Procedures for head preparation

Abstract

A method for preparing the bobbin for the rewinding process by positioning a thread end at a predetermined detection position on the bobbin, comprising the steps of: - sucking the thread end towards a cutting device by means of a suction device providing suction air, - detecting the thread end at the cutting device by means of a thread sensor, - shutting off the suction air by means of a shut-off device and / or setting a thread brake on the bobbin, - cutting the thread end to length and - depositing the thread end at the detection position, characterized in that, before the thread end is sucked in, the thread brake (3) is moved into a holding position blocking the thread unwinding from the bobbin (2) and that, with or after the provision of the suction air until the thread end is detected by the thread sensor (6), the thread brake (3) is briefly moved once or several times into an unwinding position releasing the thread unwinding.

Description

The invention relates to a method for preparing the bobbin for the rewinding process by arranging a thread end at a predetermined detection position on the bobbin, comprising the steps of: - sucking the thread end towards a cutting device by means of a suction device providing suction air, - detecting the thread end at the cutting device by means of a thread sensor, - shutting off the suction air by means of a shut-off device, - cutting the thread end to length and - depositing the thread end at the detection position. Spinning heads produced on ring spinning machines are typically rewound into large-volume cross-wound bobbins on winding machines for further processing. This requires both an upper thread retrieved from the cross-wound bobbin and a lower thread coming from the feeder bobbin at each winding station. When a feeder bobbin is changed, the winding station's computer activates an automatic thread joining mechanism specific to that station. However, for primarily technological reasons, the spinning heads have a yarn end rest that cannot usually be handled at the winding stations of a winding machine without special preparation. Therefore, on their way from the spinning station to the winding station, the spinning heads are first fed into appropriate preparation devices where the yarn end is released and prepared for the subsequent winding process. This preparation of the yarn end is achieved, for example, by placing a yarn end, previously unwound and cut to length, at a predetermined position on the spinning head. A bobbin preparation device for a winding machine is disclosed, for example, in DE 196 50 934 B4. The bobbin to be prepared is positioned on a suction device next to a suction tube, which has a slot on the side facing the bobbin for drawing in and picking up the yarn until it is laid down on the tip of the bobbin. To assist in gripping the yarn end, the bobbin is rotated opposite to the winding direction. A shut-off device for switching the suction air on and off is arranged in the suction tube. This shut-off device is coupled to an orifice by means of which the strength of the suction air can be regulated. Thus, the strength of the suction air can be set differently for different batches, for example, or selected to be lower for hairy, fine yarns than for smooth and coarse yarns. It is also known that the suction device for drawing in the thread is arranged not beside, but above the spinning head. To prevent excessive / uncontrolled thread extraction, the suction device further includes a sensor that detects successful thread pickup. Once the thread is detected in the suction device, a thread brake on the spinning head is engaged to prevent further thread pull-off. In principle, it is known to suction the thread end from the cop using a suction nozzle, to detect its presence using sensors, to then cut the thread to length by separating off too much thread length, and then to position the cut thread end at a detection position, e.g. inside the cop or at the cop tip, where it can be easily detected again at the winding point. However, known methods for preparing the heads have the disadvantage that the relatively uncontrolled thread suction results in a very high amount of thread drop when the thread end is cut to length. The use of a thread brake that swings into position at the heads after a sensor detects the thread end has not yielded satisfactory results, as the suction flow due to the thread end's pull-off speed still leads to a high amount of thread drop. Based on this, the invention aims to provide a method for head preparation that ensures very little thread waste when cutting the thread end to length. The invention solves the problem by means of a method for head preparation with the features of claim 1. Advantageous further developments of the method are specified in the dependent claims. A characteristic feature of the inventive method for preparing the cop for the rewinding process is that, before the thread end is sucked from the cop, a thread brake is adjusted to a holding position that blocks the thread from the cop, and that the thread brake is briefly adjusted once or several times to a release position that allows the thread to unwind, either once or several times, with or after the provision of the suction air until the thread end is detected by the thread sensor. In contrast to methods known from the prior art, the thread brake is positioned against the head before the thread end is suctioned in such a way that, whether the suction air is applied simultaneously or subsequently, the thread end remains attached to the head by the thread brake. The thread end is moved towards the cutting unit by the suction device by briefly shifting the thread brake into a discharge position that allows the thread to unwind. The thread length that is pulled off the head can be determined independently of the suction air by the duration the thread brake remains in the discharge position. This is achieved through a brief, possibly...Intermittent adjustment of the thread brake to the unwind position can thus be achieved so that the thread end is gradually fed to the cutting device piece by piece, whereby only a short adjustment to the unwind position ensures that only a small thread is unwound at a time, so that in the event of detection of the thread end only a short thread section is cut off by the cutting device and the overall thread waste can be kept very low. Following the cutting of the thread to length, it is placed at the bobbin at the picking position, where it can then be easily picked up by a rewinding machine. The picking position can be any point on the bobbin, although the thread end is preferably placed inside the hollow bobbin body or at the bobbin tip. Essential to the method according to the invention is that the thread brake is positioned against the thread brake in such a way that the thread end is blocked before the suction air is supplied. To carry out the method according to the invention, the thread brake is repeatedly and briefly lifted from the head to release the thread end after or simultaneously with the supply of suction air. Adjusting the thread brake simultaneously with the supply of suction air has proven to be particularly energy-efficient. By gradually adjusting the thread end towards the cutting unit until it is detected by a thread sensor, with only a small amount of thread being pulled away from the head each time, minimal thread waste is ensured after detection and subsequent cutting. The suction air provided by the suction device is used to adjust the thread end towards the cutting unit. According to an advantageous embodiment of the invention, in addition to the suction air, the thread end is moved towards the cutting unit by means of blowing air supplied by a blowing device. The blowing device can, for example, be oriented such that it directs the blowing air through the hollow cop body or laterally past the cop, thus moving the thread end towards the cutting unit in addition to the suction device. The use of a blowing device ensures, to a particularly high degree, that the thread end is detached from the cop during cop preparation and reliably transported to the cutting unit. After the thread end is detected by the thread sensor, the supplied blowing air is deactivated, analogous to the shut-off of the suction air by the shut-off device, so that the cut thread end can be returned to the cop.Following further training, the direction of action of the blowing device is reversed, so that the thread end is then guided through the suction blowing device into the hollow body of the head. The length of thread unwound from the head is determined by the duration the thread brake remains in the unwind position. Only briefly moving the thread brake from the holding position to the unwind position ensures that only a short length of thread is unwound from the head and moved towards the cutting unit. This guarantees that if the thread end is detected by the thread sensor, only a very short length of thread is cut. According to a particularly advantageous embodiment of the invention, the thread brake is moved from the holding position to the unwind position for 1 ms to 100 ms, preferably 3 ms to 60 ms, and most preferably 5 ms to 30 ms. The ability to variably adjust the dwell time of the thread brake in the unwind position allows the process to be optimally adapted to the respective thread types and cop types. A brief movement of the thread brake to the unwind position in the range of 1 to 5 ms ensures a particularly low thread drop. If necessary, however, the process can be accelerated by extending the duration of the unwind position, thereby reducing the number of unwind positions the thread brake has to assume. This allows prepared cops to be made available more quickly, potentially with only a slightly higher thread drop.The possibility of varying the dwell time of the thread brake in the unwind position thus increases the flexibility of the process in a complementary way. In a simple embodiment, the dwell time of the thread brake in the unwind position is set via suitable means operated by the user, allowing the dwell time to be determined. However, according to a particularly advantageous embodiment of the invention, the dwell time of the thread brake in the unwind position is determined by a control unit coupled to the thread brake, which records the number of unwind positions of the thread brake until the thread end is detected at the cutting device. The use of a control unit that offers the possibility of recording the number of unwind positions of the thread brake until the thread end is detected by the thread sensor makes it possible, if necessary, to extend the dwell time of the thread brake in the unwind position, thereby achieving process optimization. For example,In the event that the control unit detects a high number of thread brake positions before the thread end is detected at the cutting unit, the control unit can increase the dwell time of the thread brake in the discharge position. This reduces the process time while simultaneously minimizing thread drop. Monitoring is performed by continuously recording the decreasing number of thread brake dwell positions, allowing for easy process optimization. The user is free to select the dwell time of the thread brake in the discharge position, enabling optimal adaptation of the process to specific conditions. In principle, the dwell time can be set manually, particularly taking into account the number of thread brake positions detected by the control unit (according to an advantageous further development) until the thread end is detected at the cutting device. However, according to a particularly advantageous embodiment of the invention, the control unit automatically and stepwise changes the dwell time of the thread brake in the discharge position, starting from a predetermined duration, in a process optimization process to reduce the number of thread brake discharge positions until the thread end is detected. According to this embodiment of the invention, the control unit automatically performs process optimization, in which it stepwise adjusts or optimizes the dwell time of the thread brake until a user-defined number of thread brake discharge positions is reached.During the preparation process, the control unit continuously adjusts the dwell time after each processed cop. To ensure optimal results with minimal thread waste, the control unit starts the cop preparation with the first cop to be processed, holding the thread brake in the unwind position for a predetermined duration. The control unit then adjusts the dwell time incrementally from cop to cop. According to a particularly advantageous embodiment of the invention, the control unit repeats this process optimization procedure after a change in cop type and / or thread type on the cop. Repetition in this context means that the process optimization procedure is restarted with a predetermined duration after the cop type or thread type on the cop has been changed, which may result in different processing times.This embodiment of the invention ensures that adjustments are automatically made for different thread and cop types, so that even when changing the cop type or thread type, only minimal thread waste can be guaranteed during cop preparation. To optimize the preparation process, a further embodiment of the invention allows for the thread end to be cut to length simultaneously with shutting off the suction air. This embodiment of the invention further optimizes and accelerates the process, for example, by coupling a shut-off valve that blocks the suction air with a cutting device, so that the thread end is cut to length at the same time as the suction air is shut off. An embodiment of the invention is explained below with reference to the drawing. In the drawing, Fig. 1 shows a schematic perspective view of a head preparation device. Fig. 1 shows a schematic representation of a bobbin preparation device 1 in which bobbins 2 provided with a thread are prepared for a rewinding process, wherein a thread not shown here, arranged on the bobbin 2, is moved with its thread end via a suction device 5 in the direction of a cutting and shut-off device 4. Before the suction air of the suction device 5 is activated, a thread brake 3 is brought into contact with the cop 2 in such a way that the thread end arranged on the cop 2 is blocked by the thread brake 3 despite the presence of the suction air. After the suction air is supplied, or simultaneously with it, the thread brake 3 is briefly moved by the cop 2 from the holding position that blocks the thread unwinding to a position that releases the thread unwinding. During the time the thread brake 3 remains in the unwinding position, the thread end is moved towards the cutting and shut-off device 4, the length of the unwound thread depending on the duration the thread brake 3 remains in the unwinding position. Intermittent adjustment of the thread brake 3 to the holding position, with a dwell time of only one to a few milliseconds, prevents an excessively long thread end from being pulled off the head 2. Intermittent, short-term adjustment of the thread brake 3 to the unwinding position results in the thread being moved incrementally towards the cutting and shut-off device 4 until its position is detected by the thread sensor 6. Following this, the cutting and shut-off device 4 simultaneously shuts off the suction air and cuts the thread end to a defined length, allowing the defined thread end to be moved into a receiving position on the cop 2, preferably inside the hollow cop 2. A partial unwinding of the thread end from the cop 2, achieved by only briefly adjusting the thread brake 3 into the unwinding position, prevents excessive thread drop during cutting. After the cop 2 has been prepared, a transport device 8 carrying the cop 2 moves it towards, for example, a rewinding machine. The dwell time of the thread brake 3 in the unwind position shown in Fig. 1 can be adjusted via a control device (not shown here). As part of a process optimization procedure, the control device adjusts the dwell time for each cop 2 to be processed, up to an optimal, predetermined value. Subsequently, identical cops 2 are prepared using a process optimized by the control device. A change in the cop type or the yarn type arranged on the cop 2 causes the control unit to restart the process optimization process, starting with a minimum dwell time of the yarn brake 3 in the unwind position and successively increasing this dwell time from cop 2 to cop 2 to be processed until a predetermined value is reached, which represents an optimum between process duration and yarn drop. Reference symbol list 1 Head preparation device 2 Head 3 Thread brake 4 Cutting and shut-off device 5 Suction device 6 Thread sensor 7 Bellows 8 Transport device

Claims

Method for preparing the cop for the rewinding process by positioning a thread end at a predetermined detection position on the cop, comprising the steps of: - sucking the thread end towards a cutting device by means of a suction device providing suction air, - detecting the thread end at the cutting device by means of a thread sensor, - shutting off the suction air by means of a shut-off device and / or setting a thread brake on the cop, - cutting the thread end to length and - depositing the thread end at the detection position, characterized in that, before the thread end is sucked in, the thread brake (3) is moved into a holding position blocking the thread unwinding from the cop (2) and that, with or after the provision of the suction air until the thread end is detected by the thread sensor (6), the thread brake (3) is briefly moved once or several times into an unwinding position releasing the thread unwinding. Method according to claim 1, characterized in that the thread end is adjusted towards the cutting device (4) by means of a blowing air provided by a blowing device. Method according to claim 1 or 2, characterized in that the thread brake (3) is moved from the holding position to the unwinding position for 1 ms to 100 ms, preferably 3 ms to 60 ms, particularly preferably 5 ms to 30 ms. Method according to one or more of the preceding claims, characterized in that the dwell time of the thread brake (3) in the unwind position is set by a control device coupled to the thread brake (3), which records the number of unwind positions of the thread brake (3) until the thread end is detected at the cutting device (4). Method according to one or more of the preceding claims, characterized in that the control device in a process optimization process to reduce the number of unwinding positions of the thread brake (3) until the thread end is detected, gradually changes the dwell time of the thread brake (3) in the unwinding position starting from a predetermined duration. Method according to one or more of the preceding claims, characterized in that the control device of the process optimization process repeats after a change of the cop type and / or the thread type arranged on the cop (2). Method according to one or more of the preceding claims, characterized in that the thread end is cut off simultaneously with the shut-off of the suction air.

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