Textile machine with variable tension draft

Abstract

A textile machine, especially a spinning preparation machine, with a drafting system for drafting a fiber strand fed to the textile machine, includes a compressor arranged downstream from the drafting system in a transportation direction of the fiber strand for compressing the fiber strand. A draw-off device is arranged downstream from the compressor for drawing off the drafted fiber strand. At least one entrance cylinder is provided that can be powered by a drive and one exit cylinder that can be powered by a drive. The draw-off device comprises at least one draw-off disk that can be powered by a drive. Means are provided to the textile machine to change the ratio of the circumferential speeds of the exit cylinder and the draw-off disk (=tension draft (A)) while the drafting system is operated, at least during a part of its starting phase and/or its stopping phase.

Claims

1. A textile machine for a spinning preparation machine, the textile machine comprising: a drafting system configured to draft a fiber strand fed to the textile machine, the drafting system further comprising an entrance cylinder powered by a drive, and an exit cylinder powered by a drive; a compressor arranged downstream from the drafting system in a transportation direction of the fiber strand that compresses the fiber strand; a draw-off device arranged downstream from the compressor that draws off the drafted fiber strand, the draw-off device further comprising a draw-off disk powered by a drive; means for changing a ratio of circumferential speeds of the exit cylinder and the draw-off disk (tension draft) while the drafting system is operated during one or both of a part of a starting phase and a stopping phase of the drafting system; and, a control unit that is configured with the means for changing a ratio of circumferential speed of the exit cylinder and draw-off disk to, at least during a part of the starting phase or the stopping phase of the drafting system, increase the circumferential speed of the draw-off disk faster or slower than the circumferential speed of the exit cylinder, or to reduce the circumferential speed of the draw-off disk faster or slower than the circumferential speed of the exit cylinder.

2. The textile machine according to claim 1, wherein the drive for the draw-off disk and the drive for the exit cylinder are individual respective drives.

3. The textile machine according to claim 1, further comprising means for changing a ratio of circumferential speeds of the entrance cylinder and the exit cylinder (drafting system's draft) while the drafting system is operated during one or both of the starting phase and the stopping phase of the drafting system depending on the change of the tension draft.

4. The textile machine according to claim 3, wherein the drafting system further comprises a middle cylinder powered by a drive, and further comprising means for changing a ratio of circumferential speeds of the middle cylinder and the exit cylinder (main draft) while the drafting system is operated during one or both of the starting phase and stopping phase of the drafting system depending on the change of the tension draft.

5. The textile machine according to claim 4, wherein the drafting system further comprises a middle cylinder powered by a drive, and further comprising means for changing a ratio of circumferential speeds of the entrance cylinder and the middle cylinder (preliminary draft) while the drafting system is operated during one or both of the starting phase and the stopping phase of the drafting system depending on the change of the tension draft.

6. The textile machine according to claim 5, wherein the tension draft, the preliminary draft, the main draft, the drafting system's draft, and an overall draft (ratio of circumferential speeds of the entrance cylinder and the draw-off disk), are changed by changing the circumferential speeds of the entrance cylinder, the middle cylinder, the exit cylinder, and the draw-off disk with the control unit.

7. The textile machine according to claim 6, wherein the control unit is configured to change the tension draft during one or both of the starting phase and the stopping phase of the drafting system in proportion to the change of the circumferential speed of the exit cylinder.

8. The textile machine according to claim 6, wherein the control unit is configured to change the tension draft during one or both of the starting phase and the stopping phase of the drafting system depending on the circumferential speed of the exit cylinder, wherein the change is based on a mathematical model and data from a data base of the textile machine containing characteristic parameters of the fiber strand.

9. The textile machine according to claim 6, wherein the control unit is configured to change the drafting system's draft during one or both of the starting phase and the stopping phase of the drafting system by changing the main draft depending on one or both of the circumferential speed of the exit cylinder and the circumferential speed of the draw-off disk.

10. The textile machine according to claim 6, wherein the control unit is configured to increase the drafting system's draft by changing the main draft during one or both of the starting phase and the stopping phase of the drafting system and, at the same time, to reduce the tension draft or to reduce the drafting system's draft while increasing the tension draft.

11. The textile machine according to claim 6, wherein the control unit is designed to regulate the tension draft and the drafting system's draft by changing the main draft during one or both of the starting phase and the stopping phase of the drafting system such that the overall draft deviates by no more than 5% from a target value preset for the normal operation of the drafting system.

12. A method for operating a textile machine, wherein the textile machine comprises: a drafting system configured to draft a fiber strand fed to the textile machine, the drafting system further comprising an entrance cylinder powered by a drive, and an exit cylinder powered by a drive; a compressor arranged downstream from the drafting system in a transportation direction of the fiber strand that compresses the fiber strand; a draw-off device arranged downstream from the compressor that draws off the drafted fiber strand, the draw-off device further comprising a draw-off disk powered by a drive; the method comprising changing a ratio of circumferential speeds of the exit cylinder and the draw-off disk (tension draft) while the drafting system is operated during one or both of a part of a starting phase and a stopping phase of the drafting system and changing the drafting system's draft by changing a main draft such that an overall draft during one or both of a part of a starting phase and a stopping phase of the drafting system deviates by no more than 5% from a target value preset for the normal operation of the drafting system.

13. The method according to claim 12, wherein the drafting system's draft is increased when the tension draft is reduced, or the drafting system's draft is reduced when the tension draft is increased during the starting phase and the stopping phase of the drafting system, respectively.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages of the invention are described in the embodiments below, which show:

(2) FIG. 1 is a schematic lateral view of a drawing frame,

(3) FIG. 2 is a partially cut view of a compressor during normal operation of a drafting system,

(4) FIG. 3 is a partially cut view of a compressor during the normal operation of a drafting system known from the state of the art during one of its starting or stopping phases,

(5) FIG. 4 is a schematic representation of individual parameters of a textile machine according to the invention,

(6) FIG. 5 is a schematic section of a textile machine according to the invention, and

(7) FIG. 6 is a schematic section of another textile machine according to the invention.

DETAILED DESCRIPTION

(8) Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

(9) FIG. 1 shows a lateral view schematically and, as an example of a textile machine 11 according to the invention, a drawing frame for drafting (homogenizing) a rope-shaped fiber strand 2. While the drawing frame is operating, the fiber strand 2 (e.g. in form of fiber slivers) is pulled out of one or several so-called spinning cans 16 with the help of a drawing-off arrangement and fed via corresponding deflections 18 to the respective drafting system 1 of the drawing frame (or, in the case of a multi-headed drawing frame, to the drafting systems 1 of the drawing frame).

(10) As a rule, the drafting system 1 consists of three or more roller pairs that in each case can comprise at least one lower roller and one upper roller. The desired draft of the fiber strand 2 is ultimately created because the individual cylindrical lower rollers, and with them, also the individual upper rollers making contact with them, have an increasingly higher circumferential speed in the transportation direction T of the fiber strand 2 shown. Although other solutions are also conceivable, the drafting system 1 in the embodiments shown has lower rollers shaped like an entrance cylinder 7, a middle cylinder 10, and an exit cylinder 8. The individual cylinders 7, 8, 10, in turn, make contact with one or several counter cylinders 12, so that the fiber strand 2 can be guided in a clamped way. The transportation direction increases the circumferential speeds of the above-mentioned cylinders 7, 8, 10, resulting ultimately in drafting and thus homogenizing the fiber strand 2.

(11) After the drafting system 1, the drafted fiber material (=fiber fleece 17) is finally guided through a compressor 4 preferably designed as fleece funnel, which compresses the fiber fleece 17.

(12) Afterwards, the fiber fleece 17 passes the compressor 4 and reaches the area of a draw-off device 5, which generally comprises several rotatable or at least partially driven draw-off elements, for example in form of two draw-off disks 9 making contact with the fiber fleece 17 from two sides. Owing to a correspondingly high transportation speed, the draw-off device 5 causes an additional draft and, with it, an increase in the tensile strength of the fiber fleece 17. Finally, the fiber fleece 17 is generally fed to a rotating turntable 15, which deposits it loop-like in a spinning can 16 made available.

(13) The basic path of the fiber fleece 17 or its fiber sections 21 during the operation of the drafting system is made clear in FIGS. 2 and 3.

(14) A lateral view of a partially cut compressor 4 is shown. In this example, it is shown as a fleece funnel that brings about a joining together of the fiber sections 21 of the fiber fleece coming from above in FIGS. 2 and 3. Here, the fiber fleece 17 ultimately leaves the compressor 4 through a corresponding passage opening 13.

(15) As can be seen in FIG. 2, which shows schematically the path of the fiber sections 21 of the fiber fleece 17 during normal operation of the drafting system 1, the fiber sections 21 reach the compressor 4 along more or less parallel paths and finally strike its floor area 22 (the compressor 4 is for this reason often named striking funnel). Thus, the fiber sections 21 of the fiber fleece 17 come out of the clamping zone of the exit cylinder 8 and its counter cylinder 12 with high speed and strike the floor area 22 (i.e. the swirling zone) of the compressor 4 without significant change of direction. Owing to the ensuing reversal of direction and the further transportation towards the passage opening 13, the fiber sections 21 from the edge area of the fiber fleece 17 cover a significantly longer distance than the fiber sections 21 from the middle area of the fiber fleece 17. When the fiber sections 21 strike, they are therefore swirled among one another. The result is a fiber fleece 17 with a desired additional tensile strength, known generally as sliver adhesion.

(16) However, the path of the fiber sections 21 of the fiber fleece 17 shown in FIG. 2 results only during normal operation 016 (FIG. 4) of the drafting system 1, i.e. during the phase lying between its starting and stopping phases I, III (differing, among other things, by a slower feeding speed L of the drafting system 1, i.e. having a slower circumferential speed of the exit cylinder 8 from normal operation II).

(17) Comparing FIGS. 2 (normal operation II) and 3 (starting or stopping phase I, III), the fiber sections 21 of the fiber fleece 17 no longer enter the compressor 4 in parallel paths during the starting and stopping phase I, III (FIG. 2). Rather, a funnel-shaped movement pattern occurs, explained by the lower speed of the individual fiber sections 21 in the time windows mentioned above (once again resulting from the slower circumferential speed of the exit cylinder 8). Here, the fiber sections 21 from the edge area of the drafting system 1 do not move straight on the floor area 22 towards the compressor 4, but are more likely to be taken along by the adjacent fiber sections 21 and therefore take a path that turns out to be shorter than the one that they would have traveled during normal operation II. As a result of this, the fiber sections 21 are ultimately guided more uniformly and less swirled than in normal operation II of the drafting system 1. This finally leads to the production of a fiber fleece 17 with considerably less sliver adhesion owing to the absence of swirling.

(18) To counteract this disadvantage, this invention now suggests changing the ratio of the circumferential speeds of exit cylinder 8 and draw-off disk 9 (=tension draft A) during the operation of the drafting system 1, at least during part of its starting and/or stopping phase I, III. In this way it is possible, as shown in the following, to avoid the flow pattern shown in FIG. 3 during the starting and stopping phase I, III. Rather, a flow pattern as similar as possible to the one shown in FIG. 2 results from the method according to the invention or with the help of the textile machine 11 according to the invention, also during the above-mentioned phases outside of normal operation II.

(19) In this connection, an increase in the tension draft A (FIG. 4) during the starting phase I from an initial value to a final value is provided, and this corresponds to the value desired during normal operation II of the drafting system 1 (here, the tension draft A is increased preferably by increasing the circumferential speed of the draw-off disk 9 faster than the circumferential speed of the exit cylinder 8). Since the tension draft A is defined as the ratio of the circumferential speeds of exit cylinder 8 and draw-off disk 9, a lower tension draft A means a slower drawing off of the fiber fleece 17 from the compressor 4. The fiber fleece 17 is thus quasi compressed inside the compressor 4, so that the flow pattern shown in FIG. 3 can be approximated to the one shown in FIG. 2. A possible connection between the circumferential speed of the exit cylinder 8, i.e. of the feeding speed L of the exit cylinder 8and with it, of the drafting system 1and the tension draft A during the starting phase I results from FIG. 4. Thus, an increase in the feeding speed L of the exit cylinder 8 and of the tension draft A can be provided until normal operation II is reached.

(20) It is ultimately just as conceivable to reduce the tension draft A during the stopping phase III together with the feeding speed L of the exit cylinder 8 (by reducing the circumferential speed of the draw-off disk 9 slower than the circumferential speed of the exit cylinder 8) in order to increase the above-mentioned sliver adhesion during the stopping phase III too.

(21) Generally, it must be pointed out with respect to FIG. 4 that it merely provides a schematic view of the course of the drafting system's draft S (or main draft H), tension draft A, feeding speed L of the exit cylinder 8 and overall draft G over time t. However, FIG. 4 contains no statements about the amounts of the respective changes. Likewise, the changes shown do not have to take place linearly, so that changes that follow a non-linear function are also conceivable.

(22) Another advantageous further development of the invention is also shown in FIG. 4. It is this an enormous advantage if during the starting phase I the drafting system's draft S (ratio of the circumferential speeds of entrance cylinder 7 and exit cylinder 8) is simultaneously reduced from an initial value to one desired during normal operation II. This can take place, for example, by gradually reducing the main draft H (=ratio of the circumferential speeds of middle cylinder 10 and exit cylinder 8) of the drafting system 1 under constant preliminary draft (=ratio of the circumferential speeds of entrance cylinder 7 and middle cylinder 10). Analogously, it is finally also conceivable to increase the drafting system's draft S during the stopping phase III too by increasing the main draft H, for example. In the final analysis, the change of the drafting system's draft S ensures that the overall draft G (=ratio of the circumferential speeds of entrance cylinder 7 and draw-off disk 9) of the textile machine 11 remains roughly constant throughout its operation (see curve G in FIG. 4).

(23) Finally, FIGS. 5 and 6 show possible embodiments of the textile machine 11 according to the invention.

(24) As these figures show, it is advantageous if the draw-off disks 9 (or at least one of preferably two draw-off disks 9) are powered with the help of a drive 6 executed as an individual drive. As a result of this, the tension draft A can be adjusted to each point in time by changing the rotational speed of the drive 6. To do this, the drive 6 should be connected preferably to a control unit 3 indicated in FIG. 1. It can furthermore be seen in FIGS. 5 and 6 that it can be advantageous if the rotational axes 14 (for clarity reasons, only one of the rotational axes generally identified with a cross is provided with a reference sign) of the draw-off disks 9 and/or the rotational axis 14 of the drive 6 powering the draw-off disk(s) 9 runs skewed with respect to at least one rotational axis 14 of the cylinders 7, 8, 10, 12 of the drafting system 1 mentioned above. For example, it is conceivable that the rotational axes 14 of the above-mentioned drive 6 and/or of the draw-off disks 9 run perpendicular to the rotational axes of cylinders 7, 8, 10, 12 of the drafting system 1 in the lateral view shown in FIG. 5.

(25) The end result is therefore to suggest a textile machine 11 or method for operating it in which the overall draft G remains roughly constant in spite of changing tension draft A, thus making a uniform draft of the fiber strand 2 possible with maximum optimal sliver adhesion possible. In order to also regulate the described main draft H or the drafting system's draft S mentioned above according to the present invention, the entrance cylinder 7, the middle cylinder 10 and/or the exit cylinder 8 can be provided with the respective individual drives, as indicated in FIG. 6, for example (here, the entrance cylinder 7 and the middle cylinder 10 are connected to a drive 6 executed as a twin shaft engine with a corresponding belt 20, so the preliminary draft is always constant).

(26) To conclude, reference is made to FIG. 5, which shows a sensor 19 placed after the draw-off disks 9. This sensor can, in turn, be connected to the above-mentioned control unit 3 and designed to detect the speed of the fiber fleece 17. Ultimately, the textile machine 11 has in this case a sensor 19 to determine the tension draft A at the exit of the drafting system 1 when the fiber strand speed is known.

(27) The present invention is not restricted to the embodiments shown and described. Variations within the scope of the patent claims are just as possible as a combination of characteristics, even if they are shown and described in different embodiments, in the patent claims or in the general description.