US3746419A

US3746419A - Method and apparatus for rebuilding television picture tubes

Info

Publication number: US3746419A
Authority: US
Inventors: H Hill
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-07
Filing date: 1971-09-07
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17

Abstract

A vacuum pump evacuated chamber supports a cathode-ray television picture tube and is sealed around the neck thereof. Manually operated control means projecting into the vacuum chamber through an end wall thereof removes the previously cut off portion of the television tube neck containing the electron gun, positions a new electron gun in place, bombards the cathode, reseals the televison tube neck and ages the rebuilt tube.

Description

United States Patent [191 Hill 1 1 July 17, I973 1 METHOD AND APPARATUS FOR REBUILDING TELEVISION PICTURE TUBES [75] Inventor: Homer E. Hill, Duncan, Okla.

173] Assignee: Marvin R. Morgan, Duncan, Okla.

a part interest l22| Filed: Sept. 7, I97] l2l| Appl. No.: 178,236

I52] U.S. Cl. 316/2, 316/28 [51] Int. Cl. HOlj 9/50 [581 Field of Search 316/1, 2, 27, 28, 316/31; 313/64 [56] References Cited UNITED STATES PATENTS 1 3,063,777 11/1962 Trax 316/2 3,404,933 10/1968 Weideman 316/2 Primary Examiner-Charles W. Lanham Assistant Examiner-J. W. Davie Attorney-Robert K. Rhea 1 1 ABSTRACT A vacuum pump evacuated chamber supports a cathode-ray television picture tube and is sealed around the neck thereof. Manually operated control means projecting into the vacuum chamber through an end wall thereof removes the previously cut off portion of the television tube neck containing the electron gun, positions a new electron gun in place, bombards the cathode, reseals the televison tube neck and ages the rebuilt tube.

4 Claims, 5 Drawing Figures METHOD AND APPARATUS FOR REBUILDING TELEVISION PICTURE TUBES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to television tubes and more particularly to a method and apparatus for replacing the electron gun of a television cathode-ray tube.

2. Description of the Prior Art When the cathode and grid apparatus of a television tube, commonly called a gun, burns out or the electron emission degenerates to a value below that required for producing an acceptable image on a viewing plant, it is conventional to rebuild the television tube by replacing that portion of the television tube neck containing the electron gun. Assuming the tube has been removed from the receiving set and cleaned, this is presently accomplished by cutting the free end portion of the neck of the tube, containing the gun, at a selected circumferential position, the location of the cut depending upon the components or type of gun being used.

Cleaning the tube includes removal of the epoxy coating bonded to its surface. The tube neck out comprises forming a circumferential crack" and its purpose is to release the vacuum within the tube which usually requires a time duration of several hours to avoid implosion of the tube or other damage, such as damaging the coating on the inner surface of the tube. After pressure, within the tube, is equal to that of the ambient air, that portion of the tube neck containing the gun, is removed at its previously cut position and a new gun, surrounded by a tube neck portion, is coaxially aligned with the television tube neck and heat sealed in place. The entire tube, after removing the epoxy bond, is then positioned within an exhaust oven connected with vacuum pumps for evacuating the tube and also heating the entire tube to approximately 350 Centigrade to stress relieve the glass. While the tube is still in the oven an under vacuum the cathode of the new gun, sealed into the tube, is converted by a heat induction machine, commonly called a bombarder, which heats the cathode of the new gun. The small tipoff end of the repaired neck is sealed while the tube is under vacuum. The tube and oven are allowed to cool which must be done gradually in order to prevent breakage. After the tube has been allowed to cool and is removed from the oven, the new connector base is mounted, on the free end of the tube for connection I with the television receiver components. The tube is aged by an AC transformer using a desired voltage ranging from zero to 30 volts, depending upon the type of gun used. After aging, the repaired tube is "sparked" with a transformer for. purifying the tube. Thereafter a peripheral portion of the tube is coated with graphite paint coating commonly called dag."

The above conventional method of rebuilding television tubes is generally satisfactory but has a number of disadvantages, such as the cost of the ovens for heating and cooling the tubes which, with the time element involved, usually requires a number of such ovens in order to simultaneously process a succession of tubes being repaired and the resultant space required for the various ovens and means for moving the tubes into and out of the ovens such as a conveyor means which is sometimes used. Further, the present method frequently results in breakage during the baking and curing steps usually caused by inadvertently permitting a blast of cool air to strike the hot tube.

This invention eliminates the necessity of removing the epoxy bond and the equipment presently required, such as the ovens, for baking the repaired tubes and eliminates the time presently required for releasing the vacuum before the tube repair work can begin. The invention provides a vacuum chamber, which supports the tube and surrounds its neck portion wherein, when the vacuum chamber is evacuated to a pressure equal to or less than that normally contained by the tube, the old gun is removed from the previously cut tube neck and replaced with a new gun while the tube is still under vacuum in the vacuum chamber, the cathode is bombarded and the tube neck sealed with that portion containing the new gun.

SUMMARY OF THE INVENTION An upright generally cylindrical vacuum chamber, having a transparent wall, a bottom forming a pump plate and a centrally apertured top plate forms a television tube neck receiving support. A mechanical vacuum pump and diffusion pump, are connected with the pump plate for evacuating the chamber. A T-shaped rack is rotatably mounted within the chamber and its stem extends through the pump plate so that the cross bar of the neck supporting prong receiving sockets, at its respective ends, may respectively support a new gun and its surrounding neck portion at one end and be connected, by the socket at its other end, with the television neck to be removed by manually operating the rack by its stem portion. Post supported adjustable jacks, positioned within the vacuum chamber in off-set relation with respect to the television tube neck, support anelectrical resistance element and cathode bombardment tube both surrounding the television tube neck. The jacks are vertically adjusted by control rods projecting through the pump plate. Transformers are connected by cables and wiring to the electric resistance element and one socket of the rack through the pump plate. The tubing of the bombarder is also connected through the pump plate. The neck of the television tube is cut or cracked at a selected location and inserted through the top plate aperture and through the bombarder tubing and electric resistance element. Before placing the tube in position, a new gun having a previously sealed tip-off" tip is manually positioned on the wiring connected rack socket. The pumps are operated to achieve the desired vacuum within the vacuum chamber and the rack is manually operated to remove the old gun and the cut-off? tube neck portion, rotate the new gun into the proper position and partially insert it into the remaining tube neck portion. Thereafter the bombarder means is positioned and operated to heat the cathode. The electrical resistance element is positioned to fuse the tube neck cut end surfaces together and the tube is aged by applying voltage to the gun through the connected socket.

The vacuum in the vacuum chamber is then dissipated and the repaired tube is removed from the vacuum chamber and dag applied to the tube to complete the operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic and a vertical ersssectional view, partially in elevation, of the device in operative position;

FIG. 2 is a horizontal cross-sectional view taken substantially along the line 22 of FIG. 1;

DESCRIPTION OF THE PREFERRED EMBODIMENT Like characters of reference designate like parts in those figures of the drawings in which they occur.

In the drawings:

The reference numeral indicates a generally cylindrical vacuum chamber supported by a frame 12 and supporting a television tube 14. The television tube 14 is conventional having an image viewing plane or end surface 16 and a generally cylindrical neck portion 18 provided with an electron gun including a cathode and grid apparatus commonly called and herein after referred to'as a gun." Similarly the cathode-ray television tube is hereinafter referred to as tube.

As mentioned hereinabove, when the gun burns out or its electron emission and beam degenerates, to a level below that required for acceptable operation of the tube, the gun is replaced by cutting off the neck 18 of the tube at a selected position intermediate its ends and replacing it with a similarly sized section of tube neck containing a new gun, such as is diagrammatically illustrated in FIG. 3. The vacuum chamber 10 comprises a transparent wall 20 having a pump plate 22 underlying one end of the wall and a top plate 24 overlying its other end and defining a vacuum chamber 25. The pump plate and top plate are each provided with a concentric groove which receives resilient packing 26 to form a seal between the plates and the end surfaces of the wall 20. The top plate 24 is centrally apertured, as at 26, for admitting the tube neck and supporting the tube 14 with its end surface 16 disposed upwardly. A ring of resilient sealing material 28, is interposed between the tube 14 and surface defining the aperture 26, for the reasons presently apparent. The sealing means 28 may comprise a conventional socket and clamp arrangement, not shown, such as is used with the above mentioned evacuated chamber and oven, if desired.

The frame 12 comprises a base portion 30 resting on a suitable horizontal support, such as a floor, indicated by the line 32, and includes upright supports 34 interconnected by horizontal members 36 which support the vacuum chamber [0. Obviously the frame may be of any desired overall dimensions for supporting the vacuum chamber at a working height or the vacuum chamber may be supported above the frame by other support members, not shown, extending between the top members 36 and the frame and pump plate 22. The pump plate 22 is centrally provided with a depending nipple 38, or the like, for communication with the vacuum chamber. A conventional diffusion pump 40 is connected to the depending end of the nipple 38 and in turn is connected by tubing 42 to a conventional mechanical vacuum pump 44, belt driven by a motor 46 I and supported by the frame base 30. The diffusion pump 40, mechanical pump 44 and other conventional components named hereinbelow may be obtained from Central Scientific Company, 2600 So. Costner Avenue, Chicago, Ill. 60623, the model of each being chosen for a desired rate of evacuation.

A T-shaped rack 48 has its horizontally disposed top bar 50 positioned within the chamber 25 by its hollow stem 52 extending downwardly through the pump plate 22 and sealed therewith by a conventional push-pull rotary feed-thru unit 54 permitting rotative and linear movement of the stem 52 by means ofa manually operated control wheel 56 secured to the depending end of the stem 52. The bar 50 has, secured thereto, on its upper surface adjacent its respective ends, a pair of

female sockets

58 and 60 for cooperatively receiving the outwardly projecting prongs connected with the components of the tube gun and supported by a base 62 at the free end of the tube neck 18. The spacing between the vertical axis of the stem 52 and center of each

socket

58 and 60 is equal to the spacing between the vertical axis of the stem 52 and vertical axis of the top plate opening 26 and longitudinal axis of the tube neck 18 when positioned in the chamber for the purposes readily apparent.

Wiring, connected wijth a transformer T in turn connected with a source of alternating current, extends through the hollow stem 52 and is sealed therewith vac uum tight in' a conventional manner and is connected with the socket 60. Prior to placement of the tube 14 on the vacuum chamber 10, the tube neck 18 is cut in a conventional manner and a new gun 64 which, as diagrammatically illustrated in FIG. 3, has its tip end portion 66 sealed and provided with a prong equipped base 68, is positioned on the rack socket 60 with the upwardly disposed end portions of the gun guide arms 69 projecting above the upper limit of the gun surrounding glass envelope.

The tube neck 18 is cut by placing an electrical resistant wire or element circumferentially around the neck 18 and applying electrical potential to the wire wherein the heat generated thereby results in forming a circumferential crack or cut in the glass.

A first support jack 70 is positioned within the vacuum chamber 25 in off-set relation with respect to the neck 18. The jack 70 comprises a pair of upright standards or posts 72, each provided with a V-shaped groove 74 on one longitudinal surface which cooperatively receive, in vertical sliding relation, a cross beam 76, having cooperating V-shaped end surfaces 78. A control rod extends vertically upward and through the pump plate 22 through a suitable vacuum sealing conventional feed-thru unit 82 and is threadedly engaged at its upper end portion with the cross beam 76. A manually operated hand wheel 84, secured to the depending end of the control rod 80, rotates the control rod and raises and lowers the beam 76. A pair of arnis 86 project outwardly from the beam 76 in parallel spaced relation toward the tube neck 18 and support a metallic rod 88 having a relatively high temperature melting point, such as tungsten, which is formed intermediate its ends to define a circular loop 90 closely surrounding a peripheral portion of the tube neck 18 for fusing cut ends of the neck together as presently explained. The respective ends of the rod 88 are connected by cables 92 extending through conventional electrical feed-thru connectors 93 on the pump plate and connected to a high amperage transformer T2 in turn connected with a source of electrical energy AC.

A second similarly constructed supporting jack 94 is positioned within the vacuum chamber 25 in off-set relation with respect to the jack 70 and tube neck 18. The second jack 94 similarly includes a pair of posts 93 supported by the pump plate 22 but electrically insulated therefrom by insulators 95. These posts similarly support a two-part cross beam 96 vertically movable by a similarly connected control rod 98 threadedly extending through a cross beam insulating connector 97. A handle wheel 100 is connected with the depending end of the rod 98. A pair of arms 102 are connected with the respective ends of the cross beam 96 and have respectively secured thereto, as by set screws 99, tubing 104 connected with a bombarderl06 positioned outwardly of the vacuum chamber. The tubing 104 forms a coil or loop 109 closely surrounding the tube neck 18. The bombarder is conventional and is assembled from conventional components including a transformer, coils and a power tube to produce a desired plate circuit and RF current. The two runs of tubing 107 from the bombarder extends through and is sealed with the pump plate 22. The two ends of the tubing 107, entering the pump plate are connected with the jack posts 93 through the insulators 95.

OPERATION In operation the tube neck 18 is cut in a conventional manner at a selected position intermediate its ends. The tube 14 is then positioned on the vacuum chamber top plate 24 with the new gun 64 in place on the socket 60. The tube neck 18 is surrounded by the electrical resistance rod 88 and the loop 109 of the tubing 104. The ditfusion pump 40 and the mechanical pump 44 are operated to evacuate the chamber 25 to a desired pressure measured by a guage 110 communicating with the chamber 25 through a conventional suitable feedtht'u" connection secured to the top plate 24. When the desired vacuum, within' the chamber 25, has been achieved, as measured by the gauge 110, in millitorrs or terms of microns of Hg, the rack socket 58 is engaged with the pins of the plug 62 on the free end of the tube neck 18. The cut off portion of the tube neck, containing the gun to be replaced, is removed from the tube by lowering the rack bar 50 and rotating the bar 50 180 to align the longitudinal axis of the new gun 64 with the axis of the tube neck 18. The guide fingers 69 are then inserted into the opening of the tube neck 18 until the end surface of the envelope containing the new gun contacts the tube 18 at its severed end surface.

The cathode of the new gun is then converted, in a conventional manner, achieved by positioning the jack beam 96 so that the coil [09 of the tubing 104 is adjacent the position of the cathode of the new gun. The bombarder unit 106 is then operated to heat the cathode. The resistance element rod 88 is then positioned around the mating surfaces of the new gun surrounding envelope and end surface of the cut off tube neck 18, by operating the jack 70, and high amperage current is applied to the element 88 from the transformer T2 to heat the adjacent surfaces of the glass to a fusion temperature which, when fused, is allowed to cool. The tube is then aged by the transfrmer T by applying voltage to the components of the gun by the wires from the dissipated by a conventional vacuum bleed valve 112.

transformer T. The vacuum within the chamber 25 is When the pressure in thechamber 25 is equal to atmospheric pressure, the tube 14 is removed and an external coating or dag is applied to a selected portion of its periphery as is conventional. After aging, the tube is sparked with high voltage current as is conventional.

Obviously the invention is susceptible to changes or alterations without defeatingits practicability, there fore, I do not wish to be confined to the preferred embodiment shown in the drawings and described herein.

1 claim: 1. A television cathode-gun tube repair apparatus, comprising:

a container having a transparent side wall and opposing end walls forming a chamber, one said end wall having an opening dimensioned for removably receiving the neck portion of a television tube in supporting relation; means supported by said one end wall surrounding and sealing a peripheral portion of the television tube with said one end wall; pump means connected with the other said end wall for evacuating the chamber; rack means within the chamber,

said rack means being movable toward and away from the end portion of the television tube neck within the chamber, for removing and replacing a cut-off portion of the television tube neck; jack means within the chamber, i

said jack means being movable in a direction parallel with the longitudinal axis of the television tube neck for disposing the upper end portion of the jack means in a selected horizontal plane intermediate the length of a television tube neck;

and,

energy transfer means connected with a source of energy and supported by said jack means in surrounding relation with respect to the television tube neck for forming a fusion joint at the cut-off position of the television tube neck and heating its contained components.

2. The repair apparatus according to claim 1 in which said rack means includes:

a T-shaped rack having a stem portion rotatably and longitudinally slidably projecting through one said end wall in laterally off-set relation with respect to the longitudinal axis of a television tube neck within the chamber, said rack having a cross-bar,

the longitudinal axis of said cross-bar being normal to the longitudinal axis of a television tube neck within the chamber; and,

at least one prong receiving socket secured to said cross-bar coaxial with a television tube neck within the chamber.

3. The repair apparatus according to claim 2 in which said jack means includes:

a pair of spaced-apart parallel posts secured to one said end wall within the chamber in laterally off-set parallel relation with respect to the longitudinal axis of a television tube within the chamber;

a cross-beam extending between and slidably connected, at its respective ends, with said posts; and,

a control rod rotatably projecting through said one end wall and threadedly connected with said crossbeam.

4. The method of repairing a television tube having a neck portion containing a cathode-gun, comprising:

bombarding the replacement cathode-gun with an RF current;

surrounding said abutted end surfaces with an electrical resistance element;

heat sealing said abutted end surfaces;

admitting atmospheric pressure to the evacuated container;

removing the neck portion of said television tube from said container;

purifying the evacuated interior of the television tube by applying a high voltage current to said replacement cathode-gun; and, applying a graphite coating to an exterior portion of said television tube.

Claims

1. A television cathode-gun tube repair apparatus, comprising: a container having a transparent side wall and opposing end walls forming a chamber, one said end wall having an opening dimensioned for removably receiving the neck portion of a television tube in supporting relation; means supported by said one end wall surrounding and sealing a peripheral portion of the television tube with said one end wall; pump means connected with the other said end wall for evacuating the chamber; rack means within the chamber, said rack means being movable toward and away from the end portion of the television tube neck within the chamber, for removing and replacing a cut-off portion of the television tube neck; jack means within the chamber, said jack means being movable in a direction parallel with the longitudinal axis of the television tube neck for disposing the upper end portion of the jack means in a selected horizontal plane intermediate the length of a television tube neck; and, energy transfer means connected with a source of energy and supported by said jack means in surrounding relation with respect to the television tube neck for forming a fusion joint at the cut-off position of the television tube neck and heating its contained components.

2. The repair apparatus according to claim 1 in which said rack means includes: a T-shaped rack having a stem portion rotatably and longitudinally slidably projecting through one said end wall in laterally off-set relation with respect to the longitudinal axis of a television tube neck within the chamber, said rack having a cross-bar, the longitudinal axis of said cross-baR being normal to the longitudinal axis of a television tube neck within the chamber; and, at least one prong receiving socket secured to said cross-bar coaxial with a television tube neck within the chamber.

3. The repair apparatus according to claim 2 in which said jack means includes: a pair of spaced-apart parallel posts secured to one said end wall within the chamber in laterally off-set parallel relation with respect to the longitudinal axis of a television tube within the chamber; a cross-beam extending between and slidably connected, at its respective ends, with said posts; and, a control rod rotatably projecting through said one end wall and threadedly connected with said cross-beam.

4. The method of repairing a television tube having a neck portion containing a cathode-gun, comprising: providing a closed container; placing a replacement cathode-gun within the container; cutting the neck of the television tube; inserting and sealing the neck of the television tube within said container; evacuating the container; removing the cut neck portion of said tube; coaxially aligning said replacement cathode-gun with the cut-off end of said tube neck in end-to-end surface abutting relation; aging the replacement cathode-gun by applying an electrical current to the replacement cathode-gun; bombarding the replacement cathode-gun with an RF current; surrounding said abutted end surfaces with an electrical resistance element; heat sealing said abutted end surfaces; admitting atmospheric pressure to the evacuated container; removing the neck portion of said television tube from said container; purifying the evacuated interior of the television tube by applying a high voltage current to said replacement cathode-gun; and, applying a graphite coating to an exterior portion of said television tube.