US 3830157 A
An aluminum alloy cartridge case having a thin coating lining a substantial portion of the case internal surface to minimize operative erosion damage to the case material by hot gases escaping, should the case develop a crack when the round is fired. The coating consists of synthetic and natural resins and an additive which serve to endothermically cool the high velocity hot gases escaping through the crack.
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Description (OCR text may contain errors)
titted States atent 1 Donnard et a1.
[4 1 Aug. 20, 19741 CARTRIDGE CASE  Inventors: Reed E. Donnard, Huntingdon Valley; Marvin Rosenbaum, Philadelphia; Anthony Gallaccio, Havertown; Fred Pealstein, Philadelphia, all of Pa.
 Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.
22 Filed: Oct. 31, 1972 211 App]. No.: 302,455
 U.S. Cl 102/43, 102/43 P  Int. Cl. F42b 5/26  Field of Search 102/43, 43 P, DlG. 7, 38
 References Cited UNITED STATES PATENTS 4/1940 Korpiun 102/43 R 3,209,689 10/1965 McLennan 102/38 3,282,215 11/1966 Roth 102/38 3,362,328 1/1968 KatZ .0 102/38 Primary Examiner-Robert F. Stahl Attorney, Agent, or Firm-Edward J. Kelly; Herbert Berl; William Sommer [5 7 ABSTRACT An aluminum alloy cartridge case having a thin coating lining a substantial portion of the case internal surface to minimize operative erosion damage to the case material by hot gases escaping, should the case develop a crack when the round is tired. The coating consists of synthetic and natural resins and an additive which serve to endothermically cool the high velocity hot gases escaping through the crack.
1 Claim, 1 Drawing Figure CARTRIDGE CASE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.
This invention relates to cartridge cases, and more particularly to ammunition cartridge cases of aluminum alloy material.
Because of the extremely high production rate of ammunition cartridge cases, flaws and other undesirable physical conditions sometimes result in the cases during the manufacturing process and pass undetected through elaborate inspection procedures. The flaws of interest to this invention consist of small faults that are either in the case wall structure as manufactured or are other forms of defects in the material that can lead to cracks in the case wall structure when the ammunition is fired. The fissure or crack, particularly at the region of the case just forward of the extractor groove, can be severely eroded by escaping hot gases. This condition is most serious with light-weight metal cartridge cases such as aluminum alloys where there is damage to the weapon bolt face, chamber, moving parts and sliding surfaces which usually make the weapon inoperable. More seriously there is the high probability that the escaping high velocity hot propellant gases can seriously injure the weapon operator.
It is an object of the invention to provide a cartridge case with an internal coating which will minimize erosion of the case in the event of case failure.
Another object of the invention is to provide such a cartridge case in which the coating reacts with hot gases adjacent a crack and insulates the case surfaces at the crack, reduces the temperature of the gas escaping through the crack by appreciable energy absorption, by the vaporization of the coating and by the injection of coating vapor into the propellant gas boundary layer which effectively prevents a large fraction of heat from reaching the cracked surface.
These and other objects, features and advantages will become more apparent from the following description and associated drawing in which the sole FIGURE is a longitudinal sectional view of a cartridge case embodying the principles of the invention.
The ammunition round, shown generally at 10, comprises an aluminum alloy cartridge case 11 having a primer assembly 12, propellant charge 14 and a fluid communicating vent hole 13 provided in the central portion of the cartridge case base 15. An appropriate projectile 16 is secured in the reduced mouth portion 17 of the cartridge case sidewall 18. The major portion of the cartridge case internal surface, from the vent hole to substantially the case mouth, is provided with a thin protective coating 19, the minimum thickness being approximately 0.008 inch, that will provide ablative, insulating, reflective and endothermic characteristics to eliminate or minimize erosive damage to the case particularly at an area where a crack might occur.
More specifically, the coating consists of a base matrix which has synthetic and natural resins and several reactive additives, particularly an endothermic reactant selected from a group of organic phosphates and inorganic carbonates that includes alkyd or aryl phosphate and hydrated sodium carbonate. The preferred coating has the following constituents with the designated weight percentages:
chlorinated paraffin 8.75 dipentaerythritol 8.20 melamine 8.75 chlorinated polypropylene 2.85 synthetic styrenated rubber 4.25 alkyd phosphate 28.80 titanium dioxide 6.40 toluene 16,00 xylene 16 The natural resins, melamine and dipentaerythritol, are burning rate regulators and have ablative and endothermic characteristics as do the synthetic resins (chlorinated paraffin, chlorinated polypropylene and synthetic styrenated rubber). Endothermic additive, alkyd phosphate has reflective and insulating characteristics, as does the titanium dioxide. The toluene and xylene are solvents which evaporate upon drying.
Various modifications, alterations or changes may be resorted to without departing from the scope of the invention as defined in the appended claims.
1. In a cartridge case having an aluminum alloy base and sidewall construction, said base having a primer cavity in fluid communication with a propellant chamber defined by the internal surface portions of said case,
a thin coating lining a substantial portion of said case internal surface, said coating consisting of alkyd phosphate, chlorinated paraffin, dipentaerythritol, melamine, chlorinated polypropylene, synthetic styrenated rubber, titanium dioxide, toluene, and xylene,
so constructed and arranged that operative erosion damage to cracked material of the case is minimized.