of this invention; and, Figure 14 illustrates a further embodiment of a cartridge shell/cartridge.

Detailed Descri ~tion of the Preferred Embodiments 100111 Figures 1-5 depict a first embodiment of the cartridge shell 10. The cartridge shell comprises a main body 12 for holding an energetic material (not shown). The shell has a first end 16 and an opposite second end 18. The first end 16 is generally planar and in effect forms a planar base for the shell 10. The second end 18 however is tapered to form a point or wedge-like member [0012] The tapering of the second end 18 is configured so that an area of the second end 18 measured in a plane transverse to a longitudinal axis of the main body 12 reduces in a direction to the first end 16 to the second end 18 ie, the member 20 narrows in a direction along the main body 12 away from the end 16. Thus, with reference to Figures 4 and the area of the second end 18 in plane P 2 is reduced in comparison to the area measured in plane P I.

[00131 The second end 18 can take one of a number of different specific shapes. In Figures 1, 4 and 5 it is seen that the second 18 is in the form of two inclined surfaces 22 and 24 that converge toward each other. However, in an alternate embodiment the second end 18 can be in the form of a conical frustum. This is depicted in Figures 6 and 7 which illustrate a transverse section of the second end 18 through planes P 1 and P 2 respectively.

In yet a further embodiment depicted in Figure 8, the second end 18 is in the form of a chisel point. Of course other shapes are possible such as, but not limited to, three, four or five sided prisms.

[0014J Ideally the main body 12 and the second end 18 would be formed integrally and from a plastics material. However it is possible for the second end 18 to be made separately from the main body 12 and if so, the two components can then be attached together. The main body 12 will conveniently be in the form of a cylindrical tube as depicted in Figure 3 showing section A-A of Figure 1, [00151 Main body 12 has an opening 26 at the first end to allow filling of the shell with an energetic material. A closure in the form of a cap 28 is provided for insertion into and closure of the opening 26. As is apparent from Figures 1, 2, 9 and 10 the cap 2 8 has a tubular portion 29 which is open at one end 31 and closed at an opposite end by a base 33.

The cap 28 is press/interference fitted into the opening 26 with end 31 disposed inwardly of the end having the base 33. This forms a line or zone of weakness at the first end 16.

[0016] An aperture 30 is formed centrally through the cap 28 to allow an initiator such as an electric match 32 (see Figure 9) to be pushed into the main body 12. A lead 34 from the match 32 passes through aperture 30 for coupling with an electric power source. A volume 14 is defined within the main body 12 between the ends 16 and 18, and more particularly between the cap 28 and member 20, for holding the propellant.

[00171 In an alternate embodiment depicted in Figure 10 the outer surface 36 of the shell near the first end 16 is provided with a recess 38 for seating the initiator lead 34. The recess includes a first length 40 provided on the main body 12 and a second length 42 provided in the cap 28. The cap 28 is orientated when inserted into the main body 12 so that the lengths 40 and 42 of the recess 38 are in alignment. When the electric match 32 is inserted through the aperture 30 the lead 34 can be seated in the recess 38 to provide it with some protection from accidental damage or cutting when the shell 10 is inserted into a blast hole. In a flurther variation the length 40 of the recess 3 8 can be extended along the main body 12 to at least a point where the wedge-like member 20 commences.

100181 In a fturther variation depicted in Figure 11, the aperture 30 is placed in the point or wedge-like member 20 rather than in cap 28. In this embodiment the shell 10 can also be provided with an internal passageway 35 through which the lead 34 passes to deposit the initiator 32 near the first end 16 inside the main body 12.

[0019J Figure 12 illustrates one method of use of the shell 10. The volume 14 of the shell 10 is filled with an energetic substance such as a propellant to form a cartridge IlOc.

The cartridge 1 Oc is inserted into a blast hole 46 formed in hard material 47 with first end 16 first so that the first end 16 is adjacent a toe 48 of the hole. Accordingly the second end 18 faces or is directed toward a collar 50 of the hole. Next, a quantity of particulate stemming material 52 is placed in the hole 46. Typically this will be done by blowing.

The stemming material 52 is blown into the hole 46 to a level below the free face 54 of the hard material 47 in which the hole 46 is fonned. The stemming 52 is then mechanically held in the hole 46.

100201 In the embodiment of Figure 12 the mechanical holding is achieved by inserting a stemming bar 56 into the hole 46 so that one end 58 of the stemming bar rests on the stemming 52 and an opposite end 60 of the stemming bar extends from the fr-ee face 54. A cup 62 is placed over and cradles end 60. An opposite side of the cup 64 is formed with a planar base and supports an acrow prop 66. The acrow prop 66 is extended in length or otherwise jacked so that its opposite end 68 abuts a wall 69 disposed opposite the free face 54.

100211 By connecting lead 34 with an electrical power source, the initiator 32 generates a high temperature flame to initiate the propellant or other energetic material within the cartridge l Oc. The gas generated upon initiation initially bursts through the main body 12 about the line of weakness formed by the coupling of the cap 28 to the main body 12. The increase in gas pressure can tend to force the cartridge 10c toward the collar 50 of the hole 46. As this occurs, the point or wedge-like member 20 acts on the stemming 52 to increase the radial compressive force on the stemming material in an annular-like region between the peripheral of the second end 18 and the adjacent portion of the surface of hole 46 thereby increasing the sealing effect of the stemming material 52. The stemming material 52 is prevented from blowing out of the hole 46 by action of the mechanical retention provided by the stemming bar 56 and acrow prop 66.

[0022J The sealing effect of the sternuing material 52 is enhanced by forming the stemming material 52 from a mixture of a dry binding agent, fines, and coarse material. It has been found that fly ash is a particularly beneficial binding agent and the mixture containing fly ash has a tendency to set when blown under pressure into the hole 46. The binding agent and fines comprises particulate solids of mesh size less than about 1mm.

The coarse material within the stemming aggregate contains particles of mesh size up to about 6mm. Binding agents other than fly ash can be used in the stemming material such as waste products from smelters, or fines containing cementitious material.

10023] lIn an alternate method for stemming the hole 46, after the cartridge 10c has been inserted into the hole a volume of a liquid or gel 70 is inserted into the hole 46 to fill any space between the outer surface of the cartridge 10Oc and the surface of the hole 46 and provide a liquid or gel layer 72 between the particulate stemming material 52 and the cartridge l Oc. The gel 70 assists in sealing the hole 46 to prevent the escape of gases upon initiation of the energetic material held within the cartridge 10Oc, In all other respects, the method depicted in Figure 13 is the same as that depicted in Figure 12.

[0024] The use of the stemming material 52 either by itself or in conjunction with the liquid/gel 70 provides a seal of high integrity that substantially limits the escape of gas.

The mechanical retention of the stemming by use, in these embodiments, of the stemming bar 56 and the acrow prop 66 prevents the stemming 52 being displaced toward the collar of the hole 50 thus maintaining relative constant the volume of the hole 46 within which the gas operates.

100251 Now that embodiments of the present invention have been described in detail it will be apparent to those skilled in the relevant art that numerous modification and variations may be made without departing from the basic inventive concepts. For example, second end 18 of the shell 10 can be formed with a circumferential rebate 74 as depicted in Figure 14 for seating one end of a sleeve or tube 76 which can be filled with the stemming material 52. Obviously, the tube or sleeve 76 may also be formed as part of (le, integrally with) the main body 12. In such an instance when the cartridge 10c: is in use in a hole 46 with the member 20 facing the collar 50 of the hole and the hole stemmed with particulate stemming material, the tube or sleeve 76 will be filled with stemming material 52 so that in effect stemnming material 52 is contained between an inner surface of the shell and the member 20 as depicted in Figure 14.

(00261 Also, end 58 of the stemming bar can be formed with a point, taper or wedge-like member 78 as shown in phantom in Figures 12 and 13 to assist in the radial spreading and compaction of the stemming material 52 against the sides of the hole 46 thereby increasing the sealing effect.

[00271 All such modifications and variations are deemed to be within the scope of the present invention the nature of which is to be determined from the above description and the appended claims.

Claims (4)

1. A cartridge for use in breaking or fracturing hard material by the insertion of said cartridge followed by a particulate stemming material in a hole formed in the hard material, said cartridge including a shell, an initiator and a quantity of propellant, said shell having a main body, and first and second ends with a volume being defined within said main body between said first and second ends and containing said quantity of propellant, said second end of said shell including a surface for exerting a radial compressive force on said particulate stemming material when said propellant is ignited; said initiator disposed in said propellant and provided with a lead which passes through a hole formed either in said surface or through said first end.

2. The cartridge according to claim 1 wherein said surface is a surface of a member which narrows in a direction along said main body away from said first end.

3. The cartridge according to claim 2 wherein said shell, for a length between a point where the surface of said member commences to narrow and said first end, has a constant outer diameter.

4. The cartridge according to claim 2 or 3 wherein said member is formed separately of said main body and attached to said main body. The cartridge according to any one of claims 1-4 wherein said surface is composed of first and second planar surfaces which are inclined toward each other in a direction along said main body away from said first end. DATED this day of 2002 ROCKTEK LTD by its Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia.