A pair of co-operating screw rotors including a male rotor and a female rotor. The male rotor and the female rotor have helically extending lobes and intermediate grooves configured to intermesh with one another. Each groove of the female rotor has a first flank including at least three concave sections. A first section includes or is disposed immediately adjacent the radially innermost point of the groove. A second section is shaped as a circular arc with a radius having its center located outside the pitch circle. A third section is shaped as a circular arc with a radius having its center located outside the pitch circle. The radius of the third section is greater than the radius of the second section, which is greater than the radial distance between a pitch circle of the female rotor and the radially innermost point of the groove.

A method of machining, with a formed tool, a first rotor and a second rotor with mutually complementary meshing threads involves rotating a first workpiece about a longitudinal axis of the workpiece. The tool makes one or more passes along the longitudinal axis of the workpiece as the workpiece rotates so as to remove material, thereby forming the flanks of each helix of the first rotor's thread. The value of at least one of the parameters that collectively define the relative position and relative movement of the workpiece and formed tool is varied during each pass so as to vary the lead of the thread. The above steps are repeated for a second workpiece, thereby forming the second rotor. Adjustments are made to at least one of said parameters during one or more of the passes in order to maintain mutually complementary shapes of the threads of the rotors.

A method of machining, with a formed tool, a first rotor and a second rotor with mutually complementary meshing threads involves rotating a first workpiece about a longitudinal axis of the workpiece. The tool makes one or more passes along the longitudinal axis of the workpiece as the workpiece rotates so as to remove material, thereby forming the flanks of each helix of the first rotor's thread. The value of at least one of the parameters that collectively define the relative position and relative movement of the workpiece and formed tool is varied during each pass so as to vary the lead of the thread. The above steps are repeated for a second workpiece, thereby forming the second rotor. Adjustments are made to at least one of said parameters during one or more of the passes in order to maintain mutually complementary shapes of the threads of the rotors.

A rotor pair for a compressor block of a screw machine includes a secondary rotor that rotates about a first axis and a main rotor that rotates about a second axis. The number of teeth of the main rotor is 3 and the number of teeth of the secondary rotor is 4. The relative profile depth of the secondary rotor is at least 0.5 rk1 is an addendum circle radius drawn around the outer circumference of the secondary rotor and rf1 is a dedendum circle radius starting at the profile base of the secondary rotor. The ratio of the axis distance of the first axis from the second axis and the addendum circle radius rk1 is at least 1.636.

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.

Provided is an internal gear pump. The shape of any one of a plurality of external teeth and a plurality of internal teeth of the pump is formed on the basis of formulae (1)-(5). Formula (1): r=ro−dr.Math.cos θ, Formula (2): Px=(ro−dr)+1/4 dr{1−cos (2θ)}, Formula (3): Py=1/4 dr{−2θ+sin (2θ)}, Formula (4): Qx=Px−r.Math.cos θ, Formula (5): Qy=Py+r.Math.sin θ.

An internal gear pump includes a housing having a pump chamber in which an inner rotor and an outer rotor are arranged. A suction port in communication with a suction path and a discharge port in communication with a discharge path are formed at the housing. The pump chamber includes an inner wall having a suction region at a suction port-side and a discharge region at a discharge port-side. The suction region includes a first suction region extending towards the suction path from a pressing point, where the outer rotor is pressed when the internal gear pump is in operation, and a second suction region between the first suction region and the discharge region. A groove that enlarges a clearance between the outer rotor and the inner wall is formed in the first suction region, but the groove is not formed in the second suction region.

A screw spindle pump having a housing hi which a drive spindle and at least one running spindle having profile assemblies which engage inside each other are received, the free end of the drive spindle and the end portion of the running spindle being supported on a plate which is arranged in the housing, the plate having two faces which are inclined in opposing directions relative to each other and which form a V-shape and on which one of the spindles is supported, respectively.

A scroll compressor is provided which comprises: a housing; a driving motor; an orbiting scroll rotated by the driving motor; a fixed scroll; a suction port provided in the housing and suctioning a refrigerant; an oil separator in the housing at one side of the fixed scroll; and a discharge port for discharging, to the outside of the housing, the refrigerant from which oil is separated in the oil separator. The scroll compressor includes an intermediate housing; a back pressure chamber in the intermediate housing at one side of the orbiting scroll, first and second back pressure seal members in the intermediate housing; a plurality of anti-rotation rings in the intermediate housing; and a plurality of anti-rotation pins at the orbiting scroll to be inserted into each of the plurality of anti-rotation rings.

Disclosed is a pump system for a semiconductor chamber includes a housing having a front chamber and a rear chamber, a roots-type rotor provided to the front chamber of the housing, a screw-type rotor provided to the rear chamber, a shaft member coupled through the roots-type rotor and the screw-type rotor, and a driving motor provided to the outside of the housing in such a way as to be axially connected to the shaft member to provide power for driving the rotors. A fluid pipe is provided to the outside of the housing to connect the front chamber and the rear chamber. The fluid pipe is provided with a heater and/or a cooler to heat or cool the fluid flowing through the fluid pipe.