US3390441A - Apparatus and method for reducing the number of unnecessary cuts of yarn - Google Patents

Description

July 2, 1968 E. FELIX 3,390,441

' APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARY cu'rs 0F YARN Filed Dec. 6, 1966 2 Sheets-Sheet 1 11. Fig.3 I

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APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARY CUTS OF YARN Filed Dec. 6, 1966 2 Sheets-Sheet 2 Fig.6 H r E IN VE'NTOR EnNsT FEL 1x ATTOZZEYS United States Patent Ofice 3,390,441 Patented July 2, 1968 3,390,441 APPARATUS AND METHOD FOR REDUCING THE NUMBER OF UNNECESSARY CUTS OF YARN Ernst Felix, Uster, Switzerland, assignor to Zellweger Ltd., Uster, Switzerland, a corporation of Switzerland Filed Dec. 6, 1966, Ser. No. 599,481 Claims priority, application Switzerland, Dec. 13, 1965, 17 ,249/ 65 18 Claims. (Cl. 28-64) ABSTRACT OF THE DISCLOSURE An apparatus and method for controlling the sensitivity of a yarn cleaner in dependence on the detection of a slub or double thread. A store records whether a cut is made due to a slub or double thread and subsequently controls the sensitivity of the yarn cleaner in dependence thereon at least during reinsertion of the cut yarn cleaner.

Usually electronic yarn cleaners are able to detect double threads in the yarn passing through them without any particular difficulty. However, when a double thread is cut, the yarn has to be reexamined for the presence of a double thread when replaced in the yarn cleaner since the cut double thread can be extremely long in some cases. Thus, a. particular problem is presented in detecting double threads after the yarn is replaced in the yarn cleaner.

Since yarns are known to undergo fairly marked variations in cross-section, being non-uniform to a greater or lesser extent, double threads in the yarns are also nonuniform to a greater or lesser extent. If the yarn travels through a yarn cleaner at an adequate speed, for example, at a winding speed, fluctuations in thickness can be averaged out over a fairly long section. In such a case, the mean value corresponds to the normal cross-section (100%) of the yarn or to twice the normal cross-section (200%) in the case of a double thread. However, unless the yarn is introduced into the yarn cleaner, only a very short length is available for a cross-section measurement. In many cases, this short length of yarn will presumably have a cross-section of approximately 100%, or 200% in the case of a double thread. Due to the irregularity of the yarn, however, greater differences can occur in isolated cases. For example, a thin part of a double thread with 140% of the normal cross-section can he accidentally inserted into the cleaner. On the other hand, a single thread could even be inserted which, at the point of entry, has a thick section of 140% (+40%).

A diagram of the cross-section pattern will show that thick sections such as these are by no means rare. In order to detect the aforementioned double threads, the cleaner should not be adjusted in such a way to only respond with certainty to the insertion of a yarn with a 200% cross-section but rather should also respond to a cross-section of 140%.

By contrast, the single thread is also cut in the aforementioned case due to the accidental slub of 140% thickness. For this reason, it is impossible to prevent a certain percentage of single threads being cut for an almost one hundred percent detection of these double threads. In the case of a uniform yarn, the percentage is somewhat smaller but is a little larger in the case of an irregular or non-uniform yarn. Although the percentage can be reduced in the case of irregular yarns, by increasing the response limit of the cleaner, the percentage of double threads which are not detected on introduction is thereby increased.

In comparison with the defective slubs, double threads are fairly rare. The probability of a slub and a double thread occurring simultaneously at the same place, is practically nil. Consequently, most cuts are made to remove slubs in conventional cleaners which detect both slubs and double threads, each re-insertion is accompanied by an examination or inspection for double threads which can result in a fairly large number of needless cuts on insertion.

Briefly, the invention relates to an apparatus and method for reducing the number of needless cuts of yarn by yarn cleaners having a discriminator for detecting slubs, a discriminator for detecting double threads and a cutting unit which reacts to a signal from either discriminator. The apparatus of the invention includes a circuit arrangement having a store or storage circuit on which at least one of the discriminators acts and a control member which responds to the condition of the storage circuit. The storage circuit reacts to an output signal from either of the discriminators when a yarn is cut to store the signal and to adjust the sensitivity of the double thread discriminator with respect to the stored signal. In addition, the storage circuit includes a means for erasing the stored signal after the occurrence of a subsequent predetermined signal from the slub discriminator or upon the re-insertion of a yarn in the cleaner.

The method of the invention includes the steps of passing a yarn through a yarn cleaner to detect the pressence of a slub or double thread by emitting signals corresponding to the presence of either. The signals are directed to a common store for adjusting the sensitivity of the yarn cleaner in dependence on the signal received whereby when a double thread is detected the sensitivity of the yarn cleaner is adjusted to a high value and when a slub is detected the sensitivity is adjusted to a low value. The method also includes the step of erasing the stored signal emitted in response to the presence of a double thread in order to reduce the sensitivity of the yarn cleaner. This step is actuated upon the occurrence of a signal of predetermined value in response to the subsequent detection of a slub or upon re-insertion of the yarn in the cleaner.

Accordingly, it is an object of the invention to reduce the number of needless cuts of a yarn cleaner by adjusting the sensitivity of the yarn cleaner in response to the detection of slubs and double threads.

It is another object of the invention to provide a simple efiicient apparatus and method for a yarn cleaner for adjusting the sensitivity of the cleaner.

It is another object of the invention to store a signal in response to the detection of a slub or double thread by a yarn cleaner and to adjust the sensitivity of the yarn cleaner in response to the stored signal.

It is another object of the invention to erase the above stored signal corresponding to the detection of a double thread upon subsequent detection of a slub in order to. lower the sensitivity of the yarn cleaner.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 graphically illustrates the frequency of occurrence of slub and double thread thicknesses in a yarn;

FIG. 2 illustrates a block diagram of a conventional yarn cleaner;

FIG. 3 illustrates a block diagram of a yarn cleaner incorporating a store according to the invention;

FIG. 4 schematically illustrates a circuit arrangement for a slub discriminator;

FIG. 5 schematically illustrates a circuit arrangement for a double thread discriminator;

FIG. 6 schematically illustrates a circuit arrangement for a store of the invention; and

FIG. 7 schematically illustrates a common circuit arrangement for slub and double thread discriminators and a store.

Referring to FIG. 1, the frequency of occurrence of the distribution of cross-sectional frequencies of a single yarn 10 and a double yarn 20 are plotted with the cross sectional values Q as the abscissa in percentage of the average cross-section and the relative frequencies f for each of the cross-sectional values Q are plotted as the ordinates. The greatest frequency for single yarns is found at Q=100% while the greatest frequency for double yarns or threads is found at Q=200%.

Thus, if the response limit of a yarn clearner is set at 200% for double threads, then only 50% of the double threads passing through the yarn cleaner are detected while all the double threads of an overall cross-section less than 200% (in this case, 50% of all double threads corresponding to the overall frequency at 200%) are ignored. On the other hand, only those slubs which take up 200% of the normal cross-section are separated out although their frequency is extremely low. If, by contrast, the response limit of the yarn cleaner is set at 100%, every single yarn with a cross-section of 100% and more is cut, i.e. 50% of all cases. In this instance, all but 0.2% of all the double threads are detected since, according to the statistical distribution, only 0.2% of all double threads have an overall cross-section of less than 100% of the normal cross-section. However, such high sensitivity is not desired because it reduces production very considerably.

It is possible, however, to find a suitable compromise by setting the response limit of the yarn cleaner at 140% for example. In this case, the number of needless cuts is reduced to On the other hand, the number of double threads which are not cut increases to 5%. While the percentage of needless cuts reaches the generally acceptable limit with such a response limit, the percentage of double threads which are not out still remains excess1ve.

Referring to FIG. 2, a yarn cleaner for the detection both of slubs and a double threads of a yarn 1 has a measuring head 2 for passage of the yarn 1 in which associated amplifiers (not shown) may also be accommodated. The yarn cleaner includes a discriminator 3 for slubs which emits a signal to a cutting unit 5 when a slub passes through and a discriminator 4 for double threads which likewise emits a signal to the cutting unit 5 when a double thread passes through.

Referring to FIG. 3, a yarn cleaner, as above, additionally incorporates a store 6 according to the invention which is controlled by at least one of the two discriminators 3, 4 and acts upon the sensitivity of the discriminator 4 depending upon the storage condition. The sensitivity level could, of course, also be varied elsewhere, for example, in an amplifier accommodated in the measuring head 2. As already mentioned, sensitivity must be controlled at least during the insertion or introduction phase of the yarn. In order to achieve this object various modifications are possible both in the manner in which the store is controlled and in the manner in which the store is erased. For example, the signal generated by the discriminator 3 can be retained in the store 6, in which case the sensitivity of the discriminator 4 can be lowered for the double thread channel. Alternatively, it is possible for the signal generated by the discriminator 4 to be retained in the store 6 and the sensitivity of the discriminator 4 increased since its sensitivity is normally fairly low. If, however, a cut is initiated by a double thread, the sensitivity of discriminator 4 is increased. As already mentioned there are numerous alternatives for erasing the stored signal. Also, the store 6 can be controlled both by the discriminator 3 and by the discriminator 4, in which case the sensitivity of the discriminator 4 is reduced where the store 6 is controlled by the discriminator 3, and increased where it is controlled by the discriminator 4.

Referring to FIG. 4, discriminator 3 for detecting slubs consists of a conventional Schmitt trigger which releases a signal at an output 22 when a predetermined input voltage is exceeded at an input 21.

Referring to FIG. 5, one example of a discriminator 4 for double threads consists of an RC-section and a Schmitt trigger. The RC-section has an input 31 which permits only signals for coarse or double threads to pass and the Schmitt trigger only releases a signal at an output 32 when a predetermined output voltage of the RC-section is exceeded.

Referring to FIG. 6, a store circuit arrangement consists of a conventional bistable multivibrator wherein the inputs 41, 42 of the bistable multivibrator are connected to the outputs 22, 32 of the discriminators 3 and 4. If, therefore, a double thread, for example, passes through the measuring head, the discriminator 4 releases a signal at output 32 and hence at the input 41 of the bistable multivibrator making input transistor 43 conductive. The signal at one of the collectors of the bistable multivibrator can then be used for sensitivity control.

Referring to FIG. 7, a circuit arrangement incorporates not only a discriminator 3, discriminator 4 and store 6, as above, but also uses certain elements in common. For example, a transistor 55 acts as an output transistor both for the discriminator 3 and the discriminator 4. On the other hand, the inputs of the transistors 51 and 53 are still independent of one another so that the circuit is as it were formed by two Schmitt triggers with separate inputs but a common output. The bistable multivibrator is also included in this circuit and consists of the transistors 52 and 54 and of the resistances 56, 57, 58 and 59. In this case, the multivibrator is directly controlled by the collector currents of the input transistors 5Land S3.

The circuit arrangement of FIG. 7 operates as follows. If, for example, a slub appears, a corresponding ON-signal is generated at the input 41 and the transistor 53 becomes conductive. As a result, the transistor 54 also becomes conductive, and remains conductive even after the signal at the input 41 has disappeared thereby blocking the transistor 53. If, on the other hand, a double thread appears, the transistor 51 becomes conductive, as does the transistor 52 which also remains conductive even after the signal at the input 31 has disappeared. The response limit or sensitivity of the Schmitt trigger can be varied by means of the resistances 56 and 57. If, for example, the resistance 56 is greater than 57, the sensitivity of the Schmitt trigger is higher when the transistor 52 is conductive. Accordingly, the required objective is achieved because there is an increase in sensitivity on the arrival of a double thread. The sensitivity remains high until a sufiiciently large signal appears at the input 41, as a result of which the transistor 53 or 54 becomes conductive and the bistable multivibrator flips, i.e. the sensitivity is lowered again after the arrival of a slub.

Although the required objective is in principle obtained with circuits in which the discriminator 3 erases the store 6, circuits of this kind are attended by a disadvantage. For example, if a yarn bobbin runs out of yarn, no cut can be made. Accordingly, the discriminator 4 is adjusted to a low sensitivity level. However, if a new yarn bobbin contains a double thread immediately at the beginning, the double thread is not detected on account of the inadequate sensitivity level. This disadvantage can be obviated by controlling the store 6 only by the discriminator 3, i.e. by lowering the sensitivity of the' discriminator 4 after the discriminator 3 has been triggered by a slub. A signal can now be received, as is known per se by the measuring head 2 incorporating an amplifier, indicating whether a yarn 1 is passing through. This signal erases the signal retained in the store.

As far as the textile industry is concerned, the following properties are obtained by the latter arrangement described. If a yarn is cut due to the presence of a slub, the sensitivity level is low upon replacement of the yarn so that hardly any needless cuts are made. As mentioned, the probability of a slub and a double thread occurring simultaneously is very small so that the reduction in sensitivity is quite permissible. When the thread passes through the yarn cleaner again, the store is erased. If a cut is made due to the presence of a double thread, or if a new yarn bobbin has to be inse1ted, the sensitivity of the discriminator 4 is relatively high and the probability of double threads not being detected correspondingly small. Naturally, a certain percentage of needless cuts must be expected although, as explained, this is permissible.

The circuit arrangement shown in FIG. 7 is a very detailed example of a circuit. The circuit has only to be amplified or supplemented in such a way that the signal indicating the passage of a thread which can be obtained in known manner from the A.C. voltage signal of the thread passing through, makes the transistor 54 conductive or blocks the transistor 52. This can be done by a positive impulse at the base of the transistor 54 or by a negative impulse at the base of the transistor 52, depending upon the polarity of the aforementioned signal. Instead of being erased by the signal released by the thread passing through, the signal contained in the store 6 may even be erased by the impulse generated upon insertion of the yarn. It could also be erased after a certain time interval particularly in cases where, following a cut, the yarn travels normally again within a predetermined time, for example, in the case of automatic winding machines.

Having thus described the invention it is not intended that it be so limited as changes may be made therein without departing from the scope of the invention. Accordingly, it is intended that the subject matter described above and shown in the drawings be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In combination with a yarn cleaner having a measuring head for passage of a yarn therethrough, a first discriminator for detecting the presence of a slub in the yarn in said head and emitting a signal in response thereto, a second discriminator havin an adjustable sensitivity for detecting the presence of a double thread in the yarn in said head and emitting a signal in response thereto, and a cutting device for receiving a signal from one of said discriminators to cut the thread; a store operatively connected to said first and second discriminators for receiving said signals therefrom, said store including a circuit arrangement responsive to a signal from at least one of said discriminators for storing the signal received and a control element for adjusting the sensitivity of said second discriminator in response to the signal stored in said circuit arrangement.

2. The combination as set forth in claim 1 wherein said discriminators are each Sch-mitt triggers.

3. The combination as set forth in claim 1 wherein said discriminators and said store have a common output.

4. The combination as set forth in claim 1 wherein said store is a bistable multivibrator.

5. The combination as set forth in claim 4 wherein said bistable multivibrator includes means for erasing the stored signal to flip said bistable multivibrator back to an initial position.

6. The combination as set forth in claim 5 wherein said means is actuated after a predetermined period of time after storing of the stored signal.

7. The combination as set forth in claim 5 wherein said means is actuated upon emission of a predetermined "signal from said first discriminator.

8. The combination as set forth in claim 5 wherein said means is actuated upon emission of an A0. voltage signal from said measuring head in response to re-insertion of the yarn.

9. A method for reducing the number of needless cuts in an electronic yarn cleaner having an adjustable sensitivity to emit signals in response to the presence of slubs and double threads of predetermined size in a yarn passing therethrough comprising the steps of receiving a signal in response to the presence of a slub or double thread of predetermined size, storing said received signal, and

adjusting the sensitivity of the yarn cleaner in response to said stored signal to emit signals in response to subsequent double threads of different size than the predetermined size.

10. A method as set forth in claim 9 wherein the sensitivity of the yarn cleaner is determined by a signal emitted on the presence of a slub.

11. A method as set forth in claim 9 wherein the sensitivity of the yarn cleaner is increased upon storing a signal responsive to a double thread.

12. A method as set forth in claim 9 wherein the sensitivity of the yarn cleaner is reduced upon storing a signal responsive to a slub.

13. A method as set forth in claim 9 which further includes the step of erasing the stored signal to return the sensitivity of the yarn cleaner to the initial sensitivity.

14. A method as set forth in claim 13 wherein said step of erasing occurs after a predetermined time period.

15. A method as set forth in claim 13 wherein said step of erasing occurs upon re-insertion of the yarn in the yarn cleaner.

16. A method as set forth in claim 13 wherein said step of erasing occurs upon emission of a subsequent signal corresponding to a slub.

17. A method as set forth in claim 13 wherein said step of erasing is actuated by an AC. voltage signal upon further passage of the yarn.

'18. A method as set forth in claim 13 wherein said step of erasing is actuated by an externally applied impulse.

References Cited UNITED STATES PATENTS 3,187,568 6/1965 Gonsalves et al. 73-160 3,258,824 7/1966 Gith 2864 3,309,754 3/1967 Metcalf 28-64 3,326,481 6/ 1967 -Frickert 242--36 LOUIS K. RIMRODT, Primary Examiner.

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