Abstract: A heater adapted for placement under the mattress of a waterbed consists of a flexible laminated pad having an upper layer of resistive elements embedded in electrical insulating material, and several subjacent layers of heat-reflective and thermal insulating materials. All of the layers are encased in a protective waterproof sheath. The pad may be connected in parallel with one or more similar pads and a heat sensor may be associated with each pad. In one embodiment, a control circuit is provided for supplying power to all of the pads simultaneously when all of the heat sensors detect that the temperature of the mattress has dropped below a predetermined value. In another embodiment, power may be supplied to each pad independently of the other pads.

Abstract: A waterbed mattress is provided with a plurality of separate, free-standing cells, arranged in a "honeycomb" pattern. The cells are preferably hexagonal in plan. Each cell is provided with its own fill valve and is removably encased in its own protective waterproof pouch. The cells are held together by a cover member such as fitted sheet or a conventional zippered mattress cover. In the preferred embodiment of the invention, the cells are arranged in rows and columns on an insulating substrate having upstanding end portions alignable with the head and foot of a bed frame. Each upstanding end has a plurality of cut-out portions defining a jagged inner edge for receiving the corners of the hexagonal cells. The mattress assembly may also be provided with a heating unit comprising a plurality of heating pads electrically connected in parallel with one another and having a temperature control unit.