Automatic toe closing on the knitting machine

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Many novel methods have been devised for closing toes during the knitting operation. Generally, they have been restricted to single-cylinder sock machines, in coarser gauges, and not double-cylinder sock machines or seamless stocking and tights machines. They have achieved only limited success against conventional toe closing during post-knitting operations where automated seaming and handling techniques have considerably reduced labour content, time, and costs involved.

The main disadvantages of toe closing on the knitting machine have been one or more of the following: the necessity for a complex adaptation of the knitting machine and its knitting sequence with high capital costs; reduced production speeds; lower patterning potential; poor comfort; unsatisfactory wearing properties; and unconventional appearance. The following methods have been devised to overcome some of these disadvantages:

1 The rosette toe. Two types of toe that achieved some success in the late 1960s, were the Scott and Williams and the Duravent closed toes. Both commenced at the toe with circular knitting to produce a double thickness welt that was restricted to form a rosette closed toe, either by twisting the fabric tube or by wrapping yarn around it. These methods failed because of the unconventional appearance of the toe and the insecure finish to the welt, which was knitted last.

2 The true-linked toe. The appearance and comfort of a true-linked toe can now be achieved on a linking machine supplied directly from the knitting machine. The linking machine is either directly mounted on the knitting machine or it is supplied from a bank of machines. One sock is linked whilst the next is knitted. On the knitting machine, the open toe circle of fabric is held on a split dial that folds over to transfer and double-up the loops onto half the dial ready for loop-to-loop linking. Time and costs are saved by not having pre-linking courses, but the unit can add 30 per cent to the cost of the machine.

3 The Sangiacomo Lin Toe. This method (Fig. 21.5) uses the standard knitting sequence of welt first, toe last. It can be fitted to cylinder and dial true rib machines. The dial with its double loops is transferred to a Frullini patented, flange-mounted linking machine at the same time as the next sock is being knitted. The time required to transfer a sock for linking is 6-7 seconds. Knitting of the next sock occurs virtually immediately. Also, time and yarn are saved by not having additional pre-linking courses.

A true stitch-by-stitch single-course linked seam is on the outside and a flat seam is next to the foot. The finest gauge limit is probably 200 needles x 4 inches diameter. The toe-closing unit, which can be retro-fitted to some sock machines, costs approximately 30 per cent extra. To reduce the cost of linking, after the sock has been knitted it can be robotically transferred to an off-machine minilinker which can close the toes of socks from a number of machines [7].

4 The knitted closed toe. Knitted toe closure involves commencing at the toe and joining the instep needle loops to the toe loops. As the welt is knitted last, there is a problem in obtaining a neat, secure finish. Patents for a swivelling transfer dial to produce loop-to-loop knitted toe closure were first taken out by Giulano Ugolini in the early 1960's [8].

5 The Matec Closed Toe. With this system, the closing line on the outside of the sock is practically invisible and the result is equal to that achieved by hand linking. The time taken to close the toe is 5-6 seconds. All yarn waste is eliminated. It is possible to retrofit this to all Matec single-cylinder machines.

The toe set-up course is picked up by the half-dial transfer elements and is knitted in a reciprocating manner on the sole half needles. As soon as the toe is

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Fig. 21.5 Lin Toe toe-closing on the machine [Sangiacomo].

knitted, the dial rises further and swivels, bringing its set-up course over the cylinder needles of the instep half of the foot. The loops are then transferred from one half of the cylinder to the other. An externally-mounted crochet hook closes the toe. The foot length is then knitted on the full diameter.

6 Another method employs the dial as the transfer element, enabling the set-up course to be run by the dial, stitch-by-stitch, as the toe pouch is knitted by reciprocation. The toe fabric is then transferred to the other half of the needles that knit to close the toe. Afterwards, circular knitting commences for the foot.

7 The Conti Florentia Air Toe. This system produces a random linked appearance, not exactly loop-for-loop. It is therefore most suitable for coarser gauge sports socks. It is simple and virtually invisible on the outside of the sock. At the start of the toe, two courses of covered elastic are knitted by reciprocation. Sufficient fabric is then knitted to transfer across to the other half of the cylinder. Special hooked sinkers engage with the fabric aided by air jets which blow down onto the fabric. As the cylinder turns, the new yarn is knitted into the elastic yarn course.

21.17 Tights

Early versions of tights were made by seaming a hose leg to each leg of a pair of panties. Today, the conventional method of constructing tights is to knit two long seamless hose legs (having about 2000 courses). In the making-up operation, the legs are 'toe-closed'. A slit is then cut vertically down the centre of the inner side of the upper (body) section of each leg. The slits are then opened so that the left side of one leg slit can be seamed to the right side of the other leg slit in a single operation. This is termed the 'line closing' or U-seaming' operation and it converts the top of the two tubular legs into one large tubular tights body. The top of the legs may contain the knitted-in elasticated waist-band or this may be seamed on later. The crotch area may then be cut or burned out so that a shaped gusset (often of knitted cotton fabric) can be inserted and seamed in its place.

21.17.1 Automated seaming

The cost of manual handling and seaming, combined with the static price of the finished article, has encouraged the search for alternative methods of production in the form of one-piece tights knitted on the machine. However, at present, increasingly automated tights seaming techniques have proved to be more successful. Unfortunately, there are considerable problems involved in automatically picking-up, orientating, guiding, handling, and sewing one of the lightest, flimsiest, most extensible and unstable of knitted structures. It is therefore essential that the hose legs are in a smooth, flat, undistorted state when they are removed from one operation and presented to the next. With the making-up operations being separate modules serviced by robotic handling devices, it is possible to incorporate different makes of machine as modules and to introduce and remove them as and when required, without interfering with previous or subsequent modular operations.

Whereas previously the hose legs were presented to the automatic seaming operation by a skilled operative, the 'pick and place' system automatically picks-up and 'double positions' the garment using two reference points on it [9].

The Detexomatic pick and place system uses a pick-up probe involving suction and gripping fingers to collect legs from a revolving basket. A second picker presents the leg to an orientation device, either toe-to-waistband or waistband-to-toe. If it is the wrong way, it will be reversed.

On the Esox system, vision detection is used to align the legs for automated tight assembly by detecting and aligning a colour marker in the waist band and the six wales of mesh that indicate the cutting line.

21.17.2 One-piece tights

The various knitted one-piece tights methods normally involve using a hose machine of 3- to 4 inches (9.5-10cm) diameter with approximately 400 needles, and knitting a modified tube of fabric. It is necessary to obtain a width of 4 to 5 inches (10-12cm) for the ankles and a lateral stretch of 16 to 20 inches (40-50 cm) for the body, which may be achieved with textured yarn.

The main problems have involved fit, quality, and the time and cost of the knitting sequence. More specifically, fit and quality problems have included insufficient depth in the body, fabric breakdown under tension at the leg joins, insufficient extension of fabric at the thighs, and an excess of fabric in the crotch section.

Although smaller sizes can be achieved, larger sizes are more difficult and larger machine diameters such as 4- inches may be used for these.

One of the first types of commercially-produced one-piece tights was patented by Pretty Polly in 1968. It consists of a tube started at one toe and leg, with a wider body section in the centre, and terminated by knitting the other leg and toe. A slit is made down the wales on one side of the body section, which forms the opening for the elasticated waist section, whereas the other side of the body section becomes the under leg-crotch section as the tube bends into a banana shape.

Billi (Matec) modified this concept to achieve a better shape by introducing part course sections on the crotch side of the body section. This was combined with graduated sections of multiple tucks on a 1 x 1 knit/ tuck basis, which decrease in number towards the waist opening, which is a rectangle with a knitted-in elastic waist band. With this technique, a 'complete' panty-hose (pair of tights) can be knitted on a Zodiac eight-feed machine in approximately 3 minutes.

Other methods have involved reciprocation in the body section and in the case of the Samo Panty-Sol, one half of the waist band and panty is knitted in each of the two cylinders of a special double-cylinder machine; afterwards one leg is knitted in each cylinder with normal circular knitting.

The prototype GL one-piece tights system is the most recent development, taking 2 to 2- minutes to knit a pair of tights without closed toes. The Italian hosiery manufacturer Golden Lady holds the international patents and know-how to the GL one-piece knitted tights project (Fig. 21.6). The machine consists of two needle cylinders, each of 400 needles, and 4 feeds separated by a V-bed flat needle bed with 200 needles. It starts by knitting the two legs simultaneously, one on each cylinder. When knitting reaches the crotch portion, the body is knitted in tubular form on 1000 needles on all eight feeds, which includes the two cylinders and the V-bed.

In the standard 'made-up tights' there are only 800 needles in the body and a portion of this is cut-away during line-closing. The tights have a better fit and, being seam-free, are more comfortable. Single wale needle lines show in the body where the feeders pass between the flat and circular beds. Production rates are comparable with conventionally made-up tights but the cost of seaming machinery and labour is saved.

Fig. 21.6 GL one-piece tights. Production is started by knitting the two legs simultaneously. When the crotch portion is reached, the body is knitted continuously, in tubular form, either on the sets of cylinder needles or on the flat needle beds. This means that the leg portions are knitted with 4 + 4 feeders (4 feeders for each cylider) and that the body portion is knitted with 8 feeders throughout [Knitting International, Nov. 1998].

Fig. 21.6 GL one-piece tights. Production is started by knitting the two legs simultaneously. When the crotch portion is reached, the body is knitted continuously, in tubular form, either on the sets of cylinder needles or on the flat needle beds. This means that the leg portions are knitted with 4 + 4 feeders (4 feeders for each cylider) and that the body portion is knitted with 8 feeders throughout [Knitting International, Nov. 1998].

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