In plan view, the identically Y-shaped chain links are similar in appearance to a tuning fork with the fork end leading. The tail of the preceding link fits into the fork of the succeeding link. The links are held together by pins that are pushed through holes in the sides of the fork and tail. The pins pass through all the tracks and chains, and the ends fit into grooves in the serrated flanges of the pattern drum so that as the drum turns, the chain links are advanced in unison in a correct timing relationship.
Chain links require accurate grinding at the fork and/or the tail if they are higher than the preceding or succeeding link, so that a smooth transition and an accurately-timed shog occur (the ground ends of two successive links must never be adjacent to each other). Too sharp a gradient will produce an early-timed shog and too gradual a gradient a late-timed shog for the knitting sequence. There are four types of link: plain unground, fork ground, tail ground and fork and tail ground.
With direct transmission of the shogging movement from chain links to guide bar, as described, the exact distance shogged is the difference in heights between the two successive links. This method is employed on most high-speed machines and on the ground guide bars of many multi-bar raschels.
A second method, indirect transmission, magnifies or adapts the thrust derived from the links by transmitting it through a pivoted lever whose leverage can be adjusted, thus altering the throw of the shog. This is a versatile method used on the pattern guides of multi-bar machines that enables links of one gauge to be employed for a range of machine gauges and also for arrangements that economise on chain links.
Chain link numbering commences with '0' height and every chain sequence must contain at least one of these '0' links. When the guide bar is on this link it will be in its nearest position to the patterning mechanism during that particular lapping movement. Tricot links are numbered 0,1, 2, 3, 4, 5, etc. With direct shogging, each successive number is one needle space higher than the previous link. On a 28-gauge tricot machine, a '2' link will be 1/28th inch higher than a '1' link, which itself will be 1/28th inch higher than a '0' link. If a '1' link is placed after a '0' link, a one-needle space shog away from the pattern mechanism will be produced. If a '0' link is placed after a '3' link, a three-needle space shog towards the patterning mechanism will occur. If two links of the same height are placed next to each other, for example a '3' followed by a '3', no shog will be produced and the guides will remain between the same needle spaces.
It must be understood that the height of a link, for example '0', does not represent a fixed position between two needle spaces because all the guides in the same guide bar will have been positioned by the same '0' link, but each will be between a different pair of needles across the knitting width.
For any guide, a '0' link is the nearest that guide will approach towards the pattern mechanism for that particular lapping movement repeat. Likewise, two guides in different guide bars may occupy the same space between two adjacent needles and yet be on different heights of links at that point.
A chain notation is a list, in correct sequence of chain link numbers, spaced into knitting cycles, for each guide bar necessary to produce a particular fabric structure repeat (Fig. 23.4D). The difference between the first two links is normally the overlap. It must be remembered that the links are joined together in a closed loop, with the starting link for each guide bar joined to its last link. For this reason, under-lap movements towards left and right tend to balance each other. It does not matter from which direction the chain numbering takes place (left or right) providing it takes place consistently from the same side for all guide bars in a particular structural repeat.
The number of links per course is fixed for each machine. A minimum of two is usually required, with the underlap occurring between the second link of one course and the first link of the next. On tricot machines, a third intermediate link is often used so that the underlap is also spread between the second and third links, giving it more time and coinciding more closely with the knitting cycle requirements.
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