The pump device includes a housing defining insertion holes for a rotation shaft, inlets and outlets, and an internal passage; a first pump element; and a second pump element. The internal passage includes first suction passages communicating from the inlet to a first suction port facing the first end surface of the first pump element directed to one end side; first discharge passages communicating from a first discharge port facing the first end surface to the outlet; second suction passages passing around the first pump element to communicate from the inlet to a second suction port facing the second end surface of the second pump element; and second discharge passages passing around the first pump element to communicate from a second discharge port facing the second end surface to the outlet.

A scroll compressor includes scroll members that are made of austempered grey iron in whole or in part. The austempering process can increases fatigue strength and toughness of a grey iron while maintaining its good machinability and vibration damping characteristics. Use of austempered grey iron scroll members allows the scroll compressor to improve its capacity, efficiency, and durability.

A scroll compressor is provided that may include a casing; a drive motor provided at an inner space of the casing; a rotational shaft coupled to a rotor of the drive motor, and rotated together with the rotor; a frame provided below the drive motor; a fixed scroll provided below the frame, and having a fixed wrap; and an orbiting scroll provided between the frame and the fixed scroll, having an orbiting wrap so as to form a compression chamber including a suction chamber, an intermediate pressure chamber, and a discharge chamber, by being engaged with the fixed wrap. In a state in which a center of the fixed scroll and a center of the orbiting scroll are substantially the same, an interval between the fixed wrap and the orbiting wrap gradually increases towards the suction chamber from the discharge chamber.

A compression device includes at least: two interleaved scrolls each of which is made of an aluminum alloy, one of the scrolls, being a fixed scroll (3), and is fixed and the other scroll, which is an orbiting scroll and moves eccentrically without rotating. Also included are anti-rotation means made of an aluminum alloy and configured to allow anti-rotation of the orbiting scroll. The compression device also includes one flat thrust bearing configured to axially contain the orbiting scroll and is made of aluminum alloys or grades of cast iron. The compression device also includes coatings for promoting friction between the fixed scroll, the orbiting scroll, the anti-rotation means and the flat thrust bearing.

A scroll compressor is provided that may include a casing; a drive motor provided at an inner space of the casing; a rotational shaft coupled to a rotor of the drive motor, and rotated together with the rotor; a frame provided below the drive motor; a fixed scroll provided below the frame, and having a fixed wrap; and an orbiting scroll provided between the frame and the fixed scroll, having an orbiting wrap so as to form a compression chamber including a suction chamber, an intermediate pressure chamber, and a discharge chamber, by being engaged with the fixed wrap. In a state in which a center of the fixed scroll and a center of the orbiting scroll are substantially the same, an interval between the fixed wrap and the orbiting wrap gradually increases towards the suction chamber from the discharge chamber.

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 stator of a dry vacuum pump is provided, the pump having at least two rotors to rotate in a synchronised manner in opposite directions in a central housing to drive a gas to be pumped between a suction inlet and a delivery outlet, the stator including an outer part made of cast iron containing less than 5% nickel, and a stator insert wherein is arranged the central housing configured to receive the at least two rotors, the stator insert containing at least 10% nickel, the outer part of the stator having been cast on the stator insert. There is also provided a rotary shaft configured to bear and drive in rotation at least one rotor of a vacuum pump, a dry vacuum pump having at least one such stator and/or at least one such shaft, and a method for manufacturing such a stator and/or such a rotary shaft.

The pump device includes a housing defining insertion holes for a rotation shaft, inlets and outlets, and an internal passage; a first pump element; and a second pump element. The internal passage includes first suction passages communicating from the inlet to a first suction port facing the first end surface of the first pump element directed to one end side; first discharge passages communicating from a first discharge port facing the first end surface to the outlet; second suction passages passing around the first pump element to communicate from the inlet to a second suction port facing the second end surface of the second pump element; and second discharge passages passing around the first pump element to communicate from a second discharge port facing the second end surface to the outlet.

A compressor includes a housing, and an anticorrosive coating covering a surface of the housing. The anticorrosive coating includes a base layer applied on the surface of the housing, and a surface layer applied on the base layer. Both the base layer and the surface layer are organic coatings. Thus, the housing of the compressor is effectively separated from the external environment by means of the two organic coatings, so as to ensure that the compressor is not corroded; moreover, the anticorrosive coating does not contain a metal coating, thereby preventing the problem of the compressor being severely corroded due to an exposed metal coating.

An object of the invention is to provide a compressor that includes a corrosion-resistant film formed on the surface of a casing having a complicated shape. A compressor pumps gas in a compression chamber formed by a casing, the casing is made of cast iron, and a layer made of a mixture of iron nitride and a compound of iron, nitrogen, and carbon and an oxide layer made of triiron tetraoxide are formed on the surface of the casing. Accordingly, since the corrosion resistance of the casing, which includes a film formed by a gas soft-nitriding treatment and an oxidation treatment, is improved, the generation of rust is suppressed. Therefore, it is possible to provide a compressor in which galling or sticking caused by rust occurs less.