The major innovation introduced in the DualTow is its single-pusher chronograph function operating by means of three identically structured planetary gears.
Directly linked to the movement, the continuously driven planetary-gear entry wheel (1) is connected to a satellite-holder (2) pivoting on the arbor of the entry wheel which bears two satellites (3) rotating in turn. Placed on an axis parallel to the entry wheel, the latter mesh with the exit wheel (4) located in the upper part of the satellite-holder. At the top, a cam (5) surmounted by a hand (6) is fixed to the same arbor as the entry wheel, connected to the exit wheel, and serves to reset the chronograph.
The entry wheel transmits its movement in two different ways. When the hand rotation is blocked, it drives the satellite-holder which then spins in the void. This operation corresponds to the chronograph stop and reset positions; whereas when the chronograph is in the start position, the satellite-holder is blocked and the rotating motion of the entry wheel is transmitted to the hand.
When the chronograph is activated, the column wheel (7) moves one notch forward and raises the reset hammers (8). The start brakes (9) then drop to block the three satellite- holders (2) and the hands (6) begin turning immediately, since the energy is transmitted from the entry wheels (1) to the exit wheels (4). A second push halts the running of the mechanism. The column wheel moves another notch forward and lifts the start brakes, which releases the satellite-holders. The stop brakes (10) then drop to block a disc connected to the hands. At the third press, the column wheel moves yet another notch forward and the stop brakes lift to release the exit wheel. The hammers then drop onto the cams (5) and cause them to rotate until the hands return to zero. The chronograph cycle is thus complete and the system is ready for another measurement.

FRANCAIS
