US2771639A - System for drafting fibrous materials - Google Patents

Description

Nev. 27, 1956 J, M. B. AYMERICH 2,771,639

SYSTEM FOR DRAFTING FIBROUS MATERIALS Filed May 28, 1951 2 Sheets-Sheet l Nov. 27, 1956 J. M. B. AYMERICH 2,771,63Q SYSTEM FOR DRAFTING FIBROUS MATERIALS Filed May 28, 1951 2 Sheets-Sheet 2 INVENTOR, aw; MATE/A Eascw-Aymmwcw United States PatentO SYSTEM FOR DRAFTING FIBROUS MATERIALS Jose Maria Bosch Aymerich, Barcelona, Spain Application May 28, 1951, Serial No. 228,586 Claims priority, application Spain July 3, 1950 2 Claims. (Cl. 19-130) The invention relates to a method and mechanism for drafting cotton and other fibrous materials in spinning and roving frames.

The drawing out of rovings or slivers has been performed in apparatus which essentially consists of two pairs of rolls. The one pair comprises the feed rolls which revolve at relatively low speeds and feed a sliver of a certain weight per unit of length, and the other pair comprises the drawing rolls which revolve at a higher speed than the feed rolls and draws out the strand of fibers received from said feed rolls. The length of the produced draft corresponds to the difference between the peripheral speed of the feed rolls and that of the drawing rolls.

In the first stages of the development of drafting apparatus, the desired stretch was obtained by a series of separate drafting mechanisms which each stretched the fibers to about 3 to times their length prior to drawing. When greater drafts were intended the fibers in the sliver spread out in different directions which produced weak spots and breaks. Such breaks required a continuous supervision of the spindles, i. e. an increased number of operators. Therefore, it was considered more economical to use a greater number of drawing frames producing a limited draft instead ducing a longer draft.

In order to increase the efficiency of the work of these machines and to avoid an excessive number of successive drafting steps independent of each other, the so-called long draft system was developed. A fundamental problem in the development of said system concerned the guiding of the sliver on its way between the two pairs of rolls, i. e. in the zone where the actual stretching is carried out, and various solutions of this problem have been suggested. Many of the proposed devices were modifications of the idea to provide so-called draft aprons which guided the fibers wholly or partially in a portion of the draft zone and delivered them near the nip of the draft rolls.

Another mechanism for reducing the number of spinning steps was based on the general idea of providing drawing devices with three and four pairs of rolls, so as to divide the total draft into two steps within'a single apparatus. The first step produced a preliminary draft, suitable to take out the twist which the entering sliver may present, and the second step was arranged to effect maximum elongation.

The advantages of these modern drawing mechanisms are obvious and the "long draft system has been widely introduced in spinning mills. Nevertheless, quite a number of problems remain, which have not been satisfactorily solved so far.

The two-step drafting mechanisms present the drawback that the fibers have the tendency to leave the first draft stage in a somewhat spread out and dispersed condition, and this condition is accentuated during their travel to and through the second stage: therefore. they enter the second stage under conditions unfavorable to the drawof fewer frames proing, as they are weaker and/or lack the twist which the sliver normally had when processed according to the old method in a plurality of seperate drawing mechanisms. Many solutions have been proposed for obtaining a compression or a guided travel of the sliver on its way from the one to the other drawing step. The devices designed for this purpose comprised either rigid and fixed surfaces or endless belts of flexible material or other means which rendered the apparatus excessively complicated and involved high operating cost of the machine; objectionable long interruptions in the delivery of each spindle were unavoidable when a breakage in the sliver occurred.

Draft aprons present an efficient guiding means, but because of their elastic composition they are subject to deformations and elongations and, therefore, inherently unable to ensure completely uniform working conditions and rate of travel over prolonged periods of time.

Other proposals were directed to the recovery of the fibers which had strayed out or flared during the first drawing step.

Cleaning rolls were provided in order to avoid clogging of the drawing roll of the first draft stage, and/0r specific means were arranged to deliver the fibers in a more condensed condition to the second drawing stage. However, all those designs did not give a complete solution of the problem of maintaining a complete control of the fibers in a multi-stage drafting mechanism.

A principal object of the invention is to provide a long draft system in which the sliver leaves the drawing rolls of the first drafting stage as a compact, uniform strand of fibers.

Another object of the invention is to provide means which ensure maintaining said compactness and uniformity of the sliver on its travel from the drawing rolls of the first drafting stage to the second drafting stage.

Still another object of the invention is to provide means which feed the sliver to the second drafting stage as a compact strand of parallel fibers so as to prevent the rolls from being clogged by loose stray fibers. Such obstruction disturbs the smooth operation of the drafting mechanism.

Other objects and advantages will become apparent from a consideration of the specification and claims.

In the conventional lon -draft mechanisms, the stray fibers were condensed in the space comprised between the drawing roll of the first drafting stage and the feed roll of the second drafting stage; or to put it in a more generic language, the aim was to rearrange the fibers in the zone comprised between the two drafting stages, i. e. where the draft or stretch is nil or practically negligible.

In contradistinction thereto, the aim of the present invention is not to rearrange the fibers after they have strayed out but to avoid their straying out at all. In other words, the aim is not to correct the result but to eliminate its cause, which allows of attaining much longer drafts. According to the invention, any twist still present in the delivered sliver is eliminated in the first drafting stage and this untwisting operation i effected simultaneously with guiding and condensing manipulations, which are applied during the first drafting stage, thereby avoiding the spreading out of the fibers that otherwise will surely occur when the sliver loses its twist. Subsequently, the transfer of the fibers from the first to the second drafting stage is positively guided and the sliver travels during said transfer at all times over one or more cylindrical rigid and convex surfaces which revol've at aperipheral speed substantially equal to the rate of travel of the sliver before it is subjected to the action of the second drafting stage, In this way, I avoid all irregularities which are produced by enclosing the sliver between surfaces movingat a .spee d diiferem from the rate of travel of the sliver or between very elastic surfaces which readily deteriorate and easily may produce irregularities in the obtained yarn.

The aim of the invention is attained by arranging a condensing element between the feed rolls and the draft rolls of the first drafting tage; this element keeps the fibers in parallel alignment at a point of their travel where they would otherwise stray out following their untwisting, and it guides or leads the fibers in said parallel alignment to the tangency line of the draft rolls.

One or more guiding rolls are provided which positively guide the sliver from the draft rolls of the first draft stage to the feed rolls of the next draft stage in uch a way that the sliver is at all times supported by roll surfaces. Therefore the fibers never travel unsupported through free space but are always supported by cylindrical surfaces. In this arrangement, the sliver is positively guided by a series of guiding rolls, whereby the first roll of such series is formed by one of the draft rolls of the first draft stage and the last guiding roll is constituted by one of the feed rolls of the next draft stage.

The positively driven feed roll of the second or fol lowing draft steps should have a slightly higher peripheral speed than the positively driven draft roll of the preceding stage; consequently, the sliver is subjected to a very slightly increased rate of travel over the guiding rolls between two consecutive draft stages and the fibers of the sliver are held wholly in line with the path of the sliver and parallel and attached to the roll surfaces.

The guiding rolls are so arranged as to maintain the direction of travel of the sliver, and they should exert by their weight a slight pressure on the sliver at the tangency line with the contacting rolls. In this way, the fibers in the sliver have the possibility to slip, which is useful in drafting very long fibers.

If several guiding rolls are provided, each alternate roll should have a grooved or fluted surface.

In a specific, particularly simple and economic embodiment of the invention, the function of the guiding rolls, i. e. the positive uninterrupted guidance of the sliver between two consecutive draft stages, is taken over by the rolls of the drawing mechanism proper, i. e. by one of the draft rolls of the first drawing stage and by one of the feed rolls of the second drawing stage. For instance, the bottom draft roll of the first drawing stage and the top feed roll of the second drawing stage, or inversely the top draft roll of the first drawing tage, and the bottom feed roll of the second drawing stage, may act as such guiding rolls; in both cases, said rolls play a double role simultaneously, as guiding roll and as draft roll or feed roll, respectively.

If the system of guiding revolving rolls consists of more than two rolls, the first and last roll will assume the same double function as outlined hereinbefore.

The invention will be readily understood from the following description in connection with the accompanying drawings which show some illustrative embodiments of the invention. In the drawings:

Fig. l is a diagrammatic vertical sectional view of a drawing mechanism embodying the invention;

Fig. 2 is a diagrammatic perspective view of the elements shown in Fig. 1, wherein however the rolls are not shown in their true size relationship in order to present a better view of the mechanism;

Fig. 3 is a diagrammatic vertical sectional view of another embodiment;

Fig. 4 is a vertical sectional view of still another embodiment of the invention, showing three draft stages, and

Fig. is a vertical sectional view of a mechanism similar to that shown in Figs. 1 and 2.

In the drawings, 1 represents the sliver before entering the drawing mechanism, and 2 the sliver after drawing, 3 and 4 are the feed rolls, and 5 and 6 the draft rolls of the first preliminary draft stage.

The final draft is obtained in the roll pairs 7, 8, 9, and

10, of which 7 and 8 represent the feed rolls and 9 and 10 the draft rolls.

In a three-stage drawing mechanism (Fig. 4), the last stage is represented by the feed rolls 17 and 18 and the draft rolls 19 and 20. The zone between the second and third drawing stage extends normally from 24 to 25, although the drafting action can be extended beyond the corresponding feeding cylinders.

As usual in mechanisms of this kind, the preferably grooved or fluted bottom rolls 4, 6, 7, it), 17, and 19 are positively driven, and the top rolls 3, 5, 8, 9, 18 and 2t are covered with some cushioning material, such as leather, cork, rubber, or the like, and frictionally driven from the bottom rolls. The drawing rolls 6 and 10 are driven at a greatly higher peripheral speed than the corresponding feed rolls 4 and 7, so as to obtain the desired draft. The bottom feed roll 7 of the second draft unit is preferably driven at a very slightly higher peripheral speed than the drawing roll 6 of the first unit, and the same is true with respect to the feed roll 17 and the drawing roll 10. The top rolls are pressed down by conventional weighting means, as indicated by arrows (Fig. 4).

The zone between the two drawing stages of the twostage drawing mechanism extends from point 11 to point 12. In this zone, the sliver is in continuous contact with the rolls 6 and 7 (Figs. 1 and 2) or 5 and 7 (Fig. 5) or with the rolls 6, l3 and 7 (Fig. 3); the first and last rolls of these groups of rolls assume the double function outlined hereinabove, and only a slight pressure is exerted on the sliver in this zone so as to allow slipping of long fibers of the sliver.

Additional guiding rolls are shown in Fig. 3 at 13 and in Fig. 4 at 13, 21 and 22. These rolls have a smooth surface when located between fluted bottom rolls of the drawing mechanism; when arranged in contact with a softcovered top roll, the guiding roll should be fiuted as shown for roll 21 to ensure the proper gripping of the sliver. As will be readily seen upon inspection of the drawings, the guiding rolls are so disposed as to exert some light pressure on the tangency lines with the contiguous rolls; this ensures the transfer of the fibers but allows slipping of any fiber already pulled by the following draft rolls.

The condensers which prevent fiaring of the fibers in those zones where the draft isproduced may be of known design and are represented by the numeral 14 in the first drawing step, by 15 in the second drawing step, and by 23 in the third step (Fig. 4). 16 is the condenser which is normally used at the intake of the sliver in the system.

A particularly'simple and compact embodiment of the invention is shown in Fig. 5 where the entire two-stage draft mechanism consists of 8 rolls, a pair of feed rolls and a pair of draft rolls for either unit. In this embodiment the top feed roll of the first draft stage, the top draft roll of the same stage, the bottom feed roll of the second draft stage and the bottom draft roll of said stage have the axes substantially situated in the same plane, which feature constitutes a preferred but not necessary modification. The sliver which leaves the first drawing stage at 11 is first pulled around the surface of the top draft roll of said first stage until it reaches the tangency line of said draft roll with the bottom feed roll of the second drawing stage, and it is then pulled around the fluted surface of said bottom feed roll to the nip 12 of the pair of feed rolls 7, 8 of the second drafting stage. The sliver travels all the time on surfaces of revolving rolls from the exit 11 of the first drawing stage to the intake point 12 of the second drawing stage and is positively guided in an S shaped path between points 11 and 12. The path of the sliver between the point 11 and the drafting point 28 of the two drawing rolls of the second stage should be somewhat longer than'the length of the longest fiber operated on. This prevents breaking of the fibers and makes it unnecessary to change at any time the position of the rolls 5, 6, 7, 8, 9 and 10 for working up fibers of widely varying lengths. The roll 7 is driven at a very slightly higher peripheral speed than the roll 6; rolls 26 and 27 designate conventional felt roils used as cleaners.

The described arrangement is suitable for any kind of spinning, drafting and roving frames, and it ensures a very high degree of control of the fibers during the whole travel of the sliver. It may be used to combine the work of several drafting manipulations in a single compact unit for producing a yarn of exceptional uniformity.

Although I have illustrated and described several forms of the invention, it will be obvious that modifications can be made by any person skilled in the art without departing from the scope of the invention as defined in the appended claims.

What I claim is:

1. A drawing mechanism for a strand of textile fibers comprising a plurality of drawing units', each of said units including a pair of feed rolls, a pair of drawing rolls and a condenser, and at least one revolving guiding roll between a drawing roll of one unit and a feed roll of the next unit, said guiding rolls forming together with the surface of said feed rolls and drawing rolls a continuous support for the strand of fibers from its exit from one drawing unit to its intake by the next drawing unit.

2. A drawing mechanism as defined in claim 1 wherein the axis of the guiding rolls is located above the plane in which the axes of the drawing rolls and feed rolls contacting said guiding rolls are located.

References Cited in the file of this patent UNITED STATES PATENTS 128,618 Harris July 2, 1872 317,675 Russell May 12, 1885 541,046 Harley June 11, 1895 2,203,423 Walsh et al. June 4, 1940 2,238,659 Reynolds Apr. 15, 1941 2,244,461 Kettley June 3, 1941 2,422,444 Balmes Solanas June 17, 1947 2,472,929 Weinberger June 14, 1949 FOREIGN PATENTS 175,801 Spain Nov. 23, 1946 649,109 Great Britain Jan. 17, 1951 693,422 France Apr. 21, 1931

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