GB1236571A - Improvements relating to gas-cushion vehicles - Google Patents

Abstract

1,236,571. Air cushion vehicles. HOVERCRAFT DEVELOPMENT Ltd. 12 July, 1968 [13 July, 1967], No. 32349/67. Heading B7K. An air cushion vehicle has a flexible skirt comprising an upper part 19 made of a flexible impermeable sheet, and a lower part 18 which is preferably of the type disclosed in Specification 1,043,351 and depends from the upper part except near the bow of the vehicle where it depends directly from the body of the vehicle, the members 18 of the lower part adjacent the sides of the vehicle being attached to variable length ties thereby to displace at least a part of the lower part of the skirt relative to the body of the vehicle and provide an adjustment of the centre of pressure position. The two parts of the skirt contain an air cushion 17, air being supplied to the cushion by a fan 14 which is driven by a motor 15 and draws air through a duct 13. The vehicle is propelled by a power unit P. In Fig. 5, the ties 22 attached to the members 18 pass into the body of the vehicle via air tight seals 24 and are wound on to shafts 23 which extend parallel to the fore-aft axis of the vehicle. Each shaft 23 tapers towards its ends so that when a shaft 23 is rotated, the length of a tie wound around the centre of the shaft varies more than the length of a tie nearer an end of the shaft, and there is thus a differential movement of the skirt members 18. Each shaft 23 has shallow grooves to prevent the ties moving sideways along the taper of the shaft. When a shaft 23 rotates, the area between planes A-A of Fig. 5 which contains the effective lifting cushion 17 is displaced laterally to alter the trim of the vehicle. The shafts may be rotated by equal amounts in the same sense so as to move the whole cushion whilst retaining a constant cushion area, or may be moved by unequal amounts in which case the cushion area changes. A similar arrangement may be used with a shaft at the stem of the vehicle transverse the fore-aft axis to differentially move the lower part of the skirt at the stern of the vehicle and thus provide pitch control. The shafts are driven by electric motors which may be coupled to attitude sensing switches, e.g. mercury switches, to provide automatic attitude control. Instead of tapered shafts, cylindrical shafts having circumferential grooves may be used, the grooves being deeper near the ends of the shafts.