CA1052348A - Method and apparatus for automatic bobbin exchange - Google Patents

Abstract

Abstract of the Disclosure The invention relates to an apparatus for automatic and successive exchange of a plurality of bobbins. This apparatus includes a bobbin holder having a plurality of radially extending arms adapted for removably supporting the bobbins in one-to-one relationship. It includes further a pair of bearing means for support of an axial shaft of the bobbin holder and at least two parallel mounting rods adapted for slidably supporting these bearing means. There is provided further a pressurizing means for pressing the bobbin towards a friction drive roll and a stepwise rotary feed mechanism placed at one end of shaft of the bobbin holder. A larger diameter head member is connected with the friction drive roll so the head member's rotation is in synchronization with the rotation of the drive wheel. The connection is through an angularly displaceable doughnut ring with the drive roll.

Description

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Background of the Invention This invention relates to improvements in a process for the automatic exchange of bobbins during windlng of a yarn, preferabl~ a yarn of Spandex, and it relates fur-ther to an apparatus adapted for carrying out said process. Such an apparatus is known as an auto-doffer among those skilled in the art.
Although the invention is not limited to the exclusive use o~ elastic yarns, of which Spandex is preferably the following description will be made with the use of elastic yarns because the invention can be most favorably adapted in the manufacture of such treatment-sensitive kinds of yarns.
In the exchange operatlon of fully wound bobbins on yarn winding machines which are used in the wet-, melt- and dry spinning processes of elastic yarns, a conventional technique has developed.
This techni~ue individually removes a fully wound bobbin, preferably consistina of a paper tube, and positions a new bobbin on the holder. But the initiation o~ the conventional winding occurs only a-Eter cutting the continuously supplied yarn and introducing the end of the yarn into a suction gun on winding the end a.round a roll.
The result is the accumulation of a large amount of waste ~arn. Therefore, yarn production and packaging costs rise.
In the case of the elastic yarns as compared with o~her kinds of yarns, the winding yarn quantity must be considerably reduced mainly for technical reasonsl and therefore, the bobbin exchange frequency must be increased despite obvious uneconomical and lnefficien-t operational results.

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~OS~34l3 Even if the bobbin exchange jobs are carried out exclusi~ely or subs~an-tial~y manually, unwieldy operation is invited by virtue of the difficulty in handling elastic yarns.
For these reasons, the bobhin exchange job, including manual operations for exchanying bobbins are highly ~roublesome and inefEicient.
Various and numerous improvements have been proposed and executed in the auto-doffering of bobbins if the yarns are other than elastic yarns. However, in the case of polyurethane elastic yarns, the auto-doffer appliances could not be used per se, on account of the rubber-like elastic nature of such modern yarns.
Even if conventional yarn cutters are used in the yarn-cut jobs during the bobbin exchange, reliable cutting could not be achieved, because these elastic yarns are highly extendable and ! elastic. Threading and unthreading o these elastic yarns through individual traversing members were also very highly troublesome because of the elastic extension of these yarns.
Specifically designed various means for an automatic yarn cutter and/or auxiliary means for assisting in the yarn catch by the bobbin must be provided for the automatic bobbin exchange machineries to provide a solution to the lony-felt problems of the prior art.
Summary of the Invention It is therefore an object of the present invention to provide an efficient and improved techni~ue for the achievement of an automatic bobbin exchange technique, without producin~ a significant amount of waste yarn, even if elastic ~arns are used.

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Other objects, features and advantages of the present invention will become more apparent when the following detailed description of the invention is read in consultation with the accompanying drawings which substantially illustrate an embodlment of the invention.
Brief Description of the Drawings -In the drawings:
Fig. 1 is a side elevation of essential parts of an inventive bobbin exchanger.
Fig. 2 is an enlarged perspective view of a friction drive roll, a drive and an operation control of t~e latter and a bobbin under cooperation with said drive roll, as main constituents of said exchanger machine.
Fig, 3 is a plan view of the machine shown in Fig. 1.
Fig. 4 is a sectional front view of an intermediate coupling ring member through which, drive is transmitted from the friction drive roll to head portion thereo~.
Fig. 5 is a sectional plan view of essential parts shown in Figv 1.
Fig. 6 is a substantially sectional view of an embodiment of an eccentric doughnut ring and an operating arm thereo made integral therewith.
Fig. 7 is a front view thereof.
Fig. 8 is a side view of a pneumatic piston-and-cylinder unit adapted for operational control of the eccentric doughnut ring shown specifically in Figs. 6 and 7.
Fig. 9 is a front view of a ratchet plate attached to a bobbin holder employed.

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Fig. 10 is a timing schedule chart oE four difEerent pneumatic piston-cylinder units employed in the machine.
Fig. 11 is an enlarged view of a part of Fig. 5.
Figs. 12 and 13 are two schematic explanatory views of the cooperation of friction drive roll r doughnut ring and bobbin.
Detailed Description of the Invention Referring no~ to the accompanying drawings, a preferred embodiment of the invention will be described in detail.
In Fig. 1, numeral 1 represents a radial arm type, bobbin holder, having a plurality, (four in the present embodiment~, of arms la, lb, lc and ld, the root ends of the latter being made integral with a center boss 6. These radial arms mount respective bobhins 2, 3, 4 and 5 at their ou-ter ends in an easily detachable - manner, as will be later more fully described.
The bobbin 2 is shown in Fig. 1 in its engaging position with a friction drive roll 51 which is shown only schematically and in its position on account of its conventionally known design.
Each of the radial arms la, 1~, lc and ld represents a channel configuration when seen in its front or sectional configuration as shown in Fig. 5.
As most clearly seen from Fig. 5, the boss 6 is practically a sleeve which is rigidly coupled by means of a key 7 with a shaft 8 which is rotatably moun-ted in a pair of separated front and rear ' antifriction bearing units 9 and 10.
Non-rotatable part 9a of the front bearing unit 9 is slidably supported through a bearing sleeve 1~ on a horizontally extending rod member 11 of a framework 15. Non-rota-table part lOa y~ 4 -34~3 of the rear bearing unit 10 is slidably mounted throuyh mounting sleeves 18 and 19 on a pair of mutually parallel rod members 13 and 1~ o~ sald framework 15, these members 13 and 14 being also parallel to the foregoing rod member 11. The plurality of parallel rod members acts to slidably support the bearing means. If necessary, however, these two rod members 13 and 1~ may be replaced by a single rod. In ~ig. 5, the oppositely arran~ed bobbins 2 and are shown on the radial arms la and lc which are positioned vertically in Fig. 1.
During the bobbin exchange operation, a certain idle gap must be kept between the friction drive roll and a new empty bobbin, so as to avoid otherwise possible yarn catch by the drive roll. Such a procedure is rather` conventional. It should be noted, however, the basic properties of the yarn part (as - wound on the new bobbin after initiation of the winding action thereon and until the yarn part will have filled the said idle gap so that the bobbin will carry out its yarn winding operation at ; its normal operational speed by direct contact with the drive roll) are dif~erent from those of the further yarn part which will be wound further on the bobbin; and therefore, the initial yarn part must be removed from a completely wound-up bobbin, so as to ensure an equal quality o~ the whole yarn mass regardless of specific outer or inner yarn layers. This yarn part's removal from the completely wound-up yarn package or bobbin has caused much trouble in the yarn packaying operation. One of the main features of the present invention resides in the novel technique in which the necessary idle gap is formed between a new bobbin and the drive roll during the yarn e~chanye period. ~Ihile the yarn windiny ! ~ ~i ywl/ 5 ;,. ~, ~ C)5'~3~3 speed i5 substantially accelerated subseauent to the completion of the yarn exchange operation, the said idle gap is caused to disappear and at the same time the bobbin is caused to recover its normal yarn winding speed.
Referring now to Fig. 2, the mechanism employed ~or the above~purpose will be described in detail.
The friction drive roll is shown again at 51 r yet in a more specific way. This roll 51 is continuously ~riven at a certain constant rotational speed. The new bobbin is shown at 2 as before.
Numeral 100 represents only schematically the yarn which is fed from a conventional yarn suppl~ source, not shown. ~ double headed arrow 101 indicates the reciprocations of a conventional traverse guide 103 which is shown only schematically. This yuide is positioned in proximity to said drive roll 51 which has an enlarged head or shoulder 52.
In Fig. 3, numeral 53 represents an eccentric dou~hnut ring, made o~, preerably, rubber or soft synthetic resin material, aaa~ted for cooperation with the enlarged head portion 52 of the drive roll. A unique cooperation mode between these two members 52 and 53, to be described, provides an important feature of the invention.
Referring to Fig. 2, when the drive roll head 52 is brought into contact with a rubber end portion 58 of bobbin 2, an engaging relationship between drive roll 51 and the bohbin 2 will be established, which drives the bobbin at its surface speed at at least 50% of the speed of the drive roll 51 by virtue of a substantial difference between the respective diameters. The rotational center of the enlarged head 52 and ihat of the drive ywl/ - 6 ~

~5'~3~L8 roll proper 51 is ~ept sligh-tly eccentric, as will be described later more in detail.
Numeral 7~ represen-tsa provisionally fixed and manually rotatable sleeve and the said doughnut ring 53 is mounted on the cylindrical outer surface of said sleeve 74, the head portion 52 being in practice and more specifically a separate me~ber which is mounted through antifrictional bearing means 27 on the cylindrical surfac~ of the ring 53 (refer to also Flg. 5).
A line shaft 55 is rotatably mounted by bearing means to be described within the sleeve 74, so as to transmit driving tor~ue to the friction drive roll 51.
Numeral 102 denotes a driver for driving the line shaft 55 and comprises a pair of mutually meshing mating gears S6a and 56b. The latter gear 56b is ~echanically connected to a prime mover, preferably an electric motor, not shown, and is driven therefrom.
Bobbin end portion 58, made preferably of rubber or the like resilient material, as was already referred to herein-before, constitutes a reduced cylinder and is adapted for cooperation with the outer periphery of the drive roll head 52, as was referred to.
Numeral 59 represents, schematically a double-acting fluid piston-cylinder assembl~ to be operated by introduction of compressed air although inlet and outlet openings and conduits therefor have been o~itted from the drawin~ for simplicity of the drawing. The piston, no-t shown, of the assembly 59 is mechanically connected with a piston rod 59a which is lin~ed at its forward end with the tip end oE an operating arm 60, the root end of the ywl/ 7 ~5'~34~
latter being made integral with the said riny 53. As shown in Fig. 2, the operating angular range of said operating arm 60 is represented by 0 which ma~ preferably be 9~ deyrees. When the piston occupies its retrac-ted position within the cylinder, the arm is kept at its full line position. With the piston occupying its advanced position, the arm will be at its chain-dotted line position 60'.
The torque transmission to the head portion 52 is made through friction drive roll 51. However, since the head portion 52 throuyh antifriction bearing means 80 and the rotational axes of roll 51 and head portion 52 are offset from each other by a certain small definite distance l'e", the necessary coupling means provided between them must have a special design, as will be described below.
! - More specifically, head por-tion 52 has a number of parallel and concentric longitudinaI coupling pins 64 as most clearly seen from Figs. 4 and 5. In Fig. 5, however, these coupling pins 64 are represented b~ only one pin. These pins are kept in engagement by a corresponding number of reception recesses 63a which are formed in the outer peripheral surface o a COUpling ring 63 made of a resilient plastic, thus the both members 52 and 63 are rotatable in synchronization with each other.
Second series of reception recesses 63b are formed periodically in the inner peripheral surface of the same ring 63 for reception of a second series of concentrically arranged, longitudinally extending coupling pins 62 which are fixed to the friction drive roll 51. Therefore, it will be seen that the both y~

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34~3 members 51 and 63 are adapted for rotation in synchronization with each other.
The rotational center of the first coupling pins 62 is shown at 62' in Figs. 3 and 4, while that of the second coupling pins 64 is shown at 64', the offse-t dis-tance being "e" as shown.
The driver 102 includes more specifically a drive shaft 70 which is attached rigidly to the gear 56b by a key 70a, as shown in Fig. 5.
The drive shaft 70 is rotatably mounted in a pair of antifriction bearings 71a; 71b which are separated a certain definite distance from each other by means of a separator sleeve 72, said bearing being positioned within a socket like projection 104a of machine frame 104. The outer end of the drive shaft 70 is connected with a prime mover, as was indicated only brie~ly here-inbefore. A laxge and outer sleeve 73 and a smaller and inner sleeve 74 are coupled rigidly to each other by press fit or other conventional fixing technique and rigidly mounted in the said machine frame 104, althouah the mounting means have been omitted for simplicity. The line shaft 55 is rotatably mounted more specifically by means of a pair of bearings 75a and 75b which are positioned in the smaller and larqer sleeves 74 and 73, respectively.
Friction drive roll 51 is fixedly attached to the line shaft 55, more specifically by means of a key 76 shown in Fig. 5, for synchronized rotation. The operation arm 60 is shown in Figs.

2, 3 and 5, and a modified shape of the arm is shown at 60" in Figs. 6 - 7. In Fiy. 8, the arm is shown as having been modified, but denoted with former reference characters 60 and 60'.
Nex-t, referring to Figs. 12 and 13, the workiny cooperation be-tween the drive roll 51 and the bobbin 2 will he _ g _ ywl/

3~8 described. Fig. 12 illustrates -the normal working condition while Fig. 13 illus-trates the operating condition when a new empty bobbin has been.brought to position.. In these Figures, however, the working angle of operating arm 60 or 60" of the doughnut ring 53, not shown in these Figures, is assumed to be 180 for clearer illustration of the invention although such a large operating angle is impractical.
In the normal working condition, the head portion 52 of drive roll 51 rotates in the direc-tion shown by a small arrow 105. The head portion 52 rotates through bearing means 80 around doughnut ring 53 which is kept stationary during normal yarn winding operation shown in Fig. 12~ The center "i" of the doughnut ring is offset from the center "c" of the drive roll 51.
- During the normal yarn wind-up operation, drive roll 51 is kept in pressurized rolliny contact with the bobbin 2, yarn 100 is wound on the bobbin 2 in the transfer mode, and the head portion 52 is kept in separation from rubber bobbin end 58 with a certain predetermined idle gap ~ shown in Fig. 12. The drive roll and the bobbin have a common surface speed.
When this bobbin 2 reaches its fully wound state with part of the yarn 100, it is carried away from this position and the superseding bobbin 3 is brought to this position so as to be synchronized wi-th the drive roll. Then, this roll must be accele-rate~ to a substantially higher speed to accomplish reliable ~linding operation of the now slackened part of the yarn 100. At this stage, the doughnut ring is rotated 180 in the present i~ealized condition around its offset center "c", thereby the rotational center of head portion 52 shifti.ng relatively from "i" to "i "' as . ywl/- - 10 -, .,~ . -3~13 shown in Fig. 3. In this way, the head portion 52 is brought into contact with rubber bobbin end 58, and the bobb;n is driven at a substantially increased speed relative to the normal yarn which is wound, while the drive roll and bobbin 3 are separated from each other.
In the operation of the machine/ torque is transmitted from the prime mover through successive members 70; 56b; 56a; 55;
51; 62; 63 and ~4 to head portion 52.
It is now assumed that a fully wound-up bobbin 2 has been carried along from position and a new empty one 3 is brought to position to synchronize with the friction drive roll 51 as shown by way of example in Fig. 3. Then, the corresponding resilient end portion as at S8 of the new ~obbin 3 will occupy a slightly lower position than drive roll 51, thereby an idle gap ~ is formed and maintained in Fig. 3, while the head portion 52 having a lar~er diameter is kept in enga~ement with bobbin end 58 having a smaller diameter. In this way and at this operational stage, the bobbln 3 is driven at a higher rotational speed than usual with an increase of at least 50%, so as to pick up the now slackened yarn 100 which is supplied through the horizon-tally reciprocating traverse 103 by the new bobbin 3 in a definite and positive manner.
At this stage, the pi,ston of compressed air cylinder 59, and its piston rod 59a, occupies its re-tracted position corresponding to their full line position in Fig. 2 and to their chain-dotted line position shown in Fig. 8, respectively. In this way, the problem of yarn catch by the friction drive roll can be avoided in a highly simplified way and without use of specially provided complicated means.

y ~1 1 ~ ' 1 1 3~8 When the slac~ened yarn part of the constantly fed yarn has been wound up substantially completely, compressed air is introduced into the cylinder 59, so as to advance the piston together with its rod 59a to the full line position thereo from its former retracted imaginary line posi-tion 60' in Fig. 8.
Although the operating angle of operating arm 60 is shown as about 60 in Fig. 8, this may vary to a lesser or larger degree, dependlng upon the degree of eccentricity of the doughnut ring 53.
When piston rod 59a is brought in this way to its full line position in Fig. 8, the head portion 52 of roll 51 will be shifted to its chain-dotted line position 52' in Fig. 3, the hitherto mutually contacting parts 58 and 52' are separated from each other, while bobbin 3 and roll 51 are bxought to their normally synchronizing and mutually contacting po~ition~ The i result is that the bobbin is restored to its regular operating condition rotating at its normally winding speed, until it will attain its fuily wound state.
; The friction drive~roll 51 may have normally a diameter just or substantially the same as that of the bobbin, or alternat-ively, it may have a still larger diameter, as large as about three times the bobbin diameter. The cylindrical surface o roll 51 may preferably be finished by polishing or galvanized with a hard chromium coating. Line shaft 55 is rotatably mounted by means of bearings 75b and 75a.
As shown in Fig. 1, a suspension wire or rope 25 extends horiæontally from bobbin holder 1 and through a guide 26 rigidly attached to machine frame 15 downwardly. To the forward end of the rope 25, a mass of weight 27 is attached fixedly. By the provision ywl/ - 12 -, s. ~l 5 05~3~
of this weight suspension unit, it will be noted that the bobbin holder 1 is always subjected to a mechanical pull acting in the rightward direction seen in Fig. 1, therehy the bobbin which has been brought to its operating position during bobbin exchange period being kept in its proper pressure contact with the friction drive roll through the intermediary of the bobbin holder.
It should be noted, however, in accordance ~lith our practical experience, that during the bobbin exchange operation, slip may occur occasionally between the resilient end 58 of a new bobhin and the head portion 52 with use of such gravity pressure system. In such case, the yarn lO0 may represent excess slackening 'n the yarn part extending between the departing fully wound bobbin and the new one and in pursuit oE the attainment of the desired rapid bobbin acceleration to at least a 50%-increase from the regular winding speed, the result i5 frequently an entanglement of the yarn around the drive roll 51.
In order to avoid such a problem, the related cooperating parts 52 and 58 must be pressed against e~ch other with a substantially accentuated pressure relative to the usual pressure appearing in the normal yarn winding period. The increased pressure may be two to th ee times greater than the usual pressure, and must be applied directly after completion of each stepwise feeding step necessary for a bobbin exchange operation by steppingly rotating the bobbin holder l, so as to suppress the said kind of slip .
For this purpose, a further fluid-opera-ted piston-and-cylinder unit 28/ preferably operable with compressed air, is fixedly attached to machine frame 15, so as to exert pressure on =~! ywl/ -- 13 --~.~

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the cooperating parts 52 and 58, pushing them against each other.
This unit 28 has a movable piston rod 28a which is shown at its retracted position in Fig. 1 by dotted lines.
When it is required, the unit 28 is activated with pressure fluid, so as to advance the rod 28a rightwards to exert a substantial internal pressure against the bobbin holder 1. At each time when the stepwise rotational feed of the bobbin holder has been completed and the yarn chan~e-over operation has also been fully and satisfactorily executed, the unit 28 is instantly deactivated by retracting the piston with its rod 28a, releasing the bobbin holder from the application of lateral pressure. For simplicity, inlet and outlet and their related conduit means have been omitted from the dra~Ting, since the necessary dual purpose structure is very well known to thbse skilled in the artO
- There is provided a still further fluid-operated piston-cylinder unit 29 of the dual purpose type for stepping rotational feed of the bobbin holder 1 which is pivotably moun-ted on a slide 10 and having a movable piston rod 29a linked at its forward end with an arm 31a extending from a ratchet plate 31 arranged 20 concentrically with the bobbin holder 1, as shown most clearly in Fig. 9. This ratchet plate 31 is further provided with a second arm 31b arranged diametrally opposite to the said first arm 31a.
At the forward end of the second arm, a ratchet pawl 32 is pivotably attacned. A brake element 34 is so arranged to cooperate with the boss of ratchet plate 31, a coil spring 33 being provided so as to urge the brake element to exert a brake pressure ayainst the said ratchet plate boss.
When pressurized fluid is properly supplied to the ~ ~ y~1/ ~ 14 ~1:)5'~8 cylinder unit ~9, which is shown at its contracted position in Fig. 1, its piston, not shown, will advance together with its rod 29a. In this way, the latter will advance in rightwards and Upwards in Figs. 1 and 9, thereby the ratchet pawl 32 kept in engagement with one of notches 31a formed on the periphery surface of ratchet plate 31 arranged concentrically with bobbin holder 1 pushing forcibly the plate, so as to execute one step ro-tary feed of the bobbin holder in counter clockwise direction for an angle of 90 in this embodiment. In this way, a new bobbin as at 3 is brought into its operational position where the preceding and fully wound bobbin 2 was situated and then is brought to its one-step advanced position at 5 adapted or being removed from the bobbin holder. The new bobbin 2 is brought into pressure engagement, with drive roll 51. When this operation has been completed, pressure fluid supply mode to the cylinder 29 is reversed, so as to recede the piston rod 29a. Although not shown, bob~in holder 1 and ratchet plate 31 are joined together, so as to constitute a unified member adapted for executing a unitary motion.
A still further fluid-operated piston-cylinder unit 36 of the dual purpose type is mounted on a slidable plate, not shown, which is mounted in turn on the machine frame 15, said unit having a piston rod 36a. This piston rod is provided with an enlarged head 37 acting as a positioner adapted for cooperation with any one of a series of radially arranged receiving recesses as at 37a, on the periphery of said ratchet plate 31. In practice and more specifically, this plate 31 has been made into a douhle-plate structure, as most clearly be seen from Fig. 9. When the ~ositioner 37 is advanced, it is brought into one of said recesses ywl/ - 15 -sp 3~
37a, in order to ~ix the position of the plate 31. On the other hand, when the positioner has been receded from its operating position in engagement with said recess, the plate 31 is unlocked for its free rotation.
In the following, the operation of the machine so ~ar shown and described will be set ~orth in detail.
It is assumed that the yarn 100 was threaded from a constant delivery supply source, not shown, through the traverse 103 and drive roll 51 to th~ bobbin 2, and indeed, in the transfer mode so called, as ~ost clearly illustrated in Fig. 2 and that the bobbin 2 has attained at its fully wound condition. Such ully wound state of a bohbin can be sensed by auto~atically urging electrically a timer on upon lapse of a certain predetermined time period, such as 30 minutes counted from initiation of yarn winding - of the same bobbin. ~f necessary, however, a co~bination o~ a feeler adapted for sensing the yarn wound state o~ a bobbin, with a microswitch arranged to be on-off controlled by the ~eeler, could be utilized.
~en the said timer turns on, the cylinder unit 36 is energized 50 as to recede the positioner 37 from position, thereby other cylinder 29 being actuated by actuation of a limit switch not shown, as shown in Fig. 10 illustrative of a ti~ing schedule chart. When the cylinder 29 is thus activated, bobbin holder l is caused to execute one step rotary feed in counter clockwise direction in Fig. l and thus, the ~ully wound bobbin 2 is brought into its of~-position at 5, while, at the same time a new bobbin 3 is brought to its working position in place of the foregoing bobbin 2. During a predeter~ined short time period such as 0.3 ywl/ - 16 -~os~
second as sho~ln in the timing schedule char-t, the new bobbin 3 is kept in its present state.
BeEore the elapse of this time period of 0.3 second, a further timer which is not shown is turned on, and the positioning cylinder 36 is actuated in its expanding stroke so that the positioner 37 may be advanced into engagement wi-th one of recesses 31c for Iocking the ratchet plate 31 and bobbin holder 1 at its newly divided position. Upon lapse of said time limit of 0.3 second, a still ~ur-~her timer, not shown, is caused to go on and the initial pressurizing cylinder 28 is caused to ini~iate its advancing stroke and further cvlinders 29 and 36 are caused to initia~e their respective return strokes so as to recede their piston rods 29a and 36a, thereby the pawl 32 being disengaged ~rom one o~ notches 31c. At the same time, the positioner 37 will receae from its engaging position with one of the recesses 37a, thereb~ ratchet plate 31 and bobbin holder being freed, whereupon the contacting position between new bobbin 3 and friction drive roll 51 is maintained under the action of gravity weight mass 27.
With the same timing as that for the initial pressurizing cylinder, the cylinder unit 59 for driving of the eccentric doughnut is actuated, and the rubber bobbin end 58 and head portion 52 are brought into mutual contact with each other, thereby a small idle gap ~ being established maintained between the drlve roll and the new bobbin. In this way, bobbin 3 is rotated in a substantially accelerated way with an increased speed higher at least 50~ than the usual yarn winding speed. At this operational stage, the receded full-wound~bobbin 5 continues its winding operation ~or ~ur-ther take-up o~ yarn 100, however, with gradually decreasing 34~
speed. Thus, the yarn which is being fed always at a predetermined constant speed regardless of the bobbin exchange operation will become slackened as extending between the receded full-wound bobbin and the new bobbin which has been brought to its newly yarn-winding position cooperative with the friction drive roll.
By the actuation of initial pressurizing cylinder 28, bob~in holder 1 is subjected to a rightwardly acting pressure when seen in Fig. 1 and thus, the mutually contacting pressure between new bobbin 3 and head portion 52 is suhstantially increased. Now, the slackened yarn portion is wound on the new bobhin 3, the rotat-ional speed of which is greatly, though temporarily,increased.
Then, the yarn will strongly be pulled between these two bobbins 2 and 3 until it is finally severed.
Immediately subseauent to the intentional severing of the yarn the piston and its rod of the cylinder unit 59 will return to their receded position representatively illustrated by the full line position of the piston rod in ~ia. 2. In this way, the rubber end of new bobbin 3 and the head portion are disengaged from each other, while the drive roll and the new bobbin are brought into mutual contact with each other. Then, -the initial ~ressurizing cylinder 28 is brought to its receded piston position, thereby initiating usual yarn winding at the normal winding speed.
~ Jith this improved s-tructural arrangement and its uniaue operational mode, an auto-dofing operation can be done in a highly simplified manner without the production o-f uneconomical and troublesome waste yarn as is necessarily encountered with the conventional comparative bobbin exchange system.
As represented in the foreqoing descrip-tion, the notches ywl/ - 18 ~

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adapted for cooperation with the ratche-t pawl 32 and the recesses adapted for cooperative engagement with the positioner 37 must have the same operational phase; these no-tches and recesses may preferably be made so they axe separated from each other as was shown and described.
In the foregoing description, the yarn threading ~ode was of the transfer mode. But, when necessary, the yarn may be introduced into the co-engaging zone as provided between the bobbin and friction drive roll, so as to execute the normal threading mode. In this case, however, the stepwise rotational feed of the bobbin holder should be reversed in its operational direction or clockwise direction as shown in Fig. 1.
In addition, the machine may be designed in such way that the posi-tloner 37, acting as a kind of a stop means may be caused to disengage from its mating recess 37a when each bobbin has attained its fully wound position.
To avoid the occurrence of a mechanical shock when the positioner 37 engages its notch 37a to stop any rotational movement of ratchet plate 31 and bobbin holder 1 by locking the plate and the holder in position, the brake element 34 should preferably be actuated directly before the lockinc~ operation.
In the following paragraphs, a practical numerical example will be given to promote a clear understanding of the yarn change-over operation.
Example A conventionally used Spandex spinning liquor, viscosity:
2,500 p, was spun in the dry spinning process by use of dimethyl formaldehyde as solvent, into a 40-denier yarn at a spinning speed of 500 m/min. At -t'ne yarn winding zone, a machine of the ty e i" ~

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shown and described in the foregoing paragraphs. Yarn change-over operations were carried out so as to determine the likelihoocl of a satisfactory yarn catch by a new empty bobbin kept at posltion, and by transfer of the yarn from a fully wound bobbin. The likelihood was measured upon completion oi a thousand tests for each specifically selected test conditlon.
The friction drive roll was usecl in the form of a conven-tional paper tube, having an outer diameter of 80 mm.
The minor idle gap ~ was set to 0.5 mm between the friction drive roll and a new bobbin substituted by each bobbin exchange operation. The operation of each of several main working parts of the machine was synchronized with that which is listed in the timing schedule chart shown in Fi~. 10. Five kinds of outer diameter ratio between the head portion 52 and rubber bobbin end 58 were set to 1.2; 1.3; 1.4; 1.5 and 1.75, respectively, and the ; following results were obtained. The employment of the above ive various ratios means that the winding speed during each bobbin exchange was increased by 20~; 30%; 40%; 50~ and 75%, respectively, relative to the normal winding speed.
Results Rate of acceleration 20~ 30% 40% 50% 75%
Percentage of success of yarn change-over, %
The less than perfect percentages of success were caused in each case by yarn catch by the friction drive roll.
It will be seen from the foregoing paragraph that the objects of this invention could be achieved by increasing the yarn winding speed during bobbin exchange by at least 50% in comparison with the normal yarn winding speed.
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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for automatically exchanging a plurality of bobbins, one after another in such a way that when each bobbin of said bobbins is fully wound with a yarn, a succeeding empty bobbin is exchanged for the said fully wound bobbin, comprising the steps of:
a) removing a fully wound bobbin, b) fitting said empty bobbin in a service position for synchronization with a friction drive roll, c) forming an idle gap between the friction drive roll and said empty bobbin, d) contacting a head portion of said friction drive roll with an end portion of said empty bobbin, wherein said head portion has a larger diameter than the remaining portion, whereby the empty bobbin's rotational speed is increased in excess of usual yarn winding speed because of a difference between the diameter of said drive roll and the diameter of said empty bobbin, e) filling the idle gap by winding yard around the empty bobbin, and moving the head portion towards the friction drive roll, whereby the bobbin synchronizes its speed with that of the friction drive roll which slows the bobbin to a usual yarn winding speed, and f) maintaining in a stationary position an eccentric doughnut ring by a power operated means for forcibly and angularly positioning said doughnut ring whereby said bobbin is maintained at its instantly speed-accelerated position in contact with the said head member or at its normal running position in contact with said drive roll.

2. A process for automatically exchanging a plurality of bobbins mounted on radial arms of a stepwise rotatable bobbin holder, sequentially in such a way that when each one of said bobbins is fully wound with a yarn being continuously fed, a succeeding empty bobbin is exchanged for the fully wound bobbin, and comprising the steps of:

a) receding a fully wound bobbin from its respective service position while being kept in contact with a constantly revolving friction drive roll, and by a stepwise rotation of said bobbin holder, causing said yard to loosen, b) bringing said empty bobbin toward its respective service position simultaneously with the step of contacting the said friction drive roll with said empty bobbin, c) accelerating said empty bobbin at a predetermined rotational speed by bringing an end portion thereof into pressure contact with an enlarged head of said friction drive roll only for a limited period not to exceed 0.3 seconds, the rotational axis of said head being arranged eccentric to the rotational axis of the said drive roll, thereby forming a small idle gap between the empty bobbin and the friction drive roll per se, and causing the loosened yarn to be caught at its intermediate point by the accelerating, revolving empty bobbin, d) automatically breaking the yarn at a predetermined position between the said receding fully wound bobbin and the said empty bobbin by virtue of gradually increased tension developed in the yarn bridging these bobbins caused by the increased rotational speed of the empty bobbin, and e) removing said enlarged head portion from contact with said end portion for eliminating said idle gap and thus for establishing the direct contact of said empty bobbin with said friction drive roll so as to drive the bobbin at its regular winding speed, said yarn being continuously traversed throughout the operation.

3. A process as recited in claim 2 including increasing the empty bobbin's rotation speed by at least 50 percent of the usual yarn winding speed after the bobbin is transferred to said service position.

4. An apparatus for instantly accelerating the rotational speed of a bobbin, comprising:
a) a drive roll capable of rotating at a constant speed, b) a hollow, cylindrical, enlarged head member adapted to cooperate with said drive roll, made as a separate member therefrom, said bobbin being adapted for selectively engaging either said drive roll or said head member, c) a pin-and-ring coupling member mechanically connecting said drive roll with said head member for rotating the latter in unison with said drive roll, and allowing a radial shift of said head member relative to said drive roll, d) an eccentric doughnut ring kept stationary during yarn winding adapted to occupy either of two different angular positions around a predetermined center, and e) a power-operated positioner for forcibly and angularly positioning said doughnut ring, whereby said bobbin may be held at its instantly speed-accelerated position in contact with said head member or at its normal running position in contact with said drive roll.