Provided is a multi-stage screw compressor with which an intermediate shaft section of a rotor can be made shorter. A two-stage screw compressor includes a front-stage compressing mechanism 1 which has a front-stage male rotor 11A and a front-stage female rotor 11B, and which compresses air, and a rear-stage compressing mechanism 2 which has a rear-stage male rotor 12A and a rear-stage female rotor 12B, and which further compresses the air compressed by the front-stage compressing mechanism 1. The front-stage male rotor 11A and the rear-stage male rotor 12A are configured to be coaxial, and the front-stage female rotor 11B and the rear-stage female rotor 12B are configured to be coaxial. An axial delivery pocket 34 of the front-stage compressing mechanism 1 and an axial intake pocket 39 of the rear-stage compressing mechanism 2 are arranged in a positional relation of partly overlapping with each other in the axial direction of the rotor, and are separated from each other by a separating wall 41.

A compressor may include first and second scroll members, first and second bearings, and first and second Oldham couplings. The scroll members define compression pockets. The first bearing may define a first rotational axis about which the first scroll member rotates. The second bearing may support the second scroll member for rotation about a second rotational axis that is offset from the first rotational axis. The first Oldham coupling may include a first body and a plurality of first keys extending from the first body. The first keys may engage slots formed in the second scroll member. The second Oldham coupling is separate and distinct from the first Oldham coupling. The second Oldham coupling may include a second body and a plurality of second keys extending from the second body. The second keys may engage slots formed in a surface that rotates about the first rotational axis.

A complete bearing-sealed root vacuum pump system capable of promoting vacuum ability of a condenser of a power plant provides a complete bearing-sealed structure. All chambers are isolated effectively so that liquid cannot flow there between and thus not to destroy the root vacuum pump. Therefore, the lifetime of the root vacuum pump is prolonged. The heat exchangers are arranged between the root vacuum pumps and the front stage pump so as to return the condensed water. The condenser vacuum is improved and thus the power generation efficiency is promoted, and power consumption is lowered. As a result a large power plant can save several thousand tons of coals per year.

A compressor system can include a lubricant injection system useful to supply lubricant to an airend. The compressor system can include a variable lubricant flow valve which can be regulated by a controller on the basis of operating conditions of the compressor system. In one form the compressor system also includes an oil separator and/or an oil cooler with or without a them al control valve. The controller can have one or more modes of operation, including a mode in which the controller regulates the flow of lubricant to the airend to increase an internal flow area of the valve when the airend is operated at an unloaded or loaded condition. In some forms the controller can regulate the lubricant flow valve and/or the thermal control valve and/or the lubricant cooler.

A compressor system can include a lubricant injection system useful to supply lubricant to an airend. The compressor system can include a variable lubricant flow valve which can be regulated by a controller on the basis of operating conditions of the compressor system. In one form the compressor system also includes an oil separator and/or an oil cooler with or without a them al control valve. The controller can have one or more modes of operation, including a mode in which the controller regulates the flow of lubricant to the airend to increase an internal flow area of the valve when the airend is operated at an unloaded or loaded condition. In some forms the controller can regulate the lubricant flow valve and/or the thermal control valve and/or the lubricant cooler.

A screw compressor element may have a housing; a cylinder bearing including an inner ring, an outer ring, a raceway, and a cylindrical rolling element that contacts the inner ring and the outer ring at a location of the raceway thereof; and a ball bearing including an inner ring, an outer ring, a raceway, and a ball shaped rolling element that contacts the inner ring and the outer ring at a location of the raceway thereof, wherein a rotor is rotatably arranged by way of the cylinder bearing and the ball bearing.

A compressor system can include a lubricant injection system useful to supply lubricant to an airend. The compressor system can include a variable lubricant flow valve which can be regulated by a controller on the basis of operating conditions of the compressor system. In one form the compressor system also includes an oil separator and/or an oil cooler with or without a thermal control valve. The controller can have one or more modes of operation, including a mode in which the controller regulates the flow of lubricant to the airend to increase an internal flow area of the valve when the airend is operated at an unloaded or loaded condition. In some forms the controller can regulate the lubricant flow valve and/or the thermal control valve and/or the lubricant cooler.

The pump device includes a motor portion that includes a shaft rotating about a central axis and a pump portion that is driven by a motor portion via the shaft. The pump portion includes a pump rotor that rotates along with the shaft and a pump housing that includes an accommodation portion that accommodates the pump rotor. The pump housing includes a pump body that includes a first bearing portion that supports the shaft and a pump cover with an accommodation portion disposed between the pump cover and the pump body. The pump cover includes a flow path through which oil is discharged and suctioned, and includes a second bearing portion that rotatably supports the shaft and that communicates with the flow path. An end portion of the shaft on one side in the axial direction is disposed at the second bearing portion or inside the flow path.

Provided is a multi-stage screw compressor with which an intermediate shaft section of a rotor can be made shorter.

A two-stage screw compressor includes a front-stage compressing mechanism 1 which has a front-stage male rotor 11A and a front-stage female rotor 11B, and which compresses air, and a rear-stage compressing mechanism 2 which has a rear-stage male rotor 12A and a rear-stage female rotor 12B, and which further compresses the air compressed by the front-stage compressing mechanism 1. The front-stage male rotor 11A and the rear-stage male rotor 12A are configured to be coaxial, and the front-stage female rotor 11B and the rear-stage female rotor 12B are configured to be coaxial. An axial delivery pocket 34 of the front-stage compressing mechanism 1 and an axial intake pocket 39 of the rear-stage compressing mechanism 2 are arranged in a positional relation of partly overlapping with each other in the axial direction of the rotor, and are separated from each other by a separating wall 41.

A scroll compressor includes a flow path that is disposed in a portion of a bearing holder, which corresponds to each formation position of a plurality of stator groove portions, and that penetrates the bearing holder in an axial direction, a first recess portion (72) disposed in a portion of a thrust bearing, which faces the flow path, and recessed from one side in the axial direction to the other side in the axial direction, and a first groove portion (74) disposed in an outer peripheral portion of the first recess portion (72), extending from a bottom surface (72a) of the recess portion (72) to a surface located on a side opposite to a surface having the first recess portion (72) formed thereon, and communicating with the first recess portion (72) in the axial direction.