Abstract: 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.

Abstract: A method and apparatus for controlling the flow of a working medium through an expansion device in a closed heating system which also includes a condenser, a pump and a boiler. The expansion device is a helical screw rotor expander that has an inlet port with an inlet line connected thereto, and an outlet port. The expansion device drives an energy producing device, such as a generator. The helical screw rotor expander has an intermediate pressure port between the inlet port and the outlet port, and a branch line is connected between the intermediate pressure port and a branching point in the inlet line. A valve is in the branch line. The flow of working medium through the valve to the intermediate pressure port is controlled as a function of a state parameter.

Abstract: A helical screw rotor compressor is provided which includes a rotor housing that includes a barrel wall between two parallel end walls, an inlet port at a first end and an outlet port at a second end. The compressor has an internal shape corresponding to two parallel and mutually intersecting cylinders. The compressor includes two rotors which each include a shaft and a rotor body surrounding the shaft. The rotor bodies have parallel end surfaces adjacent to the end walls of the rotor housing, and each include helical lobes that have a crown, a first or leading flank surface on a first side of the crown and a second or trailing flank surface on a second side of the crown. The second or trailing flank surfaces of the lobes have a beveled or chamfered region adjacent to the end surface of the rotor body near the outlet port.

Abstract: A helical screw rotor compressor is provided which includes a rotor housing that includes a barrel wall between two parallel end walls, an inlet port at a first end and an outlet port at a second end. The compressor has an internal shape corresponding to two parallel and mutually intersecting cylinders. The compressor includes two rotors which each include a shaft and a rotor body surrounding the shaft. The rotor bodies have parallel end surfaces adjacent to the end walls of the rotor housing, and each include helical lobes that have a crown, a first or leading flank surface on a first side of the crown and a second or trailing flank surface on a second side of the crown. The second or trailing flank surfaces of the lobes have a beveled or chamfered region adjacent to the end surface of the rotor body near the outlet port.

Abstract: A new rotor for a positive displacement compressor is provided which includes a non-rotating rotor shaft, a rotatable rotor body having end surfaces and surrounding the rotor shaft, and a mechanism for rotating the rotor body around the shaft. The rotor may be either a male rotor or a female rotor, and a positive displacement compressor is also provided which includes the new male rotor, the new female rotor, and an internal drive mechanism. Such positive displacement compressor includes radial induction bearings, and the internal drive mechanism replaces an external drive mechanism.

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: A helical screw rotor machine is provided which has at least one trunnion having an axial thrust surface located in a chamber filled with pressure medium and actuated axially by the pressure medium. A casing is closely fitted around the trunnion. The casing has an outer end which is connected to a bottom wall that includes a hole in its center, and the casing is rotatably and slidably mounted on the trunnion and is movable between a first axial position in which the bottom wall is spaced from an end wall of the chamber and a second axial position in which the bottom wall is in abutment with said end wall. A supply channel is connected to an opening in the end wall of the chamber opposite the hole in the bottom wall of the casing for controlled delivery of the pressure medium into the casing.

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: A helical screw rotor machine is provided which has at least one trunnion having an axial thrust surface located in a chamber filled with pressure medium and actuated axially by the pressure medium. A casing is closely fitted around the trunnion. The casing has an outer end which is connected to a bottom wall that includes a hole in its center, and the casing is rotatably and slidably mounted on the trunnion and is movable between a first axial position in which the bottom wall is spaced from an end wall of the chamber and a second axial position in which the bottom wall is in abutment with said end wall. A supply channel is connected to an opening in the end wall of the chamber opposite the hole in the bottom wall of the casing for controlled delivery of the pressure medium into the casing.

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 pair of co-operating screw rotors include a male rotor and a female rotor each having helically extending lobes and intermediate grooves which intermesh. The male rotor has an external radius R.sub.M and a pitch radius R.sub.MP defining a pitch circle C.sub.MP, and each lobe of the male rotor in a predetermined section has a leading lobe flank and a trailing lobe flank which are substantially convex. The predetermined section is perpendicular to an axis O.sub.M of the male rotor and an axis O.sub.F of the female rotor, and each lobe of the female rotor in the predetermined section has a leading lobe flank and a trailing lobe flank which are substantially concave. Each lobe of the male rotor and each lobe of the female rotor has an asymmetric profile in the predetermined section. Each of the leading flank and the trailing flank of at least one of the male rotor lobes has a male circular arc segment having a center of curvature A.sub.1M, A.sub.2M and a radius of curvature R.sub.1, R.sub.2.

Abstract: A regenerative heat exchanger having a first part which is essentially cylindrical and which contains a regenerator mass, and a second part which comprises axially directed inlet ducts and outlet ducts for heat emitting and heat absorbing media. The inlet and outlet ducts are separated from each other by sector shaped plates positioned for sealing purposes close to end surfaces of the first part, and the sector shaped plates are pivotally connected to axially fixed center plates positioned at ends of the first part and attached to the second part. At least one cylindrical stop bar is provided at a radial outer end of each of the sector shaped plates for setting a clearance between the radial outer ends of the sector shaped plates and respective edge flanges provided at each end of the first part.

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 refrigeration system whose refrigeration capacity can be regulated continuously in a simple and reliable manner by gradually restricting the flow of refrigerant through an economizer channel to the compressor. The refrigeration system includes a rotary screw compressor, a condenser, a first pressure reducing valve, an economizer, a second pressure reducing valve, and an evaporator connected in sequence by respective channels. An outlet channel connects the evaporator to a low pressure inlet port of the rotary screw compressor to form a closed loop for a refrigerant. An economizer channel selectively connects the economizer to a closed working chamber of the rotary screw compressor. An adjustable valve provided in the economizer channel continuously regulates a mass flow of gaseous refrigerant through the economizer channel. And a sensing device senses a value of at least one parameter of the refrigerant in the closed loop which is indicative of a required refrigeration capacity.

Abstract: The invention relates to a refrigeration system of the air cycle cooling system type, also called reversed Brayton cycle in which the air flow through compressor means (12, 16), heat exchanger means (24) for withdrawal of heat from the compressed air and finally expander means (22) from where it is delivered to perform cooling. According to the invention the system includes heat load means (41) having a large flow resistance, creating a considerable over-pressure at the expander outlet (23). A rotary screw machine is included in the expander (22) and also in the compressor means (12, 16), which latter screw rotor machine (12) is driven solely by the screw rotor machine (22) of said expander means.

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 cooled air cycle system having a compressor (1) for compressing air, heat exchangers (3,4,5) for cooling the compressed air, a water separator (6) for withdrawing water from the compressed air, and an expander (2) for expanding the air back to substantially compressor inlet pressure, which air is cooled and can be used, for example, for air-conditioning. A regenerative dryer (7) is provided in conduits between the compressor (1) and the expander (2). The dryer (7) includes a water adsorbing section (18), which alternatingly is brought into contact with the compressed air at at least two locations (A,B,C). In one location (B), which is after the first heat exchanger (3) and the water separator (6), water is adsorbed from the air by the adsorbing section (18), and in another location (A), which is before the first heat exchanger (3) and the water separator (6), the adsorbing section (18) is regenerated in that the adsorbed water is brought away by the air.