Rotary expansible chamber devices – Pressure fluid radially balances working or rotating... – Counterbalancing fluid directed to rotating member shaft...
Patent
1996-04-22
1997-09-02
Vrablik, John J.
Rotary expansible chamber devices
Pressure fluid radially balances working or rotating...
Counterbalancing fluid directed to rotating member shaft...
418 91, 4182011, 418203, F04C 1816, F04C 2700, F04C 2902
Patent
active
056624638
DESCRIPTION:
BRIEF SUMMARY
This application is a Rule 371 continuation of PCT/NL 93/00150 filed Jul. 13, 1993.
The present invention relates to a rotary screw compressor comprising a casing, a male rotor and a female rotor cooperating therewith enclosed in a working space defined by the casing, the casing having a discharge outlet connected to an outlet port at the high pressure end of the working space and a suction inlet at the low pressure end of the working space, at least one rotor being rotatably supported at an end thereof through a bearing arrangement comprising a bearing bracket being fixed to an end cover and having a substantially cylindrical outer circumferential surface, the bearing bracket projecting into an axial cavity provided in the rotor forming a first chamber between the bracket and the rotor, the bracket being provided with an oil feed channel to feed oil into the first chamber.
A rotary screw compressor oft his kind for the compression of gas is known from JP-A-59-168290. During operation of a screw compressor the rotors are subjected to radial loads arising from the compression of the gas. At the high pressure end of the working space of the known compressor a cylindrical bearing bracket is provided for each rotor, each bearing bracket projecting from the end cover into an internal axial cavity provided in the high pressure end of the corresponding rotor. Pressurized oil is fed through an oil feed channel into the chamber between the bearing bracket and the rotor. The oil then leaves the chamber and enters the working space of the compressor. Finally the oil is seperated from the compressed gas and fed into the chamber again. The rotors will also be exposed to a higher pressure at their high pressure end than at their low pressure end, resulting in an axial force acting on each rotor towards the low pressure end. Therefore each rotor of the known compressor is provided with a rolling contact thrust bearing at the low pressure end.
The bearing arrangement of the known compressor has the disadvantage that it has a limited load bearing capacity, particularly in the radial direction of the rotors. Therefore the known compressor is not capable of producing a high discharge pressure or large differential pressure between the discharge outlet and suction inlet.
It is an object of the present invention to provide a rotary screw compressor according to the preamble which has an improved bearing arrangement with a high load bearing capacity in order to handle a high discharge pressure or a high differential pressure.
This has according to the invention been achieved in that at least one rotor is rotatably supported at the low pressure end thereof through the bearing arrangement, the corresponding bearing bracket being mounted at the low pressure end of the working space and the outer circumferential surface thereof being provided with at least a groove connected to the oil feed channel and a recess connected to an oil drainage channel provided in the bearing bracket, and in that sealing means are provided between the first chamber and the working space of the compressor. According to the invention an uncomplicated bearing arrangement is obtained capable of supporting high radial loads. The load bearing capacities of this bearing arrangement not only arise from the hydrostatic pressure of the pressurized oil fed into the first chamber but also from hydrodynamic load bearing effects between each stationary bearing bracket and the corresponding rotor, which will rotate at a high speed. As the pressurized oil can also be present in the space of the first chamber between the end face of a bearing bracket and the bottom of the internal cavity of the rotor axial loads on the rotor can also be supported.
In a preferred embodiment the end face at the low pressure end of a rotor, the end cover, the casing, and the corresponding bearing bracket define a second chamber, the second chamber being connected to an oil feed channel. In this manner the pressure of the oil fed into this second chamber acts as a hydrostatic thrust bearing
REFERENCES:
patent: 3796526 (1974-03-01), Cawley
patent: 3811805 (1974-05-01), Moody, Jr. et al.
patent: 4361419 (1982-11-01), Vohringer
Extract of Derwent Publications Ltd. for SU Appln. No. 88-145865, Patent No. 1,346,853.
Abaidullin Alfered I.
Galejev Ahmet M.
Ishmuratov Rustam R.
Maksimov Valeriy A.
Mirzoev Timur B.
Bednarek Michael D.
Thomassen International B.V.
Vrablik John J.
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