US3512031A - Triangular electrode support having two rigid and one flexible support surface in contact with cathode ray tube neck - Google Patents

Description

May 12, 1970 A. E. OBERG 3,512,031

TRIANGULAR ELECTRODE SUPPORT HAVING TWO RIGID -AND ONE FLEXIBLE SUPPORT SURFACE IN CONTACT WITH CATHODE RAY TUBE NECK Filed March 8, 1968 2 I J I 8 Q// e2 6| I I FIG. 3

WITNESSES: so INVENTOR M lflsziwaw AlberT Oberq ATTORNEY United States Patent 3,512,031 TRIANGULAR ELECTRODE TWO RIGID AND SURFACE IN CONTACT WITH CATHODE RAY TUBE NECK Albert E. Oherg, Horseheads, N.Y., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 8, 1968, Ser. No. 711,595 Int. Cl. Hlllj 19/52, 1/98 U.S. Cl. 313-488 SUPPORT HAVING 1 Claim ABSTRACT OF THE DISCLOSURE Brief summary of the invention In several types of cathode ray tubes, optimum electrical operation requires that the electron gun be located coaxially within the neck portion of the cathode ray tube. The tube performance is a function of how well this location is held throughout temperature extremes of manufacturing processes and subsequent operation as well as the effect of shock and vibration. In prior art devices, ring clips and micra collars have been utilized but these do not satisfactorily compensate for parts tolerances, differ ences in thermal expansion and the possible deterioration of the support such as mica. The use of precision mica washers leads to the presence of small mica particles within the envelope which can attach to the phosphor screen and cause voids in the light output of the screen. The use of rigid metal or glass spacers has resulted in breakage of tube due to unequal thermal expansion of the spacers within the tube neck.

One specific application, wherein concentricity of an electrode cylinder of the electron gun in the tube neck is critical, is a bi-potential electron lens in a high resolution cathode ray tube. In many of these devices, the electric focusing field is formed by a rolled edge electrode cylinder at focus voltage and a surrounding and coaxial conductive coating on the inside surface of the neck at anode voltage. The concentricity of the electrode cylinder and the conductive coating is essential to assure symmetry of the electric field with the tube axis in order to avoid astigmatism.

It is accordingly the general object of this invention to provide an improved centering support spacer for an electron gun within a cathode ray tube. This is accomplished by providing a spacer member secured to the outer periphery of the electrode. The spacer member is provided with two rigid bearing points on the inside surface of the cathode ray tube spaced apart by about 120 with at least one resilient bearing point in the remaining 240 sector and substantially opposite the rigid support bearing members to hold the assembly tightly within the tube neck.

Brief description of the drawings FIG. 1 is an elevational view, partly in section, of a cathode ray tube embodying the principles of the present invention;

ONE FLEXIBLE SUPPORT r 3,512,031 Patented May 12, 1970 FIG. 2 is an enlarged View of a portion of FIG. 1; and FIG. 3 is a sectional view taken along line III-III of FIG. 2.

Detailed description Referring now to FIG. 1, there is illustrated a cathode ray utbe 10. The tube 10 comprises an evacuated envelope 12 which includes a neck portion 14, a flared portion 16 and a faceplate 18. The neck portion is closed off with a base member 20 through which electrical leads pass to provide suitable potentials to certain of the electrodes within the envelope 12. Positioned on the inner surface of the faceplate 18 is an electron responsive phosphor screen 22 of any suitable type and an electrically conductive coating 24 of suitable material such as aluminum is evaporated onto the inner surface of the phosphor layer 22. An electrically conductive coating 26 is also provided on the inner surface of the flared portion 16 which is in electrical connection with the coating 24 and also an anode button 28. A suitable potential of about 10,000 volts may be applied to the anode button 28 from an external potential source which places the conductive coating 26 and the conductive coating 24 at a similar potential. The coating 26 as can be seen'from the drawing extends from the flared portion back into the neck portion 14 and forms one of the lens elements with an electron gun structure 30.

The electron gun 30 is positioned within the neck portion 14 of the envelope 12. The neck portion 14 is of a precision type tubing so that the internal diameter thereof is within tolerances of plus or minus .0005 inch. The electron gun 30 includes a cathode 32 which consists of a small tubular member having an end cap upon which an electron emissive material is provided. A heater is provided with the tubular member. A grid member 34 including a large tubular portion surrounds the cathode 32. A diaphragm 36 is provided on one end of tubular portion with an aperture therein aligned with the end cap of said cathode 32 and with the electron emissive coating positioned adjacent to the aperture. A second grid member 38 is provided adjacent the grid 34 and is also tubular in configuration and of similar diameter as said grid 34 and is provided with a diaphragm 40 having an aperture therein and aligned with the aperture in the diaphragm 36. The cathode is normally held at a potential of zero, the first grid at potentials ranging from zero to about minus seventy five volts and the second grid 38 at a potential of about 300 volts. The next electrode in the electron gun 30 is the first anode 42 which is an elongated tubular member of similar diameter as the grid electrodes 34 and 38. A diaphragm 44 is provided at approximately two-thirds of the distance from the end adjacent the grid 38 and is provided with an aperture. The end of the tubular anode 42 facing the screen 22 is provided with an extension section 46 which is tubular in shape but of a larger diameter than the remaining portion of the anode 42 and is provided with a rolled edge thereon facing the screen 22. This extension portion 46 extends into the neck portion of the envelope in which the conductive coating 26 is provided so that an electric field is established between the conductive coating 26 and the anode extension 46. The electric field modifies the trajectories of the passing electrons, causing their paths to converge at the phosphor screen 22. The anode 42 operates at a potential of about 5000 volts. The anode 42 must be concentric with the neck 14 in order to insure symmetry of the electric field between the anode 42 and the coating 26.

The accurate positioning of the anode 42 with respect to the coating 26 is accomplished by the spacer members 60 which are mounted on the anode 42. Two similar spacers 60 are spaced along the length of the anode 42.

The spacer member consists of a triangular shaped washer member 62 having a circular opening 61 which is positioned about the outside diameter of the tubular anode 42. A stop member 67 is mounted on the anode 42 and on each side of the washer 62 to secure the washer on the anode 42. In the specific device the stop member is a split ring which is welded to the anode 42. The Washer member 62 is flat having a thickness of about .03" and of a suitable material such as a non-magnetic stainless steel. The outer periphery of the washer 62 is an equilateral triangle with the three corner points of the triangle cut off as illustrated. Two of the corners 66 and 68 are precisely cut to provide a bearing surface having the same radius of curvature as the inside surface of the tube neck 14 so that the anode 42 is concentrically positioned within the neck 14 when the anode is pressed against the rigid bearing surfaces 66 and 68. The third corner of the triangle 70 is cut off shorter than the corners 66 and 68 and is used as a mounting location for a spring member 72. The spring 72 is deformed on insertion of the assembly into the neck 14 so that it exerts a radially outward force on the neck 14. A suitable material for the member 72 is non-magnetic stainless steel. The thickness may be .01" and the width 0.12". The reactive force is radially inward to force the two rigid contacts 66 and 68 firmly against the inside surface of the neck 14 to accurately position the assembly concentric within the neck 14. In the specific embodiment shown, two spacers 60 are provided to insure an alignment of the anode 42 within the neck.

The electron gun 30 is assembled prior to insertion into the tube and the grid electrode 34, the electrode 38 and the anode 42 are assembled as a unitary structure by suitable means such as lugs 74 extending from the electrode elements which are embedded in suitable insulating rods 76. Normally three of the rods 76 equally positioned about the periphery provide adequate support.

It is noted that the supports 66 and 68 are spaced 4 about 120 apart about the periphery forming a sector 80 and the point 70 is positioned intermediate of these two points in the remaining sector 82 of 240. It is found that the points 66 and 68 should be spaced about to apart and at least one spring member positioned in the remaining larger sector 82.

While the preferred embodiments of the invention have been disclosed herein, it is obvious that many modifications are feasible within the spirit and scope of the invention.

I claim as my invention:

1. A cathode ray tube comprising an evacuated envelope including a tubular neck portion, an electron gun including at least one tubular electrode, means for positioning said tubular electrode coaxially within said neck portion comprising a transverse member having an inner circular opening, said tubular electrode being secured within said circular opening, said transverse member further having a triangular periphery including a rigid References Cited UNITED STATES PATENTS 2,119,559 6/1938 Ronci 313258 X 2,546,976 4/1951 Clark et a1. 3l3258 X 2,830,225 4/1958 Moore 31368 X 3,038,094 6/1962 Ney 313-68 X ROBERT SEGAL, Primary Examiner US. Cl. X.R. 313-258, 292

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