Process of producing a propellant charge igniter

A process of producing a propellant charge igniter for cartridge ammunition of the type including an ignition tube with a booster charge, wherein the ignition tube is composed of a sheathing tube (4) with ignition openings (3) and a thin-walled protective tube (6) which is arranged inside the sheathing tube (4) in order to protect the booster charge, and wherein the external wall of the protective tube fits against the internal wall of the sheathing tube (4) and covers the ignition openings (3). To avoid microscopic gaps between the sheathing tube and the protective tube, which gaps influence the performance of the propellant charge igniter, a paste-like sealing agent (5) is introduced into the sheathing tube (4) before the protective tube (6) is inserted into the sheathing tube (4), and only then is the protective tube (6) inserted into the sheathing tube (4) to displace the sealing agent. Alternatively with the protective tube (6) being fully inserted, the ignition openings (3) in the sheathing tube (4) are filled with a sealing agent (5) and then the protective tube (6) as well as the sheathing tube (4) are moved axially, relative to each other.

REFERENCE TO RELATED APPLICATIONS
 This application claims the priority of German Application Ser. No. DE 197
 384 19.6 , filed Sep. 3, 1997 which is incorporated herein by reference.
 BACKGROUND OF THE INVENTION
 The present invention relates to a process of producing a propellant charge
 igniter for cartridge ammunition which igniter comprises an ignition tube
 containing a booster charge. More particularly, the present invention
 relates to a method of producing such a propellant charge igniter wherein
 the ignition tube is composed of a sheathing tube provided with ignition
 openings, and a thin-walled protective tube that is arranged inside the
 sheathing tube to protect the booster charge, which protective tube rests
 with its external wall against the internal wall of the sheathing tube and
 covers the ignition openings.
 In order to protect the booster charge against external environmental
 influences (e.g., against moisture entering from the outside) or against
 components of the propellant powder surrounding the propellant charge
 igniter, which can come in contact with the booster charge as a result of
 sweating, migration or plasticizer migration), known propellant charge
 igniters are provided with a thin-walled protective tube, the outside wall
 of which fits flush against the inside wall of a sheathing tube provided
 with ignition openings and covers these openings. Practical tests
 performed with such propellant charge igniters have shown that microscopic
 gaps or clearances can occur between the sheathing tube and the protective
 tube, which gaps or clearances reduce the protective effect.
 It is therefore the object of the present invention to provide a process of
 producing a propellant charge igniter of the type discussed above, which
 avoids the occurrence of microscopic gaps or clearance.
 SUMMARY OF THE INVENTION
 The invention according to a first embodiment is essentially based on the
 idea of filling the sheathing tube on the base side with a predetermined
 amount of sealing agent which has the consistency of paste during the
 processing, and to push this sealing agent into the sheathing tube with
 the aid of the protective tube, which is closed on one end, so that the
 protective tube can slide into the sheathing tube and seal any possibly
 existing spaces between the sheathing tube and the protective tube and
 subsequently harden therein. During the production, the excess sealing
 agent is pushed out from the inside through the ignition openings, and is
 then removed on the outside.
 According to a second embodiment of the invention, an approximately 15 mm
 thick coating of sealing agent preferably is applied to the protective
 tube in the base region of the sheathing tube, and the protective tube,
 preferably with the coating, is then pushed into the sheathing tube to its
 limit. The sealing agent then is injected, e.g., with the aid of a
 cartridge, from the outside, through the individual ignition openings or
 bores. Possibly existing gaps between the protective tube and the
 sheathing tube in the region of the ignition openings or bores are closed
 and the bores are filled. If desired, the sheathing and protective tubes
 can then be moved axially relative to one another to further distribute
 the sealing agent.
 In the alternative embodiment, possibly existing microscopic gaps or
 clearances are not filled completely, but only partially. That is, only at
 those locations where moist and volatile propellant charge components can
 enter are the gaps filled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to FIGS. 1 and 2, there is shown the end region 1 of a sheathing
 tube 4 of an ignition tube, which tube 4 is closed at one end to define a
 hollow space 2 and is provided with radially extending ignition openings
 or bores 3 in its side wall. The hollow space 2 of the sheathing tube 4 is
 filled with a given amount of paste-like sealing agent 5.
 FIG. 1 shows a thin-walled plastic protective tube 6 which is closed at its
 lower end and which has been pushed, with the aid of a non-depicted
 plunger or ram, from above partially into the hollow space 2, so that the
 sealing agent 5 is displaced and moves into the intermediate spaces that
 may exist between the protective tube 6 and the sheathing tube 4. The
 excess sealing agent 5 is pushed out through the ignition openings 3, as
 shown in the uppermost opening in FIG. 1, and is subsequently removed.
 FIG. 2 shows the protective tube 6 completely inserted into the sheathing
 tube 4 to displace the sealing agent 5 and fill the openings 3 and with
 the excess sealing agent 5 removed.
 According to a preferred alternate embodiment of the invention, prior to
 insertion into the sheathing tube 4 and using a process not illustrated in
 detail here, an approximately 15 mm thick coating of sealing agent 5
 preferably is applied to the protective tube 6 on its circumferential
 surface facing the sheathing tube 4, that is, in the base region 1 of
 sheathing tube 4. The protective tube 6 is then pushed into the sheathing
 tube 4 until it reaches its insertion limit, wherein the sealing agent 5
 seals the intermediate space between the sheathing tube 4 and the
 protective tube 6, at least in the base region, and the stripped-off
 excess sealing agent is removed on the outside. With the aid of a
 cartridge (not shown), sealing agent 5 is subsequently injected from the
 outside into the individual ignition or blow-out openings 3, thereby
 closing off and filling possibly existing gaps between the protective tube
 6 and sheathing tube 4 in the region of the blow-out openings 3.
 Microscopic gaps in particular are not filled completely, but only
 partially with this process, that is to say only at locations in danger of
 allowing moisture and volatile propellant components to enter are sealed.
 If desired, the protective tube 6 and the sheathing tube 5 may then be
 moved axially relative to one another a number of times to further
 distribute the sealing agent 5. Finally, the sealing agent is permitted to
 harden.
 Following the hardening of sealing agent 5, the booster charge, which is
 not shown for reasons of clarity, is inserted into the ignition tube in a
 manner known per se.
 The sealing agents used can be either 2-component polyurethane (PU)
 adhesives (without solvents) or paste-like, one-component sealing agents,
 e.g., on a silicone base, wherein the sealing agents must be selected such
 that they ensure good adhesion to the protective tube 6, which normally is
 made of plastic, and to the ignition or sheathing tube 4 that is normally
 composed of metal.
 The respective, paste-like sealing agents have the advantage of containing
 nearly 100% solid matter and are processed with only a small amount of
 solvents or none at all. The sealing agents have a high creep stability
 without tendency to flow during the processing and in the hardening phase.
 The hardening can occur physically through the extraction of small amounts
 of residual solvent or through diffusion of moisture, which leads to a
 chemical cross-linking.
 Among other things, sealing agents on a polyisobutylene or butyl rubber
 base have proven themselves. These sealing agents harden physically
 through the extraction of small amounts of residual solvents, which
 extraction can be accelerated through heating, preferably by approximately
 50.degree. C.
 Sealing agents and adhesives on a silicone or polyurethane base, which are
 preferred, harden through the admittance of moisture or the admixture of a
 hardening agent component. The hardening of these sealing agents can also
 be accelerated through heating.
 Once they have hardened, the aforementioned sealing agents exhibit a
 sufficiently high deformability, elasticity and expansion in the
 temperature range between -.sub.54.degree. C. and 71.degree. C. to
 compensate for the thermal behavior of the sheathing tube 4 and protective
 tube 5 relative to each other.
 The invention now fully being described, it will be apparent to one of
 ordinary skill in the art that many changes and modifications can be made
 thereto without departing from the spirit or scope of the invention as set
 forth herein.