GB808744A - Improvements in or relating to multi-section motion picture projection screen - Google Patents

Abstract

808,744. Seaming non-metallic sheet materials. HURLEY, A. B. June 15, 1956 [June 16, 1955], No. 18629/56. Class 42 (1). [Also in Group XX] A projection screen (see Group XX) comprises a pair of light-reflective sheets 2, 4 of heatsoftenable material arranged with opposing edges 10, 12 adjacent one another and a filamentary element 6 embedded in the sheets and extending from one sheet to the other between the edges. The sheets 2, 4 may be of cellulose or vinyl acetate, lucite or vinyl resin or vinylidene chloride while the element 6 may be an electrical resistance wire. Heat is applied by passing A.C. or D.C. through the wire, by induction heating of the wire or by localized dielectric heating of the sheets while a head with an operative surface of a dielectric material, such as glass, applies pressure to the wire to embed it in the sheets. To prevent discolouration of the sheets due to burning, the head and the bed on which the sheets are supported may be cooled. The arms 14, 16 of the element 6 may be downwardly-inclined about their central points to form an inverted V-shape in section or they may form a V or curved shape in plan. Two wires or filaments may be twisted or braided together to form the element 6. The Specification gives details of sheet and wire sizes, pressures employed, heating times &c., and states that the element may be arranged to fuse when it has attained the desired temperature.