CS536482A2 - Method for determining density of a fiber bundle when defining cross section and apparatus for making the same - Google Patents

Description

In the textile industry, it is very important to determine the fiber content of fibers, in particular the fiber cross-section of fibrous webs. The fiber cross-section of the fiber strips is of great importance for further processing because it directly affects the fineness of the yarns and the uniformity of their cross-section.

Primarily, it is a question of how to determine the amount of fiber in a substance, regardless of whether it is moving or not. In principle, the continuous measurement of the fibrous webs does not differ, only the fibrous web supply and restriction device needs to be appropriately formed.

However, determining the weight, in particular of the moving fiber webs, is not practically feasible. Numerous ways to reliably measure the fabric cross section have therefore been proposed. By way of example, purely mechanical measurement by means of a grooved roller and a sensing roller in which the fiber strip is guided by a grooved roller and a meserage between the groove roller and the sensing roller as a measure of the fabric cross section. As a result of the high mechanical demands and the frequency limited by large mechanically moving masses, this device is only slightly extended. Also known are abrasive measuring devices that utilize the absorbent or reflective capability of the fibrous webs, which require very complex electrical and optical means, and the reliability of these systems is limited by that absorption or reflection of light depends on the color of the fibrous material.

Acoustic measuring organs are also known; the method uses and measures the damping of air acoustic waves that pass through the fiber web. However, the accuracy of this measurement is not satisfactory.

Another of the series of measuring devices for measuring the fiber cross-section of fiber webs is the so-called actively pneumatic measuring element. Such a member consists essentially of a funnel to which a pressure measuring device is connected from the side. When the fiber web passes through the funnel, there are pressure fluctuations on the side connection which correspond to the instantaneous cut and are not converted into equivalent signals in suitable converters. Such an active pneumatic measuring element is structurally simple. However, the measured value depends both on the fineness of the fibers and on the speed of their passage.

The disadvantages of the known measuring systems are eliminated by the method according to the invention, characterized in that the elastic and / or dynamic behavior of the fluffy amount is determined in the space defined in the volume defined by the flat. It is also an object of the present invention to provide a method for carrying out this method, characterized in that a defined or defined cross-section is provided, in particular a precisely defined conduit in the form of a tube, funnel or trumpet in which the elastic and / or non-dynamic behavior of the fiber web can be measured .

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained with reference to the drawing, wherein FIG. Fig. 4 shows a measuring device for determining the transmission function in the measured material, Fig. 5 a pulse diagram, Fig. 6 a first variant of the measurement method according to Fig. 4, Fig. 7 another variation of the measuring method FIG. 9 is a cross-sectional view of another shape of a clearly defined space; FIG. 11 is a longitudinal sectional view of a measuring device; FIG. 12 is a longitudinal sectional view of a radiator or receiver;

The invention is based on the following observations: Textile fibrous amounts are formed by the rule of fiber formation with very large air gaps. Even a distinct compression is a net material fraction or fiber mass relatively small. For example, in carding machines it represents only 10 to 20%. When the free fiber amount is compressed (Fig. 1), a force-elongation curve is produced with a certain course as shown in Fig. 1. 2. Because tensile forces must not be applied to the filamentous amount, but only to compressive forces, the elongation in this case corresponds to compression, namely to the normal dependence of force and elongation for the rigid body. In the graphical representation of Fig. 2, the axis of the segments is plotted by the extension ((compression) and on the axis of the ordinate P the curve 1 is produced. The modulus of elasticity E can be expressed at each point of this curve by the tangent of the angle forming the tangent 2 to curve 1 with horizontal 3: E = tgo </ (1)

The observations have shown that a certain fibrous amount and therefore a certain modulus of elasticity correspond to a certain fibrous density. The term fibrous amount refers herein to an average value of the fibrous material mixture and the air in the fibrous material gaps. Consequently, the fabric cross section Q q of the fibrous web is equal to the cross section Q of the fibrous web multiplied by the feed factor F.

The change in force or modulus of elasticity in dependence on density is highly expressed. It follows from the invention that, at any point in which the total fiber quantity occupies a defined space or a non-defined cross section, the compression force or modulus of elasticity can be determined precisely and directly and the density, Z density and the defined space or cross section can be determined. net amount of material.

However, it should be pointed out that the force or modulus of elasticity depending on the compression at a larger 6 count of the same fiber yield gives the same results. Especially in the first compression of the free-fiber quantity, a greater force is needed than in the subsequent compression processes. It is therefore advantageous to evaluate only the results of the first compression or merely the results of repeated compression to determine the substance of the invention. It is particularly advantageous here to determine the compression in the tubes or in the funnels of the carding machines, the drawing machines or the like, since the fibrous quantities therein usually lead continuously from the free position to the tapered point and thus always the first compression. A further advantage of such measuring points is that it is possible to define precisely the outer cross-section of the fiber web. Since this application is probably the most common application of the measuring element according to the invention, the measurement of the determination of the amount of fiber webs which are guided by a certain cross-section is mainly discussed below. Basically, the same considerations apply to the measurement of material at rest in a precisely defined space. Direct determination of the compression force of the running fiber web is difficult for practical reasons. For this reason, it is preferable to determine the modulus of elasticity from which to estimate the density. The implementation of the idea of the invention can take place in several variants. According to the first variant 7, the fibrous amount can be considered a spring »

It is known that a simple oscillating system of mass and spring assemblies. Resonance frequency can be determined from this mass and the elastic constant. When, according to the invention, as shown in FIG. 3, the body 4 with a predetermined weight is pressed against the fibrous web 5 forming the spring, an oscillating system is also produced. The frequency itself is determined by the mass of the body 4 and by the constants (elastic modulus E) of the fiber web 5. Alternatively, the elastic constants and masses of the fastening elements of the body 4 are respected. The fiber web 5 can also move in the tube or funnel 6, sliding below When the density of the fibrous web 5 is changed, the modulus of elasticity E changes, and consequently the resonance frequency. From this, the density of the fiber web can be determined. The excitation of the oscillating system, which consists of mass and spring, is a known measure and does not need to be explained.

A further embodiment of the method according to the invention is the determination of the transfer properties. Each solid, liquid, or gaseous medium has a certain velocity c and a deflection with this damping or transfer function. The speed of propagation is often referred to as the speed of sound. The propagation rate c can be calculated from the equation

where E is the modulus of elasticity aD is the density.

These patterns are known from general physics.

According to the invention, it is assumed that there is some analogy to the fiber behavior of the transfer behavior in homogeneous solid, liquid or gaseous bodies. While the transfer in homogeneous bodies occurs in the molecular domain, that is to say, from molecule to molecule, fibrous amounts occur in the macroscopic field. it means fiber to fiber. A further deviation from the analogy with homogeneous bodies is that in them the transfer behavior is determined by virtually constant material constants. However, in the case of fibrous formations, the density and, in particular, the elastic modulus are dependent on compression, and vice versa.

This is used according to the invention in that the determination of the transfer function, preferably the rate of propagation, gives the density of the fibrous amount and thus, for example, the fabric cross-section.

FIG. 4 shows the principle of a method for determining velocity and / or damping in a stationary or running fibrous web. The device consists of a tube or funnel 6 shown in longitudinal section, and a transmitter 7 which is capable of generating mechanical deformations and transmitting them through a fiber web. For this purpose, piezo-electric crystals are particularly suitable when, for example, a pulse 9 is transmitted from the transmitter 7 to the fiber web, propagated at the propagation rate cΊ, and with some d and d after a certain interval t, is received by the receiver 8. The receiver 8 can also be formed by a piezoelectric crystal.

The interval ^ (FIG. 5) corresponds to the exact density of the double-stranded belt 5. When the fiber bundle is free, the spread rate is small and the damping is large. As the bundle is densified, the rate of propagation increases and the damping decreases. Consequently, the density D of the fibers and hence the net fabric cross section of the fiber web can be determined from the propagation rate and / or damping (Fig. 5). the pulse is delayed from the interval transmitter 9.

A variant of the apparatus of FIG. 4 may be a device of FIG. 6. According to FIG. 6, the transducer 11 is simultaneously designed as a transmitter and receiver, and the funnel acts as a reflector 12. The pulse is thus a lumen 5 twice, that is, there. and back, and comes with a delay of 2 ~ as received signal to transducer 11, again with a certain muting.

Equivalent measurement of interval ^ is also utilization of resonant frequency f of oscillating system formed by feedback (Fig. 7).

Since the resonance frequency is inversely proportional to the interval · ^, the density of the double-strand belt can be determined in this way. The oscillating system is excited by a suitable coupling 14 between the transmitter 7 and the receiver 10 10 in the resonance region. , which controls the frequency of the emitter 7 from the phase position on the receiver 8. In doing so, the resonance system produces not only feedback, but also within the fiber quantity. There, there are already resonances, which are additionally excited by feedback. Their resonance frequencies are inversely two times the interval ^.

This method is particularly suitable for measuring moving fiber bundles which, by their movement in the receiver, produce a strong noise as a disturbing signal. With the aid of resonance systems, these interfering signals can be virtually eliminated.

Other resonant frequencies also correspond to the fundamental fundamental vibration. The measuring boats used in the methods of the invention are preferably used on textile machines, where the material is more or less continuous and the fibrous amount passes through a precisely defined cross-section, for example, carding machine funnels and the like. tracking members, or may serve to control and / or regulate the fiber quantity.

FIG. Figures 8 to 10 show examples of guide members of a bundle, for example funnels. Fig. 8 is a cross-sectional view of the cross section. The transmitter 7 and the receiver 8 are inserted from the side wall of the funnel 6 filled with the fibrous web δ. 8, they are preferably not adapted to a circular shape but are planar parallel so that the distances between the active surfaces 19 are equal.

FIG. 9 shows a respective longitudinal section. Transmitter 7a receiver 8 protrudes slightly into space. The skewing 13 on the transmitter 7 and the receivers 8, which are located 20 in the passageway of the fiber web 5, facilitates its passage through the funnel 6.

FIG. 10 shows a square cross section of a funnel 6 with a transducer 7 and a receiver 8. However, other cross-sectional shapes are also possible, for example oval or polygonal.

FIG. 11 shows an example of a funnel structure used, for example, in a carder machine. Disregarding the mounted transmitter 7 and receiver 8, the funnel is structurally exactly the same as the most commonly used carder funnels. The fibrous web 5 passes through the accelerator 6. In such a funnel 6, according to the invention, the pulses X can pass through the fibrous web 5 into the receiver 8, since the outer web the cut of the fibrous web 5 is precisely defined, the density and thus the modulus of elasticity are given. Thus, the net fabric cross section of the fiber web 5 can be deduced from the transfer behavior,

FIG. 12 shows, by way of example, a transmitter 7 in section. 12

The outer body 11 shown in FIG. 11 is formed so that a membrane 12 is formed to secure and protect the piezoelectric crystal 15, 16 against the fiber web 5. The bevel 13 facilitates the passage of the fiber web 5 in the direction of the arrow. the piezoelectric crystal force 15, 16 on the center of the diaphragm 12, the electrical voltage can be applied to the two piezoelectric crystals 15, 16 and thereby deform. The screw 18 serves to lightly press the piezoelectric crystals 15, 16. From an electrical point of view, it must be ensured that the polarity of the piezoelectric crystals 15, 16 is identical to that of the line 17 and the mass. The tension is applied between the conduit 17 and the mass, the mass being composed of the outer body 11, the bolt 18 and the punch 14, the Tatoconstruction with the punch 14 and the diaphragm 12 being more preferred, where the fibrous web 5 touches the piezo-electric crystal directly. The same construction can be used as a receiver 8. It receives a signal between the mass and the line 17.

The method according to the invention and the apparatus for carrying it out, as shown in particular by the example in FIG. 11, has the great advantage that the existing machine part, namely the nozzle 6, can be adapted to a measuring member. There is no formation of such a gauge to determine the fabric cross section of the fiber webs. So (at all problems. 13

In connection with the problem of using the elastic modulus to determine the fiber density, it is to be noted that the modulus of elasticity in the static measurement need not necessarily be as large as in the dynamic measurement. However, this difference is irrelevant to the principle of determining the fiber density.

Claims (8)

the patent claim is to calculate Cp r = ΠΠί ', whereby the modulus 1 θ lne depends on the density, n 1. A method for determining the density of a fiber bundle in a plurality of fibers. c eny l t, w w e e? 1 {114 s t o t y; n} is carried out by the modulus (E) and the fiber bundle is affected by changes in the mechanical thickness from which the beam propagation velocity (c) is density. (D) based on formula c = / - 'elasticity is over-proportional dependent on. Increases at increasing rate (c) of sulfur. Method according to claim 1, characterized in that the passage time (Z) of the change in the fiber bundle is measured and the propagation rate (o) is determined from the formula and is the distance between the transmitter and the pressure change receiver. 3. Method according to claim 2, characterized in that, in the bundle of the cells, you have 7- Z '' * 1, λ · »~ r -i - i in GCL '3 £ ρ G Ca t GV ώ u G even varnish tangle. 'ypoci-0 aoaa pru ui.u 4. Method according to claim 3, characterized in that the excitation frequency for the resonance frequency is set to the reciprocal value of the passage time or to. the value of the integral multiple of double the passage time, the frequency of the pressure transmitter being controlled based on the phase position on the receiver. 2 5. Apparatus for carrying out the method according to claim 1, comprising a fiber bundle guiding means, a mechanical oscillation transmitter and receiver, and a measuring device, characterized in that the guiding device (6) comprises a housing in which the guiding means (5) is of the fibers is arranged with a measuring zone of constant cross-section, in which walls a transmitter (7) and a receiver (8) of mechanical vibrations are mounted, the measuring device being formed as a phase meter (14) whose input is connected to the receiver output (8) and output with transmitter input (7). 6. Apparatus according to claim 5, characterized in that the transmitter (7) and the mechanical oscillation receiver (8) are disposed at opposite sides of the measuring band relative to the direction of movement of the fiber bundle (5). 7. Apparatus according to claim 5, characterized in that a reflector (12) is disposed on one side of the guiding means (6) relative to the direction of movement of the fiber bundle (5) and a transducer (11) for transmitting and receiving mechanical vibrations is arranged on the other side. . 8. Device according to claim 5, characterized in that the channel of measurement of the channel is formed by a membrane (21) firmly connected to the piezoelectric crystals (15, 16). 9. Apparatus according to claim 5, characterized in that the mutually facing surfaces of the transmitter (7) and the mechanical oscillation receiver (8) have bevels (22) in the direction of the beam passage (5).