DE3304546A1 - DRAWING DEVICE FOR KNITTING MACHINES - Google Patents

Description

description

The present invention relates to a fabric take-off device for knitting machines, in particular flat knitting machines according to the preamble of claim 1.
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A goods take-off device for flat knitting machines, in which the adjusting device is designed mechanically and is directly assigned to the take-off roller for example from DE-PS 1,081,998. This goods take-off device works on the principle of friction, i.e. the goods are pulled by a pressure lever pressed against the take-off roller and thereby taken along. The driving force required for the take-off roller is used to adapt to the respective amount of knitting with weights and complicated weight adjustments regulated. Such goods take-off devices are not only mechanically complex and therefore expensive, but also takes up a lot of space.

A goods take-off device for knitting machines of the type mentioned at the beginning, i.e. in which the adjusting device

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direction is assigned to the drive motor is known from DE-AS 26 31 223. at In this known goods take-off device, the drive motor is a permanent magnet excited direct current motor and the actuating device, among other things, with a constant current source and a clock generator Mistake. The required tensile stress is set by changing the amperage of the armature current, which takes place in that the armature current of the drive motor is clocked. This well-known Goods take-off device is, however, essentially only there to ensure a common, uniform drainage of the drive devices for the knitting devices and the goods take-off device ensure when the drive devices are switched off, for example. Another disadvantage of this known goods take-off device is that no input disturbances, such as. Temperature increase and the like. Can be detected. Furthermore, it is not practical, besides the to use a DC machine for other AC and three-phase drives for goods withdrawal, a constant DC power source is also required.

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The object of the present invention is to provide a goods take-off device for knitting machines, in particular To create flat knitting machines of the type mentioned above, with which it is possible to use a three-phase drive and to record the most important input disturbances and regulate. This is intended to be as precise as possible with the aid of an inexpensive circuit take place.

This task is achieved in a goods take-off device for knitting machines, in particular flat knitting machines of the type mentioned achieved by the features specified in the characterizing part of claim 1.

In the goods take-off device according to the invention, a phase control is used, which are only arranged in one phase or in one strand of the three-phase fed rotating field motor is. This is a relatively simple and inexpensive measure made possible by the setpoint / actual value comparison also leads to a precise regulation in which the essential disturbance variables are recorded. Of the The target value can come from a computer, for example, in which the data for the withdrawal of goods are dependent on

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the type of knit, the type of weave, the fabric width and the like. Are entered. Through the Recording the essential disturbance variables will also have a retroactive effect on the actual value of the goods deduction on the motor and thus on the phase control circuit achieved so that also from this Basically, a very precise setting or adjustment option is given. At the same time it will Mains voltage fluctuations are also compensated.

In a first preferred embodiment of the present invention, the phase control circuit an input for the actual value of the motor current in the strand in which the phase control circuit is arranged, and an input for the actual value of the temperature of the engine. Here are the main disturbance variables such as mains voltage fluctuations and temperature increases in the motor. The advantage here is that These actual values are tapped on measuring elements, sensors or the like, which are attached to stationary parts of the Drive are arranged and can therefore be manufactured and installed in a cost-effective manner and work reliably.

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According to a second preferred exemplary embodiment of the present invention, the phase control circuit has an input for the actual value of the torque of the motor. This embodiment Although this means the technically better solution, since all input disturbance variables are recorded and can be adjusted, but the practical construction is a bit more complex because the torque measurement takes place on the rotating motor output shaft.

The setpoint specification can either be analogue or digital. Is based on the actual torque that occurs adjusted on the engine, it can be useful to set the torque range in a variety of For example, to split 30 individual torques, from which the value is then selected, that of the digital Setpoint specification corresponds.

The goods take-off must not only be adjusted to the type of knitted fabric, the type of weave, the width of the goods and the like but it must also be taken into account that the goods take-off roller from a standstill, e.g. then, if no torque was specified, it must be set in 5 rotation again. The tear-away

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moment to overcome that by the pressure of the pressure roller or rollers on the fabric take-off roller caused.

A problem-free start from standstill or acceleration of the drive motor without delay to ensure, is according to a further embodiment of the present invention Phase control circuit with an input for a loop reversal pulse for brief increase of the torque, i.e. to push the drive motor with a small actual torque in the range provided by zero. This reversal pulse can be adjustable or constant in terms of duration and height.

It is expedient to have it constantly at a level that only makes it effective can come when the drive motor is operated in the speed range close to zero. It is, however Setpoint specification with respect to the torque of zero given, then this knitting reversal pulse is off hidden and only shown again when the torque setpoint specification is greater than zero.

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From the aforementioned start-up of the drive motor from standstill during operation of the entire Flat knitting machine is to be distinguished from that which is due to the shutdown of the flat knitting machine due to a defect such as yarn breakage or the like. Usually would after switching on the flat knitting machine again, the drive motor of the goods take-off device are immediately ramped up to full target torque, but this has the disadvantage that the knitted fabric is pulled too much, firstly because at that moment no new row has been knitted and secondly, because such a regulation to harmonics and thus for a short time still leads to higher torque. In order to avoid this disadvantage, according to a further exemplary embodiment a circuit, preferably provided in the phase control circuit (26, 26 ') is that a slow run-up of the drive motor (12) to the predetermined setpoint from the Stand after the machine is switched on again. This prevents the knitted fabric in such a case, especially with medium and large torque setpoint specifications, too much is stretched.

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Further details and configurations of the invention can be found in the following description, in which the invention based on the embodiments shown in the drawing is described and explained. Show it:

Figure 1 in a schematic representation Side view of a goods take-off device with an associated adjusting device,

FIG. 2 shows the circuit arrangement of an adjusting device for the goods take-off device according to an embodiment of the present invention,

FIG. 3 shows the circuit arrangement of an adjusting device for the goods take-off device according to another embodiment of the present invention,

and

Figure h shows the diagram of a torque characteristic.

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The goods take-off device 11 according to the invention, with an electrical adjusting device acting directly on a drive motor 12 13 or 13 'is provided, is used to deduct the goods both to the type of knitting, i.e. to the type of knit, type of weave and the like, as well as to the Number of needles, i.e. to adapt to the fabric width, in order to carry out a sensitive control to be able to. This should be independent of external interference, such as mains voltage fluctuations, Temperature increases in the engine and the like. Take place.

FIG. 1 shows, in a schematic manner, a goods take-off device 11. Comes out of the needle beds 16 the goods 14 in, for example, the vertical fall line downwards and tangentially hits a take-off roller 17. This is, for example, via a drive belt 18 driven by the drive motor 12. Against the take-off roller 17 are uniform over their length distributed pressure rollers 21 pressed in a manner not shown, with between the take-off roller and the pressure rollers 21, the web 14 is guided and deflected. The web of goods arrives either in a goods tub 22 or on a goods winding device (not shown). Of the

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Drive motor 12 is connected to a three-phase voltage source 23 three-phase connected, with one phase or one line (e.g. in the Phase R) the electrical adjusting device 13 or 13 'to adjust the pulling force of the goods take-off, i.e. the torque of the motor as a function of a given setpoint and under control is arranged by disturbance variables. The drive motor 12 is a three-phase operated asynchronous motor with squirrel-cage rotor, the three-phase stator winding of which is star-connected, with the star point floated, i.e. not fixed.

Figures 2 and 3 show embodiments of the electrical adjusting device 13 and 13 ', the is arranged in strand R of the three-phase supply line to the drive motor 12. The adjusting device 13 has a phase control circuit 26 or 26 ', which is in the course of phase R and the depending on a setpoint value, the size of the to be fed or fed to the drive motor 12 in this phase R Voltage determined in terms of amount in that in every positive and / or negative half-wave the alternating voltage a certain angular range is suppressed. The setpoint that is sent to the input

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Klenunen 27 of the phase control circuit 26 or 26 'is supplied, for example. From a computer that depends on the type of knitted fabric and the number of needles determines the size, i.e. the speed and pulling force of the fabric take-off. Both Embodiments of Figures 2 and 3 also have in common that the phase control circuit 26 or 26 'of the actuating device 13 or 13' is provided with an input 28 to which the Star point 2 9 of the star-connected stator winding 31 is fed. Furthermore is a Input 3 2 provided, via which a reversal pulse is supplied potential-free, whose Function is described in more detail below. The inputs for the recorded actual values of the drive motor 12 are in the two exemplary embodiments according to Figures 2 and 3 different.

In the embodiment shown in Figure 2, the phase control circuit 2 6 has the Adjusting device 13 has two actual value inputs 33 and 34, one of which is the actual value of the engine temperature and the other is the actual value of the phase current in phase R or a value derived from it Value is added. The actual value for the motor

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temperature is taken from a temperature sensor, which is located in the stator of the drive motor 12, that is, it is arranged near the stator winding 31. The actual value for the phase current in phase R. is taken as a voltage drop across a resistor 37, which is arranged in the R phase.

In the exemplary embodiment in FIG. 3, the phase control circuit 26 'is the adjusting device 13 'provided with a single actual value input 39, which is the actual value of the torque of the drive motor 12 is supplied. The actual torque value is taken from a torque sensor 41, on the output shaft 42 from the drive motor 12 to Draw-off roller 17 is arranged.

The function of the adjusting devices 13, 13 'in both exemplary embodiments is as follows: Correspondingly a certain predetermined target value with regard to the speed and the force of the goods take-off and thus the torque on the output shaft of the drive motor 12 takes place a certain of the circuit 26, 26 'caused the phase R cut, so that in this phase the drive motor 12 a certain versus the applied voltage

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reduced voltage is supplied. A change in the specified setpoint takes place accordingly a change in the phase angle and thus a change in the motor voltage of the Phase R, which results in a change in the speed or torque of the motor 12. Surrender if the setpoint specification remains the same, changes in the other internal and external data will be this either via a change in the string current and / or the motor temperature or the torque output, what about supply voltage fluctuations, room temperature changes, load changes and The like. Can originate, detected and the relevant inputs of the phase control circuit 26, 26 ' fed. A comparison is made there with the setpoint specification, which results in a change in the phase control and thus a change in the torque output at the drive motor 12 results. Is now with a lot a few needles, i.e. very narrow knitted pieces, a torque setpoint is created for the Deduction of goods of close to zero is specified. In order to now accelerate or restart the drive motor 12 from this very low rotational speed or to enable it from the stand (zero torque) without delay, is the knitting reversal pulse

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provided, which is fed to the input 23. This reversal pulse is used for a short time Increase the torque, so as a pushing impulse for the motor 19 and the duration and Height can be adjusted. This knitting reversal pulse can be applied continuously, but it does is then only of a height that ensures that this impulse only takes effect when a nominal value specification with regard to the torque takes place in the range of zero, i.e. that this is superimposed Impulse then plays no role if the torque setpoint specification is higher than, for example. that which is necessary to overcome the breakaway force. However, there are also measures provided in order to suppress this reversal pulse when the torque target value is specified is equal to zero, since then no pushing of the drive motor 12 should take place. The knitting reversal pulse appears then again when the turning point is reached. It is of course also possible to use the Always allow the rope reversal impulse to take effect only when it is needed for a brief push will. Except in the area of the reversal points of the slide, this pushing impulse also comes into play Effect when relatively small torques are used as the setpoint

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is given, for example. When the width of the goods is very small.

The setpoint specification can be either analog or digital. In the case of a digital setpoint specification, as in the embodiment shown in FIG. 3, the one shown in FIG Torque curve subdivided into, for example, 30 scale divisions, with the relevant digital values directly corresponds to the scale division of the same number and thus a certain torque.

The drive motor 12 also has a mechanical one, although this is not shown in the drawing Backstop in the form of a rotary pawl lock to prevent that when switched off Motor or, in the event of a power failure, the train of the material web turns the motor back.

Furthermore, in a manner also not shown, the goods take-off device 11 is provided with a monitoring device provided, which monitors the maximum permissible rotational speed of the take-off roller 17 or the output shaft 4 2 of the drive motor 12. For example, part of this monitoring device is on

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the take-off roller 17 attached cam which cooperates with a stationary switch with a timer. If the take-off roller 17 and thus the cam rotates too quickly, this is also taken into account by the the timer provided switch detects what a shutdown of the drive motor 12 or the entire Knitting machine. This turning too fast can take place when the knitted fabric falls down, so there is no longer any withdrawal of goods.

From the above-mentioned start-up of the drive motor 12 from standstill during operation of the throughout the flat knitting machine is to be distinguished from that which is due to the switching off of the Flat knitting machine due to a defect, e.g. falling of the knitted fabric, yarn breakage or the like., he follows. Normally, after the flat knitting machine was switched on again, the drive motor would the goods take-off device can be run up to full target torque immediately, but this The disadvantage is that the knitted fabric is pulled too much, firstly because there is no new one at that moment Row has been knitted and secondly because one

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such regulation on harmonics and thus leads to an even higher torque for a short time. To prevent this, is in the phase control circuit 26, 26 'a circuit is provided which allows the take-off roller 17 or from its drive motor 12 to the setpoint torque specified for this operating state from the Stand then enabled when the flat knitting machine is switched on again and thus for example a restart pulse occurs. The phase control angle becomes during this run-up slowly increased up to the specified nominal or target value, so that not only the torque slowly approached the setpoint, but harmonic oscillation is also prevented. this is particularly in the case of a current setpoint specification in medium and higher torque ranges important.

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Claims (11)

Claims I 1.) Goods take-off device for knitting machines, in particular flat knitting machines, with a drive motor and an associated adjusting device for adjusting the extraction force of the drive motor, characterized in that the drive motor (12) is a three-phase rotating field motor in a known manner and that the adjusting device (13 , 13 ') is formed by a single-phase phase control circuit (26, 26') with inputs (27, 28, 32 to 34, 39) for the setpoint specification and Post account Stuttgart 507 71 -705 (bank code 600 100 70) Dresdner Sank Stuttgart 1919 854 (bank code 600 800 00) is provided for at least one actual value taken from the drive motor (12). 2. Goods take-off device according to claim 1, characterized in that the phase control circuit (26) has an input (33) for the actual value of the motor current in the strand (R) in which the phase control circuit (2 6) is arranged, and an input (3U) for the actual value of the temperature of the motor (12). 3. Goods take-off device according to claim 2, characterized in that the actual value of the motor current is taken from a resistor (37) which is arranged in the strand (R) provided with the phase control circuit (26). 4. Goods take-off device according to claim 2 or 3, characterized in that the actual value for the motor temperature is taken from a temperature sensor (36) arranged in the stator of the motor (12). . 4118 5. Goods take-off device according to claim 1, characterized in that the phase control ^{circuit (26 1} ) has an input (39) for the actual value of the torque of the motor (12). 6. Goods take-off device according to claim 5, characterized in that the actual value for the torque on the motor shaft (42) is removed. 7. Goods take-off device according to one of the preceding claims, characterized in that the rotating field motor (12) is an asynchronous motor provided with a squirrel-cage rotor, in which the star point (29) of the stator winding (31) is floating and as an input (32) in the phase control circuit (26 ¹ ) is performed. 8. Goods take-off device according to one of the preceding claims, characterized in that the setpoint specification is digital or analog. 9. Goods take-off device according to claims 5 and 8, characterized in that in the case of a digital setpoint specification of the torque in each case a value 4118 from a torque range specified by a large number of, for example, 30 individual torques is selected. y < 10. Goods take-off device according to one of the preceding claims, characterized in that the phase control circuit (26, 26 ') has an input (32) for a reversal pulse for briefly increasing the torque of the drive motor (12) at a small actual torque in the range of zero is. Y> 11. Goods take-off device according to claim 10, characterized in that the knitting reversal pulse is applied constantly and can be faded out at a torque target value specification of zero. 12. Goods take-off device according to one of the preceding claims, characterized in that a monitoring device for the maximum rotational speed of the take-off roller (17) is provided. 4118 13. Goods take-off device according to one of the preceding claims, characterized in that the drive motor (12) is provided with a preferably mechanical backstop. 14. Goods take-off device according to one of the preceding claims, characterized in that a circuit, preferably in the phase control circuit (26, 26 ') is provided, which allows the drive motor (12) to slowly run up to the predetermined setpoint from the state after the machine is switched on again causes. - End of the claim. 4118 010