Dry band francis turbines

Claim 1

IN A FRANCIS TURBINE, A STATIC STRUCTURE HAVING A SMOOTHLY CONTINUOUS SURFACE PORTION, A DRAFT TUBE, A RUNNER HAVING A BAND SHROUD WITH UPPER AND LOWER EDGES ADJACENT TO SAID DISC STRUCTURE BUT SPACED THEREFROM TO PROVIDE RUNNING CLEARANCES AT SAID UPPER AND LOWER EDGES, SAID SMOOTHLY CONTINUOUS SURFACE PORTION AND SAID BAND DEFINING AND ANNULAR SPACE BETWEEN SAID SHROUD AND SAID STATIC STRUCTURE COMMUNICATING WITH SAID CLEARANCES BETWEEN THE SHROUD AND THE STATIC STRUCTURE AT BOTH THE UPPER AND LOWER EDGES OF SAID SHROUD, AIR SUPPLY MEANS THROUGH SAID STATIC STRUCTURE FOR SUPPLYING AIR TO SAID ANNULAR SPACE, A DISTRIBUTOR RING SUPPLYING WATER UNDER PRESSURE TO THE RUNNER, SAID DISTRIBUTOR RING SPACED FROM SAID UPPER EDGE OF SAID SHROUD AND PROVIDED WITH A SEALING FACE, A SEALING FACE AROUND THE UPPER PORTION OF SAID BAND SHROUD FOR COOPERATING WITH SAID SEALING FACE ON THE DISTRIBUTOR RING SO AS TO RESTRICT THE FLOW OF LEAKAGE WATER INTO SAID ANNULAR SPACE THROUGH THE CLEARANCE BETWEEN THE STATIC STRUCTURE AND THE UPPER EDGE OF THE SHROUD, A BAULK RING FIXED TO SAID STATIC STRUCTURE IN SAID ANNULAR SPACE ADJACENT TO THE LOWER EDGE OF SAID SHROUD BUT SPACED THEREFROM TO PROVIDE A RUNNING CLEARANCE THEREBETWEEN, SAID BAULK RING BEING SUPPORTED IN SPACED RELATIONSHIP FROM SAID STATIC STRUCTURE SO THAT AN ANNULAR PASSAGE IS PROVIDED BETWEEN THE STATIC STRUCTURE AND THE BAULK RING, SAID SHROUD ON ROTATION FORMING A ROTATING RING OF WATER ADJACENT TO SAID SMOOTH SURFACE OF THE STATIC STRUCTURE TO PERMIT THE ESCAPE OF LEAKAGE WATER ONLY FROM THE ANNULAR SPACE AROUND THE BAULK RING AND THROUGH THE CLEARANCE BETWEEN THE STATIC STRUCTURE AND THE LOWER EDGE OF THE SHROUD INTO THE DRAFT TUBE.