The turned welt of doubled plain fabric that is produced on stocking frames is usually less acceptable for the start of a garment panel - a rib border is often preferred. Straight bar rib frames have been built but they have proved to be complex and uncompetitive against faster and more versatile V-bed rib flat machines.
A popular technique is to knit the rib borders or cuffs on a specific-purpose
V-bed flat machine and then to transfer them, using the last required course, loop-by-loop onto the points of a special 'topping-on bar' ('running-on').The fabric is then transferred onto the needles of the straight bar frame ('barring-on'). Six ribs may be transferred at a time but only the topmost is placed on top of the knocking-over bits and underneath the sinkers, ready for knitting the plain onto it. It is a common practice to employ 'doubling', i.e. to have more wales in the rib than in the plain so that, during running-on, two rib loops are sometimes run onto the same points. In this way, the rib is in a more relaxed state and gives a better fit.
Rib transfer has been automated by using a conveyor to transport loaded rib transfer bars from one end of the machine to the individual knitting heads (Fig. 17.1). Each bar is transferred to the holders of the automatic rib transfer mechanism, in readiness for rib transfer at the start of the next garment cycle. Arms then advance the rib transfer holder and present the new rib to the needles. Empty bars are replaced on the conveyor, which automatically returns them to the loading station for refilling.
This operation has reduced standing time from an average of five minutes to a matter of a few seconds and has enabled the knitter to supervise more knitting heads. At the start of knitting on the straight bar frame, an initial draw-off engages the ribs or welt rods whilst sufficient courses are knitted for them to be engaged by the main draw-off arrangement.
Special V-bed flat machines have been designed for automatic rib knitting and magazine bar loading. A four-head machine can knit an average body rib in 1 min 25 sec at 60 courses per minute (cpm), or in less time without doubling. The machine is pre-programmed to knit a cotton course, which is taken by the hook-up bar of the take-down mechanism, followed by the tubular welt and rib in 1 x 1,2 x 1 or 2 x 2.
On completion of the rib, a separate mechanism actuated by a cam on the main cam-shaft causes the front bed loops to be transferred to the back bed. A transfer bar then descends to collect these loops and transfer them onto the points of the magazine bar. A maximum of sixteen ribs can be accommodated. Doubling on every seventh needle on a 14npi machine can be achieved, if desired, for a 21G garment.
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