Pistonless positive displacement unit - uses bellows welded of rings stiff in bending but flexible, also central valve and plug block

摘要

The pistonless positive displacement unit, esp. for heat engines, has a welded bellows assembly (1) made up of thin, wide, annular discs of material which is flexible but stiff in bending, pref. sheet metal. Valves, plus spark plug if required, are in a concentric block, central to the bellows. The valves are spring-loaded; the inlet valve is opened by pressure difference across it, the outlet by a cam (21) moving the whole block via a blade spring (22) mounted follower (19). The inlet duct (15) is flexible. The bellows natural frequency is selected to have a specific relationship with that of the system. Bellows discs may have a coating, permeable or impermeable, or permeable inserts, or reed valves.