Helically threaded rotors for screw type pumps, compressors and similar devices

Claim 1

IN A FLUID DISPLACEMENT DEVICE OF THE TYPE HAVING A HOUSING PROVIDED WITH INTERSECTING CYLINDRICAL ROTOR CHAMBERS AND SUCTION AND DISCHARGE PORTS ARRANGED DIAGONALLY OPPOSITE EACH OTHER ADJACENT TO THE OPPOSITE ENDS OF THE HOU SING, AND A PAIR OF COMPLEMENTARY MATING HELICALLY THREADED ROTORS SYMMETRICAL IN CROSS SECTION THROUGHOUT THEIR LENGTH CONSISTING OF A MAIN ROTOR AND A GATE ROTOR EACH HAVING A PLURALITY OF THREADS AND TROUGHS, SAID ROTORS BEING ROTATABLY SUPPORTED WITHIN THE CHAMBERS OF SAID HOUSING AND COOPERATING WITH EACH OTHER AND SAID HOUSING TO FORM POCKETS AT THE SUCTION PORT, TO ADVANCE SAID POCKETS AND THE FLUID THEREIN AXIALLY ALONG THE ROTORS AND TO EXHAUST THE FLUID AT THE DISCHARGE END OF THE ROTORS THROUGH THE DISCHARGE PORTS AS THE ROTORS REVOLVE IN OPPOSITE DIRECTIONS ABOUT THE AXES THEREOF, THE ROTORS BEING HELD IN TIMED RELATION BY TIMING GEARS AND THE THREADS OF EACH ROTOR COOPERATING WITH THE TROUGHS OF THE MATING ROTOR AND WITH SAID HOUSING CHAMBER WALLS TO PROVIDE FIXED CLOSE RUNNING CLEARANCES WHICH EFFECTIVELY SEAL SAID POCKETS AGAINST LEAKAGE AS THE ROTORS ARE ROTATED TO ADVANCE THE POCKETS THEREALONG, THE IMPROVEMENT WHICH COMPRISES: EACH OF SAID ROTORS HAVING A UNIFORM ECTION AND A NON-UNIFORM SECTION, THE UNIFORM SECTIONS EXTENDING FROM THE SUCTION END OF THE ROTORS TO A POINT INTERMEDIATE THE ENDS OF SAID ROTORS AND THE NON-UNIFORM SECTIONS EXTENDING FROM THE DISCHARGE END OF THE ROTORS TO THE UNIFORM SECTION; THE MAIN ROTOR CHARACTERIZED BY HAVING UNIFORM CYLINDRICAL LANDS THROUGHOUT ITS LENGTH AT THE ROOT OF THE THREADS AND UNIFORM CYLINDRICAL LANDS THROUGHOUT THE UNIFORM SECTION AT THE TIPS OF THE THREADS, THE SIDES OF THE THREADS THROUGHOUT THEIR LENGTH BEING GENERATED BY THE CREST EDGES OF THE GATE ROTOR, THE TIPS OF THE THREADS IN THE NON-UNIFORM SECTION BEING CUT AWAY IN A GENERALLY TAPERED MANNER TO FORM INCLINED LANDS, SAID INCLINED LANDS BEGINNING AT THE TIPS OF THE THREADS AT THE JUNCTION BETWEEN SAID UNIFORM AND NONUNIFORM SECTIONS AND TERMINATING AT THE DISCHARGE END OF THE ROTOR, THE LENGTH OF THE INCLINED LANDS BEING LESS THAN THE NORMAL AXIAL DIMENSION OF THE DISCHARGE PORT AND THE HEIGHT OF THE THREADS BEING REDUCED BY SUBSTANTIALLY ONE-HALF AT THE DISCHARGE END OF THE ROTOR, THE SHARP EDGES FORMED BY THE INTERSECTIONS BETWEEN THE INCLINED LANDS AND THE SIDES OF THE THREADS BEING ROUNDED TO FORM GENERATING ARCS, SAID ARCS BEING SUBSTANTIALLY TANGENTIAL TO THE INCLINED LANDS AND THE SIDES OF THE THREADS, SAID INCLINED LANDS BEING WIDEST AT THE DISCHARGE END OF THE ROTOR TO FORM UNBROKEN SEAL LINES WITH THE GATE ROTOR AS THE ROTORS REVOLVE IN TIMED RELATION; AND THE GATE ROTOR BEING CHARACTERIZED BY HAVING INCLINED LANDS AT THE ROOT OF THE TROUGHS IN THE NON-UNIFORM SECTION OF SAID ROTOR COMPLEMENTARY TO THE INCLINED LANDS OF SAID MAIN ROTOR AND GENERATING SURFACES IN SAID TROUGHS.