The application of microprocessor controls has removed the need for mechanical timing chains and control drums on the latest electronically-controlled hosiery machines. The machine's microprocessor memory can accommodate a range of sizes and styles that can be quickly recalled when a change is required.
On mechanically-controlled machines, the changes are timed by the links of a timing chain that also control the racking of a control shaft to which are attached the control cam-drums and wheels that initiate the major mechanical machine changes (Fig. 21.3).
One complete racking of the chain together with one complete revolution of the control shaft is necessary to produce the length knitting sequence for each hosiery
article. Plain links are used purely for providing knitting time between changes whereas movement links have projections or studs to initiate mechanical changes, usually as a result of racking (turning) the cam shaft and its cam drum. Chain saver links have a pin that turns an economiser wheel, saving 23 plain links.
The control cam drum revolves with the control shaft and is divided into a number of tracks, each corresponding to a lever or rod that scans its section. Amongst functions that may be controlled from the tracks are: speed changes, knitting cam changes, pickers, the verge, take-down splicing, and pattern drum racking.
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