Patent 5335380 Issued on August 9, 1994. Estimated Expiration Date: November 3, 2012. 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 spring insert for a waterbed mattress includes a plurality of spring bellows units arranged in upright relation within the mattress. Each bellows unit has a top wall and pleated sidewall which is collapsible from a normal expanded height to a shortened compressed height wherein the internal volume of the bellows unit is substantially reduced. Each bellows unit furthermore has a bleeder opening through one wall so that a compression load exerted on the bellows unit through the mattress top wall is resisted by both spring action and hydraulic action of the bellows units. The bellows units may be interconnected to form upper and lower sections arranged in stacked relation. Stacked pairs of upper and lower bellows units may be arranged in fluid communication to define joint hydraulic chambers.