US3300161A

US3300161A - Control device

Info

Publication number: US3300161A
Application number: US398001A
Authority: US
Inventors: Hermanns Peter
Original assignee: FRAU SIGRID HEIM
Current assignee: FRAU SIGRID HEIM
Priority date: 1963-09-21
Filing date: 1964-09-21
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

Jan. 24, 1967 P. HERMANNS 3,300,151

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 1 Fig.2

180 ANBLEO PRUGRESSIVELY BETTING SMALLER APPRUXIMATION OF THE CURE TU FIELD SHUNT POSITION INVENTOR: PETER HERMANNS BY /6ruw-wc 5 42 v ATTORNEYS Jan. 24, 1967 P. HERMANNS 3,300,161

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 2 INVENTOR: PETER HERMANNS BY A Jw/WL ATTORNEYS Jan. 24, 1967 P. HERMANNS 3,300,161

CONTROL DEVICE Filed Sept. 21, 1964 4 Sheets-Sheet 5 INVENTOR:

PETER HERMANHS y A mot c 4 ATTORNEYS a Jan. 24,

Filed Sept. 21, 1964 P. H ERMANNS CONTROL DEVICE 4 Sheets-Sheet 4 INVENTOR= PETER HERMAHNS BY 6,6114% g A! ATTORNEY Patented Jan. 24, 1967 3,300,161 CONTROL DEVICE Peter Hermanns, Cologne, Germany, assignor to Frau Sigrid Heim nee Krukenberg, Cologne-Zollstock, Germany Filed Sept. 21, 1964, Ser. No. 398,001 Claims priority, application Germany, Sept. 21, 1963, H 50,326; Mar. 20, 1964, H 52,108 Claims. (Cl. 242154) The present invention relates to an electrical control arrangement for thread or yarn tension devices of textile machines, particularly spooling or winding machines, wherein the yarn passes between two guide elements which are movable relative to each other and tension the yarn by braking it.

As is known, the yarn is kept under a certain tension by means of a tensioning device or yarn brake during a spooling process. Particularly when winding synthetic fibers, it is important that a uniform or otherwise predetermined yarn tension be achieved at the yarn. A lengthwise deformation of the yarn because of too high a take-up tension, as well as tension fluctuations which are too large during the spooling process are very much dreaded, since such yarns which are not wound with a uniform or fixedly predetermined yarn tension lead perforce to rejects during the subsequent processing when the yarn is knitted, etc.

Various apparatus have already been known in order to regulate the yarn tension during the processing on textile machines, or to keep the yarn tension at a predetermined value. In these known yarn tension regulating devices, lattice or grid braking, disk braking, friction braking, or similar braking systems are utilized which provide the yarn with the desired tension during its path through the redrawing or processing steps, the yarn it self being more or less braked and thus put under tension by variable friction when passing the braking system. The factors determining the yarn pull and thus the friction within the braking system are automatically controlled in dependence upon the yarn tension so that a yarn tension difference with respect to a preselected normal yarn tension, which may occur at times, and which arises from the feed, is automatically compensated for.

Sensing and thus a measuring or control of the yarn tension present at a particular time is thus the starting point for all control and regulating processes. These control and regulating processes are carried out electrically, so that an electrical value is provided by the sensing system as the tension setting value.

In order to transfer the mechanical value of the yarn tension upon electrical elements, generally at first the pulling force or elastic force directly derived from the yarn tension is compared with an elastic force effective oppositely thereto. For this purpose, sensing fingers or movable yarn guide eyes are normally provided which are pretensioned by means of spring forces or magnetic forces and which counteract the yarn tension. It is also possible to provide guide pins or rollers which transmit a motion dependent upon the yarn pull to the electric elements in various manners. In order to provide as smooth a translation of the mechanical adjusting value into an electrical adjustment value as possible, there have already been proposed bridge bolometers, photoelectric as well as capacitive or also inductive devices, or also low-friction adjustable resistors or potentiometers.

With these features of the prior art in mind, it is a main object of the present invention to provide an electromagnetic yarn tension sensing and regulating device for thread braking systems which is endowed with special advantages and improvements as compared to known devices.

Another object of the invention is to provide a yarn sensing device which is constructed so that a control and regulating can be used with it which does not require compensation circuits in the regulating circuitry.

These objects and others ancillary thereto are accomplished in accordance with preferred embodiments of the invention wherein control device is provided with three guide elements which are arranged to form a triangle so that the yarn passed therethrough forms a so-called yarn triangle. At least one yarn guide element, pref erably the guide element in the center, is mounted to be movable at right angles to the path of the yarn. On account of the yarn passing around the yarn guide elements along a triangular path, there arises a force component from the pulling force effective at the yarn in the direction 'of travel. This component is effective at right angles to the path of the yarn and exerts an adjustment moment upon the movable yarn guide element, so that the forces becoming effective through the yarn tension tend to straighten out the triangle and to bring the yarn into a straight line.

According to the invention, an electromagnetic pulling force is effective upon the movable yarn guide element of the triangle, which force is opposite to the partial component derived from the yarn tension in the direction of motion at right angles to the path of the yarn.

If both forcesthe magnetic pulling force and the component from the yarn tensionare of the same magnitude, the system assumes a rest position. If one of the two forces predominates, there is a momentary shift into the one or the other direction, until the force relationship is balanced. With the shift of the movable yarn guide element there is connected the shifting of an electrical element in order to deliver a setting or adjustment value for an electrical yarn brake or tensioning device.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic view of a yarn triangle device.

FIGURE 2 is a graph showing the relationship of yarn angle to a component of the yarn pulling force.

FIGURE 3 is a schematic view of a yarn triangle device using an electromagnetic device and a photoelectric device.

FIGURE 4 is a graph showing the relationship of the force of magnetic attraction or magnetic pulling force to the position of the core with respect to the coil.

FIGURE 5 is a graph showing the curves of FIGURES 2 and 4 plotted on the same scale.

FIGURE 6 is a side elevational view, partly in section, of a winder.

FIGURE 7 is a front elevational view of the yarn sensing device.

FIGURE 8 is a plan view of the yarn sensing device of FIGURE 7.

FIGURE 9 is a front elevational view of the yarn braking or tensioning device.

FIGURE 10 is a circuit diagram of the control for the yarn tensioning device.

FIGURE 11 is a circuit diagram of a simplified potentiometer-type arrangement for varying the yarn tension.

FIGURE 12 is a circuit diagram similar to FIGURE 11 but arranged to degressively decrease yarn tension with increasing spool diameter.

FIGURE 13 is a schematic view of a yarn triangle device using a condenser instead of a photoelectric device.

FIGURE 14 is a schematic view of a yarn triangle device using a variable inductor.

FIGURE 15 is a schematic view of a plurality of coils 3 in electric circuits which are commonly controlled by a control device.

Before considering the drawings in detail, the sequence of the control steps of a known device will be considered.

The starting point of this consideration is to be an equilibrium of the entire control and tension system, with an assumed yarn tension of the value X. Yarn tension and electromagnetic force are equal, so that the yarn sensing system remains at rest in a certain position. The electrical element coupled with the momentary position of the movable yarn guide element delivers in this setting a certain electrical value to the yarn tensioning device, as the setting value. This setting value causes a setting of the tension device so that a yarn tension of the assumed value X is reached.

Furthermore, it is assumed that now from time to time a yarn tension difference having the value Y occurs, caused by the feed. This yarn tension difference of the magnitude Y which follows the state of equilibrium with the yarn tension having a value X, causes a shift of the movable yarn guide element against the fixedly set electromagnetic force. With this shift, there is also connected the shifting of the electrical element so that now a setting value is delivered to the tension system which is capable of adjusting the tension system such that a compensation of the yarn tension difference, which has occurred for a time, is carried out.

With progressive compensation of this assumed yarn tension difference, the yarn tension naturally approaches again the initial value, i.e., the value X. With the ap pr-oach of the yarn tension to the starting value, however, there is perforce connected an adjustment of the movable yarn guide element and, with it, of the electrical element, to the starting point of the regulating processes. However, in this starting position, a setting value is delivered to the tension or bracking system by the electrical element which value corresponds to the normal feed tension of the yarn. If the interference which causes the yarn tension difference having the value Y continues, the yarn tension difference having this value occurs again and the abovedescribed process is repeated. The setting value necessary for completely covering the yarn tension difference Y is consequently always lost with progressive compensation of the temporarily occurring yarn tension and after every completed compensation, a setting value is delivered by the electrical element, which value corresponds to the yarn tension difference which is still present.

It can thus be seen that the setting value which is delivered by the electrical element to the brake system is consequently subject to variations during the entire duration of the yarn tension difference having the value Y. Therefore the setting value varies between the value which corresponds to the normal feed tension having the value X in the starting position and the value which corresponds to the occurring yarn tension difference Y. In practice, only a compensation of about 50% of the difference occurring from time to time is possible with such a control or regulating apparatus.

In order to compensate completely for a yarn tension difference, a substantially more complicated regulating circuit is required. It is necessary, in this connection, to carry out a compensation within the entire regulating circuit, perhaps such that a second yarn tension sensing device is inserted between feed and tension system which yields a compensation tension which strengthens or weakens the electromagnetic field of the first yarn tension sensing device in accordance with increasing or decreasing feed tension, so that the setting value present when the yarn tension difference with respect to the predetermined actual value occurs at the first moment of the regulating processes is maintained. There are still other ways possible to derive electrical compensation values from the entire regulating circuit for example from the relative position of the tension system, and to feed these values into the regulating circuit in such a manner that a complete yarn tension regulation is made possible. Such regulating circuits are extraordinarily complicated and expensive, and it is dilficult to maintain the necessary regulating characteristics across the required range.

In contradistinction thereto, the device according to the invention makes possible a complete compensation of an occasionally occurring yarn tension difference, Without an additional application of a compensation value being necessary.

The force component arising in the yarn triangle at right angles to the direction of motion of the yarn is, in addition to being dependent on the pull tension at the yarn in the direction of motion, dependent upon the relative position of the three yarn guide elements with respect to one another, i.e., with increasing yarn angle within the yarn guide elements of the yarn sensing device, the component which is effective at the central yarn guide element at right angles to the path of the yarn becomes smaller.

With more particular reference to the drawings, FIG- URE 1 schematically shows a yarn triangle device. Yarn 10 passes through the yarn guide elements 11, 12', and 13 arranged in a triangle with respect to one another, and forms an angle a. The yarn 10 extends in the direction of motion indicated, the force K becoming effective as a pulling force. In this position of the yarn guide elements with respect to one another, a force component K is effective at the central yarn guide element 12, this force extending in the direction indicated. When the central yarn guide element is shifted into the position shown in dashed lines, the angle at becomes larger, as can be seen from FIGURE 1. The component K, however, is smaller in this position, the pulling force K at the yarn in the direction of motion being the same.

FIGURE 2 shows schematically in a graph the relationship between the component K and the yarn angle oz. The graph shows that, at the yarn angle of the component K is practically zero, and that the component increases, with decreasing yarn angle, approximately according to the curve as illustrated.

According to the invention, at least one of the yarn guide elements arranged in a triangle is mounted to be movable at right angles to the path of the yarn and is under electromagnetic pulling force in the direction of motion.

FIGURE 3 shows an embodiment of such an arrangement wherein the central yarn guide element is movably mounted. The yarn 10 is guided along the

yarn guide elements

11, 12 and 13. The movable yarn guide element 13 is connected with the magnetic core 14 which moves into the field of a coil 15. At the connecting member 16 which connects the movable yarn guide element 12 with the magnetic core 14, there is connected a light vane 17 which covers a photoelectric cell 18 partially on the active layer against light in a direction at a right angle to the plane of the drawing.

If the magnetic coil 15 is energized with a current, the magnetic field exerts a certain force upon the armature 14, this force being dependent, if the passage of current is constant, substantially upon the relative position of the core 14 with respect to the field of coil 15. The attractive force becomes progressively greater during the approach of the armature into the so-called field shunt position and becomes smaller when the armature moves progressively farther away from the field of the coil.

FIGURE 4 shows, graphically, the relationship between the relative position of the core with respect to the magnetic coil and the force of magnetic attraction or pulling force P resulting therefrom. The graph shows that the force P increases in accordance with the course of the curve illustrated and assumes its highest value in the field shunt position.

The essential feature of the invention is that the two oppositely effective forces from the yarn triangle and from the electromagnetic field are balanced with respect to each other by suitable geometric and mechanical adjustment of the yarn triangle to the dimensioning and arrangement of the electrical magnitude of the electromagnetic field, and by suitable choice of the characteristic of the path-field strength relationship. This balancing is done such that the curve paths of the two forces according to FIGURES 2 and 4, as shown in FIGURE 5, are substantially congruent along a portion of their path. If the two opposite forces along this portion of the curve of the diagram according to FIGURE 5 are effective between the points a and b, there is a complete force equilibrium and the sensing device is in a rest position. Within the region between points a and b, the component from the yarn tension decreases or increases, when the movable yarn guide element is shifted, to the same extent to which the oppositely effective magnetic force also decreases or increases, this force arising from the concomitant, equally large shift of the magnetic armature with respect to the magnetic field of the coil.

With such a yarn sensing device constructed according to the invention, a control and regulating device for yarn tension devices can be operated without complicated regulating circuits with compensaton circuits being necessary.

Similar to the consideration of the regulating processes in the foregoing description, there shall again be considered an equilibrium of the entire regulating system as the starting point, with an assumed yarn tension of the magnitude X. Yarn tension and electromagnetic force are the same so that the yarn sensing system remains at rest in a certain position. The light vane 17 covers the photoelectric element 18 to a certain extent, so that a setting value is delivered from this element to a subsequent amplifier circuit. This setting value exerts such an influence upon the yarn tension device which is connected to the amplifier output, that the tension device assumes a setting which results in a yarn tension of the assumed magnitude X.

Furthermore, it is assumed that now an occasional yarn tension difference of the magnitude Y occurs which is caused by the feed. This yarn tension difference of the magnitude Y, following the equilibrium condition having the yarn tension of the magnitude X, causes a shift of the equilibrium and thus a shift of the movable yarn guide element. With this shift, there is also a corresponding shift of the light vane 17, so that the photoelectric element receives a different amount of light and thus a correspondingly different setting value is delivered to the tensioning system via the amplifiers. This setting value adjusts the tension system such that a compensation of the occasional yarn tension difference is carried out. With the progressive compensation of this assumed yarn tension difference by means of the progressive change in the braking action, the yarn tension naturally again approaches the starting value, namely the value X.

On account of the occurrence of the yarn tension difference, the movable yarn guide element and with it the magnetic core were shifted as the equilibrium of the forces was disturbed. When the yarn tension difference is completely compensated for, there is again an equilibrium in the described arrangement between the force component from the yarn triangle device and the oppositely effective force from the electromagnetic system, although the basic setting has changed with respect to the initial setting, because, with the same pulling force at the yarn along a certain adjustment range of the sensing device, the equilibrium is maintained, as can be seen from the above explanations in connection with FIGURE 5. The light vane 17 thus has kept its setting which it assumed when the yarn tension difference occurred, this being different from the starting position of the operation, and the setting value which is now delivered by the photoelectric element fully compensates for the difference value which has occurred, so that with the device according to the invention a complete compensation of the occasionally occurring yarn tension difference is possible, without a complicated regulating circuit with restoration and compensation being necessary.

If, after these regulating processes have been completed, a further disturbing magnitude arises anew, for example a yarn tension difference in the opposite direction, there is momentarily again a shift of the movable yarn guide element and thus of the light vane. Thus, a changed setting value is delivered, and by adjusting the tensioning system, a compensation of the yarn tension difference is carried out. The yarn sensing system now assumes a different position, but at the moment of adjustment of the yarn tension to the starting point, there is again complete equilibrium.

By using a photodiode as the photoelectric element and by using a transistorized amplifier, connected thereafter, for the amplification of the setting value-and as described in more detail hereinaftersuch an amplification can be achieved that the relative total shift of the movable yarn guide element and the magnetic core can be limited in practice to fractions of a millimeter. By this means, very short adjustment paths and adjustment periods of the yarn sensing device can be obtained.

According to a further development of the invention, the flow of current through the winding 15 of the magnetic coil is controlled by means of a potentiometer-like circuit. The electoromagnetic basic setting is varied and the fixed output of a desired value for the desired yarn tension is made possible. This desired value is read either from a calibrated potentiometer or from an indicating device.

In the textile industry, it is almost always necessary to have a rather large number of winding machines in order to produce larger quantities of spools, cones, cheeses, quills, etc., at the same time. Greatest importance is given to the achievement of as uniform a yarn tension on all spools as possible. For obtaining this uniformity, a. great expenditure in operating personnel for the machines is required at present.

According to a further feature of the invention, as many yarn sensing systems as desired are combined electrically and are supplied with magnetizing current through a control circuit, for example by means of a control desk. In this manner, a central regulation of the amount of the yarn tension can be carried out. The choice of the magnitude of the yarn tension can be dependent upon the type of the yarn used.

For various reasons inherent on the one hand in the homogeneous construction of the spool itself and on the other hand in the technical requirements of the textile art during the further processing of the spools manufactured on the spooling machines, a degressive decrease of the yarn tension is desired with increasing spool diameter.

A further component of the inventive idea is thatthe electromagnetic field of the yarn sensing device is controlled in a second circuit or in a more detailed circuit of the first type which has been described above such that the flow of current through the winding of the magnetic coil 15 is influenced by a second potentiometer which is set in dependence upon the diameter of the take-up spool, for example, in dependence upon the position of the yarn guide flap. Thus, it is possible to achieve automatically, either step-wise or continuously, a yarn tension which decreases, for example, degressively.

By means of the inventive device, any type of control or regulation of the yarn tension can be carried out, i.e., not only the change of the braking effect by means of a yarn brake known per se with meshing guide elements or by changing the braking action of disc brakes, but it is also possible to influence an acceleration of the yarn passage.

The translation of the mechanical shifting movement of the yarn sensing system when a yarn tension difference occurs with respect to the preselected normal value, into an electrical setting value can be carried out in the most varied manner.

The photoelectric device shown in FIGURE 3 is only shown as an example for a device according to the invention. The movable yarn guide element can also be coupled with a capacitance, or inductance, or a potentiometer, or other electrical signal producing systems whose changes then serve as control basis for the regulating device of the yarn brake.

An embodiment of a control and regulating device constructed according to the invention for a yarn brake will now be described, together with the tensioning device itself and the electric circuit pertaining thereto.

FIGURE 6 shows the path of the yarn 10, from a bobbin or other yarn supply 20 via an electromagnetic tensioning system 21, yarn sensing system 22 to a take-up spool 23. From this figure, also the basic construction of the entire winding machine with drive motor and pivotable yarn guide can be seen.

As can be seen from FIGURE 7, the yarn triangle device which has been explained in detail in the foregoing is formed between the yarn guide pins 11 and 13 and the yarn sensing element. FIGURES 7 and 8 furthermore show the position of the magnetic coil 15, as well as the position of the light vane 17 arranged on a member 16b, which member also has the iron core 14 which moves into the magnetic coil I secured thereto. The connecting member 16 passes through the member 16b and has the yarn sensing member 12 arranged at the end thereof.

This light vane controls, depending upon the size of the yarn triangle, the amount of light from the light source 24 which reaches the photoelectric cell 18.

In the embodiment of a yarn sensing device shown in FIGURES 7 and 8, the yarn sensing element 12 is rotatably mounted with the stucture 16 at one end and thus is pivotable into a vertical line so that various angles can form within the yarn triangle during the operation of the device. In order that short tugs at the yarn cannot become effective and so that the control device is protected against undesired natural oscillation processes, hydraulic damping is provided. For this purpose, a vane 16a is provided which is connected to member 16. This vane operates as a damping element in a chamber which is filled with damping oil. The container is sealed against the pivotable connecting member 16 by means of a collar. The movement of the yarn sensing member 12 causes the member 16 to pivot which motion is then transferred to the member 16b resulting in a movement of the light vane 17 and the core 14 which are secured to the member. this light vane is adjusted with respect to the light source 24- and the photoelectric cell 18 such that during a motion the light beam is covered more or less, so that the photocell, in correspondence with the lighting, controls the amplifier connected thereafter to a greater or lesser degree.

The construction of the yarn tensioning system 21 (cf. FIGURE 6) which system is controlled by the yarn sensing system via an amplifier, is shown in FIGURE 9. The yarn is pulled through the tensioning grid comprising the stationary braking lattice 25 and the movable braking lattice 25a. The movable braking lattice 25a is fastened at the magnetic armature 26 so that the magnet armature is pulled into the coil when current is flowing through winding 27 and the braking lattice becomes narrower, and thus a larger friction is transmitted to the yarn. In order that the magnet armature 26 can operate without any frictional engagement with the interior of the winding or other components, this armature is fastened to supports 28 extending in the front and/ or in the rear, in transverse direction. These supports are fashioned as leaf springs and thus permit a shifting of the armature 26 in the axial direction. The magnet armature 26 is connected, via connection member 29, with a hydraulic damping device 30 which exerts such a damping upon the shifting of armature 26 that an overshooting of the displacement initiated by the yarn sensing device via the amplifier is avoided.

FIGURE 10 is a circuit diagram of the required control amplifier which is electrically connected to the output of the yarn sensing system and correspondingly amplifies the setting value delivered by the latter system. The amplifier feeds this setting value to the tensioning system.

The amplifier is fed with a preferably stabilized direct current voltage at inputs 31. This voltage arrives, via a suitable resistor, at the lamp 24 which controls the photoelectric cell 18. The quantity of light is controlled, as set forth above, by the respective position of the light vane 17. The photoelectric cell 18 lies in series with the

voltage divider resistors

32, 33 and 34. The base of transistor 35 is connected between the divider resistors 32 and 33.

The voltage potential between the resistors 32 and 33 varies in dependence upon the lighting condition of the photoelectric cell 18, so that the base of the transistor 35 which is there connected is likewise more or less controlled in dependence upon the lighting condition of the photoelectric cell. If transistor 35 becomes more or less conductive on account of a change in the base voltage at transistor 35, a varied potential likewise appears, at the

divider resistors

37 and 36, so that the transistor 38, in correspondence with the amplification factor of transistor 35 is likewise controlled to a greater or lesser degree. The winding of the tensioning magnet 27 lies in the output circuit of the transistor. This tensioning magnet 27 shifts the movable braking lattice 25a in correspondence with the passage of current set by transistor 38. Resistor 39 controls the minimal flow of current through the tensioning magnet, with transistor 38 being blocked, so that a certain setting of the braking lattice is maintained. Because of this, it is possible by means of the braking system, to generate a minimal yarn tension at the start of the machine before the yarn tension regulation has begun and thus the start of a proper winding operation is made possible. With the beginning of the regulating operation, the transistor 38 takes over the control of the flow of current through the winding of magnet 27.

A capacitor 40 in series with a variable resistor 41 is connected in parallel with the resistor 34 and the photoelectric cell. Thereby the voltage potential at the photoelectric cell has a time constant which can be changed by the variable resistor in accordance with requirements. This manner of connection serves for damping and prevents the occurrence of control oscillations.

The mode of operation of the device has already been explained in detail in the first part of this description. The yarn It) forms the yarn triangle between the yarn guide elements 11, 12 and 13 (cf. FIGURES 1, 3 and 7). A pulling force is effective at the central yarn guide element 12, which force is opposite to the force of the electromagnet 15.

Analogously to the explanation of the first portion of the description, the two oppositely effective forces are balanced or adjusted to each other by means of suitable geometric and mechanical adjustment of the yarn triangle to the path-field strength relationship of the

electromagnetic device

14, 15 operating in a middle region of the path-field strength curve (cf. FIGURES 4 and 5), such that a complete equilibrium of the forces is maintained across a required adjusting range of the yarn sensing element 12.

If this equilibrium is disturbed by the occurrence of a difference in yarn tension, a shift of the sensing element 12 takes place. With this shift, there is a change in lighting of the photoelectric cell 18. This cell effects a change of the amplification of the amplifier (cf. FIGURE 10) so that the tensioning device 21 is actuated correspondingly. After the yarn tension difference which occurred is compensated for by a varied setting of the tensioning system 21, the yarn sensing device and thus the entire regulating device is again in a state of equilibrium.

The flow of current through the electromagnet 15 and therefore its magnetic force, Within the yarn sensing systern 21, is important for the maintaining of a certain value of the yarn te sion. FIGURE 11 shows a simplified circuit diagram for setting a predetermined yarn tension. For this purpose, an electrical control desk 42 pertaining to the machine is provided. This control desk transforms the main voltage fed thereto into a direct current voltage of, for example, 24 volts. A potentiometer 43 with the slide 44 lies in the output of the control desk for preselecting the yarn tension. It can be seen that the potentiometer 43 is eflective as a voltage divider and that the electromagnet 15 receives a greater or lesser voltage, depending upon the setting of slide 44. Thus, the armature of the magnet 15 is pulled into the coil to a greater or lesser degree and the yarn triangle assumes a changed basic position so that the desired value for the desired yarn tension is provided. An indication of the preselected yarn tension can be obtained either by inserting a voltmeter in parallel with the electromagnet 15 or by transmitting the respective position of the slide 44 to a calibrated scale.

FIGURE 12 shows a circuit diagram similar to FIG- URE 11 for the automatic control of yarn tension which is varied with increasing winding diameter and which decreases degressively, for example. According to this circuit diagram, the slide 44 of the potentiometer 43 operates in conjunction with a subsequent potentiometer 45 with the slide 46. This potentiometer is located within the machine, as can be seen from FIGURE 6.

On the axis of rotation 47 of the pivotable yarn guide flap 48, a toothed gear 49 is positioned which mes-hes with a pinion 50. This pinion is seated on the axis of the potentiometer 45. If the diameter of the winding spool 23 is increased, the arm of the yarn guide flap is pivoted and is shifted, via the

cogwheels

49 and 50 of the slide 46 (cf. FIGURE 12) of the potentiometer 45, in such a manner that a lower voltage occurs at the output of the potentiometer. With decreasing voltage at electromagnet 15, a lower yarn tension is achieved.

Thus, it can be seen that a decreasing yarn tension can be obtained with the circuit of FIGURE 12 which is automatically controlled by the increasing diameter of the spool during the re-spooling process.

Instead of the photoelectric device,

parts

18, 17, one can useas the case may bea variable condenser 18a, FIGURE 13, or a variable inductor 18b, FIGURE 14.

The common control device, FIGURE 15, comprises, on principle, the common potentiometer 43 of desk 42. However, a multiple structure of potentiometers 45 and slides 46 will be necessary as shown for a set of coils 15.

It will be understood that the above description of the present invention is susceptible to various modifications,

changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A yarn tensioning device for textile machines comprising in combination: yarn guide means including a plurality of elements arranged to form a triangle and through which yarn passes, one of said elements being movable in a direction at right angles to the yarn path to be moved by a component of yarn pull in said direction so that there is a first force on said movable element in said direction; electromagnetic means connected to said movable element for providing a second force opposite to said first force; the curve of the path-pulling force relationship of said electromagnetic means being balanced with the curve of the path-pulling force relationship of the yarn guide means so that the two curves and thus the oppositely effective forces are congruent along a certain minimum path of the adjusting region of the device and an equilibrium of the forces is maintained at positions along this region with the yarn pull remaining the same; electrical means coupled with said movable yarn guide element so that when said movable element moves, a proportional change of an electrical value of said electrical means takes place; a yarn tensioning assembly; and an electrical circuit connected to control said assembly and connected to receive a signal from said electrical means which is significant of the change of the electrical value and which is a setting value for said assembly.

2. A device as defined in claim 1 wherein said electrical means includes a photoelectrical element and a light vane connected With said movable element.

3. A device as defined in claim 2 wherein said photoelectrical element is a photodiode.

4. A device as defined in claim 1 wherein said electrical means includes a capacitor whose capacitance varies with the movement of said movable element.

5. A device as defined in claim 1 wherein said electrical means includes an inductance circuit whose inductance varies with the movement of said movable element.

6. A device as defined in claim 1 wherein said electromagnetic means includes a winding and a circuit including a potentiometer for controlling the current in said winding for setting a predetermined yarn tension.

7. In combination, a plurality of yarn tensioning devices as defined in claim 1 wherein each of said electromagnetic means is provided with a winding, and further comprising an electric circuit into which said windings are combined for centrally controlling said windings and including a potentiometer, so that the flow of current through said windings may be controlled.

8. A device as defined in claim 1 comprising spool means onto which the yarn is to be Wound, and potentiometer means connected to sense the increasing diameter of said spool means and to control current in said electromagnetic means to decrease yarn tension with increasing spool means diameter.

9. A device as defined in claim 8 wherein said potentiometer means includes a rotatable potentiometer controlled by a yarn guide flap which pivots with increasing spool means diameter.

10. A device as defined in claim 9 wherein said rotatable potentiometer includes a pinion and said yarn guide flap includes a cogwheel meshing with said pinion whereby pivoting of said flap rotates said potentiometer.

References Cited by the Examiner UNITED STATES PATENTS 2,754,071 7/1956 Furst et a1 242--l 54 3,146,968 9/1964 Band 242-149 FOREIGN PATENTS 1,200,676 6/1959 France.

225,541 5/ 1943 Switzerland.

STANLEY N. GILREATH, Primary Examiner.