The invention relates to a screw compressor comprising a compressor housing (11) having two rotor screws (1, 2) mounted axially parallel therein, which mesh with each other in a compression space (18), can be driven by a drive and are synchronized with each other in their rotational movement, wherein the rotor screws (1, 2) each have a single-part or multi-part base body (24) with two end faces (5a, 5b, 5c, 5d) and a profiled surface (12a, 12b) extending therebetween, and shaft ends (30) projecting beyond the end faces (5a, 5b, 5c, 5d), wherein at least the profiled surface (12a, 12b) is formed in multiple layers, comprising a first, inner layer (3) and a second, outer layer (4), wherein the first, inner layer (3) and the second, outer layer (4) both comprise or are formed from a thermoplastic synthetic material, wherein particles (25) or pores (32) supporting a running-in process are embedded in the second, outer layer (4) and the thermoplastic synthetic material defines a matrix for receiving the particles (25) or for forming the pores (32).

A blower assembly includes, but is not limited to, a blower housing defining a blower chamber and including a gas inlet and a gas outlet; a first rotor positioned within the blower chamber and adapted for rotation therein, the first rotor including a first shaft and at least two lobes defining a first lobe profile; and a second rotor positioned within the blower chamber and adapted for rotation therein, the second rotor including a second shaft and at least two lobes defining a second lobe profile, wherein the first and second rotors are formed from a metal having a coefficient of thermal expansion from about 1 (10.sup.-6 in/in * K) to about 13 (10.sup.-6 in/in * K), and wherein at least one of the outer surface of the first rotor, the outer surface of the second rotor, or the blower chamber includes a coating.

A geared compressor includes a drive gear, a first intermediate gear, a second intermediate gear, a first impeller and a second impeller connected to a first driven gear, and a third impeller and a fourth impeller connected to a second driven gear. When viewed from an axial direction, a drive axis of the drive gear is disposed below a first intermediate axis of the first intermediate gear, a second intermediate axis of the second intermediate gear, a first driven axis of the first driven gear, and a second driven axis of the second driven gear in a vertical direction. The first impeller has a larger outer diameter than the second impeller, the third impeller, and the fourth impeller.

A rotor polishing device, including a housing with a space therein for holding rotors in need of polishing, an inlet for pumping a polishing lapper into the housing, and a rotational assembly for rotating the rotors during the polishing process. The rotor polishing device is useful for polishing rotors commonly used by rotary screw compression systems.

A transmission between a drive shaft and a driven shaft comprises a housing and at least a driven gearwheel that is mounted on the driven shaft and a drive gearwheel that is mounted on a drive shaft. The housing comprises two separated chambers, i.e. a first chamber that is connected to the driven shaft and a second chamber which is separate from the first chamber, whereby the first chamber is connected via a channel with the second chamber, whereby around the drive gearwheel or driven gearwheel the second chamber is formed, whereby the form of the second chamber is such that when the gearwheel in question rotates, a gas flow is created around this gearwheel which causes a negative pressure in the channel by the venturi effect.

A transmission between a drive shaft and a driven shaft comprises a housing and at least a driven gearwheel that is mounted on the driven shaft and a drive gearwheel that is mounted on a drive shaft. The housing comprises two separated chambers, i.e. a first chamber that is connected to the driven shaft and a second chamber which is separate from the first chamber, whereby the first chamber is connected via a channel with the second chamber, whereby around the drive gearwheel or driven gearwheel the second chamber is formed, whereby the form of the second chamber is such that when the gearwheel in question rotates, a gas flow is created around this gearwheel which causes a negative pressure in the channel by the venturi effect.

A driving structure of a three-axis multi-stage Roots pump comprises a pump body, wherein a gear end cover is mounted at one side of the pump body, an air outlet end moving bearing air sealing unit is mounted on the other side of the pump body, and the bearing end cover is mounted on the pump at the side of the pump body; a driving axis, a first driven axis and a second driven axis are further provided inside the pump body, and the driving axis is connected with the first driven axis and the second driven axis through the gear, respectively; and both ends of the driving axis, the first driven axis and the second driven axis are movably connected to an air inlet end gear mechanical seal driving unit and an air outlet end moving bearing air sealing unit, respectively. The present invention overcomes the deficiencies of the prior art, a fixed bearing limiting unit not only plays a radial supporting role, strengthens the rigidity of an independent axis, but also reduces the diameter of the axis, and at the same time, evenly distributes to the two axial ends in the axial deformation process, avoiding deformation in a single direction, reducing the amount of displacement by nearly half, and also improving the sealing efficiency of the system.

A motor-driven Roots pump includes a housing, a drive shaft and a driven shaft that have axial lines parallel with each other, and a gear chamber. The housing includes a first partition that has a first defining surface, a second partition having a second defining surface, and a relief recess. An addendum circle of the drive gear and an addendum circle of the driven gear intersect with each other at a first intersection point. A plane that includes both the axial lines is defined as an imaginary plane. The first intersection point is located on a side of the imaginary plane on which the drive gear and the driven gear start meshing with each other. An opening of the relief recess is opposed to the first intersection point and is arranged in a region on a side of the imaginary plane on which the first intersection point is located.

A screw vacuum pump comprises a housing forming a pumping chamber, wherein the housing is made of aluminum or an aluminum alloy. Further provided are two screw rotors arranged in the pumping chamber, each screw rotor comprising at least one displacer element having a helical recess for forming a plurality of windings, wherein the at least one displacer element is made of aluminum or an aluminum alloy. Between the region in which prevail 5% to 30% of the outlet pressure and a pressure-side end of the rotor (pump outlet), at least six, particularly at least eight, and with particular preference at least ten windings are provided.

A blower may include a blower housing that may include a plurality of rotor chambers and a plurality of rotors. The plurality of rotors may be substantially identical and each may include a twist angle and a helix angle. The rotors and the blower housing may be configured to create internal fluid compression when the rotors are rotating at a first rotational speed and not to create internal fluid compression when the rotors are rotating at a second rotational speed. The rotors and the blower housing may be configured to create the internal fluid compression without backflow slots in the blower housing. The twist angle may include the angular displacement of lobes of the plurality of rotors between axial ends of the plurality of rotors. The helix angle may be a function of the twist angle and a pitch diameter of the plurality of rotors.