Rotary piston pump

Claim 1

A ROTARY PISTON PUMP COMPRISING, IN COMBINATION A HOUSING HAVING A CAVITY AND A SURFACE FORMED WITH AN ANNULAR RECESS COMMUNICATING WITH SAID CAVITY, SAID HOUSING HAVING INLET MEANS AND OUTLET MEANS COMMUNICATING WITH SPACED PORTIONS OF SAID RECESS; A FIRST ROTOR MOUNTED IN SAID HOUSING FOR TURNING MOVEMENT ABOUT A FIRST AXIS AND HAVING A PLURALITY OF PISTONS PROJECTING IN AXIAL DIRECTION INTO SAID ANNULAR RECESS TO TRANSPORT A FLUID FROM SAID INLET MEANS TO SAID OUTLET MEANS; A SECOND LOCK ROTOR MOUNTED IN SAID ANNUALR RECESS FOR FREE TURNING MOVEMENT ABOUT A SECOND AXIS AND HAVING CIRCUMFERENTIALLY SPACED OPENINGS INTO WHICH SOME OF SAID PISTONS PROJECT, SAID LOCK ROTOR BEING ROTATED BY SAID PISTONS OF SAID FIRST ROTOR AND FLUID-TIGHTLY SEPARATING SAID INLET MEANS AND SAID OUTLET MEANS; AND A PLATE LOCATED IN SAID CAVITY AND HAVING AT ONE SIDE A FACE SLIDABLY ENGAGING SAID SURFACE AND COVERING SAID ANNULAR RECESS, SAID PLATE HAVING CIRCUMFERENTIALLY SPACED OPENINGS THROUGH WHICH SAID PISTONS PROJECT TOWARD SAID ANNULAR RECESS AND BEING MOUNTED FOR ROTATION ABOUT SAID FIRST AXIS SO THAT SAID PLATE ROTATES WITH SAID PISTONS OF SAID FIRST ROTOR, SAID PLATE BEING MOUNTED ALSO FOR AXIAL MOVEMENT SO THAT SAID FACE AND SAID SURFACE FORM A VARIABLE GAP THROUGH WHICH PRESSURE FLUID PASSES FROM SAID ANNULAR RECESS INTO A SAID CAVITY SO THAT THE PRESSURE IN SAID CAVITY ACTS ON THE OTHER SIDE OF SAID PLATE TO URGE THE SAME TOWARD SAID SURFACE TO CLOSE SAID ANNULAR RECESS UNTIL A CONDITION OF EQUILIBRIUM IS REACHED WHEREBY NO AXIAL PRESSURE IS EXERTED ON SAID FIRST ROTOR.