US3134218A - High speed false twist spindle drive - Google Patents

Description

May 26, 1954 R. G. HILBERT 3,134,218

HIGH SPEED FALSE IwIsT SPINDLE DRIVE RICHARD G. HILBERT BY m4,@

AT TORNE Y May 26, 1964 R. G. HILBERT HIGH SPEED FALSE TWIST SPINDLE DRIVE 3 Sheets-Sheet 2 Original Filed June 16, 1958 /ff x AWIIHNII INVENTOR. Riemen al1/BERT ATTORNEY R. G. HILBERT HIGH SPEED FALSE TWIST SPINDLE DRIVE Original Filed June 16,- 1958 May 26, 1964 3 Sheets-Sheet 5 EC@ @E s INVENTOR.

l RIU/ARI 'QHILBERr ATTGRNEY United States Patent O 3,134,218 HIGH SPEED FALSE TWIST SPINDLE DRIVE Richard G. Hilbert, Smithfield, R.I., assignor to Leesona Corporation, a corporation of Massachusetts Original application June 16, 1958, Ser. No. 742,234, now

Patent No. 3,044,247, dated July 17, 1962. Divided and this application Nov. 7, 1961, Ser. No. 150,812

vThe present invention relates to textile machinery and is directed more particularly to a machine for imparting false twist to a strand of yarn. This application is a division of applicants prior copending application Serial No. 742,234 tiled June 16, 1958, now U.S. PatentV No. 3,044,247.,

In recentvyears, much attention has been given by the textile art to the so-called crimped synthetic yarns. As is Ywell known, these yarns have been mechanically treated to assume arcrimped or coil-like configuration so that they have a certain inherent elasticity and bulkinessl that distinguishes them from untreated yarns. These properties cause them to be highly desirable for certain applications in which they have encountered unusual consumer acceptance. v

A variety of techniques have been proposed for imparting a crimped structure to synthetic yarns but at the present time only one of these techniques is being practiced on a widespread scale. This procedure involves twisting the yarn, setting the twist, and untwisting the set yarn in av continuous operation without interruption between the individual steps. The continuous twisting and untwisting is accomplished by passing the yarn through a rotating body having some means for engaging the yarn to prevent free twist migration, rotation of the body imparting twist inone direction in the yarn on one side of the body and twist in the opposite direction onV the other side thereof. Thus, an apparent or temporary twist is inserted in the yarn and is immediately removed therefrom as the yarn travels past the body. Spindles adapted for this operation have come to be known as false twist spindles in contrast to true twist spindles which rotate either the delivery or take-,up yarn packages, a A

It is quite apparent that as theV speed of rotation of the false twist spindle is increased, a higher number of turns per inch of temporary twist is imparted to the yarn, :or else the yarn can be given the same number of turns while passing through the spindle at a higher linear speed.

Recognizing this, workers in the art have attempted in.

various ways to effect a material increase in the speed of rotation of false twist spindles. For example, it has been proposed to utilize the principle of electric motorsby constructing the' spindle or yarn-engaging body as lthe armature of an electric motor. i This proposal requires a separate electric motor for each strand of yarn being processed, which is prohibitively expensive for large scale are provided for further reducing the effective load placed ice An object of the invention is to provide a machine embodying a plurality of the'high-speed false-twister units of the present invention, and including means for driving these spindles eiciently and economically.

' A further object of the invention is to provide a machine of the type described wherein means are provided for reducing the load sustained by the high speed members of the driving arrangement.

` Other objects and advantages will be apparent from the following detailed de scription of illustrative embodiment of the invention when read in conjunction with the laccompanying drawings in which: v

FIGURE 1 is an enlarged detail view of a spindle and housing unit of the present invention;

FIGURE 2 is a view in front elevation of the spindle and housing unit of FIGURE l in operative association with a swingassembly, the latter'being shown partially in section to better reveal its details;

FIGURE 3 is a bottom plan view of the swing assembly taken generally along line 3+3 of FIGURE 2 with the supporting members of the assembly shown in section;

and

FIGURES 4 and 5 are front elevation and bottom plan views, respectively, ofa preferred form of a machine embodying the spindle and housing units of the invention and utilizing an improved drive for the units, the showing being diagrammatic in nature.

In general, the high speed false twister spindle of thel invention comprises Va small, lightweight tubular spindle rotatably supported adjacent the ends thereof in a housing. Bearings of special design are interposed between the housing and spindle to permit the attainment of extreme speedsof rotation without bearing failure, undesirable wear on parts or`high rictional heat and means are provided for'supplying limited amounts of lubricant to thebearing. In one practical embodiment, a plurality of spindle and 'housing assemblies are arranged ina single multi-position'machine, the drive for the machine being particularly adapted for use with the assemblies including a main driving belt of sturdy construction and lighter weight secondary belts driven from the mainbelt andl having driving contact with groups of spindles. Means on the secondaryA belt at 'any given point.

Alternative arrangements forA journalingthe spindle inthe housing are contemplated.

Turning now yto a' detailed description of the invention,

reference is made to FIGS.. 1 of the drawings wherein a production. Again, it has been proposed to oat the v spindle yon jets of air inclined so as to exert a rotational as well as vertical force on the spindle. Such an arrangement requires extremely careful balancing ofthe forces involved, and of the jets acting on the spindle, which are usually quite numerous.l iMoreover, the consumption of compressed air in operating a large number of: these spindles is enormous and compressed air is anexpensive commodity. Conventional twister-spindles can, of course, be modified for operation at higher than usual` speeds as by the use of improved `bearings `and other known expedients, but even'when modied they have Vnot been capableof obtaining speeds of much over 50,000 r.p.m. Unfortunately, at these speeds, which are not nearly so high as is desired, bearing failures are excessive and power consumption highudespite the use ofelaborate driving means. l'

preferred embodiment of a single false twist spindle ,and housing unit is disclosed. Each unit, which may `be givenrthe general designation V1,0, consists essentially of a spindle blade 12, a housing 14,` and journals or bearings 16, there between.y Housing 14,v is preferably in the form' lof a generally C-shaped metal block having a thickyflat back portion 18 and a pair Vof legs 20a, 2,01? extending from the ends of the back portion the base or lower leg 2Gb being somewhatthicker thanthe ,upper leg 20a longitudinally of the block. The corners of the block may be' rounded *for sake of appearance. Coaxial, cylindrical bores 22aand 2211 of equal diameter pass through klegs 20a and 20h, respectively, the axis of thebores being parallel tothe plane of back portion 18.

v configurationv and having a diameter slightly less than they Each of thebore's 22a and 22b is adapted toreceivey a cylindrical, plug-like bearing mount 24 which is fabricated from porous material, for example, sintered bronze` or the like, theY two ymountsbeing generally identical in diameterof bores 22a and 22b to facilitate their Yinsertion g l'arY spacing washer` 2,8 being disposed between each ring` therein. Inwardly of housing block 14, i.e. in the direction of the central opening of the C, mounts 24 are held in thebor'es by means of split-retaining rings 26, an annuand mount to seal the mount from dust and the like. Towards the outer ends of the bores, the mounts are held against axial movement by means of bowed or dished retaining r-ings 30, annular spacing washers 32 being again provided between the rings and mounts as a dust shield and also to transmit thrust from the mounts to housing block 14. The retaining rings 26 and 3@ engage internal grooves 33 and 34 respectively provided for that purpose in the walls of the bores. It is necessary that each of the bearing mounts 24 be accurately positioned radially as well as axially with respect to the bores and to this end a small cylindrical passage 36 extends transversely to the axis of the bores through the annular wall of each of legs 20a, Ztlb. A positioning pin 38 is inserted into each of these transverse passages until the internal end of the pin engages a recess 40 provided in the outer surface of each mount.

Each bearing mount 24 has a small' central axiallyv directed bore 42 coaxial with bores 22a and 22h, the internal ends of these small central bores being outwardly flared at a relatively large acute angle as at 44. Two substantially identical slots or channels 46 are cut into the internal wall of each mountbore 42, extending longitudinally the full length ofthe Wall, with their axes parallel to the bore axis, and radially into the wall a distance equal to approximately one-half of the radial thickness of mount 24. There is disposed against the bottom wall of each slot 46 a thin metal strip or plate 43 roughly coterminous with the slot. The two slots in each mount 24 are preferably arranged with their center lines spaced 90 from each other and 135 from the axis of positioning pin 38. The slots are also preferably symmetrical with reference to a plane passed through the axis kof bore 42 perpenicular to the plane of the back portion 13 of housing 14. Where the positioning pin is equidistant fromy the slots, as just described, the axis thereof will coincide with this plane.

Spindle blade 12 is of generally elongated cylindrical configuration having an axial bore t) extending through the full length thereof for passage of the yarn, the mouth at the lower end ofthe bore being flared. Adjacent each end, the diameter of the blade is substantially reduced as compared to its normal diameter, the reduced end portions 52a, 52b serving as bearing surfaces or gudgeons for the spindle while the mid-portionV 54 functions as a Whorl. At the transition of the mid-portion to each endportion isa shoulder 56 tapering at an angle roughly complementary to the angle of the ared internal ends 44 of bores 42 in mounts 24.

When the false-twister unit of the invention is assembled, the spindle blade 12 is supported by housing 14 with the reduced end portions received within the mount bores 42 so that the spindle bore is concentric with the housing bores 22a and 22b. The lower end` 52b of the spindle blade terminates approximately flush with the lower of the external spacing washers 32 while the'upper end projects above the upper of these washers and retaining ring 30 to accommodate a yarnfengaging cap or head 60, preferably formed of wear-resistant material. This cap includes a downwardly opening socket 62 fitting over the free endof the blade, a transverse ange 64 at the' upper enduof the socket portion, and two segments 66 projectingdownwardly from diametrically opposed portions of the edge of the flange. A central axial aperture not shown is formed in cap 60. This aperture is, in `ef-l fect, a continuation of bore 50, having a diameter substantially the., same as that of bore 50. The edges of the aperture flange 64'and segments 66 are all rounded to' minimize wear and tear on the yarn. y

Reference has already been made to the presence'in each ofy the bearing mounts of two spaced radial recesses 46` withl metal plates` 48 in the bottoms thereof. These recesses are adapted to receive identical bearing segments 70 which are disposed in pairs in the bearing mount and constitute journals forthe reduced end portions of spindle blade 12. Segments 70 are formed of hard wear-resistant material, precious stones of natural or synthetic origin,

y 4f such a sapphire, being preferred, although highly wearresistant metal can be substituted where increased frequency of replacement is permissible.

For the purpose of the invention two adjacent sides 72 and 74 constitute planar bearing faces, receiving the bearing load. of the end portions 52a, 52h and tapered shoulders 74, intersects with the greater 72 at an obtuse angle approximately equal to that at which the ends of mounting bores 42 flare outwardly and complementary with the taper of shoulders 56. Side 76, opposite side 72, has a large convex radius of curvature and .is adapted to seat against the metal strip 48 in the bottom of recess 46. The

. curvature of this side permits the segment to align itself in the recess with its bearing faces in proper contact withl the corresponding surfaces of the spindle blade and avoids the necessity of forming the two opposite greater sides in exact parallel. i Due to its curvature, side 76 can have only theoretical line contact with any plane surface against which it abuts and the function of metal plate 48 is to receive the concentrated load from the curved rear face of the segment and distribute it over the bottom of the radial recess in the porous mount. Where the segment and mount can be modified such that the load receiving and transmitting surfaces thereof are closely parallel to the axis of the spindle and to each other, plate 48 may be dispensed with.

Opposite to the incl-ined end face 74 is side 7S extending generally perpendicular to the greater bearing face 72. When positioned in the bearing mount this side is generally coterminous with the outer tranverse end face of mount 24, as is readily apparent in FIGURE l. The segment is completed by the two remaining faces 80 and 82 which are substantially parallel to each other and substantially perpendicular to all other sides.l

The longitudinal and transverse dimensions of the seg-v ments are such that they are not Wholly received within the recesses 46 but rather have their greater hearing faces 72 extending chordally with respect to the mount bore 42. This insures that the bearing load is borne by the segments rather than the internal surface of the bore. The diameter of the mount bores is sufficiently greater than that of the reduced end portions 52a, 52h of the spindle .blade that a discernable clearance exists between the spindle surface and the surface of the bores. When the spindle is inactive, there is a small amount of lateral play n the spindle; however, rotational driving force, for instance of a belt 86, is transmitted to the spindle blade in such a way as to urge the spindle blade end portions into contact with the radial bearing faces 72 of the cooperating parts of the segments and away fromA the internal surface of mount bore 42. Similarly, the inclined bearing faces 74 are slightly raised above the flared end faces 44 of the porous mount.

From the foregoing descriptions, it willy have been comprehended that each cooperating pair of segments 70 define a combination' V-type radial and thrust hearing. The radial load is transmitted from the spindley through reduced end portions 52a, 52h, segments 5 70, and load distributing plates 48, vto bearing mounts 24 and thence to the housing block 14. The inclined'segment bearing faces .74 receive from the tapering spindle shoulders the axial thrust in either direction of the spindle and transmits the thrust through washers 32 and retaining ringsV 30 directly to the housing. .While the radial bearing faces 72 of each pair of segments are preferably Varranged at a right angle to each other, a different angle, except can beused in lieu thereof.

The extreme high yspeeds at whichV the spindle of the invention is to be rotated make 'the provision of va lubrication system desirable. if burned-Out parts are to be avoided.

Thefabove-described feature is accomplished in the.. present .invention by giving the generallyy cylindrical porous bearing mount access to a supply of lubricating oil in order that the mount become permeated by such oil. As can be seen from FIGURE 1, such access is obtained' by forming in the interior wall in each of the bores 22a, 22b an annular recess 90 extending into the housing legs 20a, 20b. Each of the annular recesses 90 'is in communication with an loil reservoir chamber 92, one of the chambers being formed adjacent the upper endof the back portion 18 of the housing block and the other adjacent the lower end thereof. Annular recesses 90, and preferably the reservoir chambers 92 as well, are lled by oil-absorbent felt, indicated at 94, the presence of the felt retarding the ow of oil through the sintered bearing mount and tending to prevent a condition of over. lubrication. Chambers 90 may be conveniently obtainedv by drilling into back portion 18 of lthe housing from the rear face thereof and pressing aplug 95 into the end of the opening. j Y

Any appropriate means may be provided for filling the oil reservoir chambers, such as a passageway 96 extending upwardly from the upper chamber tothe top face of housing block 14 and a passageway 98 extending'upwardly and outwardly from the lower `reservoir chamber to the back face of the block.

It is well known that yarn undergoing bodily rotationl tends to balloon outwardly due to centrifugal force, which may lead to yarn entanglement where a plurality of strands of yarn have closely adjacentv paths. Objectionable ballooning may be prevented by having suitable guide means restrain the yarn after passage around the yarn engaging head. It is advantageous from the standpoint of simplicity in assembling the false-twister spindle units of the invention into a machine for each unit to carry its own yarn guide which may take the form of a length of stiff wire 100 having a loop or pig-tail 102 at the upper end thereof in -axial alignment of the bore 50 of spindle 12 the lower end of the guide wire` being attached to the upper face of the housing block, as at 104.

Up to this point, the description of the invention has been confined to a single false-twister spindle unit existing in the abstract, so to speak, that is, independentof any particular combination of elements for mounting or supporting` the unitsl inan actual machine.` Thisfmode of description was adopted because of the facty that the unit is capable of being mounted in any one of several ways. One such way is illustrated in FIGURES 2 and 3 and is intended to be employed primarily when anew machine, ordinarily including a large number of units, is to be constructed. In this arrangement, the numeral 10S indicates a horizontal frame member of the twisting machine supported in the usual way by means not shown and o'n which a number of the false-twister spindle units are to be mounted. `At appropriatespaced points along the length of frame member`108, a swing. post 110 is xedly secured thereto, the lower, end of the post passring through an aperture provided in the member and threadedly engaging a nut 112. Nut 112 is opposed on the opposite side of member 108 by a collar l113 integral with post 110. Swing post 110 is surrounded'v over the major portion of its length by a sleeve 114 that is rotated freelyl on upper and lower bushings 116. Encircling sleeve 114 is a torsion spring 118.having one.of -its ends ixedly connected to ,they-sleeve andythefother held in engagement with a diametrical recess 120 formedV in the upper end of 4the post by means of an annular C-ring 122. A second C-ring 123 is spaced on vpost 110 inwardly of ring 122 to receive the thrust from sleeve 114 and prevent undue axial play inv the sleeve.` lThe post,

sleeve and spring may be enclosed by Ya cover 124 having `a `friction t with the base of ,the sleeve. 3

The false-twister spindle unit 10 is supported for pivotal movement about .the...swingpost on'a-swing-pl'ate 126. Adjacent one end of this plate is an aperture not visible intFIGURE 5, which is in press-tting engagement with the lower end of sleeve 114. A second aperture 128 (see FIGURE 1) is provided adjacent to the other end of the plate for the reception of an extension 130 projecting below the bottom leg of the housing block and having reduced dimensions as compared to the housing. TheV entire spindle and housing unit is held against vertical movement with respect to swing-plate 126 by means of a dished retaining ring 132 engaging at its inner end a circumferential recess in the extension and bearing at its outer end against the undersurface of swing plate 126. Upon removal of the retaining ring the unit may be lifted from the swing plate to facilitate repair and/ or replacement.

The primary function of the swing assembly is to support the spindle unit for pivotal movement toward and away from driving belt 86 adapted to engage the center whorl portion of spindle blade 12 to rotate the same. A fragment of such a belt is shown in FIGURE 2. When the machine is assembled, torsion spring 118 is pretensioned so as to urge the blade into contact with the driving belt, the tension being sufficient to prevent slippage between the belt and spindle. In order to facilitate disengagement of the spindle from the driving belt, utilization may be made of a disengaging lever 142. As can be seen in FIGURE 3, this lever is pivotally connected at one end to frame member 10S by means of a stud 144 and is formed at the other end with a handle 146 projectingy downwardly below the frame member. Intermediate the pivoted end and handle 146 is a turned-up ear 148 which is adapted to engage a down-turned ange at the rear edge of swing plate 126. .As the disengaging lever is moved clockwise in FIGURE 6, ear 148 engages flanges 150 to shift the unit slightly away'from the driving belt to an inoperative position shown in dotted lines. When pivoted to the full extent permitted by swing post 110, lever 142 is in an over-center position, shown in dotted lines, where it is urged by swing spring 118 through swing plate 126 against post 110. When lever 142 is in over-center position, unit 10 is maintained with the spindle whorl portionl out of contact with the driving belt even when the lever is released. Movement of the leverl It will be appreciated by those skilled in the .art that a plurality of` spindle and housing units and associated swing assemblies may be organized in the manner customary with twisting machines, that is in two parallel rows, one onY each side of the machine, with an endless driving belt located between the rows, driving all of the spindles in both rows, the belt, in turn, being driven from a high speed electric motor. This arrangement, however, presents certain difficulties from a practical point of view.v 'While the torque requirement of an individual unit is quite low compared to a conventional twister spindle, the totalor aggregate requirement for a large number of units, say 100, is fairly high.

If theIspindles were to be driven directly from a single belt at the speeds contemplated, the linear rate of travel yof the beltV would be higher than can be tolerated with it has not been possible to findl a large, heavy belt from` among those presently commerciallyv available that will operate satisfactorily.

For this reason, although the construction` of'a ina-v chineY embodying the spindle units of the invention along conventional ylines is not considered completely Voutside the realm of possibility, a modification of the conventional drive to meet the peculiar needs of the invention is con-r sidered preferable. One modification that'has'been found satisfactory is shown in FIGURES 4 and 5, it being understood that the'illustration is quite diagrammatic in nature and omits all mechanical details. In this gure,

the numeral 152 designates a primary driving belt which l is of the heavy durable type normally used in twisting machines, and is arranged in the normal fashion, i.e., in an elongated endless loop with large diameter pulleys 154 at each end of the loop. One of the pulleys is driven by an electric motor, not shown, while the other functions as an idler. There is disposed along each of the two straight stretches of the loop a plurality of pulleys 156. Contacts between the main belt and all of pulleys 156 is insured by means of small idlers 157 engaging the opposite side of belt 152, there being one such idler between each pair of pulleys 156.

Pulleys 156 are of the compound type, having a large diameter portion 158 and a small diameter portion 160, the primary driving belt having driving contact with the small diameter portion. The large diameter portionV of the pulleys is in driving contact with a high-speed secondary driving belt 162. Preferably, more than one of the secondary belts is used, each having a path in the shape of an elongated endless loop and encompassing a plurality or group of the compound pulleys on one side of main belt 152. The end or terminal pulleys of the group are in contact with the secondary belt through an arcv of roughly 180 while the remaining intermediate pulleys have opposite sides in tangential contact with the belt. In the illustrated arrangement, only one plurality or group of compound pulleys and associated secondary driving belts is shown on each side' of the main driving belt, but it will be appreciated that a number or these groups can be utilized. Also, the number of pulleys in each group may vary from that specifically illustrated. The compound pulleys in each group are spaced at intervals along the straight stretch of the main driving belt so that the secondary belt upon leaving one pulley is unsupported for a distance before contacting another pulley. Between each pair of adjacent pulleys 156, a group of the spindle units 1G, of the invention are arranged in a straight line adjacent the unsupported stretch of the secondary belt so that when in operative position the whorl portions of the spindle are in driving Contact with the belt. The number of spindles between the pairs of pulleys and contacting a single unsupported stretch of the secondary belt may, naturally, be varied.

This spindle driving arrangement has characteristics. particularly desirable for high speed spindles. The ymain belt has no direct contact with the spindle blades; the factfthat this belt may not run smoothly is, therefore, immaterial." A large heavy main belt, capable of transmitting the total power required for all units, can, hence, be

utilized without deleteriously affecting the performance of the machine. The maximum tension in secondary driving belt 162 need be only sucient to transmit the power being consumed by the group of spindle units 1t) mounted between an adjacent pair of pulleys 156 as it is given fresh driving impetus by a pulley 156 before encountering the next group of units. Therefore, spindle driving belt 162 can be thin, flexible and readily capable of high speed travel. only a small pressure against the spindle whorl in a normal direction to impart rotation to the spindle blade. Operation of the machine with light belt pressure results in the further advantage of light, loading of the spindle bearings.

In brief, the organization illustrated in FIGURES 4 and 5 divides the drive into a low-speed, high-load stage and a high-speed, low-load stage, and the load transmitting elementsfor each stage can be selected to meet the particular requirements of that stage and need not be expected to function over an almost impossible range of conditions. It will be understood that in this organization the spindle units shown diagrammatically and indicated by the nup package, not shown, and passed through the spindle bore Such a thin, flexible, low-tension belt requires- 50, drawing the yarn throughy the bore and opening 68 in cap 60. The strand of yarn is then wrapped around and underange 64 so that when threaded through yarn guide 102 it is retained beneath the down-turned lip 66. Next, the strand is attached to any suitable yarn take-up mechanism,.not shown. By means of the cooperating ball and socket the position of housing may be adjusted relative to plate 126 until the pairs of bearing segments 70 are disposed symmetrically about a plane passed through the spindle blade axis perpendicular to the spindle driving belt. Segments 711 are,of course, on the opposite side of the spindle blade from the belt. Alternatively, the housing may be positioned so that the radial bearing face of one segment of each pair is parallel to the belt while the same face of the other segment is normal to the belt on the side of the spindle in the direction of travel of the belt. When the strand is properly threaded, lever 142 is then pivoted .away from post whereupon spring 118 pivots swing plate 126 about post 110 until whorl portion 54 of the spindle blade contacts the driving belt.

For this reason, the form of the invention illustrated herein should be considered as exemplary only, the scope of the invention being defined by the hereunto appended claims rather than by what is specifically illustrated and described. v

What is claimed is: l

1. In a machine for false twisting a strand of yarn, in

combination,

two main pulleys at laterally spaced points,

means for rotating at least one of said pulleys,

a thick, relatively rigid main driving belt encircling said two main pulleys in an elongated endless path having two straight stretches,

a series of compound pulleys disposed at spaced points along at least one stretch of one path of said main belt,

each of said compound pulleys having a` large diameter surface and a small diameter surface, the latter being in driving contact withV one side of said main belt, v

a single thin, relatively flexible secondary driving belt driven by the large diameter surfaces of said v compound pulleys along said stretch, and v a plurality of lfalse twister spindles arranged between each pair of` compound pulleys in said series in driving Contact with said secondary driv-d References Cited in the'file of this patent UNITED STATES PATENTS Brown Aug. l0, 1915 Hilbert et al. 1-1. May 7, 1957 Trapido et al Sept. 24, 1957

Claims (1)

1. IN A MACHINE FOR FALSE TWISTING A STRAND OF YARN, IN COMBINATION, TWO MAIN PULLEYS AT LATERALLY SPACED POINTS, MEANS FOR ROTATING AT LEAST ONE OF SAID PULLEYS, A THICK, RELATIVELY RIGID MAIN DRIVING BELT ENCIRCLING SAID TWO MAIN PULLEYS IN AN ELONGATED ENDLESS PATH HAVING TWO STRAIGHT STRETCHES, A SERIES OF COMPOUND PULLEYS DISPOSED AT SPACED POINTS ALONG AT LEAST ONE STRETCH OF ONE PATH OF SAID MAIN BELT, EACH OF SAID COMPOUND PULLEYS HAVING A LARGE DIAMETER SURFACE AND A SMALL DIAMETER SURFACE, THE LATTER BEING IN DRIVING CONTACT WITH ONE SIDE OF SAID MAIN BELT, A SINGLE THIN, RELATIVELY FLEXIBLE SECONDARY DRIVING BELT DRIVEN BY THE LARGE DIAMETER SURFACES OF SAID COMPOUND PULLEYS ALONG SAID STRETCH, AND A PLURALITY OF FALSE TWISTER SPINDLES ARRANGED BETWEEN EACH PAIR OF COMPOUND PULLEYS IN SAID SERIES IN DRIVING CONTACT WITH SAID SECONDARY DRIVING BELT.

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