US3099048A

US3099048A - Apparatus for automatically controlling the drafting of elongate materials

Info

Publication number: US3099048A
Application number: US784568A
Authority: US
Inventors: Locher Hans
Original assignee: Zellweger Uster AG
Current assignee: Zellweger Uster AG
Priority date: 1958-01-09
Filing date: 1959-01-02
Publication date: 1963-07-30
Anticipated expiration: 1980-07-30
Also published as: CH356386A; DE1097328B; GB863146A; FR1210083A; NL99739C

Description

July 30, 1963 H. LOCHER 3,099,043

APPARATUS FOR AUTOMATICALLY CONTROLLING THE DRAFTING OF ELONGATE MATERIALS 4 Sheets-Sheet 1 Filed Jan. 2, 1959 fnventar Hans Locher BY Hwwm M9 w. $444014 Aifamey July 30, 1963 H. LOCHER 3,099,048

APPARATUS FOR AUTOMATICALLY CONTROLLING THE DRAFTING OF ELONGATE MATERIALS Filed Jan. 2, 1959 4 Sheets-Sheet 2 [nventar Hans Locher 4W 5);! BY M MW Attorneys July 30, 1963 H. LOCHER 3,099,048 APP FOR A MATICALLY CONTROLLING v T FTING ELONGATE MATERIALS Filed Jan. 2, 1959 4 Sheets-Sheet 5 INVENTOR HANS L0 R BY W Y M a) LAM ATTORNEYS July 30, 1963 H. LOCHER 3,099,048

APPARATUS FOR AUTOMATICALLY CONTROLLING THE DRAFTING 0F ELONGATE MATERIALS Filed Jan. 2, 1959 4 Sheets-Sheet 4 FIG. 561

FIG. 5b

INVENTOR HANS LOCHER ATTORNEYS United States Patent 3,699,048 APPARATUS FQR AUTQMATICALLY CQNTROL- LING TEE DHQG 0F ELONGATE MATE- RIALS Hans Locher, Uster, Switzerland, assignor to Zellweger Ltd., Uster, Switzerland, a Swiss corporafion Filed Jan. 2, 1959, Ser. No. 784,563 Claims priority, application Switzerland Jan. 9, 1958 11 Claims. (Cl. 19-240) This invention relates to control means, more particularly to methods and apparatus for automatically controlling the drawing or drafting of elongate material by means of drafting rolls through which said material is fed.

A variety of materials are fabricated by passing the material through apparatus which serves to draw the material into an elongate shape. Thus, in the fabrication of textile yarns, the raw material is passed through a series of draw frames, spinning frames, or the like, to produce elongate yarn of desired thickness. The term spinning will be here employed to designate all of the fabrication steps to which textile fibers are subjected in order to form the final yarn product.

In the spinning of textile materials, a variety of problems arise in controlling the drafting of the textile material so as to provide yarn, sliver, or roving of uniform weight per unit length. Means are known for automatically controlling the Weight per unit length of the fabricated yarn. These means generally empioy a measuring device to continuously measure the weight per unit length of the yarn. These continuous measurements are averaged, and then the instantaneous deviations are obtained by comparing the instantaneous measurements with the average. A signal is produced depending on the magnitude of these deviations, and the signal is amplified and employed to control the speed of drafting. The measuring components employed are either electrical, optical or pneumatic. The generally available measuring components are however not stable over a sufficiently long time period so that any average range within which it is desired to maintain quality control usually is unmaintainable over the entire production run resulting in a long term quality variation. This may of course, be overcome by frequent calibration of the measuring device, which of course requires uneconomical down-time. Where long term variations are ignored, conventional control apparatus is adequate, but this is not always feasible.

It has been proposed to eliminate some of the above noted problems by ignoring long term variations. This is feasible since during the spinning operation the greater portion of deviations are of a short term nature, with a lesser number being of medium term nature, and only an insignificant number of variations being of a long term nature. Where these long term variations are ignored, some difficulties still arise in that control action is not adequate at start-up of spinning apparatus. Additionally, the average value against which deviations are compared requires fairly complex circuitry in order to permit averag'ng over a significant time period.

It is with the above problems in mind, that the present means have been evolved, means permitting the automatic control of material drafting operations to produce a substantially uniform product, and with the controlling action compensating for deviations of a long term, medium term, or short term nature.

It is accordingly a primary object of this invention to provide an improved control for regulating the operation of material fabricating equipment in response to quality variations of the material.

Another object of the invention is to provide quality control means regulating material drafting operations so P lC as to eliminate long term, medium term, and short term variations in said material.

It is also an object of this invention to provide an nn-proved method for controlling textile spinning operations so as to produce yarn of substantially uniform quality. I

It is also an object of the invention to provide means compensating long term disturbing influences on the measuring element of a control system.

These and other objects of the invention which will become apparent in the following specification and claims are achieved by provision of measuring means in combination with the drafting rolls of spinning equipment, so that a signal is transmitted from said measuring means indicative of the quality of the material passing therethrough. Generally measurements of material thickness are made in said measuring means.

One of the conventionally employed plurality of pairs of drafting rolls is operated at a constant speed and another of the pairs of drafting rolls is operated at a variable speed. Means are provided indicating the differem tial in angular speed between an angular speed proportional to that of the variable speed drafting rolls and an angular speed of that of the constant speed drafting rolls. This differential angular speed is fed through a reducing means to position converting means which puts out an electrical signal indicative of the aforementioned speed differential. The electrical signal provided by the posi tion converting means is fed to compensating means along with a measuring signal from said measuring means, Where these signals are'compensate'd, whereby the long term variations of the measuring signal which are due to disturbing influences on said measuring device are eliminated.

Both a method and apparatus as will become heretofore more apparent are provided embodying the instant inventive concept.

The specific structural details of several embodiments of the invention, and their mode of functioning will be made most manifest and particularly pointed out in clear, concise, and exact terms in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic representation of the drafting zone of a textile machine, showing the novel control apparatus schematically as arranged in combination therewith;

FIG. 2 is a diagrammatic illustration of another embodiment of the control apparatus in which the position converting means are embodied in a potentiometer forming part of an electrical bridge;

FIG. 3 is an alternative embodiment of the invention in which the position converting means is embodied in a tuning condenser;

FIG. 4 illustrates an embodiment of the invention in which the measuring means are of an optical nature;

F IG. 5 is a schematic detail view similar to FIG. 1 showing more clearly the mechanical inter-relationship between the components, and 7 FIGS. 5:: and 5 b show respectively a series and parallel circuit for compensator 2. 7

Referring now more particularly to the drawings, like numerals will be employed to designate like parts.

In the embodiment of the invention illustrated in FIGS. 1 and 5, measuring means in the form of a condenser 1 are positioned to measure the material passing into the drafting area of textile spinning apparatus S. Condenser 1 is electrically coupled to compensator 2 which comprises an electrical network. The output of this compensator 2 is fed through schematically illustrated amplifier A where the signal is ampliled and fed to a drive 4 in which the electrical energy output of amplifier i 3 3 is converted into rotational mechanical energy for driving a pair of variable speed drafting rolls 5 and 6.

A pair of drafting rolls 7 and 8 are driven at a relatively constant speed, and the material 9 to be drafted is fed through measuring device 1, the constant speed rolls 7 and 8, and variable speed rolls 5 and 6 as illus trated.

The angular speed of the variable speed drafting rolls 5 and 6 is transmitted through gear 10 to reduction gear 11 to differential gear 12. It will also be observed that constant speed rolls 7 and 8 are also coupled through gearing to differential gear 12. Differential gear 12 is mounted for rotation in cage 12. Cage 12' may rotate about an axis perpendicular to the axis of gear 12, and as is apparent from FIGS. 1 and 5 is free to rotate on the shafts extending between reduction gear 11 and its associated bevel gear in the cage; and the unidentified pinion at the left and its associated bevel gear in the cage, cage 12' being fixedly secured to pinion 13 which rotates therewith. Any movement of the cage 12' of differential gear 12 is transmitted through pinion 13 to gear 13, the angular speed of which is transmitted through

spur gears

14 and 15 to position converting means in the form of potentiometer 16 in which slider arm 17 assumes a position between

terminals

18 and 19 of the potentiometer.

Stops

20 and 21 arranged respectively adjacent opposite terminals of the potentiometer 16 limit the movement of slider 17. These

stops

20 and 21 are preferably made in the form of limit switches forming part of a subsidiary circuit (not shown) which controls an alarm signal indicating the existence of a long term disturbance.

Phase shifter 30 is arranged in the circuit leading from measuring condenser 1 to compensator 2. Phase shifter 30 is essentially an R-C network which lags the measuring signal from the condenser for a purpose to be made hereinafter more apparent.

A tacho-generator 31 is coupled to the shaft of gear 13 whereby the rotational energy of gear 13 is transmitted in the form of electrical energy to compensator 2 to form a closed servo-loop.

In the embodiment'of the invention illustrated in FIG.

2, the position converting means in the form of potentiometer 16 is arranged with

terminals

18 and 19 directly in the circuit of measuring condenser 1 (rather than across an independent voltage source as in the FIGS. 1 and 5 arrangement) along with measuring bridge 26. The bridge voltage resulting from this arrangement is applied directly across phase shifter 30, the output of which is fed to amplifier 3. I In the embodiment of the invention illustrated in FIG. 3, potentiometer 16 is replaced by tuning condenser 22 the capacity of which is variable by means of rotor arm 23 which is coupled to rotate with gear 15. In this embodiment of the invention, the combination of tuning condenser 22 and, measuring plate condenser 1 forms the compensator 2. The output of the compensator 2 as formed .by the combination of tuning condenser 22 and plate condenser 1 is fed through phase shifter 30 to amplifier 3 as in the FIG. 1 embodiment.

In the embodiment of the invention illustrated in FIG. 4, the measuring means employed are of an optical nature comprising a radiation source 28 and radiation receivers 24 and 29. The amount of radiation passing from source 28 to receiver 24 is variable by means of scanning aperture which is coupled to gear wheel 15 so that the position of gear wheel 15 determines the amount of screening effected by aperture 25, while the amount of radiation passing to receiver 29 is determined by the material 9.

' Element 2 in FIGS. 3 and 4 serves as a compensator.

Operation 4, tion. As most fully illustrated in FIGS. 1 and 5, a ma terial 9 such as a textile material is drawn through the measuring device 1 by means of a pair of constant speed drafting rolls 7 and 8 turning at a constant angular speed 11 A measuring signal U proportional to the weight of the material in said measuring device at any given instant is fed through time delay circuit 30 to compensator 2. Additionally, an electrical signal U is fed from the position converting potentiometer 16 to the compensator 2. The compensator provides as an output difierential signal U representing the differential between signals U and U Differential signal U is fed through amplifier 3 where it is amplified and delivered to drive 4.

Drive 4 drives variable speed rolls 5 and 6 at an angular speed n which averages approximately 10 to 50% higher than the constant angular speed n of the pair of constant speed rolls 7 and 8. This average angular speed n is that speed at Which the desired drafting of material 9 takes place.

Upon the occurrence of an increase in weight per unit length of the material 9 above the desired average value, measuring signal U from measuring device 1 is increased producing an increased output U from compensator 2 and a corresponding increase in the speed of drive 4 and speed 11 of the pair of variable speed drafting rolls 5 and 6. With this increase in speed the material is drafted down to desired thickness.

If on the other hand the weight of the textile material 9 becomes less than the desired average value, the measuring signal U is reduced, with a corresponding decrease in the electrical energy fed to drive 4, and a resultant decrease in speed n of variable speed drafting rolls 5 and 6. This decrease in drafting roll speed provides less draft and the material increases in weight.

By means of

gears

10 and 11, the variable angular speed n of the pair of drafting rolls 5 and 6 is transformed to a first variable angular speed 11 This angular speed in represents the angular speed 11 of variable speed drafting rolls 5 and 6 reduced by a drafting factor or the change of speed of variable speed rolls 5 and 6 necessary to provide the proper draft of the material to produce the desired average weight. Thus when the desired average draft is obtained, the angular speed n is equal to the angular speed 11 This variable angular speed 11 and the angular speed n are both imparted to differential gear 12 functioning as a subtracter. It will be obvious to those skilled in the art that the same subtracting function may be accomplished by means of a planetary gear or the like; The cage 12' of gear 12 and the pinion 13 which is driven by said cage 12' remains stationary so long as the angular speeds 12 and n are equal. Upon a change of angular speed 12 with respect to the angular speed n gear cage 12 is rotated at angular speed n causing pinion 13 to change the position of slider arm 17 of potentiometer 16 through spur gears 14 and 15, the output of which has an angular speed 11 Thus potentiometer 16 will permit an electrical signal U to pass to compensator 2, said electrical signal U being determined by the position of cage 12'. Potentiometer 16 thus serves as position converting means.

Spur gears 14 and 15 serve to reduce the motion trans mitted from cage 12 so that slider arm 17 is limited in its motion. The magnitude of the reduction ratio effected by

spur gears

14 and 15 determines the time factor required for readjustment of average material thickness, and should therefore be adjustable, as will become hereinafter more apparent. This time factor is obtained so as to compensate for the time required to move slider arm 17 which, as will be apparent, varies depending on the reduction between the angular speed differential n; which is assumed to be constant and the reduced angular speed differential u The voltage across potentiometer 16 between its

terminals

18 and 19 has a magnitude U The voltage between arm 17 and terminal 19 has a magnitude U which as previously mentioned is fed to compensator 2. The angle a subtended by arm 17 between terminal 19 and the arm 17 will be variable by over curve 01 A0:

U is related to U in the following manner:

During start-up arm 17 is positioned in such a Way that signal U corresponds in magnitude to that of measuring signal U Thereafter arm 17 follows the movements of pinion 13. There is a slight time delay between the positioning of arm 17 through Act. This tangle Ac: represents the integrated value of the angular speed 71 over the time interval At: 1 -4 namely:

The signal U as noted is fed to compensator 2.

During normal undisturbed operation, the variations in Weight of textile material 9 produce short and medium term variations above and below the average value of measuring signal U The resultant differential produces a variation in output signal U from compensator 2 which as previously discussed serves to vary the speed of variable speed rolls 5 and 6.

If a long term disturbing influence occurs, measuring signal U changes positively with respect to signal U with the result that a positive output signal U is emitted from compensator 2 producing an increased angular speed in drafting rolls 5 and 6. This produces motion of cage 12' causing arm 17 to move through an angular displacement Au whereby the magnitude of signal U increases. It the long term disturbing influence continues then arm 17 eventually reaches stop 20 and will actuate a suitable alarm device, either lights, a stop motion, or an audible signal.

Phase shifter 36 is provided to interpose a time delay between the transmission of signal U from the measuring device to the compensator so that the compensating action provided by a variation in material thickness will not begin to take place until that portion of the material which produced the measuring signal U will have passed from the measuring zone to the drafting zone between rolls 7 and 3, and 5 and 6 respectively.

The linearity of control characteristics is improved by provision of tacho-generator 31 which serves to provide a closed circuit servo-loop in which the feed back signal U generated by tacho-generator 31 which is proportional to the differential angular speed In serves to eliminate the efiects of drafting roll torque on the angular speed n The reversible rotation of gear 13 and tacho-generator 31 constitutes a conventional velocity closed loop servomechanism. The signal U is dependent upon the direction and speed of rotation or velocity of gear 13, and thus of cage 12 of the differential gear. This signal U is fed back to the compensator 2 in opposition to the first electrical signal U from measuring device 1.

In the operation of the alternative embodiments of the invention, substantially the same functions are attained. As previously noted merely minor substitutions of components has been provided.

In the FIG. 2 embodiment, the position of potentiometer slider arm .17 directly determines bridge switching, so that the effect of long term variations is compensated. In the FIG. 3 embodiment, the long term variations of signal U are compensated by a change in the setting of condenser 22 while short term variations produce a desired drafting change.

In the embodiment of FIG. 4 the screening effected by aperture 25 in response to long term variations, as indi- 6 cated by movement of gear 15, modifies the signal passing to compensator 2.

It is thus seen that a novel means of automatically controlling the drafting of materials has been provided in which long term variations and short term variations are all accommodated, and any inertial effects, or the like of the mechanism, are substantially mitigated in the control action.

The above disclosure has been given by way of illustration and elucidation and not by way of limitation and it is desired to protect all embodiments of the invention within the scope of the appended claims.

What is claimed is:

.1. Means for controlling material drafting operations between a first pair of drafting rolls and a pair of variable speed drafting rolls, said means comprising: measuring means positioned before said first pair of drafting rolls to detect variations in the material passing thereto; compensating means to which a signal from said measuring means is fed; subtracting means coupled to the drafting rolls providing a signal indicative of the difference in angular speed between that of the first pair of drafting rolls and the variable speed drafting rolls, the difierence signal being fed to said compensating means; reducing means interposed between the variabie speed drafting rolls and said subtracting means and means directing a control signal from said compensating means to a drive for said variable speed drafting rolls, whereby the long term variations due to disturbing influences on the measuring means are eliminated.

2. Means for controlling material drafting operations between a first pair of drafting rolls and a pair of variable speed drafting rolls, said means comprising: measuring means positioned before said first pair of drafting rolls to detect variations in the material passing thereto; compensating means to which a signal from said measuring means is fed; subtracting means coupled to the drafting rolls providing a signal indicative of the difference in angular speed between that of the first pair of drafting rolls and the variable speed drafting rolls, the difference signal being fed to said compensating means, generating means coupled to said subtracting means to produce a signal indicative of the correction of drafting roll speed, said signal being fed to said compensating means and means directing a control signal from said compensating means to a drive for said variable speed drafting rolls, whereby the long variations due to disturbing influences on the measuring means are eliminated.

3. Means for controlling material drafting operations between a first pair of drafting rolls and a pair of variable speed drafting rolls, said means comprising: measuring means positioned before said first pair of drafting rolls to detect variations in the material passing thereto; subtracting means coupled to the drafting rolls providing a signal indicative of the difference in angular speed between that of the first pair of drafting rolls and the variable speed drafting rolls, compensating means to which the last named signal, along with the measuring signal are fed; time delay means interposed between said measuring means and said compensating means for delaying the signal from the former in its passage to said compensating means; reducing means interposed between said variable speed drafting rolls and said subtracting means; tacho-generating means coupled to said subtracting means to produce a signal indicative of the correction of drafting roll speed, said signal being fed to said compensating means; and means directing a control signal from said compensating means to a drive for said variable speed drafting rolls, whereby the long term variations due to disturbing influences on the measuring means are eliminated.

4. Control apparatus for regulating material drafting operations between a first pair of drafting rolls and a pair of variable speed drafting rolls, said apparatus comprising: a measuring device position before said first pair of drafting rolls to 'detect variations in the material passing thereto; a compensator electrically coupled to said measuring device receiving measuring signals therefrom;

a position converter coupled to said subtracter providing an electrical signal indicative of the difference obtained from the subtracter, said signal being fed to said compensator; and an amplifier coupled to said compensator from which a control signal is fed to the drive for said variable speed drafting rolls.

5. Apparatus as in claim 4 in which a phase shifter is interposed between said measuring device and said compensator to delay the transfer of the electrical signal from said measuring device, whereby the material will be in the drafting zone at the time the control signal has effect.

6. Apparatus as in claim 4 in which a tacho-generator is coupled to said subtracter and the output of said generator is fed to said compensator, whereby inertial effects will be minimized.

7. Apparatus for automatically controlling drafting systems to prevent faulty control actions due to long term disturbing influences, said apparatus including a first pair of rolls operating at speed 11 and a second pair of variable speed drafting rolls operating at speed n said apparatus comprising: a mechanical subtracter in which the difference between an angular speed m of a gear rotating at a speed proportional to the variable angular speed n and angular speed n is determined; position converting means to which the output 12 of the subtracter is fed, reduced by a gear to speed 12 said position converting means producing an electrical signal U a meas uring device arranged to measure. the material being fed to the drafting rolls, said device producing a measuring signal U a compensator to which the measuring signal U and signal U are fed, said compensator delivering a control signal U; for controlling operation of the variable speed rolls, whereby long term variations of the measuring signal U produced by the measuring device due to distrubing influences on said measuring device are eliminated.

8. Apparatus as in claim 7 in which a tacho-generator is arranged in combination with said subtracter, and a signal from said tacho-generator is lead to the compensator, whereby load variations will have minimal efiect on control operation.

9. Apparatus as in claim 7 in which the position converting means comprise a potentiometer.

r10. Apparatus as in claim 7 in which the measuring device comprises an electromagnetic radiation source; a sensing member; and means for screening the radiation.

11. Apparatus as in claim 7 in which said position conv'erting means include a tuning condenser.

References Cited in the file of this patent UNITED STATES PATENTS 2,812,553 Coulliette Nov. 12, 1957 2,843,882 Lewis et a1. July 22, 1958 2,930,084 Sanborn et a1 Mar. 29, 1960

Claims

1. MEANS FOR CONTROLLING MATERIAL DRAFTING OPERATIONS BETWEEN A FIRST PAIR OF DRAFTING ROLLS AND A PAIR OF VARIABLE SPEED DRAFTING ROLLS, SAID MEANS COMPRISING: MEASURING MEANS POSITIONED BEFORE SAID FIRST PAIR OF DRAFTING ROLLS TO DETECT VARIATIONS IN THE MATERIAL PASSING THERETO; COMPENSATING MEANS TO WHICH A SIGNAL FROM SAID MEASURING MEANS IS FED; SUBSTRACTING MEANS COUPLED TO THE DRAFTING ROLLS PROVIDING A SIGNAL INDICATIVE OF THE DIFFERENCE IN ANGULAR SPEED BETWEEN THAT OF THE FIRST PAIR OF DRAFTING ROLLS AND THE VARIABLE SPEED DRAFTING ROLLS, THE DIFFERENCE SIGNAL BEING FED TO SAID COMPENSATING MEANS; REDUCING MEANS INTERPOSED BETWEEN THE VARIABLE SPEED DRAFTING ROLLS AND SAID SUBTRACTING MEANS AND MEANS DIRECTING A CONTROL SIGNAL FROM SAID COMPENSATING MEANS TO A DRIVE FOR SAID