EP0307769B1 - Knitting machine with a thread-changing device - Google Patents

Description

The invention relates to a knitting machine of the type specified in the preamble of claim 1.

In knitting machines, knotting devices are increasingly used as thread changing devices, in which the new thread is knotted on the old thread when the thread is changed. In this way, precisely localized thread change points can be achieved in the knitted fabric, which is particularly advantageous when changing colors. In terms of control technology, however, the problem arises of controlling the knotting device and the thread feed so that the knot also appears exactly at the desired thread change point in the knitted fabric. The previously known devices for solving the problem mentioned have the disadvantage that a larger number of sensors is required and, accordingly, a larger number of measurement data must be taken into account in the control device, which complicates the structure of the control device.

Furthermore, it is not always guaranteed that the node actually appears exactly at the desired exchange point. If, for example, the thread changing device is provided with a positive working thread delivery device in the form of a so-called tape feeder at a point located behind the knotting device in the thread running direction (DE-A-30 15 191), the slip inevitably associated with such feeders has the consequence that the knot becomes loose gradually shifting more and more in the knitted fabric, so that e.g. In the case of a circular knit fabric, all the knots together form a helically wound line. In addition, only smooth knitwear can be made with positive feeders.

The same and other problems arise when using the only ones known to date device for electronic control of the position of the node (WO-A-82 03 642). This comprises, on the one hand, a positive thread delivery device, which forcibly supplies the thread, which is arranged between the knotting device and the thread processing point, and, on the other hand, a storage drum which is arranged between the knotting device and the thread delivery device and which is assigned a thread winding element which can be driven by a motor, by means of which the thread coming from a supply spool and then the thread running through the knotting device can be wound onto the storage drum. The storage drum and the winding element are operated in the manner of a control device, which is intended to ensure a thread part of constant length on the storage drum, in that the quantity of thread delivered to the thread processing point by the thread delivery device and withdrawn from the storage drum is supplied again by the winding element. It is assumed that a knotting device is used, the thread part arranged in it having to be stopped briefly at the moment of the actual knot formation or moved at a reduced speed. This is made possible in that the motor for the winding element is stopped during the actual knot formation and, after the knot formation has been completed, is operated for a time faster than the current thread speed. This attempts to keep the thread part located on the storage drum and thus also the thread part located between the knotting device and the thread processing point essentially constant, so that it has a preselected length when the next knot is formed, ie the distance between the knotting device and the thread processing point. based on the length of the thread part between the two or the number of machine or needle cycles that the knot needs for its migration from the knotting device to the thread processing point, is always approximately the same.

However, the known device is not free from defects. A major deficiency is, for example, that it is only suitable for the production of ring patterns consisting of horizontal stripes, because a positive thread feed takes place by means of the delivery device and therefore the thread consumption on each needle must be the same. Another major defect is that the device cannot work properly in the long run because sensors are used to measure the thread parts unwound from or wound onto the storage drum, which sensors of the thread delivery device or are assigned to the winding element. If one of the two sensors produces a slight measurement error, then this error is continuously added up, resulting in a sum error and the differential signal used for controlling the motor of the winding element becoming increasingly incorrect. The result of this is that the storage lengths and thus the thread lengths between the knotting device and the processing point also become larger or smaller over the course of time, so that the knots in the knitted fabric move laterally out of the changing point. Such, albeit small, measurement errors can arise, for example, from the fact that the thread in the thread delivery device is subject to slight slip from time to time. Another shortcoming is that a complex control circuit is required.

Finally, a deficiency of the known device is that when a thread break occurs, which usually results in the storage drum being empty, it is not known how many thread turns there were on the storage drum when the thread break occurred, because of the storage length the control process on the one hand and because of the required standstill of the thread during the actual knot formation on the other hand constantly changes. If the exact, previously existing storage length is not restored after a thread break or the control device is readjusted, errors can result. If several thread breaks occur, these can also cause the knots to move away from the changing point.

The invention has for its object to simplify the control device for the thread changing device in a knitting machine of the type mentioned without thereby reducing its accuracy and operational reliability.

The object is achieved in a knitting machine with the devices mentioned at the outset by the characterizing features of claim 1.

By keeping the length of the thread between the knotting device and the thread processing point constant and also storing the thread length required for a desired stitch length, separate sensors can be provided in the control device designed according to the invention which detect the thread movement to a thread storage and the thread movement from a thread storage to the thread processing point capture and correspondingly deliver data to be used in the microprocessor of the control device are eliminated. This significantly simplifies the control device and accelerates the control process. A further simplification of the control device results from the fact that a displacement sensor is used which is independent of the needle division of a needle bed and which delivers a predetermined number of pulses over the entire path length, regardless of whether it is a knitting machine with a finer or coarser needle division. The displacement sensor has the additional advantage that each of its impulses denotes a specific point on the needle bed. A simplification of the signal evaluation and thus also the construction of the control device can be achieved with a displacement sensor, which additionally delivers a zero pulse after each path length, which corresponds to the total length of a needle bed, i.e. in circular knitting machines of a needle cylinder revolution, so that the pulses are new for each distance Zero to be enumerated. This measure ensures that an error that may occur on a route, for example a displacement of a knot position in the knitted fabric, is not passed on to the subsequent routes. So errors could not add up.

By means of the measures according to the invention, a knotting device can be controlled so reliably that it is not necessary to control the control device by locating the knot position in the knitted fabric, which is difficult to implement.

The thread storage device mentioned above is to be understood primarily as storage drums over which the thread is laid in several turns. These Storage drums can be arranged in so-called feeders and can either be designed as continuously driven or stationary storage drums. In the former case, the storage drums do not form real thread stores, but instead cause a positive thread feed to the thread processing point by a movement dependent on the respective operating speed of the knitting machine and the thread consumption, where the thread is accordingly fed with a constant tension and thread quantity. In the other case, with a fixed storage drum, the drum forms a real thread storage device, on which the thread is wound up by means of a first thread finger and unwound by means of a second thread finger. In any case, in the knitting machine designed according to the invention, in order to ensure a constant thread length between the knotting device and the thread processing point, the same number of turns is always observed, which can be ensured in a thread storage device with a fixed storage drum by forcing the winding fingers to perform a synchronous movement, for example the second The winding finger is set in rotation by the thread pull exerted by the processing needles and is moved past a pulse generator, the pulses of which actuate a stepping motor that moves the first winding finger and forces the first winding finger to deliver threads onto the storage drum synchronously.

A further simplification of the control device can be achieved in that parts of the control device are arranged on the individual knotting devices, for example an adjustable thread length storage device and of course sensors which detect the position of knotting device parts can monitor. The thread length between the knotting device and the thread processing point can be different for the several knotting devices. It and the thread length required for a desired stitch length are measured on each knotting device before the start of the knitting process and individually entered into the thread length memory on the individual knotting devices or on the central control device.

Exemplary embodiments of the subject matter of the invention are explained in more detail with reference to the accompanying drawing.

Fig. 1

eine schematische Blockdarstellung der erfindungswesentlichen Teile einer Fadenwechseleinrichtung an einer Rundstrickmaschine zur Herstellung von Bindungen mit gleichbleibendem Fadenverbrauch;

Fig. 2

eine der Fig. 1 entsprechende Darstellung der Fadenwechseleinrichtung einer Rundstrickmaschine zur Herstellung von Bindungen mit wechselndem Fadenverbrauch, z. B. für Jacquardmuster oder Intarsienmuster;

Fig. 3

eine gegenüber Fig. 2 vergrößerte Darstellung eines Speicher-Fournisseurs, teilweise im vertikalen Längsschnitt.

In detail show:

Fig. 1

is a schematic block diagram of the essential parts of the invention of a thread changing device on a circular knitting machine for the production of ties with constant thread consumption;

Fig. 2

1 corresponding representation of the thread changing device of a circular knitting machine for the production of bindings with changing thread consumption, for. B. for jacquard or marquetry;

Fig. 3

an enlarged view of FIG. 2 of a storage supplier, partially in vertical longitudinal section.

In Fig. 1, a knotting device 10 of a thread changing device is shown only schematically as a box. The individual structure of the knotting device is of no interest here. The knotting device is supplied with four threads 11, 12, 13 and 14, between which it is possible to switch by tying a selected new thread to the thread previously used, for example 11. The thread 11-14 selected in each case is guided from the knotting device 10 via a so-called positive feeder 15 to a thread processing point 16 of a circular knitting machine indicated schematically by its needle cylinder 17. In the positive feeder, the thread is laid in several twists over a storage drum 18, which is driven by means of a drive belt 19 depending on the thread consumption and on the speed of rotation of the needle cylinder 17 of the circular knitting machine. Through the positive feeder 15, the respective thread 11-14 of the thread processing point 16 is forcibly fed in the required amount and thus tangentially with a constant tension. The positive drive of the storage drum 18 ensures that the same amount of thread is always rewound onto the storage drum 18 as is drawn off tangentially from the storage drum 18 at the lower end. Accordingly, at any operating speed of the needle cylinder 17, the length of the thread, which extends from the knotting device 10 via the positive feeder 15 to a thread processing point 16 of the circular knitting machine, is always the same size. Each system has a storage drum and each storage drum carries the same number of thread turns.

Circular knitting machines are predominantly multi-system, and each system can be assigned its own knotting device 10. All knotting devices 10 of a circular knitting machine are coupled to a common control device 20, but each have their own control part 21, which is part of the overall control device of the circular knitting machine. The control device 20 includes a displacement encoder, which in the circular knitting machine shown is designed as an angle rotary encoder 22 and is drivingly coupled to the rotating needle cylinder 17 of the circular knitting machine. The rotary encoder delivers a fixed number of pulses over a full revolution of the needle cylinder 17 and, after a full revolution of the needle cylinder, a zero pulse via a control line 23 in the central control device 20 and in the control parts 21. The control device 20 has a special one for each connected knotting device 10 and its control part 21 Interface on. Via a first control connection 24, the knotting device 10 receives command impulses from the central control device 20, which comprises a microprocessor (not shown) and a pattern memory, if knotting is to be carried out. In addition, 24 feedback signals of the knotting device 10 are passed to the control device 20 via this connection. The control part 21 of the knotting device 10 receives the clock pulses of the angle rotary encoder via a second control connection 25, and the zero pulse supplied by the angle rotary encoder 22 via a third control connection 26. At least one adjustable thread length memory can be accommodated in the control part 21 of each knotting device 10 in a manner not shown, and at least one counting stage actuated by the clock pulses of the angular rotary encoder and its zero pulse is arranged. The control part 21 can also have its own microprocessor which from the signals supplied by the central control device 20, taking into account individual switching delay times in the individual knot devices 10, the time of the trigger signal for knot formation is determined as a function of speed. The machine speed is determined from the clock pulses / time unit of the encoder.

However, a central microprocessor can also be accommodated in the control device 20, to which the data set on the control part 21 of each knot device is fed and which then calculates the trigger signals for knotting device 10 and delivers them in a timely manner.

The number of pulses of the rotary encoder over a full revolution of the needle cylinder 17 is fixed, regardless of the diameter of the needle cylinder and its needle pitch. The control device can thus be used on any circular knitting machine without major adjustment problems. The counting stage in the control part 21 of each knotting device 10 is reset to zero after each revolution of the needle cylinder 17.

The instantaneous speed of the knitting machine can be calculated at any time from the clock pulses of the angle rotary encoder 22 and taken into account when determining the time of knot formation. In the central control device 20, the thread consumption per needle during stitch formation is also recorded in the pattern memory, and accordingly that is proportional to the drive of the Needle cylinder 17 set drive speed of the positive feeder 18 is set.

The control device described can be used to produce striped goods and inlaid goods in which the knots appearing in different rows of stitches lie exactly vertically one below the other or are placed at specific points.

2 shows the design of the thread changing device for circular knitting machines on which jacquard patterns are to be produced, where, in contrast to the exemplary embodiment according to FIG. 1, where constant thread consumption has always been assumed at all needle processing points 16, the thread consumption at the individual thread processing points 16 fluctuates. Also in FIG. 2, a thread processing point 16 is indicated schematically by a needle and the same reference numbers are used for all the same parts as in FIG. 1. The device differs from the device according to FIG. 1 essentially in that instead of a positive feeder 15, a real storage feeder 30 is provided, which has a stationary storage drum 18 '. Each coming from the knotting device 10 thread 11-14 is wound onto the fixed thread drum 18 'by means of a first drivable winding finger 31. By means of a second revolving winding finger 32, the thread is drawn off from the fixed storage drum 18 'and passed to a thread processing point 16. The thread can be drawn off by forcibly driving the second winding finger 32. In the present case, it is assumed that the rotational movement of the second Winding finger 32 is caused by the tension exerted on the thread 11 by the needles at the thread processing point 16. Each rotational movement of the second winding finger 32 is determined on a moving disc 33 by means of sensors 34. With pulses supplied by the sensors 34, a forced drive of the first winding finger 31 is effected via a drive motor, not shown in FIG . This fulfills the important condition for the control device that the length of the thread between the knotting device 10 and the associated thread processing point 16 is always the same. A gear 35, which is only indicated schematically, ensures that the storage drum is fixed in the case of rotating winding fingers.

Fig. 3 shows a possible embodiment of a memory feeder 30 '. In a common carrier 36, the fixed storage drum 18 'is arranged and the two winding fingers 31 and 32 are rotatably mounted coaxially to the storage drum 18'. The first winding finger 31 is driven by means of a stepping motor 37 arranged in the carrier 36, to which it is connected in terms of drive via an endless toothed belt 38. The second winding finger 32 is fixedly connected to an aluminum disk 33, which can be serrated at its edge and generates pulses during the rotation of the winding finger in an optical sensor 34, which is acted upon by a light source 39, which drives the stepping motor 37 and thus the first winding finger 31 can be used. At the same time, the aluminum disc serves 33 as an eddy current brake disc in cooperation with a winding 40.

Claims (9)

1. Knitting machine with a needle bed (17) and a thread-changing arrangement with at least one knotting device (10), with a thread storage device (15, 30) which is disposed between the knotting device (10) and a thread preparation point (16) of the knitting machine, and with a control arrangement (20, 21) for the thread-changing arrangement including a microprocessor and a knot data store, there being associated with said thread changing arrangement sensor which emits pulses dependent on the movement of a machine part, but independent of the needle division of the needle bed (17),
   characterised in that the length of the thread (11-14) guided over the thread storage device (15, 30), between each knotting device (10) and the thread preparation point (16) associated therewith, is kept to a constant value held in a store of the control arrangement (20, 21), in that the sensor emitting the movement-dependent pulses is a position-emitter (22) with a fixed number of pulses per unit of length of travel, and in that there is in addition disposed at each knotting device (10), as components of the control arrangement (20, 21), a counting stage which is timed by the position-emitter (22), and may be reset by zero pulses, or another distance store.
2. Knitting machine according to claim 1, characterised in that the position-emitter emits a zero pulse after each path length corresponding to the overall length of a needle bed.
3. Circular knitting machine according to claim 1 or 2, characterised in that the position-emitter is an angular-rotation emitter (22) with a fixed number of pulses per machine revolution, and which emits at least one zero pulse at a fixed circumferential point on the machine.
4. Knitting machine according to one of claims 1 to 3, characterised in that the thread storage device (15) is a feed wheel mechanism driven in dependence on thread consumption and/or by the machine speed, for positive thread supply to the thread preparation point (16), its driven thread storage drum (18) carrying a predetermined number of thread windings.
5. Knitting machine according to one of claims 1 to 3, characterised in that the thread storage device (30) has a stationary thread storage drum (18'), a first winding finger (31) for winding up a thread (11-14) on to the thread storage drum (18'), and a second winding finger (32) for unwinding the thread (11-14) from the thread storage drum (18'), and in that both winding fingers (31, 32) may be driven synchronously.
6. Knitting machine according to claim 5, characterised in that the second winding finger (32) may be moved past a pulse emitter (34), the pulses from which actuate a stepping motor (37) moving the first winding finger (31).
7. Knitting machine according to one of claims 1 to 6, characterised in that there are disposed at each knotting device (10), as components of the control arrangement (20/21) at least one adjustable thread length store, and sensors monitoring the position of parts of the knotting devices.
8. Knitting machine according to one of claims 1 to 7, characterised in that the central control arrangement (20) or the components (21) of the control arrangement have in addition an adjustable thread length store for the thread length per stitch.
9. Knitting machine according to claim 5 or 6, characterised in that the second winding finger (32) is coupled to an eddy current brake (33/40).

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