Editing Pallet fork

[[Image:pallet-lever.jpg|thumb|Pallet fork with jewel pallets (pink)]]
[[Image:Chinese movement escapement and jewels.jpg|thumb|The pallet fork is above the [[balance wheel]] in this watch movement]]

The '''pallet fork''' is a component of the [[lever escapement]] of a [[mechanical watch]].<ref name="Odets">{{cite web
  | last = Odets
  | first = Walt
  | author-link = 
  | title = The Anchor Escapement
  | work = The Horologium
  | publisher = TimeZone.com
  | date = 
  | url = http://www.timezone.com/library/horologium/horologium631673198118416858
  | format = 
  | doi = 
  | accessdate = 2008-07-02
  | archive-url = https://web.archive.org/web/20080622201835/http://www.timezone.com/library/horologium/horologium631673198118416858
  | archive-date = 2008-06-22
  | url-status = dead
  }}</ref> The pallet fork and the lever form one component that sits between the escape wheel and the [[balance wheel]]. Its purpose is to lock the escape wheel, and release it one tooth at a time at each swing of the balance wheel, and also give the balance wheel small pushes to keep it going.<ref name="Kelly">{{cite book
 | last1  = Kelly
 | first1 = Harold C. 
 | title  = A Practical Course in Horology
 | publisher = Read Books
 | date   = 2017
 | pages  = 7
 | url    = https://books.google.com/books?id=XqcyDwAAQBAJ&q=%22pallet+fork%22balance+wheel%22+%22lever+escapement%22+terminology
 | doi    = 
 | id     = 
 | isbn   = 9781473339507
 }}</ref><ref name="Odets" /><ref name="Silva">{{cite book
 | last1  = de Silva
 | first1 = Clarence W. 
 | title  = Mechatronic Systems: Devices, Design, Control, Operation and Monitoring
 | publisher = CRC Press
 | date   = 2007
 | pages  = 3.3
 | url    = https://books.google.com/books?id=MNvKBQAAQBAJ&q=%22pallet+fork%22balance+wheel%22+%22lever+escapement%22
 | doi    = 
 | id     = 
 | isbn   = 9780849307768
 }}</ref>

In early watches the pallet fork and the lever were made as separate components and joined together. In later watches they were made as a single component as shown in the picture. The combined component is often referred to simply as the "lever". In a straight line Swiss lever type escapement, the lever is shaped like a 'T' or an anchor, which gives this escapement its alternative name of anchor escapement. The lever is pivoted in the center; in operation it rocks back and forth.<ref>{{cite web
  | last = Odets
  | first = Walt
  | author-link = 
  | title = The Escapement
  | work = Illustrated Glossary of Watch Parts
  | publisher = TimeZone.com
  | date = 
  | url = http://www.timezone.com/library/wglossary/wglossary631692132071014935
  | format = 
  | doi = 
  | accessdate = 2008-07-02
  | archive-url = https://web.archive.org/web/20080630082138/http://www.timezone.com/library/wglossary/wglossary631692132071014935
  | archive-date = 2008-06-30
  | url-status = dead
  }}</ref>  On the arms of the 'T' are angled surfaces called ''pallets'' which alternately engage the teeth of the escapement's ''escape wheel''.   The central shaft of the lever ends in a fork, which gives pushes to the [[balance wheel]]'s ''impulse pin'', which is set off center in a disk on the balance wheel's shaft.  To reduce friction, the pallets are made of precisely shaped pieces of ruby [[Mechanical watch#Watch jewels|jewel]].  The pallet which the teeth first contact is called the ''entry pallet'', while the other one is called the ''exit pallet''.

Under the fork there is a projecting ''guard pin'' which passes through a notch in a separate ''safety roller'' disk on the balance shaft.  In normal operation it doesn't have a function.  Its purpose is to make sure the fork is in the right position to receive the impulse pin if a jar to the watch prematurely 'unlocks' the lever from the escape wheel.

Mechanical [[alarm clock]]s and kitchen [[timer]]s use a less accurate form of the lever in which vertical metal pins are substituted for the pallet jewels.  This is called a [[Georges Frederic Roskopf|Roskopf]] or [[pin-pallet escapement]], and was previously used in cheap [[pin-pallet escapement|pin-lever]] watches.

==Notes and references==
<references/>

[[Category:Timekeeping components]]