GB2065725A

GB2065725A - Producing bobbins

Info

Publication number: GB2065725A
Application number: GB8037961A
Authority: GB
Original assignee: Zellweger Uster AG
Current assignee: Zellweger Uster AG
Priority date: 1979-12-17
Filing date: 1980-11-26
Publication date: 1981-07-01
Also published as: CH641504A5; IT8050040A0; CS227663B2; JPS56103065A; IT1127907B; GB2065725B; DE3030504C2; DE3030504A1

Abstract

Cross-wound bobbins each of which has at least approximately the same length of yarn are produced on a rotor spinning frame 1 with an automatic doffing device 2. The rotor spinning frame 1 has a length measuring device 5, preferably a pulse counter, which produces values corresponding to the length of yarn on each cross-wound bobbin. These values are stored in a calculator unit 4. Immediately before reaching the desired length on a bobbin, the doffing device 2 is caused by a signal from the calculator unit 4 to move to the relevant cross-wound bobbin and where it waits until another signal from the unit 4. This other signal indicates the desired yarn length and initiates the doffing of the fully wound cross-wound bobbin. <IMAGE>

Description

SPECIFICATION Production of yarn bobbins This invention relates to the production of yarn bobbins having a pre-determined yarn length on rotor spinning frames with the automatic doffing of fully wound cross-wound bobbins.

Cross-wound bobbins as directly produced, for example, by rotor spinning frames are used as, among other things, a supply for the so-called warp process. This term is understood to mean the formation of warp beams, such as are inserted into the looms. In this process, a plurality of crosswound bobbins are creeled in a frame, the warping creel, and the yarns are wound on the so-called warp beam via suitable guide devices. All crosswound bobbins are fully wound at the start of warping, and during warping, respectively the same yarn length of each cross-wound bobbin is transferred to the warp beam. The warp process has to be interrupted each time there is a thread break. This is very disadvantageous when there are unwound many cross-wound bobbins having yarn lengths which are too short, because they then have to be joined up.On the other hand, cross-wound bobbins with yarn lengths which are too long have a large yarn remnant which can no longer be directly further used; all these bobbins have to be replaced. The unused quantities of the yarn remaining on these bobbins are either treated as waste or they may be further used if they are combined into a new cross-wound bobbin in an additional winding device. However, this not only causes an additional expense, but also produces a second-grade yarn having a plurality of knots, since the end of each yarn remnant has to be joined to the start of the next yarn remnant.

An object of this invention is therefore to produce cross-wound bobbins which hold at least approximately a predetermined yarn length. A result of this is that during warping, all crosswound bobbins are empty at the right time, i.e.

that only insignificant yarn remnants remain on individual bobbins. The known determination of the yarn length by means of establishing the diameter of the cross-wound bobbin is not sufficiently precise.

Different ways are already known in connection with rotor spinning frames for measuring the wound yarn length very precisely during the formation of the cross-wound bobbins. In these known ways a signal is produced when a desired length of yarn on the cross-wound bobbins is reached. As a result of this signal, the sliver which is being fed to the individual spinning stations is interrupted so that a thread break is produced when a cross-wound bobbin has been wound with the desired length of yarn. A new spinning operation subsequently takes place in a known manner in the rotor. The operation is relatively complex.

Rotor spinning frames have recently been used, in which it is possible to change the cross-wound bobbins in the rotor (so-called "doffing") without a thread break. Separating the two cross-wound bobbins takes place outside the rotor and the initiation of a thread break by an interruption in the feed controlled by the length measuring device is therefore undesirable.

Rotor spinning frames have also recently become known which comprise automatic crosswound bobbin changing devices (so-called doffers) as an additional device. These usually travel from one spinning station to another in turn.

However, they only function when there is no thread break. This feed must, therefore, not be interrupted by the length measuring device when the desired yarn length has been reached.

The present invention seeks to overcome these disadvantages and consists of a method of producing yarn bobbins having a pre-determined yarn length on rotor spinning frames with an automatic device for doffing fully wound crosswound bobbins, wherein the yarn being wound on a bobbin at a spinning station is measured by a length measuring device, each cross-wound bobbin being doffed under the control of the length measuring device when the yarn wound on the bobbin has at least approximately reached the desired length.

The invention also provides an apparatus for carrying out the method comprising a rotor spinning machine having a length measuring device and a device for doffing cross-wound bobbins, the doffing device being movable under the command of signals produced by the measuring device when the desired length of yarn on a bobbin has been reached to the location of that bobbin.

An embodiment of the invention will now be described with reference to the accompanying drawing the single figure of which is a schematic illustration of a rotor spinning frame. The frame 1 has a number of cross-wound bobbins 11, 12, 13 and 14. An automatic doffing device 2 is movable along the frame 1 in a path of travel 3. Thus, the travel of the doffing device 2 may be around the machine, or backwards and forwards along one side or along a revolving rail.

The rotor spinning frame 1 has a length measuring device of a known design. This measuring device substantially consists of a revolution counter 5, preferably a pulse counter, which co-operates with a transporting roller 6 for the spun yarn and releases a signal corresponding to a predetermined yarn length on reaching a predetermined number of revolutions. The signal pulses of a selected spinning station are counted during the time yarn is being spun at this particular spinning station.

In order to avoid the relatively high expense caused by providing each spinning station with a pulse counter, the yarn length may be determined by combining an individual pulse counter 5 with thread run stop motions 7. The number of revolutions of the transporting roller 6, released by the pulse counter 5 reproduces the yarn length for all spinning stations which have produced yarn without any interruption and have wound the yarn on the cross-wound bobbin. The thread run stop motions 7 establish which cross-wound bobbins have suffered interruptions in production during which time intervals. These cross-wound bobbins require more time corresponding to these time intervals, until they have received the same yarn length.

Counting the revolutions and releasing a signal is preferably effected in a calculator unit 4 which is common to all spinning stations. The number of revolutions or the individual yarn lengths at the spinning stations are stored and processed in the unit 4, which commands the doffing device 2 to move towards a spinning station where the crosswound bobbin has reached the desired length and is to be doffed.

The unit 4 is preferably programmed so that it initially releases a warning signal when the crosswound bobbin has not quite reached the predetermined length at a spinning station, i.e.

there is still at least one time interval until the complete yarn length is reached, which interval is required by the doffing device as travelling time from the most remote starting position to the relevant spinning station. As soon as the doffing device has arrived at the cross-wound bobbin which is to be exchanged, it remains in this position until the length measuring device reports to the calculator unit 4 that the predetermined final length has been reached and the unit 4 sends a release signal to the doffing device. This release signal causes the fully wound cross-wound bobbin to be ejected from the spinning station, whereupon a new and empty bobbin tube is creeled and the yarn is joined thereto. The fully wound cross-wound bobbin is thus positioned on a transport device and is conveyed thereon to a collecting container.As soon as these steps of the bobbin change have been completed, the doffing device is ready for processing further warning and release signals.

This manner of operating makes unnecessary any interruption in the spinning process, by stopping the fibre supply to the spinning unit, when the bobbin is being changed, because the separation of the yarn end of the fully-wound cross-bobbin from the start of the cross-wound bobbin which is just being spun is taken over by the doffing device.

The length measuring device may also only cover one part of the spinning stations. This possibility is significant, for example, when a doffing device is provided for each side of the frame.

The calculator unit 4 may also receive the signals for the length measurements from transmitters other than from counting the revolutions of a transporting roller, depending on the system which is used for the length measurement.

Claims

1. A method of producing yarn bobbins having a predetermined yarn length on rotor spinning frames with an automatic device for doffing fully wound cross-wound bobbins, wherein the yarn being wound on a bobbin at a spinning station is measured by a length measuring device, each cross-wound bobbin being doffed under the control of the length measuring device when the yarn wound on the bobbin has at least approximately reached the desired length.

2. A method according to claim 1, wherein values corresponding to the yarn length at each spinning station which are ascertained by the length measuring device are continuously stored in a calculating unit and compared with a desired value, and wherein before this desired value is reached at one of the spinning stations, a doffing device is commanded to travel to the location of the said spinning station, and to commence the doffing operation when the yarn on the bobbin has reached the desired length.

3. A method according to claims 1 and 2, wherein the spinning process is continued without interruption during the doffing operation, the yarn on a fully wound cross-wound bobbin being separated by the doffing device from the yarn which is subsequently supplied.

4. A method according to claims 1 to 3, wherein the same yarn length is registered for all spinning stations by a revolution counter associated with a transporting roller 6 and the actual yarn length is established for each individual spinning station by thread run stop motion based on the standstill times established by these thread run stop motions.

5. An apparatus for carrying out the method according to claim 1, comprising a rotor spinning machine having a length measuring device and a device for doffing cross-wound bobbins, the doffing device being movable under the command of signals produced by the measuring device when the desired length of yarn on a bobbin has been reached to the location of that bobbin.

6. An apparatus according to claim 5, wherein the doffing device is caused to move to the bobbin changing location by a signal from a calculator unit and is caused to doff the bobbin by another signal released when the bobbin has reached the pre-determined yarn length.

7. An apparatus according to claims 5 and 6, wherein the length measuring device comprises a revolution counter co-operating with a transporting roller.

8. An apparatus according to claim 7, wherein the revolution counter is a pulse counter adapted to measure the yarn length reached theoretically for all spinning stations and the individual yarn lengths at each spinning station being determined by thread run stop motions.

9. An apparatus according to claim 8, wherein the thread run stop motions which are associated with each spinning station are operable continuously to release thread run signals to the calculator unit.

10. An apparatus for producing yarn bobbins having a predetermined yarn length substantially as described with reference to the accompanying drawings.