Dry vacuum pump with improved gas discharging speed and pump cooling

A dry vacuum pump comprising:

• a first cylinder, a second cylinder and a third cylinder;
• a front cover and a rear cover in a tier-structure, wherein said first cylinder, said second cylinder and said third cylinder are installed between said front cover and said rear cover in a tiered-structure;
• an intermediate cover being formed between the first and the second cylinders;
• a pair of main screws being installed in the first cylinder for compressing and discharging a gas of a vacuum facility;
• a rotor being formed in the second cylinder for drawing, compressing, and discharging the gas compressed by the main screws;
• at least one circular shaped gas flow path, said at least one gas flow path being formed between the intermediate cover and the second cylinder for compressing and discharging the gas;
• a motor housing engaging the front cover;
• a cooling water inlet being formed within an outer surface of the rear cover of the dry vacuum pump;
• a cooling water outlet being formed within the front cover;
• a plurality of circular shaped cooling water flow paths being formed for guiding a cooling water pumped through the cooling water inlet to circulate in said cylinders and the intermediate cover, wherein at least one cooling water flow path is formed in an inner and an outer side of the circular shaped gas flow path formed in the rear cover and the intermediate cover;
• a flow pipe, wherein the cooling water flow paths which are formed in the inner and outer sides of the gas flow path are connected by the flow pipe which passes through the gas flow path for thereby concurrently cooling the gas flow path;
• and
• a rotary shaft, wherein portions of the rotary shaft are capable of being cooled by the cooling water flow paths.