Double wall storage tank for liquids

DETAILED DESCRIPTION In view of the foregoing, it is the object of the present invention to provide an economical method of manufacturing a double wall storage tank from rigid single wall tank.
It is a further object of the invention to provide such a method in which at least a portion of the outer wall or sheath of the tank is spaced from the inner tank.
It is an additional object of this invention to provide a double wall storage tank in which at least a portion of the outer wall or sheath of the tank is spaced from the inner tank.
To achieve these and other objects that will become readily apparent to those skilled in the art, this invention provides a method of manufacturing from a rigid, single wall inner tank a rigid double wall tank for the storage of liquids.
The method includes the steps of applying to at least a portion of the outer surface of the inner tank a spacing material comprising a flexible sheetlike material having a continuous and generally planar surface with a plurality of projections extending outwardly of the planar surface on at least one side of the material, the material being applied to the inner tank with projections engaging the inner tank outer surface, and then applying over such inner tank outer surface and the spacing material a sheath of a material that is substantially rigid and liquid tight.
The projections on the spacing material serve to space the planar surface of the spacing material from the outer surface of the inner tank to provide for substantially free passage of liquids between the inner tank outer surface and the spacing material planar surface.