(175) Another form of apparatus recently introduced by Mr. Thomas Knowles is the one shown in Figs. 95 and 96. In this case the boss of the loose pulley =L= carries a pinion =J= inside the pulley which gears with =I=, fixed on a short shaft borne by a central plate. Through the train of wheels =H G F E C= and =B= the central pinion =A=, fastened on the inner boss of the fast pulley =M=, is revolved. Over the central plate, in which the spindles on which the wheels =E F G H= and =I= are fixed, are fitted, a band =K= is passed. By tightening the latter the plate can be prevented from revolving. In grinding, the strap is moved on to the loose pulley, the band =K= is tightened, and the revolution of the pulley gives motion to the whole of the wheels, thus reducing the ultimate velocity to the required extent. During work the band =K= is slipped off the plate, and the whole nest of wheels is carried round with the pulleys as they revolve.
(176) The rollers used for grinding the cylinder and doffer are made in two forms. One of these is shown in Fig. 97. It consists of a light roller made with a thin wrought iron shell secured upon a shaft, running in brackets fixed to the frame side. The driving pulley is fastened at one end, and at the other is a traverse arrangement, consisting of an eccentric rotated by a worm on the shaft. By means of a short rod the revolution of the eccentric gives a small lateral movement—about an inch—to the roller during the whole time it is in motion. The surface of the roller can be covered with emery in the ordinary manner, and is either made plain or grooved. Another method adopted by Messrs. Dronsfield Brothers, is to wrap round the roller a narrow fillet of emery cloth, either plain or grooved as desired. In covering, one end of the fillet is passed into the slit Fig. 98, and is then secured by the clamp shown. About half of the width of the fillet is left projecting, and after it is secured, it is wound on by revolving the roller. As soon as the fillet is wound its loose end is passed into one of the three slits Fig. 99, formed at the other end of the roller, and is secured by the clamps. The ends are then trimmed off, and the roller is ready for its work. The grooved covering is preferred by many carders, as it is found to grind the wire teeth better, and to meet the various requirements of the trade it is made in various degrees of fineness. Three of these are shown in Figs. 100, 101, and 102, the coarser of the three being used for mild steel or iron wire, and the finer variety for hardened and tempered wire. All the rollers are carefully made, so as to be evenly and truly balanced, and great care is taken to ensure them having a perfectly true surface on which to wrap the filleting. This method of covering rollers has a good many advantages, the chief of which is the ease with which the operation can be conducted as compared with the older method of covering.