Air cushion vehicles having flexible skirts deflectable by subsidiary cushion pressure

Claim 1

A VEHICLE FOR TRAVELLING OVER A SURFACE AND WHICH, IN OPERATION, IS SUPPORTED ABOVE THAT SURFACE BY AT LEAST ONE CUSHION OF PRESSURISED GAS FORMED AND CONTAINED IN A SPACE BENEATH THE VEHICLE BODY, COMPRISING A WALL STRUCTURE CAPABLE OF VERTICAL DEFLECTION FOR CONTAINING SAID CUSHION FOR AT LEAST PART OF ITS PERIPHERY, SAID STRUCTURE INCLUDING A FLEXIBLE MEMBER DEPENDING FROM AND HAVING ITS UPPER EDGE CONNECTED TO THE LOWER PART OF THE VEHICLE BODY AND ITS LOWER EDGE FREE TO MOVE VERTICALLY RELATIVE TO SAID BODY, SAID MEMBER HAVING A PROFILE IN A VERTICAL PLANE NORMAL TO THE CUSHION PERIPHERY WHICH EXTENDS IN A CURVE DOWNWARDLY BENEATH THE VEHICLE AND PROVIDES A CONVEX SURFACE ON SAID MEMBER AT LEAST THE LOWER PART OF WHICH FACES TOWARD THE SUBJACENT SURFACE OVER WHICH THE VEHICLE IS OPERATING, AND MEANS FOR SO DISCHARGING FLUID FROM THE LOWER PART OF THE VEHICLE BODY ADJACENT THE UPPER EDGE OF SAID MEMBER THAT SAID FLUID FLOWS DOWN IN CONTACT WITH SAID CONVEX SURFACE TO THE LOWER EDGE OF SAID MEMBER IN A SUBSTANTIALLY COHERENT STREAM BY THE COANDA EFFECT, THE LOWER EDGE OF SAID MEMBER FORMING A DISCONTINUITY IN THE PROFILE THEREOF BEYOND WHICH THE COANDA EFFECT CEASES AND THE FLUID LEAVES THE CONVEX SURFACE IN A DIRECTION SUBSTANTIALLY TANGENTIAL THERETO WHEN THE VEHICLE IS OPERATING WITH A NORMAL CLEARANCE BETWEEN THE LOWER PART OF SAID CONVEX SURFACE AND THE SUBJACENT SURFACE, WHEREBY WHEN SAID CLEARANCE DECREASES A REGION OF INCREASED FLUID PRESSURE IS FORMED BETWEEN THE LOWER PART OF SAID CONVEX SURFACE AND SAID SUBJACENT SURFACE WHICH IS EFFECTIVE TO CAUSE A PORTION OF SAID FLUID FLOW TO BECOME DETACHED FROM SAID CONVEX SURFACE ABOVE THE LOWER EDGE OF SAID MEMBER AND TO FORM A FLUID CURTAIN WHICH FLOWS DOWNWARDLY TOWARD SAID SUBJACENT SURFACE, SAID CURTAIN COMBINING WITH SAID MEMBER AND SAID SUBJACENT SURFACE TO ENCLOSE A SUBSIDIARY CUSHION SPACE WHEREIN SUFFICIENT PRESSURE IS BUILT UP TO RAISE THE LOWER PART OF SAID MEMBER AND MAINTAIN IT OUT OF CONTACT WITH SAID SUBJACENT SURFACE.