WO2002090874A1

WO2002090874A1 - Cartridge

Info

Publication number: WO2002090874A1
Application number: PCT/IB2002/001568
Authority: WO
Inventors: Luke Emmanuel Cronin; Stephanus Jacobus Van Vuuren
Original assignee: Rocktek Limited
Priority date: 2001-05-09
Filing date: 2002-05-09
Publication date: 2002-11-14

Abstract

A cartridge for containing a gas generating substance such as a propellant or explosive and suitable for use with small charge blasting methods for breaking hard materials such as rock in underground mining operations includes at least one formation for engagement by a cartridge removal means the formation including a hole to receive a string or hook, a female recess formation for engagement with a complimentary shaped male member at the end of a rod.

Description

CARTRIDGE

INTRODUCTION OF THE INVENTION

This invention relates to cartridges of the type used to contain gas generating substances for use in methods for breaking rock and other hard substances.

BACKGROUND TO THE INVENTION

In recent times the use of so-called "small charge blasting" techniques have received increasing attention particularly in the field of underground hard rock mining where the current prevailing mining method remains the so-called "drill and blast" method using explosives. In this latter method holes are drilled into rock to be broken, they are substantially filled with suitable explosive and the explosive is then initiated once the area (i.e. the mine) has been cleared. After removal of noxious gases and dust, entry to the blast area is permitted to facilitate removal of broken rock and the repetition of the process. Small charge blasting on the other hand often does not have the disadvantages of the drill and blast method. Here, a machine drills a hole into the rock to be broken and a pressurized working fluid, such as a gas, water, or foam, is released rapidly into a portion of the hole, usually the bottom portion. The pressurized fluid is typically generated by combustion of a propellant or explosive source, by electrical discharge into a conductive fluid, by inducing a rapid phase change or by mechanical compression or a working fluid. A stemming bar, gas introduction barrel or stemming material seals and stems the pressurized fluid in the hole bottom leading to fracturing of the rock. Small charge blasting can be highly mechanized and automated to increase productivity, can permit excavation machinery to remain near the face due to reduced fly rock discharge, and can have a seismic signature that is relatively small because of the small amount of blasting agent used in the blasting sequence.

In some types of small charge blasting the gas generating substance is placed in the hole and activated in situ. To place the substance it may be contained in a cartridge together with an initiator/activator.

A significant problem arises where activation/initiation for some reason, fails to take place. In such situations the cartridge must either be removed from the hole, which is often difficult, or otherwise it must be activated utilizing another method such as by secondary activation by the shock energy from a further amount of the substance placed in the hole and activated separately. This obviously takes time and holds up any continuous or semi continuous mining method that is in place.

OBJECT OF THE INVENTION

An object of this invention is to provide a cartridge suitable for use in small charge blasting the cartridge being easier to remove from a hole in the case of a misfire than are currently available cartridges. SUMMARY OF THE INVENTION

According to the invention a cartridge for containing a gas generating substance and suitable for use with methods for breaking hard materials is characterised in that it includes at least one formation for engagement by cartridge removal means.

Further according to the invention the cartridge is a cylindrical cartridge, is preferably elongated, and has an operatively inner end adapted to be nearest the bottom of a hole in which the cartridge is to be inserted and an outer end adapted to be remote from said hole bottom.

Still further according to the invention the formation is at or near the outer end of the cartridge.

Still further according to one aspect of the invention the formation is a hole through the cartridge, the cartridge being engageable by a cartridge removal means in the form of one of a locked member and an elongated flexible filament.

Still further according to another aspect of the invention the formation is one of a male and a female formation for engagement with a complimentarily shaped female or male member at the end of a rod which may be a stemming bar

Still further according to the invention the formation is a tapered male formation adapted to be engaged by a complimentarily shaped female formation at the end of the rod.

Still further according to the invention the engagement is by way of frictional engagement. This invention also provides for a cartridge as defined including a cartridge removal means engaged therewith.

The invention also provides a rod including a complimentarily shaped formation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments described by way of example only follow with reference to the accompanying drawings in which:

Figure 1 is a side elevation of a first embodiment of a cartridge according to the invention and located in a hole. Figure 2 is a side elevation of a second embodiment of a cartridge according to the invention and located in a hole.

Figure 3 is a side elevation of a third embodiment of a cartridge according to the invention. Figure 4 is an end elevation of the outer end of the cartridge of the third embodiment.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Three embodiments of a cartridge according to the inventions are shown in the accompanying figures.

In the first embodiment as shown in figure 1 a cartridge (1 ) is in the form of an elongated right circular cylindrical container (2) having a flat inner end (3) adapted to be located near the bottom (4) of a hole (5) in a working place (6) and a wedge-shaped outer end (7) adapted to be remote from the hole bottom (4). The container (2) is partially filled with a propellant material as is known in small charge blasting methods and the end (3) is closed off with a suitable flat end closure (8).

The wedge-shaped end (7) of the cartridge (1) is solid and includes a circular bore (9) extending there through between the two flat surfaces (10) forming the wedge-shape configuration.

The bore (9) is adapted to locate a suitable flexible member (11) which may be used to pull the cartridge (1) out of the hole (5) in the case of a misfire.

In the second embodiment as shown in figure 2 the cartridge (21) is substantially the same as that of the first embodiment and accordingly similar parts thereof have been given the same numerals as for the first embodiment. The container (2) of the cartridge (21) terminates in a frusto conical male configuration (22) having a small cone angle at its outer end. A rod (23) which may be a stemming bar (25) is provided with a complimentarily shape female formation (24). Both formations may include roughened surfaces or even surfaces which include small interlocking formations.

To remove a cartridge of this embodiment in a misfired situation the male configuration (22) may be located and engaged by the female configuration (24) at the end of an elongated stemming bar as withdrawing tool. Frictional engagement or the engagement of the small interlocking configurations allows the cartridge to be removed as withdrawal of the rod or stemming bar (25)

Figures 3 and 4 show a cartridge (31) of a different configuration and which comprises an elongated hollow right circular cylindrical container (32) having a flat inner end (33) closed off by a closure (34). The outer end (35) is also flat extending transversely to the axis of the cartridge and in the outer end surface (36) is a centrally located rectangular keyway (37). This keyway communicates with an undercut circular cavity (38) beneath the surface (36).

The formation formed by the keyway (37) and undercut cavity (38) may be engaged by a key (39) at the end of a stemming bar (40). The key (39) includes a flat rectangular portion (41) which is adapted to pass through the keyway (37), and undercut recesses (42) at each end of the key and separating it from the end (43) of the stemming bar (40) the recesses being to allow the key to be turned so that it engages in the undercut cavity (38). In this way the cartridge (31) may be engaged by the stemming bar (40) and withdrawn.

It is clear from the three embodiments described that the invention provides for a cartridge which may be withdrawn from a hole where the cartridge has for example misfired. This as has been explained above will result in a considerable time saving.

Other embodiments are envisaged within the scope of the invention including other shapes configurations and applications thereof.

Claims

1. A cartridge for containing a gas generating substance and suitable for use with methods for breaking hard materials is characterised in that it includes at least one formation for engagement by cartridge removal means.

2. A cartridge as claimed in claim 1 which is a cylindrical cartridge and has an operatively inner end adapted to be nearest the bottom of a hole in which the cartridge is to be inserted and an outer end adapted to be remote from said hole bottom.

3. A cartridge as claimed in claim 2 which is elongated.

4. A cartridge as claimed in any of the preceding claims in which the formation is at or near the outer end of the cartridge.

5. A cartridge as claimed in any of the preceding claims in which the formation is a hole through the cartridge, the cartridge being engageable by a cartridge removal means in the form of one of a locked member and an elongated flexible filament.

6. A cartridge as claimed in any of claims 1 to 4 in which the formation is one of a male and a female formation for engagement with a complimentarily shaped female or male member at the end of a rod which may be a stemming bar.

7. A cartridge as claimed in claim 6 in which the formation is a tapered male formation adapted to be engaged by a complimentarily shaped female formation at the end of the rod. 8. A cartridge as claimed in any of claims 1 to 4 in which the engagement is by way of frictional engagement.

9. A cartridge as claimed in any of claims 1 to 5 including a cartridge removal means engaged herewith.

10. A cartridge removal means as claimed in either of claims 6 or 7. 11. A cartridge substantially as herein described with reference to figures 1 or 2 or 3 and 4 of the accompanying drawings.

2. A cartridge removal means substantially as herein described with reference to either of figures 2 and 3 of the accompanying drawings.