Vehicles for travelling over a surface

Claim 1

A VEHICLE FOR TREVELLING OVER A SURFACE OF THE TYPE WHICH IS SUPPORTED ABOVE THE SURFACE BY AT LEAST ONE CUSHION OF PRESSURISED GAS FORMED AND CONTAINED IN A SPACE BENEATH THE VEHICLE, INCLUDING A FLEXIBLE SKIRT ATTACHED TO THE LOWER PART OF THE VEHICLE CONTAINING THE CUSHION FOR AT LEAST PART OF ITS PERIPHERY, SAID SKIRT COMPRISING AT LEAST ONE INFLATABLE, GAS-RETAINING THIN WALLED FLEXIBLE MEMBER HAVING FIRST AND SECOND EDGES, THE CROSSSECTIONAL SHAPE OF SAID MEMBER NORMAL TO THE PERIPHERY OF THE CUSHION SPACE BEING A SUBSTANTIALLY CONTINUOUS CURVE EXTENDING FROM SAID FIRST EDGE INITIALL IN A DIRECTION OUTWARDLY AWAY FROM THE CUSHION SPACE, THEREAFTER EXTENDING DOWNWARDLY AND THEN INWARDLY AND THEN UPWARDLY, ENDING IN SAID SECOND EDGE, SO AS TO PRESENT ON ITS LOWER SURFACE A CONTINUOUS CONVEX FACE WHICH IS PRESENTED, TOWARDS THE SURFACE OVER WHICH THE VEHICLE IS SUPPORTED, THE FIRST EDGE OF SAID FLEXIBLE MEMBER BEING ATTACHED TO THE BOTTOM SURFACE OF THE VEHICLE AND THE SECOND EDGE THEREOF LYING BELOW AND BEING MOVABLE RELATIVE TO SAID BOTTOM SURFACE, AND FLEXIBLE MEANS CONNECTING THE SECOND EDGE OF SAID FLEXIBLE MEMBER TO THE BOTOM SURFACE OF THE VEHICLE AT A POSITION INWARDS TOWARDS THE CENTRE OF THE CUSHION SPACE RELATIVE TO THE POSITION OF SAID SECOND EDGE, MEANS FOR SUPPLYING GAS DIRECTLY TO THE CUSHION SPACE WITHOUT PASSING THROUGH THE SPACE WITHIN SAID FLEXIBLE MEMBER, SAID FLEXIBLE MEMBER BEING NORMALLY INFLATED TO A PRESSURE SUBSTANTIALLY EQUAL TO THE CUSHION PRESSURE AND BEING FREE OF INTERNAL RESTRAINT, WHEREBY, UNDER THE ACTION OF THE INFLATION PRESSURE WITHIN SAID MEMBER AND THE FLOW OF GAS OUTWARDLY FROM THE CUSHION SPACE BENEATH THE CONVEX LOWER SURFACE OF SAID MEMBER, SAID MEMBER ASSUMES A PROFILE HAVING A PRESSURE DISTRIBUTION TENDING TO MAINTAIN SAID LOWER SURFACE CLEAR TO THE SURFACE OVER WHICH THE VEHICLE IS SUPPORTED, SAID FLEXIBLE MEMBER BEING FREE TO DEFLECT BOTH UPWARDLY AND DOWNWARDLY FROM A NORMAL POSITION AND TO CHANGE IN SHAPE UPON VARIATIONS IN THE DISTANCE BETWEEN THE BOTTOM SURFACE OF THE VEHICLE AND THE SURFACE OVER WHICH THE VEHICLE IS SUPPORTED, AN UPWARDLY DEFLECTIONS OF ANY PORTION OF SAID FLEXIBLE MEMBER ALSO CAUSING AN OUTWARD DEFLECTION THEREOF SO THAT THE CENTRE OF PRESSURE OF THE VEHICLE SUPPORTING CUSHION MOVES OUTWARDLY TOWARDS SAID PORTION AND THEREBY EXERTS A STABILISING EFFECT ON THE VEHICLE.