Rieter

Purpose and effect of carding elements

Index

If carding elements or additional  lickers-in are not used, the licker-in delivers mostly tufts, if not whole lumps, to the main cylinder.

These are compact and relatively poorly distributed across the licker-in. If they pass into the space between the cylinder and the flats in this form, fiber-to-fiber separation becomes very difficult and imposes considerable loading on the clothing. The whole carding operation suffers.

That is why high-performance cards presuppose unconditionally individual fibers to be spread evenly over the whole surface of the cylinder, and this again can be obtained only by increasing the number of lickers-in and the inclusion of carding elements, since they ensure further opening, thinning out and primarily spreading out and improved distribution of the fibers over the total surface area.

In the final analysis, these additional devices reduce the loading on the carding zone cylinder/flats, among other things. Two diagrams (Fig. 104 and Fig. 105) by Schmolke and Schneider  [10] illustrate loading of the  flats with and without carding segments; in addition, it is clear from these diagrams that the main opening work is done at the first flats after entry of the material. Carding segments bring the following advantages:

  • improved dirt and dust elimination;
  • improved untangling of neps;
  • the possibility of a speed increase and hence a production increase;
  • preservation of the clothing;

and hence

  • longer life of the clothing, especially on the flats;
  • the possibility of using finer clothing;
  • better yarn quality;
  • less damage to the clothing;
  • cleaner clothing.

Even  carding elements following the  flats exert a considerable influence on yarn quality – although the main carding work has been completed at that stage. This is shown in a diagram by Artzt, Abt and Maidel in Fig. 106  [11]. The segments create an additional fine carding zone as the fibers rotate 5 to 10 times with the cylinder before they pass to the doffer. This additional treatment of 5 to 10 times at the segments also improves both fiber orientation and transfer of fibers to the doffer.

Fig. 104 – Carding effect in the flats in cards without additional carding segments: A, carding effect (carding force); B, number of the flat starting from the entry point.

Fig. 105 – Carding effect in the flats in cards with additional carding segments over the licker-in; A, carding effect; B, number of the flat starting from the entry point.

Fig. 106 – Improvement in yarn properties through the use of carding segments following the flatsA, comparison values related to cards without carding segments (100%); I, neps; II, thick places; III, thin places; IV, yarn evenness; V, tenacity; a, main cylinder clothing: 430 points per square inch; b, main cylinder clothing: 660 points per square inch; c, main cylinder clothing: 760 points per square inch.