Patent Publication Number: US-3877375-A

Title: Primer

Description:
United States Patent Barr Apr. 15, 1975 [541 PRIMER FOREIGN PATENTS OR APPLICATIONS lnvemorl Irwin Luthervillfi, 179,581 5/1922 United Kingdom 102/49.7 [73] Assignee: AAI Corporation, Cockeysville, Md.  
  Primary Examiner-Robert F. Stahl [22] Flled: 1973 Attorney, Agent, or Firm-Regina1d F. Pippin, Jr.  
 [63] Continuation of Ser. No. 193920, Oct. 29, 1971, abandoned, which is a continuationin-part of Scr. No. 849,694, Aug. 13, 1969, abandoned.  
 [52] U.S.Cl. 102/45 [51] Int. Cl. F42c 19/10 [58] Field of Search 102/38, 49.3-49.7, 102/45, 86.5, 44  
 [56] References Cited UNITED STATES PATENTS 1,461,013 7/1923 Hodge 102/45 2,708,878 5/1955 Eckstein 102/45 3,486,453 12/1969 Smal1wood........ 102/45 X 15 ll |3b l5c 15d [57] ABSTRACT An anvil-less percussive ignition primer is provided having a cup-shaped body which is closed at one end and open at its opposite end, the body having a compact primer mixture held therein and having no anvil therein. The closed rear end of the primer is deformable, the primer body retains its structural integrity during and after firing, and the compact primer mixture is ignitable by abrupt external inwardly directed deformation of the closed rear end of the cup-shaped body. The primer is disposed in the rear of a cartridge, with its anvil-less open forward end facing a charge of propellant powder ignited by percussive ignition of the anvil-less primer.  
 10 Claims, 5 Drawing Figures PATENTEB 1 W5 3.877. 375  
 sum 2 o 2 ll 1 4m 4 Irwin R. Barr INVENTOR ATTORNEY PRIMER This application is a continuation of my co-pending application Ser. No. l93,920, originally filed Oct. 29, 1971, now abandoned, which in turn is a continuation of prior application Ser. No. 849,694, filed Aug. 13, 1969, now abandoned.  
  This invention relates to percussive primers for use in gun or other weapon-fired and usable cartridges or other devices which require flash ignition of propellant powder or the like.  
  While percussive primer arrangements suitable for gun or other weapon-fired cartridge firing use and using primer mixtures have long existed, on prior primers to my knowledge they have had an anvil of some type, in the sense of being one of two discrete and relatively movable interfacing parts or elements forming and/or lying within the effective primer mixture containment and percussive firing movement zone, one of which discrete parts or elements acts as in the nature of an anvil for percussive striking by, and/or percussive sliding surface interaction with, the other discrete element, whether the anvil be a circumferential rim-like anvil, a unitary conventional conical anvil. an internal corrugated sheet at and facing a portion of the rear wall of the primer cup for relative motion therebetween, or some other type to enable the firing pin to ignite the primer charge, which in turn flashes and ignites the propellant within a cartridge or the like to create a desired high gas pressure or other activating force. To obtain the simplest and least expensive gun-cartridge usable primer arrangement, it is highly desirable that the primer be easily and simply constructed of as few parts as possible to facilitate the manufacture of the primer and hence reduce production costs. Primers of this na ture differ fundamentally from stab detonators commonly used in explosives detonation or other work, in that the stab detonators are fired by stab penetration of the detonator containment body and direct penetration of the firing mix by a sharp pointed stab pin to cause firing of the firing mix therein, with resultant destruction of the stab detonator containment body integrity and escape of the gases therethrough, independent of its subsequent total destruction by the further compound which may be detonated or fired thereby.  
  It is a feature of the present invention to provide a weapon-usable cartridge primer having an integral onepiece cup formed of malleable material which retains its structural integrity and does not disintegrate or rupture on firing, and using a primer mixture therein, as distinguished from a detonator or detonating mixture or chemical as such terms primer mixture, detonator or detonating mixture are normally used in the ordnance art, and as distinquished from stab detonators, and which primer is devoid of an anvil in any normal sense of the word, whereby to substantially reduce the number of primer parts and cost of production.  
  Still another feature of the invention is the provision of a primer which retains its structural integrity on firing and which is suitable for conventional cartridge firing use, which primer has an integral one-piece cup formed of malleable material and which does not disintegrate or rupture on firing, and which primer cup has a compact primer mixture mass therein, as distinguished from a detonator or detonating mixture or chemical, and which integral-one-piece-cup primer is devoid of an anvil in any normal sense of the word,  
 whereby to substantially reduce the number of primer parts and cost of production, while retaining the essential operational features of structural integrity, percussive firing within the range of normally acceptable firing pin energies, and the enablement of use of generally relatively and acceptably safe primer mixtures.  
  The primer is illustrated in conjunction with a cartridge in which the primer has a construction enabling it to function as a movable piston. Thus, in the presently illustrated embodiment in which the primer according to the invention is utilized in one potential application, a cartridge is provided having a casing with a pair of longitudinally arranged coaxial bores connected by an annular beveled shoulder with the larger diameter bore being formed in the forward portion of the casing and containing a propellant and with the smaller diameter bore being formed in the base portion of the casing and having a movable cup-shaped anvilless piston primer disposed therein which opens toward the interior of the casing and contains a primer mixture adapted to be ignited to fire the propellant in the larger diameter bore. The movable cup-shaped anvil-less piston primer has a deformation resistant tubular wall portion freely slidably engaging the smaller diameter bore with a relatively thinner and more easily deformable web-like base portion at the rearward end thereof which is adapted to be indented upon being struck by the head of the firing pin to ignite the primer charge. At the open end of the tubular wall portion is formed an annular flared obturating flange portion with only a small circumferential surface area slidably engaging the larger diameter bore in a light interference fit which provides a gas sealing action and minimizes the energy losses resulting from friction between the movable anvil-less primer and the cartridge casing while at the same time providing a larger cross-sectional area throughout which the propellant gas can act. Alternatively, the light interference fit at the open flared obturator flange end may be a fit with a very small (e.g., up to approximately 0.005 in.) diametral clearance relative to the bore, as the flared obturator portion of the anvilless piston primer is readily deformable under the propellant gas pressure and this effects a seal and interference fit with the bore even in the instance of original small clearance. The forward longitudinal movement of the piston primer is limited by a stop formed in the larger diameter bore for engagement by the forward edge of the flared flange portion of the piston primer, while the rearward longitudinal movement of the piston primer is limited by the engagement of the back side of the flared obturating flange portion with the annular beveled shoulder connecting the coaxial bores.  
  When the head of a firing pin having a protrusion formed thereon strikes the base of the movable cupshaped anvil-less piston primer at the end of a forward stroke, an indentation is formed in the relatively thin web-like base wall that ignites the primer charge which, in turn, fires the propellant to create a high gas pressure that propels a projectile from the cartridge casing while at the same time acting across the full cross-sectional area of the larger diameter propellant-containing bore to exert a maximum force against the anvil-less piston primer and drive it rearwardly. Since the obturating flange portion of the movable primer has only a small cicrumferential surface area engaging the larger diame ter bore in an interference fit, and the deformation resistant cylindrical portion of the movable primer freely slidably engages the smaller diameter bore, the retarding frictional forces incurred during the rearward movement of the anvil-less piston primer are minimized to enable it to drive the firing pin backward in a return stroke and transfer a maximum amount of energy to operate the breech mechanism, extract the spent cartridge, cock the firearm and chamber another cartridge.  
  Still other objects, features, and attendant advantages will become apparent to those skilled in the art from a reading of the following detailed description of several physical embodiments constructed in accordance with the present invention. taken in conjunction with the accompanying drawings wherein:  
  FIG. 1 is a longitudinal cut-away view of a cartridge employing an anvil-less primer according to the invention.  
  FIG. 1a is a side view partially cut-away of the forward end of a firing pin. for percussion firing of the cartridge of FIG. 1. according to the invention.  
  FIG. 2 shows the cartridge of FIG. I inserted in the chamber of a firearm with a bolt engaging the base of the cartridge and having a firing pin in the ready position.  
  FIG. 3 is a view similar to FIG. 2, showing the firing pin striking the base of the movable primer and igniting the propellant to provide the projectile-propelling high gas pressure.  
  FIG. 4 is a view similar to FIGS. 2 and 3, showing the movable primer propelled rearward by the propellant gas pressure which forces the firing pin backward in a return stroke.  
  Referring now in detail to the figures of the drawings, in FIG. 1 is shown a cartridge suitable for use in a firearm which is operated on the primer set-back and energy transfer principle. The cartridge, generally indicated at 11, includes a casing. generally indicated at 13, containing a movable single-unit anvil-less piston primer, generally indicated at 15, a projectile 21 and a propellant 31 disposed between the movable anvil-less piston primer l5 and the projectile 21. The cartridge casing 13 has two coaxial bores of different diameters, indicated respectively at 13a and 130, and connected through an annular beveled shoulder 13b, with the smaller guide bore 130 being located at the rear or base of the cartridge casing 13 and the larger propellantretaining bore 13a being located at the forward end of the casing 13 and adapted to securely grip an annular groove 21a ofthe projectile 21 by means of an annular indentation 130&#39;.  
  The movable single-unit cup-shaped anvil-less piston primer has an integral one-piece unitary cup having a cylindrical anvil-less piston guiding portion 15a opening forwardly toward the interior of the larger diameter propellant containing bore 13a with an annular flared obturating flange portion 151) formed at the forward open end thereof, and with a web-like base wall 151&#39; formed integrally at and across the full rearward end thereof. The cylindrical piston guiding portion 15a of the primer 15 is freely slidably disposed in the small diameter bore 130 at the rear of the cartridge casing 13 while the edge of the flared flange portion 15b slidably engages the larger diameter bore 13a in a light interference fit to provide a good movable gas pressure seal. In its unfired position, the edge of the flared flange portion 15b engages an annular forward shoulder stop as shown at 13e, or alternatively, circumferentially spaced dimple stops, which limit the forward motion of the primer piston.  
  Inside the thick-walled cylindrical. piston-guiding portion 15a is formed a cylindrical cavity 15d having a length generally greater than the diameter of the cylindrical cavity 15d, although this is not necessarily required. Compacted within the cylindrical cavity 15d is a primer charge 17 of a primer mixture, which may be of conventional primer mixture composition, but which may if desired contain a small mixture of grit to enhance the reliability of firing of the primer at normal firing pin energy levels, although the grit is not necessary to operability, particularly at firing pin energy levels in the upper normal firing pin energy range. The degree of compaction of the primer charge 17 is variable, but desirable it should be as great as possible without resulting in accidental ignition during the manufacture of the cartridge. The primer charge 17 contained in the cylindrical cavity 15d is separated from the propellant 31 contained in the larger diameter bore 13a of the cartridge casing by a thin easily frangible. and preferably combustible moisture seal 19 of suitable material. such as a coating of wax or Krylon. While the moisture seal 19 is not absolutely required for functional operation, it is desirable to aid against malfunction due to undesired moisture absorption by the primer charge 17 which, for example, might occur during assembly.  
  The integral one-piece cup-shaped body of primer 15 may be suitably formed of various materials, dependent upon the tensile strength required, it being of course necessary that the primer retain its body integrity when fired, so as to maintain a propellant gas seal with a cartridge in which it may be fitted or formed. For peak propellant burning pressures of the order of approximately 50,000 70,000 psi a high tensile strength steel such as medium to high carbon steel (e.g., 1050 steel, 1065 steel), heat treatable alloy steels and precipitation hardening steels. are suitable. For lower peak propellant pressures as of the order of 40,000 psi or less the cup body of primer 15 may be formed of brass or other material of lower tensile strength properties.  
  In FIGS. 2-4 is illustrated the operation of the cartridge 11 shown in FIG. 1. In FIG. 2 the cartridge 11 is shown inserted in a chamber 41a of a conventional barrel 41 with a bolt 51 pressed against the base of the cartridge casing 13 and having extractor fingers 5111 engaging an extractor groove 13fformed in the rear of the cartridge casing 13. Disposed inside the bolt 51 is a firing pin 61 having a head 61a with a protrusion 61b in the center thereof for striking the easily deformable and relatively thin-walled web-like base 15c of the cupshaped anvil-less piston primer 15 to ignite the primer charge 17 and fire the propellant 31.  
  In FIG. 3 is shown the head 61a of the firing pin 61 striking the relatively thin-walled web-like base wall 150 of the movable anvil-less piston primer 15 at the end of a forward stroke. The protrusion 61b formed on the head 61a of the firing pin 61 makes an indentation in the integral and closed web-like base wall 15c of the anvil-less piston primer 15 to ignite the primer charge 17. The utilization of all of the available energy of the forward stroke of the firing pin 61 to form an indentation in the integral web-like base wall 150 of the anvilless piston primer 15 is insured by the engagement of the end of the annular flared flange portion 15b of the anvil-less piston primer 15 with the annular shoulder 13e formed in the large diameter bore which prevents forward movement of the anvil-less piston primer 15.  
  The exact manner in which the primer charge 17 is ignited without the requirement for an anvil is not fully understood, but it is thought that the indentation formed in the relatively thin-walled web-like integral and continuous base wall 150 of the movable anvil-less integral unitary piston primer causes primer ignition through imparting relative movement between particles in the primer charge 17, as by causing a column of primer charge particles in the cylindrical cavity 15d to move in relation to other primer charge particles nearer the periphery of the cylindrical cavity 151! which remain generally stationary due to the friction between the primer charge 17 and the wall of the cylindrical cavity 15d, and that the resulting abrupt friction be tween the moving and stationary primer charge particles generates a sufficient heat to ignite the primer charge 17, or as by abrupt relative motion and compaction of a quantity of primer particles at the rear end of the primer charge cavity adjacent integral web 150. with these rear centrally disposed particles being moved in compaction against the restraint exerted by the remaining forward mass of primer charge particles in the highly compacted columnar mass 17 of primer charge particles.  
  However. irrespective of the theory by which the primer charge 17 is ignited, the anvil-less ignition of the primer charge 17 ruptures the moisture seal 19 and fires the propellant 31 which generates a high gas pressure that propels the projectile 21 forward with suffi cient force to disengage the annular indentation 13c which grips the annular groove 21a of the projectile 21. In addition, the high pressure propellant gas obturates the annular flared flange 15b of the primer 15 against the large diameter bore 13a of the cartridge casing 13, thereby preventing gas leakage to the rear of the movable anvil-less piston primer 15, and at the same time act across the full cross&#39;section area of the propellant chamber to imparta maximum amount or rearward force to the primer. Since the cylindrical anvil-less piston portion 150 has a relatively thick-walled deformation resistant construction, it resists expansion by the high gas pressure against the propellant 31, and remains easily slidable within the small diameter bore to deliver a maximum amount of force to the firing pin 61 to drive it backward in a return stroke.  
 Since a sufficient indentation must be made in the &#39;web-like base wall 15c of the piston primer 15 to ignite the primer charge 17, yet not exceed the elongation or shear limits of the material, the contour of-the protrusion 61b formed on the head 61a of the firing pin 61 are of importance. The diameter and the amount of the protrusion formed on the surface of the head must be sufficient to cause adequate compacting or internal relative movement of the primer charge particles within the cavity 15d to cause ignition of the primer charge,  
 yet the annular edges or corners such as 61c, 61d on the protrusion 61b should be rounded or chambered to prevent shearing failures of the relatively thin web-like base wall. Also, the diameter of the head 61a of the firing pin 61b preferably extends across the rear face of the primer 15 to provide an adequate support for the piston primer to prevent upon ignition, possible rupture by the resultant high pressure propellant gas.  
  As the cup-shaped anvil-less piston primer is propelled rearwardly by the high pressure propellant gas,  
 it drives the firing pin backward in a return stroke to operate the breech mechanism and/or other components of the firearm. Initially, the relatively thin-walled web-like base wall 15c is prevented from rupturing due to the support provided byv engagement with the base of the firing pin.  
  Upon engagement of the flared flange portion-15b with the beveled shoulder 13b, the rearward motion of the anvil-less piston primer stops and the head of the firing pin 61 no longer provides support for the relatively thin-walled web-like base wall 15c since it continues its rearward motion, however, the forward motion ofthe projectile 21 through the barrel 41 increases the volume throughout which the propellant gas can expand and consequently when the rearward motion of the anvil-less piston primer stops the propellant gas pressure is reduced sufficiently to eliminate a possible rupture of the relatively thin-walled web-like integral base wall of the anvil-less piston primer.  
  In one preferred mode of practicing the present invention, an integral anvil-less piston primer is formed from 1065 steel which is heat treated to R,. 32-36 and having a cylindrical wall 15a of an outer diameter of 0.170 inch, an obturating flared flange portion 15b of a diameter of 0.223 inch, and a relatively thin integral web-like base wall 150 of 0.014 inch thick. A cylindrical cavity 15d is formed inside the anvil-less piston primer with a diameter of 0.093 inch. lnside the cavity, 0.04 grams of dried primer charge are compacted with a pressure of the order of from 125.000 to 175,000 psi, and the length/diameter ratio of the cylindrical primer charge 17 is in the range of approximately 1.5 to 2.0. The preferred embodiment primer mixture composition consists of the following ingredients in the indicated proportions:  
 EXAMPLE 1 Ingredient &#34;/1 Dry Wt.  
 Lead Styphnate, Normal (sensitive high 37 5 Tetracene (sensitive high explosive) 4 i l Barium Nitrate (oxidizer) 32 i 5 Antimony Sulfide (abrasive &amp; exothermic 15 i 2 Aluminum Powder (exothermic fuel) 7 i l PETN (Class 2) (high energy yield high 5 :L l  
 explosive) This is a composition now generally known as FA- 956, except that it does not include a light gum solution which is normally utilized in FA-956 per se.  
 An alternative workable composition is as follows:  
 explosive With the illustrative example, the associated firing pin used in conjunction with the cartridge impacts the movable primer with an input energy of48 inch-ounces and has a diameter of 0.155 inch with a protrusion extending approximately 0.012 inch from the head of the firing pin with a diameter of 0.060 inch. The base radius of curvature 61d of the protrusion 61h on the firing pin 61 is 0.020 inch, while the radius ofcurvature at the extended rim surface 610 of the protrusion is 0.005 inch.  
  While the invention has been illustrated and described with respect to a single preferred embodiment, it will be apparent to those skilled in the art that other embodiments and various modifications and improvements may be made without departing from the scope and spirit of the invention. For example. the cavity within the relatively thin-walled cylindrical piston portion of the anvil-less primer may not necessarily be cylindrical but may assume a variety of shapes. Also, the moisture seal need not be combustible but may be of very thin relatively non-combustible easily frangible material such as Chapmans red lacquer, epoxy or metal foil which offers substantially no resistance analogous to or which in any manner would function as an anvil for the ignition of the primer mix. The composition of the primer charge may be varied to produce more, or less if desired. friction between the moving particles of the primer charge. In addition, while the anvil-less primer of the invention has been illustrated in an embodiment utilizing a movable piston primer construction, it will be readily apparent that a fixed primer construction may be embodied in which the flared obturating flange may be omitted. Accordingly, it is to be understood that the invention is not to be limited by the single preferred illustrative embodiment but only by the scope of the appended Claims.  
 That which is claimed is:  
  1. An anvil-less percussive primer having a cupshaped body portion formed of malleable material of a character and a thickness to maintain its body integrity when the primer is fired, yet sufficiently thin-walled at its closed base to enable percussive dimpling thereof by a firing pin,  
 said cup-shaped body portion containing a compact primer mixture and being effectively open at its forward end and devoid of an anvil, said primer having a closed deformable rear end, and said compact primer mixture having a length greater than its cross-sectional width and being retained as a unit mass within said cup-shaped body in direct engagement with said closed deformable rear end, said compact percussive primer mixture being ignitible as a function of abrupt external inwardly directed non-rupturing, central, percussive dimpling deformation of said closed deformable rear end,  
 said malleable material of said body portion being effectively non-combustible by and upon percussive firing of said primer mixture through said abrupt external inwardly directed deformation of said closed deformable rear end.  
 2. An anvil-less primer according to claim 1,  
 said cup-shaped body portion consisting of a onepiece cup formed of malleable metal.  
 3. An anvil-less primer according to claim 1,  
 said primer mixture having a frangible anvil-less covering thereon.  
 4. An anvil-less primer according to claim 1,  
 said primer mixture comprising the mixture of Example l. 5. An anvil-less primer according to claim 1, said primer mixture comprising the mixture of Example ll. 6. An anvil-less primer according to claim 1,  
 said compact primer mixture comprising an explosive powder constituent, an oxidizer constituent, and an abrasive constituent. 7. An anvil-less primer according to claim 6, said primer mixture further comprising a catalyst constituent for increasing explosive reaction rate between said explosive powder and said oxidizer.  
  8. A cup-shaped body portion formed of a malleable metal ofa character and thickness to maintain its body integrity when fired,  
 said cup-shaped body portion having a compact primer mixture having a length greater than its cross-sectional width and retained therein as a unit mass by compact frictional gripping with the side walls of said cup-shaped body portion being effectively open at its forward end and devoid of an anvil,  
 said cup-shaped body portion having a closed deformable rear end, and  
 said compact primer mixture being ignitable by abrupt percussive external inwardly directed deformation of said closed rear end,  
 said malleable metal forming said cup-shaped body portion being effectively non-combustible by and upon percussive firing of said primer mixture through said abrupt external inwardly directed deformation of said closed deformable rear end.  
  9. An anvil-less primer according to claim 8, said cup-shaped body portion being an integral cup formed of metal.  
  10. An anvil-less primer according to claim 7, said cup-shaped body portion being a one-piece integral cup.  
 UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 2 3,877,375  
 DATED I April 15, 1975 INVENTOR(S) I Irwin R. Barr It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 Column 6, Line 41, after &#34;high&#34; insert --explosive),  
 Column 6, Line 41, change &#34;5-&#34; to -i---.  
 Column 6, Line 57, after &#34;explosive&#34; insert Signed and Scaled this Twelfth Day Of May I981 [SEAL] Amm- RENE D. TEGTME YER Arresting Oflicer Acting Commissioner of Patent: and Trademarks