Simple integral high vacuum valve

A simple mechanical system is described which enables a vessel to be roughly evacuated by a rotary pump, then by turning a handle through a third of a revolution, the vessel can be evacuated by combined rotary and diffusion pumps. A further turn will allow air into the vessel, and completing one revolution brings the system back to the initial state of being roughed. This is effected by coupling a baffle valve and specially designed rotating plate valve.