Fig. 206.

Fig. 207.

Fig. 208.

A "compensating" watch balance, at normal, super-normal, and sub-normal temperatures.

KEYLESS WINDING MECHANISM FOR WATCHES.

The inconvenience attaching to a key-wound watch caused the Swiss manufacturers to put on the market, in 1851, watches which dispensed with a separate key. Those of our readers who carry keyless watches will be interested to learn how the winding and setting of the hands is effected by the little serrated knob enclosed inside the pendant ring.

There are two forms of "going-barrel" keyless mechanism—(1) The rocking bar; (2) the shifting sleeve. The rocking bar device is shown in Figs. 209, 210. The milled head M turns a cog, G, which is always in gear with a cog, F. This cog gears with two others, A and B, mounted at each end of the rocker R, which moves on pivot S. A spring, S P, attached to the watch plate presses against a small stud on the rocking bar, and keeps A normally in gear with C, mounted on the arbor of the mainspring.

Fig. 209.—The winding mechanism of a keyless watch.

To wind the watch, M is turned so as to give F an anti-clockwise motion. The teeth of F now press A downwards and keep it in gear with C while the winding is done. A spring click (marked solid black) prevents the spring uncoiling (Fig. 209). If F is turned in a clockwise direction it lifts A and prevents it biting the teeth of C, and no strain is thrown on C.

To set the hands, the little push-piece P is pressed inwards by the thumb (Fig. 210) so as to depress the right-hand end of R and bring B into gear with D, which in turn moves E, mounted on the end of the minute-hand shaft. The hands can now be moved in either direction by turning M. On releasing the push-piece the winding-wheels engage again.

The shifting sleeve mechanism has a bevel pinion in the place of G (Fig. 209) gearing with the mainspring cog. The shaft of the knob M is round where it passes through the bevel and can turn freely inside it, but is square below. On the square part is mounted a little sliding clutch with teeth on the top corresponding with the other teeth on the under side of the bevel-wheel, and teeth similar to those of G (Fig. 209) at the end. The clutch has a groove cut in the circumference, and in this lies the end of a spring lever which can be depressed by the push-piece. The mechanism much resembles on a small scale the motor car changing gear (Fig. 49). Normally, the clutch is pushed up the square part of the knob shaft by the spring so as to engage with the bevel and the winding-wheels. On depressing the clutch by means of the push-piece it gears with the minute-hand pinion, and lets go of the bevel.