DISCONNECTING GEAR

Disconnecting gear is the action, or the mechanism, allowing the transmission of Movement and energy between two components of a kinematic chain to be interrupted — the opposite of Coupling, which links them together. It consists of separating a Train (wheel train) from its drive source so that it ceases to be driven. The most familiar example is the Winding stem: by pulling or pushing the Crown, the winding mechanism and the time-setting mechanism are alternately engaged and disengaged, so that a single stem controls two functions. Disconnecting gear also comes into play in the Chronograph, whose mechanism is disconnected at rest, and in various devices with activatable functions. It is generally based on a Lever / Rocker or a coupling that separates two wheels. The smoothness and reliability of the disconnecting gear are important: an incomplete or abrupt disconnection can cause jumps of the Hand, wear, or malfunction. Coupling and disconnecting gear thus form the pair of controls that governs the engagement of the mechanisms.