Heavy Duty Scotch Yoke Pneumatic Valve Actuator

Scotch yoke refers to a sliding linear mechanism that provides a reciprocating motion. One of the most common uses for scotch yokes are pneumatic valve actuators.
scotch yoke mechanism
Scotch yoke mechanism
(courtesy of Wikipedia)
Scotch yoke valve actuators are designed to provide higher torque output for larger industrial valves. They typically have large pistons and air cylinders that provide the linear force required to open and close large quarter turn valves (ball, butterfly, plug).

Scotch yoke pneumatic actuator
Scotch yoke pneumatic actuators installed
in sea terminal
(courtesy of Rotork)
Scotch yoke actuators can be energized by either compressed gases, or hydraulic fluids. Here are some images of scotch yoke actuators in use:

Scotch yoke pneumatic actuator
Large spring return scotch yoke actuator
(courtesy of Rotork)