Rieter

Requirements

Index

In modern spinning installations the card is the first machine to deliver a cohesive intermediate product. Among other requirements, the product is expected to be very even and as far as possible free of faults. Irregularities in the sliver can be traced through into the yarn, at least in the spinning of carded yarns; that is, they diminish yarn quality.

A fault-free sliver cannot be obtained unless the feedstock is in an adequate condition, since every irregularity in the feedstock is transmitted completely into the sliver – in an elongated form owing to the draft. The time spent by the material in the machine is too short for total compensation. In spinning, as in any other type of manufacturing process, the rule must be that faults should not be corrected and hidden but their occurrence should be prevented from the start. It follows that the feed to the card must be very even. Where lap feed was used, this represented only a minor problem, since the scutcher formed even laps, each of which was checked for accuracy of count. Tuft feed systems react much more sensitively.

The tufts must be transported pneumatically from a distributor unit into the chutes of several cards. One of the cards is always located very close to the fan of the distributing system, whereas the others are located at steadily increasing distances from the fan. To obtain even feeding, the batts in the individual feed chutes of all cards must be equally thick, evenly distributed over the whole width of the chute and of equal density. This requirement cannot be fulfilled continuously without the expenditure of some effort. An additional requirement for the feedstock of high-performance cards is a high degree of openness. This very good openness in turn is the reason for the large increase in performance of this card in comparison with conventional machines. Higher loading of the clothing (600 to 900 ktex) permits greater throughput of material. Correspondingly finely opened material is therefore essential.