Scotch yoke
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The Scotch yoke, also spelled Scotch Yoke and scotch yoke, is a mechanism for converting the linear motion of a slider into rotational motion or vice-versa. The piston or other reciprocating part is directly coupled to a sliding yoke with a slot that engages a pin on the rotating part.
The advantages compared to a standard crankshaft and connecting rod setup are:
- High torque output with a small cylinder size.
- Fewer moving parts.
- Smoother operation.
- Higher percentage of the time spent at top dead center (dwell) improving engine efficiency.
- Higher percentage of the time spent at bottom dead center to scavenge exhaust gases in 2-stroke engine design.
- In an engine application, elimination of joint typically served by a wrist pin, and near elimination of piston skirt and cylinder scuffing, as side loading of piston due to sine of connecting rod angle is eliminated.
The disadvantages are:
- Rapid wear of the slot in the yoke.
The shape of the motion of the piston is a pure sine wave over time given a constant rotational speed.
[edit] Applications
This setup is most commonly used in control valve actuators in high pressure oil and gas pipelines.
Scotch yoke engine (Bourke engine).
[edit] External links
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