US3052826A

US3052826A - Control circuit for yarn clearing apparatus

Info

Publication number: US3052826A
Application number: US777632A
Authority: US
Inventors: Henri W Schneider; Albert C Leenhouts
Original assignee: J F Scholten And Zonen N V
Current assignee: J F Scholten And Zonen N V; J F SCHOLTEN AND ZONEN NV
Priority date: 1958-12-02
Filing date: 1958-12-02
Publication date: 1962-09-04
Anticipated expiration: 1979-09-04

Description

Sept. 4, 1962 H. w. SCHNEIDER ETAL 3,052,826

CONTROL CIRCUIT FOR YARN CLEARING APPARATUS Filed Dec. 2. 1958 2 Sheets-Sheet 1 INVENTORS Hana W- scnuzmzmand,

A E T C. Lasunours ATTORNEYS i B BY Se t. 4, 1962 H. w. SCHNEIDER ET AL 3,052,326

CONTROL CIRCUIT FOR YARN CLEARING APPARATUS Filed Dec. 2, 1958 2 Sheets-Sheet 2 Mama W- Summsz and.

ALBERT C. LEENHOUTS,

INVENTORQ- BY 01171), than, MAM M131 ATTORNEYS 3,952,326 CUNTROL CIRCUIT FOR YARN CLEARING APPARATUS Henri W. Schneider and Albert C. Leenhouts, Enschede,

Netherlands, assignors to J. F. Scholten and Zonen,

N.V., Willenstad, Curacao, a corporation of Curacao,

Netherlands Antilles Filed Dec. 2, 1953, Ser. No. 777,632 Claims. (Cl. 317-14?) This invention relates to apparatus for processing textile material such as yarn and the like and more particularly to electrically operated apparatus for detecting and providing for the elimination of yarn portions representing undesirable extreme deviations in the mass of the yarn.

In the manufacture of textile material such as yarn and the like, it is frequently desirable for the sake of yarn quality to remove certain yarn portions, the thickness or mass of which deviates to an excessive and undesirable extent from the mean or average mass deviations of the yarn. For instance, yarn portions which are considerably thicker are of greater mass than the average thickness or mass of the yarn and which are relatively short in length are generally undesirable and are commonly referred to in the textile industry as slubs. These slubs, as is well known, are caused by such factors as the incorporation of lint, fly, and similar unspinnable fibers in the yarn, broken filaments, or improper drafting of the yarn as it is processed. As is well known, these slubs weaken and reduce the quality of the yarn and therefore must be eliminated when yarn of high quality is desired.

Many devices are available commercially for removing or cleaning these slubs from yarn and are frequently referred to as slub catchers. These slub catchers may be broadly classified into two categories, namely the mechanical type and the electrical type and it is to the electrically operated type of slub catcher that this invention is directed. A slub catcher to which this invention is particularly applicable and of which this invention represents an improvement in the slub catcher shown in the copending patent application of Hendrick Van Lingen et 211., Serial No. 770,482, entitled Apparatus for the EX- amination of Textile Threads, filed October 29, 1958, and now abandoned. As discussed in this patent application, the slub catcher, which is preferably mounted on a winder, is of the type which is provided with a measuring capacitor having spaced plates through which the yarn being wound is advanced at a relatively high speed. The variations in the thickness or mass of the yarn being wound are converted into an electrical signal or representation and if an extreme mass deviation such as that produced by a slub generates a signal which exceeds a predetermined level or magnitude, the slub catcher is operated so as to perform a control function such as severing the yarn. The winder operator then cuts out the slub and reties the yarn permitting the yarn to continue its advance through the slu-b catcher. As can be understood in such yarn clearing apparatus, the slub catcher is adjusted so as to operate only when too large a deviation from the average mass of the yarn is encountered as too large a deviation would affect the quality of the fabric formed from the yarn.

Accordingly, as discussed in the above patent application, the sensitivity of the slub catcher is adjustable so that the extreme mass deviation in yarn at which the slub catcher will be actuated and perform its control function may be readily predetermined. Therefore, not only must the sensitivity of the slub catcher be changed to predetermine the minimum slub mass required to actuate the slub catcher, but as the count or size of the yarn 3,052,826 Patented Sept. 4, 1962 being cleared is changed, the sensitivity of the slub catcher must be changed correspondingly. This sensitivity adjustment is a precise undertaking and should be performed only by those persons thoroughly trained and skilled in this type of operation. Furthermore, even if satisfactory skilled labor is obtained for performing this precise adjustment, the substantial number of slub catchers employed in the usual textile mill means that considerable time and labor is involved in making these adjustments each time the size of the yarn to be cleared is changed.

Another difiiculty which arises with the use of the elect-rically operated type of slub catcher is the tendency of the slub catcher to perform the control function or, in other words, to cut the yarn as the yarn is being inserted within the plates of the measuring capacitor, particularly in the case where the slub catcher has been set for extreme sensitivity. This inadvertent slub catcher actuation is a result of the substantial yarn mass change when the yarn is inserted within the capacitor plates, and often the sensitivity of the slub catcher must be temporarily changed from the sensitivity setting at which the slub catcher is to normally operate in order to permit the insertion of the yarn within the plates. Here again, a skilled operator is preferably employed to make this sensitivity change and even with a skilled operator, the sensitivity may not be returned to its original setting as a result of human error and the like.

In another respect, electronic devices such as the electrically operated slub catcher discussed in the above-mentioned patent application contain components which are very sensitive and their settings and values are extremely critical so that it is quite difficult if not impossible to continuously operate such devices without the presence of some variations, however slight, which affect the accuracy of their performance.

For instance, as is well known, power source voltages frequently fluctuate, which change is in turn passed along to the circuits connected thereto. As voltage and current values are critical in many of such circuit components, the performance of electronic circuits will correspondingly vary with these power source variations. Other factors have been found to have influence on the performance of these slub catcher electronic circuits one in particular being temperature conditions and as these temperature conditions vary from time to time the performance of the circuit components will vary correspondingly. Furthermore, it is not uncommon for circuit components such as vacuum tubes and the like to become Weak through use and thus change their operating characteristics over a period of time producing changes in the operating characteristics of the circuit.

Accordingly, a primary object of the invention is to provide -a new and novel control circuit for yarn clearing apparatus.

Another object of the invention is to provide a new and novel control circuit for yarn clearing apparatus which is self-adjusting for uniform clearing action on yarn of any size over a wide range.

Still another object of the invention is to provide a new and novel slub catcher control circuit which automatically compensates for a change in the size of the yarn being cleared to eliminate any need for adjustment of the circuit after the desired slub clearing sensitivity has once been established.

A further object of the invention is to provide a new and novel method of uniformly clearing extreme mass deviations fom yarn over a wide range of yarn sizes.

A still further object of the invention is to provide a new and novel control circuit for slub catchers of the electrically operated type which produces an electrical signal corresponding to yarn mass variations, which automatically compensates for signal variations caused by such uncontrollable factors as line voltage variations, temperature fluctuations, and the like, and in which the slub catching action depends on the performance of passive elements such as resistors, capacitors and the like so as to be independent of any spontaneous changes in the amplification of the signal.

This invention further contemplates the provision of a new and novel control circuit for an electrically operated yarn clearing apparatus which continuously produces a comparison between the extreme mass yarn deviation and the mean or average mass or thickness deviation of yarn being examined so as to permit actuation of the slub catcher upon the presence of a signal value which represents an undesirable extreme mass deviation and permits yarn of various sizes over a wide range to be cleared of undesirable extreme mass deviations without the need of adjustment when changing the size of yarn to be cleared.

Still another object of the invention is to provide a new and novel control circuit for an electrically operated yarn clearing apparatus in which a suitable alarm or signal device is actuated when the yarn is not being examined and which prevents actuation of the yarn clearing action when the yarn is initially placed into the examining position within the yarn clearing apparatus.

A further object of the invention is to provide a new and improved slub catcher control circuit which is automatic in operation after an initial sensitivity setting and at the same time utilizes a minimum of parts, is capable of operating over long periods of time without breakdown and is characterized by extremely accurate yarn examining action.

Briefly, the objects of the invention and other related objects are accomplished by providing means for producing an electrical signal which signal varies in response to the variation in the mass or thickness in yarn being examined by yarn clearing apparatus. This variable or fluctuating signal which is preferably amplified is conducted after amplification through first and second paths, the first of which conducts the signal directly to relay means arranged to perform a control function. The second path for the signal includes means for converting this fluctuating signal to a steady-state or non-variable signal which reflects the average or mean variations in mass or thickness of the yarn. As is well known, the larger the size of the yarn, the greater the average mass deviations and consequently the greater the value of this steady-state signal. This steady-state signal is also conducted to the relay means which is so arranged that the steady-state signal inoperatively conditions the relay means and the steady-state signal is reduced proportionally with an increase in the value of the fluctuating signal. If the variable signal reaches a predetermined extreme value, this extreme value corresponding to the absolute value of the mass variation produced by a yarn mass or slub of objectionable size, to sufiiciently reduce or eliminate the steady-state signal, the relay means is operatively conditioned and performs the control function. In addition, means are provided in the circuit for preventing the operation of the relay means by the variable signal in the absence of the steady-state signal or when the steady-state signal produced in the second path does not exceed a predetermined minimum value. Furthermore, an alarm device such as a lamp or the like may also be incorporated into the circuit so as to indicate the absence or the predetermined low value of this steady-state signal in the second path.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which:

FIGURE 1 is a wiring diagram of a control circuit for yarn clearing apparatus in accordance with the invention;

FIGURE 2 is a modification of the control circuit of FIGURE 1; and

FIGURE 3 is a second modification of the control circuit of FIGURE 1.

Referring now to FIGURE 1, there is shown a wiring diagram illustrating one embodiment of the novel control circuit of the invention. As has been previously discussed, this control circuit is preferably incorporated in yarn clearing or slub catching apparatus such as that apparatus described and claimed in the Van Lingen et al. application referred to above. The control circuit of the invention is arranged to receive a continuous electrical signal which fluctuates or varies in accordance with mass variations in the yarn being examined as the yarn is advanced at a relatively high speed.

Any conventional evice may be utilized with the control circuit of FIGURE 1 for sensing the yarn mass variations such as devices which operate pneumatically, photoelectrically or by capacitive means. As described in the Van Lingen et al. application, the yarn to be cleared passes between the spaced plates of a measuring capacitor which produces an electrical signal that varies in accordance with the variations in the mass of the advancing yarn.

For the purpose of clarity, the mass change measuring device incorporated with the circuit of FIGURE 1 for generating this fluctuating or variable signal has not been shown and it should be understood that the means described in the Van Lingen et al. application represent one convenient arrangement for producing an electrical signal which is a reflection or an electrical representation of the mass changes in the advancing yarn.

In the arrangement of the circuit of FIGURE 1, the variable or fluctuating signal produced is coupled by means of a capacitor 11 to the control electrode or grid 12 of a triode 13 which contains a cathode 14 and an anode or plate 16. A grid leak resistor 17 is connected to the grid 12 and is connected to ground by means of a ground conductor 18. The triode 13, which is arranged to function as an amplifier, has its plate 16 connected by means of conductor 19 to a source of positive DC voltage B+ through

resistors

29, 21. A movable tap 22 is associated with the resistor 26 and is connected to a conductor 23 which constitutes a first path for the signal generated by the mass variations in the advancing yarn and amplified in the triode 13. In the embodiment illustrated, the amplified signal, although fluctuating in nature, has a positive value. Conductor 23 is connected through coupling capacitor 24, resistor 25, coupling capacitor 26 and resistor 27 to relay means designated generally by the numeral 28.

In the specific embodiment illustrated, the relay means 28 comprise a thyratron 29 and a coil 31 having associated therewith a core 32 arranged to perform a control function such as the actuation of a yarn cutting device in the manner described in the above refer-red to Van Lingen et al. patent application. The resistor 27 is therefore connected to the control electrode or grid 33 of the thyratron 29 which also contains a cathode 34 and a plate 37 connected by means of conductor 38 to one side of the coil 31. The other side of the coil 31 is connected to a suitable source of positive voltage B+.

A fixed negative bias voltage B- is fed to the grid 33 of the thyratron 29 through a resistor 39 connected to the junction of resistor 27 and capacitor 26. The value of the B- voltage is selected in accordance with the characteristics of thyratron 29 and the circuit performance desired as will be explained hereinafter.

A second path is provided for the amplified signal appearing in the triode plate conductor 19 which comprises a conductor 41 connected to conductor 19 between the triode plate 16 and the variable resistor 26 as shown in FIGURE 1. Means have been provided in the circuit of FIGURE 1 for converting or rectifying the amplified variable signal appearing at the output of triode 13 to a steady state or non-variable signal referred to herein after as the automatic bias voltage. More specifically, conductor 41 is connected by means of capacitor 42 to a voltage doubling circuit comprising a pair of diodes 43, 44- and a capacitor 47. The output of this voltage doubler appears across a load resistor 48. As shown, the voltage doubling circuit is grounded by connecting the junction of the cathode of diode 44, capacitor 47, and resistor 43 to the ground conductor 18.

The rectified output or automatic bias voltage of the voltage doubling circuit appearing at the junction of resistor 48 and the plate of diode 43 has a negative value and is fed by means of resistor 49, resistor 51 and resistor 27 to the thyratron grid 33. A capacitor 52, one side of which is grounded by conductor 13, is connected in the well known manner to the junction of the

resistors

49, 51 in order to smooth out the ripple in the rectified signal produced by the voltage doubling circuit. It should be understood that the

resistors

49, 51, 39 therefore form a voltage dividing system so that only approximately 80- 90% of the full automatic bias voltage appears on the thyratron grid 33.

The automatic bias voltage appearing on the junction of the plate of diode 43 and

resistors

48, 49 is conducted by means of a resistor 53 to the junction of resistor and the coupling capacitor 26 to which junction is also connected to the plate of a clipper diode 54, the cathode of which is suitably grounded. If a vacuum type clipper diode 54 is employed rather than a crystal diode or semiconductor diode, the resistor 25 must be used for good clipping in order to provide a voltage divider comprising the resistor 25 and the internal resistance of the vacuum clipper diode.

In many cases it is desirable that some signaling or indicating means be provided for readily indicating that the yarn has been removed from the measuring condenser or that no signal is being produced. Therefore, means have been provided in the circuit of FIGURE 1 for indicating the absence of the automatic bias voltage which preferably comprise a triode 58 having grid 59 connected to the junction of

resistors

49, 51 and capacitor 52. The cathode of the triode 58 is grounded and its plate is connected through a gas-filled signal light or other suitable alarm device 61 to a source of positive voltage 13+,

In the operation of a yarn clearing device or slub catcher utilizing the circuit of FIGURE 1, the suitably generated, fluctuating signal voltage which is coupled to the grid 12 of the triode 13 by means of the capacitor 11 is amplified in the triode and is conducted through the first path comprising conductor 23, capacitor 24, resistor 25, capacitor 26, resistor 27 to the thyratron grid 33. As has been explained, this positive amplified signal voltage fluctuates or varies in accordance with the mass variations in yarn advancing through a yarn examining device such as the spaced plates of a measuring capacitor and is continuously fed to the thyratron grid 33. In addition, the amplitude of this signal may be adjusted by means of the tap 22 associated with resistor 20 which provides a means for predetermining the minimum size of the yarn mass variation which is necessary for actuation of the relay means 28.

The thyratron 29 may be of either the positive grid or negative grid type but in the preferred embodiment, the thyratron is preferably of the negative grid type and is arranged to ignite or conduct when the negative bias on grid 33 is less than approximately two volts. The thyratron 29 is therefore biased slightly more than two volts negative by means of the fixed bias voltage B- applied through resistor 39 so that the thyratron 29 does not conduct in the absence of an automatic bias voltage.

During normal operation, as the variable signal is conducted through its first path, it is simultaneously conducted through its second path by the conductor 41 and is rectified by means of the

diodes

43, 44 together with the associated components to provide an automatic bias voltage having a negative value which is fed to the thyratron grid 33 through

resistors

49, 51 and 27. As is well known in voltage doubling circuits of the type illustrated, the amplitude of the output signal is further increased after rectification. Therefore, in addition to the fixed bias voltage B-, an automatic bias voltage, which is a reflection of the average or mean mass variations in the advancing yarn, is applied to the thyratron grid 33 to further bias the grid negatively. As has been explained, the original automatic bias voltage has been reduced slightly (10- 20%) prior to reaching the grid 33.

When the signal voltage fed through conductor 23 to the grid 33 reaches a magnitude, which of course may be regulated by the variable resistor 20, sufiicient to overcome the automatic bias voltage, the thyratron 29 will conduct and energize the relay coil 31 to perform the control function.

As is well known, the average value of the mass variations in yarn increases with increasing yarn size. As a result of the automatic bias voltage produced in the circuit, this change in average mass variations, which occurs when the size of the yarn being examined is changed, is automatically evaluated by the circuit so that the circuit is self-adjusting. In other words, when the size of the examined yarn is increased, the average yarn mass variation and consequently the automatic bias voltage increases requiring a greater extreme mass variation to fire thyratron 29 for the same tap setting on resistor 20. For any size yarn, therefore, the ratio of the extreme mass deviations required to actuate the relay to the average value of these mass variations is approximately the same for the same setting on resistor 20.

VVhen the relay 28 has performed the control function such as cutting of the yarn and the machine operator has eliminated the slu-b and retied the yarn, the absence of the automatic bias voltage can cause ignition of the thyratron by a very weak positive pulse or signal. Such a signal might be produced during the reinsertion of the yarn within the plates of the measuring capacitor. Therefore, it is highly desirable that the thyratron 29 be prevented from firing when the yarn is being inserted within the yarn examining device.

As is well known, the diode 54 will only conduct when the voltage on its plate becomes positive and therefore as long as the negative automatic bias voltage is fed to the junction of the diode plate, the resistor 25, and the capacitor 26, the signal in conductor 23 would have to exceed this automatic bias voltage before the diode 54 would conduct. This would not be possible in the circuit of FIGURE 1, as the thyratron 29 would ignite before the automatic bias voltage is exceeded by the signal on the plate of diode 54-, since the automatic bias voltage on grid 33 is lower than the full automatic bias voltage as explained above.

When there is no yarn in the yarn examining or measuring device and consequently zero automatic bias voltage at the junction, the positive signal. fed to the thyratron grid 33 cannot rise above zero as any positive signal voltage will immediately cause the diode 54 to conduct. Therefore, if a positive impulse appears in conductor 23 as a result of the insertion of the yarn in the measuring capacitor, diode 54 will conduct and no signal can get to the thyratron grid 33 to cause ignition.

It should be understood that in FIGURE 1 there have been shown

diodes

43, 44, 54 and triode 13 of the vacuum type as they can be all included in the same envelope of a commercially available tube. However, diodes of the crystal, semi-conductor, and other types may be employed if desired.

In addition, it is highly desirable that suitable means be provided to indicate that no yarn is present in the yarn clearing apparatus or that the yarn is no longer advancing to indicate to the operator or the supervisor that the slub catcher is not operating. Means therefore have been provided with this invention for signaling the absence of the automatic bias voltage which of course reflects the absence of advancing yarn.

More specifically, as shown in FIGURE 1, the grid 59 of the triode 58 is connected to the junction of the

resistors

49, 51 and capacitor 52 so as to receive the automatic bias voltage. In the absence of this automatic bias voltage, such as when there is no yarn in the slub catcher or when the slub catcher has cut the yarn and yarn no longer advances, there is no bias voltage on the triode grid 59 and the triode conducts causing a current flow through the gas-filled signal light 61. The light 61 therefore glows to indicate the absence of the automatic bias voltage. It should be understood that any suitable type of signaling device may be used such as an alarm or the like instead of the signal light 61.

If it is desired to only detect slubs above a certain length independent of mass, an RC filter may be located between the diode 54 and the capacitor 26 to provide a time delay. Thus if the slub is so short that the signal produced by a momentary extreme mass deviation falls to zero before a predetermined time period has elapsed, the thyratron 29 will not ignite.

As previously discussed, during normal operation, the mass variations in the advancing yarn produce a signal from which an automatic bias voltage is obtained which is fed to the grid 33 of the thyratron 29 and this negative bias voltage must be overcome by a positive signal having a magnitude representing an undesirable extreme mass deviation in the yarn which is to be removed. In many cases, it is not only desirable to prevent actuation of the slub catcher in the absence of yarn in the measuring condenser or a termination of the yarn advance but also when the automatic bias voltage becomes relatively Weak or drops below a predetermined critical value permitting a relatively weak positive impulse or signal to ignite the thyratron.

In the circuits of FIGURES 2 and 3, there are shown modifications of the embodiment of FIGURE 1 which include means for preventing ignition of the thyratron when the automatic bias voltage falls below a certain value or is totally absent. It should be understood that in FIG- URES 2 and 3 like numerals have been employed to identify like parts.

Referring now to FIGURE 2, diode '54,

resistors

25, 39, 53 and capacitor 26 included in FIGURE 1 have been eliminated and the variable signal conducted through the first path by conductor 23 is not clipped. The variable positive signal in conductor 23 is fed through capacitor 24 and resistor 27 to the grid 33 of thyratron 29. Furthermore, in the circuit of FiGURE 2, the fixed B- bias voltage is brought in through a conductor 65 connected to the junction of capacitor 47 and resistor 48. An A.C. path to ground for the voltage doubling circuit is provided by a capacitor 67 having one side connected to the junction of the capacitor 47 and resistor 48 and grounded on the other side by means of ground conductor 13.

A conductor 68 is connected to the junction of

resistors

49, 51 and capacitor 52 so that the automatic bias voltage is fed continuously to the grid 69 of a triode 71 having a grounded cathode 72 and a plate '73. The characteristics of the triode 71 are selected so that if the automatic bias voltage exceeds a predetermined minimum value the triode does not conduct. Therefore, if the automatic bias voltage falls below this minimum value or is completely eliminated, the triode 71 will conduct.

The plate 73 of triode 71 is connected by means of conductor 74 through serially connected

resistors

76, 77 to a source of positive voltage B+. A signal light 78 is connected in parallel with resistor 77.

A voltage divider circuit comprising serially connected resistances 79, 81 is connected at one end to conductor 74 between resistor 76 and triode plate 73 and at the other end to a negative voltage source B. A tap comprising a conductor 82 is connected at a point between the resistor 79 and resistor 81 and leads electrically to a control electrode 83 in the thyratron 29. A clipping diode 84- and a time delay capacitor 86, connected in electrical parallel relationship, are connected at one common side to tap conductor 82 between resistor 79 and the control electrode 83 and at their other side to the ground conductor 18.

In the absence of an automatic bias voltage on the triode grid 69 or if the voltage falls below a critical value, the triode 71 conducts and a large current flows through

resistors

76, 77. The voltage drop acros resistor 77 will energize signal light 78 to indicate very little or no bias voltage is present. The high current in conductor 74 produces a low plate voltage on triode 71 as a result of the voltage drop in resistors 76-, 7'7 and the tap 82 between the voltage dividing resistors 79, 81 will therefore produce an even lower negative voltage on the control electrode 83 of thyratron 2,9 preventing its ignition.

Thus, in the absence of an automatic bias voltage or when the automatic bias voltage becomes too low, ignition of the thyratron cannot take place. When the automatic bias voltage has been built up again under normal yarn examining conditions, the bias voltage on grid 69 cuts off triode 71 and there is no current flow through conductor 74. The voltage on the thyratron electrode 83 therefore tends to go positive but cannot, as any positive voltage on conductor 82 results in a current flow through diode 84, and prevents the buildup of any positive voltage on the electrode 83 which would prevent actuation of the thyratron 29 under normal operating conditions. The capacitor 86 in parallel with the diode 84 supplies a small time delay.

Referring now to FIGURE 3, a second modification of the control circuit or" FIGURE 1 is shown and as in FIGURE 2 like numerals are used to identify like parts. Instead of the triode 71 of FIGURE 2, a gas-filled tube 91 is employed in which the grid voltage for firing the tube is more sharply defined. The tube '91 contains a grid 92 connected by means of conductor 93 to the junction of

resistors

49, 51 and capacitor 52 for conducting the generated automatic bias voltage to the grid.

The electron tube 91 has a cathode 94 grounded by means of conductor 96 to the ground conductor 18. The plate 97 of tube 91 is connected by means of

resistors

98, 99 to two voltage sources, one a positive D.C. voltage 13+, preferably twenty-five volts, and the other a relatively high A.C. voltage of normal line frequency which is preferably approximately 250 volts. A signal light 101 of the type discussed above is preferably connected in parallel with resistor 98.

In order to obtain the above described ignition blocking action in thyratron 29, a pair of serially connected resistor-s ill-2, 193 are connected at one end to the junction of resistor 98 and the plate '97 of tube 91 and at their other end to the thyratron control electrode 83. The diode 84 is connected at one side to the junction of resistor 103 and control electrode 83 in parallel with capacitor 86 which is connected at its corresponding side to the junction of resistors 102, 103. As in the embodiment of FIGURE 2, capacitor 86 and diode 84- are grounded by means of the ground conductor 18.

Under normal operating conditions during yarn examination, the automatic bias voltage cuts off the gas-filled tube 91 and the voltage on the plate of tube 91 will be approximately twenty-five volts as determined by the B+ voltage. This voltage would also appear on the thyratron control electrode 83 but the diode 84 conducts when the voltage on electrode 83 tends to go positive so that when the automatic bias voltage is present, the voltage on the electrode 83 remains Zero. The AC. voltage fed into the circuit through resistor 99 is at this time filtered out by a simple ripple filter arrangement utilizing the capacitor 86.

In the absence of the automatic bias voltage, the gasfilled tube 91 conducts and rectifies the AC. voltage so that negative impulses only are produced in a manner of a half-wave rectifier and these negative pulses are smoothed out by the capacitor 86. This smoothed out, rectified negative voltage exceeds the 13+ voltage and the control electrode 83 goes negative preventing ignition of the thyratron 29. During this action, the signal light 101 is energized and glows to indicate that the automatic bias voltage is too low or is totally absent. As in the control circuit of FIGURE 2, capacitor 86 provides a time delay of a small amount in addition to smoothing out the negative pulses produced during the half cycle when tube 91 conducts.

It can be seen therefore that there has been provided with this invention a new and novel control circuit for yarn clearing apparatus which eliminates many manual operations previously required and permits the operation of yarn clearing apparatus with a greater degree of accuracy than heretofore possible and with a minimum amount of time. One of the outstanding features of this invention is the feature of the slub catching apparatus which permits it to automatically adjust to any size yarn which is to be cleared or cleaned of slubs. Once a sensitivity setting has been made on the slub catcher for the minimum extrem mass deviation which the slub catcher is to pass, no further adjustment is required and the slub catcher will automatically examine various yarn sizes over a wide range with the same relative sensitivity without the need for additional adjustment. Furthermore, this slub catching action or sensitivity is completely independent of the amplification of the generated signal so that temperature fluctuations, changes in line voltage, and similar unpredictable factors which affect the amplification of the signal no longer affect the detecting or examining action of the slub catcher, as this examining action now depends only on such passive elements as resistors, condensers and the like. Furthermore the novel arrangement of the circuit permits the use of the very simple and quite inexpensive A.C. amplification techniques rather than D.C. amplification common to presently employed yarn irregularity detection instruments. Although the control circuits of the invention have been described in combination with a slub catcher which provides for severing the yarn when a slub appears to permit removal of the slub by an operator, the circuits may be similarly employed to actuate a counter or the like in order to totalize the number of yarn faults or slubs without cutting or stopping the movement of the advancing yarn. In this manner, yarn quality control may be practiced with a high degree of accuracy.

Another outstanding feature of the invention is the method of yarn examination which can be practiced with the novel circuit of the invention. As discussed above, this novel method involves comparing the mean or average mass deviations in yarn with the absolute or total mass deviation so that a ratio is obtained which is maintained substantially uniform throughout changes in the size of the yarn being examined. As is well known, this method takes advantage of the inherent increase in average yarn mass deviations as the yarn size is increased.

Another feature of the invention is the automatic signaling device which indicates that the yarn has been removed from the yarn examining device incorporated in the yarn clearing apparatus so that not only are the operators immediately notified when the yarn is cut but any attempt to remove the yarn from the yarn examining device and thus increase the output without improving the quality of the yarn by an operator may be immediately detected.

In the drawings and specification there has been set forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not (for purposes of limitation, the scope of the invention being defined in the claims.

We claim:

1. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, means for producing from said variable electrical signal a steady-state electrical signal corresponding to the average value of the variations in the mass of said yarn, relay means for performing a control function, means for conducting said variable signal and said steady-state signal to said relay means for oppositely conditioning said relay means whereby a predetermined amplitude of said variable signal corresponding to an excess variation in the mass of said yarn operatively conditions said relay means to perform said control function.

2. A control circuit for yarn clear-ing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, means for producing a steady-state electrical signal from said variable signal corresponding to the average variations in the mass of said yarn, relay means for performing a control function, means for conducting both said variable signal and said steady-state signal to said relay means whereby said steadystate signal inoperatively conditions said relay means and the value of said steady-state signal is reduced proportionally with the amplitude of said variable signal, said relay means being arranged to operatively respond and perform said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said yarn.

3. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, relay means for performing a control function, means for simultaneously conducting said variable signal through a pair of paths connected to said relay means, means in one of said paths for converting said variable signal to a steady-state electrical signal corresponding to the average value of the variations in the mass of said yarn and which inoperativeiy conditions said relay means, said variable signal in the other path being arranged to reduce the value of said steady-state signal in proportion to the amplitude of said variable signal whereby said relay means operatively responds and performs said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said yarn.

4. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, relay means for performing a control function, a first path for conducting said variable signal to said relay means, a second path for said variable signal including means for converting said variable signal to a steady-state electrical signal corresponding to the average value of said variations in the mass of said varn, said second path being arranged to conduct said steady-state signal to said relay means for inoperatively conditioning said relay means, said variable signal being arranged to reduce the value of said steadystate signal in proportion to the amplitude of said variable signal whereby said relay means operatively responds :and performs said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said yarn.

5. A control circuit for yarn clearing apparatus in accordance with claim 4 including means for indicating the drop of said steady-state signal said second path to 'a predetermined level.

6. A control circuit for yarn clearing apparatus in ac-- cordance with claim 4 including means for preventing the actuation of said relay means when the steadystalte signal in said second path drops to a predetermined level.

7. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, means for amplifying said variable signal, relay means for performing a control function, a first path for conducting said amplified variable signal to said relay means, a second path for said amplified variable signal including means for converting said amplified variable signal to a steady-state electrical signal corresponding to the average value of the variations in the mass of said yarn, said second path being arranged to conduct said steady-state signal to said relay means for inoperatively conditioning said relay means, said amplified signal being arranged to reduce the value of said steady-state signal in proportion to the amplitude of said amplified variable signal whereby said relay means operatively responds and performs said control function at a predetermined reduction of said steady-state signal by an amplified variable signal corresponding to an excessive variation in the mass of said yarn.

8. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously produc ing a variable electrical signal corresponding to the variations in the mass of advancing yarn, a source of power, relay means for performing a control function, said relay means including an electron tube, said electron tube having at least three electrodes including a control electrode, a first path for conducting said variable signal to said control electrode, a second path for said variable signal including mean-s for rectifying said variable signal to a steady-state electrical signal of opposite polarity from said variable signal corresponding to the average value of said variations in the mass of said yarn, said second path being arranged to conduct said steady-state signal to said control electrode for biasing said electron tube to a nonconduotive condition, said variable signal being arranged to reduce the value of said steady-state signal in proportion to the amplitude of said variable signal whereby said electron tube conducts and actuates said relay means to perform said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said yarn.

9. A control circuit in accordance with claim 8 including a fixed DC. voltage source, means connecting said fixed DC. voltage source to said control electrode whereby said DC. voltage biases said electron tube into a non-conductive condition.

10. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal having a positive polarity corresponding to the variations in the mass of advancing varn, relay means for performing a control function, a first path for conducting said variable signal to said relay means, a second path for said variable signal including means for rectifying said variable signal to a negative DC signal having a value corresponding to the average value :of said variations in the mass of said yarn, said second path arranged to conduct said DC. signal to said relay means in opposition to said positive variable signal and maintain said relay means in an inoperative condition whereby a variable signal of predetermined positive amplitude couresponding to an excessive variation in the mass of said yarn sufficient to reduce said DC. signal to a predetermined level operatively conditions said relay means to perform said control function.

11. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, relay means for performing a control function, a first path for conducting said variable signal to said relay means, a second path for said variable signal including means for converting said variable signal to a steady-state electrical signal corresponding to the average value of said variations in the mass of said yarn, said second path being arranged to conduct said steady-state signal to said relay means for inoperatively conditioning said relay means, said variable signal being arranged to reduce the value of said steadystate signal in proportion to the value of said variable 12 signal, means for clipping said variable signal in said first path in the absence of said steady-state signal, said relay means being arranged to operatively respond and perform said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said yarn.

12. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, first relay means for performing a control function, a first path for conducting said variable signal to said relay means, a second path for said variable signal including means for converting said variable signal to a steady-state electrical signal corresponding to the average value of said variations in the mass of said yarn, said second path being arranged to conduct said steady-state signal to said first relay means for inoperatively conditioning said relay means, said variable signal being arranged to reduce the value of said steady-state signal in proportion to the amplitude of said variable signal, said first relay means being arranged to operatively respond and perform said control function at a predetermined reduction of said steady-state signal by a variable signal corresponding to an excessive variation in the mass of said varn, second relay means operatively associated with said first relay means, a third path for conducting said steady-state electrical signal to said second relay means for inoperatively conditioning signal exceeds a predetermined minimum level, said second relay means being arranged to operatively respond when said steady-state signal falls below said predetermined level and prevents actuation of said first relay means.

13. A control circuit in accordance with claim 12 wherein said second relay means comprises a triode, said triode being arranged to conduct when said steady-state signal falls below said predetermined level and prevent actuation of said first relay means.

14. A control circuit in accordance with claim 12 wherein said second relay means include a gas-filled electron tube, a source of AC. voltage connected to said gas-filled tube and to said first relay means, said gas-filled electron tube being arranged to conduct and rectify said AC. voltage when said steady-state signal falls below said predetermined level and provide a negative DC. voltage for preventing actuation of said first relay means.

15. A control circuit for yarn clearing apparatus comprising, in combination, means for continuously producing a variable electrical signal corresponding to the variations in the mass of advancing yarn, means for amplifying said variable signal, said amplified variable signal having a positive polarity, means for adjusting the signal gain in said amplifying means, a source of power, relay means for performing a control function, said relay means including a thyratron for connecting said relay means to said source of power, said thyratron having at least three electrodes including a control electrode, a source of negative DC. bias voltage, means for conducting said negative DC. bias voltage to said control electrode for biasing said thyratron into a non-conductive condition, a first path for conducting said amplified variable signal to said thyratron control electrode, a second path for said amplified variable signal including a voltage doubling circuit for rectifying said amplified variable signal to a DC. signal of negative polarity corresponding to the average value of the variations in the mass of said yarn, said second path being arranged to conduct said DC. signal to said thyratron control electrode for additionally biasing said thyra-tron into said non-conductive condition, said amplified variable positive signal being arranged to reduce the value of said DC. signal in proportion to the amplitude of said variable signal whereby said thyratron conducts and actuates said relay means to perform said control function When said DC. signal is overcome by a variable signal corresponding to an excessive variation in the mass of said yarn, means including an indicator light for indicating the drop of said DC. signal in said second path to a predetermined low level, an electron tube operatively associated with said thyratron, a third path for conducting said DC signal in said second path to said electron tube whereby said electron tube conducts and inoperatively conditions said thyratron when said DJC. signal in said second path falls below a predetermined minimum value.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Great Britain Apr. 10, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,052,826 September 4, 1962 Henri W. Schneider et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 23, after thicker" insert or column 2, line 68, for "fom" read from column 12, line 28, after "conditioning" insert said second relay means when said steady-state electrical"; line 32, for "prevents" read prevent Signed and sealed this 5th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer v Commissioner of Patents UNITED STATES PATENT OFFICE f CERTIFICATE OF CURRECTION Patent No, 3,O52 826 September 4, 1962 Henri W. Schneider et a1.

Column 1, line 23, after thicker insert or column 2 line 68, for "form" read from column 12, line 28, after "conditioning" insert said second relay means when said steady-state electrical"; line 32, for "prevents" read prevent Signed and sealed this 5th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer S Y Commissioner of Patents