History of the Typewriter

Forfatter: Geo. Carl Mares

År: 1909

Forlag: Guilbert Pitman

Sted: London

Sider: 318

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-38- movement, actuated by a spiral spring, G, for imparting the rapid movements to the type-wheel ; now, to cause the partial or complete rotation of the type-wheel a most ingenious system of universal bars, I, arranged one within the other, twelve in all, six being placed each side of the type-wheel gear. These bars rest upon the ends of the key-levers, which are notched so as to raise its universal bar, and, since there are thirty-six characters, it follows tha^ each universal bar is responsible for three characters being brought to the printing point. Resting upon each universal bar is a small hammer, H, whose shaft converges from a slotted ring, it is the inner extremity of the hammer shaft (which is oscillated by a depression of a key and universal bar) which governs the partial or complete revo- lution of the type-wheel; for instance, suppose we depress a key, the hammer is tilted and thereby rocks its inner extremity inwards, and the same operation simultaneously releases the spur-wheel pallet, and, the type-wheel being free, its spring causes it to rotate rapidly, but since there is a projection on the type-wheel shaft, it is immediately arrested by the hammer-shaft projection, and the striking hammer, J, lets fly against the type, leaving an impression upon the paper attached to the line-frame, K. Upon releasing the key, the projection resumes its normal position and the pallet having engaged with the spur-wheel, the type- wheel is necessarily stationary until the depression of a another key. Above and across each key-lever towards the front of the machine are two oscillating bars (before mentioned) across which at right angles, is a lever, L, which is automatically raised by the depression of the key; each oscillation of these bars raises the type-wheel the necessary distance, that is, to the second or third rows of type on the type-wheel, and to assist in a rapid return of the type-wheel, a flat spring, M, is constantly pressing on the top of the type-wheel shaft. The lever for raising the type-wheel may be compared with the shift-key levers embodied in the construction of the “ Hammond ” type- writer, and the small hammer-headed like projection to the stop or index pins which, by means of the stop arm (also identical in the Pratt and Hammond machines), which arrests the movement of the type-wheel immediately the requisite type has been brought to the proper centre. “ Second, the impression is effected by a hammer, J, having a face equal in extent to a single type, which face is covered with a strip of ivory, backed by a small spiral spring so as to break the force of the blow ; this hammer