US2399253A - Sear mechanism - Google Patents

Description

April so, 1946. D, C. REILLY 2,399,253 y l sEAR MECHANISM Filed May 25, q1944 q Dern-mt E Eellly @2M army/MMM,

@Wn/wmp Patented pr. 3G, 1946 4. Claims.

(Granted under thev act ofA March 3, 1883, asamended April; 30, 1928; 370.0.: G. '757)1 Thefinvention described-,herein,may bev manufacturedandused; by or; for the Government. for governmental-.purposes without the payment to me of any royalty thereon.

Therinyention relateslv to animproved trigger, hammer, and v searfor firearms and particularly suchasrused irl-thev U. S. rie cal. .30 M1 sometimes known as the Garand rifle, the generalrring mechanismbeing shown .in theapplication of GarandSerial No. 426036,`ledV January 8, 1942, nowPatentNo. 2,386,205, dated Oct. 9, 1945, and developed. to the designv here illustratedl subsequently.l

It, is.- an objectV of. theinvention` to eliminate what is known as. creep in trigger actions, which materially. impairs theeffectiveness of i'lre of, arms ofthegeneral kind, evenby experienced marksmen.`

In some firing: mechanisms the preliminary liring movement.- of the trigger, sometimes known as take-up, isefiectedby, moderate application of force, and beforereleaseof the hammer there is anY increased opposition to .the nal movement of' the trigger. This is necessary in military weapons to reducey liability of accidental operationlofthetriggenbut marksmen are agreed that this more resistant,movement` should be slight. Whenit extends .over a range of movement ofthe trigger` exceeding, say, .01' tjo 02 inch before the "1`et ,oi." or release of the, hammer, it becomes very noticeable, to theV user ofv the weapon and ther-movement up to some suchdesirable limit or point is,called.cre.ep., It is considered', aA major factor. responsible for inching, and poor shooting ingeneralgin the cases .of both untrained and ex.- perienced'shooters. ByA adjustment off the sear in relation to the trigger to remove this creep action, and permit operationbf theA hammer or letioi after only` afew thousandths of 'aninch movement ofthe trigger underl the greater opposition, it isl foundthat eiective fire of riflemen is improved from2 per, centjrtoil per cent, dependingn on` the individuals experienceV and nervous condition, and'other conditions attending or surrounding-thev ring-operations.,

It isgtherefore an aim of this invention to present ameans for adjusting aweaponso that the last` named manner oft functioning, may be attained, and-particularly as to the army rifle named-t'o enable thisY accomplishment without modifyingtheformor basic functions ofthe parts of` tl'le:A ring mechanism, involved, as WellK as avoiding addition of operating partsso thatv no change; in ,present production andKA assembly practceisreqllired.

A further importantaim.istopresent almeans for effecting such` adjustmentas 1 indicated which willie@v` inexpensiverandmarr be utilized byv men without expert or mechanicalgability.,

Additional obj eots,l advantages, andfeatures of invention reside linthe construction, larrangement. and combinationof parts involvedin theembodiment. of theinvention, asiwill, appear from the following description and accompanying.l drawing, wherein:

Fig, 1 isa detail eleVationofa-triggerandphammer action 4embodying-.lily invention;

Fig. Z'sanenlarged fragmentary view similar toAFig. 1, partly in section,i after the-,take-llp movementof thetrigger has beencompleted;

Fig. 3 is a similar view atthemomentnf let- 01T;

Fig. 4, isya horizontal. sectionI on, the line lli- 4 of 'Fig. 2;v

Eig. 5 isa perspectiveview ofl a trigger showing a modication.

Referring more, particularly to the drawing, there-is illustrated a familiar, trigger and hammerv action in cockediposition, the structure, and functional relationl andinteraction. of theop/era-y tive parts being well. known andunderstoodwithout` detailedy description. Theyhamrner I0 and trigger I-I.in thisdevice areidentical in their elements, proportions; andA mounting with the devices asheretofore constructed,. and a searv` l2 isA also .included identical in form, size',y location, and manner ormounting onthetrigger, and involving asimilar principle or manner of" functioning between` the, trigger and hammer, but having incorporated therewith an adjusting screw I3, engaged., from the. rear through the transverse 'IZ-.head l!! of, thet scar on an approximately horizontal'v line sov that its forward end 'willimpinge against the rear edgeV of the trigger arm I5. The trigger carries theI usual lateral' forwardly located let-off'lugs I6 at respective sides at the upper extremity. The hammer also has the forwardly and rearwardly extended hooks Il and I8A onr the lower partA of' theghammer; this part ofthe hammer being dividedy sothatparallel arms or claws I9 are formed at each side of the trigger, each claw with hooks Ilja-nd l-8 thereon. The mechanism includes the hammer spring 2i! andits housing 2l, as heretofore, andV having: the same functions.

The functioning. o f the Darts only from cocked position for firing of the armwill behereindescribed, since the other uses and functions ofthe parts are wellj understood.

The Sear head` Illl functions as inI the prior mechanism, its detent arms engaging over the rear hooks I8 of the hammer arms in the initial slight return movement of the hammer from extreme cocked position while the trigger is still held depressed and before the lugs I6 return to interposed position in the path of upward movement of the hooks I'I. The sear head I4 is of considerable vertical extent, so as to afford a forward cam face I4' extending the full width of the two arms I9 and hooks I8 of the hammer, its lower part being at a level with the rearwardly extended tips of the hooks I8, and sloping upward and rearwardly with a slight curve rearwardly so that slippage of the hooks thereon becomes easier as the hooks moveupwardly thereon, which occurs in the present device as heretofore although limited in degree according to adjustment of the screw I3, as will be explained.

The device being cocked and to be fired, the triggery finger piece 22, formed integrally at theV lower end ofthe trigger, is pulled rearwardly as usual. At the beginning of this movement the lugs I6 of the trigger will be over and engaged at their undersides by the forward hooks Il. The notch 23 in the rear end of the spring housing 2| is engaged by the tips 24 of the fingers 25 of the sear, these tips extending forwardly beyond the trigger arm and being locatedbelow the pivot Ypin 26 of the sear by which the latter is pivoted on the trigger, so that the force of the hammer spring urges the head VI4 forward. As before, the Sear has very slight pivotal movement on the trigger, due to shoulders 2'1y at each side of the trigger limiting downward and rearward movement of the sear, and because the head I4 is close to the trigger arm I5.

The housing 2I being thrust rearwardly by the hammer spring 20 against the eccentric tips 24, the sear head I4 is pressed forwardly toward the trigger arm so that the space between the head I4 and lugs I6 is less than sufficient to Yallow the hooks I1 and I8 to clear for upward movement. A sufficient pressure on the trigger finger piece 22 however, moves the trigger arm forward, bringing the head I4 finally against the hooks I8, causing the hooks I8 to press the sear head rearward against the force of the hammer spring as the lugs I slip forwardly on the front hooks I1,

until clearance of the latter is effected.

Heretofore, the head I4 has rested directly against the trigger arm I`5,`and at initial position ,of the parts this head was thus held a short distance from the rear hooks I8 so that a certain slippage or take-up movement of the lugs I6 on the hooks I'I would occur before the sear was moved into pressing engagement with the extremities of the hooks I8. This take-up movement was somewhat more than one half the total movement required to clear the lugs I6 from the hooks I'I.

I1 is somewhat more than %4 inch, involving about T36 inch movement of the trigger finger piece 22 at an intermediate part.

As the` surfaces of the lugs I6 are nearly tangent to an intersecting radius of the trigger pin 28, there is very slight resistance to movement of the trigger in the first or take-up part of thetrigger operation (practically all due to the pressure 0f the hammer spring housingr communicated to the trigger arm through the pivot 25 of the sear, veryclose to'the trigger pin 28). ,But when movement of the trigger brings the sear against the tips of the hooks I8, further movement of the trigger requires a force several times as great. This results in a further compression The total lug movement at the hookY of the tissues of the finger by which the trigger is being operated, and a complete stoppage of movement of the trigger for the time being, until the rifleman increases his efforts suiciently to continue the movement of the trigger. If this further movement continues over a few seconds (which may occur, due to the very slow movement involved when careful aim is taken), there may be a trembling of the strained muscles as well as development of other disturbing factors as heretofore noted, and others not mentioned but understood by gunnery instructors and marksmen generally.

Due to variations from standard proportions and specifications which must be allowed in the quantity production of such arms as well as other factors, a lesser proportion of take-up was heretofore allowed than desired, and in addition, some actions will have excess creep movement of extreme degree and others may have less ofv such'excess Vso that there will be great uncertainty as to theperformance of weapons compared to any uniform operation, al1 Vshort of an ideal or desired standard; and even mderate effectiveness of a shooter may be destroyed if he has to use other than the one gun he has become accustomed to, even if of the same manufacture. Y

Therefore, by the use lof my invention, it is possible to adjust all weapons to a high standard of function and uniformity as to take-up, sear, and let-off (by which is meant clearance of the hooks I'I from the lugs I6 in this instance). f V

To decrease the high pressure terminal period of operation of the trigger, the screw I3 is screwed forward toward the arm I5 of the trigger until the sear is drawn rearward such distance when the mechanism is cocked that there will beV only the desired further movement of the'lugs I6 necessary to clear the hooks I1 while the hooks I8 wipe against the sear head. A lock nut 29 may be employed to secure the screw I3 at adjusted positions, if desired or other means employed as found practicable.

In order to further simplify production and enable adjustment by filing, stoning, or grinding, if desired, I have shown in Fig.V 5 an embodiment of the invention in which all parts are made as in prior production, except 'for the formation of a small integral tit, nib or nodule 3D on the back edge face of the trigger arm. In the assembly of the trigger and hammer parts which is carried out as heretofore, the nib 30 will hold the sear spaced rearward a maximum distance when the action is cocked. This distance will be an extreme, and preferred standard function or adaptation to the personal requirement of an Vindividual is attained by filing or grinding olf a portion of the apex of the nib 3'0. In `case of wear of the let-off edges of the lug I6 and hooks I1, this maybe quickly compensated forfrom time to timeby a further reduction of the nib, which will wear less than the lugs and hooks.

In the final operation of my invention, the sear I2-I4 does not actually function as a sear (although it will have previously so functioned ,on the to-ps of the hooks I8), but operates as a spring-loaded wiper while pressing on the hooks I8 of the hammer after completion of the takeup movement, and merely opposing clearance movement of the lugs I6 which actually perform the final sear function. Consequently it is not material whether the parts of the hammer engaging the sear I2 are hooks or merely broad nonprojecting surfaces at the rear of the' hammer.

without departure from the spirit of the invention set forth in the appended claims.

I claim:

l. A hammer and trigger assembly comprising a spring-loaded hammer movable in a xed path and including a rearwardly extended arm having hook elements thereon extended in opposite directions laterally of the path of movement of said extension, a trigger spring-urged toward an initial position movable generally transversely of said vpath of the extension and having detents thereon spaced transversely of and adjacent opposite sides of said path, one of the detents being xed on the trigger and interposed before that hook of the hammer at the side of said path in the direction of iiring movement of the adjacent part of the trigger when the hammer is cocked, the other said detent being positioned and relatively movable on the trigger so as to engage the other hook of the hammer in nal ring movement of the trigger and spring-urged toward the fixed detent of the trigger` and a screw engaged through the said relatively movable detent of the trigger arranged to impinge against the trigger to oppose convergent movement of this detent toward the other one beyond a limit xed by the screw.

2. A hammer and trigger assembly comprising a spring-loaded hammer movable in a fixed path and including a rearwardly extended arm having hook elements thereon extended in opposite directions laterally of the path of movement of said extension, a trigger spring-urged toward an initial position movable generally transversely of said path of the extension and having detents thereon spaced transversely of and adjacent opposite sides of said path, one of the detents being xed on the trigger and interposed before that hook of the hammer at the side of said path in the direction of ring movement of the adjacent part of the trigger when the hammer is cocked, the other said detent being relatively movable on the trigger and spring-urged toward the xed detent of the trigger, and a screw engaged through the said relatively movable detent of the trigger arranged to impinge against the trigger to oppose convergent movement of this detent toward the other one beyond a limit xed by the screw, the said relatively movable member being advanced beside said path and formed with a cam face to wipingly engage the opposed hook element of the hammer over movement of the trigger to complete let-off, and to wipe the last named hook on cooking movement of the hammer over an extent of movement of the hammer controlled by said screw.

3. In a trigger and hammer mechanism, a spring loaded hammer, a trigger having a detent thereon and mounted for detent engagement with the hammer and arranged for take-up and let-oir action under moderate force, and a springloaded presser member on the trigger relatively movable thereon laterally of the hammer path in a direction aligned with the path of the trigger, said presser having a wiper part thereon positioned to yieldingly engage the hammer opposite the said first-named detent through movement of the presser and trigger relatively over a distance longitudinally of the trigger path, trigger carried extensible Contact means being included on the presser before the wiper to wipingly engage the hammer in advance of the wiper in initial movement of the trigger constructed and adjustably extensible and retractable at will to be varied in effective length to control the extent of wiping engagement of said presser in relation to the trigger movement, said hammer having a part so positioned as to tend to engage said wiper directly at a given part of the relative movement of the trigger, whereby the let-oif movement before release may be regulated.

4. A gun trigger, sear, and hammer device comprising a spring-loaded hammer pivoted for spring-urged upward and forward pivotal movement, said hammer having a rearward lower rst cocked position and a normal advanced cocked position, and having an initially depending claw arm at its rear part, forwardly and rearwardly projected hooks at the extremity thereof, a spring loaded trigger pivoted below said hooks having a trigger arm extended upwardly beside said claw arm, a let-oil lug at the upper end of the trigger arm positioned to engage over said 4forwardly projected hook at normal cocked position of the trigger and hammer and to clear the hook on full swing of the trigger, a sear pivoted on the trigger arm above the pivot of the trigger having a detent arm above its pivot movable forwardly and rearwardly and positioned to engage over the rear hook of the hammer claw at first cocked position of the hammer and full pressed position of the trigger, a Spring engaged with the sear to press the sear arm toward the rear hook of the hammer claw, said sear having an upper stop part movable forwardly and back in line with the trigger arm, said sear detent arm having a, face opposed to the rear hook with an extent in the direction of movement of the hook with the hammer sufficient to engage the hook slidingly DEMOT C. REILLY.

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