TECHNICAL FIELD

The present invention relates to a device for controlling, preferably continuously or at close inter¬ vals during ongoing weaving, thread tension in a weaving machine, which thread tension is dependent upon position and/or rotation of one or more beams forming part of the weaving machine. The invention is applicable to weaving dobbies of various types, e.g. dobbies for forming weaving, blanket weaving, etc., and dobbies which operate with open and closed sheds, etc. The invention can advantageously be used on weaving machines which operate with large fabric widths, e.g. 10-30 metre fabric widths.

PRIOR ART

It is known per se to propose different types of control of the warp thread tension in a weaving machine of the generic type. By influencing the speeds of the beam or beams concerned, it is possible, where there are tendencies for the warp threads to slacken, to obtain a tentering effect in the thread during certain stages of the weaving.

It is also known per se to arrange the beams in a spring-mounted disposition, so that a certain positional mobility is obtained in each beam(s).

It is also known per se to exercise control of a weaving machine function by means of computer equipment, which can in this case operate with conventional software in relation to the control system/control in question.

ACCOUNT OF THE INVENTION TECHNICAL PROBLEM

There is a requirement to produce high-quality woven products using rational production processes. Weaving machine manufacturers are faced with high demands as regards the functions of weaving machines, which

functions must be able to be performed with a high degree of reliability and must enable simpler operating and handling procedures for staff working at the machines, faster weaving speeds, long working life in terms of the weaving machine construction, long service intervals, etc. Added to this is the fact that price pressure bearing upon product development, manufacturing, etc., in relation to the actual machine construction, -is being accentuated to a still greater degree. The weaving machine has to be able, inter alia, to work with few operating breakdowns and stoppages.

The above means, inter alia, that recourse must be taken to a refined control function for functional parts included within the weaving machine. The thread arrangement in the weaving machine represents a swinging mass which must be optimally controlled so that weaving machine functions which follow one another in the course of the weaving can be performed in an unbroken and effective sequence. By making the beam arrangement which is involved adaptive, so that the rotations and/or positions of the booms are altered during ongoing weaving, the thread tension in the warp threads can be kept within predetermined, desired thread tension ranges or essentially constant. The object of the present invention is to propose an arrangement which solves, inter alia, this problem.

There is a requirement to be able to weave at a higher and more uniform quality. The individual thread tensions in the warp threads must in this context be adapted to the binding and/or wrapping pattern between the warp and weft threads, so that the weft function remains essentially the same, irrespective of the pat¬ tern. This problem is solved by the invention. The adaptiveness in the rotation and/or position of each beam can also be adjusted to different thread material quali¬ ties, production variances in the machine, etc. The invention aims to solve this problem also.

According to the invention, feedback function(s) working with precision should be arranged for each beam

control. The beams in question should also be able to be controlled with great accuracy, despite a relatively large mass in the beam in question. The invention aims to solve this problem as well. Wear and changes in the internal and external conditions in the weaving machine and in the thread material can also continuously occur. Compensations in the control of the beams and other components in the machines must therefore be able to be continuously carried out. The invention aims also to solve this problem.

According to the invention, for the control of each beam or for the control of the beams, use should be able to be made of AC-servo motors of a known type, or of cylinders operating with a feedback function (e.g. hydraulic cylinders), etc. The said control mechanisms should be able to be incorporated into an expedient function containing the above-specified requirements for the weaving machine, the woven product, etc. The invention aims to solve this problem also.

One object of the invention is also to be able to achieve an effectively operating back rest arrangement in which one or more beams are arranged so as to be positionally mobile or displaceable in the space. A back rest arrangement of this kind should be able to work together, in the thread tension control, with other components in the weaving machine which have an influence on the same. A coordination problem exists in this context between the various functions in the weaving machine which exert an influence upon the thread tension control. The beam arrangement and its control system must in this case be constructed so that there is adjustment to the construction and control systems of the other said components in the weaving machine. The invention aims to solve this problem also.

The invention can be put to good use in dobbies in which shaft frames are included for the creation of open and closed sheds during the continuous weaving in the machine. The said shaft frames have an influence upon

the thread tension and the arrangement with back rest(s) and the control system for this/these has to be coordinated with the control systems and functions of the shaft frames. The invention aims to solve this problem also.

THE SOLUTION

What can primarily be considered to be characteristic of a device according to the invention is, inter alia, that at least one beam of the said beams is suspended in a positionally mobile manner and is arranged so as to be detectable by a force detection mechanism, preferably having the form of a load cell, by means of which force detection mechanism one or more electrical signals can be generated. The value(s) and/or number of the signal(s) is dependent upon one or more forces, provoked by the thread tension, upon the beam(s). The signal or signals in this context form(s) part, as control signal(s), of an activation system, exercising the said thread tension control, for the said position(s) and/or rotation(s) in respect of the beam(s). The activa¬ tion system will in this case comprise a drive source which operates with a feedback function and which prefer¬ ably has the form of or includes an alternating-current servo motor, here referred to as an AC-servo. In one embodiment of the inventive concept, the beam or beams form(s) part of a back rest system for warp threads in a weaving machine. The said beam(s) can be driven by the said alternating-current servo motor via a gearbox system. Each force detection mechanism/load cell can in this context be arranged at that one of the beams from which the warp thread runs out. The activation system includes, in one embodiment, a computer unit which receives and processes the said control signal(s). The computer unit, in dependence upon the reception and processing, generates one or more target-value signals to the alternating-current servo motor, which, for the execution of its said feedback function, also includes a transmitter mechanism, which is preferably constituted by

a pulse transmitter, the signal (actual-value signal) of which can be fed back to the computer unit, which generates the said target-value signal(s) with the aid of this feedback signal (actual value signal(s)). The said force detection mechanism or load cell produces an electric signal which is proportional to the detected force on the beam resulting from the thread tension.

Each beam is suspended in a positionally mobile manner in two or more mounting points along its respective longitudinal extents. A force detection mechanism or load cell is arranged in one or more of the said mounting points.

In the event of a plurality of interacting beams, e.g. beams which form part of a back rest system having a plurality of beams, the activation system effectuates the thread tension control by means of a continuous or close-intervalled, step-by-step change in the rotation(s)/rotation speed(s) of the beam(s). The activation system can also take account of the fact that thread advancement in a feed-out direction has to take place during ongoing weaving. Each force detection mechanism bears against each beam via a power trans¬ mission mechanism which transmits the force from the rotating beam to the power cell which is fixedly arranged relative to the beam.

The activation system can also operate with a positional movement and/or rotation of each beam, which motion is guided by the weaving program of the weaving machine. In this case, a comparison can be made of the thread tension control effectuated by the weaving program and the thread tension control obtained in practice. Any differences in the predetermined control and the actual control can then be adjusted, so that the weaving machine program is able to operate with altered/adjusted/adaptive values. The thread tension control is effectuated on a thread system formed by warp and weft threads, in which system the total fabric width can assume values -of up to 10-30 metres and in which the weaving speed can assume values of up to about 100 picks per minute. The thread

tensions in the warp threads can assume values of up to about 50,000 Newton/metre.

Each beam can be activated, by means of force effectuated by the warp threads, against the action of a spring function which endeavours to return the beam to its position. The beam system can also be arranged so that it is positionally variable in its entirety, together with the force detection mechanism(s) in question, which is/are fixedly arranged relative to the beam(s) .

ADVANTAGES

As a result of that which is proposed above, an effective control of the thread tension function in a weaving machine can be obtained. For the implementation of the invention, use can be made in the weaving machine of components which are known per se, in the case of the AC-servo, computer unit, software, etc. Also the back rests as such, as well as the gearbox function, etc., can be constructed in a manner which is known per se. The thread tension control exercised by means of the inven¬ tion can be coordinated with other components in the weaving machine system which act upon the thread tension for the achievement of an, in overall terms, effectively operating thread tension control function. High and uniform quality can be obtained in the woven material, blanket, fabric, etc.

DESCRIPTION OF THE FIGURES

A presently proposed embodiment of a device exhibiting the characteristics which are indicative of the invention will be described below, with simultaneous reference to the appended drawings, in which:

Figure 1 shows, in basic diagram form, parts, which are affected by the invention, in a weaving machine which, in the present instance, is constituted by a dobby.

Figure 2 shows, in end view, mounting points for beams in a back rest system,

Figure 3 shows, in end view, the arrangement of a .force detection mechanism in a mounting point for a beam shown in Figure 2, and

Figure 4 shows, in perspective view, the mounting of a back rest, in which a load cell is arranged in each mounting point.

DETAILED EMBODIMENT

Figure 1 shows relevant parts of a dobby 1, which is symbolised by a generally indicated shaft frame system 2 and a back rest system 3. The warp threads running out from the back rest system are indicated by 4. The warp threads are divided into a shed by the shaft frame arrangement and, in the arrangement shown in Figure 1, the threads for the upper shed have been indicated by 4a and for the lower shed by 4b. The butting edge is defined by 5 and the fabric which has been finish-woven in the weaving machine has been denoted by 6. The back rest arrangement is represented, in the illustrative embodi¬ ment, by three back rests 7, 8 and 9. The beams are driven by means of a gearbox system 10, which indivi¬ dually acts upon the said beams 7, 8 and 9 via power transmission systems 7a, 8a or 9a. Gearbox and power transmission systems of this kind are already well known and will not here be described in any greater detail. The gearbox system 10 is driven by an AC-servo, which can be of the SEIDEL type. An AC-servo of this kind is provided on its axle with a pulse transmitter 12, which indicates or detects rotated turns of the AC-servo. The beam 7 of the said beams is provided with a force detection mechanism in the form of a load cell 13, which can be constituted by a model which is known per se and can be of the NOBEL Elektronik type, for example. The said AC-servo thus forms a drive source for the beams 7, 8 and 9 via the gearbox system 10. The drive source 11 operates with a feedback function of which the said pulse transmitter 12 forms part. The beam 7 is spring-mounted in accordance with that which is stated below and the load cell 13 detects the force F brought about or

provoked by the warp threads 4 and emits, in dependence upon the detection, an electrical signal il which is dependent against [sic] the force F. A computer unit 14, which can be constituted by a model which is known per se, forms part of an activation system for the AC-servo. The computer unit 14 receives, as a control signal, the said signal il from the load cell 13. The computer unit processes the received signal il and effectuates a target-value signal i2 to the AC-servo 11. The signal of the pulse transmitter is utilised as an actual-value signal i3. In the present instance, the force F is governed or controlled with the aid of rotation changes (speed and/or direction) in the beams 7, 8 and 9, brought about by the AC-servo via the gearbox 10. The computer unit 14 detects the force via the load cell and primes the AC-servo so that the said rotation changes or changes in rotation speeds materialise. The system thus operates with an outer, open loop and an inner, closed loop, in which the return signal i3 is fed back to the computer. The computer unit, in its control of the AC-servo, therefore makes use of both the signals il and i3 for generating the signals i2.

In Figure 2, the said beams are indicated by 7', 8' and 9' . The beam 7' is essentially spring-mounted in a number of mounting points and a mounting point of this kind is shown in Figure 2. The beam 7' is arranged having a tapered axle part 15, which is displaceably mounted in a mounting space 16. The mounting bracket is not shown in detail since its principle and construction are assumed to be already known. The mounting bracket per se is symbolised by 17. In the said mounting space there is arranged a spring 18, which endeavours to guide the beam 7' in the direction of the arrow 19. The above-stated force has here been denoted by F' , which force endeavours to activate the beam 7' in the direction of the arrow 20 against the action of the said spring 18. The directions 19 and 20 essentially coincide with the direction of the outgoing warp thread 4' . The warp threads run in towards the beam 9' and the warp thread parts in question have

been denoted by 4c. The warp threads run around the beam 9' and between the beams 7' and 9' , in order then to con¬ tinue around the beam 7' and between the beams 7' and 8' . In accordance with the above, the warp 4' runs out from the beam 7' . The beams 8' and 9' are also essentially spring-mounted, so that they are pressed, by means of the springs 21 and 22 respectively, against the beam 7'. The beams 8' and 9' have tapered axle sections 23 and 24 respectively, similarly to the beam 7' (cf. 15). The beams 8' and 9' are mounted essentially in a corres¬ ponding manner to the beam 7' and are able to move towards and away from this beam in the directions of the arrows 25, 26 and 27, 28 respectively. In the illustra¬ tive embodiment shown, it can be noted that the spring 18 is stronger than the spring 22, since it must be able to absorb both the force F' and the force from the spring 22.

The beams 7', 8' and 9' are rotatable in first directions 29, 30 and 31, respectively. The thread tension force F' must be able to be maintained at an essentially constant value or within a predetermined force value range with the aid of change in the rotation speeds of the beams 7' , 8' and 9' . The control must in this context be able to take place such that a suitable advancement function occurs in the weaving machine in the back rest system formed by the beams 7' , 8' and 9' , simultaneously with the said maintenance of constancy being able to be effectuated. In one embodiment, the beams 7' , 8' and 9' can also be rotated in the other direction 32, 33 and 34. Supplementary or alternatively to this, the entire beam assembly, together with the gearbox and drive source system, can be arranged in a positionally displaceable manner. This positional dis¬ placeability has basically been indicated in Figure 1 by 35, the displacement directions of the assembly having been shown by the arrows 36 and 37. The displaceability of the beam assembly can be achieved in a manner which is known per se.

According to the invention, at least one of the

beams in the beam system shown is arranged so as to be detectable by means of a force emission [sic] mechanism, which has been defined in Figure 3 by 13' . The beam whose force has been detected has been indicated in Figure 3 by 7' ' and corresponds to the beams 7 and 7' in Figures 1 and 2, respectively. The said force F and F' in Figures 1 and 2 has been indicated by F' ' in Figure 3. The bearing force of the beam 7' ' against the force detection mechanism 13' is indicated by f and the counter-force from the load cell 13' by f, which is the same size as the said force f, which in turn corresponds to the force F''. The load cell is fixedly arranged relative to the beam 7' ' . In the embodiment having a displaceable beam assembly 35, the load cell 13' is displaceable with the assembly, but is simultaneously fixed in relation to the beam 7' ' . The outgoing signal from the load cell is indicated by il' .

Figure 4 shows the mounting of a beam 7' ' ' corresponding to the beam 7' ' in Figure 3. The mounting can be executed in a plurality of mounting points 38, 39, 40 and 41. One or more of the said points can be provided with the said force detection mechanism (cf. 13' in Figure 3) . In Figure 4, each mounting point has been provided with its force detection mechanism 13'', 13'''., 13'"', 13'"", etc. Each load cell in this context emits its signal il", il"'., il"", il""', etc.

In the power transmission between the rotating beam and the load cell in question (13' in Figure 3), which is fixedly arranged relative to the beam, use is preferably made of a power transmission mechanism 42 according to Figure 3. The power transmission mechanism 42 can operate with a ball bearing function.

The invention is not limited to the embodiment shown by way of example above, but can be subject to modifications within the scope of subsequent patent claims and the inventive concept.