Blowers and motors with cooperating rotors

Claim 1

A MACHINE COMPRISING A MAIN HOUSING INCLUDING TWO END WALLS, A BEARING HOUSING MOUNTED EXTERNALLY DIRECTLY ON EACH OF THE END WALLS, TWO BEARINGS IN EACH BEARING HOUSING, TWO PARALLEL SHAFTS EXTENDING FROM END TO END OF THE HOUSING AND JOURNALLED AT EACH END IN ONE OF THE BEARINGS, TWO COOPERATING LOBED ROTORS, ONE ON EACH OF THE SHAFTS, FORMING SMALL BUT FINITE RUNNING CLEARANCES WITH ONE ANOTHER AND WITH THE MAIN HOUSING, TWO GEARS IN MESH, ONE ON EACH SHAFT, IMMEDIATELY EXTERNAL TO ONE OF THE BEARING HOUSINGS, MEANS LOCATING EACH BEARING HOUSING RELATIVELY TO THE ADJACENT ONE OF THE END WALLS, SAID LOCATING MEANS RESTRAINING RELATIVE MOVEMENT BETWEEN THE BEARING HOUSING AND THE END WALL IN A PLANE PERPENDICULAR TO THE SHAFT AXES AT A POINT SUBSTANTIALLY MID WAY BETWEEN THE SHAFTS AND RELATIVE ROTARY MOVEMENT BETWEEN THE BEARING HOUSING AND THE END WALL WHILE PERMITTING LOCAL RELATIVE LINEAR MOVEMENT BETWEEN THE BEARING HOUSING AND THE END WALL ELSEWHERE IN THE PLANE, CONSEQUENT ON RELATIVE DIFFERENT THERMAL EXPANSIONS OF THE END WALL AND BEARING HOUSING, THE BEARING HOUSINGS BEING OF A MATERIAL WHICH HAS A COEFFICIENT OF THERMAL EXPANSION SUBSTANTIALLY LESS THAN THAT OF THE MAIN HOUSING AND WHICH IN OPERATION EXPANDS THERMALLY TO SUBSTANTIALLY THE SAME EXTENT AS THE GEARS.