WO2003075115A2

WO2003075115A2 - Initiator

Info

Publication number: WO2003075115A2
Application number: PCT/IB2003/000826
Authority: WO
Inventors: Immo Eurich Bock
Original assignee: Immo Eurich Bock
Priority date: 2002-03-07
Filing date: 2003-03-07
Publication date: 2003-09-12
Also published as: AU2003208504A1; WO2003075115A3; AU2003208504A8

Abstract

The invention provides an initiator for propellants or mixtures of propellants found in cartridges for use in breaking hard material such as rock or in ammunition, the initiator (11) including a combustion member (12) supported on a support frame (2) with the combustion member (12) including a pyrophoric material (13) adapted to be initiated by heat generated by an electrical current passing therethrough the configuration of the combustion member (12) being determined by required combustion characteristics.

Description

INITIATOR

FIELD OF THE INVENTION

This invention relates to an initiator and initiation system for use in the initiation of propellants and propellant mixtures.

BACKGROUND TO THE INVENTION

While the invention will be described primarily with reference to propellants as used in operations to break hard materials such as rock and concrete, this should not be considered as restricting the nature of the invention or its application in any way. For example the invention may be applied to initiating ammunition propellants.

Historically explosives have been used to break hard materials such as rock in the mining industry for example. More recently a considerable amount of research and development has been done on the replacement, or partial replacement, of explosives with propellants. There are a number of advantages to this including safer handling in transportation and operational safety particularly insofar as gas production is concerned. Propellants are flame sensitive and are best initiated with flame as opposed to detonators, as is the case with explosives. Explosive initiators tend to shock desensitize propellants. They also cannot be transported within the propellant cartridge without the propellant cartridges being classified as explosives. This condition also applies to "fuse heads" that consist of heating wires coated with a mixture of fuels and oxidizers.

A further problem with existing methods of initiating propellants is that they generally do not allow millisecond timing for the initiation of a number of charges at the same time. This is often essential for effective breaking of hard material such as rock.

OBJECT OF THE INVENTION

One object of the invention is to provide an initiator system for propellants, which system may be included within the cartridge and be safely transported and handled and which is effective in use.

SUMMARY OF THE INVENTION

According to the invention an initiator for propellants and mixtures including propellants comprises a combustion member including a suitable metal, stable at ambient temperature and adapted to be initiated by heat generated by an electrical current passing there through, the configuration of the member being determined by required combustion characteristics.

Further according to the invention the combustion member includes terminal members for connection to an initiator control energizer.- Still further according to the invention the combustion member may be connected in series or in parallel with a resistance the characteristics of which are determined by the required initiation timing characteristics.

Still further according to the invention, the required combustion characteristics include the stability of the combustion member at normal working temperatures, and the stability of the combustion member when carrying an electrical current of a minimum about ± 0,25 Amps.

Still further according to the invention the initiator includes a support frame for the member.

Still further according to the invention the configuration of the combustion member includes its specific cross sectional area and length.

Still further according to the invention the configuration of the combustion member may be in the form of one of a thin strip, and wire.

Still further according to the invention the combustion member may be shaped and/or profiled using a guillotine or laser profiling technologies.

Still further according to the invention the combustion member has a point the cross sectional area of which is less than that at any other point.

Still further according to the invention the combustion member may be one of a pyrophoric metal and of a pyrophoric metal with a suitable coating.

Still further according to the invention the combustion member may be a non- pyrophoric material substrate coated with a pyrophoric material and the non- pyrophoric material may be a substantially non-conducting material such as glass and ceramics. Still further according to the invention the pyrophoric metal includes at least one of magnesium, titanium, zirconium and hafnium.

The invention also provides a cartridge comprising a container, one of a propellant and a propellant mixture in the container and an initiator as defined in initiation association with the propellant.

Further according to this aspect of the invention the cartridge may be for use in breaking hard material or may be part of an article of ammunition.

An initiation arrangement comprises one or more cartridges as defined, which are connected in parallel or in series to an initiator control energiser.

A method of igniting a propellant comprising initiating an initiator as defined in contact with the propellant.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a plan of a first embodiment of an initiator according to the invention. Figure 2 is a plan of a second embodiment of an initiator according to the invention. Figure 3 is a schematic sectional elevation of a cartridge according to the invention; and Figure 4 is a schematic drawing of an initiation arrangement according to the invention. DETAILED DESCRIPTION OF THE INVENTION

The first embodiment of the invention as shown in figure 1 an initiator (1) for use in the initiating of propellants in a cartridge for the breaking of rock in underground mining applications is provided. The initiator comprises a U-shaped support (2) made from a non-conductive material such as plastics and having a base member (3) and two transverse side members (4).

Fixed to and extending between the two side members (4) is a rectangular thin strip (5) of a zirconium metal. The strip (5) is shaped and/or profiled using a guillotine or laser cutting technology whereby it is provided with a point in its length the cross sectional area of which is at a minimum in comparison with all other points in its length. The strip (5) is fixed by means of soldering, spot welding or a form of mechanical attachment such as crimping for example.

Electrical conductors (6) and (7) are connected by mechanical crimping to each end (8) of the combustion member (5).

The configuration (that is the length, width and thickness) of the combustion member (5) is determined by the combustion characteristics that are required to initiate the propellant with which the initiator (1) is in contact. Thus the cross- sectional area of the combustion member (5) must be such as to be able to carry a current of greater than 0,25 Amps without the combustion process being initiated. Furthermore the specific area of the member (5) must be sufficiently high to ensure deflagration commences sufficiently rapid and intensely to effect desired initiation of the propellant. It follows that the point of minimum cross sectional area is also that of maximum resistance and it is thus at this point that the initiating temperature is the highest and at which combustion will commence. Figure 2 of the drawings depicts a second embodiment of the invention. In this embodiment an initiator (11 ) has the same basic form as the embodiment of figure 1 having a support (2) with a U-shaped configuration with a base (3) and side members (4). The combustion member (12) differs from that of the first embodiment in that it comprises a strip of thin pyrophoric material (13) supported on a non-conducting substrate such as glass. Furthermore the ignition member (12) is in series with an internal, or external to the cartridge, resistor (14) the purpose of which will be more fully described below.

The initiator ( 1 )/( 11) is shown in figure 2 located in a cartridge (15). The cartridge is of known type comprising an outer casing (16) with closed ends (17) and (18). The initiator (1 ) is located near the end (18) and the cartridge is filled with a propellant material (19) in granular form such that the initiator (1) is embedded therein.

The initiator (1) is activated by the passing of a current therethrough which is sufficient to heat the member (5) using its own resistance to a temperature at which the member (5) ignites. On ignition the flame from the member (5) initiates the propellant (19).

Cartridges of this type may be wired in parallel as shown in the initiation arrangement (20) depicted in figure 4. This arrangement includes an energizer (21) and a line resistance (22). When the energizer is activated currents flow through the combustion members of the initiators (1). It will be appreciated that as the temperature of the initiators increases so does the resistance thereof. This factor allows current to be diverted to the initiator of lower temperature at any given moment. In this way the temperature rise of the initiators in parallel is substantially simultaneous as is thus ignition. Alternatively if the combustion members (5) of the initiators (1 ) are in series with resistances (14) of different values the combustion members (5) can be caused to heat up at different rates and thus ignite at different times. This allows very rapid sequential initiation of cartridges. The combustion members (5) can each consist of multiple initiators connected in series or parallel as determined by the operational requirements.

It is clear from what has been described above the invention provides an initiator that is not only effective in initiating propellants but is stable in non-operational situations. The initiator thus may be located in a propellant cartridge during transport and handling thereby obviating the need for inserting an initiator into a cartridge in operational conditions.

Other embodiments of the invention are envisaged within the scope thereof including other applications such as its application to ammunition and the like.

Claims

1. An initiator for propellants and mixtures including propellants comprises a combustion member including a pyrophoric metal, adapted to be initiated by heat generated by an electrical current passing there through, the configuration of the member being determined by required combustion characteristics.

2. An initiator as claimed in claim 1 in which the combustion member includes terminal members for connection to an initiator control energizer.

3. An initiator as claimed in either of claims 1 or 2 in which the combustion member may be connected in series with a resistance the characteristics of which are determined by the required initiation timing characteristics.

4. An initiator as claimed in either of claims 1 or 2 in which the combustion member may be connected in parallel with a resistance the characteristics of which are determined by the required initiation timing characteristics.

5. An initiator as claimed in any of the preceding claims in which the required combustion characteristics include the stability of the combustion member at normal working temperatures.

An initiator as claimed in any of the preceding claims in which the required combustion characteristics include the stability of the combustion member when carrying an electrical current of a minimum about 0,25 Amps.

7. An initiator as claimed in any of the preceding claims and which includes a support frame for the member.

8. An initiator as claimed in any of the preceding claims in which the configuration of the combustion member includes its specific cross sectional area and length.

9. An initiator as claimed in any of the preceding claims in which the configuration of the combustion member may be in the form of one of a thin strip and wire.

10. An initiator as claimed in any of the preceding claims in which the combustion member is shaped and/or profiled using a guillotine or laser profiling technologies.

11. An initiator as claimed in any of the preceding claims in which the combustion member has a point the cross sectional area of which is less than that at any other point.

12. An initiator as claimed in any of the preceding claims in which the combustion member is one of a pyrophoric metal and of a pyrophoric metal with a suitable coating.

13. An initiator as claimed in any of claims 1 to 12 in which the combustion member is a non-pyrophoric material substrate coated with a pyrophoric material.

14. An initiator as claimed in claim 11 in which the non-pyrophoric material is a substantially non-conducting material.

15. An initiator as claimed in claim 12 in which the mateirl is one of glass and ceramic.

16. An initiator as claimed in any of the preceding claims in which the pyrophoric metal includes at least one of magnesium, titanium, zirconium and hafnium.

17. A cartridge comprising a container, one of a propellant and a propellant mixture in the container and an initiator as claimed in any of claims 1 to 17 in initiation association with the propellant.

18. A cartridge as claimed in claim 17 adapted for use in breaking hard material.

19. A cartridge as claimed in claim 17 as part of an article of ammunition.

20. An initiation arrangement comprising at least one cartridge as claimed in any of claims 17 through 19 and connected to an initiator control energizer.

21. A method of initiating a propellant comprising initiating an initiator as defined in contact with the propellant as claimed in any of claims 1 to 16.