Abstract: The invention relates to a method of manufacturing a rotor (12) for a helical screw machine that includes a metal shaft (2) and helical lobes (9) mutually separated by intermediate grooves (13), comprising the steps of providing the shaft (2) with a blind axially extending passageway (10); connecting the passageway (10) with the barrel surface of the shaft (2) by means of at least one channel (11) extending outwardly from the shaft; inserting the rotor shaft (2) in a mold (1) that includes two mutually spaced end-walls (4, 5) which have respective rotor shaft receiving openings (6 and 7), said openings (4, 5) embracing the rotor shaft (2, 19) at least in a generally sealing fashion; heating the mold (1) and the shaft (2) to the curing temperature of the polymer; delivering polymer-forming materials to the mold (1); maintaining the barrel wall (3) of the mold (1) at said curing temperature until the polymer has cured; and removing the rotor from the mold (1).

Abstract: The present invention relates to a compressor (1) that has an associated coolant circulation system (1, 4, 6, 8, 11, 13), and also to a method of maintaining a low bacteria content in the coolant circulating system (1, 4, 6, 8, 11, 13), in which method gas and coolant are supplied to the compressor (1) during running of the system and the gas is compressed in the compressor (1) to an outlet pressure, the gas and the coolant are removed together from the compressor (1) and then separated into a respective gas and a liquid phase, whereafter the gas is passed to a recipient and the liquid is cooled before being returned to the compressor as coolant. The method is characterized by creating bacteria-killing conditions intermittently in the system by appropriating the heat-generating capacity of the compressor (1) to raise the temperature of the circulating coolant to at least 55° C. for a duration of at least 15 seconds.

Abstract: The present invention relates to a compressor (1) that has an associated coolant circulation system (1, 4, 6, 8, 11, 13), and also to a method of maintaining a low bacteria content in the coolant circulating system (1, 4, 6, 8, 11, 13), in which method gas and coolant are supplied to the compressor (1) during running of the system and the gas is compressed in the compressor (1) to an outlet pressure, the gas and the coolant are removed together from the compressor (1) and then separated into a respective gas and a liquid phase, whereafter the gas is passed to a recipient and the liquid is cooled before being returned to the compressor as coolant. The method is characterised by creating bacteria-killing conditions intermittently in the system by appropriating the heat-generating capacity of the compressor (1) to raise the temperature of the circulating coolant to at least 55° C. for a duration of at least 15 seconds.

Abstract: A helical screw compressor is provided having a first compressor stage and a second compressor stage. The helical screw compressor includes a first male rotor and a first female rotor in the first compressor stage, and a second male rotor and a second female rotor in the second compressor stage. A connecting duct is provided between an outlet of the first compressor stage and an inlet of the second compressor stage, and a conduit is provided having a first end communicating with the connecting duct and a second end branching off into a first line and a second line. The first line is coupled to the first compressor stage for injecting liquid into the first compressor stage, and the second line is coupled to the second compressor stage for injecting liquid into the second compressor stage.

Abstract: The present invention relates to a variable capacity helical screw compressor for compressing a gaseous medium, usually air. The compressor includes at least one lift valve (1) which connects with a first compression chamber in the compressor.

Abstract: The invention relates to a rotary screw machine that is completely oil-free. Known rotary screw machines with cooling, sealing, lubrication of the screw rotors and oil-lubrication and oil-cooling of the bearings have been replaced with water-lubricated and water-cooled bearings. Each screw rotor (102) is mounted in a water-lubricated radial slide bearing (1) and one trunnion (31) of the rotor co-acts with a water-lubricated thrust bearing (9, 10) which acts both as an hydrodynamic and an hydrostatic bearing. The trunnion bearing housing (21) is in fluid connection with the rotor housing, both along the trunnion and via a conduit (27) from the bearing housing interior to the gas inlet (108) of the screw rotor or via a channel which is cut-off from said inlet.

Abstract: A rotary screw compressor having one or more stages (10, 20) is provided with a lift valve (14, 24) on each stage for unloading the compressor at starting up and rest periods. Each lift valve (14, 24) is biased by a spring (15, 25) towards an open position and can be closed by an actuator (17, 27). Each valve actuator (17, 27) is automatically controlled by an air conduit (32) establishing air communication between the discharge channel (23) of the compressor and each valve actuator (17, 27).

Abstract: A rotary displacement compressor having an inlet channel for introducing low pressure gas, an outlet channel through which compressed gas escapes, and at least one rotor mounted in bearings and operating in a working space. The compressor includes a liquid injector for injecting liquid into the working space, a liquid separator provided in the outlet channel for separating liquid from the compressed gas, and a pressure liquid conduit connecting the liquid separator and the liquid injection port. A bearing lubrication circuit includes a tank, a pump, a supply conduit for supplying liquid from the pump to the bearings in which the rotor is mounted, a withdrawal conduit for withdrawing liquid from the bearings to the tank, and a pump inlet conduit for supplying liquid from the tank to the pump.

Abstract: A rotary screw compressor having a balancing piston device for balancing an axial gas force exerted on a pair of rotors during operation of the rotary screw compressor. The balancing piston device is exposed in one axial direction to a high pressure source on at least one first pressure surface, and in an opposite axial direction to one of a low pressure source and an intermediate pressure source on at least one second pressure surface. A valve is provided for selecting the low or the intermediate pressure source connection with respect to the at least one second pressure surface, whereby the thrust balancing force can be adapted to different working conditions such as starting up and full load operation in order to avoid underbalancing or overbalancing of the axial gas force.

Abstract: A rotary screw compressor having two rotors, liquid injection, a liquid separator (10), and a hydraulic thrust balancing piston (11) connected to at least one of the rotors. In order to vary the balancing force if suction and delivery pressures vary, there is provided first (5) and second (4) throttling devices in the return pipe from the oil separator to the liquid injection port. Between the first and second throttling devices there is a connection to a pipe branch (7) which ends in a cylinder (14) which houses the balancing piston (11). The balancing pressure acting on the balancing piston (11) will thereby vary as suction and delivery pressures vary in a way determined by the relation between the degree of throttling in the two throttling devices.

Abstract: A rotary screw compressor for oil-free air, wherein at least one of the shaft journals (11) of the rotors (10) has a seal arrangement between the rotor (10d) and an oil-lubricated bearing (12). The seal arrangement includes at least three frictionless seals (13, 14, 15) separated by annular chambers (16,17). The outermost annular chamber (17) is connected to a source of pressurized air through a supply channel (19) for supplying blocking air to the seal, and another (16) of the annular chambers communicates with a withdrawal channel (18).

Abstract: A rotor for a rotary screw machine has helical lobes (12) and grooves (14). A shell structure (18) forming the external surface of the rotor is made of pressed metal power. The rotor is manufactured by cold isostatic pressing of a powder in a vessel having a surface shaping rotor. The pressure is applied radially by means of a cast bag in which high pressure liquids acts. After the pressing process, the rotor blank is sintered and attached to a shaft (16).

Abstract: The invention relates to a rotary screw machine in which the shaft journals (20, 22) of the rotors (10) are journalled in a main thrust bearing (24) and a thrust balancing bearing (26). The thrust balancing bearing (26) is preloaded by springs (36) and by fluid pressure means (40, 44). According to the invention the fluid pressure means (40, 44) can excert a force on the thrust balancing bearing (26) in either axial direction. This increases the possibility for an optimal distribution of the forces on the thrust bearings (24, 26) at various running conditions.

Abstract: A method of manufacturing rotors having helical lands and intermediate grooves wherein a multi-layer rotor body (2) is moulded or otherwise formed on a shaft (1) to only a small degree of accuracy, whereafter an outer layer (3) of polymer-based material is moulded on the rotor body to a high degree of accuracy. For the purpose of eliminating shrinkage-induced distortion of the lands of the rotor body (2) subsequent to applying the outer layer, the rotor body is produced in a multiple of layers (21, 22), by casting or like moulding processes, with each of the body layers having a thickness which is greater than that of the high accuracy outer layer (3).

Abstract: A rotor for a rotary screw machine having helical lobes and intermediate grooves, the rotor having a core including a shaft 1 of a first material and a rotor body 2 of a second material mounted on the shaft. The surface of the rotor is coated with a plastic layer 3.

Abstract: A screw compressor of the kind incorporating at least one male rotor and one female rotor, with helically extending lands and grooves. The female rotor (1) is injection moulded from a plastics material having a modulus of elasticity of at most 25,000 N/mm.sup.2. The lands (3) of the female rotor have a thickness (a) which is so adapted to the modulus of elasticity of the plastics material as to allow the lands to be deflected resiliently when clashing with the other rotor (2), as a result of dimensional deviations of the order likely to occur during hardening or curing of the plastics material, or at prevailing temperature variations, but not as a result of the pressure exerted by the working fluid. Due to the injection moulding the surface smoothness is fine enough to make subsequent finishing unnecessary and damages caused by lack of machining are avoided because of the resilient deflecting of the lands of the female rotor when clashing with the other rotor.

Abstract: An oil-free rotary gas-compressor system includes an oil-free rotary gas-compressor (2) having a high, built-in pressure ratio and an injector arrangement (13) for injecting a vaporizable liquid, preferably water, into the compressor (2) for cooling the gas during the compression process. It is known in high-speed compressors to utilize water injection which is so restricted that the water is completely vaporized, to thereby obtain a good cooling effect. The efficiency of the compressor is limited, however. In known systems, high compressor efficiencies are obtained by injecting large quantites of water, although the compressor speed must then be considerably reduced, resulting in a lower compressor capacity.