US2961179A

US2961179A - Pirn lock apparatus

Info

Publication number: US2961179A
Application number: US794751A
Authority: US
Inventors: Iii Joseph P Mcnutt
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1959-02-20
Filing date: 1959-02-20
Publication date: 1960-11-22
Anticipated expiration: 1977-11-22

Description

1960 J. P. MCNUTT m PIRN LOCK APPARATUS 2 SheetsShe'et 1 Filed Feb. 20, 1959 IE-I-II QTA JOSEPH P. Mc NUTT ILI gpww ATTORNEY Nov. 22, 1960 J. P. MCNUTT m PIRN LOCK APPARATUS 2 Sheets-Sheet 2 Filed Feb. 20, 1959 INVENTOR JOSEPH P. MCNUTT .UI

C 6 BY W 6 ATTORNEY 8 5 4 u 4 A/ .k 2 3 United States atent O PIRN LocK APPARATUS Joseph P. McNutt III, Newark, DeL, assignor to E. I. du Pont de Nernonrs and Company, Wilmington, Bah, a corporation of Delaware Filed Feb. 20, 1959, Ser. No. 794,751

8 Claims. (Cl. 242-465) This invention relates to a pirn lock apparatus, and particularly to a centrifugally actuated pirn locking apparatus wherein locking action is obtained solely during the relatively rapid rotation of the pirn and is automatically released before the pirn comes to rest.

It is customary to provide locks for the rotating pirns of the textile industry to safeguard against the pirns flying off the rapidly rotating spindles as a result of unbalanced forces which develop during rotation which induce move ment of the pirns axially of the spindles. Such locks have to be positive in operation and relatively sturdy, due to the fact that service conditions are severe and the loads encountered are, particularly with the large size pirns now gaining favor in the industry, quite high. Hitherto it has been the practice in the art to provide pirn locks which are actuated by the operator, as in the construction of U.S.P. 2,250,560, or as a. result of frictional deflection on the part of elements of the spindle or pirns themselves, such as the design of 2,365,980. These solutions of the problem are not entirely satisfactory, because the mechanisms are relatively complicated and are therefore high in first cost and maintenance. More importantly, the prior art constructions require manual labor on the part of the operators and, with the large yarn packages which are now coming into vogue, this often necessitates excessive labor beyond the easy capabilities of any but relatively strong persons.

Accordingly, it is a principal object of this invention to provide a pirn lock apparatus which is completely automatic in operation. Other objects of this invention are to provide a pirn lock which is low in first cost, sturdy in construction and which requires substantially no maintenance. The manner in which these and other objects of this invention are obtained will become clear from the detailed description and the following drawings, in which:

Fig. 1 is a side elevation sectional view of the base portion of a driving spindle which is provided with a preferred embodiment of pirn lock according to this inven- 'tion, showing also the base portion of a pirn mounted in cooperative relation to be driven by the spindle together with a locking element disposed in locking position,

Fig. 2 is a top plan view of the driving element of the apparatus of Fig. l, with locking elements omitted, taken on line 22 thereof,

Fig. 3 is a top plan view of the locking cap of the apparatus of Fig. 1,

Figs. 4, 5 and 6 are, respectively, side elevation, and sectional views on lines 5-5 and 6-6, Fig. 4, of an alternate design of locking element which can be utilized in place of the preferred ball configuration of Fig. 1, and

Figs. 7, 8 and 9 are side elevational, sectional views with locking element disposed in locking position of three additional embodiments of pirn lock according to this invention, these showings being limited to details disposed to the left of the center line of spindle 10, since the righthand constructions are identical with that of Fig. l, and Fig. 7 relating to magnetic unlocking, Fig. 8 to springbiased unlocking and Fig. 9 to counterbalancing weight unlocking.

Generally, the pirn lock of this invention comprises a boss integral with the driving spindle provided with a plurality of bores disposed in planes radial to the driving spindle and opening at their outward ends adjacent a shoulder provided internally of the pirn when the pirn is in position to be driven by the spindle, each bore being provided with a locking element adapted to move longitudinally within the bores under the centrifugal forces accompanying spindle rotation to a position obtruding beyond the outward ends of the bores and transverse the shoulder provided internally of the pirn, and means overlying the outer ends of the bores to at all times retain the locking elements within the bores. Preferably, the boss integral with the driving spindle constituting part of the pirn lock is physically integral with the driving means transmitting rotational force from the driving spindle to the pirn mounted on the spindle; however, this is not essential and the pirn lock can equally well be located apart from the driving means.

Referring to Figs. 1, 2 and 3, relating to the preferred embodiment of this invention, 10 represents a vertically disposed conventional pirn driving spindle which is to tated by a suitable motor or central drive means, not shown, and which is provided with an integral waste spool shown in part at 11., which rotates with the spindle. Spindle 10 is provided with a driving element 14 securely attached to spool 11 by socket-headed machine screws 15, of which there are three in number, although only one is shown in Fig. 1.

Driving element 14 in the plan view of Fig. 2 has an outside profile consisting of three arcuate surfaces 16 of common radius drawn from the center of bore 17 accommodating spindle 1i}, which are separated one from another by flat surfaces 18. As shown in Figs. 3 and 1, locking cap 21} is symmetrical in general plan profile with driving element 14 and is of the same or slightly lesser limiting radial dimensions but is provided with a frustoconical surface 21 at the top, as indicated in Fig. 1, terminating at the periphery of bore 22 accommodating spindle 10. Element 14 is provided with three equiangularly spaced longitudinal bores 24 receiving the screws 15 and these bores match with similar bores 25 in locking cap 20, which latter are formed to a larger diameter over the top lengths to accept the socket heads of these screws. These heads abut against surfaces 26 in cap 20 when screws 15 engage to the full the tapped bores 27 in waste spool 11, thereby locking 14 and 20 firmly to spool 11.

The base end of the pirn used in conjunction with the apparatus of this invention is indicated at 30, the pirn comprising a stiff tubular body portion of met"! or the like provided with a bushing 32 integraly secured to the interior of the pirn by a peened over intermediate sleeve 31. The inside profile of bushing 32 as seen in plan is symmetrical with that of driving element 14, except having slightly larger bore dimensions to permit the pirn to be slid easily over element 14 from the top end of spindle 10, whereupon the base of the pirn rests on the top of spool 11 and the pirn is thus supported by the spool. Under these circumstances the opposed faces of driving element 14 and bushing 32 constitute cooperating drive surfaces and driving spindle 10, in the course of rotation, impels pirn 3% with it.

The locking agency of the embodiment of Figs. 16, inclusive, comprises the three inwardly inclined bores 33 which are each provided with a freely movable locking element 34, the preferred configuration of which is spheri cal, as represented in Fig. 1. As seen in plan in Fig. 2, bores 33 are equiangularly disposed with respect to one another and are also equiangularly separated from screws 15 assembled in bores 24, to thereby provide a balanced structure with respect to the axis of rotation of spindle 10. Bores 33 are all disposed in planes radial of bore 17, and thus of spindle 10, at a common inclination greater than the angle of repose of locking elements 34 disposed therein, a suitable angle being about 60 measured from the horizontal.

In the preferred arrangement the outward ends of bores 33 have their lower extremities disposed on about the same horizontal'plane as the upper surface 35 of bushing 32. However, this is not essential and, if the length of bushing 32 extends axially of spindle 10 to a greater extent than shown in Fig. 1, it is only necessary that the region of the bushing adjacent the bores be cut away in a radially outward direction to form a shoulderover which locking elements 34 obtrude during spindle rotation to thereby lock pirn 30 against axial movement with respect to spindle 10. Accordingly, the term "shoulder as employed in the claims is intended to comprehend generically both the top surface of bushing 32 adjacent the bore outward ends as well as any surface below the top level formed by cutting away the bushing in a radial direction to thereby create a path for the transverse obtrusion of the locking elements of this invention into pirn locking position.

Locking elements 34 can conveniently consist of steel ball bearings about in diameter, which slide easily within bores 33 having a circular cross section of 0.380- 0385" diameter. As seen in Fig. 1, the bottom surface of locking cap 20 overlies bores 33 to a degree where the bores are partially closed 01f and balls 34 retained against escape outwardly under all circumstances. At the same time the efiective overhang of locking cap 20 must not be so great as to bar the obtrusion of locking element 34 transverse the contiguous shoulder of bushing 32. With diameter balls as locking elements a protrusion of about 3: of the balls across the top of bushing 32 has proved entirely adequate. The balls are, of course, assembled within bores 33 prior to assembly of locking cap 20 and, in operation, lie at the bottoms of the bores whenever driving spindle 10 is at rest or, in fact, during slow rotation while speed is being picked up or lost in the course of'spindle acceleration or deceleration, respectively. However, when a speed of 5 to of full operating speed is attained, balls 34 are thrown to the outward ends of bores 33 and their surfaces obtrude radially over surface 35, thereby locking pirn 30 against movement axially of spindle 10.

In a typical installation employing the preferred embodiment 'of Figs. 1-3, pirns constructed with shells of 16 gage steel of wall thickness varying from about 0.062 to 0.067" were employed, the net weight of individual pirns being 4 /2 lbs. These pirns had an overall length of and were provided interiorly with centering bearings located 9" from the base end encircling driving spindle 10 with a sliding fit to prevent wobbling of the pirn in the course of yarn winding. In practice, the net weight of yarn wound on each pirn was about 9 lbs., making the total weight of yarn plus pirn about 13 lbs. The normal winding speed was about 3800 r.p.m., under which circumstances very cons derable vertical forces sometimes developed which resulted in throw-off of the pirns from the driving spindles. The pirn lock of Figs. l-3 was completelyeffective in preventing such occurrences.

For best results it is preferred that a plurality of bores 33 and locking elements 34 be utilized, so as to safeguard against any possible cocking of the pirn on the spindle, such as might occur where pirn retention is limited to a singe point only. Also, the utilization of a multiplicity of locks permits balanced mass distribution at equiangular spacings around the driving spindle, thereby eliminating unbalance during the high speed rotation of spindle 10. While it is preferred to use three locks as represented in Figs. 13, an arrangement of only two diametrically opposed locks is equally practicable or, if desired, an even greater number than three can be utilized.

spherically shaped locking elements 34 are preferred; however, Figs. 4-6 depict an alternate design of locking element, which is effective to distribute load to locking cap 20 over a somewhat greater area. This construction utilizes a generally cylindrical form of element beveled off on opposite ends at with respect to one another, so as to provide 'a fiat surface 38, beveled typically at an angle of 35 from a plane transverse 34' as an example, opposed to the underside of the locking cap and another flat surface 39 parallel with the axis of driv ing spindle 10 when the locking element is disposed within its bore 33. It will be understood that, under these circumstances, the center of mass of locking element 34 is in a plane radial to the axis of spindle 10 but below the longitudinal axis of 34', which makes the locking element self-orienting as regards rotation about its own axis during rotation of spindle 10. This selforientation is facilitated by guiding abutment of'surfaces 38 and 39 against the locking cap and spindle 10, respectively, at the extremes of travel of element 34' within bore 33, since the locking element has a full-circular profile at its greatest cross section as shown in Fig. 6. The end A of element 34 to the left of a vertical dropped from the left-hand boundary of surface 38 as seen in Fig. 4 eflects the locking action by overlying an oppositely' disposed shoulder in the pirn bushing when element 34 slides to the outward end of its bore 33' during high speed rotation of the driving spindle. Disengagement'o-f this design of locking element is also automatic and occurs well in advance of the driving spindle coming to rest.

Three other embodiments of this invention are shown in Figs. 7-9, the same reference characters being utilized throughout to designate elements identical with those hereinbefore described for the preferred embodiment of Figs. l-3. The additional embodiments all employ bores 33 which are disposed substantially normal to the axis of spindle 10, and those of Figs. 7 and 8 rely on retraction forces other than gravity, so that the spindles may in these instances be disposed other than upright. In the latter cases, of course, the retractive means employed must, with the spindle stationary, exert suflicient force on locking elements 34 to overcome the force of gravity and thereby enable positive clearance of elements-34 from looking position.

In the embodiment of Fig. 7 permanent magnets 42 provide the retraction force counter to the centrifugal forces exerted on locking elements .34 during spindle rotation, and the locking elements must necessarily be fabricated from magnetic materials, such as iron or steel. it will be understood that magnets '42 are fixedly attached internally of the assembly comprising driving element I l-driving spindle 1t), and this can be effected conveniently through the use of clamp members, suitable cements or the like, not shown, so as not to impair the magnetic properties by the drilling of holes through the members, or as a result of other machine work. It i's'preferred to employ relatively strong magnets in this service, such as those fabricated from Alnico V, which has the approximate composition: Al 8%, Ni 14%, Co 24%, Cu 3%, balance Fe. This permits the use of relatively small magnets 42 adapted to -fit easily within bores 33, while still leaving sufficient open space in the outward ends of the bores for the complete reception of locking elements 34. However, this particular magnet disposition is not essential and, in fact, magnets 42 may be mounted adjacent to and parallel with the axis of spindle 10, or in other ways depending on the requirements of desi n in any particular case. It is, of course, essential in this embodiment, and also in those hereinafter described, that the retraction forces exerted on loosing elements 34 be sufiiciently large to retain these elements positively out of locking position when driving spindle 10 is at, 'or near, rest position while, at the same time, being overcome by centrifugal forces exerted on elements 34 at, or preferably substantially in advance of, normal operating spindle speeds. Although the speeds at which locking action is obtained are subject in some degree to design selection, this invention is generally useful where spindle Speeds exceed about 500 rpm.

Referring to Fig. 8, the retraction means in this embodiment consists of a tension spring 43 of unstretched length less than the difference between the length of bore 33 and the maximum dimension of locking element 34 measured radially with respect to spindle 10. In the construction shown the inward end of spring 43 is fixedly secured to spindle 10, although this attachment can just as readily be made to the driving element 14, or to other points, whereas the other end of the spring is secured to 34. In operation, spring 43 functions exactly as hereinbefore described for the other embodiments of this invention, retracting elements 34 from locking position when driving spindle is at, or near, rest position, while permitting outward displacement of these elements into locking position under the centrifugal forces accompanying spindle rotation at substantial speeds well below normal operating speeds.

If desired, an alternative spring construction can be employed wherein the spring is proportioned with such distribution of mass relative to length that the outward end of the spring 43 per se functions as the locking element, in which case a separate locking element 34 can be dispensed with.

The embodiment of Fig. 9 is an alternate design of a gravity-retracted pirn lock according to this invention and it is therefore necessary that driving spindle 10 be disposed in upright position in the same manner as hereinbefore described for the embodiment of Figs. l-3. Here the spindle is drilled axially over a substantial length 44 extending well past the lower horizontal plane in which bores 22 are disposed. The wall of the driving spindle is drilled radially to provide ports 45 opening into the bores, which ports are of smaller diameter than the width dimensions of elements 34, so as to prevent withdrawal of the latter from the inward ends of bores 33. A weight 46 freely movable within bore 44 provides the retractive force applied to all of the locking elements 34 simultaneously, which force is exerted through the agency of cords 47, each attached at one end to the elements and at the other end to the hook 48 fixedly secured to the top of weight 46. As with the other embodiments hereinbefore described, the retractive force exerted by gravity on weight 46 must be proportioned to the centrifugal forces exerted on locking elements 34 to insure that elements 34 positively take their pirn locking position when the driving spindle is rotating at substantial speeds above rest position, and especially prior to reaching normal operating speeds, and just as positively retract inwardly out of locking position prior to the driving spindle coming to rest.

The locking elements 34 in the embodiments of Figs. 8 and 9 can, if desired, be provided with emergency retraction cords threaded through suitable holes provided in the driving element, so that an attendant can always manually retract elements 34 out of locking position in the event that springs 43 or cords 47 should ever fail in service. Or emergency magnetic retractors or the like may instead be utilized for this purpose.

The preferred embodiments of this invention utilize locking devices which are disposed within the driving element per se, since such designs concentrate the masses at the base of the spindle where maximum rotational stability is obtained, particularly at high spindle speeds. However, the pirn lock can equally well be entirely independent of the particular driving element utilized and, in fact, can be disposed within a boss conveniently located at any point along the length of the spindle which the designer may choose, such as adjacent to the pirn centering bearings hereinbefore referred to, or elsewhere. Also,

while the preferred embodiments hereinbefore described possess a driving connection between spindle and pirn consisting of mating surfaces in abutment one with another, it will be understood that any other driving arrangement known to the art is equally suited to the purposes, since the driving means employed is in any case completely independent of the pirn lock of this invention.

From the foregoing, it will be understood that this invention can be modified extensively within the skill of the art without departure f:om the essential spirit, and it is intended to be limited only by the scope of the following claims.

What is claimed is:

1. A centrifugal pirn lock apparatus comprising in combination a rotatable spindle, a pirn adapted for concentric mounting with respect to said spindle, said pirn being provided interiorly with an integral bushing, driving means integral with said spindle engaging in driving relationship with said pirn, a boss integral with said spindle provided with a plurality of straight bores of substantially the same diameter disposed in planes radial of said spindle at equal angular spacings one from another opening at the lower extremities of their outward ends in substantially the same horizontal plane as occupied by a shoulder provided in said bushing contiguous to said boss with said pirn in driving position, individual locking elements of a length less than the length of said bores and of substantially equal mass disposed within each of said bores and adapted to move longitudinally outward within said bores under the centrifugal forces accompanying acceleration of said driving spindle to full speed rotation to a locking position obtruding beyond the outward ends of said bores and transverse said shoulder in said bushing and to retract inwardly towards said spindle and out of said locking position during deceleration of said spindle to rest, and a locking cap mounted coaxial with said spindle in fixed relationship therewith of peripheral boundary measured radially of the spindle substantially no greater than the peripheral boundary of said boss along the same radial line, said locking cap overlying the outward ends of said bores a sufficient amount to prevent escape of said locking elements from said bores during rotation of said driving spindle while permitting at least a portion of said locking elements to extend radially with respect to said spindle transverse said shoulder and beyond the inside extremities of said bushing integral with said pirn to thereby lock said pirn against axial movement with respect to said spindle.

2. A centrifugal pirn lock apparatus comprising in combination a rotatable spindle, a driving element mounted coaxial of said spindle in fixed relationship therewith, said driving element being provided with at least one driving surface for abutment with a mating surface provided interiorly of a bushing integral with a pirn intended for use in conjunction with said apparatus, a plurality of straight bores of substantially the same diameter provided in said driving element in planes radial of said spindle at equal angular spacings one from another opening at the lower extremities of their outward ends in substantially the same horizontal plane as occupied by a shoulder provided in said bushing contiguous said driving element with said pirn in driving position, individual locking elements of a length less than the length of said bores and of substantially equal mass disposed within each of said bores and adapted to move longitudinally outward within said bores under the centrifugal forces accompanying acceleration of said driving spindle to full speed rotation to a locking position obtruding beyond the outward ends of said bores and transverse said shoulder in said bushing and to retract inwardly towards said spindle and out of said locking position during deceleration of said spindle to rest, and a locking cap mounted coaxial with said spindle in fixed relationship therewith of peripheral boundary measured radially of said spindle substantially no greater than the peripheral boundary of said driving element along the same radial line, said locking cap overlying the outward ends of said bores a suficient amount to prevent escape of said locking elements from said bores during rotation of said drivingspindle while permitting at least a portion of said locking elements to extend radially with respect to said spindle transverse said shoulder and beyond the inside extremities of said bushing integral with said pirn to thereby lock said pirn against axial movement with respect to said spindle.

3. A centrifugal pirn lock apparatus comprising in combination a rotatable spindle, a driving element mounted coaxial of said spindle in fixed relationship therewith, said driving element being provided with at least one driving surface for abutment with a mating surface provided interiorly of a bushingintegral with a pirn intended for use in conjunction with said apparatus, a plurality of straight bores of substantially the same diameterprovided in said driving element in planes radial of said spindle at equal angular spacings one from another opening at the lower extremities of their outward ends in substantially the same horizontal plane as occupied by a shoulder provided in said bushing contiguous said driving element with said pirn in driving position, individual locking elements of a length less than the dength of said bores and of substantially equal mass disposed wtihin each of said bores adapted to move longitudinally outward within said bores under the centrifugal forces accompanying acceleration of said driving spindle to full speed rotation to a locking position obtruding beyond the outward ends of said bores and transverse said shoulder in said bushing, retraction means disposed internally of said driving element biasing said locking elements inwardly along said bores in opposition to said centrifugal forces with a predetermined force effecting retraction of said locking elements out of said locking position during deceleration of said spindle to rest, a locking cap mounted coaxial with said spindle in fixed relationship therewith of peripheral boundary measured radially of said spindle substantially no greater than the peripheral boundary of said driving element along the same radial line, said locking cap overlying the outward ends of said bores a sufiicient amount to prevent escape of said locking elements from said bores during rotation of said driving spindle while permitting at least a portion of said locking elements to extend radially with respectrto said spindle transverse said shoulder and beyond the inside extremities of said bushing integral with said pirn to thereby lock said pirn against axial movement with respect to said spindle.

4. A centrifugal pirn lock apparatus according to claim 3 wherein said locking elements are fabricated from magnetic material and said retraction means consists of individual permanent magnets secured in fixed position within said bores intermediate said locking elements and said spindle sufficiently near said locking elements so as to exert a substantial force directed inwards of said bores upon each said looking element when said locking elements occupy said locking position, but less than the magnitude of said centrifugal forces accompanying acceleration of said spindle to full speed rotation.

5. A centrifugal pirn lock apparatus according to claim 3 wherein said retraction means consists of individual tension springs disposed within said bores fixedly secured at their inner ends with respect to said spindle and said driving element and at their outer ends to said locking elements, said tension springs having unstretched lengths such as to exert a substantial spring force directed inwards of said bores upon each said locking element when said locking elements occupy said locking position, but less than the magnitude of said centrifugal forces accompanying acceleration of said spindle to full speed rotation.

6. A centrifugal pirn loci: apparatus according to claim 3 wherein said spindle is annular in form and disposed radial ports cut through the spindle 'wall and opening into the, inward ends of said bores, and said retraction means consists of a weight disposed within the bore of said spindle in freely movable relationship axially thereof vunder the influence of gravity, and flexible strands threaded through said radial ports of greater length than the lengths of said bores attached at one end to said weight and at the other end to individual ones of said locking elements, said weight exerting a substantial force directed inwards of said bores upon each said locking element when said locking elements occupy said locking position, but less than the magnitude of said centrifugal forces accompanying acceleration of said spindle to full speed rotation.

7. A centrifugal pirn lock apparatus comprising in combination a substantially vertical rotatable spindle, a driving element mounted coaxial of said spindle in fixed relationship therewith, said driving element being provided with at least one driving surface for abutment with a mating surface provided interiorly of a bushing integral with a pirn intended for use in conjunction with said apparatus, a plurality of straight bores of substantially the same diameter provided in said driving element in planes radial of said spindle at equal angular spacings one from another oriented upwardly from the inward ends of said bores adjacent said spindle to the outward ends of said bores adjacent said bushing at a common inclination greater than the angle of repose of a rigid mass disposed for free movement within any one of said bores, the lower extremities of said outward ends of said bores lying in substantially the same horizontal plane as occupied by a shoulder provided in said'bushing contiguous said driving element with said pirn in driving position, individual locking elements of a length less than the length of said bores and of substantially equal mass disposed within each of said bores in free movable relationship axially of said bores, and a locking cap mounted coaxial with said spindle in fixed relationship therewith of peripheral boundary measured radially of said spindle substantially no greater than the peripheral boundary of said driving element along the same radial line, said locking cap overlying the outer ends of said bores a sufiicient amount to prevent escape of said locking elements from said bores during rotation of said driving spindle while permitting at least a portion of said locking elements to extend radially with respect to said spindle transverse said shoulder and beyond the inside extremities of said bushing integral with said pirn to thereby lock said r-irn against axial movement with respect to said spindle.

8. A centrifugal pirn lock apparatus comprising in combination a substantially vertical rotatable spindle, a driving element mounted coaxial of said spindle in fixed relationship therewith, said driving element being provided with at least one driving surface for abutment with a mating surface provided interiorly of a bushing integral with a pirn intended for use in conjunction with said apparatus, said driving element being of greater height measured axially of said spindle than said bushing when said pirn is disposed coaxial of said spindle in position to be driven by said apparatus, a plurality of straight bores of substantially the same diameter provided in said driving element in planes radial of said spindle at equal angular spacings one from another oriented upwardly from the inward ends of said bores adjacent said spindle to the outward ends of said bores adjacent said bushing at a common inclination greater than the angle of repose of a rigid mass disposed for free movement within any one of said bores, the lower extremities of said outward ends of said bores lying in substantially the same horizontal plane as occupied by the top surface of said bushing adjacent said driving element with said pirn in driving position, individual locking elements of a length less than the length of said bores and of substantially equal mass disposed Within each of said bores in free movable "relationship axially of said bores, and a locking p mounted coaxial with said spindle in fixed relationship therewith of peripheral boundary measured radially of said spindle substantially no greater than the peripheral boundary of said driving element along the same radial line, said locking cap overlying the outward ends of said bores a sufiicient amount to prevent escape of said locking elements from said bores during rotation of said driving spindle while permitting at least a portion of said locking elements to extend radially with respect to said spindle beyond the inside extremities of said bushing integral with said pirn to thereby lock said pi-rn against axial movement with respect to said spindle.

References Cited in the file of this patent UNITED STATES PATENTS Lawrence Nov. 1, 1904 Metcalf Nov. 29, 1904 Stimpson Mar. 14, 1933 Stevens Apr. 14, 1953 FOREIGN PATENTS France Nov. 6, 1922