US3901153A

US3901153A - Wrapped laminated felted monolithic combustible cartridge case

Info

Publication number: US3901153A
Application number: US447423A
Authority: US
Inventors: Robert I Brabets; Seymour Levine
Original assignee: US Air Force
Current assignee: US Air Force
Priority date: 1972-10-04
Filing date: 1974-03-01
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26

Abstract

A combustible cartridge case for use with a fully telescoped round of ammunition wherein the laminated case is fabricated by wrapping thin sheets of felted combustible material. Flame penetration is moderated by applying thin films of deterrent material such as mylar between the layers to permit programmed energy release for specific tailoring of various ordnance requirements.

Description

United States Patent Brabets et al.

[ Aug. 26, 1975 WRAPPED LAMINATED FELTED MONOLITI-IIC COMBUSTIBLE CARTRIDGE CASE Inventors: Robert I. Brabets, Lombard;

Seymour Levine, Chicago, both of I11.

Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, DC.

Filed: Mar. 1, 1974 Appl. No.: 447,423

Related U.S. Application Data Continuation-impart of Ser. No, 295,077, Oct 4.

1972, abandoned.

U.S. C1. 102/38; 102/40; 102/103; 102/D1G. 1

Int. CL F42B 5/02 Field of Search 102/38, 40, 43, DIG. l, l02/100103;149/14,15,16,100

References Cited UNITED STATES PATENTS 2/1902 Maxim l02/DIG. l X

3,264,993 8/1966 DeFrics 102/DIG. l X

3,293,056 12/1966 Baker l 1011/1316. 1 X

3,316,842 5/1967 Schulz v 102/100 3,493,446 2/1970 Braun r v 102/103 X 3,628,456 12/1971 Harrell.... A. l02/DIG. l X 3,677,010 7/1972 Fink 102/103 3,714,047 l/l973 Marion et al. H 102/103 FOREIGN PATENTS OR APPLICATIONS 543,739 3/1942 United Kingdom Primary Examiner-Robert F. Stahl Assistant E.\'aminerHarold Tudor Attorney, Agent, or Firm-Joseph E. Rusz; Arsen Tashjian 57 ABSTRACT A combustible cartridge case for use with a fully telescoped round of ammunition wherein the laminated case is fabricated by wrapping thin sheets of felted combustible material. Flame penetration is moderated by applying thin films of deterrent material such as mylar between the layers to permit programmed energy release for specific tailoring of various ordnance requirements.

5 Claims, 2 Drawing Figures WRAPPED LAMINATED FELTED MONOLITHIC CONIBUSTIBLE CARTRIDGE CASE This application is a continuation-in-part of copending application Ser. No. 295,077, filed Oct. 4, 1972, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a wrapped laminated felted monolithic combustible cartridge case for use with a fully telescoped round of ammunition and, more particularly, the invention is concerned with providing a combustible cartridge case which is fabricated by wrapping thin sheets of felted combustible material into layers with deterrent films of mylar, cellophane, polyethylene, polyurethane or the like between the layers to moderate the flame penetration. Increased axial stiffness is achieved which improves the primer-igniter energy transfer efficiency.

Caseless ammunition has long been recognized as the most advantageous means for improving the firepower and performance of high speed automatic weapons. The elimination of the need for extraction and ejection of spent cartridge cases makes the higher firing rates possible. Also, the caseless type ammunition is light in weight and easier to transport and the problem of disposing of spent cartridges is eliminated.

One of the major problems in the development of caseless ammunition has been the achievement of satisfactory muzzle velocity maximum pressure requirements in weapons which use this type of ammunition. This is primarily the result of the more or less fixed ballistic characteristics of the cartridge propellant. The addition of more propellant only increases the peak pressure and adds nothing to the improvement of performance of the weapon. In certain instances the peak pressure will be increased to a point where the weapon is no longer capable of proper operation. Also, the conventional propellant used in the manufacture of combustible cartridge cases is inherently weak as far as its physical properties are concerned. Thus, it would be most desirable and a step forward in the art to provide a combustible cartridge case wherein the propellant could be modified to obtain a more efficient muzzle velocity/maximum pressure ratio without adding weight to the round or substantially increasing the peak pressure. This would be particularly advantageous if it could be accomplished while at the same time adding to the physical strength of the caseless cartridge.

Accordingly, it is an object of the present invention to provide a telescoped round of caseless ammunition wherein the combustible case is fabricated by wrapping thin sheets of felted combustible material in a plurality of layers with deterrent films between the layers to moderate the flame penetration.

Another object of the invention is to provide a combustible cartridge case of multiple wrapped laminated construction wherein the individual layer formulation and density are tailored to control the rate of gas generation.

Still another object of the invention is to provide a combustible cartridge case fabricated by wrapping felted combustible material, such as nitrocellulose, to form laminates. The laminates thus formed operate to increase the axial stiffness of the case allowing greater flexibility in the use of a combustible primer by improving the primer-igniter energy transfer efficiency.

A further object of the invention is to provide a combustible cartridge case having a laminated configuration wherein the flexibility of a programmed energy release makes the concept suitable for specific tailoring to other types of ordnance requirements.

A still further object of the invention is to provide a telescoped round of caseless ammunition wherein a monolithic combustible cartridge case is fabricated by wrapping sheets of material into three separate layers of felted material including an inner layer, a midlayer and an outer layer. A deterrent film is applied between adjacent layers to moderate flame penetration.

These and other objects, features and advantages will become more apparent after considering the following detailed description taken in conjunction with the annexed drawing and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in longitudinal section of a laminated cartridge case according to the invention showing the plurality of laminated layers of felted material; and

FIG. 2 is a view in cross section taken along the line 2-2 of FIG. 1 showing the three layers with deterrent films therebetween.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, the hereinafter disclosed wrapped laminated felted monolithic combustible cartridge case for use with caseless ammunition includes a fully telescoped round of ammunition wherein a projectile 13 is positioned in the axial bore 15 of the laminated cartridge case 17. The cartridge case 17 is fabricated by wrapping thin sheets of combustible material such as nitrocellulose. In a preferred embodiment shown in FIG. 1, there are three separate laminated layers of combustible material. The inner layer 19 which is positioned closest to the projectile 13 is formed initially by wrapping felted combustible material to the required thickness. A thin film of deterrent 21 may be applied to the outer surface of the layer 19 for the purpose of moderating the flame penetration to the next adjacent layer which is called the midlayer 23. Some materials suitable for use as the deterrent film include mylar, cellophane, polyethylene film and polyurethane. Mylar is a polyester film of polyethylene terephalate resin manufactured by E. I. DuPont, Inc. Cellophane is a cellulon film and polyurethane is a film of polyurethane resin. The midlayer 23 is also formed by wrapping felted combustible material to a predetermined thickness. Another thin film of deterrent 25 made of material similar to film 21 is applied to the outer surface of the midlayer 23. An outer layer 27 is formed by wrapping the felted combustible material around the midlayer 23 until the final outer diameter of the cartridge case 17 is configurated.

A combustible material suitable for use in fabricating the laminated layers is made by felting on a form from a water slurry of nitrocellulose fiber, acrylic fiber, resins and stabilizer to make a rough preform. This preform is subsequently molded under suitable conditions of temperature and pressure in appropriate molds to form sheets which may be furnished by trimming, if necessary. A typical final composition would fall within the following:

Parts by Weight Range Nitrocellulose (12.6% N 70 55-85 Acrylic Fiber 20 5-35 Resin l0 Stabilizer (N,N diethylcarbamate) l Silicone Resin 4 American Cyunumid: Creslan T 'JS Fibrillatable Fiber. Kraft fiber (cellulose) may be substituted for the acrylic in like amounts B. F. Goodrich, Avon Lake, Ohio: Hycar 2600x186 Dow Corning, Mcdland, Mich.: Down Corning B Silicone It can be seen that the properties of the combustible material can be varied within a wide range to adjust the interior ballistics of the cartridge case 17 as well as allowing effective control of peak pressures and muzzle velocity of the round. The thickness of the

deterrent films

21 and 25 can be varied between 0.0005 and 0.0010 inches as a means of further controlling the rate of gas generation by moderating the flame penetration between the layers. Also, by choosing a deterrent film of suitable composition, the flame penetration rate can be still further controlled. Thus, by tailoring the individual layer formulation and density within the ranges noted and by choosing deterrent films of suitable composition and thickness, an extremely flexible energy release program can be achieved which allows the design to be utilized in many types of ordnance structures.

Also, it should be noted that the projectile 13 is provided with a threaded axial recess (not shown) in the center of its base portion. A set screw 29 is threaded into the axial recess and extends aft beyond the base of the projectile 13 to form a threaded boss thereon. A tubular igniter 31 of felted nitrocellulose is positioned in the rearwardmost part of the axial bore 15, and includes an internally threaded forward section which engages the threads on the set screw 29. Within the bore of the tubular igniter 31 at the base thereof, a shoulder 33 engages a primer 35, preferably of the combustible type, such that the primer 35 is in a fixed position and the action of the firing pin (not shown) can effectively operate to crush it on impact. Most of the forward section of the igniter tube 31 is filled with a standoff igniter charge of a PG black powder. Surrounding the outer surface of the igniter tube 31, there is positioned a supplementary charge 37 which is in contact with the inner surface of the inner layer 19 of the laminated cartridge case 17.

When the telescoped round is assembled, the projectile 13 is inserted base downward into the axial bore of the duplex cartridge case 17. A diametral flange 39 which is the rear shoulder of the rotating band on the projectile 13 engages a shoulder 41 on the internal surface of the laminated cartridge case 17 and stops further downward movement. The igniter tube 31 is then threadably attached to the set screw 29 which had previously been fixedly positioned on the base of the projectile 13. The igniter tube 31 is tightened in position by using a spanner-type wrench which fits into the openings 43 in the base of the igniter tube 31. The operation of turning the igniter tube 31 causes the diametral flange 39 of the projectile 13 to be drawn against the shoulder 41 while the base portion of the igniter tube is pressed against the shoulder 45 locking all of the elements in position. This procedure effectively loads the central portion of the igniter 31 in tension and the forward section through the threads are loaded in shear to produce a stress pattern which is well able to withstand ramming. At the same time, quick opening effects are achieved by the internal pressurization of the igniter tube 31 very early in the ballistic cycle.

In accordance with the invention, the laminated cartridge case 17 can be prepared by wrapping thin sheets of felted combustible material to a predetermined thickness. The finished cartridge case can be made in three layers, the inner layer, midlayer and outer layer. Moderation of the flame penetration is achieved by applying deterrent films of various compositions and thickness to the surfaces of the laminated layers which contact the next adjacent layer. Although a three layer laminated cartridge case is suggested, it should be apparent that more or less than three layers would be desirable under certain specific ballistic conditions. Also, the need for molded propellants is entirely eliminated while at the same time a much improved structural configuration with far greater physical strength is obtained.

In the laminated cartridge case 17, the individual layer formulation and density can be easily tailored to control the rate of gas generation. Also, the hereinbefore described case places less constraint on the use of a combustible primer since the increased axial stiffness improves the primer-igniter energy transfer efficiency.

Although the invention has been illustrated in terms of a preferred embodiment thereof, the invention is not limited to this embodiment or to the preferred configuration shown. For example, it will be apparent to those skilled in the art that our invention provides a means for increasing the muzzle velocity of the weapon without substantially increasing the peak pressure by using caseless ammunition of the laminated type. In effect, with this design, a progressive burning geometry propellant is achieved with a corresponding increase in gun performance. Also, it should be understood that various changes, alterations, modifications and substitutions, particularly with respect to the construction details can be made in the arrangement of the several elements without departing from the true spirit and scope of the appended claims.

Having thus described our invention what we claim and desire to secure by Letters Patent of the United States is:

1. A wrapped laminated felted monolithic combustible cartridge case for a fully telescoped round of ammunition comprising, in combination:

a laminated propellant charge of substantially cylindrical configuration with an axial bore, therethrough and having a plurality of concentric layers,

the first of said concentric layers being an inner layer comprising a series of laminations of sheet combustible material having an inside diameter substantially equal to the outside diameter of the projectile in said telescoped round and wrapped to a predetermined thickness,

a first deterrent film on the outer surface of said first concentric layer,

the second of said layers being a midlayer immediately adjacent the outer surface of said first deterrent film, said midlayer comprising a series of laminations of sheet combustible material wrapped to a predetermined thickness,

a second deterrent film on the outer surface of said second concentric layer, and

the third of said layers being an outer layer immediately adjacent the outer surface of said second denitrocellulose fiber, acrylic fiber, resins and stabilizer.

3. The laminated cartridge case defined in claim 1 wherein each of said first and second deterrent films is composed of a polyester film of polyethylene terephalate resin.

4. The laminated cartridge case defined in claim 1 wherein each of said first and second deterrent films is composed of a cellulose film.

5. The laminated cartridge case defined in claim 3 wherein the thickness of each of said first and second polyester films of polyethylene terephalate resin is in the range between 0.0005 and 0.0010 inches.

Claims

1. A wrapped laminated felted monolithic combustible cartridge case for a fully telescoped round of ammunition comprising, in combination: a laminated propellant charge of substantially cylindrical configuration with an axial bore therethrough and having a plurality of concentric layers, the first of said concentric layers being an inner layer comprising a series of laminations of sheet combustible material having an inside diameter substantially equal to the outside diameter of the projectile in said telescoped round and wrapped to a predetermined thickness, a first deterrent film on the outer surface of said first concentric layer, the second of said layers being a midlayer immediately adjacent the outer surface of said first deterrent film, said midlayer comprising a series of laminations of sheet combustible material wrapped to a predetermined thickness, a second deterrent film on the outer surface of said second concentric layer, and the third of said layers being an outer layer immediately adjacent the outer surface of said second deterrent film, said outerlayer comprising a series of laminations of sheet combustible material wrapped to a thickness equal to the outside diameter of said cartridge case, said first and second deterrent films operating to moderate the flame penetration to each of the next adjacent layers of combustible material, thereby effectively controlling the rate of gas generation to provide increased muzzle velocity without substantially increasing the peak pressure.

2. The laminated cartridge case defined in claim 1 wherein the laminations of sheet combustible material in the plurality of layers include a composition of felted nitrocellulose fiber, acrylic fiber, resins and stabilizer.