The new AP escapement
sorry for beeing so late with this - but finally here's a bit more info about the new escapement.
As already said it's a single impulse design based on the Robin escapement created in 18th. century. "Single impulse" in this context meaning that the balance wheel receives only one impulse through an entire oscillation. Or differently said it's impulsed only at one half beat, the other half beat is without an impulse. This principle was and is considered to have positive influence on the oscillators performance and precision, as an impulse also means "disturbation" at the same time (as is the unlocking).
So, "single impulse" in the physical sense means less disturbations for the oscillator. The traditional swiss lever escapement performs with double impulse - and of course the former inventors also had good reasons. As nothing is really ideal in real world, the obviously great advantages of the single impulse designs (among those also the famous detent and pivoted detent escapements) had their share of problems when carried and moved around. At the end all those escapements were considered less than ideal for all watches underlying more or less strong movements (such as pocket watches, wrist watches were considered almost impossible).
That's where AP and AP R&P started more than 6 years ago, inspired by the ingenious invention of Rober Robin, a single impulse escapement with a sort of anchor element:
Just to show the difference, here's a classical spring detent chronometer escapement:
I'll try to describe the main difference between those two escapements. Both are single and direct impulse, direct in this context describing the fact that the impulse is delivered directly from escape wheel to balance (without any connecting element, like with other lever escapements).
The spring detent (as the pivoted detent as well) is unlocked, the escape wheel delivers impulse to the balance wheel impulse jewel and than directly returns to its locking position. Therefore it always needs a returning force, mostly a spring (it should be noted here that there are some more exotic detent escapements sourcing the return force by the escape wheel as well).
The Robin escapement unlocks, the impulse is delivered the same way as with a detent escapement, but, as the anchor has two locking jewels it remains in the same position where it went after unlocking (i.e. it doesn't return to the initial position before unlocking like the detent). Now, on it's way back the balance wheel unlocks
again, but no impulse
is given! It may appear as potentially less efficient, but apparently there are good reasons for it as well.
Here's a drawing shówing the important parts of the new AP escapement:
As you may see through comparison with the original Robin design above, the AP escapement is quite different. The anchor is extremely compact (a similar developement can be observed with almost all lever escapements over the time) and the guard pin design is completely different - a point which well can be considered as major!
Here's a detail view of the AP safety guard pin - not really a "pin", more an adjustable "hook". The former "safety roller"now is a "cup shaped" piece with a small cut out allowing the guard pin to enter/pass for unlocking.
I'll have to continue later now - but maybe even this is at least of some interest
p.s.: Please forgive any errors, typos... I'm writing this out of the top of my head and under less than ideal conditions -