US2631254A

US2631254A - Geometrically coated cathode-ray tube

Info

Publication number: US2631254A
Application number: US263382A
Authority: US
Inventors: William H Nickless; Grunfelder Louis
Original assignee: ALLIED ELECTRIC PRODUCTS Inc
Current assignee: ALLIED ELECTRIC PRODUCTS Inc
Priority date: 1951-12-26
Filing date: 1951-12-26
Publication date: 1953-03-10
Anticipated expiration: 1970-03-10

Description

March 10, 1953 w. H. NICKLESS ET AL 2,631,254

GEOMETRICALLY COATED CATHODE-RAY TUBE Filed Dec. 26, 1951 Patented Mar. 10, 1953 UNITED STATE GEOMETRI ALLY COATED CATHODE-RAY TUBE William H. Nickless, Arlington, and Louis Grunfelder, Bergenfield, N. 3., assignors to'Allied Electric Products, Inc Irvington, N. J., a cor-- poration of NewJersey Application December 26, 1951, Serial No. 263,382

2 Claims. (01. 313-83) The invention herein disclosed relates to the manufacture of cathode ray tubes such as used in television receivers.

Particularly the invention is concerned with tubes of rectangular or other than circular shape.

These tubes are subject to cross burning of the picture screen, an action which impairs the quality of the picture and reduces the useful life of the tube.

Objects of the present invention are to eliminate and prevent these cross burning effects and thus to maintain and prolong the picture producing quality and efficiency of the tube.

Other, related objects are to accomplish these results in a simple, practical way and without adding to actual cost of the tube.

Other desirable results and the novel features through which the purposes of the invention are attained are set forth or will appear in the course of the following specification.

The drawing accompanying and forming part of the specification illustrates a present commercial embodiment of the invention. The construction, however, may be modified and changed within the intent and scope of the invention as hereinafter defined and claimed.

Figs. 1 and 2 in the drawing are companion, broken sectional views of a cathode ray tube incorporating the invention, Fig. 1 taken as on the plane of line ll of Fig. 2, and Fig. 2 taken as on the plane of line 2-2 of Fig. 1;

Fig. 3 is a cross sectional view of the tube as taken on substantially the plane of line 3-3 of Fig. 1;

Fig. 4 is a perspective view looking inside the tube after removal of the front wall carrying the picture screen, the side wall portions of the tube indicated in section.

The tube shown is of the rectangular type, having a picture screen 5 at the front, generally rectangular in shape and having a shallow groove 6 in the side of the same, in back of the screen.

The inner surface of the tube is covered with a conductive coating 1, extending from the neck portion of the tube, 8, toward the screen.

This internal conductive coating serves to prevent cross reflections within the tube and is used as a conductor, engaged by the contact springs or snubbers on the gun which is inserted in the neck.

The usual practice has been to extend the internal coating all the way to the groove 6 in the side of the tube, the bead 9 on the inside of the tube defining the location of this groove, being utilized as a marker limiting the extent to which the coating is applied.

In the operation of tubes so constructed, the high potential on the internal conductive coating creates lines of force extending from the edge of the coating across the face of the screen, these lines varying in value according to the distance from the edge of the coating at one side, across the screen to the edge of the coating at the opposite side of the tube. The rectangular shape creating these lines of unequal force establishes a pattern on the screen, which eventually shows up as the cross burns on the screen.

Cross lines of unequal potential are avoided in the present invention by giving the marginal edge of the internal conductive coating a geometrical contour such that radial lines extending from the center of the screen to the edge of the coating at opposite sides will all be of equal length.

In the example illustrated this gives the marginal edge a scalloped outline with deep concavities or recessions l0, Fig. 1, at the sides of the tube and similar recessions, l I, of lesser depth at the ends of the tube, Fig. 2, these curves joining and extending into points l2 at the corners of the tube. These points are closest to the screen since these corners represent the greatest radial distance from the center of the rectangular screen.

With the surface distance from the center of the screen to the edges of the coating constant for all radii, the potential across the screen from one edge to the opposite edge of the coating will be substantially uniform and the electrical stress on the screen occasioned by the coating, substantially equal at all points.

Cross burns and other objectionable results are thereby eliminated and at actually no greater cost in production. Less coating material is required but the coating is not reduced to the point where cross reflections will result.

While the coating contour shown, with scallops in the edge at the sides and ends of the tube, is a proper form for rectangular tubes, it will be realized that conformation may vary in accordance with shape of the screen, the main factor being that radial lines from the center of the screen to edges of the coating should be substantially equal at all points.

What is claimed is:

1. A cathode ray tube having a noncircular picture screen, and a conductive coating on the inner surface of the tube extending from the neck portion of the tube toward the screen and terminating in a non-straight edge contour with the surface distance from the center of the screen to the edge of the coating substantially constant for all 3 radii to present substantially equipotential radial lines extending in all directions through the center of the screen.

2. A cathode ray tube having a. generally rectangular picture screen and a neck portion in back of said picture screen, and a conductive coating on the inner surface of the tube extending from said neck portion toward the picture screen and terminating in a scalloped edge having curved recessions at the sides and ends of the tube, with those at the sides of greater depth. than those at the ends, and said curves at the sides and ends joining in points closely approaching the back of the screen at the corners of the generally rectangular formation and the surface distance from the center of the screen to the edge of the coating substantially constant for all radii.

WILLIAM H. NICKLESS. LOUIS GRUNFELQER.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number 1 Name Date 2,233,786 Law Mar. 4, 1941 2,312,206 Calbick Feb. 23, 1943 52 138,668 Koch .1 Mar. 30, 1948 2,183,457 Feld et a1 Oct. 4, 1949 2,527,981 Bramley Oct; 31, 1950 2,533,334 Sunstein et a1 Dec. 12, 1950