Obturated Firearm Breech Safety Device

Abstract

In a firearm comprising a reciprocating bolt, the pin for retaining the eactor against rotation in the nose thereof is adapted to be blown radially from the firearm through a cooperating passage responsive to excessive gas pressure in the barrel for release thereof. In an alternate embodiment the tubular body of the extractor is thinned down where coincident with the inner mouth of the passageway so as to be rupturable by excessive gas pressure for release thereof through the passageway.

Description

BACKGROUND OF THE INVENTION

This invention relates to firearms which fire cartridge type ammunition and in which the breech end of the barrel is fully obturated at the time of firing, and it pertains more particularly to a safety device whereby the gas pressure in the barrel is permitted to escape when it exceeds safe limits.

In the exploratory development of light weight alloys, such as aluminum, titanium, plastic, or other non-metallic materials, for cartirdge cases as substitutes for the traditional use of brass, because of their lighter weight and greater availability in times of war, it has been found necessary to fully obturate the breech end of the barrel because of the susceptability of aluminum cases, or the like, to occasionally rupture at firing if scratched. While this obturation removes certain hazards it creates others because with the breech of the barrel fully sealed the discharge gases have no escape path and consequently create an excessive and dangerous pressure within the barrel if the bore should be clogged. Because of this condition, it is, therefore, necessary that some means be provided in the barrel which will permit the discharge gases to escape when they exceed safe limits therein.

SUMMARY OF THE INVENTION

It is a principal object of this invention to provide in a firearm breech means for releasing excessive trapped gases.

It is another object of this invention to provide in a firearm breech a means which furnishes an exit passage from the barrel chamber area to the weapon ambience when the gas pressure within the barrel bore attains or exceeds a predetermined pressure.

It is a further object of this invention to provide an improved firearm with safety means for preventing excessive gas pressures in chambers associated with the breech end of the barrel.

It is a still further object of this invention to provide an improved safety means for firearms which is highly effective to relieve excessive gas pressures when developed in barrel chamber areas, and which is positive in performance.

These objects are achieved in this invention by providing for the extractor, which is described in applicants' copending patent application entitled "Obturator-Extractor Device for Firearms," a retaining pin the head of which is adapted to be either swaged or sheared and blown out of the barrel for release of the gas pressure therein when it exceeds a predetermined safe limit. In an alternate embodiment the tubular body of the extractor is thinned down where in registry with an escape passage from the barrel so that it will rupture through shearing action in response to excessive gas pressure in the barrel bore.

The specific nature of the invention, as well as other aspects and advantages thereof, will appear from the following description of the preferred embodiments which are illustrated in the attached drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary, longitudinally cross-sectioned view of one embodiment of a firearm in accordance with the present invention showing the bolt in locked battery position;

FIG. 2 is an enlarged perspective view of the extractor member of the embodiment shown in FIG. 1;

FIG. 3 is a longitudinal view in cross-section of the obturating washer shown in FIG. 1;

FIG. 4 is an enlarged fragmentary view taken along line 4--4 of FIG. 1; and

FIG. 5 is an enlarged fragmentary view, similar to FIG. 4, but showing an alternate extractor embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Shown in FIGS. 1-3 are those portions of a firearm comprising a receiver 10, a barrel 12 mounted to the front end of the receiver and adapted for receiving a cartridge 14 for discharge. A bolt 16 is reciprocatingly disposed in the receiver for delivering the cartridge into the barrle responsive to movement to a battery position, and includes a firing pin 17 slidably and axially disposed for reciprocation therein to discharge the cartridge. Bolt 16, conventionally, serves to block the breech end of barrel 12 during discharge of cartridge 14 and to extract fired case 18 thereof from the barrel responsive to movement out of battery position in a manner well known in the art.

Bolt 16 is provided with an extended portion or head 20 of reduced diameter and which is of truncated, conoidal configuration. A cylindrical recess 22 extends axially into the head from front surface 23 thereof. Recess 22 is adapted to receive the rear end 24 of case 18 and is large enough to contain the base end 25 of cartridge 14 to an extent forwardly of extractor groove 28 when the rear end of the case is seated therein. Recess 22 is radially enlarged inwardly from front surface 23 sufficiently to receive a cylindrical extractor 46.

Barrel 12 comprises a first chamber 30 which extends axially thereinto from the breech end thereof to an annular shoulder 31 for receiving head 20 when bolt 16 is in battery position and which includes a circumferential surface 32 that tapers inwardly and forwardly to conform to the configuration of the head when disposed therein. A second chamber 36 connects with the barrel bore and extends coaxially and forwardly from shoulder 31 for receiving cartridge 14 when bolt 16 goes into battery position. The interspace between head 20 and first chamber 30 is obturated by a washer 38 and a truncated conoidal sleeve 40. Washer 38 is normally of dished configuration in cross section, as shown in FIG. 3, such as a Belleville washer of the kind described in U. S. Pat. No. 75,970, which is held against shoulder 31 by the truncated conoidal sleeve 40 which is secured within first chamber 30 in a manner more fully explained in applicants' copending patent application identified above.

Extractor 46 comprises a tubular body 48 which is split, as shown in FIG. 2, to permit contraction to a smaller diameter thereby to facilitate insertion into recess 22. The facing ends 50 of extractor 46 are provided respectively with complementary semi-circular notches 52. Extractor 46 is secured against rotation in recess 22 by a solid pin 56 which is pressed through the aperture formed by notches 52 into a mating hole 58 provided in head 20. Pin 56 comprises a tapered head 60 which is receivable by complementary notches 52 to secure extractor 46 against rotation. The pin head has a predetermined larger diameter than that of escape hole 58, as shown in FIG. 4, whereby, when the gas pressure in barrel 12 exceeds safe limits, the pressure applied against the face of such head will force it through the hole either through swaging or shearing action for release of the gas pressure. Escape of pin 56 and the gas from barrel 12 to the outside of the firearm is permitted by a passage 62 which comprises hole 58, an orifice 64 through sleeve 40 and a port 66 through barrel 12 from first chamber 30 to the ambience. Passage 62, preferably, inclines downwardly and forwardly so that pin 56 and the escaping gas will be directed free of the operator. Relief hole 58 and orifice 64 are, of course, located so as to be aligned with port 66 when bolt 16 is in locked battery position. Suitable means is provided also for maintaining sleeve 40 oriented for alignment of orifice 64 with hole 58 and orifice 64.

Also provided on extractor 46 is a claw 44 for extracting cartridge cases from the barrel chamber. The claw is disposed chordally sufficiently to extend into the cartridge extractor groove 28 for engagement with the base end 25 of the cartridge.

The claw 44 is disposed preferably diametrically opposite the notches 52 thereby to effect a balanced structure.

The walls of sleeve 40 are arcuately curved, as shown in FIG. 1, and the washer 38 is dish shaped as shown in FIG. 3 for effecting a tight engagement with the bolt head 20, thereby providing a more positive obturation or seal for the chamber 30.

Shown in FIG. 5 is an alternate embodiment wherein extractor 46 is disposed in recess 22 so that ends 50 are located away from hole 58 and is secured against displacement relative thereto by a pin 68 pressed into a bore 69 disposed in the head 20. A section 70 of tubular body 48 is thinned down in the vicinity where it is coincident with the inner mouth of hole 58 to a predetermined thickness so as to be rupturable thereat when the gas pressure in barrel 12 exceeds safe limits to thereby release the excessive gas pressure from the barrel through passage 62.

It will become obvious to persons skilled in the art that forms other than the two embodiments shown and described herein are possible within the spirit and scope of the present invention. Therefore, it is desired that the present invention shall not be limited except insofar as it is made necessary by the prior art and by the spirit of the appended claims.

Claims

We claim:

1. In a firearm comprising a barrel having a breech end and chamber means extending inwardly therefrom including a chamber for receiving a cartridge for discharge, said cartridge including a case having an extractor groove, a bolt disposed for longitudinal reciprocation to and from a locked battery position, said bolt including a head provided with a recess extending thereinto for receiving the rear end of said case including said extractor groove, obturating means operationally disposed for sealing said breech end gas tight between said chamber means and said bolt responsive to movement thereof to the locked battery position, an extractor carried by said bolt for extracting said cartridge case from said chamber, said extractor having a tubular body receivable by said bolt recess for retention therein and a tang integral with said body and disposed for engagement with said extractor groove, and relief means associated with said bolt, said extractor, said head, and said barrel for relieving gas pressure generated by discharge of said cartridge in excess of predetermined safe limits, said relief means comprising aligned escape holes extending through said bolt head, said extractor, and said barrel from said recess to the ambience and means normally blocking said escape holes and being subject to removal in response to excessive gas pressure in said chamber thereby to open said escape holes.

2. The invention as defined in claim 1 wherein said blocking means comprises a pin having a tapered head, said pin being disposed through said extractor escape hole into said head escape hole with the tapered head thereof disposed within said extractor escape hole and being of larger diameter than said head escape hole.

3. The invention as defined in claim 1 wherein said blocking means comprises a section of said extractor body in registry with said escape holes and dimensioned to a thickness conducive to rupture in response to excessive gas pressure in said chamber thereby to provide an escape port therein.