Propellant charge igniter

A propellant charge igniter for cartridge ammunition, includes an ignition tube; and a transfer charge disposed within the ignition tube, wherein the ignition tube is composed of a jacket tube having defined therein a plurality of ignition openings; and a protective tube which is positioned within the jacket tube so that the outside wall of the protective tube rests flush against the inside wall of the jacket tube and covers the plurality of ignition openings, which is thin-walled and has a wall thickness ranging from 0.1 mm to 0.8 mm, which is arranged to effectively protect the transfer charge against adverse external environmental influences including humidity, and which is comprised of a material selected from the group consisting of glass, oxide ceramic material, glass ceramic material, metal or metal alloy, and plastic. This arrangement provides a reliable sealing of the transfer charge against external environmental influences over a long time period, e.g., at least 10 years, even if handled roughly.

BACKGROUND OF THE INVENTION 
1. Field of The Invention 
The invention relates to a propellant charge igniter for cartridge 
ammunition in which the charge igniter includes an ignition tube 
containing a transfer charge. 
2. Description of the Related Art 
In a propellant charge igniter of this type, the sensitive, explosive 
elements of the explosive train must be present in a protected, e.g., 
jacketed, form. The transfer charge of this explosive train is made from 
easily ignitable powder which burns up very quickly and propagates the 
flame very rapidly even with only a moderate pressure applied, and lies 
encapsulated in the metallic ignition tube of the propellant charge 
igniter in which ignition distribution bores are distributed over the 
entire length of he ignition tube. Up-to-date propellant charge igniters 
have ignition tubes which, in relation to the entire cartridge, have a 
maximum possible length in order to take the ignition flame unhindered 
into upper (front) propellant powder layers of the cartridge ammunition 
and in order to have an ignition surface available which is as large as 
possible by means of the ignition distribution bores. 
For known propellant charge igniters of this type, a considerable 
expenditure is typically necessary for the sealing of the sensitive 
ignition elements against environmental influences. Therefore, especially 
the ignition openings and threaded parts of the ignition tube must be 
securely sealed to ensure the functioning of the propellant it charge 
igniter. If the ignition elements are not sufficiently protected against 
humidity, malfunctions or ignition delays occur when the propellant charge 
igniter is fired. With respect to demands of customers for the 
corresponding cartridge ammunition, sealing of the transfer charge must be 
reliably ensured for at least 10 years in humid and aggressively humid 
climates, even if the corresponding cartridge itself is not totally sealed 
against humidity. 
From U.S. Pat. No. 2,446,187, a propellant charge igniter is known wherein, 
for the protection of the booster charge against external environmental 
influences, a thin-walled protective tube made from a lead/tin alloy is 
arranged within the jacket tube. Here, the protective tube rests flush 
against the inside wall of the jacket tube so that the ignition openings 
are covered. If the charge igniter is activated, the shock pressure 
punches out the ignition openings of the protective. However, the ignition 
flame in this arrangement is weakened by energy withdrawal due to 
simultaneous start of melting of the lead/tin alloy which thus results in 
delayed flame propagation through the ignition openings into the 
propellant powder of the cartridge. This time delay becomes measurably 
significant so that the required short ignition times, e.g., far below 50 
ms, are not reached. 
Furthermore, a propellant charge igniter of this design has the drawback 
that the material of the protective tube comprises lead constituents which 
are released when the cartridge is ignited and which reach the ambient air 
as toxic agents and pollutants. Finally, the use of such a protective tube 
made from a metal alloy will probably result in an impermissible increase 
in the internal pressure of the propellant charge igniter. 
From European Patent No. 0 392 533 B1 and German Published Patent 
Application No. 37 01 145 A1, propellant charge igniters with ignition 
tubes are known wherein the ignition openings are covered by plastic 
sleeves applied on the outside of the respective jacket tube. 
The drawback of these propellant charge igniters is that the respective 
plastic sleeve might be damaged in case of mechanical stressing of the 
cartridge, e. g., during jolting coincident with testing, because the 
edges of the hard propellant powder grains in the main charge of the 
cartridge can wear or damage the sleeve through friction and scoring, thus 
leading to a failure of the protection against the penetration of humidity 
into the propellant charge igniter. 
German Patent No. 34 16 736 C2 discloses a propellant charge igniter 
wherein a protective casing is arranged on the inside of the jacket tube 
and is made from a heat-shrinkable plastic film. The protective casing 
holds together a transfer charge comprised of several ring pellets and 
encloses it firmly. During the ignition process, the propagation of the 
ignition flame is inhibited, however, because the blocking effect of the 
enclosing plastic thwarts a rapid, no-delay ignition of the entire 
transfer charge so that a measurable increase of the ignition time is 
noted. 
It is therefore an object of the present invention to provide a propellant 
charge igniter having an ignition tube with an internally arranged 
protective tube which reliably seals the booster charge and the transfer 
charge against external environmental influences over a period of more 
than 10 years despite rough handling, the presence of shock-like 
temperature fluctuations, and/or storage under increased humidity 
conditions. 
SUMMARY OF THE INVENTION 
This and other objects are accomplished by the present invention which 
provides a propellant charge igniter for cartridge ammunition, comprising: 
a. an ignition tube; and 
b. a transfer charge disposed within the ignition tube, 
wherein the ignition tube is comprised of: 
a jacket tube having defined therein a plurality of ignition openings; and 
a protective tube which is positioned within the jacket tube so that the 
outside wall of the protective tube rests flush against the inside wall of 
the jacket tube and covers the plurality of ignition openings, which is 
thin-walled and has a wall thickness ranging from 0.1 mm to 0.8 mm, which 
is arranged to effectively protect the transfer charge against adverse 
external environmental influences including humidity, and which includes 
at least one layer comprised of a material selected from the group 
consisting of: 
(a) glass, 
(b) oxide ceramic material, 
(c) glass ceramic material, 
(d) metal or metal alloy, and 
(e) plastic. 
Further advantageous embodiments of the invention are disclosed in the 
dependent claims. 
The present invention is based on the concept of using a protective tube 
which rests tightly against the inside wall of the jacket tube and is 
comprised of a thin-walled material so that the cross-section of the tube 
remains open to the greatest possible extent for the passage of and 
propagation of ignition. Such demands are met particularly by protective 
tubes which are thin-walled, i.e., having a wall thickness ranging from 
0.10 mm to 0.80 mm, preferably a wall thickness ranging from 0.15 mm to 
0.60 mm, and are made from substances including glasses, oxide ceramic 
materials, glass ceramic materials, metals or metal alloys, and plastics. 
Wall thicknesses of less than 0.10 mm do not provide the desired reliable 
seal. Wall thicknesses of greater than 0.80 mm do not provide the desired 
rapidity of flame propagation during ignition of the corresponding 
cartridge ammunition. 
When plastics are used for the protective tubes or inner liners, 
particularly advantageous embodiments of the invention proved to be those 
in which the protective tube or inner liner is comprised of an adhesive 
coated plastic layer (film), a blown plastic layer (film) or a combination 
of both such layers which are inserted into the ignition tube. When an 
adhesive coated plastic layer is employed, the adhesive coating layer is 
provided on the plastic layer and is positioned in contact with the inner 
wall of the jacket tube. Thus, the protective tube may be multi-layered 
and may be comprised of an adhesive layer, a first plastic layer, and a 
second plastic layer, wherein the adhesive layer is provided on the first 
plastic layer and is positioned in contact with the inner wall of the 
jacket tube, and wherein the second plastic layer is a blown film. 
Furthermore, it proved to be advantageous to provide the protective tube 
with predetermined fracture points in the region of the ignition openings, 
particularly upstream thereof, i.e., towards the end of the ignition tube 
near the interior of the cartridge. 
In a further advantageous application, the protective tube (inner liner) 
may be comprised of a plastic tube made from polyethylene (PE) or 
polypropylene (PP), particularly from polyethylene or polypropylene 
produced according to a rotational molding process or blow molding 
process, and most particularly with the production of the protective tube 
taking place within the ignition tube itself. 
In a further advantageous embodiment, the protective tube may be composed 
of a mixed metal film, i.e., a metal alloy layer, which is protected by a 
coating of paint or varnish provided on at least one surface thereof. 
Preferably metallic cerium (Ce) is the main constituent of the mixed metal 
alloy and is present in an amount of more than 50 % by weight. Metal 
constituents of the alloy which would constitute pollutants when the 
cartridge ammunition is ignited, such as lead, are to be avoided as are 
metal alloys which melt simultaneously with ignition and would thus 
disadvantageously delay flame propagation. 
In yet another advantageous embodiment, the protective tube is comprised of 
a layer of one of glass, oxide ceramic material or glass ceramic material. 
If the protection tube 10 has a wall thickness which is less than 0.3 mm, 
inclusion of a bonding layer for improving the connection with the 
interior side of the jacket tube has proven useful for protective tubes of 
this type. Advantageously, such thin* walled tubes may be coated with a 
silicone layer which provides an adhesive bond with the jacket tube so 
that stable support is provided. Thus, the protective tube advantageously 
further comprises a coating layer comprised of a thin silicone film. The 
silicone material may be a silicone fluid film having a thickness ranging 
from a monolayer up to a thickness effective to provide the desired 
adhesive bond, for example, about 10 micrometers. The silicone material 
may also be any silicone polymer which forms a film and has a thickness 
ranging from 1 to 100 micrometers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates in longitudinal cross-section a propellant charge 
igniter according to the invention. Propellant charge igniter 1 is 
comprised of a head section 2 and an ignition tube 4 adjoining the head 
section 2 in the direction of longitudinal axis 3 of the charge igniter 1. 
The head section 2, which comprises a percussion cap (not shown) and a 
booster charge 7, is provided with an external thread 6 with which the 
propellant charge igniter 1 is screwed into the bottom of a corresponding 
ammunition cartridge (not shown). 
Ignition tube 4 is filled with a transfer charge 5 and is comprised of a 
jacket tube 8 made of steel and provided with a plurality of ignition 
openings 9 and a seal in the form of an inner liner or protective tube 10 
which is arranged on the inside surface of the jacket tube 8 and which 
covers the plurality of ignition openings 9. Ignition openings 9 rupture 
during ignition and, moreover, a plurality of fracture points 14 
optionally may be provided on protective tube 10 upstream of the ignition 
openings 9 to further expedite ignition flame propagation. 
The ignition tube 4 has a front end 11 and a side 12 facing the head 
section 2 of the propellant charge igniter 1. The inner liner or 
protective tube 10 is closed at the front end 11 of the ignition tube 4 
and sealed on the side 12 facing the head section 2 of the propellant 
charge igniter 1 by means of a seal 13 made from an elastic material, such 
as a rubber, for example, neoprene. 
The inner liner or protective tube 10 may be fabricated as a single layered 
structure as in FIG. 1 or a multi-layered structure as in FIGS. 2 and 3. 
Examples of such structures for the inner liner or protective tube 10 
include a polymeric layer glued-in with an adhesive layer, a blown 
polymeric layer, a polymeric layer glued-in with an adhesive layer in 
combination with a blown polymeric layer, a metal or metal alloy layer, 
and a glass layer, an oxide ceramic material layer or a glass ceramic 
material layer with a silicone adhesion coating layer. 
FIG. 2 illustrates in cross-section a propellant charge igniter according 
to the invention in which the protective tube includes first and second 
layers 16, 17 comprised of plastic material and an adhesive coating 15 
provided between the protective tube and the jacket tube. 
FIG. 3 illustrates in cross-section a propellant charge igniter according 
to the invention in which the protective tube is comprised of a glass 
layer, an oxide ceramic material layer or glass ceramic material layer 19 
and a coating 18 comprised of a thin silicone film provided between the 
protective tube and the jacket tube. 
The following examples illustrate, by way of example but not limitation, 
several materials and methods for insertion of the protective tube 10 into 
the jacket tube 8. 
EXAMPLE 1 
A glued-in film is useful as protective tube 10. For this purpose, a 
plastic film 16 (see FIG. 2) having a wall thickness with a maximum of 
0.25 mm and being coated with an adhesive layer 15 that can be thermally 
activated, was inserted into the jacket tube 8 and heated to a temperature 
effective to activate the adhesive, e.g., to a temperature ranging from 
above about 65.degree. C. up to about 180.degree. C. The adhesive layer 15 
is a thin layer having a thickness ranging from a monolayer up to about 
100 micrometers. The ready-for-bonding film 15, 16 thus produced was then 
glued onto the interior side of jacket tube 8 by applying pressure thereon 
from within. 
Laminated polyurethane (PU)/polyolefin (PE or PP) films have proven useful 
as protective tube materials. In particular, a polyethylene film coated 
with, for example, a reactive two-component polyurethane adhesive which 
cross-links when heated has been used. Adhesives based on polychloroprene, 
cyanoacrylate, etc. are also suitable. 
EXAMPLE 2 
A blown film has been used as a protective tube 10. For this purpose, a 
parison, i.e., a plastic sleeve in the molten state, was extruded into the 
jacket tube 8. A mold having a corresponding blow opening surrounded 
jacket tube 8. By means of blown-in air, the parison was then pressed 
against the inside wall of jacket tube 8 where it was cured in place. 
Thermoplastic polymers, such as polyethylene (PE), polypropylene (PP), 
polyethyleneglycol terepthalate (PET), polymethylene pentene (PMP), and 
copolymers and terpolymers of ethylene-propylene diamine (EPDM) have 
proven useful as parison materials. Thermoplastic fluororubbers and other 
thermoplastic elastomers are also suitable. Of primary importance for the 
selection of a suitable material for protective tube 10 is that the 
material have a high barrier effect vis-a-vis humidity and water. The wall 
thickness should be effective for this criteria and preferably ranges from 
0.15 mm to 0.6 mm. 
EXAMPLE 3. 
A multi-layered structure is useful for protective tube 10. The protective 
tubes according to Examples 1 and 2 may be combined into a multi-layered 
structure, see FIG. 2. First, a film in accordance with Example 1 above is 
positioned inside of jacket tube 8 and then a parison in accordance with 
Example 2 is inserted therein and blown in place. Blowing in place of the 
molten parison applies heat and pressure onto the film in accordance with 
Example 1 and serves to glue this adhesive coated film in place and in 
contact with the inner surface of the jacket tube. 
EXAMPLE 4. 
An oxide ceramic or glass ceramic is useful for protective tube 10. 
Protective tubes 10 which are closed on one side and are self-supporting 
must be sufficiently stable so that they can cushion mechanical stresses, 
e. g., jolting from impacts and vibration. Protective tubes 10 made from 
an oxide ceramic material or glass ceramic material having a wall 
thickness ranging from 0.3 mm to 0.6 mm have proven to be particularly 
suitable. 
Such a tube is open when viewed from the perspective of the ignition 
section and is therefore provided on the head section 2 with a thickened 
rim which is folded inwardly or outwardly (not shown). The rim has a 
groove channel (not shown). The groove can receive a sealing O-ring or a 
resilient sealing ring (not shown). The front end 11 of the jacket tube 8 
is closed off. To secure a tight seat of the protective tube 10 in the 
region of the front end 11, a resilient ring element (not shown) made from 
soft rubber may be provided there as well. 
Oxide ceramic materials based on zirconium oxide or on aluminum oxide 
stabilized with zirconium oxide have a good bending behavior and are 
useful particularly where increased mechanic stresses are likely. 
If the protection tube 10 has a wall thickness which is less than 0.3 mm, a 
bonding layer for improving the connection with the interior side of the 
jacket tube 8 has proven useful for protective tubes of this type, see 
FIG. 3. Advantageously, a tube 10 with such a thin-walled layer 19 may be 
coated with a silicone layer 18 which provides an adhesive bond with the 
jacket tube so that stable support is provided. 
The invention is not limited to the above-described embodiments. Thus, 
particularly the protective tubes made from plastic can be made, for 
example, not only by means of molding, blow molding, or rotational molding 
but also by means of injection molding or other extrusion techniques. 
It is understood that various other modifications will be apparent to and 
can be readily made by those skilled in the art without departing from the 
scope and spirit of the present invention. Accordingly, it is not intended 
that the scope of the claims appended hereto be limited to the description 
set forth above but rather that the claims be construed as encompassing 
all of the features of patentable novelty which reside in the present 
invention, including all features which would be treated as equivalents 
thereof by those skilled in the art to which the invention pertains.