Automatic Tension Control Apparatus

Abstract

The speed at which a filament should be winding on a reel at any given instant in order to have the reel packed in a predetermined manner is computed and compared to the measured speed of the filament. The tension on the filament is then changed so as to adjust the buildup of the filament on the reel as the filament is wound until the measured speed is equal to the programmed speed at any given instant. In a preferred embodiment, a pulse output tachometer connected to a metering roll generates a pulse train related to the movement of filament past the roll. A second pulse output tachometer is connected to the reel being wound to generate a pulse train representative of the total angular rotation and the instantaneous angular velocity of the reel. The output of the second tachometer is then operated upon to deliver a programmed pulse output representative of the speed of the filament winding on the reel needed at that particular total angular rotation in order to pack a beam in a predetermined manner. The programmed pulse output is compared to the metering tachometer output, and filament tension is adjusted so that the program is followed.

Description

BACKGROUND OF THE INVENTION

This invention relates to reel-winding apparatus and, more particularly, to control apparatus for automatically adjusting the tension on a filament or thread, such that a reel will be wound in a predetermined manner, regardless of differences in the type thread being wound, differences in thread denier, distortion of the reel, and the like. As will become clear, such apparatus is especially suitable for the "beaming" process of winding yarns for use in the textile industry.

It is frequently necessary to wind a filament on a reel such that the filament is loaded on the reel in an exactly predetermined manner. For example, it may be necessary to load a given length of filament on a reel with the wound reel having a given diameter after winding. This can be controlled by control of the "packing factor" of the filament which can be controlled, for example, by control of the tension of the filament during winding.

The problem is particularly severe in the preparation of "beams," which are large reels, wound with a large number (for example, 1600) of individual yarns from spools mounted on a rack termed a "creel." Such beams are subsequently used to produce fabric, and must be properly prepared in a predetermined manner. Any disparity in the loading of such beams results in flaws in the fabric being produced.

The loading of the beam is controlled by passing each thread through a tension control device, which can be manually or electrically adjusted. Such devices are shown in U.S. Pat. No. 2,777,545 to Rocket and in U.S. Pat. No. 3,043,936 to Rabeux.

During the winding of the beam, the beam may not wind with the desired buildup of radius due to variations in packing factor, actual distortion of the reel body and its end flanges due to the enormous forces built up by the wound filament, varying thread diameter, varying thread coating, and the like. These variations have to be offset by a change in the tension of the thread. However, presently available devices and techniques are too slow or incapable of determining improper beam packing, and a poorly prepared beam results. Moreover, when different or new thread spools are loaded into the creel, time-consuming readjustment of each tension device is needed to adjust for the characteristics of the new spools to produce a beam having the specified properties.

SUMMARY OF THE INVENTION

In accordance with the invention, the velocity that the filaments winding on the reel should have at any instant is computer generated. This programmed velocity is compared to the actual velocity of the filament as measured by a metering roll. A suitable control system then adjusts the tension on the filaments in order to stretch or relax the filament, and to adjust the packing of the filament, such that the filament builds on the reel in the predetermined manner which causes the measured filament velocity to always equal the desired or calculated filament velocity.

In one embodiment of the invention, a tachometer is connected to a metering roll around which at least one filament passes and generates an output signal representative of the actual speed of the filament. A second tachometer is then connected to the beam being wound and generates a signal representative of the number of times the beam has rotated. This signal is then modified by stored data regarding the initial diameter of the beam and the packing factor of the filament to deliver a programmed signal of what velocity the filament should have at the measured number of rotations of the beam. This programmed signal is then compared to the actual measured velocity, and, if the two are unequal, an error signal is generated to adjust the filament tension. Adjustment of filament tension then adjusts the packing of the beam to cause an increase or decrease in instantaneous filament velocity, as required by the velocity program to obtain a given final beam.

The novel circuit and process of the invention permit extremely high accuracy in the winding of beams since the response time of the system is very short. Thus, the measuring equipment responds virtually immediately to change filament tension with extremely small deviations of filament velocity from the programmed value. When using pulse-type tachometers, it has been found that deviations as small as 1 pulse per million can initiate corrective actions where the velocity measuring tachometer generates about 50 pulses per revolution of the metering roll.

While the novel invention is described herein with reference to a beaming operation, it will be understood that the concepts of the invention may be applied to any control application in which a measured variable is to be constrained to follow a pattern which can be predetermined.

It is an object of the present invention, therefore, to provide a control system and process for tension adjustment apparatus for use in the beaming process of winding filaments, such as yarn, which produces a beam of predetermined packing characteristics regardless of variations in filament characteristics, and regardless of distortions of the beam.

Another important object of the invention is to generate data related to the predetermined movement of a filament winding on a reel, if the reel is to be packed in a predetermined manner, and to force the measured instantaneous movement of a filament to match the generated desired movement.

It is another object of the invention to provide a control system and process for uniformly packing yarn on the beam so as to eliminate flaws in the fabric produced thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a winding machine incorporating the automatic tension control apparatus of the present invention.

FIG. 2 is a block diagram of the apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is schematically illustrated a winding system of the type to which the present invention can be applied. In the winding machine illustrated, there is a schematically shown creel 10 which consists of a plurality of spools of thread which are to be wound on a beam 11, which is subsequently used for the production of fabric. Typically, the creel 10 may have 1,600 individual spools of thread.

Three of these spools are shown in FIG. 1 as spools 12, 13 and 14. These spools are clamped into a suitable creel support structure and threads unwinding from the creel are passed through eyelets, schematically illustrated as eyelets 15, 16 and 17 for spools 12, 13 and 14, respectively, with the threads or filaments 18, 19 and 20 thereafter passing around thread tensioning devices 21, 22 and 23, respectively. Tensioning devices 21, 22 and 23 may be of the type known as the Whorl tension device, manufactured by the Valve Division of Allied Control Co., Inc., Plantsville, Connecticut. These tension devices are electrically operable to increase or decrease the tension on the filaments or threads which they receive.

Suitable electrical signals for controlling this tension can be applied to the individual tension devices in banks or individually, as desired, such that the same tension is applied to each of the threads of the creel 10. Each of the threads are then passed through a conventional comb 24 and from comb 24 are wound on the beam 11.

Beam 11 is a conventional and well known type of beam and is made of a central barrel having a given radius upon which the filaments are wound and side flanges 11a and 11b. Typically, the barrel and flanges of beam 11 may be of aluminum or some other strong structural material. It will be later noted that despite the apparent rigidity of the beam 11, the barrel will distort during the winding due to enormous forces created as the filament winds on the barrel, which forces tend to extend the barrel and distort the flanges 11a and 11b.

A suitable drive motor 25 is connected to beam 11 to rotate the creel, thereby to wind the filaments or threads from beam 11 on the creel, with controlled tension being applied to these filaments by the tensioning devices 21, 22 and 23.

As was previously mentioned, beams, such as beam 11, must be prepared with great precision if they are to be useful in the subsequent production of fabric which is free of flaws. Thus, poorly prepared beams, which are beams which are unevenly wound or are wound to radii different from a desired value, will cause fabric flaws during the fabric-weaving operation and are subject to rejection by the purchaser. In particular, it is most desirable that the beam be wound uniformly with filaments of a given length, such that the beam fills out to a given outside wound diameter. This must be done even though the threads being wound may be of different quality and diameter and even though the beam distorts due to the winding forces.

The control of the winding of the beam is obtained through the control of the tensioning devices 21, 22 and 23. Thus, by increasing tension on the filament or thread, the thread tends to stretch and thus narrow so that it occupies a smaller volume. Similarly, reducing the tension on the thread will cause it to expand, thereby occupying greater volume in the beam. With presently known control arrangements for controlling the tension of tension devices 21, 22 and 23, however, when the beam 11 is not being wound at any instant in the required manner to produce the desired ultimately finished beam, the information or intelligence regarding the improper instantaneous condition cannot be corrected quickly enough or accurately enough to produce the desired finished beam.

In accordance with the present invention, the beam winding process is monitored at every instant as soon as any variation from the theoretically desired or programmed condition is observed, correction is made immediately through the tensioning control devices. Thus, in accordance with the invention, a metering roll 30 receives and is driven by filaments 18 to 20 in the manner well known for such metering rolls. A tachometer 31 is then connected to metering roll 30 to deliver an output signal representative of the speed of the filaments 18 to 20 being wound from creel 10.

While any type transducer could be used, a preferable form of transducer 31 is a pulse-generating type in which a given number of pulses are produced for each revolution of metering roll 30. By way of example, a photographic film being optically measurable indicia can be carried on roll 30 to be scanned by a suitable scannable mechanism in transducer 31 to produce, for example, 50 pulses for each revolution of metering roll 30. The pulse repetition frequency will be related to the speed of the filaments being beamed, although it will be understood from the foregoing that filament speed need not be directly determined and that the number of pulses coming from transducer 31 can be used in comparison with a programmed pulse number to control the system.

A second transducer 32 is then appropriately coupled to beam 11 to generate an output signal representative of the total angular rotation of beam 11 at the measuring instant. In particular, transducer or tachometer 32 can also be pulse-generating transducer which generates a given number of pulses for each revolution of beam 11. This number of pulses, which is representative of the number of revolutions of beam 11, is then applied to a suitable programming circuit which converts this information into information representative of what the filament velocity should be as it winds on beam 11 if beam 11 were building up in the appropriate manner to become an acceptable finished beam at the end of the beaming process.

This calculated value, representative of desired filament velocity, is then compared to the output of transducer 31 which can measure actual filament velocity and any difference in the two signals generates an output error signal which controls the operation of the tensioning devices 21, 22 and 23. By way of example, the output of program circuit 35 will indicate that since beam 11 has rotated n rotations, the filament package has reached a radius of r so that the filament speed entering the beam should be s. The metering roll 30, however, indicates that the filament speed is greater than s, which means that the beam 11 has too great a radius and that the filament is being packed too loosely. Accordingly, the error signal from the error sensor 36 causes the tension of tension members 21, 22 and 23 to increase on the filaments 18, 19 and 20, so that the filaments now winding on beam 11 are stretched and caused to be somewhat thinner and are packed somewhat tighter. Thus, the rate of increase of beam radius is reduced such that the actual speed of the filament winding on beam 11 begins to approach the programmed value. A similar operation will occur if the measured filament speed at transducer 31 is less than the programmed speed, whereupon the tension on filaments 18, 19 and 20 will be reduced to permit a thickening of the filaments to increase their rate of buildup on the beam 11.

FIG. 2 schematically illustrates, in block diagram form, the programming circuit 35 and error detector circuit 36 of FIG. 1. In the circuitry of FIG. 2, it will be understood that the output of transducer 31 will be a pulse output related to the instantaneous filament speed

v.sub. n (t).

This output is applied directly to the error detector circuit 36. The output of transducer 32 is then modified by the programming circuit 35 to generate a signal representative of the desired speed of the filament entering the beam at any instant

v.sub. B (t).

It will be seen that

v.sub.B (t)=.omega.(r.sub.o +nD)

where

.omega. is the angular velocity of beam 11,

r.sub.0 is the radius of the barrel of the beam 11,

n is the number of revolutions of beam 11 (measured by the transducer 32) and

D is the packing factor of the thread on the beam 11.

Note that the actual packing factor will be varied between predetermined limits by the adjustment of the tension in the thread being wound.

By using the programming circuit 35 to generate a signal representative of v.sub.B (t) and then comparing this signal to the actual measured output of transducer 31 v.sub.n (t), one will have instantaneous information as to whether the metered actual velocity is correct or should be increased or decreased (by adjusting the buildup of the beam through adjustment of tension) in order to conform to the instantaneous desired or programmed velocity.

In order to perform the computation for v.sub. B (t), the programming circuit 35 includes a multiplier circuit 40 connected to a data input register 41 which can enter a given value D into multiplier 40, and a second multiplier 42 which is provided with a data input register 43 which can enter the beam radius r.sub. o into multiplier 42. The measured value n, which is the output of transducer 32, is then applied to multipliers 40 and 42 such that multiplier 40 multiplies n and D. This product is then added to r.sub. o from register 43 and the sum is applied to multiplier 42, whereby it is multiplied by .omega. (related to the output of transducer 32). The output of multiplier 42 is then the theoretical or desired value v.sub.B (t) for the filament being wound if the buildup of the beam is following the desired buildup to produce an acceptable beam. The outputs v.sub.B (t) of multiplier 42 and v.sub. n (t) of transducer 31 are then compared in error detector 36 and may be subsequently applied to an error storage circuit 44 (to insure that no output pulses are ignored due to coincidence or overlap of the two input signals) and thence to a digital-to-analog converter 45. The output of converter 45 is then applied to the tension control circuit shown in FIG. 1 as including tension devices 21, 22 and 23.

While the foregoing has described the comparison of output signals as being related to the velocities or speeds of the filament, it will be noted that the circuit of FIG. 2, in fact, permits comparison of pulse numbers. Thus, the total pulse count from tachometer 32 can be directly compared to a theoretically desired total pulse count for that instant from programming circuit 35 whereby any difference in pulse counts will create an output from error detector 36. A circuit of this type can give extremely high accuracy and sensitivity since it is capable of great resolution of the order of 1 pulse per million.

While the above description of the invention shows its application to beam winding apparatus, it will be understood that the novel control concepts can be applied generally to other processes in which a pulse count proportional to the process action is to follow a preprogrammed sequence of events.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A winding machine for winding a filament on a beam comprising, in combination:

means for rotatably supporting and rotating said beam to wind said filament thereon;

tension control means coupled to said filament operable for adjusting the tension on said filament;

metering means connected to said filament at a region removed from said beam for monitoring the speed of said filament past said metering means and generating an output related to said filament speed;

beam rotation measuring means for measuring the angular rotation of said beam;

program means connected to said beam rotation measuring means for determining the desired speed of said filament at any instant in order that said beam be loaded in a given manner and generating an output related to the speed determined by said program means;

difference monitoring means connected to the output of said metering means and to the output of said program means for comparing the actual speed of said filament to the programmed speed of said filament;

and means connecting said difference monitoring means to said tension control means for adjusting the tension of said filament to cause the speed of said filament to approach the programmed speed when there is a difference between the two.

2. The combination of claim 1 wherein said beam rotation-measuring means includes a transducer means coupled to said beam for measuring the number of rotations of said beam and the angular velocity .omega. of said beam; said program means including means for storing values related to a predetermined beam-packing density D and the radius r.sub. 0 for said beam when unwound, and for generating an output signal related to .omega.(r.sub. o +nD).

3. Apparatus for the preparation of a beam for use in the production of fabric comprising, in combination:

a creel consisting of a plurality of spools of thread wherein said threads are to be individually wound on said beam in a predetermined manner;

each of said threads being connected to said beam;

means for rotatably supporting said beam and for rotating said beam to wind said threads on said beam and to remove said threads from their respective spools;

tension control means connected to said threads for controllably applying tension to said threads as they wind on said beam;

first transducer means coupled to at least one of said threads for measuring a first parameter related to the movement of said threads;

second transducer means coupled to said beam for measuring a second parameter related to the winding of said threads on said beam;

programming means connected to said second transducer means and generating an output in the form of said first parameter which is related to a desired value of said first parameter required at the instant of measurement in order to wind said beam in a predetermined manner;

signal comparison means connected to said first transducer means and said programming means for comparing their measured and computed first parameters, respectively, and generating an output error signal responsive to a difference therebetween;

and circuit means connecting said output error signal to said tension control means for adjusting the tension on said threads in a direction to make said measured first parameter approach said computed first parameter.

4. The apparatus of claim 3 wherein said first parameter consists of the speed of said threads.

5. The apparatus of claim 3 wherein said first parameter consists of a pulse train in which the time between pulses is equivalent to a given length of said thread.

6. A control circuit for controlling the tension in threads being wound on a beam by adjusting a tension control means; said control circuit comprising:

first transducer means coupled to at least one of said threads for measuring a first parameter related to the movement of said threads;

second transducer means coupled to said beam for measuring a second parameter related to the winding of said threads on said beam;

programming means connected to said second transducer means and generating an output in the form of said first parameter which is related to a desired value of said first parameter required at the instant of measurement in order to wind said beam in a predetermined manner;

signal comparison means connected to said first transducer means and said programming means for comparing their measured and computed first parameters, respectively, and generating an output error signal responsive to a difference therebetween;

and circuit means connecting said output error signal to said tension control means for adjusting the tension on said threads in a direction to make said measured first parameter approach said computed first parameter.

7. The control circuit of claim 6 wherein said first and second transducer means comprise pulse-generating tachometers for generating pulse trains related to the movement of said threads and the rotation of said beam, respectively.

8. The process of winding a filament on a rotating beam such that the beam is packed in a predetermined manner which comprises:

measuring the angular rotation of said beam and generating a first signal related to the total accumulated angular rotation of said beam;

connecting said first signal into computer means for computing the speed which said filament should have as it winds on said beam at said given accumulated angular rotation of said beam if said beam is to be wound in said predetermined manner; and generating a signal related to a desired programmed instantaneous filament speed;

measuring the actual speed of said filament;

comparing said measured speed to said desired programmed speed at that time and generating an error signal related to their difference;

and increasing and decreasing the tension on said filament when said measured speed is respectively greater than or less than said programmed speed.