US3638414A

US3638414A - Programmed spindle speed

Info

Publication number: US3638414A
Application number: US874742A
Authority: US
Inventors: David M Williams
Original assignee: Fiber Industries Inc
Current assignee: Celanese Corp
Priority date: 1969-11-07
Filing date: 1969-11-07
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01
Also published as: BE758592A; GB1324422A; NL7016123A; IE34710L; DE2054627A1; CA926715A; IE34710B1

Abstract

An improved method and apparatus for programming the slowdown period of a yarn overend winding apparatus including draw rolls and a spindle wherein the draw roll and spindle are programmed in relationship to each other until the draw rolls reach a set predetermined low speed and then the spindle is brought to rest after the draw rolls have become stationary.

Description

United States Patent Williams 1 Feb. 1,1972

[54] PROGRAMMED SPINDLE SPEED [72] Inventor: David M. Williams, Greenville, S.C.

[73] Assignee: Fiber Industries, lnc.

[22] Filed: Nov. 7, 1969 I21 Appl. No.: 874,742

[52] U.S.Cl. ..57/93,57/55.5, 57/157 S, 242/261 [51] Int. Cl ..D0lh 1/26, D01h 1/36 [58] Field of Search ..57/88, 34, 55.5, 66, 75, 78,

[56] References Cited UNITED STATES PATENTS 3,358,433 12/1967 Curtis et al. ..57/93 3,472,014 10/1969 Taylor et al ..57/93 3,488,938 1/1970 Johnson et al.. .....57/98 3,521,441 7/1970 Lamparter ..57/93 X 3,526,244 9/1970 .loy ..57/93 X Primary Examiner-John Petrakes Attorney-Thomas J. Morgan, S. D. Murphy and Louis Gubinsky [5 7] ABSTRACT An improved method and apparatus for programming the slowdown period of a yarn overend winding apparatus including draw rolls and a spindle wherein the draw roll and spindle are programmed in relationship to each other until the draw rolls reach a set predetermined low speed and then the spindle is brought to rest after the draw rolls have become stationary.

10 Claims, 4 Drawing Figures PATENTEB FEB H972 3,53

sum 1 or 4 I nvenlora oAvlb M. WILLIAMS BYULW A llorney;

PATENTED FEB H972 3IQ3 L414 SHEET '8 BF 4 740/0 AC. DRAW m/ws MOTOR was %f FORMER 570p BRAKE [0W SPHD RfFfPf/K' POE/VHO I (AM METER CONTROL Invenlors DAVID M. WILLIAMS 'By (9W i Atlorneys PROGRAMMED SPINDLE SPEED BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for winding yarn packages especially of synthetic polymeric filaments or yarns, and is particularly concerned with the collection of such filaments in the form of packages on bobbins mounted on rotating spindles, in conventional drawing apparatus, or other forms of overend winding apparatus of the kind in which the filaments are fed to the spindles via rotating processing rolls, and the completed packages are brought to rest before being doffed, and the empty bobbins are brought from rest up to an initial operable rotational speed after the filaments have been secured thereto for rotation therewith.

The term apparatus of the kind specified, will-be used hereinafter to refer to such apparatus.

Overend winding apparatus may, for example, have a ringand-traveller yarn guide around each spindle, or comprise cap-spinning apparatus; but for convenience in describing the invention in this specification it will be assumed that the apparatus has a ring-and-traveller yarn guide, although it must be understood that the present invention applies also to other forms of overend winding apparatus. The package produced by such apparatus will usually be tapered in form.

Further, for convenience in this specification, the roll or cooperating rolls, which engage the running filament immediately before it is collected on the package, will be referred to hereinafter and in the claims as the draw rolls, although as indicated above, the present invention is applicable to various kinds of apparatus other than drawing apparatus. By drawing" we mean that a filament of synthetic polymeric material is stretched to cause the molecules to orientate themselves along the filament axis, thus increasing the tenacity of the filament.

The filament may pass between the nip of two cooperating draw rolls, or be wrapped around a single roll, or around a pair of cooperating rolls comprising a rotating roll and separator roll, which latter may be rotating or stationary.

The winding apparatus may include programming means arranged to vary the speed of the spindle throughout the major part of the winding of each package, for some particular purpose; and the present invention is particularly, but not exclusively, concerned with such overend winding apparatus in which it is possible so to vary the value of the spindle speed according to a desired program.

In overend winding apparatus, it may be shown that the spindle speed is equal in magnitude to the traveller speed plus the winding-on speed of the filament, this latter term being the fraction of spindle speed corresponding to the winding-on of the filament, and being equal in magnitude to the spindle speed if the traveller is stationary.

Thus, it is possible to control some feature of the winding operation which is related to winding-on speed and traveller speed throughout the production of a package, in order to obtain some desired object, by employing a suitable spindle speed program.

In any such spindle speed program, the traveller speed should not, under known conditions, be allowed to exceed about 8,000 r.p.m., except transiently, otherwise the yarn guide device will be subjected to excessive stresses, and unacceptable wear and breakage will ensue.

Further it is desired that a stable package be produced; and thus it is essential that the filament be tensioned to an extent above a certain minimum value so that a stable balloon be maintained, and the manner of the lay of the filament on the package be predicted, and the filaments arranged to be securely laid on the package and not tending to slough off it.

Thus, the rotating traveller is used to tension the running filament to the requisite amount in order that a stable balloon may be obtained throughout the winding operation, the balloon being tensioned to an amount of at least 0.l grams per denier in the case of a polyamide filament, and the spindle speed is so programmed that the traveller speed is held within a predetermined narrow range of values.

It is particularly desirable that this condition should be maintained during the startup and slowdown periods in the formation of each package, because, due to the reasons given above, such a condition will reduce the propensity of the filament to break during these periods (filament breakages being more likely to occur at these periods in the package-winding cycle, than intermediate therebetween).

The present invention is concerned with obtaining such a winding condition while the winding machine is slowing down, by the provision of positive programming means arranged to control the spindle speed during this period. During this period also, loops tend to be formed on the package, if filament breakages are avoided, and the spindle speed program during this period is therefore arranged to be such that both kinds of irregularities in the winding operation are reduced.

Slowdown breakages occur when the spindle rotational speed is reduced at a faster rate than is desired in relation to a given draw roll deceleration, with consequent overfeeding of the filament from the draw-rolls to the spindle causing an uncontrollable balloon to be produced. Thus, the filament may eventually lick back onto the draw rolls, or become entangled and snagged either with itself or on parts of the winding apparatus, and so break.

However, if the spindles are allowed to run on by an excessive amount, or the draw rolls are braked too quickly, then the twist insertion rate in the balloon rises, and this twist runs back to the draw rolls, and a so-called slowdown loop will occur. Increase in the twist insertion rate occurs because, in the dynamic state, the form of the balloon will remain substantially constant. Thus, if the filament delivery speed, i.e., draw roll speed, is reduced sharply, the winding-on speed must reduce in proportion. However, if the spindle speed maintains the same value, the traveller must accelerate to compensate for the reduced winding-on speed, until when no filament is being delivered, then none of the filament is wound onto the package and the balloon will speed up until its rotational speed is equal to that of the spindle. This increase in traveller speed and reduced winding-on speed accounts for the increase. in the twist insertion rate.

The increased twist runs back up the filament and may cause a wrap of the filament to slip off the draw rolls, when these comprise a cooperating draw roll and separator roll. The sudden concomitant increase in the amount of filament in the balloon will cause a complete yarn loop to be wound onto the package.

It will be appreciated that it is relevant to such loop formation whether S or Z twist is being inserted into the filament, because, in a given form of winding arrangement, the insertion of one direction of twist will tend to keep the wraps on the draw rolls, while the insertion of the other direction will tend to cause the wraps to roll off the draw rolls.

Single-filament loops may, however, be caused in the threadline even if complete yarn loops are not produced; and these single-filament loops are equally prejudicial to the usage of the yarn.

The existence of any slowdown breakages and loops will result in the packages sold being slightly below standard weight (because the portion of the filament with loops will have to be stripped from the package during inspection), if as usual it is intended that the portion of the filament processed during the slowdown operation of the winding apparatus should form part of the package. If slowdown breakages and loops can be eliminated, it will obviate the need for packages to be superficially inspected, and so cause a reduction in operation costs.

With respect to the production of standard weight processed packages, it will be appreciated that winding apparatus having a programmed winding procedure, and in particular a programmed slowdown procedure, will be less likely to suffer from between doff variations in the winding operation, and hence there is less likelihood of uncontrollable variations in package weight occurring, compared to winding apparatus which is not controlled in such a positive manner.

It is of importance not to produce packages of below standard weight due to unintentional breakages occurring, or due to the formation of loops, because of their possible unsuitability for use in subsequent manufacturing processes. Further, there will be a high wastage rate if the filament wound thereon is to be used in specified discrete amounts, because the amount of the filament remaining on he supply package will be considerably more than was intended after, say, processed packages of a specified weight have been wound therefrom.

This wastage of the filament will be particularly important if heavy denier yarns are being processed on the machine, which yarns usually are desired to have as high a throughput rate as possible and have a relatively shorter package-winding cycle.

The presence of loops in the package will also cause package instability at their locations and this will cause a transient relatively large reduction in the takeoff tension of the filament at this point when unwinding the filament from the package. The package will, therefore, be unsuitable for use on a creel where the filament of one package is connected to the filament of an adjacent package.

Hence, it will be appreciated that, it is important to be able to predict precisely the slowdown procedure for the winding apparatus, and the spindle speed program should be such that there is avoidance both of slowdown breakages due to the spindle speed decaying too quickly, and of slowdown loops due to the spindle running on more than was intended. It may be possible according to this invention to arrange the slow-' down winding conditions such that both these faults can be eliminated; but in any event a compromise solution can be adopted so that the optimum winding condition for minimum slowdown breakage rate and loop formation rate are obtained.

If such optimum conditions are attempted to be employed in winding apparatus not having positive programming means, it is found that the manner of operation of the apparatus requires constant observation in order that the critical conditions be maintained, and the controlling elements of the apparatus require constant trimming to preserve the desired manner of operation, particularly if the slowdown period is initiated when the package rotational speed is relatively high and the package being wound is relatively large.

In order to reduce or eliminate the above problems associated with the slowdown sequence of an overend yarnwinding process, it has been suggested to program the slowdown period of the draw-roll-winding apparatus so that spindle speed is controlled in a predetermined relationship to the speed of the draw rolls until the draw rolls have become stationary and then applying the full spindle brake simultaneously with draw roll stoppage to bring the spindle to rest as soon as possible within machine capability.

The aforementioned type of slowdown sequence as well as .similar procedures, have been found to be deficient for a number of reasons, the major one being the high degree of reliance placed upon the spindle braking mechanism during the stopping sequence. It is apparent that as soon as the draw rolls have reached standstill, the spindle must become stationary almost immediately in order to prevent yarn breakage and maintain the desired threading of yarn over the various rolls and guides for startup. The only control allowed the operator with such a system is adjustment of spindle braking force which requires constant observation of the machine. As the spindle brakes become worn, i.e., less efficient, because of repeated usage, the spindle runs on excessively causing a slowdown loop" in the dynamic state and poor control of balloon tension through to complete machine stoppage. Instead of the yarn being threaded through the traveller in machine startup condition, the yarn must be completely restrung from the supply package through the various guides and over the various rolls to the spindle. Obviously, the linear length of yarn wastage is also markedly increased.

Therefore, it is an object of the present invention to provide an improved slowdown sequence for overend yarn winding apparatus.

Another object of this invention is to provide a slowdown sequence for overend yarn winding apparatus including draw rolls and a spindle wherein means is provided to compensate for changes in spindle brake efiiciency.

A further object of the invention is to provide programming apparatus for carrying out the above slowdown sequences.

Still another object of the invention is to provide yarn overend winding apparatus and process which will reduce the number of slowdown filament breakages and loops while producing, consistently and reliably, satisfactory standard weight tapered packages which include the portion of the filament processed while the apparatus is slowing down.

Other objects of the invention will be obvious to those skilled in the art from the detailed description of the invention hereinafter.

SUMMARY OF THE INVENTION In accordance with the invention, it has now been found that the slowdown sequence of the full package-winding cycle of a yarn overend winding apparatus can be controlled to reduce slowdown breakages and loops while leaving the yarn properly strung for machine startup by a process which comprises positively forwarding yarn by draw rolls to a rotating spindle for winding thereon in the form of a yarn package; programming the slowdown period of the full package-winding cycle in such a manner that the spindle speed is positively controlled in a predetermined relationship to the speed of the draw rolls during the first part of said period until the draw rolls reach a low predetermined speed and thereafter regulating the time of application of maximum spindle brake so that said spindle becomes stationary after said draw rolls with the yarn maintained under a predetermined tension.

Further, it has been found that the process of the invention can be carried out by an overend winding apparatus of the kind in which yarn is fed to a rotating spindle from processing rolls, said apparatus including:

a. a motor adapted to drive the spindle,

b. a second motor adapted to drive the draw rolls independently of the spindle,

c. programming means for controlling the winding operation of the apparatus in a positive manner at least during the slowdown period of the full package-winding cycle, said means including a servo device forcontrolling the spindle drive motor, a first tachogenerator for the spindle and a second tachogenerator for the draw rolls, and a reference error unit adapted to compare electrical signals produced by said tachogenerator-s during said slowdown period and to feed a resultant electrical signal therefrom to said servo device, and

d. a low-speed sensing device adapted to receive electrical signals from said second tachogenerator and to activate said servo device to stop the spindle drive at a predetermined time after sensing a predetermined low speed from said second tachogenerator.

DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION In conventional draw-twisting apparatus for synthetic polymeric filaments, such as polyamide, polyester, cellulose ester, polyacrylonitrile or polyolefin filaments, there are included two or more pairs or sets of cooperating rolls, each pair I of rolls being arranged to impart a different speed to the filament, causing the filament to be drawn between two adjacent pairs of rolls, (and, optionally to relax between another two adjacent pairs of rolls).

Snubbing devices, which impose a substantial restraint on the running filament, may be included in the apparatus, so that there may be a single drawing zone or several such zones, and possibly also regions in which the yarn may relax or be subjected to some other treatment process. The first pair of rolls which engage the yarn are feed rolls for the apparatus, and between these and the final pair of rolls, which are positioned immediately before the winding apparatus, and which are herein referred to as draw rolls," the filament is stretched to many times its original length.

Thus, as shown in FIG. 1 a polyamide filament l is withdrawn from a cheese 3 mounted on a container 5, and passes through yam guide means 7, 9, ll, 13 to a pair of cooperating nip rolls 15, 15 From these nip rolls, which serve as positive feed rolls, the filament is wrapped around an inclined snubbing pin 17, which causes a considerable physical restraint to be imposed on the filament resulting in the filament necking" and being stretched to, say five times its original length. The filament then passes around draw roll 19 with its inclined separator roll 21, which rolls, which forward the filament to a balloon guide 23 and thence to winding apparatus. I

The winding apparatus comprises a vertically extending spindle 25 on which a tube 27 for the yarn package 29 is rotatable mounted, and around which spindle yarn guide means is disposed for causing the filament to be laid on the package. The yarn guide means is in the form of a conventional ring 31 and traveller 33 device mounted on a ring rail 35, this ring rail being reciprocated along the spindle axis by a known form of builder mechanism, including a stricker plate 37 secured to the ring rail for reciprocation therewith. At each end of each reciprocation stroke the plate is arranged to operate a microswitch (not shown) and so cause reversal in the direction of movement of the ring rail. The positions of the microswitches are controlled respectively by two cams rotatably mounted on a shaft driven at a constant speed.

The main drive means for the draw twist machine comprises an AC induction motor coupled to each of the feed rolls and the draw rolls of the machine, but not to the spindles on which the packages are being formed, the spindles being arranged to be driven by a separate DC motor.

Thus, the drive means of the draw twist machine is in two parts, and hence both the spindles and the draw rolls can be allowed to accelerate and decelerate independently of each other during the startup and slowdown periods of each package winding cycle.

In order that filament breakages shall be avoided during the startup period of each package winding cycle, an electrical timer is included in the winding apparatus, this timer being arranged so that the draw rolls (and the feed rolls) are not driveably connected to the AC motor until after the spindles have been driveably connected to the DC motor. The setting of the timer is adjustable manually.

The criteria upon which the optimum value for the delay period in starting the AC motor after the DC motor is determined are set out below.

It is essential that a stable balloon be maintained as soon as the draw rolls have started to rotate and the filament is being wound on the package, and consequently, it is important that the traveller speed be maintained within a certain range during this latter part of the startup period, when the draw rolls are rotating.

Although the traveller speed of the yarn guide should at no time during this period be permitted to exceed the highest speed of the range, it should start at this speed when the draw rolls have started to rotate, or rise to it soon after they have started to rotate. As a result the traveller speed will then fall to a value near to its minimum acceptable speed when the draw rolls have obtained their maximum speed.

in this way the balloon tension is given its maximum possible value initially, which is found to cause a reduction in the number of filament breakages. The spindles are arranged to obtain their maximum speed, i.e., their requisite speed according to the winding program at the end of the startup period, either at the same time as or before the draw rolls have obtained their corresponding maximum speed.

During the startup period in each package winding cycle, it is usual to arrange for a waste bunch to be wound, particularly as the filament at this point may be inadequately drawn or otherwise processed.

The time taken for the draw rolls to be brought up to speed should be as short as possible, for productivity reasons, and such that the waste bunch, which is wound during this time, is not too large.

Throughout the major part of the winding operation, when the winding apparatus is operating in a normal manner, the AC motor is arranged to drive the draw rolls at a constant speed, which speed is related to the desired processing speed for the apparatus.

However, the DC motor is arranged to drive the spindles according to a predetermined winding program during this period, in order that some desired object, with respect to the winding operation, may be obtained.

Thus, the spindle speed can be arranged to be varied throughout the winding of a package in accordance with the profile of a cam embodying the desired spindle speed program.

The DC motor driving the spindles is arranged to be controlled by a servo device, which in turn is controlled by the cam, this cam being arranged to be rotated at a constant speed by being rotatably mounted on the shaft comprising the ring rail traverse cam drive means.

The servocontrol device for the DC motor comprises a three-phase magnetic amplifier, the input of which is controlled by a preamplifier. The motor armature voltage comprises the output from the magnetic amplifier, and the current from a rectifier positioned across one phase of the electrical supply to the device comprises the shunt field excitation current for the motor.

The programming cam is used to produce a reference signal, which varies in accordance with the winding program, and the spindle speed is monitored continuously by means of the first tachogenerator operably coupled to the output shaft of the DC motor. The reference error unit compares the signal from the first tachogenerator with the reference signal.

The error signal obtained by this comparison is then used to alter the output of the DC motor by being fed to the preamplifier of the servocontrol device and so alters the magnitude of the current fed to the armature of the motor.

The cam follower comprises the slider of a linear potentiometer, and the output from this potentiometer is the reference signal.

Trimming rotary potentiometers are provided at each end of the linear potentiometer of the programming means, each such rotary potentiometer having a range approximately 20 percent of the linear potentiometer range and being used to control the effective range of the linear potentiometer.

[t is essential that the balloon tension be maintained within a similar narrow range of value during the slowdown period also, so that breakages may be reduced or avoided during this period.

The optimum slowdown conditions required to be reproduced by the winding apparatus in winding a yarn of 40 denier polyhexamethylene adipamide, for instance, are that the traveller speed shall not fall below 2,500 rpm. while the draw rolls are rotating and the filament is being wound in order that a stable balloon may be maintained and that the spindles shall be brought to rest as soon as practicable after the draw rolls whereby there will be reduction in the number of filament breakages and loops.

Due to the relatively high inertia of the motors coupled respectively to the spindles and the draw rolls, both the spindies and the draw rolls will tend to run on when the motors are deenergized, and in any event they will decelerate at rates which are independent of each other.

Thus, at the start of the slowdown period, the AC motor driving the draw rolls may be switched off so that the draw roll speed is allowed to decay normally. Preferably, a draw roll braking means is employed.

In order that there should be the controlled predetermined relationship between the spindle speed and the draw roll speed during the first part of the slowdown period the second tachogenerator is provided to monitor the speed of the draw rolls, and during the first part of the slowdown period, the output signal from this second tachogenerator is fed to the reference error unit.

The connection of the second tachogenerator to the reference error unit, and the disconnection of the program cam potentiometer therefrom, is caused by the programming means upon the transference of the winding apparatus from its normal operating procedure to its slowdown procedure. (Compare FIGS. 3 and 4) The reference error unit compares this signal with that from the first tachogenerator monitoring the spindle speed, and feeds back a signal to the DC motor to drive it, so that the two motors slow down at a predetermined ratio.

The programming means causes another signal to be compounded with the above-mentioned signal, the magnitude of which second signal is such that, alone, it would cause the spindles to be driven at above the minimum value of, say, 2,500 r.p.m.

This second signal is produced by a traveller speed potentiometer which is positioned across a fixed voltage. When the apparatus is idle, this potentiometer is adjusted to give the desired voltage, determined empirically previously, and the programming means places this potentiometer across the first tachogenerator, which is coupled to the DC motor drive shaft, when the slowdown procedure is initiated. This second signal can be eliminated by adjusting the spindle brake means to allow a minimum spindle speed at time of draw roll stop by comparison through the reference unit.

The above-referred-to program for the slowdown period of the package winding cycle is shown graphically in FIG. 2, in which the full lines indicate the actual speed/time programs of the spindle and draw rolls respectively.

In order to ensure that, when the winding apparatus changes over from the normal operating procedure to the slowdown procedure, there is no suddenjump in the DC motor speed or traveller speed, and the winding apparatus begins smoothly to slow down, there is provided a changeover speed" potentiometer positioned across the second tachogenerator, i.e., that which is operably coupled to the draw rolls. During the initial setting up of the apparatus, with the apparatus running, and the spindle speed arranged to be the value at which the slowdown procedure is to be initiated, this potentiometer is adjusted so that no signal is fed from the second tachogenerator to the reference error unit.

As already mentioned, in order that a positive control may be maintained, it is advantageous to arrange that the spindles are driven against lightly applied braking pressure during the first part of the slowdown period.

Thus, upon the transference of the winding apparatus from its normal operating procedure to its slowdown procedure, the programming means is arranged to actuate the spindle brake means, and during the initial setting up of the winding apparatus, with the apparatus operating and with the brake means in this position, this means is adjusted so that the DC motor armature current is at a low, finite, but detectable value. Hence, the spindle drive means will not hunt during the first part of the slowdown period.

The low-speed sensing device coupled to the second tachogenerator is arranged also to control the spindle-braking means. The arrangement is such that, when the sensing device detects that the second tachogenerator is registering a predetermined low speed for the draw rolls, the sensing device causes the spindle-braking means to be actuated to cause maximum braking restraint to be applied to the spindles at a predetermined time after said low speed is reached to bring the spindle to rest after the draw rolls have become stationary with proper tension on the yarn through to the spindle, which is the condition required to avoid the occurrence of slowdown loops on the package being wound. In this manner, needed flexibility is incorporated into the programmed slowdown sequence. By allowing adjustment of time of maximum spindle brake application in conjunction with control of braking force, the aforementioned disadvantages, particularly variation in balloon tension and degree of draw at standstill, are markedly reduced. With the present invention, the machine is stopped with the yarn in position for the startup sequence. Restringing, which accounts for the major employee cost of the draw-twisting operation is limited to severing the yarn past the traveller, removing the full package and inserting a new pim on the spindle. An additional advantage arises from the fact that the yarn is fully drawn through to the traveller which reduces yarn breaks upon startup because of the increased strength of the drawn yarn.

The sensing device is also operably coupled to the spindle drive means servo device during the slowdown period, and upon the activation of the braking means by the sensing device, the sensing device simultaneously causes the deenergization of the DC motor driving the spindles. Thus, there is nothing counteracting the torque applied by the braking means on the spindles.

Thus, during the slowdown period in each package-winding cycle, the manner of operation of the DC motor is positively programmed so as to avoid the occurrence of both filament breakages and loops during this period.

A second variable timer is included in the apparatus so that the movement of the ring rail of he winding apparatus is controlled during the slowdown period. It is important that the ring rails should not be brought to rest before the slowdown bunch has been wound onto the bobbin. Thus, by use of this second timer, the ring rail is stopped at a predetermined time after the initiation of the slowdown program, this delay being such that the ring rail is stopped after the draw rolls have stopped. The spindles tend to run on after this time, even under maximum braking forces, particularly if relatively large packages are being wound at relatively high speeds.

According to the present invention, the following operating conditions were employed during the slowdown sequence for a draw twist machine drawing 40 -denier polyhexamethylene adipamide yarn having 13 constituent filaments, the machine operating at a drawing speed of 4,200 feet per minute.

SLOWDOWN SEQUENCE At the termination of the full package build cycle as determined automatically by the particular programmed means em ployed, the slowdown sequence is initiated. Simultaneously (as graphically depicted in FIG. 2 of the drawing), the draw roll motor is deenergized, the draw rolls are braked so that they reach a stationary position from an initial speed of about 4,200 r.p.m. in an approximate preset time, for example 20 seconds, and a partial spindle brake is applied against the driven spindles rotating at about 8,000 r.p.m. As the draw rolls decelerate, draw roll and spindle speeds are continuously monitored and fed into the reference error unit which programs the spindle speed down in preset relationship to draw roll deceleration. When the draw rolls decelerate to the predetermined low speed, for example 1,000 r.p.m., the spindle motor is deenergized and maximum spindle brake is applied at a set time thereafter to stop the spindle with adequate tension on the yarn and minimum run-on after the draw rolls have become stationary. For example, the spindle brake is set so that the spindle is rotating at a predetermined speed, for example 3,0003,500 r.p.m., when the draw rolls have stopped.

The spindle is then brought to stop 3-5 secondsafter the draw rolls stop and the slowdown sequence is terminated about 24 seconds after the initiation thereof. In practice a separate timer lowers the ring rail of the ring and traveller apparatus about 1-2 seconds before the draw rolls stop so that adequate but minimum waste yarn is wound about the waste whorl.

In addition to the elimination of filament breakage during the slowdown period and reduction in slowdown loops to below 1 percent, the yarn is drawn and under tension suitable for start up.

The accuracy with which the predetermined startup and slowdown program was reproduced by the apparatus described above was i k percent, which was the accuracy of the motors employed. This was found to be adequate and the beneficial effects, referred to above as being obtainable by use of the apparatus according to the present invention, were found.

In practice, it is found that there is a range of several seconds, i.e., 3-5, during which the spindles may come to rest, for a given slowdown period for the draw rolls, and in which range neither slowdown breakages nor loops occur. At speeds above 8,000 rpm, the traveller becomes subject to excessive stresses, and this speed was therefore never exceeded.

ln operation, the spindle brake was found not to need readjustment over a considerable period of operation of the machine while in conventional equipment of this type the spindle brake would require resetting at intervals of approximately 3 months.

It will be appreciated that the quality of yarn packages produced on apparatus according to the invention will be improved, and the yarn wound thereon will have greater uniformity, compared with what has been possible heretofor without an excessively high wastage rate associated with each machine.

In addition, the apparatus allows for considerable flexibility in the manner in which it may be used, while still being capable of giving the benefits occurring from the use of the present invention. The use of two control means, time of application of maximum spindle speed brake as well as control of braking force, give this increased flexibility in comparison with the process rigidity present when the time control component is absent, i.e., maximum spindle brake is always applied at draw roll stoppage.

It is understood, of course, that various changes may be made in the invention which will be obvious to those skilled in the art. For example, the invention may be employed with all types of continuous yarns, including spun staple yarn, such as polyamides, polyesters, polyacrylonitriles, polyolefins, polyurethanes, polycellulosics, etc. Additionally, between startup and slowdown sequences, the package build may be entirely controlled by a preset cam arrangement which regulates spindle speed in accordance with a predetermined program as opposed to the continuing monitoring of the feedback system of the drawing and the operation need not be lagged, i.e., continuous filaments could be fed directly from the extrusion apparatus to the draw twister.

lclaim:

l. A method of winding a yarn package on yarn overend winding apparatus in a manner to reduce slowdown breakages and loops, while leaving the yarn properly strung and drawn for machine startup, which comprises:

a. positively forwarding yarn by draw rolls to a rotating spindle for winding thereon in the form of a yarn package;

b. programming the slowdown period of the full packagewinding cycle by positively controlling spindle speed in a predetermined relationship to the speed of the draw rolls during the first part of said period until the draw rolls reach a low predetermined speed;

c. thereafter regulating the time of application of maximum spindle brake so that said spindle becomes stationary after said draw rolls with the yarn maintained under a predetermined tension; and

d. stopping said draw rolls independently of said spindle when a full yarn package has been wound and bringing said spindle to rest after the draw rolls have become stationary.

2. The method of claim 1 wherein said yarn is a polyamide.

3. The method of claim 1 wherein said yarn is a polyester.

4. The method of claim 1 wherein said yarn is a polyolefin.

5, The method of claim I wherein said yarn is a polyacrylonitrile.

6. The method of claim 1 wherein the startup period of the full package-winding cycle is also programmed in a predetermined manner.

7. The method of claim 1 wherein the portion of the full winding cycle between startup and slowdown sequences is programmed in a predetermined manner.

8. The process of claim 1 wherein said draw rolls are driven at a constant speed during said full package-winding cycle and the spindle is driven separately therefrom according to a predetermined program.

9. Overend winding apparatus of the kind in which yarn is fed to a rotating spindle from processing rolls, said apparatus including:

a. a motor adapted to drive the spindle;

b. a second motor adapted to drive the draw rolls independently of the spindle;

c. programming means for controlling the winding operation of the apparatus in a positive manner at least during the slowdown period of the full package-winding cycle, said means including a servo device for controlling the spindle drive motor, a first tachogenerator for the spindle and a second tachogenerator for the draw rolls, and a reference error unit adapted to compare electrical signals produced by said tachogenerators during said slowdown period and to feed a resultant electrical signal therefrom to said servo device; and

10. The apparatus of claim 9 wherein said servo device activates a timing device which applies maximum braking force to said spindle at a predetermined time after said activation.

Claims

1. A method of winding a yarn package on yarn overend winding apparatus in a manner to reduce slowdown breakages and loops, while leaving the yarn properly strung and drawn for machine startup, which comprises: a. positively forwarding yarn by draw rolls to a rotating spindle for winding thereon in the form of a yarn package; b. programming the slowdown period of the full package-winding cycle by positively controlling spindle speed in a predetermined relationship to the speed of the draw rolls during the first part of said period until the draw rolls reach a low predetermined speed; c. thereafter regulating the time of application of maximum spindle brake so that said spindle becomes stationary after said draw rolls with the yarn maintained under a predetermined tension; and d. stopping said draw rolls independently of said spindle when a full yarn package has been wound and bringing said spindle to rest after the draw rolls have become stationary.

2. The method of claim 1 wherein said yarn is a polyamide.

3. The method of claim 1 wherein said yarn is a polyester.

4. The method of claim 1 wherein said yarn is a polyolefin.

5. The method of claim 1 wherein said yarn is a polyacrylonitrile.

9. Overend winding apparatus of the kind in which yarn is fed to a rotating spindle from processing rolls, said apparatus including: a. a motor adapted to drive the spindle; b. a second motor adapted to drive the draw rolls independently of the spindle; c. programming means for controlling the winding operation of the apparatus in a positive manner at least during the slowdown period of the full package-winding cycle, said means including a servo device for controlling the spindle drive motor, a first tachogenerator for the spindle and a second tachogenerator for the draw rolls, and a reference error unit adapted to compare electrical signals produced by said tachogenerators during said slowdown period and to feed a resultant electrical signal therefrom to said servo device; and d. a low-speed sensing device adapted to receive electrical signals from said second tachogenerator and to activate said servo device to stop the spindle drive at a predetermined time after sensing a predetermined low speed from said second tachogenerator.