Launching the Haute Horlogerie Constant Escapement collection, Girard-Perregaux presented the Constant Escapement, the result of over five years of research and development in the field of constant force, one of the highest goals for watch makers.
The principle of a constant force escapement is that whatever the energy supplied by the barrel, the escapement returns a constant energy to the regulator (balance wheel). To achieve this, they had the brilliant idea of integrating an intermediate device into the escapement, consisting of an extremely thin blade that stores the energy up to an invariable threshold bordering on instability, and then transmits it all instantaneously, before recommencing the cycle.
The inspiration came from an experiment, which anyone can repeat by holding a train ticket vertically between thumb and forefinger, bending it to form a C or an open round bracket. If you then apply pressure from the side you will feel resistance until the moment when the card snaps to the other side to mirror its former shape, and close the round bracket. Try it with a business card, it works every time. The video below gives a clear idea of how it works.
While silicon was the material of choice for its ideal properties in the design and manufacture of the blade, it may be replaced by other materials for escapement wheels, while the movement blanks are in brass coated in black PVD for a contemporary look.
The movement was designed to run for several days with a linear power reserve indicator on the dial, demonstrating the efficiency of this escapement in the long run. The energy is supplied by two barrels coupled in parallel (a new patented design): the cover and the ratchet are a single piece to maximise the thickness available and each drum contains two springs stacked in series.
The revolutionary movement is housed in a round 48 mm diameter case in white gold with a curved case band.
To offer maximum visibility to the escapement itself, with its butterfly wing frame and the vibrating blade in its central axis, the hours and minutes occupy a sub-dial off-centered at 12 o’clock. This is flanked by the two energy reservoirs in the shape of the double barrels. The power reserve indicator is placed at 9 o’clock.
The whole of the lower part of the watch is reserved for the Constant Escapement beating at the frequency of 3 Hz or 21,600 vibrations per hour. Under the anti-glare treated sapphire glass three bridges are visible and play their structural role in a novel layout.
This new manually wound calibre is 8 mm thick, while the case is 14.63 mm, with a wide open sapphire glass back held in place by 6 screws.
With its hand-sewn alligator strap and folding clasp, the model will be offered in Girard-Perregaux’s Haute Horlogerie collection.