Constant Joining Material in Air Vortex Spinning Methods
The present application relates to a method for operating a drafting arrangement (1) for drafting a fibre composite (2). For this purpose, the drafting arrangement (1) has at least one front pair of rollers (3) and one rear pair of rollers (4) having a nip line (5), a fibre composite end (6) being present for operating the drafting arrangement (1). According to the invention, when the drafting arrangement (1) is put into operation, the fibre composite end (6) enters the nip line (5) of the rear pair of rollers (4) only when the build-up arising from acceleration has ended in the rotational speed profile of the front pair of rollers (3) and in the rotational speed profile of the rear pair of rollers (4).
The present invention relates to a method for operating a drafting arrangement, according to the precharacterizing clause of the independent Patent Claims 1 and 2, to a control for drafting arrangements of a textile machine, according to the precharacterizing clause of Patent Claim 12, and to a textile machine having a said control, according to Patent Claim 13.
PRIOR ARTMethods for operating drafting arrangements are known in textile technology. The publications EP 121 97 37, EP 807 700 and EP 137 57 09 describe methods of this type. However, as is evident from the publications mentioned, the present invention is suitable particularly for the operation of drafting arrangements which belong to air-spinning machines. In air-spinning machines, a fibre composite is spun into a yarn by means of one of more airflows.
The known methods for operating a drafting arrangement, however, have disadvantages. This applies particularly to drafting arrangements which belong to air-spinning machines or to drafting arrangements which transfer the drafted fibre composite to a spinning unit operating according to an air-spinning method. The disadvantage of the known methods for operating a drafting arrangement is that the piecer quality is not always satisfactory. The term “piecer” is understood to mean a “seam”, within a yarn, at which the yarn has been “pieced up” or “hung up” again, for example after an interruption in production. Normally, a piecer is produced by spinning further fibres at or around an existing yarn end. The piecer constitutes an actual overlap region between a yarn end and new fibres additionally spun on this. It therefore often forms a thick place which is actually undesirable. Ideally, a piecer or a piecing point should not differ from the remaining yarn, this applying particularly to strength and fibre mass. In an endeavour to achieve this ideal state, various possibilities are disclosed in the abovementioned publications. For example, the fibre end at which piecing is to take place may be narrowed and/or the drafting arrangement delivers fewer fibres in the overlap region than in the subsequent stationary operating state. Irrespective of this, however, in the known devices, there is a further problem which the present invention now intends to solve.
To be precise, it was found that, when a drafting arrangement is put into operation and therefore when the associated pairs of rollers are put into operation or accelerated, a build-up of the rotational speed profile to the corresponding piecing speed takes place. This build-up (overshoots and undershoots), which is caused by the run-up of the pairs of rollers from standstill to their corresponding piecing speed or piecing rotational speed (see
The object on which the invention is based is, therefore, to provide a method for operating a drafting arrangement for the drafting of a fibre composite, by means of which mass fluctuations in the piecer are avoided or minimized. An object which may also be considered is to provide a method for operating a drafting arrangement, in which a fibre composite is to be drafted from the outset with the correct draft ratio.
This or these objects is or are achieved by means of the features in the independent Patent Claims 1 and 2.
The advantageous effect of the method according to the invention is now explained below with reference to
When the drafting arrangement 1 is then put into operation again, first, as a rule, the rear pair of rollers 4 commences to rotate before the front pair of rollers 3 itself resumes operation. It may well be that the period of time between the operation of the rear pair of rollers 4 and that of the front pair of rollers 3 is sufficient to ensure that, in the rotational speed profile of the pair of rollers 4, the build-up arising from acceleration is terminated before the front pair of rollers 3 is set in motion. However, since the fibre composite end 6 is located directly in front of the nip line 5 of the rear pair of rollers 4, a drafting of the fibre composite 2 takes place immediately after the front pair of rollers 3 has been put into operation. Since, after being put into operation, the front pair of rollers 3 still has to accelerate to the piecing speed or operating speed, a build-up to the desired piecing rotational speed also takes place here. As a result, that region of the fibre composite 2 which directly follows the fibre composite end 6 is drafted in a fluctuating manner and consequently has undesirable mass fluctuations. If this “initial region” of the fibre composite 2 is used to produce a piecer, then, of course, this piecer, too, has undesirable mass fluctuations.
That these mass fluctuations occur can also be seen very clearly from
So that no mass fluctuations occur as a result of the said effects in the initial region of the drafted fibre composite when a drafting arrangement is put into operation, according to the invention the fibre composite end (that is to say, the foremost tip of the fibre composite) is supplied to the nip line of the second pair of rollers only when both pairs of rollers have ended their corresponding build-ups arising from acceleration. This time point is designated by tEVE in
There are various advantageous refinements and embodiments of the method according to the invention which are to be found in the dependent claims.
The invention and the idea of the invention or its implementation are explained below with reference to further figures. It is to be pointed out expressly, however, that the invention or the idea of the invention is not restricted to the embodiments shown in the figures and examples.
Depending on how the drafting arrangement has previously been stopped, the method according to the invention may also include moving the fibre composite end 6 back from the nip line 5 of the rear pair of rollers 4 before the drafting arrangement is put into operation. This may also take place automatically, for example by means of the control 19 and the drive 17. This applies particularly when the fibre composite end 6 is not separated from the nip line 5 of the rear pair of rollers 4 at a predetermined distance by hand. This is desirable, above all, in fully automatic piecing methods and devices, in which the drafting arrangement is first stopped so that the fibre composite 2 breaks away at the nip line 5 of the rear pair of rollers 4. To be precise, in this case, a clearly defined fibre composite end 6 is obtained, which merely has to be positioned appropriately before the drafting arrangement can be put into operation again.
The invention is not restricted to the possibilities and the embodiments explicitly mentioned. On the contrary, these variants are intended as suggestions for a person skilled in the art in order to implement the idea of the invention as beneficially as possible. Further advantageous uses and combinations which likewise reproduce the idea of the invention and are to be protected by this application can therefore easily be derived from the embodiments described. Some of the disclosed features have been described in combination in this description and are claimed in combination in the following claims. It is also conceivable, however, to claim individual features of this description in themselves or in another combination in application of the idea of the invention. The applicant therefore expressly reserves the right, in any event, to provide other combinations in application of the idea of the invention.
KEY
- 1 Drafting arrangement
- 2 Fibre composite
- 3 Front pair of rollers
- 4 Rear pair of rollers
- 5 Nip line
- 6 Fibre composite end
- 7 Pair of rollers
- 8 Main drafting zone
- 9 Predrafting zone
- 10 Yarn end
- 11 Drafted fibre composite
- 12 Spinning unit
- 13 Yarn
- 14 Vortex chamber
- 15 Spindle
- 16 Rollers of the rear pair of rollers
- 17 Drive predraft
- 18 Drive rear pair of rollers
- 19 Control
- 20 Apron
- U4(t) Rotational speed profile of rear pair of rollers 4
- U3(t) Rotational speed profile of front pair of rollers 3
- UA,4 Piecing rotational speed for the rear pair of rollers 4
- UA,3 Piecing rotational speed for the front pair of rollers 3
- ts,3 Time point for operating the front pair of rollers 3
- th,3 Period of time until the front pair of rollers 3 reaches the piecing rotational speed UA,3 (acceleration)
- th,4 Period of time until the rear pair of rollers 4 reaches the piecing rotational speed UA,4 (acceleration)
- tEV,3 Period of time until the front pair of rollers 3 has ended the build-up arising from acceleration
- tEV,4 Period of time until the rear pair of rollers 4 has ended the build-up arising from acceleration
- tK Time point commencement of piecing action
- tE Time point end of piecing action
- tAE Period of time piecing action
- tEVE Time point in which both pairs of rollers have ended the build-up
- UB,4 Operating rotational speed of the rear pair of rollers 4
- UB,3 Operating rotational speed of the front pair of rollers 3.
Claims
1. Method for operating a drafting arrangement (1) for drafting a fibre composite (2), the drafting arrangement (1) containing a front pair of rollers (3) and a rear pair of rollers (4) having a nip line (5), and a fibre composite end (6) being present for starting up the drafting arrangement (1), characterized in that, before the drafting arrangement (1) is put into operation, the fibre composite end (6) is brought to a predetermined distance from the nip line (5) of the rear pair of rollers (4), this distance preferably amounts to up to 6 mm, this distance preferably amounts to 0.1 mm to 5 mm, this distance particularly preferably amounts to 3 mm or 4 mm, and the bringing to a distance is preferably carried out by the fibre composite end (6) being cut to length.
2-13. (canceled)
Type: Application
Filed: Jan 28, 2005
Publication Date: Oct 11, 2007
Inventors: Horst Wolf (Holzheim), Michael Bergmann (Deggingen-Reichenbach), Oliver Straub (Eislingen/Fils)
Application Number: 10/587,916
International Classification: D01H 5/00 (20060101);