US3440469A - Flat screen attachment inside cathoderay tube by snap ring and clip assembly - Google Patents

Description

G. BRADU ET AL April 22, 1969 FLAT SCREEN ATTACHMENT INSIDE CATHODE-RAY TUBE BY SNAP RING AND CLIP ASSEMBLY Filed Aug. 29, 1967 Sheet of 2 lullllnlllllllllillllllllnnllllllllll FIGI INVENTORS GEORGES BRADU JEAN'PIERRE DRIFFORT ATTORN EYS April 22, 1969 BRADU ETAL 3,440,469

FLAT SCREEN ATTACHMENT INSIDE CATHODE-RAY TUBE BY SNAP RING AND CLIP ASSEMBLY Sheet Filed Aug. 29, 1967 FIG4b INVENTORS GEORGES BRADU JEAN-PIERRE DRIFFORT BY 11m 4%,

ATTORNEYS Int. or. non 29/24 US. Cl. 313-89 3 Claims ABSTRACT OF THE DISCLOSURE A flat screen is easily attached with precision to the inside forward face of a bulb of a cathode-ray tube by connecting the flat screen to a retainer ring placed in V-shaped grooves formed in cast bosses which are provided on the inside skirt of the forward face of the bulb. The plane of the retainer ring determines the plane of the fiat screen, and the plane of the retainer ring is held by the precision of the V-sha-ped grooves which have lines bisecting the angle of each groove in a plane parallel to the plane of attachment of the forward face portion tothe cone of the bulb and perpendicular to a longitudinal axis of the bulb.

This invention relates to improvements in the production of cathode-ray tubes, particularly tubes for color television. More specifically, the invention relates to a method of installation of a fiat screen easily and precisely within the forward face of the bulb, and to the assemblage arrangement.

It is known in the art, for reasons of simplification in the production process and for the purpose of reducing operating costs, that it is important to have fluorescent products on a perfectly true, flat and level surface within a cathode-ray tube rather than on the inside front on a conventional bulb provided with a skirt.

This invention involves providing, during casting of a skirted forward face portion of a TV bulb, bosses on the inside wall of the skirt, and then forming V-shaped grooves or slots in these bosses. The grooves are V- shaped slots in these bosses. The grooves are V-shaped or in the form of dihedrals with their apex in the same plane and lines bisecting the angle of the dihedrals lying in the common plane perpendicular to a longitudinal axis of the bulb and parallel and spaced from a supporting edge of the skirt. The fiat screen is then installed within the forward face of the bulb and supported on a plane defined by the position of a metal retainer ring of circular cross section which is held in the V-shaped slots. The flat screen is held firmly against the ring.

The fiat screen, covered with its conducting layer, is applied to the metal retainer ring by means of a metal frame which is secured to the retainer ring in the last step of the installation process by clips which are bent to hold the flat screen tight against the retainer ring while the screen is positioned between the frame and the retainer ring.

In assembly, the metal frame is first placed over the bosses inside the forward face, followed by the fiat screen and finally the snap retainer ring is installed in the grooves in the bosses of the skirt. The retainer ring instantly snaps into the groove and requires no special procedures for centering or for referencing it with other parts. The only step required to complete the assembly is to fold the holding clips of the metal frame to make a rigid assemblage of the metal flat screen and retaining ring.

The screen is thus rigidly held against the perimeter of the retaining ring in a predetermined plane. This plane is United States Patent Patented Apr. 22, 1969 referenced with extreme precision because it is not at all difficult to cut slots of dihedral form in the bosses so that the apex of each slot will be in a plane parallel to the plane formed by the true edge of the skirt which serves as a reference plane, and at a precise distance from this reference plane. It is also a precise reference because the metal retainer ring of circular cross-section is engaged by the dihedral or V-shaped grooves and assumes a precisely determined position (with the plane of its axis coincident with the plane defined by the 'apexes of the V- shaped grooves.

The bendable clips or clamps for the attachment of the frame to the retainer ring may be welded to one or the other face of the frame. The frame is tightly held against the screen and the thickness of the clips may be used to slightly space the screen from the frame. Of course, the clips can be an integral part of the frame without being welded thereto and the frame can be positioned directly against the screen. The clips can have any suitable shape or dimension, but in one version which is particularly advantageous for the attachment of a flat screen, the clips are provided with an oblique cut with respect to the plane of the retainer ring so that, by bending the clip over the ring along the oblique portion automatic tightening of the assembly consisting of the screen, metal frame, and retainer ring is obtained. Moreover, the handling of these clips requires no complicated tools nor does it require a skilled worker to perform this operation.

The assembly thus obtained has both great rigidity and flexibility sufficient to permit heat treatment required in the production of the tube such as welding of the grid and cone as well as the preparation of the vacuum, or the jolting tests, etc.

It is desirable to select a metal for the retainer ring which has a heat expansion coefiicient that will be less than ore equal to that of the glass of the bulb; this would prevent risk of damage to the walls of the dihedral shaped grooves during the heat treatment.

It is necesary, in cathode-ray tubes, to provide a conductor that runs through the tube wall to connect the fiat screen to a continuous potential to permit the attachment of the potential to the screen. In this invention a conductive layer, covering the screen, is in contact with the metal retainer ring at a very large number of contact points, if not along its entire periphery. It therefore sufficies to connect the conductor which runs through the wall of the bulb to any point of the metal retainer ring.

By way of non-restrictive example, one method of employing the procedure involved in this invention and the assemblage of components :will be described with reference to the attached drawings, in which:

FIG. 1 is a longitudinal axial section taken through a bulb illustrating the assemblage of this invention.

FIG. 2 is a plan view from the interior of the forward face of the bulb.

FIG. 3 is an enlarged sectional detail view of one boss and the assemblage with respect thereto.

FIGS. 4, 4a, and 4b are detail elevational bottom plan and side views respectively of the arrangement for attaching the frame to the metal retainer ring.

In FIG. 1 there is shown a bulb with a skirted front face 1 and a cone portion 2. An edge 1a of the skirted front face and edge 2a of the cone portion are aligned so that the plane of joint 10 will be perpendicular to the longitudinal axis of the bulb. The front or forward face 1 is provided with a plurality of spaced bosses 3 which are cast integrally with the skirted front face of the bulb. In each boss a groove 4 is formed in the shape of a dihedral Le. a V-shaped groove, having an apex 4a. The apex of each groove is in a common plane as are lines which bisect the angle of each V-shaped groove and this plane is parallel to the plane of joint 10 and hence normal to the longitudinal axis of the bulb. The grooves 4 can be obtained from the cast front face 1 by mechanical working such as milling or grinding with a precision in the order of a few hundredths of a millimeter.

Prior to the time the front face 1 of the bulb is welded to the cone portion 2 a metal frame 6 provided with notched portion 7 is positioned between the inside of the front face and the bosses 3. Notches 7 in frame 6 permit the frame to pass over the bosses 3.

A fiat screen 9 with an inside face 11 provided with fluorescent products which are covered with a conducting layer 11a is then introduced. This screen is also provided with notches 3a which permit its passage over the bosses 3.

A continuous unetal retainer ring which may be a snap ring is placed in the grooves 4. In order to facilitate placing of the ring, it can be cut and provided with a sleeve to connect its ends after placement.

FIG. 3 shows an enlarged detail across a boss 3, and the relative position assumed by the metal snap retainer ring 5, the screen 9 which on its inside face 11 bears the phosphor dots and the conducting layer 11a, and the metal frame 6 which, in the embodiment shown is spaced from the screen by the thickness of the clips 8, see FIG. 4.

Referring to FIGS. 4, 4a, and 4b it can be seen that frame 6 carries clips 8 having oblique cuts 12 therein (FIG. 4b), frame 6 is connected to retaining ring 5 by bending tang 8a of the clip 8 (FIG. 4a). The fact that notch 12 is cut at an oblique angle to the plane of the retainer ring 5 provides for automatic tightening of the assembly sandwiching screen 9 between frame 8 and ring 5 and firmly clamping the screen in a precisely predetermined plan or position.

For greater clarity in the drawings a considerable space is shown in FIG. 2 between bosses 3 and attachment clips 8. However it is important to place the clips as close as possible to the bosses since the position of the metal :wire retainer ring 5 is rigorously determined by the dihedral or V-shaped grooves of the bosses. Clips could be provided on either side of each boss in order to increase the reference precision without in any way interfering with the flexibility of the assembly which remain assured 'by the fact that the metal wire may glide in the grooves 4 during the heat treatment operations.

After the phosphor bearing screen has been assembled, as described above, the forward face portion 1 may be sealed to the cone portion 2 of the bulb, providing the electron optics of the tube so requires, by attaching grid 13 in the plane of the joint.

As shown in FIG. 2 a lead in conductor 14 extends through the wall of the tube and is connected to the metal retainer ring or snap ring 5 for applying potential to the flat screen.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An assemblage for attaching a flat screen to the inside of a skirted face portion of a bulb for a cathode-ray tube, the bulb having a cone portion joined at its edge to the edge of the skirt of the face portion, the assembly comprising: spaced bosses cast in the inside skirt of the face portion, V-shaped grooves in the bosses, one groove being formed in each boss and positioned so that a line bisecting the angle of each groove is in a common plane parallel to the plane of the joint between the edge of the skirt and the cone portion and perpendicular to a longitudinal axis of the tube, a flat screen, a retainer ring of circular section inserted in the grooves defining a support plane parallel to the plane of the lines bisecting the angle of the grooves, and means holding the screen rigid with and parallel to the retainer ring in the support plane.

2. An assemglage as defined in claim 1 wherein the clips include a bendable tang having a holding edge formed at an angle to the plane of the retainer ring.

3. An assemblage as defined in claim 1 wherein the retainer ring is of conductive metal in contact with the surface of the fiat screen and further comprising a conductor extending through the wall of the tube and connected to the ring.

References Cited UNITED STATES PATENTS 2,100,703 11/1937 Schlesinger 313-92 2,733,366 1/1956 Grimm et al.

2,856,552 10/1958 Evans.

2,973,454 2/1961 Heil.

2,982,874 5/ 1961 Van Doorn.

ROBERT SEGAL, Primary Examiner.

US. Cl. X.R.

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