Firmness regulated waterbed mattress

Claim 1

A waterbed mattress for use with a waterbed frame comprising: (a) impervious plastic sheet material forming a top mattress layer and a bottom mattress layer; (b) a plurality of individual tie structures arrayed about the operative area of the mattress; (c) each tie structure including a resilient and highly elastic element anchored at opposite ends of the respective mattress layers; (d) each tie structure having a low spring constant thus to yield as the top layer bulges upwardly under the load of an occupant or under the load of water fill; (e) each of the elastic elements being stressed when the mattress, peripherally confined by the frame, is filled with water beyond a nominal level whereby said elastic ties impose stress upon the said upper mattress layer resisted by the volume of fluid in the mattress thereby to determine the firmness characteristic of the mattress; and (f) a substantially cylindrical baffle located about the said elastic element of each tie structure, each baffle having a keyhole slot for placement after the tie structure is attached to the top and bottom layers.