Mainrotor machining process and apparatus

A method of making a globoidal screw for use as a mainrotor in a compressor or expander comprising the steps of:

• a) providing a cylindrical rotor body having a longitudinal axis and mounting said rotor body for rotation about said longitudinal axis;
• b) providing a cutter having at least one tooth along a circumference disposed in a plane and having an axis of rotation disposed perpendicular to said plane;
• c) mounting said cutter for rotation about said axis and with said cutter disposed so that the plane thereof is parallel to said rotor body longitudinal axis and that the rotational axis thereof is perpendicular to said rotor longitudinal axis;
• d) rotating said rotor body and said cutter at synchronized speeds;
• e) positioning said rotor body and said cutter relative to each other in a manner moving said cutter axis of rotation and said rotor body longitudinal axis relative to each other to decrease the distance between said axis while said rotor body and cutter are being rotated so that said cutter tooth contacts said rotor body during each cutter rotation to remove material from said rotor body by a milling action to form a globoid screw profile including a groove having a pair of spaced-apart sidewalls and extending along said rotor body in a helical path;
• and
• f) changing the relative speed between said rotor body and said cutter by a given amount for a given time to effect a positional change between said cutter tooth and the material of said rotor body thereby resulting in a desired change in the globoid screw profile, the relative speed being increased or decreased depending upon which groove sidewall is being machined and the speed change being to an extent depending upon the desired groove sidewall location.

Apparatus for machining a globoid screw from a cylindrical rotor body having a longitudinal axis for uses as a mainrotor in a compressor or expander, said apparatus comprising:

• a) means for mounting said cylindrical rotor body for rotation about said longitudinal axis thereof;
• b) a cutter having a plurality of teeth at spaced locations around a circumference disposed in a plane and having an axis of rotation disposed perpendicular to said plane;
• c) means for mounting said cutter for rotation about said axis and with said cutter disposed so that the plane thereof is parallel to said rotor body longitudinal axis and so that the rotational axis thereof is perpendicular to said rotor body longitudinal axis;
• d) drive means operatively associated with said rotor body and said cutter for rotating said rotor body and said cutter at synchronized speeds;
• and
• e) means for moving said cutter and said rotor body relative to each other so that said cutter axis of rotation and said rotor body longitudinal axis are moved relative to each other while said cutter and said rotor body are rotated so that said cutter teeth contact said rotor body during rotation of said cutter to remove material from said body by a milling action to form a globoid screw profile.

Apparatus for machining a globoid screw from a cylindrical rotor body having a longitudinal axis for uses as a mainrotor in a compressor, said apparatus comprising:

• a) means for mounting said cylindrical rotor body for rotation about said longitudinal axis thereof;
• b) a cutter having at least one tooth along a circumference disposed in a plane and having an axis of rotation disposed perpendicular to said plane;
• c) means for mounting said cutter for rotation about said axis and with said cutter disposed so that the plane thereof is parallel to said rotor body longitudinal axis and so that the rotational axis thereof is perpendicular to said rotor body longitudinal axis;
• d) drive means operatively associated with said rotor body and said cutter for rotating said rotor body and said cutter at synchronized speeds;
• and
• e) means for moving said cutter and said rotor body relative to each other so that said cutter axis of rotation and said rotor body longitudinal axis are moved relative to each other while said cutter and said rotor body are rotated so that said cutter tooth contacts said rotor body during each rotation of said cutter to remove material from said body by a milling action to form a globoid screw profile including a groove having a pair of spaced-apart sidewalls and extending along said rotor body in a helical path;
• and
• f) means operatively associated with said drive means for changing the relative speed between said rotor body and said cutter by a given amount for a given time to effect a positional change between said cutter tooth and the material of said rotor body thereby resulting in a desired change in the globoid screw profile, the relative speed being increased or decreased depending upon which groove sidewall is being machined and the speed change being to an extent depending upon the desired groove sidewall location.