Method and apparatus for stretching interchangeable tension masks in color cathode ray tubes

摘要

An apparatus and method for differentially stretching a flat tension mask to register apertures in the mask with an undedicated screen on a CRT faceplate. Stretching is accomplished biaxially on the mask with a plurality of separate clamping elements along all four sides of the mask. Various methods and means are disclosed for applying a fixed ratio of forces to the clamps to maintain strain in the mask substantially uniform across the entire mask, such as a "wiffle tree" linkage and selected spring rate springs. Growth of the mask during stretching is accommodated by allowing the clamps to move laterally or perpendicular to the stretching forces. Fragile slit aperture masks are stretched with clamps having tangential component stretching forces. Individual and/or groups of clamps can be controlled independently of others to correct for localized mask or screen defects. The clamps move in unison toward the mask to a clamp engagement position where they are precisely aligned in a starting position. With the mask precisely located and held, the clamps are engaged. The clamps and mask are then released by their aligning devices and stretching begins.