The Co-axial escapement...
...or, return to Watch Escapements.
Click on the Image to see the Animation.
... an Octal Escape-wheel - probably for a heavy balance beating 14,400 A/h (2 Hz.)
The amplitude of the balance is limited here, for clarity - normally it would be at least 270°
Escapement sequence: Click to enlarge images.
1/. The balance is towards the limit of its excursion, towards the right.
The octagonal escape-wheel is retained by the upper detent.
2/. An elliptical pin on the balance roller enters the fork in the detent lever and begins to disengage the upper detent.
3/. The co-axial star wheel leads the detent lever across, ready to engage the lower detent.
This also provides security - one or other of the detents must always block the escapement - for a 'run-away' 'scape wheel will invariably be wrecked...
4/. The lower detent is engaged, and the balance continues its excursion freely.
5/. As the balance returns the detent lever is led to the left, releasing the lower detent...
6/. ...allowing the escape-wheel proper to give an impulsion to the balance.
7/. As the impulse pallet leaves the wheel, the upper detent re-engages - the cycle begins again.
The escape wheel is driven by a toothed wheel (not shown) which engages with the foremost impulse wheel.