Knitting technology, Third Edition

19.5
Electronic controls replace mechanical controls
The electronically-controlled power flat machine offers quick response to size,
style and pattern changes with versatile and infinitely variable adjustment of its 
electronically-controlled functions under the guidance of the main computer soft-

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Knitting technology
ware programme and the back-up support of its memory. It is therefore more able
to efficiently meet the exacting requirements for knitting shaped garments [5].
In contrast, the mechanically-controlled power flat machine is time-consuming
and costly during machine changes and its more limited facilities provide less scope
for adjustment.
19.6
The garment sequence programme
The garment sequencing programme is the most important requirement of a
garment-knitting machine because it has overall control of the functioning of the
machine whose automatic operation follows the specified programme.
On mechanically-controlled power flats, it is the pasteboard movement-card
mechanism that provides the programme controlling and co-ordinating the
machine’s functions throughout the garment-length knitting sequence.
The positions of holes punched in the cards determine movement functions such
as yarn carrier selection, positioning of knitting cams, needle bed racking, and over-
all control of the jacquard mechanism.
The cards are expensive and time-consuming to assemble, shaping programmes
would require many extra cards and sequential knitting would require the equiva-
lent of four programmes – for the front, back and two sleeves.
19.7
Mechanical jacquard selection
Figure 19.1 illustrates the arrangement of elements in the needle bed of a machine
having full mechanical selection. A separately-controlled arrangement may also be
available on the other needle bed. In the tricks beneath each needle are selectors
(two in the case of the double-cam system machine) whose tails are supported by
a jacquard steel that extends across the full width of the needle bed.
There is a possible punched-hole position for each selector on every jacquard
steel. The steels are hinged together to form an endless ‘chain loop’ which passes
over the prism. The prism can turn whilst the cam-carriage is clear of the needle bed
at the end of its traverse. This brings another steel onto its upper surface and thrusts
it upward into contact with the protruding tails of the selectors. This produces a
simultaneous selection at every needle trick, ready for the next carriage traverse.
The prism can dwell to repeat a selection, or rack forwards or backwards by one or
two positions.
An unpunched portion in a steel causes the corresponding selector to be pushed
upwards in its trick, aligning its butt with a raising cam in the cam-carriage so that
eventually the needle above it will be lifted, possibly to knit. A punched hole allows
the selector tail to sink into the groove of the prism and thus be unaffected by the
thrust of the prism so that its needle is left at an inactive level.