Patent 6739549 Issued on May 25, 2004. Estimated Expiration Date: November 12, 2022. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
A variable-lift device using a helium to fly. The device comprises a balloon (1) composed of an outer flexible envelope (3) supported by a rigid structure. The rigid structure comprises a plurality of hollow toruses (4) of inside volume that acts as a tank for storing helium under pressure.