1. Field of the Invention
The invention is directed towards a shadow mask back ring structure for use in color television picture tubes.
2. Description of the Prior Art
A shadow mask is an apertured, curved conductive member, which operates as the electron beam limiting electrode in a color television picture tube. An example of the typical shadow mask structure is seen in U.S. Pat. No. 3,639,799. The shadow mask typically has a curved aperture face portion surrounded by a solid skirt portion which is bent in a direction normal to the face portion of the shadow mask. This type of mask is typically formed of relatively thin metal to minimize the weight of the structure, and also to minimize thermal effects. It has been the practice to utilize a relatively thicker unitary metal reinforcing ring which is rigidly affixed to the back end of the mask shirt portion to strengthen and stabilize the shadow mask. It has been found necessary to use a unitary reinforcing ring to achieve the desired strength, and to avoid distortion due to nonsymmetrical thermal heating.
In preparing such a unitary reinforcing ring, it has been the practice to stamp such rings from large metallic sheets. This structure and fabricating process results in significant scrap losses, and thus is an expensive, high waste production process.