U.S. patent number 3,877,375 [Application Number 05/389,402] was granted by the patent office on 1975-04-15 for primer.
This patent grant is currently assigned to AAI Corporation. Invention is credited to Irwin R. Barr.
United States Patent |
3,877,375 |
Barr |
April 15, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
PRIMER
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.
Inventors: |
Barr; Irwin R. (Lutherville,
MD) |
Assignee: |
AAI Corporation (Cockeysville,
MD)
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Family
ID: |
26889499 |
Appl.
No.: |
05/389,402 |
Filed: |
August 27, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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193920 |
Oct 29, 1971 |
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849694 |
Aug 13, 1969 |
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Current U.S.
Class: |
102/470 |
Current CPC
Class: |
F42B
5/36 (20130101); F42C 19/10 (20130101) |
Current International
Class: |
F42B
5/00 (20060101); F42B 5/36 (20060101); F42C
19/00 (20060101); F42C 19/10 (20060101); F42c
019/10 () |
Field of
Search: |
;102/38,49.3-49.7,45,86.5,44 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Stahl; Robert F.
Attorney, Agent or Firm: Pippin, Jr.; Reginald F.
Parent Case Text
This application is a continuation of my co-pending application
Ser. No. 193,920, 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.
Claims
That which is claimed is:
1. An anvil-less percussive primer having a cup-shaped 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 one-piece 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 I.
5. An anvil-less primer according to claim 1,
said primer mixture comprising the mixture of Example II.
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 of a
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.
Description
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 nature 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 one-piece 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 anvil-less 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 anvil-less 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 cup-shaped 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 diameter
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. 1 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 15 and the
projectile 21. The cartridge casing 13 has two coaxial bores of
different diameters, indicated respectively at 13a and 13c, and
connected through an annular beveled shoulder 13b, with the smaller
guide bore 13c being located at the rear or base of the cartridge
casing 13 and the larger propellant-retaining bore 13a being
located at the forward end of the casing 13 and adapted to securely
grip an annular groove 21a of the projectile 21 by means of an
annular indentation 13d.
The movable single-unit cup-shaped anvil-less piston primer 15 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 15b formed at the forward open end
thereof, and with a web-like base wall 15c 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 13c 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 51a engaging an extractor groove 13f formed 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 cup-shaped 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 15c 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 15c of the anvil-less 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 13a 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 15c of the movable
anvil-less integral unitary piston primer 15 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 15d 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 between 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 15c, 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 sufficient force to disengage the annular indentation
13e 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-section area of the propellant
chamber to impart a maximum amount or rearward force to the primer.
Since the cylindrical anvil-less piston portion 15c 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 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 by 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 of the
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 15c 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.sub.c 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 15c of 0.014 inch thick. A cylindrical
cavity 15d is formed inside the anvil-less piston primer with a
diameter of 0.093 inch. Inside 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 I
Ingredient % Dry Wt. ______________________________________ Lead
Styphnate, Normal (sensitive high 37 .div. 5 Tetracene (sensitive
high explosive) 4 .+-. 1 Barium Nitrate (oxidizer) 32 .+-. 5
Antimony Sulfide (abrasive & exothermic 15 .+-. 2 fuel)
Aluminum Powder (exothermic fuel) 7 .+-. 1 PETN (Class 2) (high
energy yield high 5 .+-. 1 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:
EXAMPLE II
Ingredient % Dry Wt. ______________________________________ Lead
Styphnate, Normal (sensitive high 31 percent explosive Barium
Nitrate (oxidizer) 19 percent Antimony Sulfide (abrasive &
exothermic 20 percent fuel) Lead Dioxide (oxidizer) 8 percent
Tetracene (sensitive high explosive) 10 percent Zirconium
(catalyst) 8 percent PETN (Class 2) (high energy yield high 4
percent explosive) ______________________________________
With the illustrative example, the associated firing pin used in
conjunction with the cartridge impacts the movable primer with an
input energy of 48 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 61b on the firing pin 61 is 0.020
inch, while the radius of curvature at the extended rim surface 61c
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 Chapman's 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.
* * * * *