Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means

Definitions

• the invention relates to a method for frequency analysis on moving fiber collectives according to the preamble of
• the main disadvantage of laboratory determination of the fiber parameters in accordance with the prior art lies in the discontinuous adjustability of the production machines, as is not otherwise possible on the basis of individual measurements of the fiber parameters carried out in the laboratory. This means that the setting of production machines cannot be permanently optimized.
• the invention seeks to remedy this.
• the invention has for its object to provide a simple, reliable method for frequency analysis on moving fiber collectives create with which a change in the frequency spectrum can be determined practically without delay and thus relative statements about the fiber parameters can be made.
• the invention achieves the stated object with a method which has the features of claim 1 and a device which has the features of claim 10.
• the fibers should be approximately parallel within the nonwoven, i.e. have a certain pre-parallelization.
• the movement of the non-woven fabric takes place either by means of a flow medium or by a transport device (e.g. air flow, clothing drum, needle bed, etc.)
• the fibers to be analyzed are expediently guided past the sensor in the form of a thin nonwoven fabric, preferably comprising a fiber layer.
• the sensor continuously measures a part or the entire width of the fleece. It can either be attached stationary, relative to the moving nonwoven fabric, or can be arranged so as to be movable, the speed being different from that of the nonwoven fabric.
• the sensor can consist of a capacitor, a CCD camera or a reflection measuring device, in which reflective light is used with directed light, for example laser light Surfaces of the transport device are illuminated and the reflected light is collected by means of a light sensor.
• the sensor measures the amount of fibers capacitively or optically and sends a correspondingly proportional signal to an evaluation unit.
• the evaluation unit can either be structurally separate from the sensor or can also be part of the sensor.
• the signal processing takes place in the evaluation unit, i.e. the separation of the interference signals from the useful signals, the amplification of the difference signals obtained in this way and the calculation of the frequency spectrum based thereon.
• the evaluation unit should have at least one input amplifier, intensity regulator, filter, computer and an interface to the user.
• the evaluation unit processes the signal generated by the sensor, which is proportional to the fiber quantity, and in this way determines a time diagram of the fiber quantity fluctuation in the measuring range of the sensor. Using the Fast Fourier Transformation (FFT) the evaluation unit can now calculate the frequency spectrum of the sensor signal.
• FFT Fast Fourier Transformation
• the signal generated by the sensor is stored in the evaluation unit before it is processed, preferably with a high clock frequency.
• the transport device of the nonwoven fabric and other interference units cause additional, undesirable frequencies in the spectrum of the sensor signal. If these interference frequencies are not already known in advance and can therefore be eliminated by calculation, a second sensor can be attached to a fiber-free point of the transport device or the flow medium, which can now measure these interference frequencies alone. The frequency spectrum of this sensor signal without fiber influence can then be subtracted from the frequency spectrum with fiber influence in the evaluation unit. This gives you exactly the frequency spectrum of the fibers without system-related interference frequencies.
• the advantages achieved by the invention are essentially to be seen in the fact that, thanks to the frequency analysis of the moving fiber collective obtained with the method according to the invention, on the one hand conclusions on the relative fiber parameters (changes in the fiber length, the dirt content, etc.), but on the other hand control of the fiber processing machines can also be carried out.
• the relative length measurement of the fibers results directly from the frequencies of the determined spectrogram. As the frequencies decrease, the fibers become longer; if the frequencies increase, the fibers have become shorter. A change in the fiber damage of production machines (eg cards) can be determined practically without delay.
• Fibers with defined properties have been included, the absolute parameters of the examined nonwovens can finally be determined.
• Two sensors can also be used, which measure the moved nonwoven fabric once before and once after a processing process (eg drafting system), so that the differential frequency spectrum of the two is obtained from the two sensor signals in the evaluation unit by means of the Fast Fourier Transformation Sensor signals can be calculated, which is directly related to the machining process.
• a processing process eg drafting system
• the machine setting can be continuously optimized by appropriate interventions in the fiber production machine.
• Fig. 1 shows a schematic representation of the device for performing the inventive method
• FIG. 2 shows a schematic representation of the various signal processing stages.
• the device for frequency analysis on moving fiber collectives shown in FIG. 1 essentially consists of two sensors 1 and 2, the transport device 6 for the fibers and the evaluation unit 7.
• the sensors 1 and 2 comprise both a transmitting part 15, 16, 18 and a receiving part 19.
• the transmitting part consists of a semiconductor laser 16 which generates laser light with the wavelength lambda - 670 nm and with With the help of a mirror wheel 15 and a mirror 18, a line pattern is drawn on the conveyor belt 6 underneath.
• the light beam moving back and forth across the conveyor belt 6 illuminates the film passing by. rende collective of fibers 5.
• the receiving part of the sensors 1 and 2 consists of a photodiode 19, which reflects the intensity of the laser beam reflected by the conveyor belt 6 and its structures (fibers 5, trimmings 3, etc.) and deflected by the semi-transparent mirror 17 and measures.
• the transport device 6 consists of a motor-driven conveyor belt which, on its surface facing the sensors 1 and 2, has regularly arranged sets 3 in the form of hooks which hold the collective of fibers 5 to be measured at the measuring fields 4 of the sensors 1 and 2 passes.
• the parts of the conveyor belt 6 lying between the sets 3 are mirrored (with the highest possible degree of reflection with respect to the illumination source used) in order to reflect the laser light emitted by sensors 1 and 2.
• the evaluation unit 7 which is shown in more detail in FIG. 2, essentially consists of two signal processing units 10 (for the signals generated in the sensors 1 and 2) and a computer 14, which in turn has two Fast Fourier Transformation units 11 and two interfaces 12, 13 to the user.
• the sequence of the method according to the invention is shown schematically on the basis of FIG. 2.
• the light intensities measured by sensors 1 and 2 are converted into electrical signals and in the two assigned signal processing units 10 amplified, filtered and subjected to an analog / digital conversion.
• the signals generated by sensors 1 and 2 can, if necessary, be stored in evaluation unit 7 before they are processed, preferably at a high clock frequency.
• the processed signals are now fed to the computer 14 and there subjected to a Fast Fourier transformation 11.
• the frequency spectrum of the sensor signals is calculated from the time diagram of the fiber quantity fluctuation or the clothing fluctuation in the measuring fields 4 of the sensors 1 and 2.
• the frequency spectra of the two sensor signals calculated in this way (once with fiber influence by sensor 1 and once without fiber influence by sensor 2) can then be mathematically subtracted from one another in evaluation unit 14.
• the group of 3 signals appearing on the left of the front of the schematic block representing the Fast Fourier transform 11 corresponds to the fiber information
• the signal appearing in the middle of the spectrum corresponds to the sets 3
• the signal arranged to the far right corresponds to the signals present in the system Dirt particles.
• the frequency spectrum freed from all external influences can now be supplied to the output / input unit 9 via the interface 12 and to the machine control 8 via the interface 13.

Landscapes

• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Treatment Of Fiber Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4226339

Family Applications (1)

Country Status (4)

Families Citing this family (5)

Family Cites Families (5)

• 1989
  • 1989-06-06 CH CH212089A patent/CH678230A5/de not_active IP Right Cessation
• 1990
  • 1990-05-11 WO PCT/CH1990/000127 patent/WO1990015325A1/de not_active Application Discontinuation
  • 1990-05-11 JP JP50689190A patent/JPH04500272A/ja active Pending
  • 1990-05-11 EP EP19900906840 patent/EP0427824A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events