Textiles: fiber preparation – Working – Carding
Reexamination Certificate
1999-11-12
2001-04-24
Neas, Michael A. (Department: 3765)
Textiles: fiber preparation
Working
Carding
C019S113000, C019S114000
Reexamination Certificate
active
06219885
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns the carding process of textile fibres (in particular “short staple fibres” of a maximum fibre length of up to 60 mm).
STATE OF THE ART
A modern card comprises a so-called main drum (also called main cylinder) or two drums of large dimensions. This (or each) drum co-operates with a flat arrangement for performing the actual carding action. In order to maintain the material flow the drum (or the pair of drums, respectively) co-operates with a feed system (feed roll and licker-in, also called taker-in) and with a fibre take-off system. The feed system processes fibres normally supplied in batt form. The take-off system normally is laid out for forming a sliver. Each “working element” (drum, licker-in, take-off roll, flats) is provided with a so-called clothing which performs the actual processing of the fibres. Between the drum and its “cover” (be it in the form of a working element or in the form of an element with a covering function) a “working gap” is provided. The feed system is to be laid out for feeding fibres to be processed to the drum as evenly as possible over the full working width of the working elements, i.e. over the full width provided with clothing for processing fibres. The take-off system is laid out for collecting processed fibres as evenly as possible over this full width.
The main drum is the “heart” of the carding machine and fundamentally influences all of its functions. In particular the fibre stream is opened completely to the individual fibre and is cleaned thoroughly only after it has reached the main drum. Cleaning is effected by eliminating undesirable matter from the path of transport which is defined by the working gap at the circumference of the drum. “Undesirable” matter comprises e.g. dust, trash particles, neps that cannot be disentangled, and short fibres (unspinnable fly waste). The “selectivity” of the elimination process, however, is of decisive importance—the “desirable” material (good fibres) is to be first carried forward as completely as possible in the working gap and subsequently transferred to the subsequent working element for the formation of a sliver.
Today a conventional card is provided with a drum of a diameter of about 1000 to about 1300 mm, the working width being about 1000 mm.
“Small” cards have been proposed and applied in practical use. They were deemed unsatisfactory, however (see “High-Speed Carding and Continuous Card Feeding”, Dr. Zoltan S. Szaloki, page 87; Editor: Institute of Textile Technology, Charlottesville, Va., U.S.A.). Cards of this type (to the knowledge of the applicant) no longer are in practical use.
EP-A-446 796
A card of a new type has been described in EP-A-446 796. According to this earlier proposal a card for achieving higher precision is characterized in that the working width is limited in such a manner that it does not exceed 800 mm, and is in the range of e.g. 400 to 600 mm, and preferentially is reduced to below 400 mm. This proposal did not yield satisfactory results in practical application and no machines of this type were tested outside the laboratories. In a further step according to EP-A-446 796 it was proposed that the diameter of the drum, or of its working surface, respectively, be limited in such a manner that it does not exceed 800 mm and preferentially ranges between 350 and 450 mm. Notwithstanding the reduction in diameter this drum was meant to also co-operate directly with the feed system and the take-off system, i.e. the card comprised only one single drum. The card preferentially was laid out as a revolving flat card.
All elements influencing the working gap (e.g. the main drum and the flats) according to EP-A-446 796 preferentially were meant to be made from a material of high elastic modulus in order to reduce bending over the working width. According to EP-A-446 796 steel and fibre reinforced synthetic materials were indicated. The material chosen was to ensure the desired dimensional stability of the element (a corresponding manufacturing method being applied) and to maintain it during operation. Accordingly the material was supposed to show a low heat expansion coefficient and/or a higher heat conductivity in order to prevent the heat losses (which inevitably occur at high production rates) from causing disturbing deformations of the working elements.
EP-A-446 796 was based on the principle that the carding process was to remain basically unchanged. Thus corresponding reductions in the diameter of the licker-in, and of the take-off roll respectively, were proposed according to the reduction of the main drum diameter, e.g. maintaining the usual relations of these diameters.
SUMMARY OF THE INVENTION
The present invention provides a card equipped with at least one main drum, a cylindrical surface of the main drum being provided with a clothing, or prepared to take up a clothing respectively, which defines the working width of the card. The card comprises a feed means for feeding fibres to be carded to the main drum evenly over the full working width as well as a take-off means for taking off carded fibres evenly over the full working width. Also a flat arrangement is provided for carding fibres on the drum over the full working width. The card is characterized in that the diameter of the main drum ranges from 700 to 1000 mm, e.g. between 700 and 900 mm. This diameter advantageously can be chosen between 750 and 850 mm.
The working width preferentially exceeds 1300 mm, and is e.g. 1500 mm.
A card according to the present invention can be laid out as a revolving flat card or as a fixed flat card.
The small drum card preferentially is driven at a relatively high rotational speed in such a manner that a higher circumferential speed is effected than applied on conventional cards up to now. It thus becomes possible to improve the selectivity of the elimination process. The total (stress) load to which the fibres are subject in the card, however, should not be increased, which limits the number of working elements.
Card designers are permanently challenged to improve the precision of the elements forming the working gap. Achievement of higher precision, however, causes higher cost already in the manufacture of the individual elements, e.g. in the machining of a cast element as the narrow tolerances required cannot be met if a casting process is used. The problem is complicated further as the rotating elements are subject to deformations during operation under the influence of the centrifugal forces and to heat-induced expansion. The problem of deformations increases in a non-linear proportion with increasing rotational speeds. At higher rotational speeds care also is to be taken that no vibrations of the working elements, or of their support structures respectively, are caused, which could adversely influence the gap width decisively. Eccentricities of rotating elements in this connection also can exert a considerable influence.
The main drum of a conventional card is made from steel or from cast iron. Certainly it is possible to fulfil ever more stringent requirements using these materials. Fulfilment of the new requirements using conventional materials, however, results in disproportionate increases in manufacturing cost, in particular due to the further machining processes mentioned above (such as grinding or even machining) after the manufacture of the blank.
For a small drum card in particular it is feasible to produce a (rotary) body using fibre reinforced synthetic materials which can be applied without further processing of the bore as a card drum which meets the highest requirements. The term “card drum” in this context comprises the card main drum as well as the other drums or rolls such as e.g. the licker-in or the take-off roll. Fibre reinforced synthetic materials represent compounds or “composites” of e.g. glass fibres and a resin, the E-modulus of e.g. glass fibre filaments exceeding 70,000 N/mm
2
and the E-modulus of a polyester resin being merely of about 3000 N/mm
2
. The reinforcing fibres can be applied
Faas Jurg
Götz Theodor Gresser
Naf Beat
Sauter Christian
Wust Olivier
Dority & Manning
Maschinenfabrik Rieter AG
Neas Michael A.
Welch Gary L.
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