Rieter

Possibilities for cleaning

Index

The available possibilities for cleaning natural fibers can be divided broadly into three groups:

  • chemical cleaning;
  • wet cleaning (washing);
  • mechanical cleaning.

This discussion will be confined to mechanical cleaning, in which usually only particles on the surface of the flocks can be removed.

The following procedures can be used:

  • striking = falling out;
  • beating = ejecting;
  • scraping = separation;
  • suction = separation;
  • combing = extracting;
  • use of centrifugal force = ejecting.

Striking, carried out by pins, noses, etc., on the  Type and degree of openingopening devices<//a>, leads to repeated collisions of the flocks with the grid-bars, causing foreign particles to drop through. In a beating operation, the flocks are subjected to a sudden strong blow. The inertia of the impurities, accelerated to a high speed, is substantially greater than that of the opened flocks owing to the low air-resistance of the impurities. The latter are hurled against the grid and, because of their small size, pass between the grid-bars into the waste box, while the flocks continue around the periphery of the rotating beater. Impurities can be scraped off when the fibers are guided, under relatively high friction, over machine components, grid-bars, mote knives, or even other fibers.

This operation is chiefly of importance in dust removal. Suction is less suited to the elimination of coarse particles than to extraction of dust. Transport air is fed through filters or perforated sheets; the small dust particles, which have been released during beating or transport, pass with the air through the fine openings. The flocks cannot pass.

In combing, needles pass completely through the body of fibers and draw impurities out of the inner regions. This is the only form of mechanical cleaning in which regions other than simple surfaces are cleaned.

Genuine exploitation of centrifugal force, in which there is no need for beating, is achieved, for example, in the card. Because of their high ratio of mass to surface, when compared with the fibers, the dirt particles are thrown out into the flats while the fibers are retained in the clothing by the air current. This system was used still more intensively in the “air stream cleaner” from the former Platt company (Fig. 28). In this machine the transport flow of air and stock (A) was subjected to rapid acceleration (V) before the transport direction was sharply altered, i.e. by more than 90° (E). The flocks were able to follow the diversion but the heavier impurities flowed straight on through a slot in the duct into a waste box (C).

However, as impurities have become smaller and smaller in recent decades, this system does not function any longer – it has been abandoned.

Fig. 28 – Former Platt air-stream cleaner