Thermal compensation for color television picture tube aperture mask

Claim 1

In a color television picture tube having a faceplate, a skirt extending from said faceplate, and an aperture mask, said aperture mask being situtated within said tube behind said faceplate and supported by a four-sided frame, apparatus to compensate said tube for expansion of said aperture mask therein due to a temperature rise of said mask so as to maintain registration between apertures in said mask and predetermined regions on said faceplate, said apparatus comprising: first and second temperature responsive means attaching said frame to the faceplate skirt at each of two points on said skirt situated such that each of said two points is located along a horizontal axis situated below the horizontal centerline of said frame and is coupled to an opposite one of the four sides of said frame below said axis, respectively, each of said temperature responsive means tending, for any given rise in temperature thereof during normal operation of said tube, to thrust the side of said frame to which it is respectively attached toward said faceplate be a predetermined distance; and third temperature responsive means attaching a third one of the four sides of said frame to said faceplate skirt at a third point on said skirt, said third temperature responsive means tending, when experiencing said given rise in temperature, to thrust said third one of the four sides of said frame towards said faceplate by a distance other than said predetermined distance.