Rotary engines and compressors

Claim 1

IN A ROTARY COMPRESSOR OR ENGINE COMPRISING A CASING PRESENTING TWO SIDE-BY-SIDE INTERSECTIONG BORES, TWO SIDE-BY-SIDE ROTORS ROTATABLY MOUNTED IN THE RESPECTIVE BORES AND HAVING HELICAL GROOVES AND THREADS WHICH MESH AT THE INTERSECTION OF THE BORES, INLET AND OUTLET PORTS RESPECTIVELY AT OPPOSITE ENDS OF THE CASING, AND MEANS FOR DRIVING THE ROTORS SO THAT THE WORKING MEDIUM IS COMPRESSED OR EXPANDED IN WORKING CHAMBERS FORMED BETWEEN THE ROTORS AND THE CASING AND THERE IS A GRADUAL INCREASE IN TEMPERATURE FROM END TO END OF THE ROTORS AND A CORRESPONDING GRADUAL INCREASE IN THE THERMAL EXPANSION OF THE ROTORS FROM END TO END OF THE ROTORS, THE ROOT AND TIP DIAMETERS OF THE GROOVES AND THREADS OF A ROTOR GRADUALLY REDUCE FROM END TO END OF THE ROTOR TO PROVIDE TAPERED CLEARANCES BETWEEN THE ROTOR ON THE ONE HAND AND THE CASING AND SECOND ROTOR ON THE OTHER HAND, SAID CLEARANCES GRADUALLY INCREASING IN CORRESPONDENCE WITH SAID GRADUAL INCREASE IN THE THERMAL EXPANSION OF THE ROTORS TO PERMIT SAID THERMAL EXPANSION SO THAT IN OPERATION OPTIMUM WORKING CLEARANCES FOR MAXIMUM EFFICIENCY ARE PROVIDED AT ALL POINTS ALONG THE LENGTH OF THE ROTORS.