A vacuum pump screw rotor, comprising at least two helical displacer elements on a rotor shaft. The at least two displacer elements have different pitches, but the pitches of each displacer element are constant. Furthermore, the displacer elements each have a helical recess, each having a contour that remains the same over its entire length. Hereby, a suction-side displacer element has a recess having an asymmetric contour, and a pressure-side displacer element has a recess having a symmetrical contour.

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 screw compressor for a utility vehicle includes at least one housing and at least one air-oil separator holder arranged at the housing. The air-oil separator holder is manufactured from a non-corrosive material. A relief valve is provided, which is arranged in the air-oil separator holder and by which the interior of the screw compressor can be relieved of pressure.

A low cost scroll device and methods of manufacturing the same are described. The scroll device includes, for example, a drive pin hole and bearing bores machined into a scroll of the scroll device from the same side as the involute of the scroll; idler shaft assemblies with no more than one bearing in the orbiting scroll for mechanically coupling the orbiting scroll to the fixed scroll; and an epoxy coating applied using a process that requires assembly of the scroll device only once.

A gear configured to rotate as a unit with a shaft, the gear includes: a plurality of annular grooves formed on both side surfaces of the gear in a direction of a rotation axis of the shaft, at least partially overlapped when viewed from the direction of the rotation axis, and at least partially overlapped in a radial direction with respect to the rotation axis.

A multi-stage rotary piston pump comprising two shafts in a housing, which support multiple rotary pistons. Corresponding rotary pistons form a respective rotary piston pair, wherein multiple rotary piston pairs are provided which form a respective pump stage. Neighboring pump stages are each connected to one another via connection channels. The multi-stage rotary piston pump also comprises a pump inlet that is connected to the first pump stage, as well as a pump outlet that is connected to the last pump stage. The built-in volume ratio is at least 15, so that high pumping capacities of at least 1500 m.sup.3/h can be achieved.

A structural frame is provided. The structural frame includes a bottom surface, first and second cylinder block sidewall engaging surfaces, the first and second cylinder block sidewall engaging surfaces positioned above the bottom surface at a height that is above a centerline of a crankshaft support included in a cylinder block when the structural frame is coupled to the cylinder block.

A linear compressor and a method for manufacturing a linear compressor are provided. A piston of a linear compressor may include a surface treatment body made of aluminum or an aluminum alloy; a first surface treatment provided on an outer surface of the surface treatment body by a first vacuum deposition process; and a second surface treatment provided on an outer surface of the first surface treatment by a second vacuum deposition process.

A hydraulic module including a cylinder (2) which accommodates a piston (3) which delimits a chamber (4) which receives the brake fluid. The piston (3) is connected to the electric motor (5) of the module (1) by a recirculating ball screw (6), whose core (61) is fixedly connected to the piston (3) which itself is guided by needles (21) which are parallel to the axis (xx) of the piston (3) and with which notches (351) on the circumference of the piston (3) interact. The piston (3) is a piece, which is formed from a cylindrical body (32) made from anodized aluminum and an outer ring (35) made from steel, which is forcibly mounted on the edge (34) of the piston and is provided with notches (351) with a cross section which corresponds to the effective cross section of the needles (21).

A ring carrier for a piston for an internal combustion engine is formed by a carrier body having an outer circumferential surface, an inner circumferential surface, a top surface and a bottom surface, with at least one ring groove formed in the outer circumferential surface. An outer circumferential portion of the ring carrier is formed of gray iron, and an inner circumferential portion is formed of ductile iron. A transition region between the outer circumferential portion and the inner circumferential portion intersects upper and lower flanks of the ring groove, so that an outer circumferential extent of the flanks is formed of gray iron and an inner circumferential extent of the flanks is formed of ductile iron.