GB947218A - Collapsible optical projection screen unit - Google Patents

Abstract

947,218. Projection screens. AGFA A. G. July 14, 1960 [July 18, 1959], No. 24607/60. Heading G2J. A collapsible projection screen unit comprises a centrally-disposed supporting pillar to which are linked, on opposite sides, two parallel attachment members for a flexible screen and movable towards and away from the pillar while maintaining parallel relation therewith. As shown in Figs. 2 and 3, the screen 3 is stretched, when in use, between two rollers 4, one of which is spring-loaded, secured in respective halves 1 of a longitudinally-divided cylindrical shell. On extension of the screen by means of handles 2, the shell halves 1, as they move away from the previously enclosed supporting pillar 5, are maintained in parallel relationship therewith by means of the pivotal linkages of ribs 6 and struts 7. As shown in Fig. 6 the opening of the screen is assisted against the roller spring tension and frictional and inertial resistance, by a compression spring 13 which bears against a fixed disc 17 within the pillar 5 and serves both to push down the piston-like member 18 to cause outward splaying of the support legs and thereby, via cord 11 and a pulley, to exert upward pull on the piston-like member 10 thereby assisting the outward movement of struts 7 pivoted to the member 10 by pins 9. When the screen is fully opened, spring 12 is in slight tension. To close the screen, the handles 2 are pressed together. This causes extension of spring 12, as the element 10 is depressed until a catch 15 of the latter (see Fig. 8) is caught by a pin 16 fixed by spring 20 to the pillar 5. The tension in spring 12 is now sufficient to compress spring 13 via the cord 11 and member 18 and the legs are retracted against their spring loading at 14. When the screen is fully folded, the movements of the forces in struts 7 are such as to maintain closure until the shell-halves 1 are manually separated.