Draw module

Abstract

 The multi-stage draw module (20) comprises a number of draw roller pairs (22,23,24) comprising at least one upper and at least one lower draw roller pair in a staggered arrangement relative to a theoretical plane (P2) of reference; each draw roller pair (22,23,24) includes two rollers (221,222;231,232;241,242) having essentially parallel axes and essentially the same axial length, and all draw roller pairs have essentially parallel axes arranged substantially perpendicularly to the plane (P2) of reference; the staggered arrangement of the draw roller pairs is defined essentially by a longitudinal offset of each upper draw roller pair relative to an adjacent lower draw roller pair; the offset corresponds essentially with the working length of an upper draw roller pair; the theoretical plane (P2) of reference has an inclination of between 20 and 60 degree relative to a horizontal plane.

Description

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to the art of producing or processing man-made fibres and specifically to drawing of such fibres as a part of a melt-spinning production method or as a separate processing step.

[0002] Generally, drawing of man-made fibres, i.e. those consisting essentially of a synthetic or semi-synthetic polymer material, such as a nylon, polyester or polyalkylene, comprises an elongation of the fibre in solid state so as to achieve molecular orientation, or crystallization, of the fibres generally leading to an increased tensile strength and to obtain a "low oriented", "partially oriented" or "high oriented" yarn (LOY, POY and FOY, respectively) depending upon the degree of orientation achieved in one or more drawing stages.

[0003] Drawing may involve heating of the fibres by convection or contact and a typical conventional draw module comprises a number of subsequent drawing stages, each stage involving a passage of the yarn, typically in the form of one or more multi-filament strands, around a pair of adjacent rollers in which the "down-stream" roller rotates at a higher peripheral speed than the "up-stream" roller of each pair.

[0004] The terms "up-stream" and "down-stream" as used herein are relative terms and refer to a position closer to, or more removed from, the infeed portion of the drawing process or apparatus. In other words, yarn at an up-stream portion of the process or apparatus will have a relatively lower degree of orientation than at a more down-stream portion of the same process or apparatus.

[0005] A main problem in any continuous process involving treatment of filaments, man-made or otherwise, is rupture or breakage of the yarn, and various means are known for maintaining continuous plant operation upon breakage of a filament or yarn in an apparatus in which a number of filaments or yarns is processed simultaneously. Typically, the path of the yarn, strand or filament is provided with several control and "deviating devices" which will trap and carry away the continuously supplied up-stream end portion of the yarn, strand or filament after a break.

[0006] It should be noted that the terms "yarn" and "strand" as used herein both refer to a continuous structure composed of a plurality of monofilaments, the difference being one of a differing degree of entanglement in the sense that a strand will have little or no mutual entanglement, intertwining, twisting or the like of the essentially parallel filaments whereas as typical yarn will show less or no parallel alignment of the filaments that constitute the yarn. However, as the degree of parallel alignment, on the one hand, and entanglement, intertwining, twisting or the like, on the other hand, of the filaments of a strand or yarn is believed to be of subordinated importance herein, the term strand is assumed to encompass yarns, and vice versa.

[0007] Accordingly, whenever the term "strand" is used herein below, it will encompass strands with any degree of parallel alignment of its filaments as well as strands wherein the filaments show entanglement, intertwining, twisting or the like.

[0008] Generally, deviation of a broken filament or strand is effected by a stationary suction nozzle that catches and swallows, generally by suction, the broken end of the upstream portion and continues to remove that filament or strand yarn portion into a yarn waste bin until an operator supplied with a cutter and mobile suction device severs the filament or strand at a point before its entry into the deviating device and proceeds to "draw" the broken filament or strand down-stream and around or through any subsequent stages of the processing method or apparatus. For this reason and to provide access to all portions of a multistage draw module, the roller pairs are arranged in a staggered or stepped arrangement so that any downstream roller pair protrudes beyond the adjacent up-stream roller pair by an axial offset corresponding essentially to the "operative width" or of the down-stream roller pair. The term "operative width" as used herein refers to that part of the axial length of a roller, or roller pair, which is in direct physical contact with the windings of the filament or strand.

[0009] While such prior art multi-stage draw modules are available commercially, e.g. as Draw Module Multisystem from Filteco s.p.a of Cerrio Maggiore, Milano, Italy, and have been well received by the industry because of favourable performance properties and applicability to various processing environments, they tend to have a relatively large overall "size", "width" or "depth" i. e. that dimension of the draw module that increases with each roller pair by the operative width of that roller pair, and this may be a major disadvantage when operating space is at a premium.

OBJECTS AND SUMMARY OF THE INVENTION

[0010] Accordingly, it is a main object of the invention to provide for a multi-stage draw module where the "depth" or "width" dimension of the apparatus does not increase by another operative width when another roller pair is added, but without any sacrifice of accessibility of the draw rollers for breakage repair in the conventional manner.

[0011] It is a further object of the invention to improve the ease of access of and to a multi-stage draw module for purposes of maintenance or repair without the need to use external aids, such as scaffolds, ladders or the like means.

[0012] Now, according to the present invention, these main objects as well as further advantages explained in more detail below will be achieved by a novel draw-module of the type having a number of draw roller pairs, e.g. from 2 to 6 roller pairs or even more, comprising at least one upper and at least one lower draw roller pair in a staggered arrangement relative to a theoretical plane of reference, each draw roller pair including two rollers having essentially parallel axes and essentially the same axial length, and all draw roller pairs having essentially parallel axes arranged substantially perpendicularly to said plane of reference; said staggered arrangement of said draw roller pairs being defined essentially by a longitudinal offset of each of said upper draw roller pair relative to an adjacent lower draw roller pair, said offset corresponding essentially with the operative width, or strand-contacting axial length, of an upper draw roller pair; according to a general feature of the invention, the said theoretical plane of reference has an inclination of between about 20 and about 60 degree relative to a horizontal plane, preferably of about 35 degree.

EXPLANATION OF THE DRAWINGS

[0013] The invention will be better understood and further objects will become apparent when considering the enclosed drawings in which:

Fig. 1A is a semi-diagrammatic side view of a prior art multi-stage draw module with a plurality of axially off-set draw roller pairs;

Fig 1B is a front view of the prior art draw module shown in Fig. 1A;

Fig. 2A is a semi-diagrammatic side view of a preferred embodiment of the novel draw module according to the invention; and

Fig. 2B is a front view of the draw module shown in Fig. 2A.

[0014] The prior art draw module 10 shown semi-diagrammatically in a side view in Fig. 1A comprises a frame 11 provided with three draw roller pairs 12, 13 and 14 and a feed-in roller device 15 for passing and drawing four multifilament strands S fed into draw module 10 at the upstream end via a conventional breakage control and deviating device 16. The preceding apparatus portion (not shown) or process step could be a conventional meltspinning apparatus or a yarn package holder (not shown). A take-up device or winder 18 is provided at the downstream end of module 10, preferably including a conventional intermingling device. Strand guides 171 and 172 are provided to control the travel path of each multifilament strand. While only one draw roller 121, 131 and 141 is shown in Fig. 1A it will be appreciated that the axes of all roller except the holding roller 152 of the entry roller device 15 are arranged in parallel and include an angle of about 90 degree with a theoretical reference plane P1 which, in turn, is essentially arranged vertically, i.e. perpendicular in that it includes an angle α1 of about 90 degree with the horizontal. In other words, the term "staggered arrangement relative to a theoretical plane of reference" is understood as referring a theoretical plane positioned at an angle of about 90° relative to the axes of the draw rollers.

[0015] It should be noted that the infeed roller device 15 having a larger roller 151 and a slightly inclined smaller roller 152, such arrangement can well be replaced with a pair of parallel rollers of the same or a different diameter as roller 151. Regardless of wether a pair of equally dimensioned parallel rollers or the dissimilar-pair arrangement 151, 152 shown in Fig 1A is used, it is apparent from Fig.1A that each "down-stream" roller pair (actually the roller pair in the "upper" position in Fig. 1A) is offset in an axial direction relative to the preceding "lower" or "upstream" pair by the working "width" (axial roller length covered by windings of the strands) of the preceding upstream roller pair.

[0016] It is only by such a staggered or stepped arrangement of the draw roller pairs that an operator can draw the "end" of a broken strand downstream onto the next roller pair since otherwise the strand portions would have to"cross" each other which is not only impractical but operatively unfeasible. Obviously, the "end" of the broken strand is not a stationary portion of a strand but a dynamically changing strand portion defined by the "type" of the mobile suction device (not shown) used by the operator when "mending" the path of a broken strand.

[0017] When considering Fig. 1B in conjunction with Fig.1A it is apparent that both rollers of each pair 12, 13 and 14 have the same diameters, are of the same length, and are arranged in parallel within each pair and between all pairs, again with the exception of an angularly displaced infeed roller 151 when such a feeding device is actually used (as shown in the drawings). Since draw modules of the type shown in Fig. 1A, 1B are known in the art, a detailed discussion of further components is omitted herein for brevity. It should be noted however, that conventional drives for the draw rollers will be used (not shown in the drawings) in accordance with the power requirements and the draw ratios required for any given situation. Also, some or all draw rollers may be heated in a conventional manner if this is advantageous for any given application.

[0018] The novel draw module illustrated in Fig. 2A and 2B is composed essentially of the same or similar elements and this is indicated in the figures by using the same second digits in the reference numerals and changing only the first digit in accordance with the numbering of the figures. The main difference regarding element structure resides in the roller supports which are essentially regular cylindrical in Figs. 1A and 1B (120,130,140) while they are irregular cylinders in Figs. 2A and 2B in that the axial mantle lines at the upper portions of the supports 220, 230, 240 are substantially shorter than the axial mantle lines of the lower support portions.

[0019] Notwithstanding the relatively minor structural modification of the draw roller supports apparent from a comparison of Figs. 1A,1B on the one hand, and Figs. 2A, 2B, on the other, the overall effect is substantial: because the theoretical plane P2 of reference according to the invention is not vertical or perpendicular but includes an angle α2 of about 20 to about 60 degree with the horizontal, the staggered arrangement and axial offset of the drawing roller pairs 22, 23, 24 as well as the larger roller 251 of the feeding roller device 25 needed for access by an operator when re-feeding a broken strand by means of a mobile suction device through all downstream stations is maintained while the lateral "width" or "depth" of a draw module according to the invention is not only substantially shorter than a comparable prior art machine but does not increase in depth if one or more additional draw roller pairs are added, and achieving such reduction at no sacrifice of accessibility for conventional strand breakage repair.

[0020] It is higly preferred according to the invention that, in addition to the change of angular position of the axes of substantially all draw rollers, substantially all draw roller axes should be essentially in parallel alignment. More specifically, maximum deviation from such parallelity should be less than 10° and preferably not more than about 5°.

[0021] It is apparent from the drawings that the "working width" of each roller of each draw roller pair, i. e. the axial length thereof that is essentially covered with the strand windings, is almost equal to the actual length of the rollers and corresponds typically to at least about 80% of the actual length. This is preferred for practical purposes and optimum efficiency.

[0022] Generally, the draw module according to the invention can be operated essentially under the same conditions as comparable prior art machines and, accordingly, a more detailed discussion of operational details is omitted for brevity.

[0023] The obvious and substantial advantages of a draw module according to the invention when compared with a prior art apparatus of the same capacity are believed to be an indication of the unobviousness of the invention as disclosed herein. It will be understood that the above showing of a preferred embodiment of the invention as illustrated in Figs. 2A and 2B is not intended to limit the invention and that many modifications within the scope of the inventive teaching will be apparent to those skilled in the art.

Claims

1. A multi-stage draw module (20) comprising a number of draw roller pairs (22,23,24) including at least one upper (23) and at least one lower (24) draw roller pair in a staggered arrangement relative to a theoretical plane (P₂) of reference, each draw roller pair (23,24) including two rollers (231,232;241,242) having essentially parallel axes and essentially the same axial length, said essentially parallel axes being arranged substantially perpendicularly to said plane of reference; said staggered arrangement of said draw roller pairs being defined essentially by a longitudinal offset of each of said upper draw-roller pair relative to an adjacent lower draw roller pair, said offset corresponding essentially with the working length of an upper draw roller pair; said theoretical plane of reference having an inclination of between 20 and 60 degree relative to a horizontal plane.

2. The draw module of claim 1, wherein said theoretical plane of reference has an inclination of from 30 to 60 degree relative to said horizontal plane.

3. The draw module of claim 1, wherein said theoretical plane of reference has an inclination of about 45 degree relative to said horizontal plane.

4. The draw module of any of claims 1 - 3 comprising three draw roller pairs (23,24,25) in said staggered arrangement.

5. The draw module of any of claims 1 - 4 comprising a feeding roller device (25) provided upstream of said draw roller pairs.

6. The draw module of any of claims 1 - 5 wherein said essentially parallel axes deviate from parallelity by less than 10 degree.

7. An apparatus for processing a yarn, said apparatus including at least one yarn drawing stage comprisisng at least one draw module as claimed in any of claims 1 - 6.

8. A method of processing a yarn including at least one drawing step wherein said drawing step is effected by means of a draw module as claimed in any of claims 1 - 6.

Drawing