SJX Watches
Explained: The Horizontal Clutch of a Chronograph
The chronograph is an on-demand complication, as its operation requires the user to active the function. As such, the chronograph, or more accurately a stopwatch, engages selectively with the going train of the watch. The chronograph wheel couples with the going train when engaged and uncouples when stopped or reset. The mechanism which makes this selective engagement possible is the clutch. Arguably the most classical form of clutch is the horizontal clutch, also known as a lateral coupling. As suggested by the name, the coupling action takes place horizontally, with the clutch arm moving on a plane parallel to the movement. Because the mechanism is spread out laterally, it results in an intricate display of mechanics, which is one reason why the lateral coupling is desired by many enthusiasts. A eminently classical chronograph construction in a mid-20th century Patek Philippe ref. 530 How it works The fundamentals of the horizontal clutch are outlined in Figs. 1 and 2. Gear R1 is fixed to the seconds’ mobile, on the same axis, above the going train. The same mobile conveys the turning motion from the going train, and may carry the small seconds hand on the dial side. The clutch arm pivots on the same axis as R1 and carries an intermediary clutch wheel R2. In Fig. 1 the column wheel or cam (not shown) keeps the clutch uncoupled with the intermediary wheel R2 idling. In other words R2 is turning but not driving anything. Fig 1. Image – Patek Philippe patent EP1437...
