A method of treating, tuning, assembling, and/or overhauling a twin rotor device (200, 1200) includes applying a coating material (102) on an internal set of working surfaces (218, 222, 224, 226, 228, 1218, 1222, 1224, 1226, 1228) of the twin rotor device when at least partially assembled. The coating may be factory or field applied to a new or used twin rotor device. The working surfaces may be uncoated or previously coated and may be built-up as the coating material forms a coating (206, 1206) on at least some of the working surfaces. Manufacturing variations of a pair of rotors (220, 1220) and a housing (210, 1210) may be compensated by the coating. One or more performance characteristics of the twin rotor device may be improved by the coating, and variation between a series of twin rotor device may be reduced or substantially eliminated. The coating may reduce internal leakage and increase volumetric efficiency of the twin rotor device. The twin rotor device may be a supercharger 200, a screw compressor 1200, or other twin rotor device.

The present invention provides a method of ceasing rotation of a rotor of a vacuum pump. The method comprises the steps of rotating the rotor at an intermediate RPM, at which there is substantially no probability of the rotor clashing with the stator, for a dwell time sufficient for the vacuum pump to be at or below a threshold temperature, and subsequently coasting down the rotation of the rotor until cessation of rotation.

A rotor for a positive displacement compressor assembly having a housing defining an inlet, an outlet, and a rotor cavity in communication with the inlet and the outlet. The rotor may comprise a rotor body and a porous inner core enclosed within the rotor body. The rotor may comprise a tapered rotor body having an outer radius that decreases from a first end to a second end thereof. In one form, the positive displacement compressor assembly may comprise a supercharger assembly for an internal combustion engine.

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.

A dry pump for gases comprises a first rotor (1) comprising a first lobe portion (1A) and a first screw (1B), as well as a second rotor (2) comprising a second lobe portion (2A) and a second screw (2B). A casing delimits an internal volume in which are located together the first and second screws (1B, 2B) and the first and second lobe portions (1A, 2A). Each of the first and second screws (1B, 2B) comprises a threading invariable along its length. The first and second rotors (1, 2) turn in opposite directions and are located in successive configurations. In a first configuration of the rotors, the first and second lobe portions (1A, 2A), a portion of the first screw (1B), a portion of the second screw (2B) and the casing together delimit a chamber (30) which is closed. In a second configuration of the rotors, the chamber (30) has a smaller capacity than in the first configuration. In a third configuration of the rotors, the chamber (30) is displaced entirely at the first and second screws (1B, 2B) and isolated from the lobe portions.

A pair of intermeshing gears for multi-shaft vacuum pumps, comprising a first running gear and a second running gear is provided, wherein at least the first running gear comprises a first and a second gearwheel, respectively. The first and the second gearwheel are axially arranged in direct contact, wherein the first gearwheel comprises a predetermined number of first cogs of same dimension and the second gearwheel comprises a predetermined number of second cogs, wherein the predetermined number of second cogs is at least one. All of the predetermined number of first cogs have a dimension larger than the dimension of the predetermined number of second cogs to a predetermined amount. The first gearwheel is made of a material with a first elastic modulus. The second gearwheel is made of a material with a second elastic modulus, wherein the first and the second elastic modulus are different.

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.

A multistage Roots pump comprise a plurality of pump chambers in a pump housing. They constitute respective pump stages, wherein each pump stage comprises two two-toothed rotary pistons. The pump stages are separated from each other by partition walls. In the partition walls essentially radially extending connecting ducts are arranged. The connecting ducts are connected with an inflow chamber whose inflow opening has a larger cross-section than the connecting ducts.

A pump includes a first housing part defining a first portion of a bore extending within the first housing part and shaped to receive a rotor; and a second housing part defining a second portion of the bore extending within the second housing part and shaped to receive the rotor. The first housing part has a first face abutable against an opposing second face of the second housing part to position the first portion of the bore with the second portion of the bore to receive the rotor. The first portion of the bore has a first circular cross-section portion centered along the first face and the second portion of the bore having a second circular cross-section portion centered, within the second housing part, at a distance from the second face.

A rotor for a multi-stage vacuum pump, a multi-stage vacuum pump and a method. The rotor comprises: a plurality of rotary vanes, the plurality of rotary vanes being axially displaced and coaxially aligned; a pair of end shafts, each end shaft extending from opposing axial ends of the plurality of rotary vanes; and an inter-vane shaft extending between adjacent rotary vanes of the plurality of rotary vanes, the inter-vane shaft having a diameter which is greater than that of the end shafts. In this way, the inter-vane shaft provided between each rotary vane may have an increased diameter, which improves the stiffness of the shaft and changes the modal frequency of the rotor. Such a change in the modal frequency is typically sufficient to improve its operation.