Pulsomax®, Ref. 5450 - Ron DeCorte
"Pulsomax®, Ref. 5450" - Ron DeCorte
The “Trilogy” is complete. In 2008, Patek Philippe unveiled the Ref. 5450 Annual Calendar wristwatch featuring the latest development from the Patek Philippe Advanced Research department, the Pulsomax® escapement. I say “Trilogy” since in 2005, Patek Philippe launched the Ref. 5250 Annual Calendar watch featuring their first high tech innovation the Silinvar® escape wheel, and again in 2006, launched the Ref. 5350 Annual Calendar incorporating the Spiromax® hairspring, also a Silinvar® innovation, in conjunction with the Silinvar® escape wheel.
The “missing” link. The watch escapements are the regulatory heart of the watch and there are three major components of importance: the escape wheel, the hairspring and the ancre (pallet fork). I’ve written previous articles on the Patek Philippe Ref. 5250 and Ref. 5350 and waited with anticipation for the past two years for the third innovation, the missing link, to be released. Now with the Ref. 5450 this missing link, the ancre, has been incorporated using Silinvar® and in my opinion the trilogy has been completed.
Escapements are peculiar beasts that strike fear into hearts of watchmakers and have been the subject of more debate and experiments than possibly any other subject in watchmaking. Allow me to explain. All mechanical watches need a power source, the mainspring, and as its name implies is the main source of power which keeps your watch ticking away. At the opposite end of the watch mechanism is the balance wheel that by virtue of the hairspring (which is directly attached) oscillates at a certain frequency (rate) acting as the heart beat of the watch.
The tricky part of the escapement function is the transfer of power to the oscillating balance wheel. In the lever escapement, which is incorporated within virtually every wristwatch of the past 100 years, it is the ancre (pallet fork) that is responsible for this very important “connection”. How the ancre receives power from the escape wheel, and how efficiently it makes the transfer of power to the balance wheel, is a key factor in the overall accuracy of the watch performance.
The conventional Swiss lever escapement shown here is comprised mostly of steel components including the escape wheel and pallet fork. It is the rotating escape wheel that provides energy from the mainspring to the pallet fork which in turn gives a small impulse to the balance wheel several times per second that keeps it oscillating. Two ruby, or in some cases sapphire, pallet jewels are fixed into the pallet fork to reduce friction with the escape wheel. For more than 100 years this combination of steel and ruby has changed little, until now.
The differences are obvious. Immediately you might notice that the Pulsomax® escapement in this drawing looks more robust and you might assume that it is more massive in terms of weight. Quite the contrary, since the Pulsomax® escapement is fabricated from Silinvar® which is 1/3 the density of the same steel components used in the conventional Swiss lever escapement. Also noticeable is the radical geometric design of the pallet fork, but we will save this geometry lesson for a future edition of Rendezvous when we can explore its technical merits in greater detail.

Speed is of essence. The Pulsomax® escapement components, being so much lighter than conventional steel components, are able to react much faster than their steel counterparts of the past, and thus the transfer of power between themselves and ultimately to the oscillating balance wheel is greatly improved. As well as being lighter and faster, the Pulsomax® escapement made of Silinvar® shares excellent anti-friction properties negating the need for lubrication (oil) that has been the detriment of all lever escapements of the past.