This application relates to a synchronous engagement clutch, such as a clutch for use in a turbine starter for a gas turbine engine.
Turbine starters are used to drive engines, such as gas turbine engines, up to speed before ignition. A typical turbine starter may be driven by a power source, such as an auxiliary power unit (APU) or a ground air supply unit that supplies pressurized air to generate torque. A clutch is used to transfer torque from the power source to a shaft in the engine during startup and to disengage the power source from the engine after the engine starts running.
One variety of clutches uses spherical flyweights to engage and disengage depending on the state of the power source and engine operating speed. The power source drives a fixed member and a translating member, both having sloped pockets for the flyweights. The pockets are typically shallow relative to a diameter of the flyweights.
When the power source is running, the air turbine starter engagement and flyweights, or engagement balls, are centrifugally driven to outer ends of their respective pockets. The outward travel of the flyweights against the slope of the engagement ball pockets pushes the translating member into engagement with an assembly that transmits torque to the engine. The power source is cut off after the engine begins to run, and an opposing set of flyweights (disengagement balls) on the gearbox engine shaft side of the clutch pushes the translating member back out of position.