An oil-free screw compressor has a screw rotor including a screw and a shaft, a bearing supporting the shaft, a first shaft seal device disposed between the screw and the bearing and including a first seal opposite to the shaft, and a first communication portion communicating the bearing side with respect to between the shaft and the first seal and the outer peripheral face of the first shaft seal device, and a second shaft seal device disposed between the first shaft seal device and the bearing and including a second seal opposite to the shaft, and a second communication portion communicating the screw side with respect to between the shaft and the second seal and the outer peripheral face of the second shaft seal device. A casing includes an atmosphere communication portion connected to both of the first communication portion and the second communication portion on the inner peripheral face of a shaft accommodation space, and communicating the first communication portion and the second communication portion with the atmosphere.

The oil-free screw compressor includes: a casing having a rotor chamber; a bearing supporting rotary shafts of screw rotors; a shaft seal device with an oil seal portion and an air seal portion; a ventilation gap positioned between the oil seal portion and the air seal portion; and an atmosphere open passage communicating an atmosphere side of the casing with the ventilation gap communicate. A most narrowed portion, an air seal portion, and oil seal portions are set such that the followings is established:

(La/Sa.sup.2.5)/(Lh/Sh.sup.2.5)>|P2|/ΔPb La: effective shaft seal length Sh: effective open cross-sectional area (most narrowed portion of atmosphere open passage) Lh: effective narrowed length (most narrowed portion of atmosphere open passage) Sa: shaft seal cross-sectional area |P2|: negative pressure in rotor chamber during unloading operation ΔPb: minimum differential pressure in the oil seal portion during the unloading operation

A screw compressor includes a screw rotor, a casing, and a delivery side shaft sealing unit. The delivery side shaft sealing unit includes an annular groove, a seal ring, and a shaft sealing fluid supply passage. Pressure of the fluid that is supplied to the one side, in the axial direction, of the seal ring via the shaft sealing fluid supply passage is set higher than pressure that acts on a first side surface, in an axial direction with respect to a first side wall surface of the annular groove, of the seal ring.

A compression system is disclosed having a compressor and a seal package including a non-contact seal and one or more radial shaft seals. In one form the non-contact seal is placed in proximity to a high pressure portion of the compressor. The offset of the non-contact seal from a shaft used to drive the compressor allows some amount of pressure reduced leakage air to pass. A radial shaft seal is coupled to the shaft axial aft of the non-contact seal on the other side of the compressor and oriented to discourage further passage of the leakage air past the radial shaft seal. A vent conveys leakage air to return to the compressor. A backup radial shaft seal can be used axially aft of the first radial shaft seal. A further radial shaft seal is disposed adjacent to the backup seal and oriented in the other direction to seal lubricant for a bearing.

This scroll compressor is provided with a scroll member which has a compression chamber which compresses a work fluid, a housing which houses the scroll member, a second drive-side shaft (72c) which discharges compressed work fluid from the compression chamber and which rotates about an axis with respect to the housing, and a seal member (16) which contacts and forms a seal with the outer peripheral surface X of the second drive-side shaft (72c). On the outer peripheral surface (X) that contacts the seal member (16), the second drive-side shaft (72c) is provided with a surface hardened part (Y).

A pump is described, including: a drive shaft including a rotor; a first housing part and a second housing part, between which a pump chamber is formed, in which the rotor is arranged; a rotary bearing via which the drive shaft is mounted on the first housing part such that it can rotate about its rotational axis; and a passage including a first opening and a second opening, wherein the rotary bearing is arranged between the pump chamber and the first opening, and the second opening of the passage emerges onto the side of the second housing part which faces away from the pump chamber.

A high suction pressure thrust load balance assembly configured for use with a single screw compressor includes comprises a sealing baffle that is keyed to, so as to be rotatable along with, a main rotor drive shaft of the single screw compressor. The sealing baffle is configured to create a force or load to counteract the axial force of the main rotor drive shaft created during rotation of the main rotor drive shaft using the pressurized oil used to lubricate the mechanical shaft seal of the compressor.

Positive displacement machine such as a compressor, expander, pump or the like, for displacing a gaseous or liquid medium, the machine containing an element with at least one inlet and at least one outlet for the medium and at least two cooperating driven moving parts. The mutual periodic movement of the moving parts displaces the medium from the inlet to the outlet. Each of the at least two driven cooperating moving parts is provided with its own individual drive. The element is provided with a kinematic synchronisation coupling between the at least two cooperating moving parts for the mutual kinematic synchronisation of their movements.

An electric pump includes a housing that includes a gear chamber, a rotor chamber, and a motor chamber. The electric pump includes a first seal member, a second seal member, and a third seal member. The first seal member seals a space between the gear chamber and the rotor chamber. The second seal member seals the space between the gear chamber and the rotor chamber. The third seal member seals a space between the gear chamber and the motor chamber. The third seal member seals the space between the gear chamber and the motor chamber to a lesser extent than the first seal member and the second seal member seal the space between the gear chamber and the rotor chamber.

Scroll devices with cooling fluid supplied through a crankshaft are provided. The device may comprise an orbiting scroll operably connected to a fixed scroll and a crankshaft operably connected to the orbiting scroll. A first seal may be positioned about an outer surface of the crankshaft to form a seal with the outer surface. A second seal may be positioned about an outer surface of the crankshaft to form a seal with the outer surface. A first channel and a second channel extend through the crankshaft and are in fluid communication with the orbiting scroll and a fluid source and a fluid reservoir.