Rotary screw compressor and method for providing thrust bearing force compensation

A rotary screw compressor comprising:

• a rotor housing including a bore means, a bearing means, a low pressure end having a low pressure inlet and a high pressure end having a high pressure outlet;
• rotor means rotatably mounted by said bearing means in said bore means, and having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• a compression chamber means on said rotor means which successively progressively diminishes in volume during operation to provide a low pressure corresponding to said low pressure at said inlet, a high pressure corresponding to said high pressure at said outlet and a series of intermediate pressures between said high and low pressures throughout a range of the compressor outputs;
• a pressure applying means for exerting a counterbalancing force on said rotor means in opposition to said variable axial thrust force existing on said rotor means end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with said compression chamber means at one of said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to supply said one of said series of intermediate pressures to said pressure applying means and cause application of a variable counterbalancing force on said rotor means which varies through said output range of the compressor,
• wherein said intermediate pressure port means includes a plurality of intermediate pressure ports connectable in equalized pressure communication with said compressor chamber means at different intermediate pressure levels within said series of intermediate pressures, and wherein a selector means is provided for connecting only one of said intermediate pressure ports with said conduit means.

A rotary screw compressor comprising:

• a rotor housing including a bore means, a bearing means, a low pressure end having a low pressure inlet and a high pressure end having a high pressure outlet;
• rotor means rotatably mounted by said bearing means in said bore means, and having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• a compression chamber means on said rotor means which successively progressively diminishes in volume during operation to provide a low pressure corresponding to said low pressure at said inlet, a high pressure corresponding to said high pressure at said outlet and a series of intermediate pressures between said high and low pressures throughout a range of the compressor outputs;
• a pressure applying means for exerting a counterbalancing force on said rotor means in opposition to said variable axial thrust force existing on said rotor means end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with said compression chamber means at one of said series of intermediate pressures;
• and
• a conduit mean sin equalized pressure communication between said pressure applying means and said intermediate pressure port means to supply said one of said series of intermediate pressures to said pressure applying means and cause application of a variable counterbalancing force on said rotor means which varies through said output range of the compressor,
• wherein said intermediate pressure port means comprises a movable selector means, a single port on said movable selector means, and an actuating means for moving said selector means to vary the specific location of said intermediate pressure port to select one of the intermediate pressures within said series of intermediate pressures.

A rotary screw compressor comprising:

• a rotor housing having intersecting bores, a bearing means, a low pressure end having a low pressure inlet and a high pressure end having a high pressure outlet;
• male and female rotors rotatably mounted by said bearing means on parallel axes in said bores, and each having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• helical grooves and lands on said rotors intermeshed to define a plurality of compression chambers which successively progressively diminish in volume during operation to provide compression chambers that have a low pressure corresponding to said low pressure at said inlet, a high pressure corresponding to said high pressure at outlet and a series of intermediate pressures between said high and low pressures throughout a range of the compressor outputs;
• a pressure applying means for exerting a counterbalancing force on at least one of said rotors in opposition to said axial thrust force existing on said rotor end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with one of said compression chambers that is at a pressure falling within said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to cause said pressure applying means to apply a counterbalancing force on said rotor which varies as a function of suction pressure to maintain a required axial bearing load on said bearing means throughout said output range of the compressor.

A rotary screw compressor comprising:

• a rotor housing having intersecting bores, a bearing means, a low pressure end having a low pressure inlet and a high pressure end having a high pressure outlet;
• male and female rotors rotatably mounted by said bearing means on parallel axes in said bores, and each having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• helical grooves and lands on said rotors intermeshed to define a plurality of compression chambers which successively progressively diminish in volume during operation to provide compression chambers that have a low pressure corresponding to said low pressure at said inlet, a high pressure corresponding to said high pressure at outlet and a series of intermediate pressures between said high and low pressures throughout a range of the compressor outputs;
• a pressure applying means for exerting a counterbalancing force on at least one of said rotors in opposition to said axial thrust force existing on said rotor end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with one of said compression chambers that is at a pressure falling within said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to cause said pressure applying means to apply a counterbalancing force on said rotor which varies as a function of suction pressure to maintain a required axial bearing load on said bearing means throughout said output range of the compressor;
• wherein said intermediate pressure port means comprises a plurality of intermediate pressure ports in said rotor housing each opening into equalized pressure communication with one of said compression chambers that is at a pressure falling within said series of intermediate pressures and wherein a selector means is provided to select only one of said intermediate pressure ports for connection to said conduit means during operation of said compressor.

A method for operating a rotary screw compressor of the type including a rotor housing having a bore means, a bearing means, a low pressure inlet end, and a high pressure outlet end;

• a rotor means rotatably mounted in said bore means by said bearing means and having a plurality of compression chamber means which successively progressively diminishes in volume to provide a low pressure corresponding to the pressure at said inlet end, a high pressure corresponding to the pressure at said outlet end and a series of intermediate pressures between said low and high pressures, and a high pressure end face subject to said high pressure at said outlet end which exerts a variable axial thrust force on said rotor means corresponding to compressor output;
• and a pressure applying means connected to said rotor means to exert a counterbalancing force on said rotor means comprising the steps of:
• establishing an intermediate pressure port means opening into said compression chamber means at one of said series of intermediate pressures;
• rotating said rotor means to operate said compressor in an output range and create a source of said series of intermediate pressures;
• and
• connecting said intermediate pressure port means in equalized pressure communication with said pressure applying means to allow said one of said series of intermediate pressures to appear at said pressure applying means and exert a varying counterbalancing force on said rotors which will parallel the load curve of the compressor from minimum to maximum operating capacity to always provide a required axial load on said bearing means.

A method for operating a rotary screw compressor of the type including a rotor housing having a bore means, a bearing means, a low pressure inlet end, and a high pressure outlet end;

• a rotor means rotatably mounted in said bore means by said bearing means and having a plurality of compression chamber means which successively progressively diminishes in volume to provide a low pressure corresponding to the pressure at said inlet end, a high pressure corresponding to the pressure at said outlet end and a series of intermediate pressures between said low and high pressures, and a high pressure end face subject to said high pressure at said outlet end which exerts a variable axial thrust force on said rotor means corresponding to compressor output;
• and a pressure applying means connected to said rotor means to exert a counterbalancing force on said rotor means comprising the steps of:
• establishing an intermediate pressure port means opening into said compression chamber means at one of said series of intermediate pressures;
• rotating said rotor means to operate said compressor in an output range and create a source of said series of intermediate pressures;
• and
• connecting said intermediate pressure port means in equalized pressure communication with said pressure applying means to allow said one of said series of intermediate pressures to appear at said pressure applying means and exert a varying counterbalancing force on said rotors which will parallel the load curve of the compressor rom minimum to maximum operating capacity to always provide a required axial load on said bearing means;
• establishing a plurality of intermediate pressure ports into said intermediate pressure means at locations therein that will result in a different one of said intermediate pressures appearing at each port;
• connecting any selected one of said plurality of intermediate pressure ports in equalized pressure communication with said pressure applying means;
• and
• preventing intermediate pressure flow from the remaining intermediate pressure ports.

A method for operating a rotary screw compressor of the type including a rotor housing having a bore means, a bearing means, a low pressure inlet end, and a high pressure outlet end;

• a rotor means rotatably mounted in said bore means by said bearing means and having a plurality of compression chamber means which successively progressively diminishes in volume to provide a low pressure corresponding to the pressure at said inlet end, a high pressure corresponding to the pressure at said outlet end and a series of intermediate pressures between said low and high pressures, and a high pressure end face subject to said high pressure at said outlet end which exerts a variable axial thrust force on said rotor means corresponding to compressor output;
• and a pressure applying means connected to said rotor means to exert a counterbalancing force on said rotor means comprising the steps of:
• establishing an intermediate pressure port means opening into said compression chamber means at one of said series of intermediate pressures;
• rotating said rotor means to operate said compressor in an output range and create a source of said series of intermediate pressures;
• and
• connecting said intermediate pressure port means in equalized pressure communication with said pressure applying means to allow said one of said series of intermediate pressures to appear at said pressure applying means and exert a varying counterbalancing force on said rotors which will parallel the load curve of the compressor from minimum to maximum operating capacity to always provide a required axial load on said bearing means;
• establishing said intermediate pressure port means on a movable member that is movable to vary the location of said intermediate pressure port means;
• and
• moving said movable member to place said intermediate pressure port means in equalized pressure communication with a selected one of said varying pressures within said intermediate pressure range.

A rotary screw compressor comprising:

• a rotor housing including a bore means, a bearing means, a low pressure end having a low pressure inlet, a high pressure end having a high pressure outlet, and a slide valve recess providing a fluid bypass between said bore means and said inlet;
• rotor means rotatably mounted by said bearing means in said bore means, and having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• a compression chamber means on said rotor means which successively progressively diminishes in volume during operation to provide a low pressure and a high pressure throughout a range of compressor outputs, and which is capable of providing a series of intermediate pressures capable of progressively increasing between said high and low pressures;
• a slide valve means mounted in said slide valve recess operative to control compressor capacity and compression volume ratio through said compressor output range;
• a pressure applying means for exerting a counterbalancing force on said rotor means in opposition to said variable axial thrust force existing on said rotor means end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with said compression chamber means at one of said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to supply said one of said series of intermediate pressures to said pressure applying means and cause application of a counterbalancing force on said rotor means which varies through said compressor output range to always maintain a required axial load on said bearing means.

A rotary screw compressor comprising:

• a rotor housing including a bore means, a bearing means, a low pressure end having a low pressure inlet, a high pressure end having a high pressure outlet, and a slide valve recess providing a fluid bypass between said bore means and said inlet;
• rotor means rotatably mounted by said bearing means in said bore means, and having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end;
• a compression chamber means on said rotor means which successively progressively diminishes in volume during operation to provide a low pressure and a high pressure throughout a range of compressor outputs, and which is capable of providing a series of intermediate pressure capable of progressively increasing between said high and low pressures;
• a slide valve means mounted in said slide valve recess operative to control compressor capacity and compression volume ratio through said compressor output range;
• a pressure applying means for exerting a counterbalancing force on said rotor means in opposition to said variable axial thrust force existing on said rotor means end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with said compression chamber means at one of said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to supply said one of said series of intermediate pressures to said pressure applying means and cause application of a counterbalancing force on said rotor means which varies through said compressor output range to always maintain a required axial load on said bearing means;
• wherein said intermediate pressure port means includes a plurality of intermediate pressure ports connectable in equalized pressure communication with said compressor chamber means at different intermediate pressure levels within said series of intermediate pressures, and wherein a selector means is provided for connecting only one of said intermediate pressure ports with said conduit means.

A rotary screw compressor comprising;

• a rotor housing including a bore means, a bearing means, a low pressure end having a low pressure inlet, a high pressure end having a high pressure outlet, and a slide valve recess providing a fluid bypass between said bore means and said inlet;
• rotor means rotatably mounted by said bearing means in said bore means, and having a high pressure end face subject to a variable axial thrust force induced by high pressure at aid high pressure end;
• a compression chamber means on said rotor means which successively progressively diminishes in volume during operation to provide a low pressure and a high pressure throughout a range of compressor outputs, and which is capable of providing a series of intermediate pressure capable of progressively increasing between said high and low pressures;
• a slide valve means mounted in said slide valve recess operative to control compressor capacity and compression volume ratio through said compressor output range;
• a pressure applying means for exerting a counterbalancing force on said rotor means in opposition to said variable axial thrust force existing on said rotor means end face at said high pressure end during operation;
• an intermediate pressure port means in equalized pressure communication with said compression chamber means at one of said series of intermediate pressures;
• and
• a conduit means in equalized pressure communication between said pressure applying means and said intermediate pressure port means to supply said one of said series of intermediate pressures to said pressure applying means and cause application of a counterbalancing force on said rotor mean which varies through said compressor output range to always maintain a required axial load on said bearing means;
• wherein said intermediate pressure port means comprises a movable selector means, a single port on said movable selector means, and an actuating means for moving said selector means to vary the specific location of said intermediate pressure port to select one of the intermediate pressures within said series of intermediate pressures.

A rotary screw compressor comprising:

• a rotor housing including a bore, a low pressure end having a low pressure inlet, and a high pressure end having a high pressure outlet;
• a rotor rotatably mounted in said bore and having a high pressure end face subject to a variable axial thrust force induced by high pressure at said high pressure end, said rotor defining first and second pressure chambers presenting a low pressure corresponding to said low pressure at said inlet and a high pressure corresponding to said high pressure at said outlet, respectively, said rotor further defining a third pressure chamber which is positioned between said first and second pressure chambers and which is capable of presenting an intermediate pressure between said high and low pressures;
• a pressure applying device capable of exerting a counterbalancing force on said rotor in opposition to said variable axial thrust force existing on said rotor end face at said high pressure end during operation;
• an intermediate pressure port in equalized pressure communication with said third compression chamber;
• and
• a conduit in equalized pressure communication between said pressure applying device and said intermediate pressure port so as to be capable of supplying said intermediate pressure to said pressure applying device and of causing application of a variable counterbalancing force on said rotor.