Patent FR-1254078-A (FR)
IPC: B60V1/12
Filed: 1960-03-23
Granted: 1961-02-17
Abstract: 944,502. Air cushion vehicles. HOVERCRAFT DEVELOPMENT Ltd. March 21, 1960 [March 23, 1959], No. 9900/59. Heading B7K. In a vehicle for travelling over a surface and which in operation is supported above that surface by cushions of pressurised gas formed and contained beneath the vehicle, said cushions being contained at least in part by curtains of moving fluid which travel across the gap which in operation exists between the bottom of the vehicle and the surface over which it is travelling, the means for forming said fluid curtains constitute at least part of the means whereby at least two cushions or compartments of a cushion are set up, at least one of which has its centre of pressure removed from the vertical axis through the centre of gravity of the vehicle and is adapted to provide a stabilizing moment on the vehicle. The invention is concerned primarily with vehicles such as shown in Fig. 1 having an outer, primary port 3 and an inner secondary port 4 whereby a primary cushion 5 and a secondary cushion 6 are formed, the pressure of cushion 6 being intermediate between that of cushion 5 and atmosphere. If such a vehicle tilts, the increased local pressure in cushion 6 at the point where the undersurface of the vehicle approaches the ground causes a local splitting of the inner curtain so that it tends to flow inwards. This in turn results in further inclination of the vehicle, the local loss of all the air forming the inner curtain and part of the air forming the outer curtain. A variety of ways of preventing the loss of pressure in the secondary cushion are described; one involves the cross-connection of the inner and outer ports by a plurality of radial connecting ducts or, as stated to be preferred, forming the outer port as a series of lobes, Fig. 7. In another arrangement, Fig. 12a, not shown, the inner port is blanked off at points around its circumference to form radially outwardly directed ports which result in the local outflow of the inner cushion to form transverse gaseous curtains dividing cushion 6. In the arrangement of Fig. 16 (not shown), secondary cushion pressure is maintained when the vehicle becomes inclined by making the undersurface between the primary and secondary ports upwardly inclined. Figs. 17-20 (Fig. 20 only shown) disclose arrangements in which the flows from inner and outer curtains may be relatively varied around the circumference of the vehicle for the purpose of adjusting the secondary cushion pressure locally in order to trim the vehicle. In Fig. 20, each curtain is formed from two ports, the outer curtain by ports 50 and 51 fed by ducts 52 and 53 and the inner curtain by ports 54 and 55 fed by ducts 56 and 57 respectively. In each pair the outer duct is wider than the inner and a hinged valve member formed from two parallel flaps 58a and 58b is mounted at the junction of the ducts in such a manner that the flows through the inner ducts 53 and 57 is unaffected, only the relative flows to the outer ducts 52 and 56 being varied. The flaps are circumferentially divided so that flow variation may be varied circumferentially, preferably being increased and decreased respectively at diametrally opposite positions. In an alternative arrangement (Fig. 23, not shown) the inner and outer ports are formed in the bottom wall of an annular duct which carries a plurality of circumferentially-spaced slide valves whereby the relative flows through the ports may be varied. In a further embodiment (Fig. 24, not shown) the cushion is contained by side walls and double cross-curtains ejected at each end of the vehicle from the side walls form fore-and-aft secondary cushions. In still further embodiments (Figs. 25 and 26, not shown) the lateral division between the primary and secondary cushions comprises keel-like members which may have provision for ejecting a gaseous curtain. Specifications 854,211, 893,715, 894,644, 895,341, 944,503 and 944,504 are referred to.