The figure shows the vacuum clutch system. This sort of clutch utilizes the prevailing vacuum in the motor manifold to work the clutch. The vacuum clutch includes a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  This helps prevent the transmission shaft and clutch plate from tilting up https://beckettvvsqo.activosblog.com/32084392/how-clutch-kereta-can-save-you-time-stress-and-money