EP1995551A1

EP1995551A1 - Igniter/Initiator

Info

Publication number: EP1995551A1
Application number: EP07108759A
Authority: EP
Inventors: Mikael Strohmaier
Original assignee: Saab AB
Current assignee: Saab AB
Priority date: 2007-05-23
Filing date: 2007-05-23
Publication date: 2008-11-26

Abstract

Igniter/initiator comprising a housing (4) with a through opening containing a starter module comprising a means of igniting a primary explosive, two or more tubular explosive modules (5,6,7) piled on each other and having an outer size and shape suited to the inner size and shape of the housing, each packed with an explosive, one explosive being a primary explosive, and having an inner section and height suited to contain the intended amount of explosive, a cover attached to the open end of the housing, the starter module being accessible from the outside.

Description

The present invention concerns an igniter/initiator.

BACKGROUND OF THE INVENTION

An igniter or initiator, blasting cap, detonator, in the following called igniter, is used for igniting, initiating or detonating an energetic device, such as main charge of a warhead or a pyrotechnic device. The igniter conventionally consists of a housing having an open cavity containing an explosive or two or more layers of different explosives. The most sensitive explosive, the primary explosive, is arranged at one end of the housing and is in contact with a means of initiating, such as an electric wire, a bridge wire igniter, a flex card, a capton film or some other means. Next to the primary explosive, on the opposite side of the initiating means, a less sensitive explosive may be arranged, such as a secondary explosive or a booster charge. The initiating means starts an explosive train by igniting the primary explosive, which ignites or detonates the secondary explosive and in the end ignites or initiates the main charge.
Different igniters are required to ignite different main charges. Some igniters may comprise within the housing only a primary explosive. Some may contain two or more layers of explosive. Some igniters contain small amounts of the different explosives, some contain larger amounts. Further different kinds of igniting means are used on the igniters. All these different types of igniters must be available for mounting.
To meet these requirements a vast amount of the different types of igniters must be produced and stored. This requires not only much storage space but the pressing of the different explosives against each other in an igniter always involves a certain risk.

OBJECTS OF THE INVENTION

It is therefore an object to make it possible to produce and store a smaller amount and fewer types of igniters.
Another object is to achieve less expensive igniters.
Still another object is to achieve a simplified production line.
A further object is to decrease the risk at producing igniters.

SHORT DESCRIPTION OF THE INVENTION

These objects are achieved by the present invention by producing the igniter in the form of modules. The igniter is produced by assembling the desired modules. This may take place any time before the igniter is to be used.
Thus, an igniter system comprises, as different parts or modules, tubular housing modules open at one or both ends. The housing modules are for instance made of metal or plastic. Further a series of tubular explosive modules containing explosive and having essentially the same outer shape and size as the inner section of the housing modules. These tubular explosive modules may have differing inner sections and/or heights and may all contain the same kind of explosive or may contain different kinds of explosives. Finally a series of starter modules to fit the open end of the housing and containing different means of ignition, such as electric wire, a bridge wire igniter, a flex card or a capton film. The starter modules have an end surface comprising connecting means intended to be connected to a device delivering an initiating signal, such as laser energy or an electric current.
A tubular explosive module comprises a tubular sleeve with the same outer shape and form as the inner shape and size of the housing module into which it is intended to be inserted. The sleeve is filled with an explosive. The sleeve is suitably made of metal or plastic.
The explosive modules comprise primary explosive modules where the sleeves are filled with a primary explosive. The same type of explosive may be used in other explosive modules, booster modules, where the primary explosive is compacted to a higher density and thus is made less sensitive.
The inner section and height of sleeves of the tubular explosive modules decide the amount of explosive to be enclosed therein. However, the explosives may also be packed to different densities inside the module and in this way identical tubular modules may contain different amounts of the same kind of explosive.
An igniter is produced by assembling the modules, placing the explosive containing modules inside the housing module, one of the explosive modules containing a primary explosive. The primary explosive is arranged at one end of the pile of modules and outside this module a starter module is arranged. If the housing is closed at one end, the explosive containing modules are piled against the closed end, the primary module last, with the starter module thereafter with the connecting means accessible from the open end of the housing module. Possibly a filling material, such as a polymer or glue, is used to fill out open spaces within the housing and to stabilize the pile of modules. Thereafter the open end of the housing is closed partly to hold the modules securely within the housing. The connecting means of the starter module must remain accessible. The closing of the housing end may be performed by bending the tubular end inwards against the starter module, by welding or soldering, for example.
In the case where the housing is open at both ends, preferably one opening has a smaller section than the inner section of the housing. When assembling an igniter, the starter module is inserted first with the end surface comprising connecting means arranged against this smaller opening and with the connecting means accessible through the opening. Thereafter the primary module is inserted, followed by the other explosive modules, where after the large opening is closed, such as by welding a sheet metal against the housing. The end having the smaller opening may also be sealed, if necessary. However, the connecting means must remain accessible from the outside of the igniter.

SHORT DESCRIPTION OF THE DRAWINGS

Fig 1 is a schematic sectional view through a known igniter.
Fig 2 is a schematic sectional view through modules in an embodiment of an igniter system according to the invention.
Fig 3 is a sectional view showing an embodiment of an assembled igniter according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is in the following described with regard to a cylindrical igniter having a circular section. However, the section of the housing modules and the modules to be inserted into these may be square, rectangular, star shaped, elliptic or any other form suited to the device to be ignited.
Fig 1 shows a conventional igniter comprising a cylindrical sleeve 8 containing two different explosives 6 and 7 and an insulating glass mass 10 filling up the rest of the sleeve. Between the explosive 6 and the mass 10 there is an initiating layer in contact with a wire or bridge 9 passing through the mass 10. The igniter also comprises a cylindrical housing into which the sleeve is inserted.
The embodiment of an igniter system of the invention shown on Fig 2 comprises the same type of cylindrical housing 4 as the conventional igniter on Fig 1. In this case the housing is closed at one end and open at the second end. It is however possible to have housing modules that are at least partly open also at the second end. Further it comprises three modules 1, 2 and 3 in the form of small tubes containing different kinds of explosives 5, 6, 7 and having the same outer diameter as the inner diameter of the housing module 4. The tubes have different wall thicknesses and thus different inner diameters and the amount of explosive in each tube is therefore different. The module or tube 1 also comprises an igniting module 11 built into the tube 1.
The embodiment of an assembled igniter of the invention shown on Fig 3 comprises three tubular modules T-4, T-5 and T-6, filled with different amounts and different kinds of explosives. Module T-7 is a cap through which electrical wires are threaded. Module T-3 is a bridge or thread and module T-2 is a part keeping modules T-4 to T-6 together. Module T-8 is the cylindrical housing which has been closed or sealed such as by bending the upper part of the wall inwards to fasten the Module T-7 and hold it against the other modules.
If necessary the modules are held together within the housing module with the use of a filling material, such as a glue or a plastic, which fills out empty spaces between modules.
In the case of a housing module having a small opening at the second end, the module T-7 having protruding electrical wires as connecting means is arranged at the second end, followed by the other modules. The first open end is closed by for instance welding a plate to this end.
It is possible to combine two or more of the modules to a combined module. In fig. 2 module 1, containing the primary explosive, and the starter module I 1 have been built together to a combined primary-starter module.
To have igniters of the known technique available which contain:

1) two different kinds of primary explosive,
2) two different kinds of secondary explosive,
3) three different amounts of each kind of explosive and
4) three different kinds of igniting means

To be able to produce any of these 36 types of igniters, according to the present invention, it is necessary to produce:

a) 6 tubular modules containing primary explosive,
b) 6 tubular modules containing secondary explosive,
c) 3 igniting modules, and
d) 1 housing module,

In this way it is possible to assemble any type of igniter using only a few modules. All the mentioned 36 types of igniters will not be used to the same extent, but it is necessary to have all of them available. Using the present invention not so much explosive must be stored in igniters that may never be used. Should one type of explosive module be consumed quickly, it is possible to produce new modules of only that type to again be able to assemble all necessary types of igniters.
The invention is not limited to the types of igniters discussed above. For instance, the modules may have any suitable shape and size. Also the igniters may be intended for igniting or initiating different kinds of energetic devices, such as warheads or pyrotechnic devices. The invention comprises all possible modifications within the scope of the claims.

Claims

Igniter/initiator for an energetic device, having a housing with an open cavity containing two or more layers of explosives, one of the explosives being a primary explosive, a cover attached to the open end of the housing and a means of igniting the primary explosive, characterized in having inside the housing a starter module and two or more tubular modules piled on each other and having a form and outer size to fit into the housing, each tubular module packed with one of the explosives and having an inner size suited to contain the intended amount of explosive.
Igniter/initiator according to claim 1, characterized in that the housing and the modules have an elliptic or circular section.
Igniter/initiator according to claim 1 or 2, characterized in that it is intended for a warhead.
Modular igniter/initiator system comprising tubular housing modules, being open at one end or both ends, tubular explosive modules having a fraction of the height of the housing modules, having essentially the same outer form and section as the inner form and section of the housing modules and having differing inner sections and/or heights, filled with different kinds of explosives, starter modules having an end surface comprising connecting means and comprising means of igniting an explosive contained in a tubular explosive module, such that an igniter/initiator may be assembled by piling in a housing module two or more tubular modules with a starter module at one end.
System according to claim 4, characterized in that the modules have an elliptic or circular section.
Process of producing an igniter/initiator, comprising the steps of
a) providing a tubular housing module, having a through opening and being open at one end and closed at the other end,

b) providing two or more tubular explosive modules having a fraction of the height of the housing modules, each consisting of a sleeve, having essentially the same outer form and section as the inner form and section of the housing module, filled with explosive, one sleeve being filled with a primary explosive,

c) providing a starter module comprising means of igniting an explosive and having an end surface comprising connecting means,

d) inserting into the housing module two or more explosive filled tubular modules, the module containing the primary explosive being inserted last,

e) inserting the igniting module after the primary explosive module,

f) if necessary, filling possible open spaces within the housing with a filling material and

g) closing the open end of the housing, leaving the connecting means accessible from the outside.
Process of producing an igniter/initiator, comprising the steps of
a) providing a tubular housing module, having a through opening and being open at both ends,

b) providing two or more tubular explosive modules having a fraction of the height of the housing modules, each consisting of a sleeve, having essentially the same outer form and section as the inner form and section of the housing module, filled with explosive, one being filled with a primary explosive,

c) providing a starter module comprising means of igniting an explosive and having an end surface comprising connecting means,

d) inserting the starter module into the housing module with the end surface comprising connecting means accessible from the outside,

e) inserting the primary explosive module, followed by one or more other tubular, explosive filled modules,

f) if necessary, filling possible open spaces within the housing with a filling material and

g) closing the open ends of the housing, leaving the connecting means accessible from the outside.
Process of producing an igniter/initiator according to claim 6 or 7, wherein the explosive modules contain different explosives.
Process of producing an igniter/initiator according to any of claim 6-8, wherein the modules have elliptic or circular sections.
Process of producing an igniter/initiator according to any of claim 6-9, wherein the modules have differing inner sections and/or heights