Anti-surge flotation mattress

Claim 1

A flotation mattress engageable in a frame having a horizontal platform and vertical side and end rails about and projecting upwardly from the platform; said mattress including an outer bladder of flexible, supple, water impervious sheet material with a flat, horizontal platform engaging bottom wall, vertical rail engaging side and end walls and a flat normally horizontal depressable top wall; a volume of fluid medium within and slackly filling the bladder; a normally flat, horizontal intermediate wall of flexible material in spaced relationship between the top and bottom walls and dividing the interior of the bladder into upper and lower portions; a plurality of spaced, vertical partitions of flexible, supple material fixed with and extending between the bottom and intermediate walls and cooperating therewith to define elongate fluid conducting tunnels with opposite ends in said lower portion of the bladder; flow metering fluid transfer means communicating with and between related ends of the tunnels; flotation means at the intermediate wall normally buoying up and maintaining that wall and the partitions in their normal position within the bladder and wherein said flow metering transfer means includes fluid conducting chambers at and extending between adjacent ends of adjacent tunnels and membranes of flexible material overlying the ends of the tunnels and having flow metering openings communicating with the tunnels and the chambers.