Method of preventing knot breakage during drawing of yarn

Jan. 16, 1968 m. f. culpin 3,364,293

METHOD OF PREVENTING KNOT BREAKAGE DURING DRAWING OF YARN

Filed April 13, 1964 2 Sheets-Sheet 1

<img file="US3364293A_D0001.tif" />

Jan. 16, 1968 m. f. culpin 3,364,293

METHOD OF PREVENTING KNOT BREAKAGE DURING DRAWING OF YARN

Filed April 13, 1964

Sheets-Sheet 2

<img file="US3364293A_D0002.tif" />

3,364,293

Patented Jan. 16, 1968

United States Patent Office

3,364,293

METHOD OF PREVENTING KNOT BREAKAGE DURING DRAWING OF YARN

Michael Frank Culpin, Pontypool, England, assignor to British Nylon Spinners Limited, Pontypool, England Filed Apr. 13,1964, Ser. No. 359,106

Claims priority, application Great Britain, Apr. 24,1963, 16,092/63

Claims. (Cl. 264—290)

ABSTRACT OF THE DISCLOSURE

Method and apparatus for suddenly releasing the tension in a synthetic yarn which is being drawn so that the presence of a knot in the yam will not increase the tension in the drawing zone to a value at which the yam will break. The tension release device is one which slowly lengthens the yarn path between feed rolls and a snubbing pin prior to the approach of a knot and which then suddenly releases the yarn reserve just before the knot reaches the drawing zone. The tension release device may be any of several known devices and may be operated automatically or manually.

Disclosure

This invention relates to drawing machines for the permanent stretching or drawing in the solid state of synthetic yarn and more particularly to such machines as are capable of handling knotted yam.

The word “yarn” as used in this specification is to be understood as including both monofilamentous yarn (i.e. a monofilament) and multifilamentous yarn.

It is well-known to draw synthetic yarn in the solid state in order to increase its strength, which may be measured by the tenacity in grams per denier at break. The drawing is commonly effected by passing the yarn around (a) a feed roll and (b) a draw roll revolving at a greater peripheral speed than the feed roll. The single feed and draw rolls may each be substituted by multiple rolls to ensure that the yarn is adequately gripped, alternatively nip rolls may be employed. The tendency of the yarn to slip on the roll may also be countered by winding the yarn several times around the roll, conveniently with the use of an auxiliary roll to separate the turns, known as a separator roll. In drawing yarn consisting of synthetic filaments, for example, synthetic linear polyamide filaments such as polyhexamethylene adipamide ones, the seat of the drawing action may be advantageously localised by the employment of a snubbing pin situated between the feed roll (or rolls) and the draw roll (or rolls), round which pin the filaments are looped on their way from the feed roll to the draw roll. In this case nearly all the drawing of the yarn occurs at the said snubbing pin, that is to say, very' close thereto or actually thereon.

However, owing to the use of bobbins and for other practical reasons, undrawn yarn cannot be made commercially in indefinite long lengths, and consequently it has to be knotted occasionally when a new length is joined on to the old one. Trouble is then apt to be experienced, especially in the case of the heavier deniers e.g. a multifilament yarn of 800 denier or over, when the knot arrives at the drawing point or zone, owing the rupture taking place. The reason for the rupture is that the knot itself is difficult or impossible to draw by reason of its increased denier and the physical changes in the filaments brought about by the operation of knotting. Particular difficulty is encountered when yam of relatively high tenacity is to be manufactured because in this case the filaments are drawn at a draw ratio near to the maximum possible draw ratio.

It has now been found possible temporarily to suppress the drawing action of a conventional machine while a knot passes through and thus prevent rupture of the filaments. The temporary suppression of the drawing is accomplished by slowly lengthening the yarn path between the feed roll and the snubbing pin with conventional mechanical means prior to the approach of the knot, so that a reserve of yarn accumulates. This yarn is suddenly allowed to return to its shorter path (i.e. the path before lengthening) by the aforesaid conventional mechanical means just before the knot reaches the drawing zone. This causes a sudden release of the reserve of yarn, thereby depressing the tension nearly to zero and in any case far below the drawing tension so that there is no tendency for drawing of the knot to occur. It is important that the aforesaid lengthening of the yam path be sufficiently slow for the drawing process to be unaffected or not noticeably affected. The drawing zone is in the immediate neighbourhood of the snubbing pin being for the most part actually on it and/or adjacent thereto.

Accordingly the invention consists as already indicated, of a process for drawing in the solid state synthetic yam with occasional knotted joints comprising forwarding said yarn from one or more conventional feed rolls to one of more conventional draw rolls revolving at a greater peripheral speed than said feed rolls, the yam passing round a snubbing pin on its way from the feed rolls to the draw rolls, slowly lengthening the yarn path between the feed rolls and the snubbing pin by conventional mechanical means prior to the approach of a knot and by the same means suddenly releasing the reserve of yarn thus accumulated by allowing the yarn to return to its original unlengthened path just before the knot reaches the drawing zone.

Apart from polyamides, already mentioned, examples of other synthetic filaments to which the present process applies are:

stereospecific polypropylene polyethylene terephthalate polyacrylonitrile polyethylene

The invention includes synthetic yarns whenever drawn by the above process.

The knotted joint may be made in the synthetic yarn by numerous known processes. A most convenient way of knotting is described in British Patent No. 956,992. A knot made in this manner in a multifilament yarn of say, 800 denier, might occupy a length of yarn of about 2 inches.

Numerous forms of apparatus which may be used to lengthen the path of the yarn are illustrated by way of example in the accompanying diagrammatic drawings whereof descriptions are subjoined. In all the drawings the broken line shows the original (unlengthened) path of the yarn and the full line the lengthened path thereof. The pulleys shown in the drawings are all idler pulleys; in other words they merely serve as yarn guides.

FIGURE 1 illustrates a device comprising a disc 1 rotatable about its centre 2 and bearing two idler pulleys 3, 4. The yam is led to and from the said disc by the idler pulleys 5, 6 respectively. The yam path is lengthened by rotating the disc for a fraction of a turn in a clockwise direction. On allowing the disc suddenly to turn back in an anti-clockwise direction until the yam assumes the shortened path shown by the broken line 7, the drawing action is temporarily suppressed.

FIGURE 2 shows a device comprising a plunger 7 bearing an idler pulley 8. When the plunger is raised the yam path between the idler pulleys 9, 10 is lengthened.

FIGURE 3 depicts a device similar to that of FIGURE 2, except that a triple plunger 11 bearing 3 idler

3.364.293 pulleys 12, 13, 14 is incorporated, the yarn path being controlled by the aforesaid three pulleys in conjunction with the idler pulleys 15, 16, 17, 18.

FIGURE 4 is a diagram of a device somewhat analogous to a gate tensioner, wherein the yarn path is lengthened by increasing the distance between the fixed idler pulleys 19, 20, 21 and the pulleys 22, 23 which are mounted on an arm which pivots at 24.

FIGURE 5 pictures a device comprising a peripherally grooved disc 25 eccentrically pivoted at 26 and idler pulleys 27, 28 for guiding the yarn. The path of the yarn which slides over the disc 25 in the peripheral groove, is lengthened and shortened by turning the aforesaid disc 25. Preferably the latter is furnished with a periphery capable of revolving as the yarn passes thereover in order to eliminate any friction caused by the yarn sliding over the motionless disc.

FIGURE 6 portrays a truncated cone 29 mounted on a spindle 30 capable of being shifted axially in its bearings 31, 32. The yarn guided by the pulleys 33, 34 passes round the cone. By shifting the cone so that the yarn passes round a larger or smaller circumference thereof the yarn path can be lengthened or shortened.

Whilst it is sometimes convenient to operate the mechanical means for lengthening and shortening the yarn path manually, the device may be rendered automatically operable by the employment of conventional electronic means and/or electrical relays in conjunction with known means for detecting and signalling the approach of the knot. For the latter purpose devices incorporating the principles of the numerous known slub catchers can be applied.

The following example is for the purpose of illustrating not restricting the invention.

EXAMPLE

A tow of total denier 6400 consisting of 8 yarns each containing 200 filaments of 4 denier is drawn at an effective draw ratio of 5. Each of the 8 yarns is knotted at different places in the tow by the method described in British Patent No. 956,992. Each knot extends over 2 inches of the yam. The knots occur in each yarn once every 100,000 feet approximately. The tow passes through the feed rolls at 100 feet per minute, then round the snubbing pin and finally through the draw rolls at 500 feet per minute. 500 feet per minute is equivalent to five sixths of a foot, i.e. 10 inches, in one tenth of a second. This is a suitable time to suppress the drawing action in order to permit the passage of a knot, because a length of yarn of 10 inches allows for the knot itself (2 inches) for some 50 yarn on either side thereof, of which the properties may have been adversely affected in the process of knotting and also for some slight inaccuracy in timing the release of the yarn reserve in order to suppress the drawing action. During 20 seconds before a knot in one of the 8 ⁶³yarns is due to arrive at the snubbing pin the reserve of 10 inches in the yarn is slowly accumulated by means of the apparatus shown in FIGURE 2 which is placed between the feed rolls and the snubbing pin. The time taken ⁴ .

to lengthen the yarn path by 10 inches is thus 20 seconds. The reserve of yarn is released just before the knot reaches the snubbing pin. No rupture of the yam occurs. This operation does not affect the drawing of the other 7 yarns 5 which proceed normally until the arrival of a knot is imminent in another of the 8 yarns. Separate devices for each yarn can be provided but it is more convenient to employ one device capable of being shifted under the particular yarn the path of which is required to be length70 ened, for it is to be understood that during the process of drawing and passage round the snubbing pin, all 8 yarns comprising the tow are in practice spread out side by side in ribbon formation.