US2509540A - Machine gun fire retarder - Google Patents

Description

May 30, i950 o. o. SUNDERLAND 2,5@9954 MACHINE GUN FIRE RETARDER Filed Sept. 14, 1945 2 She'ets-Sheet l 48 Ej 5-5L 4 L A29 @la IZS 78 24 d v l 47 46 L 55 t; 66 36- 7/ .im 55 40 7%8 Y 3S/l i May 30, 1950 o. o. SUNDERLAND 2s59954 MACHINE GUN FIRE RETARDER Filed Sept. 14, 1945 2 Sheets-Sheet 2 Dam/ald D- luvadapan :D

.awffmgm Q/ Patented May 30, 1950 MACHINE GUN FIRE RETARDER Oswald 0. Sunderland, Fairfield, Conn.

Application September 14, 1945, Serial No. 616,333

14 Claims.

The invention relates to means for reducing the rate of lre in machine guns, particularly those of .30 and .50 caliber rearms, the object, as usual in such devices, being to enable the use of the standard high rate of fire at which the guns tend to operate with the basic or conventional action, and to permit reduction in this rate at will where the high rate would expend ammunition in a quantity out of proportion to the result accomplished. As is well known, due to the fact that such arms are advantageously usable at short ranges against aircraft, and in order to deliver projectiles at short angular intervals under rapid traverse, the gun action will ordinarily operate at a rate of from 500 to 900 rounds per minute more or less. When such a gun is used against enemy infantry, such a rate is much too fast, and is apt to result in exhausting the ammunition supply while the military unit is `'still under re. This liability is contributed to by the tendency of some personnel to freeze on the trigger.

Therefore, it is now recognized as important to provide means operable at will be the soldier to control the rate to meet conditions of the moment. In meeting the need outlined, it is an important object of this invention to present a mechanical device which will be peculiarly novel for its simplicity, compactness, and adaptability to be substituted for conventional trigger mechanism without changing conventional gun actions otherwise than to provide for the fitting of a Small trigger housing to the conventional receiver.

it is a special aim of the invention to present an escapement device which is safe from liability of access of dirt and mud or damage by moving objects as might be encountered in the rough handling of firearms in fleld service.

A further aim is to present a novel form of delay device including a novel means for effecting the functioning of an escapement device without dissipating materially the energy of recoil and counter recoil devices of the gun action. Additional objects, advantages and features of invention reside in the construction, arrangement and combination of parts involved in the embodiment of the invention and otherwise, as will be either apparent or understood from the following description and accompanying drawings, wherein:

Figure l is a fragmentary longitudinal sectional view of a trigger and delay action device in cocked position, the trigger free, with a part of a conventional action slide such as has been heretofore used in machine guns such as illustrated in the patent to Browning, Number 1,293,022, and to Simpson, Number 2,379,461, and other patents;

Figure 2 is a similar view of the trigger mechanism in retarded automatic fire, at the moment of let-olf of the sear;

Figure 3 is a fragmentary view of the trigger parts at initial automatic retarded action position of the rack and sear subject to movement by the slide to the let-olf position;

Figure 4 is a cross section on the line 4 4 of Figure 1;

Figure 5 is a detail of the escapement wheel and ratchet with a part broken away;

Figure 6 is a cross section on the line 6 6 of Figure 1; looking toward the gun butt;

Figure '7 is a section on the line 1 1 of Figure 1, and

Figure 8 is an exploded perspective view of the trigger mechanism.

Referring more in detail to the drawings, there is illustrated a portion of a receiver Ill in which is mounted the conventional action slide I I, having the usual recoil and counterrecoil functions, including in the specific instance a buifer I2 against the buffer head I3 of which the cross member or bumper I4 of the slide II engages at the rear limit of its recoil. As is usual, in these slides, the cross member I4 includes a bottom planiform plate I5 extending forwardly and having in its lower face the usual notch I6 against the claw or shoulder I1 of which, the heel I3 of a broad Sear I9 engages substantially in the same manner that the conventional sear engages in the notch in such a gun action.

In the present instance, the trigger frame or housing 2l! includes side plates 2| fitting into the receiver conventionally and a forward vertical cross plate 26) of the frame has near its upper edge a horizontal rib 2l serving as a support means, although other construction may be employed as found expedient. A bottom 22 is formed on the housing and below this at the forward part a trigger guard 23 of conventional form is positioned, abutting a hollow pistol grip 24, extending downward from the rear end of the trigger housing.

The sear in the present instance corresponds somewhat to the form of the conventional sear in prior weapons of this type, including a forwardly extending operating leg 25, this and the heel portion I8 of the sear being substantially a straight member thickened toward the heel so as to receive its pivot pin 21 therethrough and to permit the formation of a recess on its underside accommodating a compression coil spring 28 seated on a seat 3G on a lever 2s. Contrary to ordinary practice, however, the pivot of the sear 59 is not fixed in the trigger frame, but is a floating pivot pin 2l, set through the upper short arm 25 of the lever 29, the lower long arm of which extends downwardly through an opening in the bottom 22 into the hollow grip Gn the upper part of this lower arm a rearward cup seat bracket 3@ is formed oiset slightly to the left but under the heel of the sear (Fig. 7), andjreceiving therein the lower end of the scar spring 3d. 's lever 29 is pivoted on a cross pin 3l set in the walls ZI of the trigger frame, the lever being located ade jacent the right hand side of the trigger frame. Pivoted also on this pin adjacent the left side of the trigger frame and close besdevthe lever 2S there is a delay lever 52 extending downwardly below the extremity of the lever and carrying at its lower end a rack sector di? concentric with the pivot of the lever and merged with a gear 34 loosely revolvabley therebelo'w onV a cross pin 35 set between side plates et constituting a part ofthe trigger frame within the grip 2li; his rack and gear are located adjacent the left side of the grip as shown. Revolvable freely' on the pin 35, there is also an escape-ment wheel vclose beside the right side of the gear. rlhergear and escapement wheel are formed with abutting complementary ratchet or clutch and the gear @il is capable of sliding movement on the' pin 35 toward the left so as to permit it to disengage from wheel Si" cn rotation in one direction, the clutch faces having saw teeth 3S 'operative for this purpose. The gear is held yieldingly in engaged' relation to the escapement wheel by means of a compression'spring (Fig, e) accommodated in a concentric recess formed in the left side of the gear and conned-by a shoulder 4E) formed on the pin 35. it may thus be seen that upon oscillation of the lever 32 tothe left from its extreme right hand position shown in Figure' l, the gear may move esV an idler without rotating the escapement wheel (see Fig. 5), but upon opposite movement of thelever thel clutch' teeth 33 will co-engage and rotation of the'gear l will drive the esce-.pement wheel. It will be noted that the wheel 3i is of much larger diameter than -the gear and the rack 33 operates close beside the wheel 3l. The lower end of theiever 291s offset toward the left as at in Figure '7, and its extremity l-l- (Figures l, 2 closely over the forwardly extended partcf 'the rack. 33, which is formed at its forward end with an upwardly extendedlug ft2, to limit forward movement of the lever, Zlrelatively to lever and also a shoulder d3 at the base of the'Y lever 32 to limit relative rearward movement `of the lever 2S.

The two levers have seat lugs t5 projected across the medial plane of the frame and recessed 'f to receive therebetween a compression spring' d5 by which they are urged apart a distance limited by the lug 42, and yieldable momentarily to forward impact thrust of the action slide against the sear I9, as will be subsequently explained.

The upper arm 25 of the lever 25 is extended forwardly at an angle of about 60 degrees to the horizontal, and is engaged in a longtitudinal-slot formed through the sear, where it receives therethrough the pin 27, as may be seen in Figure 4. As a result, upon counterrecoil of the slide initial. engagement of the sear with the shoulder li will occur at the positions of these parts shown in Figure 3, and impact oi the slide against the sear will move the sear abruptly forwardly,

and v4) moves slightly compressing the spring momentarily with consequent slight downward movement of the sear pivot as may be understood. However, due to the angular position of the sear pivot 2l with relation to the arm 29, movement of the lever 29 is checked by the spring 4t or the lever 29 engages the shoulder 43, before the ksear has cleared the slide and the gun will not fire until the trigger is operated. Due to retardance of the lever 32 (tob'eexplained), the spring it Will recover with-partialreturnof the "lever 29 and sear, but continued pressure of the slide will move the levers 29 and 32 substantially as a unit, to the positions of Figure 1.

Rotation of the wheel 31 is retarded by means of" aipendulum-weight or escapement lever 4l rockingly mounted on a cross pin 68 in the extreme lower part of'the space in the grip 24 and havingpallets 49 shaped and set within the path of the teeth of the wheel 31 sufficiently to unction as an 'escapement A trigger -is shown, constituting aldepending:

linger piece 5I and shank'52, the latterrectangular in horizontal section and:transversely` bored` rearwardly of the end ofthe arm;5S; This cam-lsr a simple straight armextended horizontally forward atinitial position of the parts, resting uponV the arm 55 of the trigger, andsupporting slidably the extremity of the arm 26 of the'sear upon the cams ilat upper surface.` The thickness of the cam is such that-With the trigger inany po.-

sition-the arm 25 is always supportedgby. the

cam.

The cam 5l is laterally thickenedat its rear part so as to extend to the left-of thegarm 55, and is formed on its underside with twoihorizontal downwardly facing steps? cand litrespectively, the former being higher than, and forwardly ofthe latter as best shown at Figure 8. Below the cam and aligned therewith, rearwardly of the shank of thetriggenan L-shaped dog El is pivoted, on a transverse pin t2: belowr the arm 55, which also servesasa` stopfor the dog. The dog has a forwardly extending lower short arm B3 cupped and coninin'g thereunder a spring 611 againstthe bottom of the trigger frame, and an upstanding arm constituting a rest $5 of a length sulicientv to extend above the firstv step 59 a distance corresponding to the movement of the sear'arm 25 to' nrst released position as will be subsequently-explained. The' spring 64 serves to move therest 55 under the steps 59 and 6d successively as the cam 51 is pivoted clockwise as viewed in Figs. 1, 2 and 3, to successive positions, so as to support ther cam in such positions Without disturbance oil the` sear byvwavering movementsl of -the trigger within certain limits. The trigger rear-armis extended ull width for a short distance from the shank 52, so as to provide a presser lug 56 over the arm 53 of the dog, so that after operation oi the trigger to elevate the cam and permit movements of the rest (i5-as stated, on release of the finger pull on the trigger, the lug- 66- will `press upon the short arm B3 and return the rest 65 toward initial position.

The extent of ring movement of the trigger 5| is limited by means of a selector 51, which is a simple elongated rectilinear sliding block inserted through an opening 68 in the front wall 2| of the housing immediately over the bottom 22 of the housing, this block being substantially thicker and longer throughout its forward part than at its rear part, this forward part remaining in and closing the opening 68 throughout all operating positions of the selector. The rear part 59 of the selector comprises a flat horizontal, longitudinal extension of reduced height at the lower side of the body of the selector, resting upon the bottom 22 and having an upturned nib at its rear extremity. The selector is held in place by means of a small pin 1| set in the walls of the frame closely over the rear extension 69 limiting forward movement of the latter by engagement of the nib 10 with the pin and limiting the rearward movement of the selector by engaging the shoulder 12 on the latter defining the inner end of the thick forward part of the selector. The selector has two operative positions (one being shown in Figure l) and it is retained yieldingly in either of these positions by a springpressed detent 13 slidable in a shallow bore in the bottom 22, arranged to alternatively engage respective indentations 14 in the underside of the selector body. The rearmost of these indentations is positioned so as to stop the selector at a forward position with its inner extremity forwardly of the end of the arm 54 of the trigger. This arm is provided with a forwardly extending lip 15 which, at the rear position of the selector will engage upon the nib 10 and check downward movement of the trigger when the arm 56 has lifted the cam to that position where the rest 65 may engage under the first step 59 (as in Fig. 3). And when the nib 10 is pulled forwardly to its second position, the arm 54 of the trigger may move to the bottom 22 resulting in elevation of the cam sufficiently for the rest 65 to engage under the second step 60.

In operation, assuming that theweapon has been cocked by drawing the slide rearwardly to the buffer head I3 and then releasing the slide, the trigger being free, at the instant of such release the levers 29 and 32 would be in the position shown in Figure 3, but the trigger parts as in Figure 1, and the sear slightly to the right of its position in Figure 1. The usual operating spring of such weapons will then, by its stable force, move the slide and Sear forwardly, bringing the parts to the positions illustrated completely in Figure 1, the trigger meanwhile remaining without movement and without being affected, in the position shown in Figure l. It may also be assumed that the selector has been pressed inward to first, or retarded rate position, as in Figure 1. Y

Upon pulling the trigger then to the first firing position (see Figure 2) the arm 56 bears upwardly upon the cam 51 and this produces a magnified movement of the leg 26 of the sear until let-olf occurs at the instant when the rest 65 is moved by the spring 64 to position under the first step 59, and the heel I8 clears the shoulder I1. The slide is thus released, and moves forwardly to battery position, being returned by recoil or gas operation according to the type of gun involved. With the trigger maintained in or near the rst firing position, the leverage exerted through the arm 26 by the cam 51 and the force applied thereby through the spring 28 to the lugVv 36, causes the lever end 4| to press forwardly against the lug 42 of the rack, rapidly moving the latter and the lever 32 forward as a unit with the lever 29, and bringing the rack 33 to its forward position (Figure 3), thereby rotating the gear 34 counterclockwise as an idler. Upon recoil of the slide thereafter, the lever arm 25 being now at the maximum elevation of retarded lire, the heel I8 will have been lifted to a level where it will engage the shoulder l1 of the counter recoiling slide.

Incident to the acceleration which may occur after the bumper |4 is stopped by the buffer, the

c impact of the shoulder l1 against the heel of the Sear will for the moment exceed the stable expansive pressure of the conventional driving spring of the gun action, then the sear and lever 29 will be moved and the spring 46 will yield to the pressure of the lever 29 before inertia of the lever 32 (initially positioned as in Fig. 3) and escapement are overcome, permitting a slight convergent movement of the lever. But the spring y46 will immediately thereafter recover and force the lever 29 forward to its initial angular relation to the lever 32, its end 4| stopped against the shoulder 42, while the retarded movements of the rack and ratchet proceed.

The stable force of the driving spring acting through the slide will now continue to move the sear forwardly, swinging the arm 25 forward and the lever 29 rearwardly so that the spring 4B moves the lever 32. This will rotate the escapement wheel 31 clockwise, this motion is impeded by the escapement to a degree determined by the weight of the pendulum and depth of engagement of the pallets thereof with the teeth of the wheel. After the desired extent of movement of the wheel 31 and time lapse required, swinging of the arm 25 and sliding of the scar arm 26 upward on the cam 51 lowers the heel i8 of the sear to a level where let-off will again occur (the trigger being maintained in sufficiently finger-pressed or pulled condition) and the foregoing action will then be repeated as long as the trigger is held to or near its rst let-olf position. The engagement of the rest 65 before the step 5s will prevent lowering of the cam 51 and operating leg 26 until the trigger is fully released, so that if partial return movement of the trigger occurs no premature engagement of the sear with the slide will be caused after initial let-oli.

The spring 4S is of sufficient strength to oppose depression by the stable force of the slide when stopped at initial position so that the levers 29 and 32 normally remain fixed in the relation shown in Figure 1. But in automatic fire on counterrecoil of the slide from the buffer, the component of inertia of momentum acquired by slight acceleration of the slide, which must be additionally overcome when the sear engages the shoulder I1, results in a momentary slight movement of the lever 29 relative to the lever 32, attended by slight compression of the spring 46. The latter quickly recovers, while the sear is still engaged with the slide. If the gun is in course of automatic iire, the rack 33 will first be at a forward position and the arm 25 at a high rearward position, requiring a substantial forward movement of the sear before sliding of the toe of the leg 2S forward and upward on the cam 51- and the forward swing of the arm 25-ei`fect the necessary lowering of the heel of the sear to clear the slide. As soon as let-01T occurs with the trigger depressed, the leverage of the leg 25 7 against the cam 51 and force thereby transmitted through the spring 28, to the lever 29 and-so to the lever 32, again Swings the rack- 33 quickly forward, the force of the vspring 28 `maintaining this leverage throughout all positions ofthe parts, including released position of the trigger. In consequence, the rack 33 is Yalways maintained in its forward position when the searis noteng-aged by the slide, ready for its delay `function With the gear and escapement whenever the sear becomes engaged bythe slide.

It will be seen that let-off of movement of the sea'r is a resultant both of the lowering of its pivot with relation to theframe and rising of the arm 2S in sliding up the top face of the cam A5l While the trigger is pressed to the firsti'firing position (represented by engagement oi lip with the nib lll). It is contemplated that the cornponentof motion produced by arm operating translatively on the cam vwill supply vapproximately half of the necessary resultant, so that an ample margin for trigger movement will benallowed.

The arrangement has the advantage that a large bearing between the sear heel and slide shoulder l? is obtained on initial impact, but

much less and only slight trigger movement from beginning of take up to let-oi required.

When the selector is pulled entirely forward (a position not illustrated) the lip le may move to the bottom'E. The greater extent of movement of the trigger permitted thereby causes the trigger larm to elevate the cam andthe arm 26 of the sear to such extreme that the heel of the Sear is held clear of the slide .and

unretarded, operates in its conventional way and s,

at its maximum high rate. The second vstep G would at the same time be-engaged by the rest 65, which then functions lto prevent 'partial release of the seal1 until the trigger is released sufliciently to move the rest G5 to its ffirs't.

firing position (as in Figs. 3 and l2). In the extreme position the action will be stabilized at unretarded .automatic operation, and when the release movement indicated occurs the action will become stabilized at retarded automatic fire by engagement of the support under the step 59. At any time that the trigger is` partially released to such extent that the pawl mayfdrop to position with the nrst step 59 engaged on the rest 65 the gun will resume retarded automatic action as nrst described, At any time that the trigger is completely released the sear willengage and stop action of the gun in the manner rst described in reference thereto.

It is an advantage of the arrangement and function of the selector that accidental shifting thereof by engagement thereof against external objects can only result in moving it fromhigh rate to retarded rate position and small likelihood exists that it can `be accidentally Vmoved from low rate to high rate position. Y

It will be understood that in the claims"s1ide or reciprocate will include'pivoted members and/oroscillating movements `and devices, such Vas a pivoted hammer.

I have disclosed the invention with particularity in the best form in which I have yet constructed it, but it will be understood that this is purely exemplary, andv that modification and changes in construction and arrangement, substiti-ition* of materials and equivalents mechanical or otherwise may be made without departing from the spirit of theinvention set forth in the appended claims, wherein I claim:

:1. In a ring mechanism, a reciprocating firing'member, a sear pivoted thereadjacent having la heel movable and spring-urged into the path of the firing member and having a forwardly extended operating arm, a cam having a cam face under said arm, means responsive to operation of the firing member .to Ymovegthe cam and sear divergenti;7 and then convergently 'with the cam oblique tothe path of their relative movement for let-off of the seal, means to `retard. said convergent movement, and 'trigger means to move said cam whereby let-ofi of the sear will occur by at least a terminal part of said convergent movement. Y

2. In a firing mechanism, a reciprocating ring member, a sear pivoted thereadjacent having a heelV movable and spring-urged into the path of the firing member and havingA a forwardly extended operating arm, a cam having a cam face under said arm, means responsive to operation of the l'iring member to move the cam and sear divergently and then convergent/ly with the' cam oblique to the path of their relative movement for .let-off of the Sear, means to retard said convergent movement, said cambeing normally operative over a limited initial part oi' total said convergent movement of the sear and cam, and trigger means to move said cam to aposition of greater altitude for let-off at least.

3. A retarded actionsear device for machine guns having reciprocating action members, comprising a frame, a lever pivoted to swing in a plane with the path of the action member from an rinitial position to an operated position and having a short arm extended toward said path and inclined in the direction of its said-swing, asear pivoted on the said arm having a heel part Vmoval'ile into said path and having la forwardly extended operating arm, a second lever pivoted with the first lever, a sear spring under tension between the. sear `and sai-d 'first lever urging the sear heel toward said path, .the second lever having' a rack sector at its outer part, a revolvably mounted gear meshed with the rack an escapement operat'ivelyY associated with the gear to retard movement of the latter in one direction, a resilient connection between the levers, a cam positioned to slidingly support the end of said operating arm of the sear, and means to move said cam to vary its angular position at will in relation to the direction of movement of said short arm.

p4. rhe structure of claim 3, in which saiddevice includes airame adapted to constitute part of a gun frame assembly and having a trigger guard and hollow pistol type grip extended downwardly therefrom, said levers being extended into said grip for the described movementJ therein, said nie-ans to move said cam comprising a lever pivoted above the guard and having a rearwardly extended arm under said cam andV having a iinger piece extended intothe guard spring-urged to a forward vreleased position.

5. rhe structure of claimV 3 in which said device includes a frame adapted to constitute part or a gun frame assembly and having a trigger guard and hollow pistol type grip extended downwardly therefrom, said levers being extended into said grip for the described movementtherein,V

said means toy move said cam comprising a lever pivoted above the guard and having a rearwardly extended arm under said cam and having a nger piece extended into the guard spring-urged to forward released position, said escapement comprising a V-toothed wheel, a pendulum pivoted therebelow in the grip and having pallet portions engaging the wheel, and a one way clutch connection between the gear and wheel.

6. In a rate of iire retarding mechanism for a rapid-fire gun, a firing member movable between cocked and iiring positions, a sear, means mounting said sear in position to releasably engage and hold said member in cocked position, said means being movable between first and second positions in which said sear is at lesser and greater distances, respectively, from said member, means yieldingly resisting movement of said sear mounting means from iirst to second positions, a trigger movable in a ring direction to iirst and second :positions in sequence, cam means operable by and in response to movement of said. trigger to the first of said sequential positions to move said sear so that said sear is released from said member in response to movement of said sear mounting means to second position and movable stop means effective in one position to limit movement of said trigger to its iirst said sequential position, said stop means, when moved to another position, permitting movement of said trigger to its second sequential position wherein said sear is held clear of said firing member for all positions of said sear mounting means.

7. The structure of claim 6l wherein the mounting means for the sear comprises a irst lever with a Sear-carrying arm having an initial elevated position inclined from its pivot toward and in the direction of the iring motion of said iiring member, a separate second lever pivoted for movement in the same direction as the first, a spring connected between the sear and first lever, means limiting relative movement of the levers under urging of said spring, yieldable means engaged between the levers to limit opposite movement of the levers by pressure of the firing member on the sear, means to retard movement of the second lever under pressure of the iiring member on the sear, said sear having a forwardly eX- tended operating arm, a sear operating means connected between the trigger and sear said lastnamed means being operative to let off the sear at a forward position only of the sear on said iirst-named lever arm and firing position of the trigger, said spring between the sear and rst lever being operative to move said levers to initial positions while the sear is free of the firing member.

8. The structure of claim 6 wherein the searmounting means comprises a pivoted lever arm having an initial elevated position inclined from its pivot in the direction of iiring motion of said iiring member, said sear being a lever of the rst order pivoted on and adjacent the extremity of said lever arm and having a heel extension to engage and hold the ring member in cocked position, yielding means urging said lever arm to said initial position and yieldable to pressure of the iring member on the heel of the sear, said yielding means comprising escaipement means connected with said lever arm to oppose movement of the latter by the firing member and yieldable freely to return movement of the lever arm, said sear having an operating arm extended in the direction of ring movement of the firing member, said cam means extended from near the pivot of the sear in said direction of ring movement between the sear and trigger and receiving said operating arm slidably thereon, said trigger being operable to engage and vary the pivotal position oi said cam means. Y

9. In a rate-oi-fire-retarding mechanism for a rapid-fire gun, a firing member mounted for reciprocation in a rectilinear path between cocked and firing positions, a cam element adjacent said firing member and having a cam surface (pivotable from a rst position generally parallel with said path to a second position inclined toward said path, a trigger operable to move said cam element from first to second position, a first lever `pivoted about an axis generally perpendicular to said path, a sear pivoted on one end of said lever between said member and element and having one end engaging said cam element to be pivoted thereby, the other end of said sear being releasably engageable with said member to hold the same in cocked position, said sear being pivoted to release said member, only when said cam element is in said second position, by and in response to pivotal movement of said lever to predetermined position, and time-delay means acting on said vlever to retard movement thereof to said position.

10. A mechanism as recited in claim 9, said cam element being pivotable by said trigger to a third position in which said sear is pivoted to a position rfree of said iiring member, for all positions of said lever, and adjustable stop means cooperating, in one position of adjustment, with said trigger to limit movement of said cam element by said trigger, to the second position only of said element, said stop means, in a second position of adjustment being free of said trigger.

11. The mechanism recited in claim 9, said time-delay means comprising a second lever pivoted coaxially with said rst lever and movable therewith to said predetermined lposition, spring means urging said levers apart, stop means limiting the angular separation of said levers under the urge of said spring means, and escapement means acting upon said second lever to delay the movement of said levers as a unit to said predetermined position.

12. In a ring mechanism, a reciprocating ring member, a sear pivoted thereadjacent having a heel movable and spring-urged into the path of the firing member and having a forwardly extended operating arm, a cam having a cam face under said arm, means responsive to operation of the firing member to move the cam and sear divergently, and then convergently with the cam oblique to the ipath of their relative movement for let-off, means to retard said convergent movement, said cam being a member pivoted below said sear arm and receiving the end of the latter slidably thereon, a spring-loaded trigger pivoted below and yforwardly of said cam, said trigger having a finger piece for its operation and having an arm extending rearwardly under said cam for the purpose described.

13. In a firing mechanism, a reciprocating firing member, a sear pivoted thereadjacent having a heel movable and spring-urged into the path of the firing member and having a forwardly extended operating arm, a cam having a cam face under said arm, means responsive to operation of the ring member to move the cam and sear divergently, and then convergently with the cam oblique to the path of their relative movement for let-off, means to retard said convergent movement, said cam being a member pivoted below said sear arm and receiving the end of the latter slidably thereon, a spring loaded trigger pivoted 1.1 Y ybelow and forwardly of said cam, said trigger yhavinga finger piece for its operation and having an arm extended rearwardly under said cam for the purpose described.; said cam having at least `one step fpart thereunder, n dog -pivoted adjacent saidtrigger 4,arm having -a spring supported 'arm under the trigger arm and Ihaving an upstanding .rest swingable therewith under said step under fning movement othe trigger.

14. YIn a firing mechanism, a reciprocating firing member, va sear pivoted thereadjacent -having faheel `movable and spring-urged in-to the path of the firing :member and lleaving a forwardly Vextended olperating arm, la cam having a .ca-m iface -under .said arm, lmeans responsive to operation v.of the ring member to :move the earn and sear divergently., and Athen e'onvergently with the cam loblique to the path vof their relative vmovement ifor let-olf, means to retard sai'd `convergent movement, said :cam being a member pivoted below said sear arm and receiving the end of the lat-ter slidably thereon, a spring loaded trigger pivoted below and forwardly of said `cam, said trigger having a finger piece for itsoperation Vand having an arm extended rearwardly under saidcam for the purpose described, said cam having at least two -step parts at different levelsl thereunder, a

12 dog pivoted adjacent said trigger arm having la spring supported arm under the trigger arm and 'having an upstanding rest swingable therewith .under :respective extents of said Astep firing movementi/of :the trigger, said trigger and cam :having movement tor an'extreme position to clear the 'sear from said ring member throughout operation of Ithe firing memben-said sear vhaving operative relation to :the ring member only at an intermediate lposition of the trigger and cam, and means operable at will to limit firing position of the trigger.

' OSWALD YO. SUNDERLAND.

REFERENCES CITED The `'following references are of record in the fof this patent:

' UNITED STATES PATENTS Number Name Date Y 1,511,262 Browning Oct. 1-4, 1924 v23845832 Y `(.`=r11iga1 i l Sept. 18, 1945 2,384,854 lSimpson Sept. 18, 1945 FOREIGN PATENTS Nuniber Country Date France Mar. 31, 1931

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