Shut-off valve for cementitious pressure vessels

Claim 1

IN A MACHINE FOR HANDLING PARTICULATE MATERIAL, THE COMBINATION OF A PRESSURE HOPPER FOR SAID MATERIAL HAVING A MATERIAL INLET PORT AND A CIRCULAR, RESILIENT SEAT IN THE HOPPER ADJACENT THE PORT; A VALVE IN THE HOPPER HAVING A CONVEX OUTER FACE SHAPED SUBSTANTIALLY IN CONFORMITY WITH A SECTOR OF A SPHERE, SAID OUTER FACE NORMALLY BEARING AGAINST THE SEAT IN CLOSING RELATIONSHIP TO THE PORT; AND RESILIENT SUPPORT MEANS COUPLED WITH THE VALVE AND INCLUDING A SHAFT ROTATABLY CARRIED BY THE HOPPER AND SUPPORTING THE VALVE FOR MOVEMENT TO SAND FROM A POSITION OPENING SAID PORT AS SAID SHAFT IS ROTATED, SAID SUPPORT MEANS FLEXING IN RESPONSE TO PRESSURE IN THE HOPPER AND MOUNTING THE VALVE FOR MOVEMENT TOWARD THE SEAT TO COMPRESS THE LATTER WHEN THE VALVE IS CLOSED, WHEREBY SAID PRESSURE IN THE HOPPER HOLDS THE VALVE TIGHTLY AGAINST SAID SEAT, THE SUPPORT MEANS RETURNING THE VALVE TO A DISPOSITION OUT OF SUBSTANTIAL COMPRESSING ENGAGEMENT WITH THE SEAT IN THE ABSENCE OF SAID PRESSURE, WHEREBY TO MINIMIZE DRAG OR FRICTION BETWEEN THE SEAT AND THE VALVE DURING MOVEMENT OF THE LATTER TO THE OPEN POSITION WHEN THE HOPPER IS DEPRESSURIZED.