Abstract: In a screw compressor for a refrigerator, suction-side rotor shafts of screw rotors are supported rotatably by angular ball bearings for forward thrust load, an annular gap is formed between the angular ball bearings and a suction-side bearing casing, and outermost end faces of outer rings of the angular ball bearings are pressed through a spring member by means of a presser member fixed to an end face of the suction-side bearing casing, whereby the angular ball bearings are held movably in the thrust direction within the suction-side bearing casing. Discharge-side rotor shafts of the screw rotors are supported rotatably by angular ball bearings for forward thrust load and an angular ball bearing for reverse thrust load which are held at predetermined certain positions within a discharge-side bearing casing. A screw compressor which permits structural simplification, reduction of size, and lightening of a maintenance burden is provided.

Abstract: A screw refrigerating apparatus comprising a refrigerant circulating passage including a screw compressor, a condenser, an expansion valve, and an evaporator is constituted such that a bypass flow passage branching at a part of the refrigerant circulating passage between the condenser and the expansion valve, routing through throttle means, and communicating with a rotor room within the screw compressor is provided. The screw refrigerating apparatus is capable of simplifying the structure, decreasing the size, decreasing labor of the maintenance, and the like.

Abstract: In a screw compressor for a refrigerator, suction-side rotor shafts of screw rotors are supported rotatably by angular ball bearings for forward thrust load, an annular gap is formed between the angular ball bearings and a suction-side bearing casing, and outermost end faces of outer rings of the angular ball bearings are pressed through a spring member by means of a presser member fixed to an end face of the suction-side bearing casing, whereby the angular ball bearings are held movably in the thrust direction within the suction-side bearing casing. Discharge-side rotor shafts of the screw rotors are supported rotatably by angular ball bearings for forward thrust load and an angular ball bearing for reverse thrust load which are held at predetermined certain positions within a discharge-side bearing casing. A screw compressor which permits structural simplification, reduction of size, and lightening of a maintenance burden is provided.

Abstract: A screw refrigerating apparatus comprising a refrigerant circulating passage including a screw compressor, a condenser, an expansion valve, and an evaporator is constituted such that a bypass flow passage branching at a part of the refrigerant circulating passage between the condenser and the expansion valve, routing through throttle means, and communicating with a rotor room within the screw compressor is provided. The screw refrigerating apparatus is capable of simplifying the structure, decreasing the size, decreasing labor of the maintenance, and the like.

Abstract: The present invention provides a screw compressor for refrigerating apparatus capable of controlling the rotational speed of a motor to be suitable for cooling heat load by simply controlling an inverter, without causing the overload of the motor. The screw compressor 1A for refrigerating apparatus 10A, which uses a motor 22 controlled by an inverter, as a driving portion, is provided with a suction pressure detector D3 as a heat load detecting means for detecting the cooling heat load; a motor coil temperature detector D1 as a means for detecting the load condition of the motor 22; and a controller 26 that decreases the rotational speed of the motor 22 if the capacity of the compressor is determined as excessive based on a pressure signal from the detector D3, maintains the rotational speed if the capacity is determined neither excessive nor lacking.

Abstract: A screw compressor to enable prevention of contact between a slide valve and screw rotors. The screw compressor comprising a capacity controlling slide valve 3 provided for advance and (or) retreat through a piston rod 6 by a piston 5 operated by fluid pressure arranged on the discharge side to adjust the size of a diametral opening of screw rotors 1, 2 on the suction side, the screw compressor including projections 8 extending in parallel with axes of the screw rotors 1, 2 from a position distanced from the screw rotors 1, 2 at the end on the suction side of the slide valve 3, and a support portion 10 which comes in relatively slidably contact with surfaces 9 on the axial side of the screw rotors 1, 2 of the projections 8 which advance and retreat along with the slide valve 3 to support the projections 8.

Abstract: An oil-cooled type screw compressor capable of improving the oil separating efficiency is provided.

Abstract: An oil injection type screw compressor which includes an oil tank for separating lubricating oil from gas discharged from a compressor body and collecting the thus separated lubricating oil is constituted such that the oil tank has a substantially L-shaped vertical section composed of a base portion and a column portion provided uprightly on the base portion such that a spacing in the base portion located above an oil storage portion at a lower location in the base portion is formed such that it extends from an upper portion in the base portion to the inside of the column portion, and an oil separating element is provided on the inner side of an exit of gas at an upper portion of the column portion while the compressor body is disposed on the base portion.

Abstract: A screw rotor for a screw pump device includes a male rotor and a female rotor meashing with the male rotor and adapted to be driven by the male rotor, wherein a tooth profile of the female and male rotors is unsymmetrical such that the sum of absorbing torques of the female rotor is negative. Accordingly, a negative torque is always positively applied to the female rotor, thereby preventing the generation of abnormal noise and abnormal vibration due to collision of the tooth surfaces of both the rotors. As a result, a volumetric efficiency and an adiabatic efficiency can be improved.

Abstract: A screw type vacuum pump has in a passage leading to its suction port a check valve which is adapted to open the valve securely by hydraulic pressure to open the gas flow passage without the hunting phenomenon. This permits the selection of a spring with a suitable spring constant for seating the valve body on the valve seat securely and promptly to prevent reverse gas flows.

Abstract: A screw vacuum pump which includes a pair of screw rotors meshing each other with a small gap defined therebetween. A closing valve is provided in an oil circulation line leading from an oil stripper to a rotor chamber accommodating the screw rotors. A pressure switch for detecting a suction pressure is connected to the closing valve. When the suction pressure is lower than a predetermined value (i.e., at high level of vacuum), the closing valve is opened to supply the oil into the rotor chamber.

Abstract: A vertical oilless screw vacuum pump for effective use in industrial processes to which air containing oil is detrimental, such as vacuum food packaging processes and semiconductor device manufacturing processes. The vertical oilless screw vacuum pump includes a pump unit having a pump casing provided with a suction port in the upper portion and a discharge port in the lower portion thereof, and a set of meshed male and female oilless screw rotors disposed within the pump casing A, also high-frequency motor is disposed under the pump unit and has a motor casing joined to the lower end of the pump casing. The output shaft of the motor is coupled directly with one of the rotor shafts of the oilless screw rotors to drive the oilless screw rotors directly without using any gear train. Bearings supporting the upper ends of the rotor shafts are lubricated by a grease having a vapor pressure below a desired ultimate vacuum to be achieved by the vertical oilless screw vacuum pump.

Abstract: Disclosed is a screw type mechanical supercharger which is small in size but has a large capacity. The supercharger includes a pair of female and male screw rotors held in a mutully meshing condition with each other, and a pair of synchronizing gears mounted for integral rotation with the screw rotors and held in meshing engagement with each other to establish synchronous rotation of the female and male screw rotors. The female rotor has six teeth while the male rotor has three teeth, and the synchronizing gear for the female rotor has a number of teeth equal to twice that of the other synchronizing gear for the male rotor. The female rotor is connected to be driven by a reciprocating internal combustion engine so as to serve as an input power shaft of the supercharger. The screw rotors are preferably formed from a lighter weight material than the remainder of the supercharger.

Abstract: A screw supercharger is provided having a set of male and female screw rotors rotatably supported in a casing and driven through a wrapping transmission including belts and pulleys by a prime mover, wherein a through hole is formed in the wall of the causing at a position through which the input shaft of the screw rotor or the extension of the axis of the input shaft of the screw rotor extends, in that a cylindrical bearing supporting part is formed around the through hole so as to project outside from the casing, and in that a driven pulley is supported through bearings on the bearing supporting part and is fixedly mounted on the input shaft.

Abstract: Described herein is a method for operating an oil-free screw compressor and an oil-free screw compressor construction, the method including the step of feeding a gas of a temperature Ta to a discharge space in the vicinity of the discharge port of the compressor, the temperature Ta satisfying the relationshipTa.ltoreq.Tl/kwherein Ta is the temperature (.degree.K.) of said feed gas; Tl is the temperature (.degree.K.) of the compressed gas before feeding; and k is a polytropic index number.

Abstract: A screw vacuum pump which includes a pair of screw rotors meshed with each other. The vacuum pump includes an oilless screw vacuum pump suitable for application to industries where air containing foreign matter is detrimental to the products to be produced and for application to the food industry where odorous air must be avoided.

Abstract: A screw vacuum pump which includes a casing having a rotor chamber opened at its one end to a suction opening and opened at the other end to a discharge opening; a pair of male and female screw rotors rotatably received in the rotor chamber, each of the screw rotors having a pair of rotor shafts supported by forcibly lubricated bearings on both sides of the suction opening and the discharge opening; at least one first sealing member provided between the bearing on at least the suction opening side and the rotor chamber and communicated with a space under pressure less than atmospheric pressure which space is out of communication with the suction opening; and at least one second sealing member provided between the bearing on at least the suction opening side and the rotor chamber and communicated with the atmosphere, the first and second sealing members being arranged in this order from the rotor chamber side.

Abstract: A pair of dry-sealed screw rotors for compressors which includes rotor tooth profiles in which an inter-tooth gap at a profile point on male and female rotor of a normal temperature is determined by an amount of interference due to thermal expansion caused during the operation of the compressors and an amount of minimum safety clearance necessary for the operation. The inter-tooth gap is further determined by a total thickness of seal coatings applied to the peripheral surfaces of the rotors at a profile point at which the thus determined gap is smaller than the total thickness of seal coatings. With the thus shaped rotor teeth, a most preferable seal line is achieved so as to produce an improved compression efficiency.

Abstract: A screw rotor mechanism which includes a female rotor F having tooth crests each being formed by a leading side arc g2-a2 overlying a tooth tip circle Cf thereof and a following side are a2-b2 having its center at a point 07 on a pitch circle Pf thereof, and a male rotor M having tooth tips each being formed by an arc c1-d1 having its center at an interaxial line passing through axes Of,Om of the female and male rotors F,M. The male rotor M also has tooth bottoms being complementary to tooth female tooth crests or tips and forms no seal grooves thereon. The thus shaped rotors are adapted to be machined with a high efficiency by a gear hobbing machine.