Abstract: A frame for a projection screen or the like may be fabricated of elongated round tubular members running one direction and polygonal (preferably rectangular) cross section members running in the other direction connected together into a grid by clamps at their intersections. The clamps are parallel plates affixed to the parallel surfaces of the polygonal support members and have a rounded groove in an edge generally conforming to the rounded cross section. Clamp means to hold the round members in the grooves are conveniently formed of U-bolts which are secured to flanges generally normal to the planar surfaces of the bracket. The frame is particularly useful for compound curved surfaces including generally spherical domes. In such configurations the rectangular elongated support members are arranged as latitudes and the round section members as longitudes outside of the rectangular members.

Abstract: A frame for a projection screen or the like may be fabricated of elongated round tubular members running one direction and polygonal (preferably rectangular) cross section members running in the other direction connected together into a grid by clamps at their intersections. The clamps are parallel plates affixed to the parallel surfaces of the polygonal support members and have a rounded groove in an edge generally conforming to the rounded cross section. Clamp means to hold the round members in the grooves are conveniently formed of U-bolts which are secured to flanges generally normal to the planar surfaces of the bracket. The frame is particularly useful for compound curved surfaces including generally spherical domes. In such configurations the rectangular elongated support members are arranged as latitudes and the round section members as longitudes outside of the rectangular members.