Aperture mask unit for color television picture tube

Claim 1

In a rectangular aperture mask structure for a color television picture tube composed of a thin metal sheet presenting a mask region of generally rectangular form and a peripheral flange surrounding the mask region and extending at an angle thereto, and a metal frame enclosed by the flange in a telescoping manner and fastened thereto by a plurality of spot welds distributed around the periphery of the flange, the flange being provided, at each corner of the structure, with two spaced cutouts extending from the edge of the flange remote from the mask region and defining a tongue which is curved, and thus stiffened, in the direction of the periphery of the flange, the length of the cutouts being equal to at least one-half the height of the flange, and each tongue being fastened to the frame by at least one spot weld, the improvement wherein said mask region includes a central aperture region and an imperforate border region extending around the periphery of said aperture region and disposed between said aperture region and said flange and said border region is provided with a continuous, peripherally extending recess.