US2981154A - Safety interlock for machine gun barrel - Google Patents

Description

April 25, 1961 P. E. SWEENEY SAFETY INTERLOCK FOR MACHINE GUN BARREL 2 Sheets-Sheet l Filed Jan. 7, 1960 PATRICK E. SWEENEY IN V EN TOR.

ATTORNEX April 25, 1961 P. E. s wEENEY 2,981,154

SAFETY INTERLOCK FOR MACHINE GUN BARREL Filed Jan. 7, 1960 2 Sheets-Sheet 2 PATRICK E.SWEENEY v INVENTOR.

ATTRNEK i nted States SAFETY rNrERLoCK Fon MAcrnNE GUN BARREL Patrick E. Sweeney, Baltimore County, Md., assignor to Aircraft Armaments, Inc., Cockeysville, Md., a corporation of Maryland Fired Jam?, 1960, ser. No. 1,066

s claims. (ci. s914) This invention relates in general to automatic machine guns, and more particularly to a safety interlock for perl mitting the barrel ofV a` machinev gun to be quickly lbarrel can be removed for replacement after a certain period of use. One of the problems associated with quickly changing the barrel is that of insuring proper head space or distance between thel shoulder in the cartridge chamber of the barreland the bolt block face when the lat-v ter is in firing position. Generallythebarr,el is threaded into the barrel extensionfrequiring gaging of the axial p position of the barrel in order to insureproper head space before the barrel is locked in position..l A failure to,pro-` videy adequate headspace can result in jamming of the gun, while head space Vin excess of thatv which is proper can result in rupture of al cartridge on firing.l Thus, when a barrel is changed, it is essential that time be taken to gage the new barrel toinsure the proper amount of head space.

, v It is therefore an object of this invention to provide a Y connection between barrel and barrelextension which requires merely the axial insertion and rotation ofthe barrely inthe barrel extension to insure proper locking of the barrel to the extension and creation of the proper head space.

of is achieved, interengaging lugs lon the barrel andbarextension to a fixed depth and rotation of the bairel until ja spring-loaded detent snaps into place` andV holdsv the barrel at a particularangular position at which the lugs on'the barrelV and barrelextension cooperate'to prevent,

withdrawal of the barrel. Thelhead space is automatically xed .and all that is necessary tobe done isto insert and rotate thebarrel through. afsuflicient angle after in.-

in haste to change barrels, the` new` barrelV is notrotated sutliciently for the detent to be eiective! rThis result is Vacxorriplished,by providing a safety lever on the barrel extension which normally is positioned in the path of the As a feature of this invention whereby the object'ther'ef ICC . tailed description thereof that follows may be better understood, and in order that the contribution'to the art` may bebetter appreciated. There are, of course, addin tional features of the invention that will be described VVrelyextension permit insertionof'the barrel into the barrel hereinafter' and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims toy be granted herein shall be of sufficient breadth to prevent the appropriation of this invention by those skilled inthe art. p -Y In the drawings: l

Figure l is a top sectionalvviewv taken along theV line 1-1 of FigureZ and showing a machine gun with the barrel properly. locked into the barrel extension and the bolt assembly in position for `firing a cartridge in the chamber of the barrel. 5 t

Figure 2 is a side sectional View ofthe machine gun shown in Figure l. f

Figure 3 is a top sectional view similarto Figure l but showing the barrel improperly attached to the kbarrel extension'and the bolt assembly held back from itsring position. f n f Figure 4 is a side sectional view of the machine gun shown in'Figure 3.

Figure 5 is a sectional view taken along the `line 5-5 ofFigure 1 andshowing the safety lever. in an inoperative position.

lFigure 6 is a sectional view taken along the line6-6 of Figure 3 and is similar to Figurey 5 except that parts Vare broken away to show, thek safety lever inoperative position.

Figure 7 is a perspective vView of the forward end of the barrel extension showing the lockinglugs thereon.

Figure V8. is a perspective View of the rear end of the barrel showing the locking lugs thereon and the cam surface for moving the safety lever.

Referring now to iFigure l, reference numeral iii designates an automatic machine gun having a receiver 1,1 with aV forward portion 12, a rearward portion i3, and'intermediate portion 1'4. Portion 13 is formed with longitudinally extending guide rails l5, and portion 12 is formed-with bearing surfacel and apertures 17. Portion 14 is provided with grooves 18 for the reception of accelerator housing '19 upon which accelerator Ztl is pivotably mounted at 21,- Acceleratorztl is biased by springs (not shown) toward wall 22 on receiver 11.

Slideably mounted within portion 13 of receiver 111 is barrel extension 23 which hasbearing grooves 2 4 on v each side' (see Figure 7*)` engaged' with rails 15. Bari sertiorria` Because of thesimplicityofthey above des :rilj edA connection, it is desirable 'to-prevent Ifiring of the gunpi'f, v

bolt assembly carryingv the tiring pin and prevents the firing pin-from contacting andiiring acartridge inthe chamber yof the barrel; "The'barrel is provided with Va camavhi'chis engageable withthe lever upon rotation of thebarrelsuchthat' its rotation to the angular position ywhere the ydetent* elfective earns'thev safety levervout of' the-path'of the bolt-assembly. lnjth'is manner, aV cartridge inthe; chamber canbe'iired only` afterthebarrel is prop.-

l erly'hattachedi'to Athe barrel''extensrio'n.v y Y lTli e important yffeatu'res 'olfrthisf invention lhave 'K @been outlined 'rather gin order ythat `the l'def t i j y rel extension 23 has a forward portion 25 (i,e., the portion to which the barrel is attached) which Yextends across the widthofportionlS of receiver 11, andrearwardly l, directed legs 26 on each side. LegsA Zoyhave ,groovesrll on their outer faces. The inner vfaces of legsf26 contain entire length bolt `assembly lgrooves 27 which extend the ofthe barrel extension. v Y

Bolt assembly 3@ has two main parts: bolt slideval, and bolt block 32,. Bolt slide '31 has flanges 3,3 slideably 'engaged in grooves `27. Beneathilanges 33 is tubular portion 34 having laperture 35 incylindrfical spring well 36 through which bolt return spring rod 37 passes.

Bolt return spring fhaskone yend lenga'ged against" thel Irear of'receiver 11 (not shown)l and one-end engaged in weil 36 for cn'stamly ingingtit fassembiy :ss-forwardly toward-wallf2.2v of receiverfll, Y1Ab`c ve ange 33V y is ytiring pin holder '39W`hic'h` is provided vwith. a longitu f Y dinaly slot 40, in which'slidejtl Vof,bolt' 'block132 isj'en- 'gageableJ-Slide 41 fispro'vided with elongatedhole 42 f through whichpas'sesffpin 43 attached'to holder '39. In

A 3 this manner, bolt block 32 is connected to bolt slide 31 for limited relative movement. Rigidly attached to holder 39 is firing pin 44 which extends through aperture 45 in bolt block 32 and can project therefrom as seen in Figure l. Pivotally mounted on each side of bolt block 32 are locking latches 46 which are engageable in keeper notches 47 formed in the inner face of legs 26 of barrel extension 23 when the bolt block is at its forwardrnost position on the barrel extension. I

Bolt block 32 has extractor cam 48 pivotally mounted below aperture 45 and biased upwardly toward the aperture. Cam `48 is engageable 4with the rim of a cartridge for extracting the same fromjthe chamber of the barrel when the bolt block is moved rearwardly by bolt slide 31. Cam 48 has ears (not shown) which are engageable with extractor grooves 49 on the inner faces of legs 26 to controlmovement of the cam relative to the rest of the bolt block when the bolt block moves relative to the barrel extension. Above aperture `45 is stripper cam 50 which engages the base of afresh cartridge above and behind portion 25 of the barrel extension during forward movement of bolt assembly 30 underthe effect of return spring 38.

Pivotally mounted on receiver 11 is detent lever `51 having arm 52 extending through slot 53 in receiver 11. Lever 51 has aperture 54 in which pin 56 can slide transversely, rotation of pin 56 being prevented. Pin 56 has j a portion which is circular (Figure 4) vand a portion which has ears thereon (Figure 2). `When pin 56 is in the position shown in Figure l, lever 51 is locked against rotation because the ears on the pin engage corresponding v The chambered end of barrel 60 has a portion 64Y of reduced diameter that is connected to an intermediate portion at shoulder 66. Forward of intermediate portion 65 is bearing ring 67 of the same diameter as bearing `16 in receiver 11. Bearing ring 67 has `axial recesses 68 which serve to lighten the barrel and prevent` distortion of the barrel due to the heat `generated when the gun is continuously fired. Axial slot 69 is formedv in the surface of portion 65. Bolt locking lugs 70 and 71 are formed on the free Vend 72 ofthe barrel adjacent chamber 6 2. Lugs 70 and 71 are located 90 on each side of the location of slot 69 and are thus 180 apart as shown best in Figure 8. Lug 70 hasradial end -faces 72 and lug 71 has radial end Ifaces 73 to deiinerlugs which extend circumferentially through `approximately one quadrant on opdirection of lgroove 69 has semicircular recessV 74 therein.

Projecting beyond the planeof the rear face 75 of thebar-v 23 with recess 80. Recess 81 is of a diameteri su'iciently large to permit rotation therein `of freejend` 72 `of the barrel. Extending Vradially/into 4recess Sjltare barrel `extension locking lugs 83.and `84, whichifornilfcontinuations `ofvface 82.flugs83 fand 84.are`.oppositely spaced-180 apart and 'larerabout oneV quadrant inglength;` The clearance `between the crests. ofglugsr 33 yanlf84 isV `substantially equal to the diameter'of portion64' on the Vbarrel.` f Mounted to one side of the center line of barrel ex- 4 l tension 23 is stop pin 85 which projects radially into aperture 81. Pin 85 is located axially inwardly of face 82 asuiiicient distance so that it engages recess 74 in lug 71 on the barrel. Barrel extension 23 has a vertical hole 86 which extends from the top of the barrel extension downwardly into recess and aperture 81. The forwardmost edge of hole 86 is rearward of pin 85 such that it is substantially -aligned with face 75 of the barrel when shoulder 66 of the barrel abuts face 82 of the barrel extension (see Figures 2 and 4). Safety lever 87 is pivotally mounted in hole 86 on pin 88 that is connected to the barrel extension. Torsion spring 89 coiled around pin 88 has one end attached to the lever and the other end (not shown) bearing on an edge of hole 86. Spring 89 is mounted so that lever 87 is continuously urged to a position shown in Figure 6 where end portion 90 projects into the path of bolt block 32. AThe projection of the bolt block is shown by the phantom lines in Figures S and 6. Hole 86 is large enough so that lever 87 can pivot against the action of spring 89 out of the path of bolt block 32 as shown in Figure 5.

The attachment of barrel 60 to barrel extension `23 will now be described.- Barrel 60 is slidably and rotatably mountable in receiver 11 because of bearing ring67 and bearing 16. Barrel 60 has another bearing forward of ring 67 that also engages a bearing on the forward end of the receiver, but these bearings are not shown. Pin 56 is moved in aperture 54 in lever S1 such that the latter may manually be moved against spring pressure to the position shown in Figure 4. While the lever is depressed, barrel 60 isinserted into barrel extension 23 by being 'moved axially (to the left as viewed in Figure 4) with lugs 70 and `71 positioned `90" out of alignment with lugs 83 and 84. In this manner, the free `end portion 64 of the barrel can be inserted into aperture 81 until shoulder 66 on the barrel abuts` -face 82 on the barrel extension, and lever 51 is heldin theposition shown in Figure 4 by portion 65 of the barrel. Because the lugs on the barrel are now interior `to the lugs on the barrel extension (see Figure 3), the barrel` can now be rotated 90.u until groove 69 opens upwardly. The position of the barrel is 'as shown in Figures 1.and 2 and lever 51 snaps into groove 69. Inaddition, stop pin enters notch 74 in lug 71 and prevents further` rotation of the barrel ,beyond the point where the lugs on the barrel are directly behind the lugs on the barrel extension.` In this position, barrel d 60 cannot be withdrawnfrom the barrel extension. As

j d tween shoulder 63 in thecharnber (Figure 2) and the fory posite sides` of portion 64. The one 4face 73 facing in the i rearward of `the'position fshown in Figure 1. 6U

ward face of bolt block 32,` when the latter is positioned with latches `46 engagedV in keepers 47, defines the head space. Thus, `by simply inserting and rotating the barrel, the proper head space is achieved.

" Assume now thatthe barrel'is properly attached to thebarrel extension and thattheV bolt assembly 30gis d Stripper carne 50 on bolt slide 31 engages the base of a cartridge as `thehbolt-slide..is drivenforward byreturn spring 38. Thecartridge is cammed downwardly by achambering ramp on receiver 11 untilextractor cam 48 is engaged in the extractor groove injthe cartridge and the bolt block engages the base of the cartridge. Further .forward v movementlof the bolt assembly causes the cartridge to be inserted into chamber 62 by the action of bolt block 32. During `this forward movement, the bolt slide and `boltblock are positionedrelative to Aeach other as shown best in Figure 3. If safety lever 87 isA in its inoperative positionybolt block 32 drives thecartridge into the charnp Y ber untilit seats against `shguider 63. l Forward movev rnent'of` block 32 ceases as bolt slide` 31 continuesrfor- Ward.movement,simnltaneouslylcamminglatches 461i`nto` j l keepers 47; and causing ring pin 44 to move through the bolt block to strike and fire Vthe cartridge. The bolt assembly is now locked tothe barrel assembly and both recoil together. Recoil of the barrel causes ring 67 to impart pivotal movement to accelerator 2.0 against its spring. However, the curvature of the accelerator is chosen so that during initial recoil, the portion ofthe accelerator contacting well 36 on the boltslide moves axially through the same displacement as the barrel. This prevents any relative movement between the bolt assembly and the barrel extension during initial recoil and permits reduction in the gas pressure in the barrel before the cartridge is extracted. As the barrel recoils further, accelerator 20 causes relative movement between bolt slide 31 and the barrel extension storing energy in spring 38. Simultaneously, firing pin holder 3 9 is withdrawn from its camming position between latches 46 as pin 43 moves in slot 42 in bolt block 32. Further `movement of bolt slide 31 relative to the barrel extension first causes keepers 47 to cam latches 46 inwardly `toward the ring pin and then causes rearward movethat the barrel is improperly attached to the barrel exable means for preventing rotationr of said barrel Aaway from said other angular position.

3. The combination with a gun barrel having a chamber at one end, a barrel extension having anaperture therein for receiving said'A one end of the barrel, and a bolt assembly slideably mounted on said barrel extension for firing a cartridge in the barrel chambervwhen the bolt assembly moves to a certain location on the barrel extensionyof a safety interlock for attaching the barrel to the barrel .extension comprising a movable safety lever mounted of said barrel extension, saidsafety lever having anoperative position in the path of said bolt assembly movement of they same to vrsaid certain location and preventingthe tiring of a cartridge in the barrel chamber, said safety lever having an inoperative position out of the path of said bolt assembly for effect-y ing movement of said bolt assembly to said certain location and the firing of a cartridge in the barrel chamber, means constantly urging said safety lever to said operative position, locking lugs projecting from said one end of said barrel, latching lugs on said barrel extension projecting into the aperture, said lugs being cooperable for tension and that portion 90 of lever 87 projects into theV path of bolt block 32. Spring 38 drives the bolt assembly forwardly causing a fresh cartridge to enter chamber 62. Forward movement ceases when the bolt block strikes the safety lever. However, bolt slide 3'1 cant not move relative to the bolt block as shown in Figures 3 and 4 because latches 46 are not aligned with keepers 47. As a result, iiring pin 44 cannot strike and tire the cartridge, and the gun cannot function.

It lcan now be appreciated that with this invention an extremely simple connection between a barrel and barrel extension is achieved while at the same time insuring against accidental ring if the barrel is improperly con-l nected. l

What is claimed is:

l. In a machine gun havinga gun barrel connected to one end of a barrel extension slideably mounted kin a receiver so that the chamber of the barrel' is adjacent said`v one end, a bolt assembly mounted von said barrel Y extensionfor reciprocatory movement thereon from onev terminal position adjacent said one end of the barrel extension to another `terminal position remote from said one end, said bolt assembly having a tiring pin" thereon for contacting and firing a cartridge in 'the chamber when the bolt assembly moves to said one terminal position; a safety interlock for attaching the barrel tothe barrel extension comprising: means to effect insertion` of said barrel intosaid barrel extension only at a given angular position of the barrel relative to the barrelextension, means to eiect rotation of said barrel after insertion vand prevent its' withdrawal from the barrel extension, stop means to limit rotation of the barrel so preventing insertion of said one end of said barrel into barrel, said cam means being engageable with said safety lever only when said barrel is rotated toward said stop means, rotation of said barrel against said stop means causing said cam means to move said safety lever froml j operative to inoperative position.

4. In combination: a generally cylindrical gun barrel y having an .axial chamber atone end, said chamber adapt'- ed to receive a cartridge, said one end having radial extending lug means; a barrel extension Vhaving an-axial aperture at one end sufliciently large to receivel said lug means, Vsaid barrel 'extension having lugV means extending radially into the aperture, the lug means on said barrel extension and barrel being cooperable to -eiect axial insertion of said end vinto said aperture when said barrel has a first angular positionrelative to the barrel exten'-v sion, said lug means being cooperable after said end is *I inserted in said barrel to yelfect'rotation of said barrel away fromsaid first angular position and `to prevent its axial withdrawal, stop means on said barrelA extension to Y.

` limit rotation of the barrel to `a second'angular position, l

a bolt assembly slideably mountedon said barrel exten` v sion for movement to'an operative position adjacent said y one' end thereon, fsaid bolt assembly having a tiring pin j thereon for contacting and firing lacartridge, inthe chamber when said bolt'assembly isf-in its operative position,

` a safety lever mounted on saidbarrel extension for rnove-l l ment from an operative position to an inoperative posi-V tion, the operative position of said lever being in the path ofthe bolt assembly` for preventing movement of said bolt assembly to its operative position, the inoperative vposition of said'lever being out of the path of the bolt that after its insertion and rotation the barrel has anv.

other angular position different from said given angular v"position, movable means on said barrel extension posi-l tioned in the pathof said bolt assembly for preventing r movement-of the latter to said one terminal tposition,

and means on said .barrel for cammin'g Asaid movable means out lof thepath of said bolt assembly uponrota'- assembly vfor Veectingv movement of. said bolt assembly to its operative position, spring meansconstantly urging said lever to its operativeposition, and cam means being `fengageable with said levei-upon rotation of said vbarrel ytion of'said barrel to the limit determined 'by said stop i "means 'j Y .7. 2. In the machine gun of claim 1*,sele`ct1vely opertowardsaid second angular position for moving saidlever against v the Iaction of p Saidspring means, movementA Vof said barrel-Pto saidy second angular position causing movement of said lever to inoperative position.

5.l In a machine gun having a receiver, a member slideably mounted in said receiver, a bolt assembly slideably mounted'on 'said member for reciprocatory movement tl- 'ward and away from a terminal position,- a tiring pin on said. bolt assembly, saidvflringipin being effective when `tl1e bolt assembly ,is atits terminal position, and a barrel having a chamber in one end for receiving a cartridge, said barrel being slideably and rotatably mounted in said receiver; means for connecting they barrel to the barrel preventing withdrawal of the barrel, detcnt means fory retainingsaid barrel at said angnlar position, safety lever means mounted `on said` barrel extension for movement from an operative position to an inoperative position, the

operative position of the lever ,preventing ,the bolt assemb1y``fr`om moving to itsterminal positionI and the firing pin r'from `being effectiveto fire a cartridge in the chamber, theinoperative` position of the lever :effecting movement of `the-'bolt assembly to its` terminal position and firing` of arcartridge in the chamber by the firing pin, means constantly yurging said lever to operative position, and cam means `on said barrel engageable with said lever upon rotation of the barrel, 'said cam means being etective -to move said lever to inoperative position only after said detent means is eiective to retain said barrel at said angular position.

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