Paper Making and Its Machinery; Including Chapters on the Tub Sizing of Paper, the Coating and Finishing of Art Paper and the Coating of Photographic Paper (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...papermakers will not resort to this method of quickly removing all trace of the bleach from the pulp. The chief source of trouble is, however, a mechanical one. The cloth is driven by the lower couch roll, and in passing between these rolls and round the breast roll, &c, is bound to wear in time. If the wear were even all over its surface, its destruction from this cause would occupy a fairly considerable time. But it is not even. However carefully the cloth is handled and looked after, it cannot altogether escape being slightly puckered in places. The ridges developed may be very small and short, but they will receive a greater proportionate amount of wear than the rest of the cloth, and sooner or later they will be worn through. Skilful darning may enable the life of the cloth to be prolonged, but it is from the development of holes that the majority of wire cloths perish. Such holes do not mean simply that more fibre than usual is lost in the back water draining away from the cloth; the danger of their presence arises from the fact that they allow the fibre to come into direct oontact with the metallic surface of the lower couch roll. The spot of fibre then clings to the roll and holes and rents in the web of paper result. If we take a portion of wire cloth and pour a little water over it, we will find that capillary attraction holds up nearly the whole of the liquid on the top of the cloth. In practice this effect is overcome in great measure by the action of the large number of small tube rolls, on which, as we have seen, the working stretch of the wire cloth Wire 500 ft /min. Fig. 65. Action of Tube Roll. is supported. These tube rolls are rotated by the movement of the cloth, and on close examination it wall be found that from the forward side of...