Method for manufacturing luminous hollow bodies for signs or the like

In a method for manufacturing hollow bodies adapted to be used for luminous signs, comprising the steps of first molding an endless wall of predetermined configuration, so that said endless wall will form an open-ended endless side wall of the final hollow body, and then molding at only one end of the space confined within said endless wall an end wall of the hollow body joined to said endless wall along an end region thereof, so that the thus-molded end wall together with the thus-molded endless side wall will define a space adapted to receive light which can travel through said end and side walls of the hollow body to form at least part of a luminous sign, said molding of said endless side wall of the hollow body comprising the steps of situating around an inner mold member on an upper substantially flat surface of a support a plurality of layers of thermosetting synthetic resin which rest at bottom side edges thereof on said upper surface of said support during an interval when said layers of thermosetting synthetic resin are still hardening but have not fully set and are self-sustaining while still being soft enough to be molded to a desired configuration with each of the layers having at least one desired characteristic of strength, light-transmission, and the like which are to be included in the final hollow body, and each layer having a width corresponding to the desired depth of the luminous hollow body which is to be manufactured, and placing on said upper surface of said support around said layers a plurality of sections of an outer mold member which when joined together will surround the inner mold member while defining therewith a cavity of predetermined configuration and thickness corresponding to the desired configuration and thickness of the endless side wall of the hollow body, and then bringing said sections of said outer mold member together on said upper surface of said support for pressing the innermost of said layers against the exterior surface of said inner mold member fand the outermost of said layers against the inner surface of the outer mold member formed by bringing the sections thereof together, while said layers will engage each other and fuse together during continued setting of said layers, and maintaining said outer mold member with its sections joined to each other in engagement with said outermost layer while said innermost layer remains in engagement with said inner mold member until a sufficient time has elapsed for said layers to have hardened and set sufficiently to remain in the configuration desired for the final hollow body at the side wall thereof, and thereafter removing the outer and inner mold members from the layers so that the side wall of the hollow body produced thereby will have a precisely determined thickness as well as a precisely determined configuration at its inner surface as well as its outer surface and a texture at its inner and outer surfaces determined by the characteristics of the outer surface of the inner mold member and the inner surface of the outer mold member, respectively.