CH654665A5 - Method and appliance for measuring characteristic features of fibrous material, and application of the method - Google Patents

Abstract

The method relates to the measurement of fibrous material, such as ribbons and rovings, by means of ultrasound. A suitable arrangement of sound transmitter (3), sound receiver (8) and fibrous material (6) ensures that all the sound waves reaching the sound receiver (8) have permeated the fibrous material (6). By operating the sound transmitter (3) in a pulsed manner and, accordingly, arranging for the sound receiver (8) to be ready to receive for short periods only, all the lagging interference signals generated by reflections and interferences are suppressed, which ensures that the variable to be measured, i.e. the amount of fibres (6) present at any time in the measuring section, is largely free from interference. This measured variable can be utilised as a value for the cross-sectional uniformity or alternatively as a controlled variable for the production of uniform rovings or ribbons. <IMAGE>

Description

** WARNING ** beginning of DESC field could overlap end of CLMS **.

PATENT CLAIMS 1. A method for measuring characteristic features of fiber material, in particular for measuring the fiber quantity of textile fiber tapes by means of sound waves, characterized in that the fiber material is penetrated by the sound waves emanating from at least one sound transmitter on their way to at least one sound receiver, the intensity of the sound waves damped or delayed in accordance with the amount of fibers, the sound transmitter, fiber material and sound receiver are arranged in such a way that only sound waves that penetrate the fiber material directly reach the sound receiver and are evaluated.

2. The method according to claim 1, characterized in that sound transmitters and sound receivers are operated in the ultrasonic range.

3. The method according to claim 1, characterized in that the fiber material is limited by lateral boundary surfaces such that the sound waves are forced to penetrate the fiber material in order to get from the sound transmitter to the sound receiver.

4. The method according to claims 1 and 3, characterized in that the fiber material is arranged between the boundary surfaces in such a way that all sound waves that pass from the sound transmitter through the fiber material to the sound receiver penetrate approximately the same amount of fibers.

5. The method according to claim 1, characterized in that the sound transmitter (3) intermittently emits sound waves (4), and that only the beginning of the incoming sound waves (7) is evaluated by the sound receiver (8) and the time-dependent portion of the sound wave arriving later is suppressed in such a way that interference and resonances of sound waves of different duration are no longer taken into account by the sound receiver.

6. The method according to claim 1, characterized in that the sound receiver is arranged such that any disturbing sound waves from the outside must also penetrate the fiber material to get to the sound receiver and thereby experience the same attenuation as the sound waves from the sound transmitter.

7. The method according to claims 1 and 3, characterized in that the lateral boundary surfaces (5) are formed by parallel plates (21) with a fixed or variable distance.

8. The method according to claim 1, characterized in that the characteristic features of the fiber material, in particular the amount of fiber material (6) from the attenuation of the part of the incoming sound signals (7) selected on the sound receiver (8) is obtained.

9. The method according to claim 1, characterized in that the characteristic features of the fiber material (6), in particular the amount of fiber material, is obtained from the delay time of the arriving at the sound receiver (8), selected part of the sound signal (7).

10. The method according to claim 1, characterized in that sound waves of different frequencies are emitted by the at least one sound transmitter (22).

11. The method according to claims 1, 9 and 10, characterized in that the different propagation delay at different sound frequencies is used to compensate for the temperature dependence of the propagation time of the sound wave from the sound transmitter (3) to the sound receiver (8).

12. The method according to claims 1, 8, 9 and 10, characterized in that several characteristic features of the fiber material, such as, for example, the amount of fibers, fineness of fibers, and the mixing ratio, are determined simultaneously by a combined evaluation of damping and delay time at one or more sound frequencies.

13. The apparatus for performing the method according to claim 1, characterized by at least one sound transmitter (22) and at least one sound receiver (23), between which the fiber material (20) to be examined with regard to characteristic features is arranged, and by boundary surfaces (5) for guidance and limiting the fiber material (20), further by an electronic circuit for generating the sound signals and for evaluating the sound waves arriving at the sound receiver (23).

14. The apparatus according to claim 13, characterized in that the boundary surfaces (5) are designed as parallel plates (21) with a fixed or variable distance.

15. Device according to claims 13 and 14, characterized in that the plates (21) form a slot open on at least two sides, that the sound receiver (23) is acoustically shielded on the closed side of the slot and only with an acoustic opening (24) is provided against the inside of the slot, that there is at least one sound transmitter (22) on the opposite side of the slot, and that the fiber band (20) between the sound transmitter (22) and sound receiver (23) is used to measure the characteristic features the slot is guided.

16. The device according to claims 13, 14 and 15, characterized in that the measuring slot formed by the plates (21) is closed on the side opposite the acoustic opening (24).

17. Application of the method according to claim 1 for measuring the cross-sectional uniformity of strips and rovings.

18. Application of the method according to claim 1 for the measurement of the layer thickness of sheet-like amounts of fiber.

19. Application of the method according to claim 1 for controlling textile machines to achieve uniform fiber slivers.

The invention relates to a method and a device for measuring characteristic features of fiber material, in particular the measurement of the amount of fibers in textile fiber bands, and the application of the method.

Experiments have been carried out for some time and appropriate methods and devices have been developed to determine the amount of fibers in textile tapes using ultrasound. For example, refer to the patent of Heller (US No. 2 966 057), as well as the publication by Bobrov, Gorelik and Volosmikov, Teknologia Tekstilnov Promystchlennosti No. 4 (1973), 115.

Nevertheless, it has not yet been possible to manufacture a device with sufficient accuracy and reliability on this basis. A major reason for this is the high interference ability of the sound waves. As a result, certain resonances occur at each arrangement, which considerably disrupt the linear or monotonic relationship between the amount of fibers and the size of the influence on the sound signal. Another problem in the determination of the amount of fibers by means of ultrasound arises from the fact that even very small openings suffice to falsify the measurement considerably if sound waves can get from the transmitter to the receiver through these openings without completely penetrating the fiber material.

The present invention bears these findings

Bill and relates to a method, a device and the application of the method according to the features formulated in the independent claims.

The fundamental difficulties are eliminated by arranging the fiber material between the sound transmitter (short: transmitter) and sound receiver (short: receiver) in such a way that the sound waves arriving at the receiver are evaluated in such a way that only sound waves that come directly from the transmitter without additional reflections reach the receiver and have penetrated the fiber material, are evaluated.

According to the invention, the fiber material is guided through lateral boundary surfaces, in particular in the case of fiber tapes, in such a way that all sound waves are forced to penetrate the fiber tape in order to get from the transmitter to the receiver. The lateral boundary surfaces are preferably formed by parallel plates, the compression being chosen so large that the fiber material lies snugly on both plates. This avoids side openings through which sound waves can partially or even completely bypass the fiber material. Such openings, even if they are only narrow, have similar effects to short circuits in an electrical circuit and can therefore considerably disrupt measurements.

In practice, reflection-free sound transmission can usually only be achieved with great effort, if at all. To determine the characteristic features of fiber material, the transmitter can therefore intermittently emit sound waves through the fiber material to the receiver. The receiver only evaluates the beginning of the incoming sound waves and suppresses the later arriving part of the sound waves. Since sound waves, which carry out additional reflections, travel a longer distance from the transmitter to the receiver, they arrive later at the receiver and are therefore suppressed. The pauses between the emitted sound waves are to be chosen so long that all resonances that arise can subside.

From the evaluated sound signal at the receiver, both the attenuation and the transit time delay can be used to determine the amount of fiber or other characteristic features of the fiber material. The delay time also depends on the sound frequency used. The runtime changes due to temperature changes, however, is frequency independent. The temperature dependency can be eliminated by using two or more different frequencies, which leads to a significant improvement in the measurement.

The different frequencies can be transmitted simultaneously or alternately by one or more transmitters. The use of two or more different frequencies can also serve to determine the distance from the transmitter to the receiver.

The simultaneous determination of damping and delay time offers the possibility of simultaneously determining two different characteristic features of the fiber material, for example the fiber quantities and the fineness of the individual fibers.

Based on the description and the schematic Figures the method and an embodiment of the device is explained in more detail. It shows: 1 is a block diagram of the device according to the invention, 2 shows a diagram of the temporal behavior of the transmitter and receiver, Fig. 3, the measuring device in supervision and Fig. 4 the same in plan according to section A-A.

A transmitter 3 (FIG. 1) periodically emits a sound wave 4, as shown in FIG. 2. These sound waves 4 penetrate the fiber material 6, which is guided through boundary surfaces 5 and reach the receiver 8. The fiber material 6 is preferably to be arranged between the boundary surfaces 5 in such a way that the height h is greater than the distance d, since strong inhomogeneities in the height h can falsify the measurement. The emerging sound waves 7 reach the receiver 8 according to FIG. 2 with a time delay At and an amplitude AU. The time delay At increases proportionally with the permeated fiber material and the amplitude AU decreases exponentially with the permeated fiber material, i.e. At = to + al Ato + a..Q.undAU or E us dU C Here a and ss are given by the arrangement, e is the density of the fiber material and the fill factor. The receiver only takes into account sound waves that arrive between Ti and T2 (cf.

Fig. 2) and suppresses the rest 15, which would falsify the measurement. As soon as resonances have subsided sufficiently, i.e. at time T0, the transmitter 3 sends a sound wave 4 again.

The distance d between the boundary surfaces 5 can be variable so that the optimum distance can be set for each fiber quantity. Transmitter 3, boundary surfaces 5 and receiver 8 must be arranged according to the invention in such a way that sound waves 7 cannot bypass boundary surfaces 5 without penetrating fiber material 6.

A possibility of bypassing fiber material 6 and boundary surfaces 5 is only permissible if the resulting detour of the sound wave and the resulting time delay are so great that the corresponding sound wave 7 reaches the receiver 8 at the point in time at which the received signals are suppressed will.

Transmitter 3 and receiver 8 must be installed acoustically isolated from each other. This can be achieved, for example, by mounting transmitter 3 and receiver 8 on sound-insulating damping elements 16, such as rubber buffers. This prevents sound signals from being transmitted through structure-borne noise.

The block diagram of a complete measuring arrangement is shown in FIG. 1. A sine oscillator 1 excites the transmitter 3 via an analog switch 2, which is preferably designed as a piezo element. Its sound energy is directed to the receiver 8, which preferably consists of a microphone. A clock generator 12 with a zero-crossing detector 14 controls the analog switch 2 for emitting short sound pulses, on the one hand, and controls a time element 13 with which the transit time is simulated. This time element closes a further analog switch 9 after a predetermined time and influences a zero crossing detector 14, which opens the analog switch 9 again after a predetermined number of zero crossings of the received signal and thus interrupts the forwarding of the received signal to an evaluation device 10 again. In this evaluation device 10, the input pulses of the sound receiver 8 are analyzed with regard to damping and / or delay time and represented as an output signal 11. The evaluation device 10 can also contain a computer or corresponding electronic elements, such as microprocessors, to compensate for the temperature from the transit time delay at different frequencies or to determine the distance from the transmitter 3 to the receiver 8. Furthermore, the evaluation device 10 can be used to determine several characteristic features of the fiber material 6 simultaneously, such as, for example, the amount of fiber and the fineness of the fiber, by jointly evaluating the damping and delay time.

This output signal 11 can serve various purposes: representation in a display and / or writing device for cross-sectional uniformity; - As a control or regulating signal for influencing cross-section-determining organs on production machines in the textile industry, such as cards or draw frames.

However, the execution of the necessary electronic circuit is familiar to a person skilled in the art and therefore need not be the subject of the invention.

Finally, the invention also includes the use of the method for measuring the cross-sectional uniformity of strips, rovings and sheet-like amounts of fiber, and for controlling textile machines on the basis of the measured values for the cross-sectional uniformity.

3 and 4, an embodiment for measuring the uniformity of textile fiber tapes is shown in plan and plan. The sliver 20 is pulled between two plates 21 which form the boundary surfaces 5. The transmitter 22 is located on the open side of the slot which is formed by the two plates 21. One or more transmitters 22 can be arranged in one or both plates 21. The receiver 23 is located on the other, closed side of the slot. It is acoustically shielded and has only one acoustic opening 24 towards the inside of the slot. The tape 20 is guided over this opening 24. This arrangement ensures that any external and disruptive sound waves 25 are damped from the outside to the same extent as sound waves 26 from the transmitter 22. Thus, the measuring device also works without interference even with very large dampings. The open slot also makes handling much easier, since the sliver 20 to be measured can simply be placed in the slit without the sliver 20 having to be separated.

The arrangement of the measuring slot formed by the plates 21 can also be made such that it can be closed by mechanical means on the side opposite the acoustic opening 24. The entry of external sound waves into the measuring field and thus into the receiver 23 is thereby made more difficult.

Claims (19)

PATENT CLAIMS 1. A method for measuring characteristic features of fiber material, in particular for measuring the fiber quantity of textile fiber tapes by means of sound waves, characterized in that the fiber material is penetrated by the sound waves emanating from at least one sound transmitter on their way to at least one sound receiver, the intensity of the sound waves damped or delayed in accordance with the amount of fibers, the sound transmitter, fiber material and sound receiver are arranged in such a way that only sound waves that penetrate the fiber material directly reach the sound receiver and are evaluated. 2. The method according to claim 1, characterized in that sound transmitters and sound receivers are operated in the ultrasonic range. 3. The method according to claim 1, characterized in that the fiber material is limited by lateral boundary surfaces such that the sound waves are forced to penetrate the fiber material in order to get from the sound transmitter to the sound receiver. 4. The method according to claims 1 and 3, characterized in that the fiber material is arranged between the boundary surfaces in such a way that all sound waves that pass from the sound transmitter through the fiber material to the sound receiver penetrate approximately the same amount of fibers. 5. The method according to claim 1, characterized in that the sound transmitter (3) intermittently emits sound waves (4), and that only the beginning of the incoming sound waves (7) is evaluated by the sound receiver (8) and the time-dependent portion of the sound wave arriving later is suppressed in such a way that interference and resonances of sound waves of different duration are no longer taken into account by the sound receiver. 6. The method according to claim 1, characterized in that the sound receiver is arranged such that any disturbing sound waves from the outside must also penetrate the fiber material to get to the sound receiver and thereby experience the same attenuation as the sound waves from the sound transmitter. 7. The method according to claims 1 and 3, characterized in that the lateral boundary surfaces (5) are formed by parallel plates (21) with a fixed or variable distance. 8. The method according to claim 1, characterized in that the characteristic features of the fiber material, in particular the amount of fiber material (6) from the attenuation of the part of the incoming sound signals (7) selected on the sound receiver (8) is obtained. 9. The method according to claim 1, characterized in that the characteristic features of the fiber material (6), in particular the amount of fiber material, is obtained from the delay time of the arriving at the sound receiver (8), selected part of the sound signal (7). 10. The method according to claim 1, characterized in that sound waves of different frequencies are emitted by the at least one sound transmitter (22). 11. The method according to claims 1, 9 and 10, characterized in that the different propagation delay at different sound frequencies is used to compensate for the temperature dependence of the propagation time of the sound wave from the sound transmitter (3) to the sound receiver (8). 12. The method according to claims 1, 8, 9 and 10, characterized in that several characteristic features of the fiber material, such as, for example, the amount of fibers, fineness of fibers, and the mixing ratio, are determined simultaneously by a combined evaluation of damping and delay time at one or more sound frequencies. 13. The apparatus for performing the method according to claim 1, characterized by at least one sound transmitter (22) and at least one sound receiver (23), between which the fiber material (20) to be examined with regard to characteristic features is arranged, and by boundary surfaces (5) for guidance and limiting the fiber material (20), further by an electronic circuit for generating the sound signals and for evaluating the sound waves arriving at the sound receiver (23). 14. The apparatus according to claim 13, characterized in that the boundary surfaces (5) are designed as parallel plates (21) with a fixed or variable distance. 15. Device according to claims 13 and 14, characterized in that the plates (21) form a slot open on at least two sides, that the sound receiver (23) is acoustically shielded on the closed side of the slot and only with an acoustic opening (24) is provided against the inside of the slot, that there is at least one sound transmitter (22) on the opposite side of the slot, and that the fiber band (20) between the sound transmitter (22) and sound receiver (23) is used to measure the characteristic features the slot is guided. 16. The device according to claims 13, 14 and 15, characterized in that the measuring slot formed by the plates (21) is closed on the side opposite the acoustic opening (24). 17. Application of the method according to claim 1 for measuring the cross-sectional uniformity of strips and rovings. 18. Application of the method according to claim 1 for the measurement of the layer thickness of sheet-like amounts of fiber. 19. Application of the method according to claim 1 for controlling textile machines to achieve uniform fiber slivers. The invention relates to a method and a device for measuring characteristic features of fiber material, in particular the measurement of the amount of fibers in textile fiber bands, and the application of the method. Experiments have been carried out for some time and appropriate methods and devices have been developed to determine the amount of fibers in textile tapes using ultrasound. For example, refer to the patent of Heller (US No. 2 966 057), as well as the publication by Bobrov, Gorelik and Volosmikov, Teknologia Tekstilnov Promystchlennosti No. 4 (1973), 115. Nevertheless, it has not yet been possible to manufacture a device with sufficient accuracy and reliability on this basis. A major reason for this is the high interference ability of the sound waves. As a result, certain resonances occur at each arrangement, which considerably disrupt the linear or monotonic relationship between the amount of fibers and the size of the influence on the sound signal. Another problem in the determination of the amount of fibers by means of ultrasound arises from the fact that even very small openings suffice to falsify the measurement considerably if sound waves can get from the transmitter to the receiver through these openings without completely penetrating the fiber material. ** WARNING ** End of CLMS field could overlap beginning of DESC **.