| 摘要 |
Thin, flexible sheets of water-impervious plastic material have their margins heat-sealed together and enclose a layer of insulating material of a size sufficient to cover the internal area of a tub. An internal bladder is of a size sufficient to cover at least the major portion of the water surface area of the tub, is supported on the intermediate sheet and itself is covered by a thicker, weather-resistant top sheet. The margins of all of the sheets are secured together and adapted to be secured to the curb or deck of the tub.
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