Multi-section roots vacuum pump of reverse flow cooling type with internal flow division arrangement

A multi-section Roots vacuum pump of the reverse flow cooling type with internal flow division arrangement, comprising:

• a sequence of pump sections;
• two shafts common to said sequence of pump sections for transmitting driving power;
• said pump sections each having a rotor pair coupled to said shafts;
• castings for said pump sections including housings for accommodating said rotor pairs therein;
• inlet passages and outlet passages of said casings for supplying gas into said casings and discharging gas from said castings;
• upper peripheral gas passages formed around upper portions of said housings and connected to said inlet passages for sending gas to the adjacent pump sections;
• lower peripheral gas passages formed around lower portions of said housing and connected to supply inlets of reverse flow cooling gas for supplying reverse flow cooling gas into said housings;
• partition walls between said upper and lower peripheral gas passages;
• and
• inter-section walls for separating adjacent pump sections;
• communicating passages being formed through said inter-section walls for communicating said lower peripheral gas passages of pump sections with said upper peripheral gas passages of the following pump sections;
• connection pipes being provided between outlet passages of said casing of pump sections and inlet passages of said casing of the following pump sections;
• and
• coolers being provided in said connection pipes.