CN118497956A

CN118497956A - Method for controlling warp tension on textile machine and related textile machine

Info

Publication number: CN118497956A
Application number: CN202410080213.3A
Authority: CN
Inventors: 托马斯·韦伯
Original assignee: Yokob Mueller Ltd Frick
Current assignee: Yokob Mueller Ltd Frick
Priority date: 2023-02-14
Filing date: 2024-01-18
Publication date: 2024-08-16
Also published as: EP4417741A1

Abstract

The warp threads (3) are unwound from a supply unit (2) and move to a thread interlacing area (5) in which a textile product (6) is formed. A drag roller (8) pushes the textile product (6) away from the yarn interlacing area (5) to maintain a selected target advance speed Vtv. A braking action is effected on the warp yarn (3) upstream of the dragging roller (8) to provide a supply traction force SF along the warp yarn (3). Monitoring of the supply traction is effected on the basis of an instantaneous value DT of a drag torque applied by the drag roller (8). A target value SFtv of the supply traction is maintained during operation of the textile machine (1) by means of repeated control cycles, each repeated control cycle comparing the instantaneous value DT of the drag torque with a target value DTtv, which corresponds to the target value SFtv of the supply traction. The braking action is modulated to maintain the supply tractive effort SF at the target value SFtv.

Description

Method for controlling warp tension on textile machine and related textile machine

Technical Field

The present invention relates to a method for controlling warp tensioning on a textile machine, and a textile machine with warp assembly for carrying out such a method.

The present invention can be conveniently applied to a loom such as a sword mast loom, a jet loom, a water jet loom, a shuttle loom, a narrow band loom, etc., and a knitting machine, etc., in order to improve product quality by effectively controlling the tension of warp yarns moving toward a yarn interlacing area.

In the present disclosure, a "spool" means a spool, reel, beam, or other type of cylindrical body that carries a wire, yarn, or textile product wound into a coil around a generally cylindrical core. An "electric motor" means an electric induction motor, such as a DC motor, a brushless DC motor, an AC motor, or preferably an AC servo motor.

A "brake" may be a real brake, e.g. operated by friction, magnetic induction, etc., or a motor operated in a "brake mode", i.e. generating energy due to forced rotation of its rotor.

Background

Textile machines generally provide at least one supply unit, for example one or more supply spools or reels, from which warp yarns or threads are delivered towards a yarn interlacing area. At the yarn interlacing area, the yarn interlacing device is driven to form a textile product by interlacing warp yarns supplied from the supply unit, possibly inserting weft yarns and/or other yarns, depending on the type of machine and/or the desired textile pattern.

A drag drive system comprising drag rollers operates the textile product at or immediately downstream of the yarn interlacing area to pull warp yarns from the supply unit and move the textile product away from the yarn interlacing area. Downstream of the yarn interlacing area, the textile product is collected into a container or wound on a winding reel into superimposed loops.

Textile machines are typically actuated by at least one main electric motor, which is part of a drag drive system. The pulling action exerted by the rotating drag roller withdraws the warp yarn by unwinding the warp yarn from the supply unit and moving the unwound warp yarn longitudinally towards the yarn interlacing area.

The supply unit may comprise a plurality of reels from which the warp yarns are unwound under the action of the drag roller. A braking arrangement may be employed to maintain a desired supply traction along the warp yarn upstream of the yarn interlacing area. For example, known braking devices comprise an idle redirecting roller assembly that operates on warp yarn to detect warp yarn tension by means of a load cell detector. The braking unit acts on an unwinding drum or intermediate roller, which is engaged with the warp threads coming from the respective spool carried by the creel. The braking unit is driven in response to a signal provided by the load cell detector to adjust the braking action applied to the supply drum in response to a change in warp tension.

When a large reel or beam is used as the supply unit, a supply motor may be provided to rotate the supply unit forward in a direction that facilitates unwinding of the warp yarns. The supply motor is controlled by a tension roller acting on the warp yarn to maintain a desired supply traction along the warp yarn, for example by facilitating rotation of the supply unit when the supply tension exceeds a given threshold value.

Disclosure of Invention

The present invention aims to improve and simplify the known arrangements for monitoring and/or adjusting the tension of warp yarns during operation of a textile machine.

In this regard, the scope of the present invention is to improve upon the prior art, in particular by providing a method and an apparatus which enable the precise control specified above by means of a simplified and inexpensive arrangement.

More particularly, the present invention aims to propose an arrangement in which accurate tensioning control of warp yarns can be achieved without the need for load cells, tension rollers and/or other kinds of additional sensors, in order to achieve improved reliability and simplified construction.

An additional object of the present invention is to easily achieve an accurate real-time control of the tensioning of the warp yarn leading to the drag roller, even during operation of the textile machine.

According to the present application, the inventors have found that an accurate tensioning control of the warp yarn can be effectively achieved by detecting the instantaneous value of the torque transmitted to the dragging roller to determine the instantaneous value of the tensioning force applied to the warp yarn. The torque transmitted to the drag roller can be easily adjusted to maintain this torque at a desired target value corresponding to the desired target tension of the warp yarns.

More particularly, the invention relates to a method for controlling warp yarn tension on a textile machine, wherein: the warp yarn is unwound from the supply unit and moves longitudinally to reach the yarn interlacing area; a textile product comprising said warp yarns is formed at a yarn interlacing area; the drag roller engages the textile product adjacent the yarn interlacing area; a drag motor rotates the drag roller to push the textile product away from the yarn interlacing area; the drag controller electronically controls the drag motor to maintain a selected target forward speed Vtv of the textile product.

A braking action is effected on the warp yarn upstream of the dragging roller to provide a supply traction SF along the warp yarn itself.

Preferably, during operation of the textile machine, repetitive control cycles are implemented, each repetitive control cycle comprising:

acquiring an instantaneous value DT of the drag torque applied to the drag roller, or at least one parameter representative thereof;

an instantaneous value of the traction force SF, or a representative of the at least one parameter thereof, is determined as a function of the instantaneous value DT of the traction torque.

In another aspect, the present invention is directed to a textile machine comprising: at least one supply unit configured to carry warp yarns; yarn interlacing means acting at the yarn interlacing area for producing textile products by means of warp yarns supplied from the supply unit; a drag roller configured to engage the textile product adjacent the yarn interlacing area and push the textile product away from the yarn interlacing area; a drag motor acting on the drag roller to rotate the drag roller at a drag angular velocity, thereby pulling the warp yarn out of the supply unit and pushing the textile product away from the yarn interlacing area; a drag electronic control unit provided with a drag motor and configured to acquire a power supply current value of the drag motor; a drag controller configured to electronically control a drag motor to maintain a selected target forward speed Vtv of the textile product and to obtain an instantaneous value of a drag torque DT applied to the drag roller as a function of a drag supply current, or at least one parameter representative thereof; a brake acting on the warp yarn upstream of the dragging roller to provide a supply traction force SF along the warp yarn itself.

Preferably, the central processing unit is configured to determine the instantaneous value of the supply traction force SF, or the at least one parameter representative thereof, as a function of the instantaneous value of the traction torque DT.

The inventors have observed that the tensioning of the warp yarns leading to the yarn interlacing area is directly related to the instantaneous value of the moment exerted by the respective motor on the dragging roller.

For the purposes of the present invention and the claims, any value of the drag torque mentioned, such as the instantaneous value DT and the target value DTtv, is also meant to be made up of any parameter indicative of the drag torque value.

For example, the supply current of the drag motor may be considered as a representative parameter of the drag torque. Instead, the torque value applied to the drag roller is directly related to the supply current to the drag motor. Since the supply current value is generally representative of one of the input parameters for the operation of the textile machine, an accurate monitoring of the warp thread tension can be achieved without the need for an additional sensor device.

In at least one preferred embodiment, the present invention may also include one or more of the following preferred features.

Preferably, the at least one parameter indicative of the value of the drag torque is the value of the drag torque.

Preferably, the at least one parameter indicative of the value of the drag torque is the supply current of the drag motor.

Preferably, the target value SFtv of the supply traction SF is maintained during operation of the textile machine by means of said repetitive control cycles, each of which further comprises:

Comparing the obtained instantaneous value DT of the drag torque with a predetermined target value DTtv of the drag torque corresponding to the target value SFtv;

Increasing the braking action when DT < DTtv;

When DT > DTtv, the braking action is reduced.

The braking action and the variation of the drag torque compensate each other to prevent uncontrolled tensioning in the warp yarn, resulting in defects or quality changes in the textile product. The present invention thus allows for easy monitoring and adjustment of warp yarn tension during operation of the textile machine by continuously adjusting the desired tension to accommodate the drag torque in response to changes that may occur in any of all functional parameters during operation of the textile machine.

Preferably, each of the repetitive control cycles further comprises a modulation action for maintaining the supply tractive effort at the target value.

Preferably, the increase and decrease of the braking action is achieved simultaneously with the increase and decrease of the drag torque, respectively.

Preferably, each of the repetitive control cycles further comprises:

when DT < DTtv, driving the drag motor (9) to increase the drag torque;

when DT > DTtv, the drag motor (9) is driven to reduce the drag torque.

Preferably, driving the drag motor to increase and decrease the drag torque is accomplished by increasing and decreasing, respectively, the supply current to the drag motor.

Instead, the value of the supply current is proportional to the value of the drag torque.

Preferably, the supply traction force SF is dependent on the drag torque transmitted from the drag motor to the drag roller.

Preferably, the warp is pulled out of the supply unit by means of a drag roller.

Preferably, no tension is applied to the textile product downstream of the drag roller.

Preferably, a constant tension is applied to the textile product downstream of the drag roller.

Preferably, the central processing unit is configured to drive the brake modulation braking action so as to maintain the supply tractive effort at the target value.

Preferably, the comparator is configured to compare the obtained instantaneous value DT of the drag torque with a predetermined target value DTtv of the drag torque, which corresponds to the target value SFtv of the supply traction.

Preferably, the central processing unit is configured to actuate the brake to:

Increasing the braking action when DT < DTtv;

When DT > DTtv, the braking action is reduced.

This facilitates maintaining the supply tractive effort SF at the target value SFtv.

Preferably, the brake comprises brake pads which are configured to be urged towards each other by a braking force so as to act directly on warp yarns sliding therebetween by friction.

Preferably, the brake acts on at least one redirecting roller around which the warp yarn is wound for applying a braking force against the rotation of the redirecting roller.

Preferably, the brake is configured to resist rotation of the supply spool, roller or unwind roller of the supply unit.

Preferably, the brake is operated by friction or magnetic induction.

Preferably, the brake comprises an electric motor operated in braking mode which generates energy due to forced rotation of its rotor.

Preferably, the central processing unit is configured to actuate the brake by means of a brake controller comprising an actuator acting on the brake pads to adjust the braking force.

Preferably, the central processing unit is configured to drive the brake by means of a brake controller configured to adjust an electrical load applied to the motor operated in the braking mode to adjust the braking force.

Preferably, a display unit is provided, connected to the central processing unit, for displaying the instantaneous value of the supply traction force SF and/or any deviation thereof with respect to the set target value SFtv.

Drawings

Additional features and advantages will be made apparent from the detailed description of a preferred, but not exclusive, embodiment of a method for controlling warp tensioning on a textile machine and a loom assembled for carrying out such method, according to the present invention. This description will be set forth hereinafter with reference to the accompanying drawings, which are provided as non-limiting examples only, in which:

Fig. 1 schematically shows a lateral front view of an exemplary textile machine 1 equipped with a control system for implementing the method according to the invention;

Fig. 2 is a flow chart of the operating logic of a textile machine 1 implementing the tensioning control method according to the invention.

Detailed Description

In fig. 1, a textile machine 1 is generally indicated by reference numeral 1. For example, the textile machine 1 may be a sword mast loom, an air jet loom, a water jet loom, a shuttle loom, a narrow band loom, a knitting machine or other type of textile machine 1.

The textile machine 1 comprises at least one supply unit 2, for example in the form of at least one supply reel or roller, from which a plurality of warp yarns 3 are extracted when the supply unit 2 rotates about a respective unwinding rotation axis X2. If desired, the reels can be driven by a motor (not shown) which assists the unwinding of the warp yarn 3 to prevent it from being overstretched.

In a different embodiment not shown, the supply unit 2 may comprise a plurality of spools carried by a cradle. The motor-driven unwinding drum 4 can operate on the warp yarn 3 to rotate about the unwinding rotation axis X2 downstream of the creel, providing a positive supply of warp yarn 3 to prevent excessive tensioning.

The warp yarns 3 drawn from the supply unit 2 move longitudinally to reach a yarn interlacing area 5 (for example, a knitting area or a weaving area), wherein a yarn interlacing device (not shown) operates for producing textile products 6 from the warp yarns 3 supplied by the supply unit 2. For this purpose, warp yarns 3 may be joined to each other and/or to one or more weft yarns and/or other additional yarns in any known manner not disclosed herein as not forming part of the present invention. The yarn interlacing device may generally comprise or consist of a yarn guiding element cooperating with the oscillating member: the yarn interlacing device is not shown in the drawings, as it can be implemented in a number of different known ways, if desired.

The dragging unit 7 engages with the textile product 6 in the vicinity of the yarn interlacing area 5, i.e. at or immediately downstream of the yarn interlacing area 5. The dragging unit 7 comprises a dragging roller 8 acting on the textile product 6 to push it away from the yarn interlacing area 5. The drag roller 8 also produces a pulling action on the warp yarn 3 from the supply unit 2. In fig. 1, DD indicates the drag diameter defined at its outer surface by the drag roller 8, which is free from slipping phenomena on the textile product 6. The drag motor 9 is preferably connected to the drag roller 8 via a drag gearbox reducer 10, so as to rotate the drag roller 8 at a controlled angular speed and subject itself to a controlled drag torque DT. The towing motors 9 are conveniently controlled by respective towing electronic control units 11, which are capable of controlling the rotational speed, the supply current and/or other operating parameters of the towing motors 9. A brushless motor equipped with a drag electronic control unit 11 can be conveniently used as the drag motor 9.

The drag electronic control unit 11 is able to detect the rotation speed n9 of the drag motor 9 (i.e. its rotor) at any moment. Preferably, the rotation speed n9 is received as an input signal by the drag controller 12 in order to calculate the drag rotation speed n8 of the drag roller 8 based on the value of the drag transmission ratio i10 of the respective drag gearbox reducer 10, by:

n8＝n9/i10。

The drag controller 12 may be embedded within the drag electronic control unit 11 or separate therefrom, for example as part of a central processing unit CPU that supervises the operation of the entire textile machine 1 or related parts thereof as shown in fig. 1.

The textile product 6 moving from the yarn interlacing area 5 is pushed towards a collecting unit 13. In a preferred embodiment, the collection unit 13 is such that no tension or a substantially constant tension WF is applied to the textile product 6 downstream of the dragging roller 8. This collecting unit 13 can be obtained in many different ways, which are not relevant to the scope of the invention, for example it can comprise a motor-driven winding reel, or consist solely of a collecting box assembled to receive the textile product 6.

During operation of the textile machine 1, the dragging roller 8 pushes the warp yarn 3 and the textile product 6 at a selected target advancing speed Vtv, which can be set by the central processing unit CPU, for example by the user via the input interface 14 or selected from a stored menu. The target forward speed Vtv is then controlled and/or maintained by the drag controller 12, such as by PID or other suitable control loop logic, by adjusting the rotational speed n9 of the drag motor 9 such that the rotational speed n8 matches the target forward speed Vtv, as:

Vtv＝n8*DD*π。

The warp yarn 3 is pulled out of the supply unit 2 by a drag roller 8, while the reel, roller or unwinding drum 4 of the supply unit 2 rotates about an unwinding rotation axis X2 to unwind the warp yarn 3 moving towards the yarn interlacing area 5.

A brake 15 is provided to exert a braking action on the warp yarn 3 upstream of the drag roller 8. In one embodiment, the brake 15 may comprise a brake pad 16 operating between the supply unit 2 and the drag roller 8. The brake pads 16 are pushed towards each other to directly act by friction on the warp yarn 3 sliding in between, which is schematically shown in fig. 1.

In an alternative embodiment, not shown, the brake 15 can act on one or more idle redirecting rolls on which the warp yarn 3 travelling along its path towards the yarn interlacing area 5 is wound. At least in this latter case, the brake 15 may be configured to resist rotation of one or more of the idler redirect rollers.

In another alternative configuration, the brake 15 may be configured to act on the supply reel, roller or unwind roller 4 of the supply unit 2 for resisting rotation about the unwinding rotation axis X2.

The brake 15 may comprise a real brake 15, e.g. operated by friction, magnetic induction, etc., or at least a motor operated in a brake mode when assembled for resisting rotation, i.e. an electric motor generating energy due to forced rotation of its rotor.

The brake 15 may be driven under the control of a central processing unit CPU by means of a brake controller 17, which may comprise an actuator acting on the brake pads 16 to adjust the braking force. If a motor operated in brake mode is used as the brake 15, the brake controller 17 may be configured to adjust an electrical load applied to the motor operated in brake mode to modulate the braking force.

During operation of the textile machine 1, the action of the brake 15 resists movement of the warp yarn 3 towards the yarn interlacing area 5, but does not prevent the desired movement of the warp yarn 3. Thus, the warp yarn 3 upstream along the drag roller 8 generates and maintains the supply traction force SF.

Effective control of the supply traction SF is critical for proper execution of the interconnection between warp yarns 3 and/or with weft yarns and/or other yarns at the yarn interlacing area 5.

On the other hand, the supply traction SF may be affected by a series of parameters that may not be easily predictable and/or controllable.

For example, at least when the supply unit 2 is in the form of a reel carrying the warp yarn 3 wound around the unwinding rotation axis X2, the rotation of the supply unit 2 causes its external diameter to gradually decrease as the warp yarn 3 is unwound from the unwinding reel 15. Thus, during operation of the textile machine 1, if the braking action against rotation about the unwinding rotation axis X2 remains constant, the supply traction SF will gradually increase in response to a gradual decrease in the unwinding diameter. In addition, especially in the case of warp yarn 3 supplied from a number of different bobbins or reels, small brakes or simple friction elements, possibly added to create some load, will not allow precise control, resulting in fluctuations in the feed traction SF. Variations in the supply tractive effort SF may also be required for the operating program.

In accordance with the present invention, forward control of the supply tractive effort SF is performed to maintain the supply tractive effort at a desired target value SFtv by implementing the repetitive control loop explained herein with particular reference to FIG. 2.

At or just after the start-up of the textile machine 1 (see block 18 in fig. 2), the user can conveniently set the desired target value SFtv for the supply traction SF (block 19). For example, the target value SFtv may be entered directly via the input interface 14 or selected from a menu stored in the central processing unit CPU. The target value SFtv may also be part of a work program selected from a work program menu previously stored in the central processing unit CPU, for example via the input interface 14.

If necessary, the target value SFtv of the supply traction SF may be varied during operation of the textile machine 1 according to a predetermined working procedure, for example increased and/or decreased while the work is performed in response to a change of the knitting pattern carried out in the yarn interlacing area 5. Instead, for example, the predetermined knitting pattern may comprise a production phase in which the supply traction SF is required to be greater or lower than in the previous or subsequent production phase, for example due to the insertion of additional yarns in the yarn interlacing area 5 or for other reasons, in order to optimize the result.

During operation of the textile machine 1, the drag controller 12 repeatedly queries the drag electronic control unit 11 to obtain an instantaneous value of the drag torque DT.

The instantaneous value of the drag torque DT, which varies with the supply current I9 of the drag motor 9, can be calculated by the drag controller 12. More specifically, the value of the supply current I9 is obtained by the dragging electronic control unit 11 (block 20). Next (block 21), the instantaneous value of the drag torque as a function of the supply current I9 of the drag motor 9 can be calculated according to the following formula:

DT＝I9*kT9*i10

where kT9 denotes the moment constant of the drag motor 9. As is known, the torque constant is a motor specific value, typically expressed in Nm/a.

The instantaneous value of the drag torque DT is directly related to the instantaneous value of the supply force SF according to:

SF＝DT*2/DD+WF

It also considers the influence of the tensioning WF that may be applied to the textile product 6 leading to the collecting unit 13. The tension WF can be detected, if necessary, by means of a known sensor system acting on the textile product downstream of the dragging unit 7.

A comparator (not shown), for example embedded in or separate from the central processing unit CPU, is provided for comparing (block 22) the instantaneous value of the drag torque DT with its target value DTtv. The target value DTtv of the drag torque can be easily calculated based on the predetermined target value SFtv by the following equation:

DTtv＝(SFtv-WF)*DD/2。

If the instantaneous value of the drag torque DT is equal to the target value DTtv, a new supply adjustment cycle is implemented.

Otherwise (block 23), the comparator determines if the instantaneous supply tractive effort SF is less than the target value SFtv. If so, the central processing unit CPU drives the brake 15 by means of the brake controller 17 to increase the braking action on the warp yarn 3 (block 24). Otherwise, the braking effort is reduced (block 25).

As described above, the drag controller 12 drives the drag motor 9 to maintain the desired target value Vtv of the forward speed. Accordingly, in response to increasing and decreasing the braking action, the drag controller 12 simultaneously drives the drag motor 9 by increasing or decreasing the supply current I9 to respectively increase and decrease the drag torque applied by the drag roller 8 so as to maintain the forward speed at the desired target value Vtv. Increasing and decreasing the braking action also causes a corresponding increase and decrease, respectively, of the supply tractive effort SF towards the target value SFtv such that this target value remains unchanged or substantially unchanged.

Any adjustment of the braking action may trigger a new supply adjustment cycle, as shown in fig. 2. Additionally or alternatively, iterations of the supply traction control loop may preferably occur at a desired frequency comprised between 1Hz and 10 Hz. This frequency may remain constant or vary gradually during operation of the machine.

A display unit 26, for example embedded in the input interface 14 and controlled by the central processing unit, may be conveniently provided for displaying the instantaneous value of the supply traction SF and/or any deviation thereof with respect to the set target value SFtv. This helps to constantly inform the operator about the correct operation of the textile machine 1.

Claims

1. A method for controlling warp yarn tension on a textile machine, wherein:

A plurality of warp yarns (3) unwinding from a supply unit (2) and moving longitudinally to reach a yarn interlacing area (5);

a textile product (6) comprising said warp yarns (3) is formed at the yarn interlacing area (5);

A drag roller (8) engaging the textile product (6) in the vicinity of the yarn interlacing area (5);

A drag motor (9) rotates the drag roller (8) to push the textile product (6) away from the yarn interlacing area (5);

a drag controller (12) electronically controls the drag motor (9) to maintain a selected target advance speed Vtv of the textile product (6);

Wherein a braking action is effected on said warp yarn (3) upstream of the dragging roller (8) to provide a supply traction force SF along said warp yarn (3) itself;

wherein a plurality of repetitive control cycles are implemented during operation of the textile machine (1), each repetitive control cycle comprising:

Acquiring an instantaneous value DT of a drag torque applied to the drag roller (8) or at least one parameter representative thereof;

an instantaneous value of the supply traction force SF, or of the at least one parameter representative thereof, is determined as a function of the instantaneous value DT of the drag torque.

2. The method of claim 1, wherein a target value SFtv of the supply traction SF is maintained during operation of the textile machine (1) by said repetitive control cycles, each repetitive control cycle further comprising:

comparing the obtained instantaneous value DT of the drag torque with a predetermined target value DTtv of the drag torque, the predetermined target value corresponding to the target value SFtv of the supply tractive effort;

Increasing the braking action when DT < DTtv;

When DT > DTtv, the braking action is reduced.

3. The method of claim 2, wherein the increasing and decreasing of the braking action is accomplished simultaneously with the increasing and decreasing of the drag torque DT, respectively.

4. The method of claim 3, wherein each of the repeated control loops further comprises:

Driving the drag motor (9) to increase the drag torque when DT < DTtv;

when DT > DTtv, the drag motor (9) is driven to reduce the drag torque.

5. The method according to one or more of the preceding claims, wherein driving the traction motor (9) to increase and decrease the traction torque DT is achieved by increasing and decreasing, respectively, a supply current of the traction motor (9).

6. A textile machine, comprising:

At least one supply unit (2) configured to carry warp threads (3);

Yarn interlacing means acting on a yarn interlacing area (5) for producing a textile product (6) by means of the warp yarns (3) supplied from the supply unit (2);

-a drag roller (8) configured to engage the textile product (6) in proximity of the yarn interlacing area (5) and to push the textile product away from the yarn interlacing area (5);

-a dragging motor (9) acting on the dragging roller (8) to rotate it at a dragging angular speed, so as to draw the warp yarn (3) from the supply unit (2) and push the textile product (6) away from the yarn interlacing area (5);

A drag electronic control unit (11) provided with the drag motor (9) and configured to obtain a supply current I9 of the drag motor (9);

-a drag controller (12) configured for electronically controlling the drag motor (9) to maintain a selected target advancing speed Vtv of the textile product (6), and to obtain an instantaneous value of a drag torque DT applied to the drag roller (8) as a function of the supply current I9 of the drag motor (9), or at least one parameter representative thereof;

a brake (15) acting on said warp yarn (3) upstream of the dragging roller (8) to provide a supply traction force SF along said warp yarn (3) itself;

A Central Processing Unit (CPU) configured to determine an instantaneous value of the supply traction force SF, or a representative of the at least one parameter thereof, as a function of the instantaneous value DT of the traction torque.

7. The textile machine of claim 6, further comprising a comparator configured to compare the obtained instantaneous value DT of the drag torque with a predetermined target value DTtv of the drag torque, the predetermined target value corresponding to a target value SFtv of the supply drag force;

the Central Processing Unit (CPU) is further configured for driving the brake (15) to:

Increasing the braking action when DT < DTtv;

When DT > DTtv, the braking action is reduced,

To maintain the supply tractive effort SF at the target value SFtv.

8. The textile machine according to claim 6 or 7, wherein the brake (15) comprises brake pads (16) which are configured to be pushed towards each other by a braking force so as to act directly on the warp threads (3) sliding therebetween by friction.

9. Textile machine according to one or more of claims 5 to 8, wherein the brake (15) acts on at least one redirecting roller on which the warp yarn (3) is wound for applying a braking force against the rotation of the redirecting roller.

10. Textile machine according to one or more of claims 5 to 9, wherein the brake (15) is configured to resist the rotation of a supply reel, roller or unwind cylinder (4) of the supply unit (2).

11. Textile machine according to claim 9 or 10, wherein the brake (15) comprises an electric motor operated in braking mode which generates energy due to a forced rotation of a rotor thereof.

12. Textile machine according to one or more of claims 8 to 11, wherein the Central Processing Unit (CPU) is configured for driving the brake (15) by means of a brake controller (17) comprising actuators acting on the brake pads (16) for adjusting the braking force.

13. The textile machine of claim 11, wherein the Central Processing Unit (CPU) is configured to drive the brake (15) by means of a brake controller (17) configured to adjust an electrical load applied to the electric motor for braking mode operation to adjust the braking force.

14. Textile machine according to one or more of the claims from 6 to 13, further comprising a display unit (26) connected to the central processing unit CPU for displaying an instantaneous value of the supply traction SF and/or any deviation thereof with respect to the set target value SFtv.

15. Textile machine according to one or more of claims 6 to 14, wherein the drag motor (9) is driven to:

Increasing the drag torque when DT < DTtv;

when DT > DTtv, the drag torque is reduced.