US3053986A

US3053986A - Thread cleaner for textile machines

Info

Publication number: US3053986A
Application number: US108217A
Authority: US
Inventors: Loepfe Erich; Eichenberger Werner
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-12-31
Filing date: 1960-12-28
Publication date: 1962-09-11
Anticipated expiration: 1979-09-11

Description

Sept. 11, 1962 E. LOEPFE ETAL THREAD CLEANER FOR TEXTILE MACHINES Filed D90. 28, 1960 2 Sheets-Sheet 1 on tn mm am PM mm 0N N INVENTO [15: E. Loa /e m: N. Edchenberer ATTQ R-NEBS Sept. 11, 1962 E. LOEPFE ETAL THREAD CLEANER FOR TEXTILE MACHINES 2 Sheets-Sheet 2 Filed Dec. 28, 1960 an Ow "5 2m n0 m0 2. H m nmdE m fi 3 no on B 5 3 n 3 3 I N VENTQ RS 7 E. L oepfe. A W. ELc/zenb rge wwolav'g ATTQLNE 5 3 053,986 THREAD CLER FOR TEXTEE MACHINES Erich Loepfe, Im Rossweidli 62, and Werner Eichenherger, Turnerstrasse 26, both of Zurich, Switzerland Filed Dec. 28, 1960, Ser. No. 108,217 Claims priority, application Austria Dec. 31, 1959 8 Claims. (Cl. 250-419) This invention relates to a thread cleaner for textile machines.

The term thread cleaner is used in this art to describe a device applied to textile spooling machines of all types which contacts a running thread to determine its uniformity; if the threads have non-uniform spots, such as constrictions, thicknesses, coated spots, etc., the device emits a signal. This signal can be used to stop the spooling part in question, to cut the thread or to automatically clean the thread so as to remove the non-uniform spot. Consequently, the device of the present invention is not a measuring instrument, but a supervisory instrument for producing machines.

In prior art devices the threads is contacted mechanically; it runs through a screen provided with a hole, a slit or the like. A thickening in the thread will either brush against the screen, or the screen will be moved by the thickened thread in a manner which can be utilized to shut off the corresponding spooling part. Such mechanical cleaners do not operate satisfactorily; in particular, they do not respond at all to constrictions in the thread and they react to thickened portions only when they are very pronounced. The errors of these devices were found to be particularly disturbing during rewinding in view of thread speeds which have the tendency of becoming higher and higher.

Another prior art attempt of solving the problem of thread cleaning is based upon a capacitive supervision; this arrangement, as compared to the above-described mechanical devices, has the substantial advantage that the supervision is carried out without touching the thread. According to this arrangement, the thread moves through a small measuring condenser and the irregularities of the thread are registered by capacitive changes caused by the changes in the dielectric medium. This device, however, has two very substantial drawbacks: firstly, the examination is not based on an examination of the outlines of the thread, but upon the mass of the thread, or the efiect of this mass as a dielectric medium. The result is that the cleaner may be actuated when there is no mechanical defect in the thread but, for example, when there is a change in the moisture content, or, which is even worse, the moment of actuation may be shifted so that the device will not respond any more when actual defects occur. The second important drawback is that the measuring condenser in order to have good response must be made inconveniently small. This is caused by the fact that good sensibility requires a high emitted signal for a certain unevenness of the passing thread, which may be quite small in the case of fine yarns. Consequently, such unevenness must produce a relative change in the dielectric medium of the condenser, which should be as great as possible. This, however, can be accomplished only if the thread itself occupies a substantial part of the space between the condenser plates. Capacities resulting therefrom are very small and their measuring is bound with frequencies which are so high that they cannot be handled conveniently at a producing machine. Furthermore, the capacities of the wiring are of the same range as the capacity of the measuring condenser, so that the mechanical stability is also of a critical nature.

Prior art cleaners which utilize optical means, present a much better solution.

Contrary to the capacitive clean-.

Patented Sept. 11, 1962 ers they provide actual inspection of thread outlines. However, prior art optical cleaners have substantial drawbacks. They are based on the principle of a light screen, whereby the thread being examined passes through a bundle of light rays which is ejected by a light source and is received by a light receiver. When the thread is uniform, the light-electric cell of the light receiver receives uniform light, so that no signal is transmitted by the capacitive coupling of the cell to a magnifier. When the thread is not uniformwhether it be positively or negatively, the light current engaging the photo cell will be changed and the corresponding change in the photo-current is transmitted to the magnifier. It is a matter of general knowledge, however, that the brightness of a glow lamp changes to a great extent even when changes in the supply voltage are small. Therefore, in the case of optical cleaners provided with the usual light receivers, the lamp voltage of the light source must be very well stabilised, in order that the moment of operation and the sensitivity of the device should not be detrimentally infiuenced by the net voltage. Another great difliculty with prior art optical cleaners is caused by the dust. For example, when cotton is being treated, a film of dust will invariably settle upon the optic parts of the instrument and will absorb a substantial part of the bundle of light rays used for examination, so that the sensitivity of the cleaner is subjected to changes which are difiicult to control. If a device of good sensivity is to be provided, then the bundle of light rays must be made as narrow as possible (in a manner analogous to the small condenser in capacitive examination), so that a defect in the thread will produce a high relative change in the light current. However, such a thin bundle of light rays is affected to a considerably greater extent by dust, than a ray bundle with a larger cross-section, since static accumulations of individual dust particles afiect the light current of a thin ray bundle to a greater extent than that of a thick one. Furthermore, the usual cleaners which are constructively similar to light screens, respond only to thread outlines which are perpendicular to the axis of the ray bundle, and the cleaner does not respond at all to defective thread portions which extend, for example, in a plane containing the thread and the ray bundle.

An object of the present invention is the provision of an optical thread cleaner which will eliminate the drawbacks of prior art devices.

Other objects of the present invention will become apparent in the course of the following specification.

In accomplishing the objects of the present invention, it was found desirable to engage the thread simultaneously by two light ray bundles which preferably intersect each other at right angles. The two light ray bundles are projected in the light receiver upon a common light-receiving cell. The use of two light ray bundles which preferably intersect each other at right angles imparts to the instrument the important advantage that defects upon the surfaces of the thread are detected by the cleaner even when their plane by chance coincides with the axis of a light ray bundle. Furthermore, the use of two light ray bundles results in that a defect in the thread appears in double its size in the light-electric cell, which is equivalent to a twice greater sensitivity. Furthermore, in accordance with the present invention, the emitted electrical signal produced by the light receiver, is a function of the size of the light current reaching the light-electric cell, which is approximately a logarithmic one, at least within the operating range. Thus the sensitivity of the light receiver receives a sliding slope in such manner that the slope diminishes with an increase in the strength of illumination. Consequently, a slowly changing intensity of the examining light ray bundle-which may be caused by changes in the lamp voltage or by dust films-will not aifect the sensitivity, and the result is an outgoing signal which always remains the same for a specific defect of the thread, irrespective of the immediate ray intensity affected by variations in lamp voltage and dust.

According to another feature of the present invention, a part of the light emitted by the light source, is guided directly, without byways, outside of the thread being examined and to a second light-electric cell which also operates logarithmically in a manner analogous to the actual receiver cell; the outlets of the two cells are subtractively connected. As will be described in greater detail hereinafter, this compensation connection provides that even a quickly changing lamp brightness (such as a 100 hertz modulation for A.C., rapid changes in the net voltage, rapid changes of contact resistances, etc.) will not aliect the operation of the thread cleaner. The above described important characteristic of the logarithmically operating receiver remains thereby preserved.

Throughout this specification and claims, the term light source is used to describe that part of the device of the present invention, which consists of one or possibly several electric glow lamps and the lens-screen system pertaining thereto, said part being used for producing one or more limited light ray bundles. The lens screen system or systems can be set up from one lensscreen system or a single screen.

Throughout this specification and claims, the term light receiver is used to describe that part of the entire device of the present invention which is build up of a lensscreen system, a light-electric transformer and an amplifier. In this case also, the lens-screen system may consist of a screen system or a single screen. The lightelectric transformer includes means which transform light energy into electrical energy. The amplifier increases by electronic means the low output gauge of the signal supplied by the light-electric transformer to a higher gauge suflicient for actuating electro-mechanical elements.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings showing, by way of example only, preferred embodiments of the inventive idea.

In the drawings:

FIGURE 1 is a diagrammatic sectional view of the entire device of the present invention, wherein the two light ray bundles intersecting the thread at approximately right angles are produced merely by reflecting a single light ray bundle by a flat mirror.

FIGURE 2 shows the electrical connections of this device.

FIGURE 3 is a diagram illustrating the operation of the light receiver with a sliding curve slope.

FIGURE 4 is a diagram illustrating the coincidence of the characteristic curve of a silicon photo-element with the theoretical logarithmic curve.

FIGURE 5a illustrates diagrammatically electrical con nections and FIGURE 5b is a curve diagram; they illustrate the realization of the logarithmic characteristic curve of the receiver by a photo cell which has a current-saturation characteristic.

FIGURE 6a illustrates diagrammatically electrical connections and FIGURE 6b is a curve diagram; they illustrate an arrangement similar to that of FIGS. 5:: and 5! but with a photo resistance.

FIGURE 7 is a circuit diagram illustrating the provision of a logarithmic relationship by the introduction of non-linear switching elements into the amplifier.

FIGURE 8 is a diagram showing the simultaneous examination of several threads with the same device.

FIGURE 9 is a diagram illustrating the operation of the compensating cell.

FIGURE 1 of the drawings shows an electric lamp 2 having a glow wire 1 and a bulb 3. The entire light emitted by the lamp 2 is received by the screen 4 which screens a ray bundle 5. The ray bundle 5 is projected at an acute angle 6 upon a flat mirror 7. The thread 8 moves at right angles to the plane of the drawing in the middle of the ray bundle 5 and directly above the mirror 7. The mirror 7 reflects the ray bundle 9 which passes the thread 8 for the second time and then reaches the photo-electric cell 10.

An electronic amplifier 11 is used to amplify the signal supplied by the cell 10 until it reaches an output gauge sufiicient for the operation of a mechanical relay.

The lamp 2, the cell 10 and the amplifier 11 are located in a common casing 12, while the mirror 7 is carried by arm 13 attached to a side of the casing 12. The entire optical system is closed by a glass plate 14. The device may be screwed to a spooling machine (not shown) by means of the two flanges 15 and 16.

FIGURE 2 shows a transformer 17 the primary winding of which is supplied with electrical current from any suitable source and the secondary winding .18 of which provides feed voltages for the lamp 2 and the amplifier ii. The alternating current in the winding 18 is transformed into a pulsating direct current by a rectifier 19 and this pulsating direct current is flattened by two

filter condensers

20 and 21 and a filter resistance 22. The direct current which is thus produced provides the anode supply voltage for an amplifier tube 23 and a cold cathode thyratr on 24. The current impulse supplied by the silicon photo element 25 is transmitted to the potentiometer 26 having a connection 27 which is set in accordance with the desired sensitivity and which is connected with the grid 29 of the amplifier tube 23. The preliminary negative grid voltage produced in the cathode conduit by the resistance 3t is transmitted through the potentiometer 26 :to the grid. In order to avoid the appearance of an A.C. counter-coupling, the resistance 30 is bridged with the condenser 32.

The signal amplified by the tube 23 is conducted by means of the transmitter 33 located in the anode circuit, to the starter 34 of the cold cathode thyratron 24. If this signal reaches the size predetermined by the starter ignition voltage, then the main discharge of the thyratron on the side of the anode takes place and the relay 35 which is located in the anode circuit, is energized. The contacts 36 of the relay which are then closed, may cause the desired switching oif operations in the spooling machine (not shown).

Whenever yarns are used which by themselves have a non-uniform cross-section, it may be advisable to provide a cleaner which will respond to yarn defects which, besides having a predetermined transverse dirnension, also have a predetermined minimum length. To be able o test this minimum length, an integration network is ntroduced between the connection 27 of the potentiometer 26 and the steering grid 29. This network may consist, by way of example, of a resistance and a condenser 91 located between the grid 29 and the mass. By increasing this resistance, the integration constant of the network is increased and thus the time interval is extended, which is necessary in order to reach the actuating voltage.

FIGURE 3 illustrates a curve 37 which shows qualitatively the extent of the outgoing signal of the light receiver 25 which is to be transmitted, depending upon the strength of illumination. The abscissa 38 indicates the strength of illumination L and the ordinate 39 indicates the outgoing signal U. The immediate operative point is at 49. Let the change in light intensity dL caused by a fault in the yarn, be indicated by 41, and the change in the otugoing signal dU produced thereby, be indicated by 42. The analytic expression of the requirement of a constant sensitivity independent of the immediate location of the operative point 40, is given by the following Equation 43:

Integration of the ditferential Equation 43 produces the following Equation 44:

U:c in L wherein c and c are constants.

A curve corresponding to the Equation 44 is produced in very close approximation by a block layer photoelement, namely, by its open-circuit voltage.

FIGURE 4 shows by way of example experimental data obtained from testing a monocrystalline silicon photo-element, as compared with the theoretical curve required by the Equation 44. The abscissa 45 of FIG. 4 indicates illumination strength in luxes and the ordinate 46 shows the open-circuit voltage U supplied by the element in volts. Points appearing on the curve indicate actual values which were obtained experimentally, while the curve drawn between these points corresponds to the following Equation 47:

U (in volts):0.2.l0 log 1.86X10 L (in luxes) (47) FIGURE a shows a photo cell 48, the voltage-current characteristic curves of which are indicated in FIGURE 5b. The abscissa of FIG. 5b shows the voltage, while the ordinate shows the current. In the curves represented in FIG. 5b, the intensity of illumination was taken as the parameter, namely, the curve 49 represents a small illamination intensity, while the curve 52 represents a large illumination intensity. To this category of photo cells belong, for example, high vacuum cells and half conducting diodes operated in the block range. 53 is a nonlinear resistance consisting, for example, of a silicon carbide slag, wherein the current increases rangewise approximately exponentially with the applied voltage. If constant direct voltage is applied between the points 54 and 55, then the desired logarithmic relationship will exist between the voltage applied at the

points

55, 57 and the intensity of the bundle of light rays 56.

FIGURE 6a shows a photo resistance 58 having current-voltage characteristics which are illustrated in FIG. 6b, wherein again the x-axis indicates the voltage and the y-axis indicates the current. In this case also, the strength of illumination serves as the parameter, whereby the straight line 59 represents small strength of illumination and the straight line 62 represents a great strength of illumination. FIGURE 6a shows a voltage-dependent resistance 63 which is similar to the resistance 53 of FIG. 5a. While according to the arrangement of FIGS. 5a and 5b, a logarithmic relationship can be attained for any desired ratio of the two voltages 57, 54, in the arrangement of FIGS. 60 and 6b it must be assumed that the direct voltage applied between the points 64 and 65 is large in comparison to the one obtained between the points 67 and 65. However, if this requirement is fulfilled, then the arrangement of FIG. 6a produces the required logarithmic dependence between the intensity of the ray bundle 66 and the outgoing voltage between the points 67 and 65.

FIGURE 7 illustrates an arrangement wherein the logarithmic characteristic of the light receiver is produced by non-linear elements located in the electronic amplifier itself. As shown by way of example in FIG. 7, an outgoing signal produced by a linearly operating photo cell is applied to the grid 68 of a pentode 69. A voltage-dependent resistance 70of the type of resistance 53 in FIG. 5a and of the resistance 63 in FIG. 6ais located in the anode circuit of the pentode 69. Since the pentode has a saturation characteristic which is similar to that shown in FIG. 5b, the required approximate logarithmic relationship will exist between the outgoing signal 71 and the incoming signal 68.

FIGURE 8 shows an example of the device of the present invention, wherein several threads can be examined simultaneously. The only requirement necessary to attain this result is that all the

threads

72, 73' and 74 which are being examined, should be located in the .space 77 filled jointly by the two intersecting light ray bundles 75 and '76. The reflecting mirror described in connection with the device shown in FIG. 1, is indicated by 7.

FIGURE 9 illustrates an arrangement wherein the bundle of rays 5 which constitutes the actual rays being utilized, is emitted by the lamp 2, strikes the thread 8 and is deviated by the mirror 7 upon the light-electrical element 10. In addition, a second bundle of rays 78 is projected upon a second light-electrical element 79. The light-electrical elements 10 and 79 may consist, for example, of the silicon-photo elements illustrated in FIG. 4. The two elements 10 and 79 are interconnected in series in phase opposition.

Hereinafter it will be demonstrated that the outgoing signal 80 of the device fulfills the following requirements:

1) It is independent of the slow changes in the brightness of the lamp.

(2) It is independent of quick changes in the brightness of the lamp.

(3) It is independent of dust films.

For this purpose let the direct light portion of the total light current of the lamp be designated by L and the alternating light portion (quick change in brightness) be designated by LN; it will be also assumed that The light current of the useful light ray bundle 5 amounts then to and that of the compensating light ray bundle The initial voltage of the two elements 10 and '79 is assumed, in consideration of the Equation 44, to follow the following two equations:

Consequently, the characteristic features of the two elements 10 and 7-9 should coincide only as far as the constant 0 is concerned, but not the constant c A subtraction of the two voltages of the Equations 83 and 84- when taking into consideration the Equations 85 and 86, produces the following formula for the outgoing signal 86 (U of the entire device:

Since the first part of the expression 87 is eliminated 1n the case of capacitive coupling with the aid of the condenser 88, the AC. portion has the following equation:

A comparison of the Equation 89 with the Equation 43 shows immediately that the above-stated requirement 1 is fulfilled and due to the elimination of the constant k and the alternatinglight portion LN, the

requirements

2 and 3 are fulfilled also.

The two light-electrical transformers 10 and 79 with their inherent logarithmic characteristic can be also replaced by one of the arrangements shown in FIGS. 5a, 6a,

'5' or 7, whereby again care must be taken that the interconnection of the elements must be in counter phase.

The devices above described and illustrated in FIGS. 1 to 9, have been given merely as examples of the present invention. Various changes may be made therein within the scope of the present invention.

For example, the screen 4 shown in FIG. 1 or the entry opening of the light-electric cell may be replaced by a lens system.

This system can contain simultaneously lenses and screens.

The amplifier tube 23 and the cold cathode thyratron 24 can be replaced by other amplifying elements, for example, transistors.

Furthermore, it is possible to leave out the electromechanic relay at the outgoing side of the amplifier, so that the end stage of the amplifier will operate directly the electro-mechanical element of the corresponding spooling machine.

Furthermore, if several of the described devices are connected to the same spooling machine, the individual elements can be centralized. By way of example, it is possible to provide the entire current supply from a common single transformer.

The light ray bundles which, in accordance with the present invention, are used for examining the thread and which preferably intersect each other at right angles, can be produced by other means in the light sender. While the arrangement shown in FIG. 1, wherein a reflecting mirror is used, is considered to be the best and most effective solution, which is accomplished by the simplest means, the scope of the present invention should not be considered to be limited to this example.

If in the case of two testing light ray bundles which intersect each other at right angles, the remaining anisot-ropy in sensitivity is too great in special cases, then it is possible to use three light ray bundles which intersect each other at'angles of 60, or it is possible to use more light ray bundles intersecting each other at corresponding angles. These light ray bundles can all emerge from a single light ray source, or a separate light ray source can be used for producing each light ray bundle. In each case care must be taken, however, that the light ray bundles which are being used, should not diverge too much. "If possible, parallel or nearly parallel light rays should be produced. Such an arrangement will attain that changes in the position of the thread while it passes through the cleaner and resulting from vibrations, used up thread guides and the like, will not produce any changes in the sensitivity of the device. It should be noted that such a change in the sensitivity takes place in the case of greatly divergent light ray bundles as soon as there is a change in the distance between a thread and the cusp of the bundle. On the other hand, in the case of substantially parallel light rays the crest is sufiiciently far removed, so that small changes in position of the thread, due to its substantial distance from the cusp or crest of the light ray bundle, will not detrimentally alfect the instrument.

Practical experience has shown that a device of the present invention attains, with comparatively small expenditure, a very high sensitivity and particularly an exceptionally high stability with respect to dust, and also with respect to slow and quick variations in the net voltage and changes in the position of the thread being examined while it is passing through the cleaner. Due to these properties it is easily possible to supervise more than one thread with the same device. By way of example, in the case of a multiple spooling machine the same device can be used for examining all three threads which are to be joined.

Furthermore, in many instances it is desired that the cleaner should also respond to breakage of a thread. This requirement is also fulfilled by the device of the present invention, since in the case of thread breakage the 8 resulting change in brightness is generally larger than one produced by a defect in a thread. The supervision of thread breakages can be also carried out simultaneously with many threads.

To sum up, it may be stated that among the various thread cleaners known in prior art, the optical thread cleaner is best suited to satisfy the various requirements. The device of the present invention eliminates the following drawbacks of optical thread cleaners known in prior art:

(1) Its sensitivity is not affected by dust films due to the logarithmic characteristic of the receiver.

(2) Its sensitivity is independent of slow changes in the brightness of the sender due to the logarithmic characteristic of the receiver.

(3) Its sensitivity is multiplied by the use of two or more intersecting bundles of light rays.

(4) It also detects surface defects in the thread due to use of two or more intersecting bundles of light rays.

(5) Its compensation connection eliminates quickly changing difierences in brightness of the sender.

What is claimed is:

1. An electro-optical thread cleaner for textile spooling machines, comprising a light sender having means for emitting at least two intersecting light ray bundles for simultaneously contacting at least one thread, and at least one light receiver having means receiving light emitted by said sender after it contacts said thread, and means connected with the second-mentioned means for emitting an electric signal when a defect in the thread causes a change in the strength of illumination, the second-mentioned means and the third-mentioned means having at least a substantial logarithmic relationship between the strength of illumination and the emitted signal, whereby the two intersecting light ray bundles are adapted to detect a surface defect in the thread and whereby due to said logarithmic relationship the same emitted signal always corresponds to a predetermined extent of thread defect irrespective of dust particles located in the path of the light rays and a slowly changing brightness of the light sender.

2. A thread cleaner in accordance with claim 1, wherein the second-mentioned means comprise a barrier layer photo element having an open-circuit voltage characteristic providing said logarithmic relationship.

3. A thread cleaner in accordance with claim 1, wherein the second-mentioned means comprise a photo cell having a current-saturation characteristic and a voltage-dependent resistance connected in series with said photo cell, said voltage-dependent resistance having at least within a range a substantially exponential current-voltage dependence, said photo cell and said voltage-dependent resistance providing said logarithmic relationship.

4. A thread cleaner in accordance with claim 1, wherein the second-mentioned means comprise a photo resistance and a voltage-dependent resistance connected in series with said photo resistance, said voltage-dependent resistance having at least within a range a substantially exponential current-voltage dependent, said photo resistance and said voltage-dependent resistance providing said logarithmic relationship.

5. A thread cleaner in accordance with claim l, wherein the third-mentioned means comprise an electronic amplitier having non-linear elements providing said logarithmic relationship.

6. A thread cleaner in accordance with claim 1, further comprising a second light receiver receiving a light ray bundle which is emitted by said light sender and which does not contact said thread, said second light receiver also having said logarithmic relationship, and means interconnecting the two light receivers to subtractively mix the signals emitted by the two light receivers, whereby due to said logarithmic relationship between strength of illumination and signal, quick changes in brightness of 9 the light sender affecting all light ray bundles do not cause the emission of any signals.

7. A thread cleaner in accordance with claim 6, wherein said light sender comprises alternating current heating means capable of producing illumination pulsating with double net frequency of the alternating current.

8. An electro-optical thread cleaner for textile spooling machines, comprising means including a light sender and a plane mirror for producing two light ray bundles intersecting each other at a substantially right angle and illuminating a thread located substantially close to said plane mirror, said plane mirror reflecting a light ray bundle by substantially 90, and a light receiver having means receiving light ray bundles reflected by said plane mirror, and means connected with the second-mentioned means for emitting an electric signal when a defect in the thread causes a change in the strength of illumination, the second-mentioned means and the third-mentioned means having at least a substantial logarithmic relationship between the strength of illumination and the emitted signal, whereby the two intersecting light ray bundles are adapted to detect a surface defect in the thread and whereby due to said logarithmic relationship the same emitted signal always corresponds to a predetermined extent of thread defect irrespective of dust particles located in the path of the light rays and a slowly changing brightness of the light sender.

References Cited in the file of this patent UNITED STATES PATENTS 2,413,486 Denyssen Dec. 31, 1946 2,510,347 Perkins June 6, 1950 2,636,223 De Santis et a1 Apr. 28, 1953 2,962,596 Leimer et a1 Nov. 29, 1960