Rotary displacement pumps

Claim 1

A ROTARY DISPLACEMENT MACHINE COMPRISING A HOUSING CONTAINING AN OPERATING CHAMBER HAVING A PERIPHERAL WALL SURFACE, A HIGH-PRESSURE PORT, AND LOW-PRESSURE PORT, AT LEAST ONE DISPLACEMENT ROTOR MOUNTED IN SAID HOUSING FOR ROTATION IN SAID CHAMBER AND MADE OF A MATERIAL HAVING A LOWER COEFFICIENT OF THERMAL EXPANSION THAN SAID HOUSING, PARTITION MEANS ASSOCIATED WITH EACH ROTOR AND CO-OPERATING WITH AT LEAST PART OF SAID WALL SURFACE TO FORM MUTUALLY SEALED COMPARTMENTS WHICH DURING ROTATION OF SUCH ROTOR CONVEY LIQUID FROM ONE OF SAID PORTS TO THE OTHER, EACH ROTOR HAVING END FACES AND AT LEAST ONE JOURNAL PROJECTING FROM SUCH END FACE, SAID OPERATING CHAMBER INCLUDING AT LEAST ONE CYLINDRICAL PORTION THROUGH WHICH SUCH JOURNAL EXTENDS, A BEARING ASSEMBLY FOR EACH SUCH JOURNAL, EACH BEARING ASSEMBLY INCLUDING AN OUTER BUSH OF A MATERIAL HAVING A COEFFICIENT OF THERMAL EXPANSION WHICH IS GREATER THAN THAT OF SAID HOUSING, SAID OUTER BUSH FITTING SEALINGLY INTO SUCH CYLINDRICAL PORTION OF THE CAVITY FOR SLIDING MOVEMENT TOWARDS AND AWAY FROM SUCH ROTOR, A THIN-WALL BEARING SLEEVE OF A MATERIAL HAVING A COEFFICIENT OF THERMAL EXPANSION GREATER THAN THAT OF THE OUTER BUSH, SAID SLEEVE BEING FITTED ROUND SAID JOURNAL AND BEING ACCOMMODATED INSIDE THE OUTER BUSH, THE INSIDE DIAMETER OF SAID OUTER BUSH FROM ITS END FACING THE ROTOR THROUGHOUT AT LEAST PART OF ITS LENGTH ACCOMMODATING THE BEARING SLEEVE BEING SO MUCH GREATER THAN THE OUTSIDE DIAMETER OF THE SLEEVE AS TO LEAVE ROUND SAID SLEEVE A RADIAL GAP OF A WIDTH GREATER THAN THE RADIAL THICKNESS OF SAID SLEEVE, AND A FILLER SLEEVE OF LOW-EXPANSION MATERIAL SLIDABLY FITTING INTO THE OUTER BUSH AND OVER THE BEARING SLEEVE TO FILL THE GAP, PASSAGE MEANS BEING PROVIDED IN THE MACHINE TO CONNECT THE HIGH-PRESSURE PORT WITH A POINT OF THE OPERATING CHAMBER SEPARATED FROM THE ROTOR END FACE BY THE BEARING ASSEMBLY FOR CAUSING PRESSURE FROM SAID PORT TO URGE THE ASSEMBLY INTO SEALING CONTACT WITH SAID END FACE, THE COEFFICIENT OF THERMAL EXPANSION OF THE OUTER BUSH BEING SO CHOSEN THAT FOR ANY GIVEN TEMPERATURE DIFFERENCE THE THERMAL EXPANSION OF THE HOUSING BETWEEN THE AXIALLY FIXED POINT OF THE ROTOR AXIS AND THE CENTRE OF THE BUSH IS EQUAL TO THE SUM OF THE AXIAL EXPANSIONS OF THE INCLUDED PART OF THE AXIAL LENGTH OF THE ROTOR, AND HALF THE LENGTH OF THE BUSH, AND THE RADIAL THICKNESS OF THE GAP BETWEEN THE SLEEVE AND THE BUSH BEING SUCH THAT THE TOTAL AMOUNT OF THERMAL EXPANSION PER UNIT OF TEMPERATURE OF THE BEARING ASSEMBLY IS EQUAL TO THAT OF THE ROTOR.