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THE LEVER / ROCKER

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1. General description

The lever / rocker belongs jointly to the winding mechanisms and the time setting. It is the element that allows switching the control of the Winding stem between these two mechanisms. It is a lever pivoting on a stud driven into the Main plate at its end. The other end of the Lever / Rocker is housed in the Groove of the Sliding pinion. When actuated, it forces the sliding pinion to slide along the winding stem in order to switch from one function (winding) to the other (setting the Time) and vice versa.

Figure 1

Diagram of a Lever / Rocker (winding – setting the Time)

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Figure 2

Lever / Rocker between the winding mechanism and the setting mechanism

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2. History

The Lever / Rocker appears in 1847 with the invention of the winding mechanism with Lever / Rocker by Antoine Le Coultre, of which it is the central element. It has since made it possible to switch the control of the Crown between the winding mechanism and the time-setting mechanism, at the very least. The major developments made to Le Coultre’s invention have consisted in multiplying the functions adjustable via the Crown. As a result, the function of the Lever / Rocker and its profile can be more or less complex.

3. Handcrafted manufacture of a Lever / Rocker

The Horologist (watchmaker) begins the handcrafted manufacture of the Lever / Rocker by engraving its profile using a scribing point on the surface of a plate of Steel slightly thicker than the finished component. He then marks the drilling point for its screw and the pivot point. Then he carefully cuts the outline of the Lever / Rocker using a piercing saw (jeweler’s saw). The sides of the piece are then filed to bring the Lever / Rocker to its final thickness while strictly respecting its shape. The Lever / Rocker is then beveled and polished using the usual tools (files, cabrons, Polishing). According to the rules of the craft, the artisan then draws out the lines along the sides of the piece (Satin finish) as well as the tiny flat surface remaining on the upper face of the Lever / Rocker.

When the Lever / Rocker is close to its final dimensions, the Horologist (watchmaker) adjusts the function that links the Lever / Rocker to the Setting lever by pre-assembling the two components to the Main plate. More than a dimension on a drawing, this is typically an action for which the craftsman’s eye and hand remain the best tools. The Heat treatments and whitening operations follow, and the Lever / Rocker is then ready to be assembled.

4. Semi-industrial manufacturing of a Lever / Rocker

To optimize the production costs of a single piece or a small series of components, Electrical discharge machining (EDM) is particularly interesting here. The implementation costs and machine Time remain relatively low and suited to small production volumes. Moreover, this technology allows complex and thin profiles to be cut without exerting any mechanical stress on the component during its manufacture. Compared to the traditional (handcrafted) method, Electrical discharge machining (EDM) cutting offers a considerable Time saving with good repercussions on the Decoration steps. The end of the manufacturing and Decoration process resembles the traditional method, particularly in terms of the required level of finishing.

5. Industrial production of a Lever / Rocker

Large-scale production justifies investing in a stamping die (striking tool) to manufacture Levers / Rockers at an optimal cost. The enlarged contour of the profile is thus punched directly into a strip of Steel of a thickness slightly greater than that of the finished component using a stamping press. Manual steps nevertheless remain unavoidable. The Lever / Rocker must thus be brought to its final dimensions (profile and thickness) while giving it the finishes and decorations desired (satin finish, beveling / angling etc.).