Production of heels and toes

Three-dimensional 'turned' heel and toe pouches (Fig. 21.4) are knitted in plain so that, in the case of double-cylinder machines, the heel section needles must be transferred down to knit from the bottom cylinder. A spring take-up holds the surplus yarn as the needles traverse towards the feed on the return oscillation, whilst a pouch tension equaliser ensures that the pouch fabric is held down on the needle stems.

The pouch is preferably knitted in single feed so that the other feeds (if there are any) are taken out of action, but an additional splicing yarn is striped in for reinforcement. The shape and extent of the spliced section may extend beyond the pouch. Reciprocation of the cylinder is produced by the drive at this point, being taken from the forward and backward oscillation of the quadrant. As the changeover is mechanically complex, oscillatory knitting takes place at approximately two-thirds of the speed of circular knitting.

In socks with reciprocated heels and toes in single feed, over a third of the courses will be in oscillatory knitting and may require over 60 per cent of the machine's operating time, thus making this operation time-consuming and expensive.

During the oscillatory knitting of the pouch, the remaining needles (approximately half) are raised into a high inactive cam-track by the introduction of a cam. This operates only on the long knitting butts allocated specifically to them, so that they retain their loops (for the instep) from the last course of circular knitting.

During narrowing, the leading needle in each direction of oscillation is lifted up to join the other needles in the inactive track by the action of one of two side pickers

Fig. 21.4 Heel produced by reciprocation.

that are alternately in action according to the direction of oscillation. These pickers operate throughout the oscillatory motion.

During widening, a down picker is introduced that lowers two needles at a time, thus cancelling the effect of the up picker and putting an extra needle into action.

Each of the side pickers has an L-shaped recess and these are positioned facing outwards at the approach into the cam system so that in either direction of oscillation, the knitting butt of the leading heel needle or slider is caught by the recess. The continued movement of the cylinder causes the picker to be moved backwards and, as its movement is restricted, it pivots upwards in its holder to place the butt into the high inactive track; the spring attached to the picker then pulls it down again.

The down picker, when brought into action, moves down from the inactive track bringing two needles down with it each time. It has a recess on each side of its under surface so that two butts can be accommodated in each direction of oscillation. Lonati use only one type of picker, which is turned over to act as a down picker during widening. Some machines knit a twin-feed heel and toe. During narrowing two needles at a time are lifted. During widening, up picking continues with only one needle at a time whilst three needles are lowered into action at each side. With this method, a twin-feed heel or toe with acceptable sutures can be knitted in 22 seconds.

In the production of a standard small heel, half the needles knit in the heel-section, with narrowing occurring at each side, until only one-third of the needles are left in action. As each needle is lifted out of action, the yarn is automatically wrapped over it in the form of a tuck stitch, which makes the heel join stronger. Widening then takes place until all the heel section needles are brought back into operation, when circular knitting recommences.

A toe pouch is knitted in a similar manner. If the heel section needles are used again, the seam will be on top of the toe (as is the case in most socks). If the instep needles are used instead, a reverse toe is knitted, with its seam being underneath (usually preferable in hose).

Many modifications to the basic pouch sequence have been employed, particularly on hose, in order to improve the fit and appearance. In the Y-heel, extra fabric is knitted in the centre of the inverted Y suture-line by widening for twelve courses after narrowing to the one-third needles. Narrowing then occurs to one-third needles before commencing normal widening.

The gusset toe is a reverse toe knitted in a similar manner except that, when the one-third needles are left, a group are re-introduced collectively. Single-needle narrowing then occurs for twelve courses and then the rest of the needles previously collectively widened are lifted out of action and the normal widening picker is introduced. In the ballet toe, all the needles are brought collectively into action for a few courses of circular knitting after the needles have been narrowed to one-third. All except the one-third are then collectively raised out of action as normal widening begins.

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