US Patent 6837951 Method of thermoforming a bladder structure

A method for thermoforming a resilient, fluid-filled bladder structure with thermal contact molding is disclosed. The bladder includes two sheets of thermoplastic material that are separated by at least one core formed of two spaced outer layers connected together by a plurality of connecting members. The bladder is formed by bonding the sheets to the core, bonding the sheets to each other around the periphery of the core and forming a sidewall between the sheets in a single mold. A fluid is then inserted into the space bounded by the peripheral bond and the two sheets such that the connecting members are extended.