Fluid pressure responsive rubber seated butterfly valve

Claim 1

A BUTTERFLY VALVE COMPRISING A VALVE BODY HAVING A PASSAGEWAY FOR FLUID FLOW THERETHROUGH, VANE MEANS SUPPORTED IN THE VALVE PASSAGEWAY FOR MOTION BETWEEN AN OPEN POSITION AND A CLOSED POSITION AND HAVING A PERIPHERAL SURFACE, RESILIENT SEALING MEANS MOUNTED IN THE VALVE BODY HAVING A VANE-ENGAGING SURFACE PORTION TO ENGAGE THE PERIPHERY SURFACE OF THE VANE MEANS WITH A MINIMUM INITIAL CONTACT PRESSURE, AND SEAL CONFINING MEANS FORMING, IN CONJUNCTION WITH THE VALVE BODY AND THE VANE MEANS IN THE CLOSED POSITION OF THE VANE, AND SUBSTANTIALLY COMPLETE ENCLOSURE FOR THE RESILIENT SEALING MEANS, THE SEAL CONFINING MEANS PROVIDING AN ANNULUS PERMITTING THE SEALING MEANS VANE-ENGAGING SURFACE PORTION TO BE EXPOSED TO THE PERIPHERY OF THE VANE MEANS, THE ANNULUS HAVING A WIDTH SUBSTANTIALLY EQUAL TO THE THICKNESS OF THE VANE MEANS AT THE PERIPHERAL SURFACE THEREOF, WHEREBY INCREASED PRESSURE APPLIED TO A PORTION OF THE SEALING MEANS IS TRANSMITTED TO THE VANE-ENGAGING SURFACE PORTION SO AS TO INCREASE THE CONTACT PRESSURE WITH THE PERIPHERY OF THE VANE MEANS BUT, AT THE SAME TIME, DISTORTION OF THE RESILIENT SEALING MEANS IS EFFECTIVELY PREVENTED.