The figure exhibits the vacuum clutch mechanism. This sort of clutch uses the existing vacuum inside the engine manifold to function the clutch. The vacuum clutch contains a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  An air-con compressor in a car or truck has an electromagnetic clutch. https://clutch-kereta09741.blog2freedom.com/33026069/5-simple-techniques-for-clutch-plate