US Patent 7269866 Air bed with stable supporting structure

An air bed with a stable supporting structure comprises a periphery sheet, a top sheet, and a bottom sheet. A middle sheet separates the air bed into an upper air-chamber and a lower air-chamber, an outer extending strip separates the upper air-chamber into a peripheral air-chamber and an upper main air-chamber, a first set of extending strips is provided in the upper main air-chamber, a second set of extending strips, which is welded to the middle sheet and the bottom sheet, is provided in the lower air-chamber, and an oblique extending strip is provided around the periphery of the second set of extending strips and is welded with the periphery sheet and the bottom sheet to separate the lower air-chamber into a lower main air-chamber and a peripheral auxiliary air-chamber. The lower main air-chamber is a space which has a shape of an inverse cone and receives air therein. Its outer surface is concave with respect to the outer surface of the peripheral auxiliary air-chamber, that is, the surface of the peripheral auxiliary air-chamber extends beyond the surface of the bottom sheet of the lower main air-chamber.