The pattern wheel is a cheap, simple device occupying little space, and is unique in employing separate raising cams, in the form of pattern bits, to select and move individual elements, if necessary, to three different positions in their tricks (Fig. 11.9). It is most popular in single-jersey machines, either as an inclined wheel for needle or point selection, or as a horizontal wheel for plush sinker selection. The pattern set-out, which is unchanged during knitting, uses bits which are either re-usable and are inserted into the tricks, or are break-off teeth on pre-prepared discs.
The wheels, tricked to the same gauge as the revolving cylinder needles, are driven continuously in the opposite direction, either by the needle butts meshing with their tricks or by gearing from the cylinder.
The wheels are of the gain or loss type so they do not produce an exact number of complete turns in one machine revolution. The design areas can have a depth greater than the number of feeds, but are built up in a spiral manner, compared with the courses around the fabric tube.
The inclined pattern wheel, like all selection devices, is normally placed at each feeder. It is set at an angle of 20-40 degrees in place of the solid raising cam so that, as it turns, it lifts any element whose butt rests on a pattern bit. The needles will all have a butt of the same size in the same position.
With a three-position wheel (Fig. 11.9), a needle entering an empty trick will remain at miss height (3), a needle supported by a low bit will be lifted to tuck (2), and a needle supported by a high bit will be lifted to clear (1). Needles left at miss height are lowered by a wing cam (X) to ensure that they do not inadvertently receive yarn.
Some machines have four-finger striping selection available at each feeder wheel, which considerably increases the pattern depth and scope. Another mechanism often used in conjunction with striping is a pattern placer, tuck bar, or pattern-cancellation device, which is a moveable raising cam, usually acting onto a butt at a level lower than the pattern wheel. When the cam is raised into action, it causes
all needles to be lifted to knit and thus cancels the selection for a number of courses so that alternating bands of design and plain single colour may be produced.
Alternative methods of needle selection with higher productivity, less restrictive pattern areas, and quicker pattern-changing facilities have replaced the pattern wheel as the most popular method of pattern selection.
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