US3677036A

US3677036A - Method of equalizing supply of thread to a plurality of knitting stations

Info

Publication number: US3677036A
Application number: US879711A
Authority: US
Inventors: Charles Hatay
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-11-25
Filing date: 1969-11-25
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18

Abstract

To provide equal supply of thread, a signal is generated representative of thread speed of each of the thread supplies, for example by wrapping thread around a disc subjected to pulsed illumination supplied from a pulse source. One knitting station is adjusted for perfect knitting, and the pulse source is then regulated so that the disc of that one station will appear stationary; thereafter, the other knitting stations are regulated, manually or by means of a servo motor, until they all appear stationary, that is until all the knitting stations are in synchronism. Additionally, thread tension is pre-set and sensed at each station, and the speed of a thread delivery drum controlled to provide constant thread tension to the knitting positions.

Description

United States Patent Hatay [54] METHOD OF EQUALIZING SUPPLY OF THREAD TO A PLURALITY OF KNITTING STATIONS [72] Inventor: Charles Hatay, Alpenweg 7, Busingen near Schaffhausen, Germany 22 Filed: Nov. 25, 1969 [2]] Appl. No.: 879,711

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 625,l l0, March 22,

1967, Pat. No. 3,523,433.

[52] U.S. Cl. ..66/132 R, 66/54, 66/125 R [51] Int. Cl. 15/48 [58] Field of Search ..66/12S, 54, 55, I32, 125 R, 66/132 R [56] References Cited UNITED STATES PATENTS 2,098,050 1 1/1937 Lawson et al ..66/l25 2,106,146 1/1938 Gosling ..66/125 2,109,945 3/1938 Lawson ..66/l25 2,207,464 7/1940 Lawson ..66/125 3,073,139 1/1963 Post et al. ..66/l32 [451 July 18, 1972 FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Robert R. Mackey Attorney-Flynn & Frishauf ABSTRACT To provide equal supply of thread, a signal is generated representative of thread speed of each of the thread supplies, for example by wrapping thread around a disc subjected to pulsed illumination supplied from a pulse source. One knitting station is adjusted for perfect knitting, and the pulse source is then regulated so that the disc of that one station will appear stationary; thereafier, the other knitting stations are regulated, manually or by means of a servo motor, until they all appear stationary, that is until all the knitting stations are in synchronism. Additionally, thread tension is pre-set and sensed at each station, and the speed of a thread delivery drum controlled to provide constant thread tension to the knitting positions.

5 Claims, 6 Drawlng Figures PATENTED JUL! 8 I972 SHEET 2 OF 5 PATENIEU JUL 1 a m;

sew 3 [1F 5 M, w 3 w METHOD OF EQUALIZING SUPPLY OF THREAD TO A PLURALITY F KNITTING STATIONS Continuation-impart of Ser. No. 625,1 I0, filed March 22, 1967, now U.S. Pat. No. 3,523,433.

This invention is a continuation-in-part of application Ser. No. 625,110, new U. S. Pat. No. 3,523,433, granted Aug. II, 1970 and relates to a method of equalizing supply of thread to thread feeding stations of knitting machines provided with a feeding drum controlled in relation to its circumferential speed, the outer surface of which feeds the thread resting on it by essentially slipless frictional drive. The drum is driven through an electromagnetic coupling by a source of energy rotating at a constant speed corresponding to the highest requirement of thread. The pull-off of the thread by the drum is controlled, automatically in dependence on the tension of the thread, for example by a thread feeler, to furnish an equal supply of thread to the individual working positions in circular knitting machines and particularly to machines having more than one feeding station.

Apart from thread feeding devices comprising two meshing cogwheels, which have the disadvantage that the thread is crinkled several times and that in order to alter the feeding speed relatively large masses have to be accelerated or delayed by the cogwheels, two basically different types of thread feeding devices are used, both provided with smooth surfaced feeding drums. In one, the thread resting on the surface is fed without slip, while in the other type the rate of feed is controlled by changing the slip of the thread on the outer surface of the feeding drum which rotates at a constant speed. The present invention relates to the first type.

It is the object of the invention to provide a method of thread feeding which permits the control of the feeding speed in dependence on the tension of the thread in a simple manner, and which makes it possible to synchronize the feeding elements of the individual stations of a circular knitting machine with each other. The rate of feed per station is controlled. This assures that, firstly, the rate of feed per station remains constant and that, secondly, any variations in the tension at the knitting positions, due to irregularities in the machine, are compensated, whereby it is assumed that the consumption of thread at each knitting position over a longer period remains constant.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, a signal is generated which has a characteristic representative of thread speed which will result in perfect knitting; this signal is used as a reference or command signal against which similar thread speed signals are compared having characteristics representative of thread speed to the other knitting positions; error signals are then brought to zero by adjusting the knock-over point at the various knitting positions, so that the knitting at all positions will be perfect and in synchronism and under the same conditions as that at the position from which the command signal was derived. Additionally, the tension of the thread being supplied to the knitting positions is sensed and the speed of the supply drum is controlled from the sensed tension, so that a certain predetermined tension of thread will be maintained at all times.

In accordance with a feature of the invention, stroboscopic discs and strobe-lamps supplied by a pulse source are used to generate the signals; the pulse source can also be used to control servo motors for automatic adjustment of the knock-over point and thus automatically control the knitting at all the knitting positions.

The construction of a device to carry out the method is simple and safe in operation, so that it can be easily fitted to existing machines. Moreover, it is possible to maintain the best possible stability in the tension of the thread, while during the feeding the tension of the thread can be kept constant down to a value of nearly zero gram tension. The electrical drive of the feeding drums in itself is known (see German Pat. Publication No. l 147 705). These known feeding drums are so con structed that the feeding element is formed by a cylinder which is the rotor of an electro motor. This type of feeding drum rotates, however, at a constant and unchangeable speed, while the rate of feed of the thread is altered by changing the tension of the thread, so that the mirror-like surface of the feeding drum around which the thread is wound pulls the thread with more or less force.

The method may be used for the supply of the thread to the individual knitting positions of a multi-station machine which can be adjusted to an absolutely constant and overall uniform value and can be maintained at this value or to a number of single-station machines operating in parallel.

Each knitting station is provided with a stroboscopic disc which can be illuminated by a stroboscopic lamp, which disc is driven by the thread extending between the thread bobbin and the thread feeding drum and the stroboscopic lamp, which lamp is fed by an electrical pulse emitter (pulse counter) which is common to all systems. According to the indication of the stroboscopic discs at the individual systems, the rate of feed is adjusted to equal values by altering the position of the stitch knocking-over parts, the tension of each thread, which is fed slipless by the electromagnetically driven feeding drum, the circumferential speed of which is adjustable, is scanned by means of adjustable thread tension feelers. The thread tension feelers are arranged behind the feeding drum and detect variations in the tension of the thread in the region between the relevant feeding drum and the knitting system. The tension sensors control electrical pulse emitters which adjust electrically the circumferential speed of the relevant feeding drum to a constant thread tension. The adjustable thread tension feelers of the individual systems may be set to the same thread tension, which would be the best in most cases. Control of the rate of feed to the individual systems and of thread tension directly controls the lengths of threads being supplied to the knitting positions. The stitch knocking-over parts can be adjusted by hand or automatically in dependence on the measuring result of the thread supply control device, such, that at a constant tension of the thread a constant thread consumption is achieved in all systems.

In order to obtain an absolutely even tension of the thread, in particular, to eliminate peaks of tension which occur when the thread is drawn unevenly from the bobbin and which may have unpleasant results, a brake for the thread acting together with a thread tension meter can be provided in an inherently known manner between the thread bobbin and the feeding drum to effect a compensation of any peaks in the tension of the thread caused by the thread bobbin, the tension meter controlling the thread brake.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective, schematic illustration of thread feeding devices applied to a circular knitting machine (shown in a fragmentary view only) to illustrate the method;

FIG. 2 is the feeding drum of the device shown in FIG. I partly in axial section, in side view, and to a different scale;

FIG. 3 is a perspective of a number of thread supply devices as shown in FIG. I to illustrate in a simplified manner the arrangement of the devices on the machine and the common driving means;

FIG. 4 is a perspective of a tension feeler device combined with electrical thread brake detector for disconnecting the device shown in FIG. I;

FIG. 5 is an electrical schematic diagram explaining the operation of the device shown in FIG. 1; and

FIG. 6 is a schematic diagram of the function of the analog pulse comparator.

The thread or yarn stored on the bobbin 1 (FIG. I), or any other thread package, is led by means of guide rollers 2, 3 to a thread brake 4. From there the thread is led over an electricoptical indicator 5, which operates according to the stroboscopic principle, to a feeding drum 6. As shown in FIG. I, the thread is wound several times around this thread feeding drum 6 which is provided with a smooth and cylindrical outer surface, so that practically no slip occurs between the outer surface and the loops of the thread. Thereafter, the thread is led over a combined thread feeling and disconnecting aggregate 7 to the knitting position 8 at which an electrical knocking-over adjustment 9 is indicated in a simplified manner.

The feeding drum 6 which pulls the thread in the direction of the arrow (FIG. 1) from the bobbin 1 is connected by means of an adjustable slip coupling with a source of energy, which is formed, for example, by a belt 10 which is driven along the circumference of the machine, as shown schemati cally in FIGS. 1 and 3.

The machine may be driven also by means of other known driving agents, like a toothed belt or a friction wheel, or each element may be driven separately which may be advantageous for certain cases.

The construction of the feeding drum 6 and the slip coupling associated with same can be seen in FIG. 2.

A hollow axle 25 is attached to the support 24, shown in FIG. 2, which is mounted by means of screws 24 on the sup porting rail 27 of the machine, shown in FIG. 1, in the inner bore of which said axle a shaft 11 is rotatable by means of two ball bearings 12, but axially unmovable. The shaft 11 is connected to a cylindrical outer drum 13 made of an electrically conductive material which is provided with a layer 14 forming the surface of the feeding drum. The layer 14 is made of a material which increases the friction of the thread wound around it, so that the thread cannot slip on the feeding drum. The drum surface 14 may also be highly polished, which may be advantageous in certain cases.

Inside the metallic cylinder 13 of the feeding drum 6 an exciter coil 15 is arranged coaxially and is surrounded by a sleeve 16 which is made of a magnetic material of good permeability, for example, iron, and has the shape of a moulded body, as shown in FIG. 2. The sleeve or moulded body 16 is constructed in two parts, the butt joints between the two parts 16 being seen at 18. The outer surface of the moulded body 16 which faces the cylindrical part 13 is constructed like the rotor of a salient pole, axial air gap type motor (sometimes referred to as a pancake type" motor) which is achieved by arranging the butt joints 18 in an undulating or zigzag line.

Both parts of the moulded body 16 are attached to a hollow shaft 19 which rests by means of roller bearings 20 on the stationary hollow axle 25. The hollow shaft 19 is connected rigidly with a grooved wheel 21. The exciter coil 15 situated inside the moulded parts 16 is connected to two slip rings 22 which are provided with brush holders 23 supplying current. The two slip rings 22 are insulated, or the grooved wheel 21 together with the axle 19 is made of an insulating material.

The mode of operation of the device is as follows:

The hollow shaft 19 and with that the moulded body parts 16 resting on the shaft and the exciter coil situated inside said parts are driven by engagement of the belt 10 (FIGS. 1 and 3) with wheel 21 at a constant speed which is higher than the highest speed required for the maximum thread consumption. The magnetic lines produced by the exciter coil 15 close around the metallic cylinder 13 of the feeding drum 6. Due to the relative movement between the metallic cylinder 13 and the field, eddy currents are induced in the cylinder 13 which results in a pulling effect between the rotating magnetic system l5, l6 and the cylinder 13. The degree of slip and with that the rate of feed of the thread is changed by altering the magnitude of the exciter current. The exciter current is adjusted by a tension feeler 17 (FIG. 4) which is provided in the thread feeling and disconnecting aggregate 7 which will be described in the following.

The thread feeling and disconnecting aggregate 7 (FIG. 4) is mounted on a common base 28, to the upper half of which the thread feeler 17 is attached. This feeler comprises a twoarmed lever turnable around its center of gravity, the turning axle 30 of which rests easily movable in a bearing of the base 28. The core of a spiral leaf spring 29 is attached firmly to the turning axle 30, while the outer end of the spring 29 is anchored to a block which is adjustably attached by means of a screw 32 to a holder 33 fixed to the base 28. The spring 29 acts as a counter force to the thread which is guided, as shown in FIG. 4, over the rollers 34 and, in the direction of the arrows, to the knitting position and due to its tension exerts a diverting force on the two-armed lever. A contact finger is firmly attached to a pivoting axle 30 which can engage a resilient contact tongue 36 of an on and off switch 43 with a non-resilient counter contact 37 when the pull of the thread increases. When the thread is no longer pulled, the current supply is switched off by the switch 43.

On the lower half of the base 28 there is an electrical disconnecting device 46, the

contact tongues

38 and 38a of which are short-circuited when the thread breaks.

The thread, guided by eyes 39, presses the feeler roll 48 against the tension of the spiral leaf spring 49, which can be set in the same manner as the thread feeler 17. The machine is switched off when the tension of the thread decreases or when the thread breaks, in that contact release 50 presses the lower resilient contact tongue 38 against a harder contact tongue 38a arranged above the first one.

FIG. 3 illustrates a different embodiment, in which thread feeler aggregates 17 controlling the exciter current of the coil 15, are replaced by potentiometers 26, the setting of which is controlled by a lever 260 connected to a roller 26b over which the thread runs. The potentiometers 26 thus control the current through coils l5.

Structures which are functionally and technically equivalent to the springs 29 which produce a counter force may be used.

The electrical apparatus 51, shown in FIG. 1, which is attached to the supporting rail 27 carrying the thread feeding drums, serves as a common pulse emitter for all indicating in struments 5 which operate, as mentioned above, on the stroboscopic principle. The indicating instruments are provided with perforated disc wheels which are turned by the thread. The thread is wound by almost 360 around the thread guiding groove of the wheels. Stroboscopic lamps are placed behind these discs driven at the rate of the thread, which lamps are supplied with electrical pulses by the central pulse emitter 51. By utilizing the known stroboscopic effect, it is possible to obtain the same rate of feed of the thread at each knitting position or station by altering the knocking-over posi tion of the stitch. This is achieved as follows:

After the correct stitch knocking-over position has been determined at one knitting position, the pulse sequence of the apparatus 51 is adjusted to strobe the lamps until the indicating wheel of the instrument 5 appears to be stationary. As the pulse sequence determined in this manner is fed to all indicating or stroboscopic instruments 5, all other knitting positions can be brought into uniformity by observing the relevant indicating instruments 5, while adjusting each stitch knockingover setting by hand until the disc wheel of each indicating instrument 5 appears to be stationary.

After the rate of feed of the thread to all knitting positions of the machine has been synchronized by the above mentioned method, any further adjustment from this basic setting (0" adjustment) can be made automatically in dependence on the control by the thread feeler 7 or 26. This automatic adjustment is achieved as follows:

When the knitting machine is switched on, i.e. when the driving motor is switched on and the machine is ready for the knitting operation, a contactor 40 having a normally open contact 400 and a normally closed contact 41 (FIG. 5) pulls in. The contact 400 connects the DC. source 42, so that a voltage is developed across the terminals of the ON-OF F switch 43. This switch 43 can be actuated by the attached feeler arm 17 (FIG. 4) which is controlled by the tension of the thread. When the tension of the thread increases, the switch 43 (FIG. 5) is closed (FIG. 4), so that the exciter coil 15 of the feeding drum 6 (FIG. 2) is supplied with current. Since the coil is driven, the separately journalled feeding drum is pulled along by the resulting eddy current effect. Thus thread is fed to the knitting position.

A lamp 44 serves for optical indication of the eddy current coupling which, due to its inertia, will glow only faintly, since switch 43 is connected only for short instants.

When the tension of the thread decreases, the feeler arm 17 connected to switch 43 alters its position, so that the contacts 36, 37 are opened. Consequently, the feeding drum 6 of the thread feeding device is no longer pulled along.

The continuous interaction between the on and off connection of the switch 43 in accordance with the embodiment of FIGS. 1 and 4 results, in general, in an evenly, controlled speed of the feeding drum and with that in a corresponding control of the total feed, i.e. the quantity of thread fed to the respective other knitting positions. The tension of the thread, therefore, adjusts automatically the feed of thread. A diode 45 (FIGS. 1 and 5) connected in parallel to the exciter coil [5 (HO. 2) cuts the voltage peaks occurring when the switch 43 (FIG. 4) opens and prevent burning of the contacts.

An electrical disconnecting device 46 (FIG. 4) comes into operation, for example, when the thread breaks, to stop the machine. Contactor 40 opens, and contact 4| will energize the contacts of relay 47. Relay 45 has its coil connected by means of conductors 52 parallel to the usual braking magnet of the machine, not shown in the drawing. The relay 47 thus supplies DC. voltage to the exciter coil l5 independently of switch 43. As the exciter coil 15, which is driven from the machine, consequently also comes to rest when the machine is stopped, the magnetic field of the now stationary energized exciter coil acts as a brake on the still rotating feeding drum 6, so that the feeding of the thread is quickly stopped.

The knocking-over position can be adjusted, starting from the adjustment, in the plus and minus direction. Adjustment is also possible from pulse apparatus 51, simultaneously and synchronously affecting all knitting positions. For this purpose, small adjusting motors 9 (FIG. I) are provided at each knitting position connected to apparatus 51 which adjust the knocking-over device in accordance with the pulse sequence set as above described. The control system also may be constructed, that the adjusting motors 9 are included in the control circuit of the feeding drum 6, in order to maintain the rate of feed of the thread constant.

Control of the thread supply can be obtained automatically by a closed control loop which is arranged to pick off pulses from drums 6 which are, sequentially for the various knitting positions, compared with pulses from a reference source. Instead of pulse sources, equivalent devices can be used to provide electrical signals having other measuring characteristics, such as frequency, amplitude or the like.

Referring now to FIG. 6: A thread controlled pulse source 55 is provided, each coupled to a drum 6 of any knitting position to sense the speed of the respective drum 6 and provide a pulse sequence representative of this speed. Such pulse sources are known, and may include, for example, small magnets mounted on the circumference of the drum and passing a fixed coil. The pulses from the thread controlled pulse source 55, from each of the knitting positions, are applied to individual contacts of a stepping switch 77, to be subsequently (as will appear in detail below) compared with a fixed pulse sequence. Stepping switch 77 is shown connecting, for example, the first thread control pulse source. The output from stepping switch 77 is applied to an isolation amplifier 56, which amplifies the pulses and applies them to a monostable multivibrator 57, having a variable pulse width (as schematically indicated by variable resistance t). The pulses from monostable multivibrator 57 are applied to a charging circuit 58, which, over a resistance (not shown) charge a condenser positively with respect to a reference datum, for example ground to provide a sensed signal thereon. The condenser likewise is not shown.

A reference pulse source 74 connected to supply reference pulses at a predetermined rate, for example as determined by perfect knitting (and which may be derived from unit applies reference pulses to an isolation amplifier 6], to trigger a monostable multivibrator 60 which, in turn, activates charging circuit 59 which, over a resistance, charges a condenser (not shown) with negative polarity with respect to the datum (for example ground) to provide a reference signal thereon. The charges on the condensers from charging

circuits

58, 59 are compared in a comparator circuit 62. Comparator circuit 62 is controlled to be on or off from the start-stop circuit 76; additionally, it can be blocked by application of a signal on line 70, as will appear below. Let it be assumed that comparator circuit 62 is active or on (not blocked, and the circuit started) then the absolute value of the two voltages applied from charging

circuits

58, 59, are compared (arithmetically added since one is positive and the other negative). The resulting output potential will control the one or the

other multivibrator circuit

63, 64, depending whether the potential is positive, or negative. Flip-

flops

63, 64 are connected to control the coils of

relays

65, 66, respectively; relays 65, 66 are further connected to stepping switches 78, 79 to control the operation of a motor 73 which corresponds exactly to motor 9 controlling the knock-over point at a specific knitting position. Stepping switches 78, 79 are synchronized with the stepping switch 77, as indicated by the dashed lines. Depending on the time that a

relay

65 or 66 is activated, the motor will turn in the one, or other direction to adjust the knock-over point. Simultaneously, and until the comparison voltage at the comparator stage 62 is zero, an indicator lamp at indicating until 68 will light to show that a motor is turning.

When the motor 73 (corresponding to motor 9) has reduced the error at a specific knitting position, so that the output at the comparison stage 62 is zero, the flip-flop 63 (or 64, respectively) will return to its other state, disconnecting relay 65 (or 66, respectively) and thus motor 73. When both flip-

flops

63, 64 are in their RESET state, the AN D-gate 67 is energized which controls the center, or 0" indicator of indicating unit 68. Additionally, the output from AND-gate 67 is applied to a timing circuit 69, which again may be of variable time setting (as indicated by the potentiometer t), which controls a monostable multivibrator 70. After the motor 73 has been disconnected for a predetermined period of time, that is after ANDgate 67 had been active for such time, a pulse is obtained from monostable multivibrator 70 which controls stepper control 7] to cause the stepping switch 77, and stepping switch 78, 79 to step by one unit, thus changing the control function to that of the next knitting position. Simultaneously, the pulse from monostable multivibrator 70 is applied to comparator 62 to block the comparator and discharge the condensers charged by the charging circuit so that a new and independent measuring cycle may commence.

It is desirable to supply this network by a stabilized voltage source, schematically indicated at 72. If a specific knitting position is to be checked, the stepping switch can be manually operated by activating a manual control 75, causing stepping control 71 to step the

switches

77, 78, 79 through a desired number of steps and connecting a selected knitting position. The start-stop control 76 can be coupled with the start-stop of the knitting machine itself.

The comparison device described in connection with FIG. 6 may be termed an analog-pulse comparator; similar effects can be obtained by digital circuits. Upon deviation of a knitting position from the ZERO adjustment, change of the knock-over point of the loops will be obtained automatically, so that the quantity of thread used will again correspond to the desired speed. Simultaneously, the tension sensing element will maintain thread tension constant by controlling the speed of the thread supply drum, so that the individual knitting positions will automatically adjust themselves to the knitting conditions prevailing thereat, thus compensating for possible individual variations and resulting in absolutely even and uniform knitting at the various positions.

Although the synchronization of the feed of the thread to the individual knitting positions of a multi-system machine is described in the foregoing, it is, of course, also possible to synchronize a number of separate machines having one system each. When the same types of yarn are used for the same types of articles, all machines which are synchronized in the above manner will produce an unchanged quality of material over a long period 1 claim: 1. Method of obtaining equal supply of thread to a plurality of knitting stations in multifeed circular knitting machines having rotating thread supply drums over each of which thread is looped to be supplied thereby essentially without slip of the thread over the drum, said method comprising generating a thread speed reference command signal having a characteristic representative of desired speed of the thread being delivered to a first knitting station;

separately sensing the speed of the thread supply drum and thus of the thread being delivered to each knitting station and deriving, for each knitting station, a sensed speed signal having a characteristic representative of sensed thread speed at the respective knitting station;

separately sensing the tension of the thread being delivered to each knitting station and deriving, for each knitting station, a sensed tension signal having a characteristic representative of sensed thread tension at the respective knitting station;

controlling the speed of the thread supply drum at the respective knitting station by the tension signal of the respective knitting station to provide constant thread tension between the respective supply drum and the respective knitting station;

comparing the respective sensed speed signals of each knitting station with said thread speed command reference signal and deriving, for each knitting station, a speed error signal;

and adjusting the knock-over point at the respective knitting stations in dependence on the respective speed error signal whereby the amount of thread being delivered to respective knitting positions will be controlled by the constraint of the reference command signal.

2. Method according to claim I, in which the knockover position of one of said stations is adjusted for perfect knitting;

wherein the step of generating the thread speed reference command signal comprises deriving a signal representa' tive of thread speed from said one station adjusted for perfect knitting.

3. Method according to claim I, wherein the step of generating a reference command signal comprises the step of generating a pulse sequence having a predetermined repeti tion rate.

4. Method according to claim 3, in which the knock over position of one of said stations is adjusted for perfect knitting;

including the step of driving a stroboscopic disc at each knitting station by the thread including the step of adjusting the pulse rate such that the stroboscopic disc of said one station will be illuminated to appear stationary under said perfect knitting condition;

supplying pulses at said adjusted pulse rate to the stroboscopic lamps of the other knitting stations;

and adjusting the knock'over position of said other knitting stations until the stroboscobic discs at said other stations appear stationary.

5. Method according to claim I, for use in a knitting machine having an electrically operated knock-over adjusb ment mechanism, wherein the step of individually adjusting the knock-over points of the stations includes the step of ap plying the error signal to said electrical knock-over adjustment mechanism to control the setting thereof.

"UNITED STA'lES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 677 O36 Dated July 18 1972 1L ii certified that error appears; in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading add: Claims priority, Germany on March 25, 1966, Application No. P 17 85 501.5.

Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents f U 5 c IVFFVH -H'NY rarN lm. HILE wsmm5 JM

Claims

1. Method of obtaining equal supply of thread to a plurality of knitting stations in multifeed circular knitting machines having rotating thread supply drums over each of which thread is looped to be supplied thereby essentially without slip of the thread over the drum, said method comprising generating a thread speed reference command signal having a characteristic representative of desired speed of the thread being delivered to a first knitting station; separately sensing the speed of the thread supply drum and thus of the thread being delivered to each knitting staTion and deriving, for each knitting station, a sensed speed signal having a characteristic representative of sensed thread speed at the respective knitting station; separately sensing the tension of the thread being delivered to each knitting station and deriving, for each knitting station, a sensed tension signal having a characteristic representative of sensed thread tension at the respective knitting station; controlling the speed of the thread supply drum at the respective knitting station by the tension signal of the respective knitting station to provide constant thread tension between the respective supply drum and the respective knitting station; comparing the respective sensed speed signals of each knitting station with said thread speed command reference signal and deriving, for each knitting station, a speed error signal; and adjusting the knock-over point at the respective knitting stations in dependence on the respective speed error signal whereby the amount of thread being delivered to respective knitting positions will be controlled by the constraint of the reference command signal.

2. Method according to claim 1, in which the knock-over position of one of said stations is adjusted for perfect knitting; wherein the step of generating the thread speed reference command signal comprises deriving a signal representative of thread speed from said one station adjusted for perfect knitting.

3. Method according to claim 1, wherein the step of generating a reference command signal comprises the step of generating a pulse sequence having a predetermined repetition rate.

4. Method according to claim 3, in which the knock-over position of one of said stations is adjusted for perfect knitting; including the step of driving a stroboscopic disc at each knitting station by the thread including the step of adjusting the pulse rate such that the stroboscopic disc of said one station will be illuminated to appear stationary under said perfect knitting condition; supplying pulses at said adjusted pulse rate to the stroboscopic lamps of the other knitting stations; and adjusting the knock-over position of said other knitting stations until the stroboscobic discs at said other stations appear stationary.

5. Method according to claim 1, for use in a knitting machine having an electrically operated knock-over adjustment mechanism, wherein the step of individually adjusting the knock-over points of the stations includes the step of applying the error signal to said electrical knock-over adjustment mechanism to control the setting thereof.