Mechanical Escapements

Contents

Anchor Escapement

• ​​Strip-Pallet Recoil (Metal Strip Type Escapement)
• ​Brocot Escapement (pin-pallet escapement)​

​​​Audemars Piguet Escapement
​​Coaxial Escapement
Constant Escapement
​Cross-beat Escapement
​​Cylinder Escapement
​​Daniel's Independent Double Wheel Escapement
​​Deadbeat/Graham Escapement
​​Detent/chronometer Escapement
​​Duplex Escapement
​Dual Direct Escapement
​Dual Ulysse Escapement
​Échappement Naturel (Breguet Escapement)
​Eleta Escapement
​Fasoldt Escapement
​Grasshopper Escapement

​Gravity Escapement
​Haldimann Escapement
Lever Escapement

• English Lever Escapement
• Glashuetten Lever Escapement
• Swiss Lever Escapement
• Mueller Lever Escapement

​​Pin Wheel/Amant/Mannhardt Escapement
​​Pin-Pallet/Roskopf/Pin-lever Escapement
​Riefler/Spring Pallet Escapement
​Robin Escapement
Spider Escapement
Strasser Escapement
Tic-Tac Escapement
Ulysse Anchor Escapement
Verge and Foliot Escapement
Würtz Escapement

Anchor Escapement

Original

• probably Robert Hooke, 1657 some credit William Clement who popularized the anchor escapement with his longcase clocks, 1680
• Standard for pendulum clocks
• Problem: swing of pendulum pushes escape wheel backward during part of cycle, recoil causes inaccuracy and reverses direction of gear train, causes backlash, high loads=friction and wear

Strip-Pallet Recoil (Metal Strip Type Escapement)

• Used in inexpensive clocks
• Bend strip of steel so that its ends form the R and L pallets
• Allows for manufacturing at low costs for labor and material

​Brocot Escapement (pin-pallet escapement)​

• Invented 1823 by Louis-Gabriel Brocot, improved by Achille Brocot, 1849
• Called “pin-pallet” but is really a variation of the anchor escapement
• nearly deadbeat, robust and reliable, but suitable only for half-second pendulums or shorter (large angular amplitude needed)

​Audemars Piguet Escapement

• Inspired by Robin escapement

Advantages

• Offered absolute protection against shocks through a “safety finger” mechanism
• Less moving parts compared to Swiss lever escapement
• Need for oil eliminated

​Coaxial Escapement

• George Daniels (1974, patented 1980) classifiable as detached, adopted by Omega (1999)
• Didn’t need lubrication (one of the main causes of degradation for timepieces)

​3 levels

• Level 1: balance wheel contacts pallet fork; guard pins
• Level 2: inner escape wheel w/ 12 teeth
• Level 3: outer escape wheel w/ 12 teeth
• Pallet fork is in contact with both levels of escape wheels

​Constant Escapement

• Nicolas Déhon (patent submitted by Rolex), developed by Girard-Perregaux, 2008
• in watches by 2013
• key component: silicon buckled-blade acting as micro-accumulator of energy

​Cross-beat escapement

​Jost Bürgi invented in 1584, variation of verge with two foliots rotating opposite directions

​Cylinder Escapement

• Thomas Tompion, 1695 and perfected by George Graham, 1726
• Replaced verge escapement in pocket watches after 1700
• Thinner than verge
• High end watches had cylinders of ruby
• mid-19th and 20th century, French made cylinder and escape wheel out of hardened steel solving problem of excessive wear

​Daniel's Independent Double Wheel Escapement

invented by George Daniels in 1974

​Deadbeat/Graham Escapement

• Design by Richard Towneley, made by Thomas Tompion, 1675
• Credited to Tompion’s successor, George Graham who popularized it in 1715
• Got rid of recoil, separated locking and impulse action of escapement

(a) Escape wheel
(b) Pallets
(c) Pendulum crutch

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​Detent/chronometer Escapement

• Pierre Le Roy, 1748 (early form) created pivoted detent type of escapement (theoretically deficient)
• John Arnold, 1775, created first effective design
• Thomas Earnshaw, 1784, modified it into spring detent which was patented by Thomas Wright (who he worked for)
• Final form in 1800
• 1779, John Arnold ad Ferdinand Berthoud had their own designs, but neither were as popular as Earnshaw’s
• Most accurate of balance wheel escapements, used in marine chronometer, more accurate than lever escapement

Function

• detached escapement, allows balance wheel to swing unperturbed during most of cycle except for brief impulse period (once per cycle or every other swing)
• driving escape wheel tooth moves almost parallel to pallet, escapement has very little friction, no need for oiling

​Problem: fragile, need skilled maintenance, not self-starting, hard to manufacture in volume

​Duplex Escapement

• Robert Hooke, 1700 and improved by Jean Baptiste Dutertre and Pierre Le Roy, final form by Thomas Tyrer who patented it in 1782
• Much higher accuracy than cylinder escapement, equaled early lever escapements, almost as good as detent escapement
• English pocketwatches 1790 to 1860 and American cheap ones 1880-1898 (Waterbury)

Function

• One impulse per cycle
• Escape wheel has two sets of teeth
• Known as a frictional rest escapement: tooth resting against roller adds friction to balance wheel during swing
• Little lubrication needed (little sliding friction during impulse)

Problem: lost to lever escapement due to sensitivity to shock, not self-starting

​Dual Direct Escapement

• Invented by Dr. Ludwig Oechslin and showcased in Ulysse Nardin Freak watch in 2001
• Inspired by Daniel’s independent double wheel escapement

​Dual Ulysse Escapement

• increased balance frequency from Dual Direct
• invented by Dr. Ludwig Oechslin in 2004
  

​Échappement Naturel (Breguet Escapement)

• Invented by Abraham Louis Breguet, 1802
• Only about 20 watches made with this escapement
• Advantage
  • solved problem of detent escapement stopping and not being self-starting and lubrication of lever escapement
  • doesn’t require oil
  • impulse produced close to dead point
• Two escape wheels geared together; one escape wheel driven by the fourth wheel of the wheel train which, in turn, was geared to and drives second escape wheel
• pivoted detent swings freely between escape wheels and locks each escape wheel on coaxial set of locking teeth 

​Eleta Escapement

​Created by Miki Eleta, 2011

​Fasoldt Escapement

• Invented and patented by Charles Fasoldt, 1859 (more like 1884)
• Impulse in one direction only

​Grasshopper Escapement

• John Harrison, 1722
• Pendulum driven by two hinged arms (pallets)
• Problem: wear out too quickly, waste too much energy

​Gravity Escapement

• uses small weight or weak spring to give direct impulse to pendulum
• double three-legged most popular

​Haldimann Escapement

• Beat Haldimann, 2000
• Combined properties of Graham and Strasser escapement
• Although very accurate, it was a century too late since the atomic era had begun
• Maintained 0.1 seconds per day

Lever Escapement

• Advantage: detached escapement, self-starting
• Cheap, less accurate form: Roskopf or pin-pallet escapement (Gearges Frederic Roskopf, 1867)

English Lever Escapement

• Thomas Mudge, 1755
• comprised of escape wheel, anchor-like pallet fork, balance wheel, hairspring

Glashuetten Lever Escapement

• Ferdinand Adolf Lange of a little town called Glashuetten, 1852)

Swiss Lever Escapement

• mid nineteenth century Switzerland
• probably team effort
• same parts as English version
• pallet shaped like fork: centered balance wheel, pallet fork and escape wheel aligned in one line making power transmission more efficient and stable

Mueller Lever Escapement

• Hugo Mueller, 1924, Glashuetten in Saxony
• Different design and type of banking pin
• Pallets were shorter
  • Supposed to have advantage of oil staying in place
  • (a little oil is filled in at locking face of entry pallet which then accumulates at front corner
  • (teeth of escape wheel constantly draw oil from “reservoir”)
• most important difference: allocation of impulse
  • impulse plane of escape wheel and pallets are never parallel
  • has advantage that adhesion at the impulse plane can not occur
  • adhesion depends on viscosity which rises when oil gets older which would have a negative effect on energy balance of escapement

​Pin Wheel/Amant/Mannhardt Escapement

• Louis Amant, 1741
• Version of deadbeat that can be made rugged since it uses round pins that are stopped and released by scissor-like anchor instead of teeth
• Often used in tower clocks

​Pin-Pallet/Roskopf/Pin-lever Escapement

• Patented by Georges Frederic Roskopf, 1867
• Cheap, less accurate form of Lever escapement
• Brocot escapement is a type of pin pallet

​Riefler/Spring Pallet Escapement

• Invented by German instrument maker Signmund Riefler in 1889
• Used in astronomical regulator clocks by his German firm Clemens Riefler from 1890 to 1965
• Improvement of deadbeat
• Riefler clocks achieved accuracy of 10 milliseconds per day, guaranteed to be within 30 milliseconds

​Robin Escapement

• Robert Robin, 1792
• Single impulse in one direction only
• inspired by both Swiss escapement and detent escapement
• extremely sensitive to shocks, very complex

​Spider Escapement

created by Phil Abernathy in Parry Sound, Ontario, Canada

Strasser Escapement

• Ludwig Strasser, 1900
• Impulse delivered from pendulum through spring to lever
• Pallet has very limited movement

Tic-Tac Escapement

Used in French drum clocks with a rigid pendulum

Ulysse Anchor Escapement

• circular silicone frame
• pallet arms are suspended by two buckled blades that are – curved under tension – one perpendicular to the other

Advantages

• no need for lubrication
• slimmer movement
• less loss of energy
• antimagnetic properties

Verge and Foliot Escapement

• Early large mechanical clocks (1275)
• first watches (shortly after 1500) with early examples made by Peter Henlein
• Freely swinging horizontal bar (foliot) attached to centrally-located vertical shaft (verge)
• Weight driven

​Würtz Escapement

Created by Philippe Würtz, 2001