History of the Typewriter

— 54 — to the other, and which is continuously turned in one direction by the rotation of the drum containing the main- spring. The bevel wheels, W W, are arranged on the shaft as shown, so that they cannot both be in gear at the same time. When one is in gear, the ribbon will move one way ; and when the other is in gear, it will move in the reverse direction. The reversal of the direction of the ribbon must take place just at that moment when the ribbon is entirely wound off from one of the spools. To effect this there is a worm, K, on the shaft at each end, opposite the axis of the spool. When all the ribbon is unrolled from one of the spools a weighted lever, L, which normally lies in a recess cut in the face of the spool, being kept in place by the ribbon wrapped over it, falls out as shown, and in so doing forces Fig. 38 out of the end of the shaft a small spindle or pin which runs along the centre of the spool shaft. This pin engages with the worm, K, and the continuous rotation of the shaft thus pulls it along in the direction of its own length until the bevel wheel at that side is in gear. Ihis automatically reverses the direction of winding and the weighted lever again falls into its recess, withdrawing the pin from the worm, and the ribbon is again wrapped over it. Ihe same thing happens at the appropriate time at the other end. The transverse motion is brought about by the stud, Q, which, as the shaft rotates, very gradually turns a cam, which pushes the ribbon frame seen in the figure, backwards and forwards, and slides each spool along its shaft. In order to illustrate the inkpad system we present a view of the typeblock of the Williams resting in its pad. This sim- plifies the machine to a great extent, since it obviates the