Abstract: A supercharged internal combustion engine is drivably connected to a variable displacement supercharger operable to continuously supply varying amounts of an air mass to the engine in response to the varying power requirements of the engine. The variable displacement capability eliminates blowdown losses of fixed displacement superchargers and substantially reduces the need for throttling of the intake air. The device also presents an air-motoring mode that can recover a portion of the engine throttling losses as positive power returned to the engine crankshaft when the engine intake manifold is below atmospheric pressure.

Abstract: A pump having at least two fluid drivers and a method of delivering fluid from an inlet of the pump to an outlet of the pump using the at least two fluid drivers. Each of the fluid drives includes a prime mover and a fluid displacement member. The prime mover drives the fluid displacement member to transfer fluid. The fluid drivers are independently operated. However, the fluid drivers are operated such that contact between the fluid drivers is synchronized. That is, operation of the fluid drivers is synchronized such that the fluid displacement member in each fluid driver makes contact with another fluid displacement member. The contact can include at least one contact point, contact line, or contact area.

Abstract: An electric pump includes a motor unit rotationally driving a drive shaft, and a pump unit. The pump unit includes a pump rotor that sends the fluid by a driving force of the driving shaft, and a pump housing that covers at least one side of the pump rotor. The pump housing includes an attachment surface extending in the axial direction and in contact with an attached body, first and second flow paths respectively on the suction side and the discharge side, and a partition wall positioned between pump-side openings of the first flow path and the second flow path facing the pump rotor, and extends in a direction along the attachment surface, and locations of attachment-side openings of the first flow path and the second flow path on the attachment surface are displaced from each other on the attachment surface in the axial direction.

Abstract: An oscillation module for a compacting roller of a soil compactor includes a plate-like carrier, at least two oscillation mass units supported on the carrier at a distance from one another, and an oscillation drive motor supported on the carrier. The carrier has a connection formation for firmly connecting the carrier to a carrier structure of a compacting roller. Each oscillation mass unit includes an imbalance mass rotatably supported on the carrier about an oscillation axis of rotation. Each imbalance mass of each oscillation mass unit can be driven by the oscillation drive motor for rotation about the respectively assigned oscillation axis of rotation.

Abstract: A pump assembly may include a rotor having a rotor shaft portion; a stator having a bore portion defining a bore for receiving the rotor shaft portion; and a circumferential protrusion extending radially into the bore between the bore portion and the rotor shaft portion, wherein at least one of the protrusion and a corresponding surface of the rotor shaft portion or the bore portion is configured to be abraded by the other upon experiencing contact therewith. In this way, the gap between the bore portion and the rotor shaft portion may be at least partially filled by the circumferential protrusion in order to provide a seal. The protrusion and one of the bore portion and the rotor shaft portion may be formed from different hardness materials.

Abstract: A microfluidic pumping system configured to prevent backflow from an outlet of the system toward an inlet of the system. The microfluidic pumping system comprising a gear housing that has an inlet and an outlet and that houses a drive gear, an idler gear and a drive shaft. The system further includes a front end plate that is coupled to a first surface of the gear housing and a rear end plate that is coupled to a second, different surface of the gear housing. Also coupled to the gear housing is a first and second Halbach magnet arrays that is disposed between the front end plate and the rear end plate. The first and second Halbach magnet arrays include one or more solenoids and the first Halbach magnet array is disposed proximate to the drive gear and the second Halbach magnet array is disposed proximate to the idler gear.

Abstract: A rotary positive displacement pump comprising a pair of forwardly-positioned sealing arrangements and a pair of forwardly-positioned sleeves are received within a cavity providing for easy maintenance of the pump when the seals need to serviced. Each of the sealing arrangement includes a dynamic seal and a static seal. The dynamic seal abuts a corresponding sleeve and hub while a static seal is established between the corresponding sleeve and rotor.

Abstract: A modular system for producing a screw spindle pump having a housing with a drive spindle therein and at least one running spindle meshing with the drive spindle, including: a plurality of housing components including a basic housing component exhibiting a fluid inlet for the formation of a basic pump chamber, a housing pressure component exhibiting a fluid outlet, bearing the drive spindle for creating a pressure chamber, a housing cover arranged on the basic housing part for supporting running spindle, and identical intermediate housing components arrangeable in any number between the basic housing component and the housing pressure component and form an additional pump chamber in each case; and a plurality of running spindle elements including at least one running spindle base element arranged in the basic housing component, and identical running spindle extension elements arranged in the intermediate housing components.

Abstract: In a fuel cell system, a circulation pump provided in a circulation flow path is a two-lobe roots pump configured such that two rotors rotate in opposite directions. An exhaust/drainage portion is provided at a bottom in an internal space of a gas liquid separator provided in the circulation flow path and is configured to collect a liquid separated by the gas liquid separator and discharge the collected liquid via a discharge valve. The gas liquid separator includes an opening that is connected with the circulation pump and that is configured to face in a direction of the exhaust/drainage portion. At a system stop time, when a predetermined condition is satisfied, a controller configured to control operation of the circulation pump causes the rotors of the circulation pump to be rotated in reverse directions from rotations at a system operation time.

Abstract: 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.

Abstract: The invention relates to an electric motor-driven motor-vehicle vacuum pump (1), having a drive shaft (3) which has, in particular, two bearings and extends with a shaft stub (5; 35; 45) into a rotor (8) which is connected fixedly to the shaft stub so as to rotate with it. In the rotor, the shaft stub has a centring region (26; 36; 46) which serves to center the rotor, without guiding the rotor in the axial direction.

Abstract: A drive rotation shaft is rotatably supported by a first slide bearing between a rotor part and a pump rotor, and is rotatably supported by a second slide bearing on its distal end side of a pump rotor fixing part of the drive rotation shaft. Working oil is supplied to the first slide bearing and the second slide bearing. According to this configuration, since the distal end side of the drive rotation part is rotatably supported by the second slide bearing, inclination of the drive rotation shaft is restricted by an inner peripheral surface of the second slide bearing, thereby suppressing occurrence of noise.

Abstract: A rotary positive displacement pump has a front-loading seal arrangement to better accommodate servicing and cleaning of the pump body. The pump includes a sliding seal subassembly disposed in a volume between a central portion of a rotor that is received on a shaft of a gear case and the hub of the pump body. A related method of modifying a rotary positive displacement pump enables a conventional pump with a rear-side seal arrangement to be transformed into a pump having a front-loading seal arrangement. In addition to the reduction of a dead zone in which turbulent flow does not occur by inclusion of the sliding seal subassembly, other modifications to the pump body improve the ability of the pump to be cleaned in place.

Abstract: An air diverter system for a vacuum excavator is disclosed. In a particular embodiment, the system includes a bag house in communication with a debris tank. In addition, the system includes a filter housing secured to a side of the bag house and a valve housing interposed between the bag house and the filter housing. A valve member is mounted within the valve housing and is configured to rotate about an axis to define at least two different passageways for an air flow. The system also includes a selector for rotating the valve member and selectively aligning the passageway for the airflow between a vacuum pump inlet and either the filter housing or the bag house.

Abstract: A hermetically sealed compressor in which the occurrence of heat generation and insulation breakdown is reduced at the connection portion between a lead wire of a motor and an external terminal is configured as follows. The compressor main body and the motor are integrally structured. The flow path of a fluid to be compressed is in fluid communication with the internal space of the motor. The stator of the motor is formed by winding each of a plurality of independent coils in multiple turns. Each of the coils is provided with a separate external terminal.

Abstract: A scavenge gear pump and its method of operation is described. The scavenge gear pump includes a pump housing defining a pump chamber, an inlet passage, an outlet passage, and a fluid injection passage in fluid communication with the pump chamber. The inlet passage receives an admixed fluid at low pressure and the outlet passage the admixed fluid at high pressure from a downstream region of said pump chamber. The fluid injection passage receives a third fluid at an injection pressure for input into the pump chamber. A pair of driveable gears is disposed in the pump chamber. The third fluid is injected directly into the gear meshing area of the pump chamber through the fluid injection passage so that the third fluid fills voids at least between said intermeshing teeth of the driveable gears and so that the second fluid does not occupy the gear meshing area.

Abstract: Elliptical or oval shaped gears of a positive displacement gear pump are disclosed. The gears have specially designed teeth at the ends of the gears' major and minor diameter axes. For example the teeth at the ends regions of the major diameter axes include radially extending wipers or vanes that extend and run against the circular gear case bore walls to seal liquid slip paths at radial running clearance areas between the tips of the gear teeth and the case bores. The pump may also have moveable wearplates on one or both sides of the gears that may be loaded laterally to seal liquid slip paths at lateral running clearance areas between the side faces of the gears and the pump faceplate and backplate.

Abstract: A Roots-type blower may include first and second meshed, lobed rotors disposed in first and second chambers of a housing. Each lobe may have first and second axially facing end surfaces defining a twist angle that may be a function, at least partially, of the number of lobes on each rotor. A blower housing may include a bearing plate that may include one or more internal pressure relief ports. A pressure relief port may be configured to relieve fluid pressure from a trapping area that may form between first and second meshed rotors.

Abstract: An improved positive displacement pump provides improved wear characteristics. Specifically, rotor pads are provided on faces relative to an internal portion of the rotor housing as it relates to an end wall and a rear side of a cover plate. The rotor pads preferably have at least one of anti-galling and/or anti-friction or anti-wear characteristics thereby providing improvements over the prior art. A central member is preferably provided so that pad replacement may be relatively easily performed in the field in clean in place operations.

Abstract: An input shaft assembly is movable along an axis to absorb external impact loads. A biasing member exerts an axial load in a direction counter to potential impact loads. A stop is provided to control the application of biasing loads to control application of such axial load.

Abstract: A rotary piston pump for the delivery of liquids and for the delivery of liquids containing solids. The rotary piston pump includes a pump housing which is provided with an inlet and an outlet. The pump housing includes a lining. Disposed in the pump housing, or inside the lining, are at least two counter-rotating rotary pistons, which form pump spaces during their rotation. During the rotational movement, the rotary pistons are sealed against one another, against the pump housing and against the lining. Disposed in the pump housing and/or in the lining, in the spatial vicinity of the inlet and/or the outlet, are means with which the pulsation can be reduced or even completely prevented.

Abstract: An aircraft turbine engine Fuel Metering Unit (FMU) is provided including a main gear pump having a main drive gear and a main driven gear and a servo gear pump having a servo drive gear and a servo driven gear. The main drive gear and the servo drive gear are received on an input shaft. The main driven gear is mounted to a first shaft oriented parallel to and adjacent a first side of the input shaft. The main driven gear is in meshing engagement with the main drive gear. The servo drive gear is mounted to a second shaft arranged parallel to and adjacent a second, opposite side of the input shaft. The servo driven gear is in meshing engagement with the servo drive gear.

Abstract: A fluid pump includes a housing that defines a suction chamber, a discharge chamber, and a barrier having a first height, wherein the barrier is configured to separate the suction chamber from the discharge chamber. The pump also includes meshed first and second gears rotatably disposed in the housing. The gears are configured to draw relatively low-pressure fluid from the suction chamber, transform the relatively low-pressure fluid into relatively high-pressure fluid, and release the relatively high-pressure fluid into the discharge chamber. The barrier includes first and second portions configured to accept the first and second gears respectively, and a bridge connecting the first and second portions. The bridge is disposed proximately to where the gears mesh and is configured to provide a transition from the first height to a second height to thereby generate gradual re-expansion of the fluid away from the bridge.

Abstract: A pump system for producing fluids from a reservoir using a wellbore having a vertical section with a casing defining an annulus, a transitional section and a horizontal section, and a production tubing having a vertical section and a horizontal section, wherein the system includes a completion with an isolation device in the annulus near the bottom of the vertical section, a gas/liquid separator for receiving produced fluids from the horizontal section, and a vertical lift pump; a continuous flow path from the terminus of the production tubing to the vertical section; a plurality of horizontal pumps in the horizontal section, each having an intake exposed to the reservoir and an outlet in the continuous flow path. The horizontal length of the production tubing is closed to the reservoir except through the horizontal pumps.

Abstract: Embodiments of an oil pump for an engine have an increased pump capacity while maintaining or marginally increasing the overall physical size of the pump. In some embodiments, this increased capacity is reflected in a pump length efficiency ratio, which compares an effective gear length (LG) of first and second pump gears used in the oil pump, to an effective housing length (LH). The effective housing length (LH) is a longitudinal distance between surfaces on opposite ends of the oil pump that must be maintained for the oil pump to fit into an available space. Accordingly, the pump length efficiency ratio indicates how much of the effective housing length (LH) can be occupied by the gears. Alternatively, the pump capacity is measured using an output flow efficiency ratio, which compares a theoretical pump flow (FP) at a given gear speed (SG) to the effective housing length (LH) of the pump.

Abstract: The present invention deals with the analytical definition of a tooth profile for rotors used in gear pumps. The purpose is to obtain a pump characterized by noiseless operation, minimization of vibrations and pressure overoscillations generated in operating conditions at the beginning and end of life, and high specific displacement, in such a way to increase the delivery of the pump in given volume conditions. This profile is characterized by an active profile of the tooth flanks with involute stub-tooth with transverse contact ratio (?t) comprised in the range from 0.4 to 0.45, helical teeth with helical contact ratio (??) comprised in the range from 0.6 to 0.85, circular inactive tooth bottom and top profiles, with center (Of, Ot) and radius (rf, rt) defined by a non-dimensional parameter ? in the range from 1.1 to 1.6.

Abstract: In a pump chamber (12), a male rotor (20) having claw portions and a female rotor (24) having recesses into which the claw portions enter are secured to rotating shafts (18a and 18b), respectively. The female rotor is provided with hollows on an upstream side in the rotational direction of the female rotor relative to a plane L containing the rotating shafts. For the hollows, the disposed position, size and configuration are selected so that a compression pocket P and a discharge opening remain in communication with each other through the hollow throughout the time from when the compression pocket stops communicating with the discharge opening and separates from the discharge opening until the compression pocket gradually reduces to disappear, and so that the hollow stops communicating with the discharge opening at the same time as the compression pocket disappears.

Abstract: A coupling shaft assembly includes a coupling shaft with a first radial shoulder and a second radial shoulder, the first radial shoulder and the second radial shoulder each include at least one slot to provide a lubricant flow path.

Abstract: An air compression device is applied in an air compressor. A rotatable pressure regulating disk and a valve are disposed in a rotor set. When external air enters an air chamber in the rotor set, the air is exhausted after being compressed through rotation of a first rotor and a second rotor. When the two rotors compress the air, a user may control the pressure regulating disk to rotate to advance or postpone exhaust of the air from the valve, so as to change an exhaust pressure in the air chamber to adjust an exhaust volume output by the rotor set. An adjustable air intake disk may further be added, so that timing adjustment can be performed during both air intake and exhaust.

Abstract: A roots type fluid machine includes suction and discharge ports, rotary shafts and a pair of rotors. The rotor has a number n of lobe and valley portions with apex and bottom ends. The lobe portions are located on imaginary lines extending radially from an axis of the rotary shaft. The outer surface of each one of the rotors is generated by rotating an outline of the rotor including an arc and involute and envelope curves around and moving the outline in the direction of the axis. The arc has a radius R and a center located on the imaginary line. The involute curve is formed by an imaginary base circle having a radius r and a center located on the axis. The envelope curve is formed by an arc having a radius R. The number n is four or more. A torsional angle ? is over 360/n degrees.

Abstract: Rotary piston steam engine with equal double rotary pistons is provided with a balanced rotary variable inlet cut-off valve for enhanced efficiency. The exhaust steam from the primary expansion is routed to secondary expansion avoiding back pressure for additional efficiency. The rotary valve has balanced dual inputs and outputs on opposite sides. The exhaust steam from the primary expansion is taken off when the trailing face of the rotary piston passes the inlet port of the expansion chamber housing, the exhaust outlet secondary expansion being placed approximately 180 degrees from the primary expansion inlet in the curved portion of the expansion chamber housing wherein back pressure is not imparted to the primary expansion.

Abstract: A Roots-type blower has first and second meshed, lobed rotors disposed in first and second chambers of a housing. Each lobe has first and second axially facing end surfaces defining a twist angle that is a function, at least partially, of the number of lobes on each rotor, and each lobe further defines a helix angle that is a function of the twist angle and an axial length between the first and second axially facing end surfaces of said lobe. The lobes cooperate with an adjacent surface of the housing to define at least one blowhole that defines a control volume, occurs in a cyclic manner, and moves linearly in a direction toward the outlet port. The blowhole provides communication between adjacent control volumes.

Abstract: A rotary pump having a variable delivery volume, including: a casing; a delivery chamber formed in the casing; at least one delivery rotor which is rotatable in the delivery chamber; an actuating member which is arranged facing a front face of the delivery rotor or surrounds the delivery rotor, and is moveable in the casing for adjusting the delivery volume; the actuating member chargeable with an actuating force which is dependent on a fluid requirement; a track which is formed in the casing and guides the actuating member on an actuating member sliding surface in a sliding contact; and a sliding material which forms at least one of the track and the actuating member sliding surface.

Abstract: In a gear pump according to the present invention, a wall surface portion of a casing (2) includes a drive side partition surface (41) on which tooth crests (11) of a drive gear (10) slide, a driven side partition surface (42) on which tooth crests (21) of a driven gear (20) slide, a suction side inner peripheral surface (43) that connects the drive side partition surface (41) and the driven side partition surface (42) on a suction chamber (3) side, and a discharge side inner peripheral surface (44) that connects the drive side partition surface (41) and the driven side partition surface (42) on a discharge chamber (4) side.

Abstract: An air compression device is applied in an air compressor, and mainly includes a first rotor, a second rotor, a stop disk, a transmission element and a drive element. When external air enters an air chamber in the air compression device, the air is rotated and compressed by the first rotor and the second rotor, and then is exhausted, the transmission element generates axial displacement vertically according to actual requirements on air admission or exhaust, and drives the drive element and the first rotor to displace, so as to change a capacity of the air chamber, and adjust the air output.

Abstract: A supercharger compressor includes a plurality of rotors rotatably mounted in a housing, a first inlet for air, a second inlet for recirculated exhaust gas, and a flow separator. The flow separator is arranged interior the housing and configured to form a slideable seal with at least one rotor of the plurality of rotors, the slideable seal fluidically isolating the first inlet from the second inlet, at least in part, and retarding pressure equalization therebetween.

Abstract: A nonmetallic pump with a gear pump assembly having an adapter spool mounted to an electric motor. The pump assembly is designed to reduce manufacturing costs and to provide access for many service and maintenance tasks to be performed without breaking any of the pipe connections. The pump assembly also includes a splined shaft system and a lubricating fluid circulation system with spiral grooves located inside a pair of bearings disposed on opposite sides of the gear flights. The assembly also includes a replaceable precision liner that surrounds the gear flights to maintain a tight tolerance for optimal performance of the pump. Also, an O-ring disposed inside the front cover of the assembly provides for operation of the pump over a wide temperature variation with relatively loose manufacturing tolerances.

Abstract: A pump includes a pump body defining first and second cavities. First and second rotors are disposed in the first and second cavities between an inlet passage and an outlet passage and are in sealing relationship with each other during rotation of the rotors. A drive transmission mechanism is coupled to the first and second rotors for rotating the rotors in opposite directions. During a revolution of the first rotor, a vane projecting from the first rotor emerges from a recess of the second rotor, passes the inlet passage and the outlet passage, and enters a recess of the second rotor, while the inlet passage remains sealed from the outlet passage.

Abstract: A Roots-type blower has first and second meshed, lobed rotors disposed in first and second chambers of a housing. Each lobe has first and second axially facing end surfaces defining a twist angle that is a function, at least partially, of the number of lobes on each rotor, and each lobe further defines a helix angle that is a function of the twist angle and an axial length between the first and second axially facing end surfaces of said lobe. The lobes cooperate with an adjacent surface of the housing to define at least one blowhole that defines a control volume, occurs in a cyclic manner, and moves linearly in a direction toward the outlet port. The blowhole provides communication between adjacent control volumes.

Abstract: Designs for multiple segment lobe pumps are shown. The designs include pumps using rotors having two lobes to a plurality of lobes and segments that include two segments to a plurality of segments. Designs for both vertical or straight walled conventional lobed rotors as well as helical lobe rotors are shown. The designs are applicable to a variety of rotors and number of segments. In one particular case the designs enable a three lobe helical pump.

Abstract: A high-performance oil pump for pumping oil in an internal combustion engine that eliminates or greatly reduces cavitation in the oil pump, thereby increasing the efficiency and performance of the oil pump. The present invention provides a housing having an inlet for receiving a supply of oil and an outlet for discharging the oil. At least two gears rotatably and matingly are disposed within the housing for pumping the oil from the inlet to the outlet. A pressure regulation circuit is disposed within the housing for balancing oil flow pressure between the inlet and the outlet by redirecting a portion of the oil from the outlet to the inlet when said oil flow pressure reaches a predetermined level at the outlet in order to reduce or eliminate cavitation of oil in the oil pump.

Abstract: A scavenge gear pump and its method of operation is described. The scavenge gear pump defines a pump chamber in which a pair of toothed gears are rotatably driven to pump an oil-air mixture from an inlet passage where the oil mixture is at low pressure, to an outlet passage where the air and oil has separated and is at high pressure. The gears are intermeshed in a meshing area between the inlet and the outlet passages and an oil nozzle is provided in a downstream region disposed in relation to the gear meshing area to inject oil under pressure in that area to occupy the volumes between the intermeshed gear teeth whereby to prevent air bubbles from being carried back to an upstream region adjacent the inlet passage. Accordingly, the volumetric efficiency of the pump is improved and it is more tolerant to back pressure.

Abstract: A gear pump has a face plate 2 cooperating with central plate 24 defining a pump chamber 21 holding gears 16. The pump chamber 21 is in fluid communication with drive chamber 32 holding the rotor 40 of an electric motor. An O-ring 18 may be used to seal the face plate 2. Other elements may be sealed using a permanent seal such as glue.

Abstract: A dry pump includes: a plurality of cylinders; a pump chamber formed in each of the cylinders; a division wall separating pump chambers adjacent to each other; a plurality of rotors contained inside pump chambers; a rotating shaft that serves as an axis of rotation of the rotor; and a cooling medium path which is formed inside the division wall and through which a cooling medium passes.

Abstract: A supercharger is provided, comprising a plurality of rotatable supercharger rotors each having a plurality of interleavable lobes configured to move air from an inlet to an outlet of the supercharger. Inner chambers in the lobes define an end opening and perforated end faces, at the end openings defining at least one port, having a length and a diameter. The at least one port is configured to operate with an associated air mass in the inner chamber to attenuate sound adjacent to the end opening.

Abstract: A pressure equalization system reduces or eliminates a pressure differential across supercharger rotor shaft seals. Under high boost, rotor shaft seals often fail, allowing hot compressed air into an oil lubricated space containing rotor bearings and gears (and vented to ambient pressure), reducing oil lubricating effectiveness and resulting in increased wear and failure. Under low or non boost operation, the pressure differential is reversed causing the lubricating oil to leak into the supercharger interior and accelerated rotor seal wear. The pressure equalization system includes flow restrictive seals on both rotor shafts, separated from the rotor shaft seals by vented spaces, thereby isolating the rotor shaft seals from boost or vacuum in the supercharger interior and reducing or eliminating the pressure differential across the rotor shaft seals. Maintaining close to atmospheric pressure on both sides of the rotor shaft seals during boost and vacuum operation reduces wear and failures.

Abstract: A fuel pump for a direct injection internal combustion engine having a housing defining a pump chamber. Driven and idler toothed gears are rotatably mounted within the pump chamber so that the driven and idler gears are in mesh with each other at a predetermined location in the pump chamber. A fluid inlet is formed through the housing and open to an inlet subchamber in the pump chamber. A fluid outlet is also formed through the housing and open to an outlet subchamber in the pump chamber. A pressure relief passageway fluidly connects the inlet subchamber to the outlet subchamber and a valve is disposed in series with the pressure relief passageway. A control circuit controls the actuation of the valve to control the pump pressure at the pump outlet.

Abstract: An apparatus includes a rotation body having one or more rotary shafts having projections, and a cleaning part disposed adjacent to the projections, having one or more rotation holes into which the one or more rotary shafts are inserted, respectively, and configured to flow a cleaning material into the one or more rotation holes.

Abstract: A multistage vacuum pump has a pair of rotors disposed in each of pump chambers connected in stages. As the rotors rotate while intermeshing, a suctioned gas is compressed and discharged, angles of the rotors are adjusted so that a phase angle ?? of the rotors of adjacent pump chambers relative to a rotation angle C of the rotors during a single cycle of the pump chambers from intake to discharge and the number of stages S of the rotors satisfies ???C/S. When a rotor angle is ?1, an mth stage rotor angle is ?m, and an nth stage rotor angle is ?n in order from an upstream side of a gas flow direction, relationships of ?1<?m??n and ?1<?n, where n and m are natural numbers and n>m, are satisfied.

Abstract: The present invention provides a dry pump including: a center cylinder which includes: a plurality of pump chambers containing an upper stage pump chamber that communicates with an intake port and a lower stage pump chamber that communicates with a discharge port; a plurality of rotors contained in the plurality of the pump chambers; a rotating shaft that is a rotation axis of the rotor; and a side face on which a communication hole is formed, the side face being intersected by the rotating shaft extending in the axial direction, and being provided adjacent to the lower stage pump chamber, and a side cover which covers the side face with the communication hole to form a space.