Plastic liner for bayonet primers

Details Plastic liner for bayonet primers Plastic liner for bayonet primers

1999-08-31

2001-08-14

Jordan, Charles T. (Department: 3644)

Ammunition and explosives

Igniting devices and systems

Percussion primers or ignitors

C102S202000, C102S470000, C102S469000

Reexamination Certificate

active

06272994

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to bayonet primer devices, and more particularly to a plastic liner for bayonet primers used in tank ammunition.
BACKGROUND OF THE INVENTION
Bayonet primers have long been used in tank ammunition. Conventional bayonet primers have a cartridge case base that is ejected into the confines of the fighting vehicle after the propelling charge has been ignited by the primer. Unfortunately, in the case of originally designed bayonet type primers, the ejected case base, including the steel primer body created a hot metal tube that was able to come into contact with an ammunition round that was being held ready for loading after the chambered round was extracted. The ejected round could land on the next round and start a fire within the close confines of the fighting vehicle.
To promote safety for the crew of the fighting vehicle and solve the aforesaid fire hazard, tank ammunition primers were sealed with silicone rubber and other materials in order to keep them from igniting when contacting a hot ejected round. Unfortunately, such exterior rubber seals are expensive and have other significant drawbacks.
One current method of sealing bayonet primers uses a paper liner placed inside the flashtube. The flashtube is then dipped in a vat of lacquer, thereby filling flashholes with lacquer to protect the pyrotechnic charge from moisture. Excess lacquer must be scraped from the exterior of the flashtube. Finally, the lacquer plugs so formed are air dried. This is necessary because the various ignition charges are very hygroscopic and the presence of moisture will have an adverse effect upon the ignition charges, causing their degradation and possibly resulting in misfires.
As noted in U.S. Pat. No. 5,465,665 to Diehl issued Nov. 14, 1995, entitled “Primer,” a typical bayonet type primer includes a primer head for housing an initial firing stage of a round. An ignition element, pressed into place in the confines of the primer head, is charged with a pyrotechnic composition that starts the firing train. When activated, the ignition element disperses a flame through a retainer. The flame sets off an explosive charge of black powder. The black powder charge in turn propagates through a closing plug, which acts as a directional device to a third charge of Benite. Benite is comprised mainly of nitrocellulose and black powder in a stranded form and other pyrotechnic formulations, housed in the primer body. The third charge propagates through holes in the metal primer body initially sealed with a lacquer. This charge, propagating through the primer body, ignites the propelling charge contained in the ammunition case moving the ammunition projectile such as a penetrator out of the gun barrel and to its target. U.S. Pat. No. 5,465,665 is incorporated in its entirety herein by reference. Unfortunately, Diehl proposes using a hollow tubular one-piece body comprised of a molded thermoplastic material that body still requires lacquer sealing. Alternatively, the perforations in the body may be molded such that there is a thin skin covering the perforations, but this latter method still requires sealing many individual flash holes.
There are several drawbacks to primers constructed in accordance with such known methods. One such drawback is inherent in the use of the sealing lacquer because the lacquer consistency varies within batches and between batches with respect to viscosity and percent solids. Such inconsistencies make the process variable and difficult to control.
Other drawbacks of conventional sealing by paper liner are caused by the method of applying the lacquer that can create bubbles in the flash holes. The presence of bubbles results in a marginal seal. The lacquer itself has undesirable moisture permeability. Further still, it is difficult to determine by inspection whether all flashholes are sealed.
Furthermore, a paper liner, if used, does not always seat tightly to the interior of the flashtube and lacquer may leak into the interior of the primer. As a further drawback, a paper liner is susceptible to being caught by charge strands of Benite during loading. Once so damaged, it is difficult to load the primer charge.
In other types of tank ammunition primers, much shorter primers were used. For example, a stub plastic liner was used with short primers of about one inch in length. Such stub liners were made by injection molding. Injection molded parts are not practical for liners suitable for use with longer bayonet primers. It has been found that injection molding is not desirable for longer liners because 1) the draft angle required to extract the part from the mold reduced the internal volume to the point that sufficient charge could not be loaded, and 2) the injection pressures required to fill the mold quickly pushed the mandrel core against the sidewall, thereby ruining the part.
SUMMARY OF THE INVENTION
The present invention provides a primer assembly with a plastic flashtube liner. A flashtube containing an ignition charge has an open rearward end connected to a head loading assembly. A closing plug assembly includes a conically bored open frontward end and an open cylindrical rearward end that may is include an optional outer flange between the frontward and rearward ends. The closing plug assembly is attached to the head loading assembly located rearwardly of the flashtube. The flashtube liner has a flange at an open rearward end. The flashtube liner is inserted into the flashtube to line the inner wall of the flashtube. In one example, the flashtube liner is held in place by the flashtube impinging the flashtube liner flange between the head loading assembly and the open rearward end of the flashtube. The flashtube liner is comprised of an extruded plastic material.
In contrast to the prior art, the present invention provides a plastic flashtube liner that has the advantage of eliminating the use of a liquid to seal the flashholes.
As a further advantage, the liner of the present invention reduces the number of seals from one for each flashhole to a single piece seal.
As a further advantage, the plastic liner of the invention significantly increases the safety of workers during assembly by allowing the charge to be loaded into inert sleeves prior to entering the assembly area, greatly reducing the exposed surface of explosive material during primer assembly.
As a further advantage, the plastic liner of the invention eliminates all need to maintain complicated purple lacquer processes requiring monitoring of temperature, percent volatiles/solids and mixing, and eliminates the multi-step process to insert a paper liner, including dipping, drying, inspecting, and reworking lacquer seals.
As a further advantage, the plastic liner of the invention improves safety of the operators by eliminating exposure to potentially harmful fumes.
As a further advantage, the plastic liner of the invention improves inspectability because the flashtube liner can be pressure tested for integrity before is assembly onto the primer. For example, the plastic tube can be leak tested prior to assembly and is made from a stable, virtually inert, plastic material that is impervious to moisture.
As a further advantage, the plastic liner of the invention is far more inert and stable than the lacquer previously used in this process.
Other objects, features and advantages of the invention will become apparent to those skilled in the art through the description of the preferred embodiment, claims and drawings herein wherein like numerals refer to like elements.


REFERENCES:
patent: 1491676 (1924-04-01), Courouble
patent: 3182595 (1965-05-01), Hassman
patent: 5052302 (1991-10-01), Taddeo
patent: 5465665 (1995-11-01), Diehl
patent: 5831204 (1998-11-01), Lubben
patent: 5895881 (1999-04-01), Thiesen et al.
Bourgeois and Blackett, High-Density Polyethylenes(HDPE),1988, Vol. Engineered Materials Handbook, ASM International, pp. 163-166.

Affiliated with

Also associated with

Rating

Plastic liner for bayonet primers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Plastic liner for bayonet primers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plastic liner for bayonet primers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2487006