System using an electropyrotechnic device intended to trigger the operation of a gas generator

An electropyrotechnic device for sequentially triggering the operation of a battery of gas generators. The ignition of double-base propellant blocks is obtained by the combination of EFI and an IFOC, arranged so that the airtight barrier between the cavity containing the donor secondary explosive and the downstream chamber containing the secondary receiving explosive is only one part of the closing element of the back end carrying the nozzles, integral with the ring. The control electronics of the EFI are contained inside a housing capping the back end of the powder generator with the entire system being closed by a cap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a system using an electropyrotechnic device 
intended to trigger sequentially the operation of a battery of gas 
generators. 
2. Description of the Prior Art 
An application of these systems is found, for example, in the area of the 
release of air-to-surface submissile rounds from a cargo aircraft calling 
for the use of gases formed by powder generators. Difficulties appear when 
the number of gas generators is increased, particularly with regard to 
reliability, because the precautions necessary to assure an acceptable 
rate of reliability then become very expensive in terms of cost and space. 
These two requirements of increased reliability and decreased space 
requirement and weight serve as a basis for the optimized combination of 
the present invention. 
SUMMARY OF THE INVENTION 
Accordingly, one object of this invention is to provide a novel system 
using an electropyrotechnic device intended to trigger the operation of a 
powder generator placed inside a ring having a front end and a back end, 
the system has a downstream chamber containing a so-called IFOC 
(Inflammateur Fonctionant par Ondes De Choc, i.e., igniter operated by 
shock waves) secondary receiving explosive, which is able, by shock wave 
detonation, to cause flames which trigger the powder generator. The 
chamber is made in a first bore of a closing element of the back end of 
the ring which has a shape of a truncated cone with nozzles coming out in 
the side wall of the back end. 
The system also includes an upstream cavity containing a donor secondary 
explosive and made in a second bore placed head-to-tail relative to the 
first bore and separated from the latter by an airtight barrier which 
consists of a zone of the closing element of the back end of the ring. 
Also included is a so-called EFI projected-layer initiator positioned 
opposite the upstream cavity and producing, when it is initiated, a 
detonation in the upstream cavity. A housing caps the back end and has a 
bottom in the shape of a truncated cone which is complementary to the 
truncated cone of the back end of the ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As FIGS. 1 and 2 show, an electropyrotechnic device (E) according to the 
invention essentially consists, for its ignition part, of a 
projected-layer initiator (1), more commonly known by the English 
terminology of "EFI" (Exploding Foil Initiator). The latter produces a 
detonation in an upstream cavity (Ca) which contains a donor secondary 
explosive (2). When the latter detonates, it produces a shock wave which 
is propagated through an airtight barrier (3) to a downstream chamber (Ch) 
containing a secondary receiving explosive (4) which is able, by 
detonation, to cause flames which, in turn, cause the combustion for the 
charging of powder (P) of gas generator (g). The igniter device of the gas 
generator thus is assured, according to the invention, by the combination 
of an EFI and an IFOC (igniter operating by shock wave). 
Such a combination offers the advantage of avoiding the installation of 
safety means between the standard igniters and the pyrotechnic charges in 
the pyrotechnic chain, as is the case in the prior art. Further, the 
introduction of electric means inside gas generators is thus avoided. 
Such an electropyrotechnic device (E) according to the invention is 
integrable at least partially in the very structure of gas generator (g) 
thus providing a compact and reliable finished product. 
According to another characteristic of the invention, the system consists 
of such an igniter as described above which assures the correct start of 
the combustion of a charging of double-base propellant having a combustion 
profile and characteristics so that the pressure is maintained at an 
almost constant value during the entire period of the combustion. A 
closing pallet (22) is installed to close chamber (Ch) of the IFOC. 
According to an embodiment illustrated by FIGS. 1 and 2, the charging of 
powder (P) is achieved inside a ring (10) whose front end (15) is 
hemispherical and whose back end (16), which carries nozzles (12, 13), is 
made integral with ring (10) by, for example, a thread (14). This back end 
(16) has the shape of a convergent truncated cone with nozzles (12) and 
(13) coming out of the side wall of this truncated cone. In the example 
described, there are two nozzles, diametrically opposite, but this number 
is not limiting. 
Closing element (21) of back end (16) exhibits at the level of the vertex 
of the truncated cone two bores placed head-to-tail. One bore delimits the 
space of downstream chamber (Ch) containing secondary receiving explosive 
(4) and the other bore delimits the space of cavity (Ca) containing donor 
secondary explosive (2). A zone of closing element (21) constitutes an 
airtight barrier (3) of the IFOC. This barrier makes possible the 
propagation of the shock wave while exhibiting sufficient mechanical 
strength. 
Back end (16) is capped with an airtight metallized plastic housing (17) 
whose bottom (18) also has the shape of a truncated cone, complementary to 
the convergent truncated cone defined above. 
The two ends of these two truncated cones are fitted into one another, 
enclosing cavity (Ca) containing donor secondary explosive (2). Cover (30) 
of housing (17), which holds EFI (1) in position, is placed on the vertex 
of the truncated cone of housing (17). The latter contains the control 
electronics 47 which is supplied through its wall, via filters (31) and 
airtight passage means (37), by an electric connection (32) connected to a 
sequencer, not shown. This housing (17) is placed on a cushion (33) acting 
as a damper while a set of seals (34) assures the sealing at all levels. 
The housing is made, for example, of metallized plastic and constitutes an 
ideal housing for the control electronics of EFI (1). 
The whole device is closed by a cap (35) made integral with back end (16) 
by an known means such as a screw system (40). In these figures, a single 
generator has been shown, but as has been stated above, the invention 
applies more particularly when these generators are grouped in a battery. 
FIG. 3 illustrates another embodiment of combination (EFI-IFOC) integrated 
in nozzle-holder back end (16). The two bores delimiting upstream cavity 
(Ca), downstream chamber (Ch) and airtight barrier (3) are as indicated 
previously, but in this embodiment, EFI (1) is made directly integral with 
nozzle-holder back end (16) by, for example, a threading (60). Such a 
structure contributes to making the unit also more compact. 
As FIG. 4 and FIG. 5 show, the propellant charging consists of seven powder 
blocks (P) whose combustion profile is star-shaped (FIG. 4). These powder 
blocks (double-base propellant) are held by two metal grids (50) provided 
with wedging claws (55) and spacing elements (56). 
As has already been stated above, in such a structure as described 
according to the invention, a propellant ignition at a constant pressure 
combustion is assured without having to introduce electric means inside 
the charge. The ignition necessitates the use only of secondary 
explosives, which contribute to the reliability of the system. Utilizing a 
combination of an EFI and an IFOC further makes it possible to integrate 
these means as well as the electronic control means of an EFI (1) inside 
the general structure of gas generator (g) without danger of gas passage. 
The existence of cap (35) on the one hand and closing element (21) on the 
other hand provide an assurance of a second function, namely, that of 
propagating the shock wave at the level of airtight barrier (3) of the 
IFOC. 
The electronic control means are compacted inside a housing located inside 
the general structure of the gas generator. 
The invention applies each time a battery of generators is used, as is the 
case of the release of air-to-surface submissile rounds from a cargo 
aircraft. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.