US2796906A - Threaded locking device and method of making same - Google Patents

Description

, June 25, 1957 T. J. BUcKLEY 2,796,906

THREADED LOCKING DEVICE AND METHOD V./OF MAKING SAME Filed Feb. 18. 1954 z sheets-snee*v 1 lNvEN-roR IMoT HY J. Bucmiv Y ,Mu/kw HIS ATTORNEYS.

June 25, 1957 T. J. BUCKLEY 2,796,906

IHREADED LOCKING DEVICE AMD METHOD oF MAKING SAME Filed Feb. 18, 1954 2 snee'ts-snee: 2

INVENTOR TIMOTHY J. BUCKLEY Hls ATroRNYs.

THREADED LOCKING DEVICE AND METHOD OF MAKING SAME Y'llirnothy J. Buckley, Elmira Heights, N. Y., assignor to The Nylok Corporation, New York, N. Y., a corporation of Delaware This invention relatesto methods and apparatus for manufacturing lock nuts, lock screws, bolts and the like and it relatesparticularly to methods and apparatus for punching and vinserting plugs formed of nylon and other similar resilient plastics in lock screws, lock nuts and the like of the kind shown in thevBoots U. S. Patents, No. 2,462,603, dated February 22, 1949, and No. 2,539,887, dated January 30, 1951.

In the manufacture of lock nuts and lock screws, lock bolts and the like, referred to hereinafter-as threaded elements, extruded cylindrical rods formed of resilient plastics, such as nylon (a synthetic linear polyamide of high molecular weight) have been used for making the locking plugs. The end of the rod vis Asheared olf to form a plug which is forced into a recess or hole dnille'd in the side of the threaded element and intersecting a threaded portion thereof.

Considerable ditliculty has 'been encountered in cutting and inserting such plugs due to -the fact that the plastic rod is not raccurate in diameter. As extruded, the rod can be held to a tolerance of plus or minus .002.of an inch at best and normally the rods vary considerably more than the specified tolerance. If the plastic rod is oversize, it will not feed properly through the shearing apparatus and as a consequence the apparatus is frequently shut down for repairs and for clearing. The undersize rod will feed but the plugs cutftherefrom do not iit tightly in the holes or recesses in the threaded elements and will fall out of the threaded element during shipment. Efforts to control the diameter of the rods by scraping, grinding, milling or the like have not been very satisfactory because of the expense involved. This is due to the material being in coil form and of circular cross section.

Another disadvantage of the prior types of plug cutting operations is that the holes drilled for thereception of the plugs must be of considerable depth in order to hole the plugs securely.

The present invention overcomes the disadvantages inherent in theprior methods of cutting and inserting the resilient plugs in threaded elements and has, in addition, certain advantages which are neither inherent in the prior products nor obtainable with the methods and apparatus as used heretofore.

In accordance with the present invention, instead of using round or cylindrical rods, the plugs are formed by punching them from half round or similarrods of plastic by means of a punch moving at a right angle to the axis `of the rod. inasmuch as the diameter of the plug is controlled entirely by the diameter of the cutting punch or die, it is possible to shear the plugs cleanly and within close tolerances from the semi-cylindrical rods. The resulting plugs are cylindrical in cross section, but have one flat end conresponding to the at side of the rod and a curved end corresponding to the curvature of the curved face of the rod. When such plugs are cut from a rod of suitable size and inserted in a lock screw, for example, the curvature of the outer end of the plug conforms'sub- States Patent ice stantiallyito the curvature of the threads vof the lock screw. K t

A'particular advantage of the use of a semi-'cylindrical rod is that plugs of various diameters may be punched therefrom with Va high degree of accuracy without requiring that the cross-sectional dimensions of the extruded rod be maintained within very close tolerances.

An unexpected advantage of the newplug is that its over-all length Vcan bejdecreased because of -its more precise size `so that the holes drilled inthe lock screws, bolts and similar'y externally threaded members may be as much as v60% shallower than those required before without danger of the plug being accidentally dislodged from `such shallower holes. As a result, -lock screws or bolts having "the-new form of plug therein have of the tensile strength of plain screws for bolts when the nylon plugis properly engaged.

Moreovenfithas beenfound that the static torque required to remove lock screws of the type having'the new plugs'therein is increased nearly 50% above that required to lremove a similar screw having the prior: type of plug therein. .Evidently,`the improved torque characteristics :arise because of the fact that the axis of the plug. extends transversely of 4themolecular bundles or chains which `are disposed vlengthwise of'the semicylindrical 'rodsby the extrusion'. thereof. .The'transverse positioning ofthe bres evidentlyintroduces a vgreater yelasticity and resista-nceto permanent deformation -as evidenced by'the -fa'ct that the static removal torque afterva 'great number of removals of the threaded element isstill farsuperior to the static removaltorque required toremove a similar devicehaving a plug thereinwhich is cut olf the end of the rod.

For-a better understanding of theV present invention, reference may behad totftheaaccompanyin'g ydrawingsin which:

Fig. l is a view of-one sideof an extruded rod'of .nylon or similar plastic shown greatly enlarged;

' Fig. 2 is a'view in end elevation of t-he'rod--shown in Fig. l;

'iied-foirms'ofcuttingand punching devices for severing the nylon plugs and inserting them in recesses in screws;

`FiguSvis a view in section through atypical threaded element containing the new locking plug; vand Fig. 9 is a viewk in elevation of a portion of the threaded element.

As shown in Figs. vl and 2, the invention may be practiced kwith extruded nylon or other equivalent plastic rod 10 of semi-cylindrical cross section. The plastic rod need not be precisely `semi-circular in cross section. As la matterrof fact, if the plugs are to be inserted in nuts or the like, the rod may have .-a fiat face and an opposite concave face or liatface.

During the extrusion of nylon rod of a type shown'in VFigs. zl and 2, the molecular chains are oriented with the result that they extend lengthwise of the rod `in the form of tiny parallel vbundles. Endwise'orientation of the molecules evidently renders the rod lessresilient endwise thanl transversely.. Y

In accordance with the present invention, in the production of yplugs for insertion Vin'lock nuts, jlockscrews and other threaded elements, the plugs are/formed 'by punching transversely through lthe rod 'l0 to produce cylindrical plugs 11, -11 of smaller diameterthan the y width of `the Yrod 110, and vwhichgfhave 'flatinner fends "12 and'convex outer =ends 13." 1rthemed `10 -is 'chosen so that its outer surface has essentially the same radius of curvature as the curvature of the crests of the threads of the threaded element into which the plug is to be inserted. Accordingly, when the plugs 11 are punched from the rod and pressed into a recess 14 in a screw or the like as shown in Figs. 8 and 9, the outer surface 13 of the plug is essentially concentric with the crest line of the threads of the screw 15 and extends slightly beyond them.

Figs. 3 and 4 illustrate one apparatus by means of which the plastic rod can be advanced and punched to produce the locking plugs and by means of which the plugs are inserted into a screw threaded element. As shown in Figs. 3 and 4, a typical device may include a frame plate having a pair of crossbars or bearing blocks 21 and 22 at its upper end. The crossbars 21 and 22 have journaled in them the roller 23 and the feed wheels 24 and 25, the latter having concave knurled inner surfaces 26 and 27, respectively. The feed wheels 24 and 25 are fixed to a drive shaft 30 which is driven `to rotate the wheels in a counterclockwise direction as viewed in Figs. 3 and 4 to feed semi-cylindrical rods 10 of plastic downwardly. rl`he convex surface of the rod engages in the knurled groove 26 or 27 of the feed wheels. The rods 10 are moved downwardly through an opening and guide passage 31 between a die member 32 and a cooperating punch 33. The punch 33, as will be described more fully hereinafter advances through the rod 10 to sever a plug therefrom. Cooperating mechanism forces the plug through the guide opening 32 and a channel 35 in a guide or sizing block 36 and into the drilled recess 37 in a screw 38 or other threaded member.

The guide block or die 32 may be formed of hardened steel or the like and is mounted in a downwardly de-Y pending llange or plate 39 in front of a frame member 20.

The punch 33 is guided in an opening 40 extending transversely through the frame member 20 in alignment with the axis of the die 32. The punch 33 may consist of a tubular cutting die 43 having a sharpened inner edge 44 which serves to cut through the rod 10. The tubular member 43 is guided in a sleeve 45 which is slidable in the hole 40. The entire sleeve and cutter assembly 43, 45 is advanced by means of a bell crank lever 46 having its upper end engaging in a collar 47 threaded on the cutting member 43 near its outer end and bearing against a ange 48 on .the sleeve 45.l The collar 47 is locked in position by means of a lock nut '50 also threaded on the threaded end of the cutter 43.

The hell crank lever may be oscillated by means of a cam slide 51 which is reciprocated back and forth with a cam surface 52 thereon engaging a cam follower roller 53 on the outer end 54 of the bell crank lever 46. Reciprocation of the cam bar 51 will advance the cutter 43 and retract it.

The severed plug is pushed into the recess 37 by means of a plunger 55 mounted ona push rod 56. The plunger `55 is telescopically received within the cutter 43 and 1s reciprocable between a position behind the shearing edge 44 of the cutter and a position well in advance of the shearing edge to force the cut plug `through the sleeve 32 and the channel 35 into and seat it in the recess 37. The plungerV 55 may be advanced in any suitable way such as by means of a separate cam operated alternately with respect to the cam slide 51 or by electrical or hydraulic means as may be desired.

In order to facilitate the operation of a device the feed wheel 27 may beroperated intermittently to adprovision for slippage relative to the rod 10 to-enable intermittent cutting .and ejection of the plug.

ItA will'be understood that the punch and plunger lmechanism is susceptible to considerable variation. Eor

example, as shown in Fig. 5, the cutting punch 60 may be a relatively short frusto-conical member which is mounted in a threaded sleeve 61 at the front end of a slide 62. A plunger 63 is slidable within the punch 60 and is provided with an operating disc or collar 64 which bears against one end of a helical spring 65 interposed between it and the back end of the punch 60. With this arrangement, a cam member or crank may bear against the collar and advance the entire punch and plunger assembly againstthe rod 10 to sever the plug therefrom. When the punch comes up against the guide or die member 66, the plunger 63 advances farther by compressing the spring 65 to force the severed locking plug'through the die member 66 into the recess 67 in the screw element 68. l i

A variation of the above-described punch device is shown in Fig. 6. In this device, the punch 70 is received in the end of a tubular holder 71 and is provided with a ared base 72 against which bears a heavy helical spring 73. The other end of the spring bears against a collar 74 xed to the shaft of the plunger 75 which extends through the punch. Reciprocation of the plunger 75 will cause the punch 70 to advance and sever the plug and upon stoppage of the punch by engagement with the die member 76, the plunger 75 will `continue to advance and will force the plug into the .recess in the screw 77.

Another modification of the punch and ejecting plunger is shown in Fig. 7. In this variation, the punch is mounted in the front end of a heavy supporting block 81 provided with an internal recess 82 to receive the actuating plunger 83 in which the ejecting plunger 84 is mounted. The ejecting plunger extends through the punch 80 in the manner described above. The actuating plunger 83 is provided with an annular groove 85 therein near its end for receiving the spring pressedV balls 86 and 87 which are carried by the housing 81. The housing with the punch 80 thereon is advanced by the plunger S3,

but upon encountering resistance such as the die plate 88,

the halls 87 will be forced back and will allow the plunger to advance to eject the plug and force it into the screw 89.

The ball andgroove connection, of course, affords the vof the screw or nut, a condition which produces most vadvantageous results. For example, it has been found that theV static torque on the 15th removal of a screw such as that shown in Figs. 8 and 9, is 18.25 inch lbs., as compared with only 13.95 inch lbs. for the same screw provided with a standard plug formed by cutting it olf the end of a cylindrical nylon rod.

After being subjected to elevated temperatures of 250 F., the new plugs provide a static torque of 30.3 inch lbs. whereas the standard nylon plug provides a static torque of only 20.2 inch lbs. Thus, screws or nuts having the new plugs have nearly 50% greater holding capacity than 'the nuts made with the prior type of plugs. In addition to the advantages Vderived from the plugs themselves, it has been found that the holes drilled in the screws or other threaded elements need be only about 40% as deep as .the prior holes to retain the new plugs against accidental loss. As a result, screws having the new plugs have .100% of the tensile strength of plain screws of the same size when properly installed. For aircraft work and other elds whererhigh tensile strength and low weight are required, this improved characteristic is of great practical importance. It will be understood that the new plugs may be used in articles other than the screws or bolts shown herein and that they may be used in many other threaded elements such as nuts, locking inserts and any other field where a threaded element must be used and which must be retained in position by suitable locking means to prevent its loosening or loss due to vibration and stresses thereon.

Accordingly, the illustrative embodiment of apparatus and method in accordance with the present invention should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

1. A method of making threaded locking devices comprising, drilling a hole substantially radially of the locking device, advancing a rod of resilient plastic substantially parallel with the axis of said locking device, said plastic having a molecular orientation lengthwise of said rod, punching transversely through said rod to cut a plug therefrom and pushing the severed plug endwise into said hole.

2. The method set forth in claim 1 in which the locking device is an externally threaded member.

3. The method set forth in claim 1 in which the locking device is an externally threaded member and the rod is semi-cylindrical in cross-section and the plug punched therefrom has a convex outer end conforming substantially to the curvature of the crests of the threads on said member.

4. The method set forth in claim 1 in which the rod is formed of nylon.

5. A locking device comprising a threaded member having a substantially radially disposed hole therein and a locking plug in said hole, said plug being of substantially cylindrical shape and being composed of a resilient linear polymer plastic of the long molecular chain type in which the molecular chains are substantially parallel and oriented substantially transversely with respect to the axis of said plug.

6. The locking device set forth in claim 5 in which the plug is composed of extruded nylon.

References Cited in the flle of this patent UNITED STATES PATENTS 1,435,586 Collette Nov. 14, 1922 1,495,687 Grosclaude May 27, 1924 1,914,405 Cummings June 20, 1933 2,217,714 Swanstrom Oct. 15, 1940 2,409,638 Lyon Oct. 22, 1946 2,663,344 Burdick Dec. 22, 1953 2,674,311 Griswold Apr. 6, 1954 FOREIGN PATENTS 372,405 Great Britain May 9, 1932

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