Double wrap dry scroll vacuum pump having a compressed gas cooling passage disposed in the scroll shaft

A double-wrap dry scroll vacuum pump having a pump body comprising:

• a revolving scroll including a base and a pair of revolving scroll wraps arranged on both sides of the base, a pair of stationary scrolls each having a scroll wrap engaged with each revolving scroll wrap and holding the revolving scroll on both sides, and a drive shaft penetrating a central part of each of the stationary scrolls, a central part of the revolving scroll being driven by the drive shaft;
• the pump body further comprising:
• a pair of enclosing members each mounted to an external surface of one of the stationary scrolls via a sealing member and each of the enclosing members covering an end portion of the drive shaft, the drive shaft being in fluid communication with compressed gas feed ports at each end portion;
• a compressed gas axial cooling passage formed in the drive shaft and a compressed gas being introduced to each end portion of the drive shaft and into the axial cooling passage from each of the compressed gas feed ports, and the drive shaft further including at least one additional passage in fluid communication with the axial cooling passage for introducing the compressed gas to a bearing which supports the drive shaft;
• a gas bearing for rotatively supporting the drive shaft and being in fluid communication with the axial cooling passage through at least one discharge passage formed in an eccentric portion of the drive shaft which supports the revolving scroll, the at least one discharge passage communicating compressed gas to a space between an inner and outer ring of the gas bearing;
• a port formed by an end surface of the gas bearing, the revolving scroll and one of the stationary scrolls, and receiving the compressed gas from the space between the inner and outer ring of the gas bearing and directing the compressed gas to a discharge passage;
• and
• the discharge passage formed in one of the stationary scrolls for discharging the compressed gas from the port to an outside of the pump body, together with a wrap compressed gas generated by a contraction operation of a gas-tight space formed by the revolving and the stationary scrolls.