The fall-plate loop is achieved by a mechanism (Fig. 27.2) exclusive to latch needle raschel machines, although a similar effect to fall-plate loop structure, termed plaiting, can be achieved on crochet machines by wrapping a loop below the chain loop on the latch of the needle as it is moving out to clear.
In both arrangements, the fall-plate loop slips from the open lap immediately after formation and joins the technical back of the old loop from the previous course without being pulled through it.
The fall-plate is a thin metal blade attached to a bar and extending the full width of the machine. It is mounted between the guide bars and is attached to the guide bar brackets so that it makes the same swinging movement but it also achieves a vertical upwards and downwards movement described by the American term 'chopper bar'. The vertical movement of the fall-plate can be obtained from a pot cam on the main cam-shaft and is adapted through linkages.
Figures 27.3 and 27.4 illustrate the action of the fall-plate. The raschel knitting action is normal; the guide bars swing through the needles as they rise, then shog for the overlap and return to the front of the machine. The fall-plate descends, contacting the threads from guide bars in front of it as they pass onto the latch of the needle.
As the fall-plate descends, it causes the overlaps formed by those threads to be pushed downwards and off the latches, to join the loops of the previous course. They are knocked-over with them whilst the overlaps of the guide bars behind the fallplate remain unaffected in the hooks of the needles, ready to form the next course.
As the needles rise after knocking-over, the fall-plate is lifted to its high, inoperative position where it remains until the next knitting cycle.
It is necessary to knit the ground structure overlaps on the guide bars behind the fall-plate because these are unaffected by its descent. Every needle must receive at least one ground structure overlap. It is preferable to overlap the fall-plate yarn in the opposite direction to the ground overlaps as this is less likely to cause the ground overlaps to be lower on the needle stems and thus to be pushed off the latches as the fall-plate threads are pushed down.
As fall-plate yarn is not knitted by the needle hook, fancy or heavy yarns may be used in partly- or fully-threaded guide bars. Fall-plate designs use either open or closed lap movements to produce attractive relief designs whose overlaps as well as underlaps show clearly on the technical back, often as 'cup handle' shapes (Fig. 27.5).
Fig. 27.4 Fall-plate lowered into action.
The connection of the fall-plate pattern yarns to the ground structure is peculiar to its design (Fig. 27.6). The loop is held down at the technical back of the ground underlap of the course above, as well as by the underlap of the course at which it appears.
The fall-plate underlap floats loosely across the fabric up to its next overlap. The overlaps appear at the course previous to that at which they were formed.
Multi guide bar machines having fall-plate pattern bars controlled by an auto matic overlap are used to produce three-dimensional 'embroidery' or 'broche' relief designs in lace, particularly for curtains. These pattern bars will be positioned at the front of the machine whereas the ground guide bars will be placed behind the fallplate, and any inlay pattern bars will be placed behind these bars.
A fall-plate raschel termed the Co-we-nit was introduced by Karl Mayer in 1967. It was designed specifically to knit a woven-like structure. Despite arousing considerable interest, it was commercially unsuccessful for the following reasons:
The machine produced two separately-timed overlap actions, one for knitting the pillar stitch of the front bar, the second for the weft bar behind it that open laps in the same direction. The weft bar open laps are then pushed from the needle hooks by the fall-plate so that they appear to be an inlay. The two back guide bars, gauged twice as fine as the needle bar, provide vertical warp threads that 'interweave' with the fall-plate weft yarns, using carefully arranged evasion and miss-lapping movements. A half-needle space evasion movement can cause only one of the two threads of the warp bar to cross over the weft on the technical back of the structure, which is the effect side.
Was this article helpful?