PLASTIC LINER FOR BAYONET PRIMERS

Abstract: A flashtube liner (30) for a primer assembly including a head loading assembly (12). A flashtube (14) containing an ignition charge has an open rearward end connected to the head loading assembly (12). A closing plug assembly (20) includes a conically bored open frontward end and an open cylindrical rearward end that may include an optional outer flange between the frontward and rearward ends. The closing plug assembly (20) is attached to the head loading assembly (12) located rearwardly of the flashtube. A flashtube liner (30) has a flange (32) at an open rearward end. The flashtube liner (30) is inserted into the flashtube (14) to line the inner wall of the flashtube. The flashtube liner (30) is held in place by the flashtube (14) impinging the flashtube liner flange (32) between the head loading assembly (12) or the optional flange, and the open rearward end of the flashtube. The flashtube liner (30) is constructed of an extruded plastic material, such as high density polyethylene.

Description: PLASTIC LINER FOR BAYONET PRIMERS 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 CROSS REFERENCE TO RELATED APPLICATION The present patent application is related to co-pending U S patent application, attorney docket number ATK20579US, to Reider, entitled "BAYONET PRIMER " filed on the same date as the present patent application The aforesaid to co-pending U S patent application, attorney docket number ATK20579US is hereby incorporated by reference 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 Patent 5,465,665 to Diehl issued November 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 Patent 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 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 improved 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 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 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial cut-away perspective view of one example of a bayonet primer including a plastic liner as contemplated by the present invention Figure 2 is a cross-sectional view of one example of a plastic liner tube assembly as contemplated by the present invention Figure 3 is a cross-sectional view of one example of a head loading assembly as contemplated by the present invention Figure 4 is a cross-sectional view of one example of a plastic liner tube assembly loaded with Benite as contemplated by the present invention Figure 5 is a cross-sectional view of one example of an interlocking and press fit head loading assembly including a lengthened closing plug assembly as contemplated by the present invention Figure 6 is a cross-sectional view of a conventional threaded head loading assembly as contemplated for use in an alternate embodiment of the present invention DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a partial cut-away perspective view of one example of a bayonet primer including a plastic liner as contemplated by the present invention The primer assembly 10 includes a head loading assembly 12, and a flashtube 14 An open rearward end 18 of the flashtube 14 is connected to the head loading assembly 12 located rearwardly of the flashtube A closing plug assembly 20 includes a conically bored open frontward end 22 and an open cylindrical rearward end 24 including an optional outer flange 26 between the frontward and rearward ends The closing plug assembly 20 is attached to the head loading assembly 12 The flashtube includes a plurality of holes 70 disposed along the length of the flashtube An extruded plastic flashtube liner 30 is affixed within the flashtube to seal the holes The flashtube liner 30 has a flange 32 at an open rearward end 34 The flashtube liner 30 is inserted into the flashtube 14 so as to line the inner wall of the flashtube 14 In one embodiment of the invention, the flashtube liner 30 is held in place by the flashtube 14 impinging the flashtube liner flange 32 between the closing plug assembly outer flange 26 and the open rearward end 24 of the flashtube To complete the primer assembly 10, the flashtube liner is loaded with a charge of Benite 60, substantially comprising black powder in a stranded medium (best shown in Figure 4) The rearward end 24 of the flashtube is threaded into the head loading assembly 12 to a depth defined by the flashtube liner disposed between the closing plug assembly outer flange 26 and the open rearward end 24 of the flashtube Referring now to Figure 2, a cross-sectional view of one example of a plastic liner tube assembly as contemplated by the present invention is shown The flashtube liner 30 is an extruded plastic tube having a flange 32 and an open rearward end 34 and a top end 40 In one example, the flashtube liner is comprised substantially of an extruded plastic material In a more preferred embodiment of the invention, the extruded plastic material comprises an extruded high density polyethylene material It has been found that the high density polyethylene material works well for constructing a flashtube liner having a length greater than 2 inches The plastic liner may also be made using rotary or blow-molded processes In some prototype devices, the material chosen for the plastic in these parts was polyethylene This material had been prior approved for use in contact with explosives, and was also used to make milk/water jugs, tanks and containers for storing alcohol and acetone for extended periods of time to prevent moisture contamination of the contents Nearly any plastic that has melt characteristics acceptable to the end use storage requirements could be used Figure 3 is a cross-sectional view of one example of a head loading assembly 12 including a closing plug assembly 20 and an ignition element 29 as contemplated by the present invention The head loading assembly 12 includes a frontward throughbore 51 The closing plug assembly is attached within the frontward throughbore 51 The closing plug assembly 20 includes a conically bored open frontward end 22 and an open cylindrical rearward end 24 including an optional outer flange 26 between the frontward and rearward ends The closing plug assembly rearward end 24 contains black powder 37 The head loading assembly 12 includes a rearward throughbore 50 An ignition element 29 is attached within the rearward throughbore 50 When activated, the ignition element 29 is positioned to be in communication with the black powder contained in the closing plug assembly The ignition element 29 includes a conventional electrode 31 In some embodiments, a retainer 27 may be juxtaposed between the closing plug assembly and the ignition element The closing plug assembly 20 is attached to the head loading assembly 12 by press fitting the closing plug assembly into the frontward throughbore 51 Referring now to Figure 4, a cross-sectional view of one example of a plastic liner tube assembly loaded with Benite 60 as contemplated by the present invention is shown The Benite 60 may be loaded before inserting the liner into the flashtube Figure 5 is a cross-sectional view of an example embodiment of an interlocking and press fit head loading assembly 512 including a lengthened closing plug assembly 520 and an ignition element 529 as contemplated by the present invention Note that, in contrast to the configuration of Figure 3, the lengthened closing plug assembly 520 eliminates the need for spacers The head loading assembly 512 includes a frontward throughbore 551 The closing plug assembly is press fitted within the frontward throughbore 551 The closing plug assembly 520 includes a conically bored open frontward end 522 and an open cylindrical rearward end 524 including an outer flange 526 between the frontward and rearward ends The closing plug assembly rearward end 524 contains black powder 37 The black powder 37 may conventionally be held in place by adhesive tape (not shown) The head loading assembly 512 includes a rearward throughbore 550 The ignition element 529 is attached within the rearward throughbore 550 pressed against the closing plug assembly rearward end enclosing black powder 37 The ignition element 529 includes a conventional electrode 531 The closing plug assembly 520 is sized to be press fit into the frontward throughbore 551 The ignition element assembly 529 is configured to be press fit into the rearward throughbore 550, bearing against stop 513 The head loading assembly 512 also includes threads 562 for threadedly attaching the flashtube 14 As best shown in Figure 1 , once the flashtube 14 is attached to the threaded portion of the head loading assembly, the interior parts, including the flashtube liner 30, head loading assembly 12 with the closing plug assembly 20, and the ignition element assembly 31 , are held in place Specifically, the flashtube 14 is threaded onto the head loading assembly 12 The closing plug assembly includes an outer flange 26 The flashtube liner 30 is captivated between the outer flange 26 and the flashtube 14 Figure 6 is a cross-sectional view of a conventional threaded head loading assembly 712 including a closing plug assembly 720 and an ignition element 729 Similarly, to the head loading assembly of Figure 3, the head loading assembly 712 includes a frontward throughbore 751 The closing plug assembly is threaded within the frontward throughbore 751 The closing plug assembly 720 includes a conically bored open frontward end 722 and an open cylindrical rearward end 724 including an outer threaded surface 726 The closing plug assembly rearward end 724 contains black powder 37 The black powder 37 may conventionally be held in place by adhesive tape (not shown) The head loading assembly 712 includes a rearward throughbore 750 In some embodiments, a retainer 727 may be juxtaposed between the closing plug assembly and the ignition element The ignition element 729 is attached within the rearward throughbore 750 secured by retainer 727 The ignition element 729 includes a conventional electrode 731 The closing plug assembly 720 is threaded into the frontward throughbore 751 The ignition element assembly 729 may be configured to be press fit into the rearward throughbore 750 The head loading assembly 712 also includes threads 762 for threadabiy attaching the flashtube 14(shown in Figure 1 ) The invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles of the present invention, and to construct and use such exemplary and specialized components as are required However, it is to be understood that the invention may be earned out by specifically different materials and structural configurations, and that various modifications, both as to materials and structural configurations and operating procedures, may be accomplished without departing from the true spirit and scope of the present invention The embodiments of an invention in which an exclusive property or right is claimed are defined as follows

Claims: 1 CLAIMS 2 1 A primer assembly comprising a) a head loading assembly (12), 4 b) a flashtube (14) containing an ignition charge, an open rearward end of said flashtube (14) connected to said head loading assembly (12), 6 c) a closing plug assembly (20) including an open frontward end and an open 7 rearward end, said closing plug assembly (20) being attached to said head 8 loading assembly (12) located rearwardly of said flashtube, and d) a flashtube liner (30) having a flange (32) at an open rearward end, said 10 flashtube liner (30) inserted into said flashtube (14) so as to line the inner l i wall of said flashtube, wherein said flashtube liner (30) is comprised of an 12 extruded plastic material π 1 2 The primer assembly of claim 1 wherein said extruded plastic material comprises 15 an extruded high density polyethylene material 16 17 3 The primer assembly of claim 1 wherein said flashtube liner (30) has a length is greater than 2 inches 19 20 4 The primer assembly of claim 1 wherein said flashtube liner (30) is loaded with a 21 charge including black powder in a stranded medium 22 23 5 The primer assembly of claim 1 wherein said rearward end of said flashtube (14) 24 is threaded into said head loading assembly (12) to a depth defined by said 25 flashtube liner flange (32) and said open rearward end of said flashtube (14) 26 threaded into said head loading assembly (12) 27 28 6 The primer assembly of claim 1 wherein said closing plug assembly (20) rearward 2 end contains black powder 30 1 7 The primer assembly of claim 6 further comprising 2 a) said head loading assembly (12) including a rearward throughbore, and 3 b) an ignition element attached within said rearward throughbore in 4 communication with said black powder contained in said closing plug 5 assembly (20) 6 7 8 An improved primer assembly including a flashtube (14) attached to a head 8 loading assembly (12), wherein said flashtube (14) includes a plurality of holes disposed along the length of said flashtube, the improvement comprising an lo extruded plastic flashtube liner (30) affixed within said flashtube (14) so as to seal l i said plurality of holes 12 13 9 The improved primer assembly of claim 8 wherein said extruded plastic flashtube 14 liner (30) comprises a high density polyethylene material 15 16 10 The improved primer assembly of claim 8 wherein said extruded plastic flashtube 17 liner (30) is loaded with charge including black powder in a stranded medium 18 19 1 1 The improved primer assembly of claim 10 wherein said extruded plastic 20 flashtube liner (30) comprises a high density polyethylene material 21 22 12 The primer assembly of claim 1 wherein said flashtube (14) has a series of 23 perforations in its wall 24 25 13 The primer assembly of claim (12) wherein said perforations are covered by said 26 flashtube liner (30) 27 28 14 The primer assembly of claim 8 wherein said rearward end of said flashtube (14) 29 is threaded into said head loading assembly (12) to a depth defined by said 30 flashtube liner (30) disposed between said closing plug assembly flange and said l open rearward end of said flashtube 2 i 15 A primer assembly comprising a) a head loading assembly (12), 5 b) a flashtube (14) having an open rearward end connected to said head loading assembly (12), 7 c) a closing plug assembly (20) including a conically bored open frontward end 8 and an open cylindrical rearward end including an outer flange between said 9 frontward and rearward ends, said closing plug assembly (20) attached to lo said head loading assembly (12) located rearwardly of said flashtube, l i d) a flashtube liner (30) containing a charge, and having a flange (32) at an 12 open rearward end, said flashtube liner (30) inserted into said flashtube (14) 13 so as to line the inner wall of said flashtube, wherein said flashtube liner (30) 14 is held in place by said flashtube (14) impinging said flashtube liner flange 15 (32) between said closing plug assembly flange and said open rearward end 16 of said flashtube, and 17 e) wherein said flashtube liner (30) is comprised of a high density polyethylene is material 19 20 16 The primer assembly of claim 15 wherein said flashtube liner (30) has a length 21 greater than 2 inches 22 23 17 The primer assembly of claim 15 wherein said flashtube (14) has a series of 24 perforations in its wall 25 26 18 The primer assembly of claim 15 wherein said flashtube liner (30) comprises an 27 extruded material 28 19. The primer assembly of claim 15 wherein said flashtube liner (30) is constructed using a rotary molding process. 20. The primer assembly of claim 15 wherein said flashtube liner (30) is constructed using a blow molding process.

Inventors: REIDER JOHN L, REIDER, JOHN, L.
Applicants: ALLIANT TECHSYSTEMS INC, ALLIANT TECHSYSTEMS INC.
Application year: 2000
Main classification: F42C19
IPC codes: F42C19