HK1028908B - Control mechanism for the electromotor of a device for forming a leno edge - Google Patents

Description

Motor control device for a device forming a leno selvedge

The invention relates to a device for forming leno selvedges in a weaving machine with a heddle frame according to the preamble of claims 1 and 2.

A planetary type leno device is known from JP 369627. In the device in question here, the planet gear supports the yarn bobbin and therefore rotates with it. The device operates in such a way that the planetary gear is actuated in accordance with the rotational angle of the heald frame. This means that such planetary leno devices perform a continuous rotary motion corresponding to the angular motion of the heddle frames, that is to say that each of the corners of the planetary leno devices is associated with a respective corner of the heddle frame.

The operation of such a planetary-type leno device is independent of the drive of the heald frames, which allows the planetary-type leno device to be advanced or retarded with respect to the angle of rotation of the heald frames; the movement of the planetary leno device is of course always oriented according to the heald frame movement.

DE 4405776C 1, for example, discloses a device for forming a leno selvedge, in which an electrically controllable servomotor is provided, wherein a capstan forms the rotor of the electrically controllable servomotor. The warp skein-wheel itself has at least two guide elements for the skein, which are twisted around the weft yarns to form leno selvedges.

Furthermore, a device for forming leno selvedges is known from WO97/24479, in which the rotor of the electric motor has arms for guiding the leno. Here too, the leno selvedge is formed by twisting the leno warp guided by the arms around the weft thread.

The two known devices have in common that, for the production of the leno selvedge, an electric motor is provided which runs synchronously with the movement of the palm frame at any time. Of course, the electric motor can be driven in phase-shifted fashion relative to the movement of the heald frame in order to be able to advance the twisting of the weft thread. However, the movement of the motor rotor is always oriented in accordance with the heald frame movement. As a result, it is clear that, in order to implement such a synchronous operation of the leno selvedge device described with the movement of the heald frames, it is necessary to transmit continuous data, in particular from the drive shaft of the weaving machine to the leno selvedge device, in order to achieve the above-described synchronous operation of the motor of the leno selvedge device with the movement of the weaving machine or with the heald frames. In this respect, it is also provided that the electric motor is connected to the drive of the weaving machine, for example, via a so-called electric shaft. This does not mean that the control of the leno selvedges is related to the heddle frames in the known device; in particular, the control of the motor rotor of the leno selvedge device and accordingly its rotary movement is independent of the heald frames, since there is no direct mechanical connection between the heald frames and the leno selvedge device. However, as already explained, the leno selvedge device is connected to the weaving machine when it is moved, which means that the rotor of the electric motor is operated synchronously with the movement of the drive shaft of the weaving machine or correspondingly with the movement of the heald frames.

It is now clear from the results that it is exactly the same as for the formation of a leno selvedge whether the motor rotor of a leno selvedge device runs exactly and at any moment in synchronism with the weaving machine (referred to as the drive shaft or heald frame of the weaving machine). It is only important, in particular, that at the beginning of the weft insertion by the leno selvedge apparatus the two warp threads are also in the shed-open position and that after the end of the weft insertion the warp threads are transferred into the shed-closed position. This means that the problem is only present in the end positions, i.e. "shed open" or "shed closed", which are reached by the leno selvedge device at the latest when the heddle frames are in the respective position. As a result, a movement process which is synchronized at any time between the movement of the motor rotor and the movement of the heald frame is not required at all.

It is therefore an object of the present invention to provide a device of the type mentioned in the introduction, by means of which the electric motor of the device for forming a leno selvedge can be controlled such that the skein-ing, although not dependent on the movement of the heald frames, is still carried out in the time between the shed-open position and the shed-closed position of the heald frames.

In a first variant, provision is made for the motor control to provide a start pulse at the moment when the weaving machine starts to open the shed or when the shed starts to close. Another solution for this purpose is that the control of the electric motor is designed in connection with the weft insertion. In this connection, according to a second variant, it is provided that the motor control device provides a start pulse at the moment when the weft thread starts to be picked or the weft insertion ends. In both cases it is of course required that the rotational speed at which the shed is opened and closed by the motor rotor is higher than the speed at which the shed is opened and closed by the heald frames. Such a control device has the advantage of being very simple in construction and thus inexpensive, since only a few parameters, precisely two parameters, are required for controlling the device for forming the leno selvedge. In contrast to leno selvedge devices with the aid of known control devices, such leno selvedge devices are substantially failure-free in operation.

The invention is further illustrated by way of example with the aid of the accompanying drawings. In the drawings:

FIG. 1 is a schematic representation of the position of the device according to the invention relative to a fabric, with the heald frames and the reed removed for clarity;

figure 2 shows schematically the course of the heald frame stroke or the rotation of the motor rotor of a leno selvedge device over time.

In order to better understand the device, it should first be explained again how the leno selvedge device works; in this connection, reference is also made, inter alia, to the disclosure according to WO 97/24479.

The device 1 shown in fig. 1 is provided with an electric motor, generally indicated by reference numeral 10, which has a central opening 11 for guiding the strands 20, 30. In the embodiment shown, two arm pairs 60, 70 are provided, the axis of rotation extending transversely to the warp threads 40, i.e. substantially parallel to the weft threads 50. It is of course also conceivable for the device to operate with only one arm pair 60, which is arranged on the motor rotor on the fabric side. These arm pairs are designed like propeller blades and are mounted on the rotor. Each arm pair 60, 70 consists of two arms 61, 62 or 71, 72 designed as propeller blades. The two arm pairs 60, 70 extend parallel to each other and are each fixed to the end of the rotor of the motor 10, as can be seen clearly in fig. 1. The ends of the arms 61, 62 or 71, 72 are designed as hooks, and in the area of the hook-shaped bend, there are holes 73, 74 or 63, 64. These holes are used to pass through the skein 20, 30, which is pulled out of the yarn bobbin 80, 90. When the arm pairs 60, 70 and here in particular the arm pair 60 are rotated, a fully leno selvedge 100 is formed in the fabric region. The twisting of the thread (at the position 110) likewise takes place in the feed region of the skein 20, 30 from the thread bobbin 80, 90, and the twisting is cancelled again because the rotor turns in the reverse direction after a certain number of revolutions. That is to say the rotor of the motor runs forward and backward. Here, the untwisting of the leno selvedges 100 is avoided because the weft thread 50 is inserted between the leno warp threads.

Figure 2 shows, on the one hand, the motion of the heald frames over time and, on the other hand, the motion of the electric motor rotor of the leno selvedge device also over time. It can be seen from the figure that the rotor has held the warp in the shed open position at the moment when the heald frame is finally open. Furthermore, it is seen from the curve that the motor rotor has the ability to hold the shed much longer than the heald frame has. The device according to the invention can therefore be operated with smaller sheds and, of equal importance, can be mounted directly on the reed, particularly forward, i.e. between the heald frames. Due to this long-term hold-open of the shed, it is also possible to adapt to the specific requirements of a gripper weaving machine, such as the requirement for a longer dwell time of the gripper in the shed.

The advantage of such a control device is that it can be implemented very simply, since it is not necessary to simulate an electric shaft or an electric cam disk with a great deal of control engineering outlay, and therefore only a few control signals are required for operation. That is, the production cost of such a control device is low. Such control devices have also proven to fail less. In addition to this, such a control device makes it possible to use simple and therefore cost-effective stepping motors.

Claims (3)

1. Device for forming leno selvedges in a weaving machine with heald frames, comprising an electric motor with a rotor having two guide elements for the leno warp, wherein the electric motor is controllable by means of a control device, characterized in that: the control device of the electric motor provides a starting pulse at the moment when the weaving machine starts opening the shed or when the shed starts closing.

2. Device for forming leno selvedges in a weaving machine with heald frames, comprising an electric motor with a rotor having two guide elements for the leno warp, wherein the electric motor is controllable by means of a control device, characterized in that: at the moment when the weft thread starts to be inserted or the weft insertion ends, the control device of the motor provides a starting pulse.

3. The apparatus of claim 1 or claim 2, wherein: the speed of rotation at which the shed is opened and closed by the motor rotor is higher than the speed at which the shed is opened and closed by the heald frame.