Patent GB-825625-A (GB)
Title: Improved method of joining sheet materials
Inventor: RIEDESEL RICHARD G
IPC: C14B1/00
Filed: 1956-01-27
Abstract: 825,625. Seaming; laminates; coated fabrics. MINNESOTA MINING & MANUFACTURING CO. Jan. 27, 1956, No. 2817/56. Classes 42 (1) and 140. [Also in Groups XXIII and XXV] Abutting edges of flexible sheet material are spliced by slotting the material at the edges at an angle thereto and parallel to the direction of stress to be applied to the splice, holding the edges in abutting relationship and inserting strong, flexible, fine filaments within the slots and across the edges, and firmly adherently bonding the filaments within the slots. As shown, the ends of an abrasive-coated fabric belt 12 are cut at an angle of 45 degrees and slotted by means of a die which is pressed into the strip at the side opposite to the abrasive, to form open longitudinal channels 13a, 13b. The ends are abutted, touching or slightly spaced, and an adhesive strip 20 is placed above the joint. Strip 20 comprises a lower layer 21 containing short splicing filaments 15 parallel to channels 13a, 13b and an upper layer 22 containing long reinforcing filaments 19 parallel to the edges of the strip; layer 22 may be omitted. Pressure is applied by heated platens to cause the adhesive material to soften and carry filaments 15 into the open channels, and thereafter to cure the material to a thermoset condition. Filaments 15 may consist of strands of glass filaments with loose twist; alternatively, nylon or cellulosic filaments or fine piano wire may be used. Filaments 19 are preferably stretchable and may be of nylon; instead of lying parallel to the strip edges, they may be at right angles to filaments 15. Woven fabric may be used for reinforcement instead of filaments 19. The slots in the belt edges may have a depth equal to part or whole of the belt thickness and may be of the same or (as shown) different lengths. The adhesive material may be a resin composition, e.g. a blend of polyvinyl butyral resin and thermosetting phenol-formaldehyde resin; or, when splicing glue-bonded abrasive-coated belting, a film of animal glue may be used. In a particular example, an adhesive strip includes a carrier web of tough paper with a thin coating of polystyrene; on this is coated a layer of a composition consisting of equal parts by weight of polyvinyl butyral resin and thermosetting phenol-formaldehyde resin in a solvent, the composition being dried at normal room temperature; the surface of the resin layer is moistened with solvent and a layer of parallel, loosely twisted strands of glass filaments placed thereon; a further coating of the resin composition is then applied and dried so that the filaments are embedded in the middle of the resin film; the strip is then partially cured by heating for 45 minutes at 200‹ F. In the same example, the abrasive material from which belt 12 is cut is made as follows: a drill cloth is saturated with ethyl cellulose and dried; it is coated on one side with a phenolformaldehyde resin solution and dried; a gritbonding coating of a solution of the same resin is applied, silicon carbide grit is sprinkled on, and the resin partly cured; a further " sandsize " coating of phenol-formaldehyde resin solution is then applied and the material given a final cure.