US3404933A - Method and apparatus utilized in repairing electron tubes - Google Patents

Description

'Oct. 8,1968 R.J.WE|DEMAN 3,404,933

METHOD AND APPARATUS UTILIZED IN REPAIRING ELECTRON TUBES Filed Dec. 19, 1966 GAS WM sumv IZOSIT/ONTUBE $544 w C/l L L EVACUA TE CHAMBER fl OPE/V SEAL INERT 4mm; i

L ADM/r INVENTOR. Rosa/er .f, WE/DEMAA/ g/A/mf/w A TTORN' Y United States Patent 3,404,933 METHOD AND APPARATUS UTILIZED IN REPAIRING ELECTRON TUBES Robert John Weideman, Ottawa, Ohio, assignor' to Sylvania Electric Products Inc., a corporation of Delaware Filed Dec. 19, 1966, Ser. No. 603,035 11 Claims. (Cl. 3162) ABSTRACT OF THE DISCLOSURE An improved method and means for opening an evacuated electron tube, having an externally projecting seal, and preventing the entrance of contaminants thereinto. The tube portion containing the seal is vertically oriented in a small hermetic cham'berrfrom which the environ- This invention relates to electron tubes and more particularly to an improved method and apparatus utilized in the repairing of defective cathode ray tubes.

Cathode ray tubes, whether they be of the monochrome or color variety, basically comprise a cathodoluminescent screen and at least one electron beam generating means contained within an evacuated envelope. It is conventional practce to fashion the envelope in a substantially funnelshaped manner, the expansive portion having a terminal closure in the form of a face panel with the cathodeluminescent screen disposed relative to the interior surface thereof. Within the neck portion of the funnel, one or more electron guns are positioned in a manner to beam electrons to the screen. Usually, the evacuation seal'projects externally from the terminal closure of the neck portion as does an array of metallic pins effecting external electrical connections for the several internal components of the tube.

There are occasions when a tube is found to contain a malfunctioning or defective component, such as an electron gun assembly. A situation of this type may arise during tube manufacturing or as a result of tube operation. When the other components of the tube are considered to be satisfactory, it is conventional practice to repair the tube by removing the defective gun and replacing it with a new one. Essentially, this involves disturbing the vacuum of the tube, removing the defective gun by cutting off a portion of the neck of the tube, resealing a new neck portion thereto, sealing a new gun mount into the renecked tube, and thence exhausting and processing the repaired tube in accordance with conventional processing and aging practices.

The initial step in the repairing operation, as noted above, is that of disturbing the vacuum wherein the evacuated tube is opened and a fill of an inert non-contaminating gas is admitted to prevent an inflow of con taminating gases such as oxygen, carbon dioxide, water vapor and the like, which, if sorbed by the internal parts of the tube, would be detrimental to subsequent tube operation. It has been conventional practice to discretely puncture the neck of the tube in the presence of a surrounding non-contaminating atmosphere and allow this atmosphere to flow through the opening and fill the tube. Usually, the puncture operation is consummated in one of two ways, either by utilizing a heated metallic tip to melt a hole in the glass or by boring a hole therethrough by means of a rapidly revolving drill. Both of these methods have disadvantages in that heat releases gaseous contaminants such as water vapor and objectionable hydroxides from the adjacent glass, and drilling produces finechips land particled glass materials. Thus, as the vacuum in the tube is disturbed, the aforementioned and other deleterious gas borne foreign materials, ambient to the tube, are undesirably sucked into the interior of the envelope, and are undesirably sorbed or adhered to the componental surfaces included therein. While a portion of these contaminants can be removed by subsequent tube processing, some of them remain as potentially troublesome deterrents to desirable performance of the repaired tube.

Accordingly, an object of the invention is to reduce the aforementioned disadvantages and to improve the operational quality of repaired evacuated electron tubes.

: A further object is the provision of an improved method utilized in the repairing of evacuated cathode ray tubes, and improved means to prevent internal comtamination during the repairing procedure.

The foregoing objects are achieved in one aspect of the invention by the provision of a method and means for initially opening an evacuated cathod ray tube for repair purposes. The tube is positioned vertically with the protruding seal portion oriented within a hermetic chamber which is evacuated of the environmental atmosphere therein. The seal of the tube is then opened in the vacuum of the chamber, whereupon an inert noncontaminating atmosphere is gradually admitted into the chamber and into the opened tube as a gaseous fill to prevent a subsequent inflow of contaminants into the opened envelope.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claim-s in connection with the accompanying drawings in which:

FIGURE 1 is a vertical sectional view illustrating the apparatus used in practicing the method of the invention; and

FIGURE 2 is a diagrammatic flow chart showing the steps of the improved method utilized in tube repairing.

By way of example, the invention will be described in this specification with reference to the repairing of a cathode ray tube, but such description is not to be considered as limiting as both the method and apparatus are equally applicable to the repair of other types of evacuated electron tubes.

With reference to the figures, there is shown a partial portrayal of a cathode ray tube 11 having a glass neck portion 13 with an attached terminal closure portion 15. It is intended that this neck portion be substantially free of external contaminants. Projecting externally from the closure is an evacuation seal or tip 17 and an array of metallic pins 19, of which only two are shown to promote clarity in the drawing. Within the neck of the tube, and electrically connected to the metallic pins extending thereinto, is an electron generating means or gun, not shown.

The tube opening device 21, vertically mounted on support means or table 22 as shown in FIGURE 1, has a body portion 23 wherein there is formed an elongated duo-diameter chamber 24. The upper part 25 of the chamber is dimensioned to accommodate the cathode ray tube neck portion 13 which is positioned therein in a spaced manner with the tube terminal closure portion 15 peripherally seated on the ledge 27 which has at least one radial groove 26 therein. By this positioning, the array of pins 19 and the evacuation seal 17 extend into the lower part 28 of the chamber with the pin array and wall of the chamber effecting transverse orientation. The funnel portion of the tube, not shown, is held and oriented by support means to relieve undue stress upon the neck portion.

A top closure cap 29 has an aperture 31 therein and an associated O-ring arrangement 33 compatible with the neck of the tube. Since the cap has threaded engagement 31 with the body portion, tightening of the cap effects a hermetic seal between the neck of the tube and the upper part of the device chamber.

Integral with the device is one type of seal opening means 35 in the form of a fluid operated piston 37 dimensioned to be hermetically slidable within cylinder 38 thus defining inner and outer cylinder chambers 39 and 40 respectively. Attached to the piston is a substantially pointed plunger 41 which movably extends in a nonhermetic relationship into a compatible guiding bushing 43 in the wall of the device adjacent the tube evacuation seal 17. This bushing, upon movement of the piston toward the device, enables the pointed end of the plunger to advance into the lower part of the chamber 28 to make impact with and break the tube evacuation seal, an operation which will be more fully described later in this specification. Also associated with the piston is a rotatable stem portion 45 having a terminal disc 47 movably retained in a piston-well by an apertured plate 49 attached to the outer face of the piston. Outward therefrom, the stem contains a short threaded portion 51 movably oriented within a related threaded aperture in the non-hermetic cylinder closure member 53. Externally of the closure member, the stem has a shaft portion 55 free of threads and a terminal wheel 57 to facilitate manual rotation thereof.

The lower part 28 of the device chamber has a removable foraminous insert 59 formed as a metallic screen basket which is supported by the bottom chamber closure cap 61. This cap makes threaded engagement with the device and effects a bottom hermetic seal 63 for the chamber.

To evacuate the duo-diameter chamber 24, a vacuum system 64, comprising of valving V, gauging G and pumping P means, is hermetically attached to an opening 65 extending through the wall of device into the lower part chamber 28.

In order to admit the inert non-contaminating gas into the duo-diameter chamber, a gas supply system 67 with appropriate valving V and gauging G means is hermetically connected to a suitable opening 69 traversing the wall of the device into the upper chamber 25.

The steps of the improved method utilized in repairing a defective tube are shown in FIGURE 2. As previously described, the tube is supported in a vertical manner with the neck thereof in a downward position whereby that portion of the neck containing the seal is oriented within the chamber 24 of the tube opening device. It is predetermined that none of the pins 19 will interfere with the movement of the plunger 41 during its subsequent movement into the lower chamber. Tightening of the top closure cap 29 produces a hermetic seal around the neck of the tube. The plunger 41 is in a withdrawn position, as shown in FIGURE 1, being so retained by the mating of the stem threads 51 in the cylinder closure member 53. With valving means V and V being closed and the bottom chamber closure cap being tightened, the duo-diameter chamber 24 is hermetically sealed with the tube evacuation seal properly oriented therein.

The vacuum system 64 is activated whereupon valving means V is opened to evacuate the environmental atmosphere contained within the chamber of the device and the inner cylinder chamber 39. This includes the atmosphere existing in the space 71 between the neck of the tube and the wall of the upper chamber which is evacuated via grooves 26. When the gauge G in the evacuation system indicates that the degree of vacuum in the device chamber is substantially of the level of that contained within the tube, the valving V of the evacuation system may be closed and wheel 57 of the tube opening means 35 rotated to move the threaded portion of the stem 51 into the outer cylinder chamber 40. This slight adjustment of the stem removes the restraint on the piston 37. Since the atmospheric pressure in the outer cylinder chamber 40 is much greater than the pressure in the evacuated inner cylinder chamber 39, the piston is propelled inward by the existing differential in fluid pressures. Thus, the plunger 41 is impelled to enter the lower chamber and strike the evacuation tip 17 with sufficient impact to break the seal which falls away from the point of attachment and is deposited in the retaining basket 59 which provides trapping and non-interfering containment means for the broken seal portions. If desired, the pumping of the vacuum system may be continued during the tube opening step after which it is closed. It is to be noted that the forward travel of the plunger has culminate arrestment in the form of a non-porous resilient buffer 42 attached thereto, which makes contact with the end wall of the cylinder chamber. If desired, other means for breaking the tube seal tip, such as mechanical or solenoid plunger activations, can be utilized in place of the aforedescribed fluid differential pressure means.

Since the vacuum within the opened tube and that within the evacuated chamber 24 is substantially similar, there is no gaseous inrush. Additional factors are also of importance, namely, the tube seal is opened in a comparatively small volumetric confinement which is evacuated or cleaned prior to the opening of each tube seal. Thus, the possibility of contaminating particles remaining within the chamber is reduced to a minimum.

The valving V of the gas supply system 67 is opened in a manner to allow a gradual gaseous inflow into the upper chamber space 71 of a dry inert non-contaminating gas such as nitrogen, neon, argon, helium, or similar gases or mixtures thereof. Admittance of the gas into the restricted space 71 of the upper chamber and the gaseous flow therefrom through the plurality of radial grooves 26 into the lower chamber 28 provides a desirable baflling effect for the inflow of gas into the opened tube. The fill of inert gas is continued until the gas gauge G indicates that the pressure within the chamber and the opened tube at least equals, and preferably slightly exceeds, the pressure of the external atmosphere whereupon gas supply valving V is closed. The higher gaseous pressure within the chamber of the device expands the inner cylinder chamber 39 thereby pushing the piston 37 outward and effecting retraction of the plunger into the guide bushing 43. Turning of the wheel 57 again mates the stem threads 51 with those of the cylinder closure member 53 thereby restraining further piston movement.

Top closure cap 29 is loosened which opens the O-ring seal and permits removal of the gas filled tube from the device. As previously mentioned, subsequent steps in the tube repair operation comprise removing the end neck portion of the tube wherein the electron gun is located, joining a new neck portion thereto and sealing a new gun thereintothese operations being consummated -while the tube has the inert gaseous atmosphere confined therein.

It has been found that the tube repair procedure of opening the evacuated tube in a vacuum and backfilling with a dry inert gas in a controlled manner has produced subsequently repaired tubes exhibiting markedly improved operational quality. The improved method for opening the tube prevents internal contamination during that critical procedure when the tube vacuum is disturbed.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

What is claimed is: v

1. In a method utilized for repairing an evacuated electron tube having a glass envelope with a seal portion projecting therefrom wherein the evacuated envelope is initially opened, a defective component replaced by one of desired quality and the tube re-evacuated and sealed, an improvement in the method of initially opening the evacuated tube comprising the steps of:

positioning said tube in support means with said seal portion oriented within a hermetic chamber; evacuating said chamber of the environmental atmosphere therein;

opening said seal of said tube in the substantially ambient vacuum of said chamber; and

admitting an inert non-contaminating atmosphere into said chamber and into said opened tube as a gaseous fill to prevent a subsequent inflow of contaminants into said open envelope.

2. The method according to claim 1 wherein said electron tube is a cathode ray tube whereof the envelope has a neck portion with said seal portion substantially terminally oriented therein, said tube being predeterminately supported in a substantially vertical manner by envelope support means with said neck in a downward position, that portion of said neck containing said seal being positioned within said hermetic chamber.

3. The method according to claim 1 wherein said inert non-contaminating atmosphere is a dry .gas admitted into said chamber in a gradual manner to prevent the conveyance of contaminating particles into said opened tube.

4. The method according to claim 1 wherein said evacuation of said chamber is of a degree at least substantially approaching the level of vacuum contained within said evacuated tube.

5. The method according to claim 1 wherein said tube is opened without the use of heat and wherein said opening of said seal is effected by impact in a manner to allow said seal portion to fall away from the point of attachment.

6. The method according to claim 1 wherein said gaseous fill of said inert non-contaminating atmosphere is of a pressure at least equalling that of said environmental atmosphere.

7. A device utilized in opening an evacuated electron tube having an envelope with a seal portion projecting therefrom, said device comprising:

a chamber having a plurality of controlled openings therein;

means for positioning said tube to orient said seal portion within said chamber;

means for 'etfecting hermetic closure of said chamber;

means for substantially evacuating said chamber of the environmental atmosphere contained therein;

means for opening said seal of said evacuated tube to the substantially ambient vacuum within said chamber; means for trapping said broken seal portions to provide non-interfering containment thereof; and

means for admitting an inert non-contaminating atmosphere in a predetermined manner into said chamber and into said opened tube as a gaseous fill to prevent a subsequent inflow of gaseous contaminants into said open envelope.

8. The device according to claim 7 wherein said electron tube is a cathode ray tube whereof the envelope has a neck portion with said seal portion substantially terminally oriented therein, and wherein said tube positioning means is formed to afford envelope support to the tube with the neck thereof in a downward position to eifect the orientation of a portion of said neck and said seal within said hermetic chamber, said neck portion being substantially spaced from the Wall of said chamber.

9. The device according to claim 7 wherein said means for opening said seal is in the form of an impacting plunger activated by a differential in fluid pressure.

10. The device according to claim 9 wherein said differential in fluid pressure is effected by said chamber evacuation means.

11. The device according to claim 8 wherein said means for predeterminately admitting said inert atmosphere into said chamber is oriented to introduce said gaseous fill into said space between said chamber wall and said neck portion, said gas being introduced by said means at a predetermined rate against said neck to provide a baffling effect from whence said gas flows throughout said chamber and into said open tube.

References Cited UNITED STATES PATENTS 3,063,777 11/1962 Trax 3162 2,455,317 11/ 1948 Schneider 316-1 1,920,528 8/1933 Butler 3162 RICHARD H. EANES, JR., Primary Examiner.

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