US3913194A

US3913194A - Method of assembling cathode ray tubes

Info

Publication number: US3913194A
Application number: US447774A
Authority: US
Inventors: Anthony Victor Devere Krause
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-03-02
Filing date: 1974-03-04
Publication date: 1975-10-21
Anticipated expiration: 1992-10-21
Also published as: CA1001706A; GB1442804A; DE2410436A1

Abstract

To assemble a cathode ray tube having a plurality of electrodes forming the electrode gun, the electrodes, which in the finished tube are supported by wires, are assembled in their correct relative dispositions on a frame by means of the wires to form a temporary assembly of the electron gun. The envelope of the tube is assembled around the gun with the wires passing through the seam of the tube which is then sealed and the frame removed. The technique is applicable to the manufacture of miniature cathode ray tubes and extends to the formation of the electrodes and grids and other sub-assemblies within the finished tube.

Description

United States Patent Krause 1 Oct. 21, 1975 I METHOD OF ASSEMBLING CATHODE RAY 3,047,759 7/1962 McNaney 3l3/480 x TUBES 3,462.629 8/1969 Bell 313/82 TS 3,598,557 8/197l Sawagata et ala, 65/155 Inventor: Anthony VICIOr DeVere Krause, 3 3,600,778 8/l97l Martin i 29725.15 x Beeehcroft, Ashtead, Surrey, 3.722044 3/l973 Law 29/2576 England [22] i Man 4 974 Primary Examiner-Roy Lake 7 Assistant Examiner-lames W. Davie [cl] Appl. No: 447,774 Attorney, Agent or Firm waters, Schwartz & Nissen Related US. Application Data [63] Continuation-impart of Ser. No. 377,778, July 9, [57] ABSTRACT 1973, Pat, No. 3,875,452, which is a continuation of i S NO 23279 March Hv 1971 abandomzd To assemble a cathode ray tube having a plurality of electrodes forming the electrode gun, the electrodes [30] Foreign Apphcafion Prior), Dam which in the finished tube are supported by wires, are Mar 2 1973 Unit d Km do 10247? assembled in their correct relative dispositions on a e g m frame by means of the wires to form a temporary as- S2 sembly of the electron gun The envelope of the tube 5' 'gfi gfig is assembled around the gun with the wires passing [58] Fieid l l 25 13 through the seam of the tube which is then sealed and mp5 15 25 25 5 f 6 the frame removed The technique is applicable to the 7 manufacture of miniature cathode ray tubes and extends to the formation of the electrodes and grids and [56] UNITES S X?ES S/?FENTS other sub-assemblies within the finished tube.

2,25(L622 7/1941 Bowie 313/89 x 21 Claims Drawing Figures V l' vm US. Patent Oct.21, 1975 Sheet10f12 3,913,194

U.S. Patent Oct. 21, 1975 Sheet3of 12 3,913,194

US. Patent Oct.21,1975 Sheet4ofl2 3,913,194

US. Patent Oct. 21, 1975 Sheet50f12 3,913,194

U.S. Patent Oct. 21, 1975 Sheet6of 12 3,913,194

U.S. Patent 0a. 21, 1975 Sheet 7 of 12 US. Patent Oct.21, 1975 Sheet8of 12 3,913,194

U.S. Patent Oct.21,1975 Sheet9of 12 3,913,194

U.S. Patent Oct. 21, 1975 Sheet 10 of 12 U.S. Patent 0.1.21, 1975 Sheet 12 ofl2 3,913,194

METHOD OF ASSEMBLING CA'IIIODE RAY TUBES This application is a continuation in-part of my application Ser. No. 377,778 filed July 9, 1973, now US. Pat. No. 3,875,452, which is a continuation application of Ser. No. 123,279 filed Mar. 11, 1971, now abandoned.

This invention relates to vacuum tubes, and is particularly, although not exclusively, concerned with the manufacture of cathode ray tubes.

BACKGROUND OF THE INVENTION The development of miniature televisions, particularly those small enough to be carried in the pocket, has been retarded by a number of factors. Among these factors has been the design and manufacture of a cathode ray display tube which is of suitably small physical dimensions and which requires a low power supply for its operation, enabling the use of small and light batteries to power a portable set.

Further from the commercial point of view, the market for such televisions has been limited in view of the cost of manufacturing such a television, the cathode ray display tube contributing a significant part of that cost.

It is therefore an object of the present invention to provide a cathode ray display tube suitable for use in a television apparatus which is small in physical size, is of low power requirement, while still being cheap to manufacture.

It is to be understood however, that the tubes of the construction and method of manufacture of the invention are applicable to other applications than televi- SIOII.

SUMMARY OF THE INVENTION Accordingly, in one aspect, the present invention provides a method of assembling a cathode ray tube in which some or all of the electrodes are provided with supporting wires by which they are supported and located with respect to one another in the finished tube from the envelope wall of the tube, comprising assembling the electrodes in their correct relative disposition on a temporary support frame by means of said supporting wires to form a temporary assembly, assembling the envelope of the tube around the electrodes in two or more portions with the supporting wires passing through one or more seams between those parts, and then removing the temporary frame from the supporting wires.

Preferably, in the above method one or more groups of said electrodes are assembled together in subassemblies of electrodes, held together by temporary wires joining their respective support wires, before being assembled to said temporary support frame.

In a further aspect the invention provides a cathode ray tube assembled by the above methods and comprising an envelope and a plurality of electrodes therein forming an electron gun assembly, said envelope including two body portions joined together along a seam, the electrodes of said gun being supported and located in the envelope by means of conductor wires through which the required electrical connection is made to the respective electrode, said conductor wires passing through the seam.

In a preferred arrangement of such a cathode ray tube, the screen is formed on a face of a cup portion of the envelope which is joined to said two body portions along a further seam.

BRIEF DESCRIPTION OF THE DRAWINGS In order to promote a fuller understanding of the above, and other, aspects of the present invention, embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. I is a side elevation of a cathode ray tube,

FIG. 2 is a plan view of the tube of FIG. 1,

FIG. 3 is a face view of the tube of FIG. 1,

FIG. 4 is a schematic cross-sectional view taken on the line IV-IV of FIG. 2,

FIG. 5 is a schematic cross-sectional view taken on the line VV of FIG. 1,

FIG. 6 is a schematic cross-sectional view taken on the line VI-VI of FIG. 4,

FIG. 7 is a schematic cross-sectional view taken on the line VII-VII of FIG. 4,

FIG. 8 is a schematic cross-sectional view taken on the line VIII-VIII of FIG. 5,

FIGS. 9 and 10 show the screen potential control electrode of the tube of FIG. I,

FIGS. 11 and 12 show one of the X" deflection plates of the tube of FIG. 1,

FIGS. 13 and 14 show the interplate screen of the tube of FIG. 1,

FIGS. 15 and 16 show the Y" deflection plates of the tube of FIG. 1,

FIGS. 17 and 18 show the No. 3 anode of the tube of FIG. 1,

FIGS. 19 and 20 show the No. 2 anode of the tube of FIG. 1,

FIGS. 21 and 22 show the No. I anode of the tube of FIG. 1,

FIGS. 23 and 24 show the grid of the tube of FIG. 1,

FIG. 25 shows the assembly of the grid and filament of the tube of FIG. I,

FIG. 26 shows a typical portion of the seam of the envelope of FIG. 1,

FIG. 27 shows a schematic cross-section on the line XXVIIXXVII of FIG. 26,

FIGS. 28, 29 and 30 show the jigs for, and the assembly of, a first electrode sub-assembly,

FIGS. 31, 32 and 33 show the jigs for, and the continuation of, the first electrode sub-assembly,

FIGS. 34, 35, 36, 37, 38 and 39 show the device for filament winding attachment to the first electrode subassembly,

FIGS. 40, 41 and 42 show the jigs for, and the attachment of, the grid electrode for the first sub-assembly,

FIGS. 43, 44 and 45 show the jigs for, and the assembly of, a second electrode sub-assembly,

FIGS. 46, 47 and 48 show the jigs for, and the assembly of, a temporary electron gun assembly, and

FIGS. 49, 49A, 50 and 51 show the mandrel of the jig of FIGS. 46, 47 and 48 in more detail.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 show the external arrangement of the cathode ray tube of this embodiment.

The glass envelope of cathode ray tube is formed in three parts, as best seen in the side view of FIG. I, the parts comprising two body halves l0 and II, and a screen cup 12 having a screen end face 13. The three

body parts

10, 11 and 12 are joined together to form a complete envelope by soldering with a low melting point glass frit in a manner to be described in more detail below.

As best seen in FIGS. 4 and 5 which are crosssectional views of the cathode ray tube, the various electrodes of the electron gun of the tube which is of the electrostatic deflection type, are supported individually on a series of supporting wires, the supporting wires passing through the envelope along the seam where the two body halves l0 and I] are joined together. The supporting wires also serve for electrical connection to the respective electrodes.

The electrodes of the gun will now be described in brief detail starting from the front of the tube. The first electrode immediately behind the screen of the tube is a screen potential control electrode which is shown on an enlarged scaie in FIGS. 9 and 10. It is provided with supporting wires 21 and 22 and is positioned towards the front of the tube with the wires 21 and 22 disposed immediately behind the joint between the screen cup 12 and the two body halves l0 and 1 I. The next electrodes are the two "X"

deflection plates

23 and 24, the plate 23 being shown in more detail in FIGS. 11 and 12, each is provided with supporting

wires

25 and 26. The next electrode is the interplate screen 27 shown in more detail in FIGS. 13 and 14 and provided with supporting wires 28. The screen 27 is formed with a central slit 29 through which the electron beam may be directed from the Y plates. The next electrodes are the Y"

plates

30 and 31 shown in more detail in FIGS. 15 and 16, and provided with supporting

wires

32 and 33. The next electrode is an anode, referred to as No. 3 anode, indicated at 34 and shown in more detail in FIGS. 17 and 18. The No. 3 anode is provided with a central aperture 35 through which the electron beam may pass, and supporting wires 36. Preferably the No. 3 anode 34 and the screen 27 are connected as an assembly by means of side plates 27a as a convenience in the manufacturing assembly of the tube as discussed below.

The next electrode is an anode referred to as NO. 2 anode indicated at 37 and shown in more detail in FIGS. 19 and 20. It is to this anode that a beam focusing potential is applied to the tube when in use, and it is provided with an aperture 38 for the beam and with supporting wires 39. The next electrode is an anode referred to as No. l anode indicated at 40 which is shown in more detail in FIGS. 21 and 22 and which is provided with an aperture 41 for the beam and supporting wires 42. The cylindrical part 400 of the anode 40 is preferably formed separately from the plate part 40b, the two being welded together to form the complete anode as shown. To complete the electron gun assembly there is a grid indicated at 43 and shown in more detail in FIG. 23 and 24, and which forms an assembly with a directly heated cathode filament 44, the assembly being shown in more detail in F 1G. 25. The grid electrode 43 is provided with a central aperture 45 through which electrons emitted from the directly heated cathode 44 may pass.

The assembly of the grid 43 and filament 44 forms a rigid structure as best seen in FIG. 25, supporting Wires 46 being rigidly attached to the grid electrode 43 to support it and the assembly in the envelope of the tube. The two supporting wires 46 each have turned over portions which are welded to a cross wire 52 and two further supporting wires 47 for the filament are attached to the cross wire 52 by means of fused glass beads 53. The supporting wires 47 pass through the seam between the

envelope parts

10 and 11 at the rear end thereof and each have a turned over portion 54, the filament 44 being attached and electrically connected by welding across those portions 54.

The filament 44 is wound from a tape of nickel 205 or 222 alloy, this being an active alloy, microns wide by 2% microns thick. The filament has four turns with connecting tails extending therefrom, giving three effective loops in the middle of the filament, and is covered with an activating material containing barium, strontium carbonate and calcium to enhance the emission of electrons from the filament in known manner per se. The activating material also serves to support and hold the turns of the filament relative to one another providing a mechanically rigid unit.

The grid electrode 43 is welded to the support wires 46 being provided with depressions 50 which form attachment points to this purpose, and to space the grid from the filament, the depressions 50 may if desired be omitted however.

Thus, the grid aperture 45 and the filament 44 are correctly located and aligned, and the support wires 47 together with the filament 44 are electrically insulated from the support wires 46 and the grid electrode 43 by means of the glass beads 53.

As discussed the electrodes of the electron gun assembly are located and supported in the envelope of the tube by means of their respective support wires. This feature transfers the function of locating the various electrodes of the gun assembly relative to one another, to the actual envelope of the tube as opposed to previous constructions where this function has been performed by separate spacers and supports with the gun being arranged as a separate self supporting assembly independent of the envelope and located and sealed in the envelope at one end. This departure from previous practice enables a considerable reduction in the overall size of the envelope to accommodate a particular assembly of the electrodes with a consequent reduction in the tube envelope size for a given size of picture screen.

The

portions

10, 11 and 12 of the tube envelope are joined together along their respective seams by means of a low melting point glass frit. This glass hit is preferably a devitrifiable material for example Pyroceram frit as manufactured and sold by the Coming Glass Company. When Pyroceram frit is used, the frit flows sufficiently during fusing, to be discussed later, to flow round the supporting wires and seal the wires into the seam between the envelope portions, serving them both to seal and attach the supporting wires to the envelope. When other glass frits are used, in some cases the flow during fusing is not sufficient and in order to ensure complete encirclement and sealing on the wires, grooves 60 are provided (as seen in FIGS. 26 and 27) in the

body portions

10 and 11 at appropriate points to receive the supporting wires for the electrodes where they pass through the seam between them; and the glass frit indicated generally at 61 in those Figures, apart from serving to join and seal the envelope portions together, also serves to attach and seal the supporting wires to the envelope seam and portions.

The preferred method of assembly for the above tube will now be described in some detail. As initial steps two sub-assemblies of electrodes are prepared before the assembly of the electron gun. The first subassembly includes the grid electrode 43 and filament 44 and their respective supporting

wires

46 and 47. The second sub-assembly comprises the No. 1 anode 40, the No. 2 anode 37, the No. 3 anode 34, and the interplate screen 27, together with their respective supporting wires. The second sub-assembly is in a sense a temporary sub-assembly as will be seen from the later discussion.

The stages by which the first assembly of grid and filament referred to above, is made will be described with reference to FIGS. 25, 28, 29 and 30. The two supporting wires 47, each with their turned-over end portion 54 are provided with a small glass head 70 around the corner between the body of the wire and the turned over portion 54. The two support wires 47 carrying such glass beads are positioned in a jig indicated at 71 with the portions 54 facing towards one another in their correct dispositions. The wire 52 in the form of a length of wire 72 provided with two glass beads 73 appropriately placed along it to lie adjacent beads 70 when the wire is placed on top of the jig 71 is so placed on the jig. The jig 71 is provided with a shaft 74 which is rotatable by a handle 75 and which carries two spring fittings 76 arranged to grip and hold the wire 72 in a groove provided in blocks on the jig, and which also carries two spring fingers 77 arranged to engage with the outer ends of the wires 47 to hold them firmly in position in the jig. When the wires 47 and the wire 72 are correctly positioned and held in the jig by rotation of the shaft 74, heat is applied to the

adjacent glass beads

70 and 73 to fuse them together to form the beads 53 so that on cooling a rigid assembly is formed between wires 47 and the length of wire 72. The location of the length of wire 72 relative to the wires 47 in the jig ensures that on fusing the glass beads there is glass between the length of wire 72 and the wires 47 so that they are electrically insulated relative to one another. The formation of the wire 52 from the length of wire 72 is completed by cropping off the excess length on either side of the beads 53 so formed.

The next stage in producing the first sub-assembly is to add the grid supporting wires 46. These are placed in a jig with their turned over portions 55 correctly aligned, together with the assembly of the wire 52 and the supporting wires 46 formed as above, as best seen in FIGS. 31, 32 and 33, and the turned over portions 55 are then resistance welded to the ends of the wire 52, the resistance welding electrode being indicated typically at 78.

The assembly of the supporting wires 47 and the supporting wires 46 formed as above is then positioned in a jig carried in a filament winding device illustrated in FIGS. 34, 35 and 36. The jig is in the form of a slidable carriage 80 and is arranged to receive the wires 47 and locate the assembly with the wires 46 upwards and laying in a horizontal disposition along the line 81 at an angle to the direction of sliding of the carriage 80. The carriage is slidable between the loading position towards the right of the device and a coil winding position at which it is shown in FIG. 34, towards the left of the device.

At the coil winding position there is provided a rotatable mandrel 82 with an associated crank pin 83 disposed to lie alongside the mandrel 82. The mandrel 82 is rotatable in the device by means of a knurled hand wheel 85. The filament tape is supplied in the form of straight annealed lengths and a tape feed mechanism carried on a shaft 84 is provided on the device and positioned on the shaft 84 so as to feed and tension the filament tape during winding of it from the storage reel onto the mandrel 82.

The feed device is shown in more detail in FIGS. 37, 38 and 39 and indicated generally in these Figures at 85. The feed device comprises a channelled tape guide 86 mounted at the desired helix angle of the filament winding on a block 87 which is in turn rotatably carried on the shaft 84, the guide 86 being sufficiently long to accommodate a length of the tape as supplied. Associated with the tape guide 86 are a pressure pad 88 and a final feed guide 89 formed from round cross-section wire. The arrangement of the guide 86, the pad 88 and final guide 89 is such that the filament tape is tensioned and guided onto the mandrel 82.

To wind a filament, the mandrel 82 is angularly positioned so that the crank pin 83 is in a horizontal position, as shown in FIG. 37, and the filament tape is laid across the top of the mandrel 82 and the free end resistance welded to the crank pin 83. The mandrel 82 is then rotated (anti-clockwise) so that the filament tape is drawn from the feed device across the top of the mandrel 82 and wound around the mandrel, the angle at which the tape guide 86 is set being appropriate to the desired helix angle of the filament as mentioned above and to give the desired spacing between the turns in the finished filament. The flexibility of the filament tape between its location in the feed device 85 and its contact with mandrel 82, is such that it accommodates for the effective axial feed of the tape along the mandrel 82 which occurs automatically during winding as a result of the angle of feed. The feed device 85 is axially adjustable by a small amount to take up any excessive axial displacement during winding, the operation of winding being preferably observed through a microscope.

When the required number of turns has been wound on the mandrel the carriage 80 with a supporting wire assembly located therein is moved from the loading position into position beneath the mandrel 82, the crank pin 83 being again positioned in the horizontal position for this operation. It is arranged that the length of filament tape extending from the crank pin 83 to that wound on the mandrel 82 and the length of tape extending from the mandrel 82 to the feed device 85, lie repectively over the portions 54 of the support wires 47 carried in the carriage 80. These portions of the filament tape are then resistance welded to the portions 54 and the thus formed and welded filament is severed from the tape attached to the crank pin 83 and extending from the tape feed device 85. The mandrel 82 is then withdrawn axially from the wound filament to leave it freely supported between the portions 54. As a final step in the completion of the filament the activating material mentioned above is applied as a droplet of the constituents with a cellulose binder in a volatile solvent such as amyl acetate.

The next step in manufacturing the first sub-assembly comprises the addition of the grid electrode 43. To facilitate this the grid electrode is placed on a locating block indicated at 90 in FIGS. 40, 41 and 42. The block 90 is carried at the extreme right hand end of the winding device on the horizontal bars which carry the jig 80. A pair of

fine tubes

91 and 92 are carried in a carriage indicated generally at 93 which is slidably mounted on the back of the winding device. The

pipes

91 and 92 are turned downwards at their free ends and connected to a vacuum system by way of the carriage. When a grid electrode 43 has been placed on the block 90 and accurately located therein, the

tubes

91 and 92 are lowered onto the grid electrode 43 and a vacuum applied so that the electrode is then accurately located or. and carried on the

tubes

91 and 92. The carriage 93 with the grid electrode is then brought accurately into register over the jig 80 at the winding position so that the grid electrode 43 is accurately located above the supporting wire and filament assembly already produced in the jig 80. The grid electrode 43 is then lowered and the vacuum system disconnected to deposit the grid electrode 43 accurately onto the supporting wire assembly. The grid electrode 43 is then resistance welded to the supporting wires 46 as discussed above to complete the first sub-assembly which can then be removed from the jig 80.

The second sub-assembly for the tube is produced in ajig arrangement illustrated in FIGS. 43, 44 and 45. As a first step to producing this second sub-assembly, a glass coated wire 100 is positioned in a pivotally mounted portion 102 of a jig 101. The base of the jig 101 is also provided with a fixed pin 103 and a central mandrel 104. The No. 1 anode 40 with its associated supporting wires 42 is then positioned by means of its aperture 41 on the mandrel 104 with the supporting wire on the appropriate side extending in front of the pin 103 and behind the wire 100 as seen in FIG. 43, and with the cup of the anode resting on the base plate of the jig.

A sleeve 106 which is a close fit over the mandrel 104 and in the aperture 38 of the No. 2 anode 37, is then positioned on the mandrel 104 resting in the cup portion of the No. 1 anode. A spacer disc 107 is placed over the sleeve 106 to rest on top of the No. 1 anode 40. The No. 2 anode 37 with its associated supporting wires 39 is then positioned over the sleeve 106 with one of its supporting wires 39 similarly extending in front of the glass coated wire 100.

The movable portion 102 of the jig is then swung to a fixed stop by means of the handle 105 to slightly load the glass coated wire 100 carried in it against the supporting wire 42 and the supporting wire 39, and those supporting wires against the pin 103. Heat is then applied to fuse the glass coating onto the supporting wire 42 and the supporting wire 39 thus to join the supporting wires to the wire 100. The arrangement is such that on fusing of the glass, there is still a slight gap between the supporting wires and the wire 100 resulting in a strain free join when the glass again solidifies.

After that operation has been completed, a second glass coated wire 100 is placed in the jig 101 to the left of the mandrel 104 as seen in FIG. 43, the supporting

wires

42 and 39 on that side extending in front of the second wire 100. The jig portion 102 is then moved in the opposite direction to a second fixed stop to load the left

hand supporting wires

42 and 39 against the second wire 100 and the glass thereon is again fused to join the three. Again the arrangement is such that on fusing of the glass there is a slight gap between the supporting wires and the wire 100 resulting in a strain free joint when the glass again solidifies.

The sleeve 106 is then removed and a spacer 108 positioned over the mandrel 104 to rest on top of the No. 2 anode 37. The assembly of the No. 3 anode 34 and interplate screen 27 with their respective supporting

wires

36 and 28, is then positioned over the mandrel 104 and the supporting wires 36 similarly fused to the glass coated wires on either side with strain free joints.

By this means it can be seen that the three anodes are formed together as a sub-assembly with their respective apertures accurately located to be concentric by means of the mandrel 104 and the sleeve 106, and being at the same time accurately spaced apart by means of the

spacers

107 and 108, and retained in this location by being fused to the glass coated wires 100. Since the joints are formed in strain free fashion in the jig, the accuracy of location is retained on removal from the jig.

Having made these two sub-assemblies, the electrodes of the electron gun are positioned in a jig arrangement shown in FIGS. 46, 47 and 48 for the purposes of a temporary assembly of the electrodes onto a temporary frame prior to the addition of the glass envelope portions.

The jig arrangement for this temporary assembly is arranged for the assembly for the electron gun with its axis horizontally and comprises a central mandrel indicated generally at 110 and shown in more detail in FIGS. 49, 49A, 50 and 51.

The mandrel 110 comprises a central spindle 111 which has wings 112 extending in a horizontal plane on either side of its mid portion. A block 113 adjacent the wings 112 and terminates in a second block 114 with a pair of sideplates 115 at the left hand end as seen in FIG. 46 by which the mandrel 110 is mounted on the jig base plate.

The screen potential control electrode 20 with its respective supporting wires 21, 22 is positioned over the side plates 114 to be located thereon by means of the notches 116 in correct relationship to the axis of the electron gun as defined by the axis of the mandrel spindle 111. The X" plates of the

electron gun

23 and 24 are then positioned on the mandrel 110 resting in abutment at their front end on the block 114 between the side plates 114, at a mid point on the block 113 and at the back of the wings 112. A block (not shown) is provided on the base plate to support the lower X" plate in against the mandrel 110 while the upper rests in position on top.

The second sub-assembly of Nos. 1, 2 and 3 anodes together with the interplate screen, is then fitted over the mandrel spindle 111 and the interplate screen is located by its aperture fitting over the wings 112 while the three anodes are located by the apertures of the Nos. 1 and 3 anodes being fitted over the mandrel spindle 111.

The Y"

plates

30 and 31 with their respective supporting

wires

32 and 33 are positioned and held with their front ends resting against the ends 117 of the wings 112 and their rear end resting on the mandrel spindle 111. The Y" plates are supported in this position by means of three posts 118 provided on the base of the jig, the posts 118 having notches in the top to receive and locate the thickness of the material of the plates. Apertures 119 are provided in the lower side plate 27a to allow the posts 118 to protrude into the space between the side plates 270. An additional location for the "Y" plates may be provided by the further posts on a suitable fixture (not shown) being provided to engage the tops of the plates in a similar manner with notches. In that last instance the upper side plate 27a is provided with apertures 119.

The first sub-assembly of grid and filament is then positioned in the jig with the grid aperture 45 being located on a spigot 120 formed at the rear end of the mandrel spindle 111. The assembly is held square on the spigot by means of two pegs 121 provided on the jig abutting the rear face of the grid electrode 43. in order to axially locate the anodes assembly along the mandrel a spacer of the correct thickness is then interposed between the front of the grid electrode and the rear of the No. l anode, and the anode assembly held back to the correct distance from the grid as determined by that spacer. The axial position of the grid is determined by the shoulder which forms the spigot 120 on the mandrel spindle 111.

A supporting wall 122 is provided in the jig arrangement around the mandrel the upper surface of which is arranged as a reference plane to lie just below the supporting wires of the various electrodes with a minimum clearance to afford thereby angular location for the electrodes about the mandrel. Support and location means are also provided on the jig for a temporary frame 123 which, in this embodiment, is in the form of a glass rod frame, to be held in the jig with its upper surface lying immediately below the supporting wires of the electrodes located in the jig again with a distance but minimum clearance. It can thus be seen that by means of this jig arrangement the electrodes of the gun may be accurately located with respect of one another and held in position with their supporting wires just out of contact with the temporary frame 123. The supporting wires are then all attached to the temporary frame 123 with a suitable adhesive, preferably the adhesive sold under the name lnsalute manufactured by the Sauereisen Cement Company, Pittsburgh 15, Pennsylvania, United States of America. The important criteria for the adhesive, apart from it adhering to the material of the wires and temporary support frame, is that it dries or cures without distortion or imposing any strain between the wires and support frame. When the adhesive has set or cured the thus formed assembly of electrodes and frame is removed from the jig on the temporary frame 123.

Thus it can be seen that a temporary assembly of all the electrodes of the electron gun is achieved with the electrodes assembled and accurately located with respect to one another without strain on the temporary support frame.

This temporary assembly is then located 'in an envelope assembly jig carried within an oven chamber. The envelope assembly jig includes means to receive and hold the temporary support frame and means to receive and hold the

glass envelope portions

10, 11 and 12 around the electrodes and their respective supporting wires in their correct final assembled condition.

Before the glass envelope portions are placed in the envelope assembly jig the edges of the portions are coated with frit material such as pyroceram frit mixed with a nitro-cellulose binder in a volatile solvent such as amyl acetate. When the envelope portions are placed in the envelope assembly jig the Pyroceram coatings are in contact with the supporting wires for the electrodes in the case of the joint between the portions and I1 and with one another in the case of the joint between the cap 12 and the other portions.

A glass evacuation tube also appropriately coated at one end with (Pyroceram) frit is also located in the envelope assembly jig in a correct position adjacent an appropriate aperture on one of the

tube envelope portions

10 or 11 to be joined thereto and form subsequently an evacuating means for the finished cathode ray tube. The other end of the glass tube is connected in the envelope assembly jig to a high vacuum system outside the oven and the envelope assembly jig includes heating means to surround the glass evacuation tube for subsequent fusing of the tube to seal the envelope.

When the Pyroceram coated envelope components and the electrodes are correctly assembled in the jig the oven temperatures is taken quickly at the rate of some 7C to 10C per minute to a temperature of 390C in order to fuse the Pyroceram" frit between the envelope portions and the glass spew tube thus to form an integral envelope. As the frit fuses, the envelope portions settle together slightly, the envelope assembly jig being arranged to accommodate this. The frit also flows around the electrode supporting wires and completes the required seal around them.

After the temperature of 390C is reached the tem perature is carried more slowly at the rate of some 3C per minute to 440C at which level it is maintained for approximately h hr., to devitrify the Pyroceram" material to complete the joints and the sealing between the envelope portions. The oven is then allowed to cool and evacuation of the envelope through the spew tube is commenced with the envelope remaining in the envelope assembly jig within the oven. When the evacuation is completed the spew tube is heated electrically and fused to seal the evacuated tube.

The completed tube envelope with the electron gun electrodes located and sealed therein is then removed from the envelope assembly jig and the temporary support frame 123 and the temporary wires are cropped from the supporting wires to leave the finished assembled tube ready for subsequent treatment such as gettering in known manner per se, and cathode activation and ageing in known manner per se.

1 claim:

1. A method of assembling a cathode ray display tube which includes a plurality of electrodes forming an electron gun assembly, the electrodes being each provided with supporting wires by which they are supported from the envelope wall of the tube and located with respect to one another in the finished tube, comprising the steps of assembling the electrodes in their correct relative disposition on a temporary support frame by means of said supporting wires to form a temporary assembly of the electron gun, assembling the envelope of the tube around the electrodes in a plurality of portions with the supporting wires each passing through a seam between those portions sealing the envelope portions to each other and the supporting wires of the electrodes, and with the temporary support frame lying outside the envelope, and then removing the temporary frame from the supporting wires.

2. A method according to claim 1, wherein X" and Y deflection plates, an interplate screen and a screen potential electrode which are also each provided with supporting wires by which they are supported from the envelope wall of the tube and located with respect to one another and the electron gun in the finished tube, are assembled together with said electron gun electrodes in their correct relative disposition thereto on said temporary support frame before the envelope is assembled there-around.

3. A method according to claim 2, wherein some of said electrodes are pre-assembled in at least one group as a sub-assembly in their correct relative disposition before being assembled on said temporary support frame.

4. A method according to claim 3, wherein filament and grid electrodes of said electron gun are preassembled as a first sub-assembly of electrodes.

5. A method according to claim 4, wherein first, second and third anodes of said electron gun together with an interplate screen are pre-assembled as a second subassembly of electrodes.

6. A method according to claim 4, wherein the supporting wires for said filament and for said grid are assembled together in a first jig device in their correct disposition, the filament is then attached to its supporting wires and the grid electrode is then located relative to the filament on the jig and attached to its supporting wires to form said first sub-assembly.

7. A method according to claim 6, wherein the assembled supporting wires for the filament and grid are positioned in a second jig device, said filament is coil wound on a rotatable mandrel positioned in the second jig device above the supporting wires for the filament, and the winding of the filament includes the steps of feeding the filament material from feed means over the mandrel, attaching the filament material to a crank pin provided adjacent to but eccentric from the mandrel, rotating the mandrel carrying the crank pin therewith to wind the filament material in a coil of the required number of turns on the mandrel, attaching the free ends of the coil extending from the mandrel to the crank pin and to the feed means, to respective ones of the support wires for the filament, severing the attached filament from the feed material and from the crank pin and then axially with drawing the mandrel from the attached filament.

8. A method according to claim 7, wherein said assembled supporting wires are located in a portion of the jig device which is movable between a loading position clear of the mandrel and a locating position beneath the mandrel for the attachment of a filament.

9. A method according to claim 8, wherein said grid electrode is initially located on a fixed part of the jig device and transfer means is provided to carry it in fixed orientation to be correctly located above the supporting wires therefor carried in said movable jig portion in said locating position.

10. A method according to claim wherein said second sub-assembly is formed by attaching the supporting wires of the electrodes thereof to one or more glass coated temporary joining wires, the attachment being achieved by fusing the glass coating of the joining wires to the electrode supporting wires.

11. A method according to claim 10, wherein said electrodes are located with their supporting wires extending horizontally on a vertical mandrel of a third jig device by means of their electron beam apertures, with intervening spacing means to achieve their correct axial disposition, and the third jig device includes means for supporting a first glass coated joining wire in correct dispostion to the supporting wires, and means for rotating the electrodes about said mandrel to load said supporting wires against said first joining wire while the glass coating thereon is fused to the supporting wires.

12. A method according to claim 11, wherein when said glass coating has been fused to the supporting wires, a gap remains between the joining wire and each supporting wire fused thereto.

13. A method according to claim 11, wherein each electrode of the second sub-assembly has two oppositely extending supporting wires, and said third jig device includes a pivotable portion having a vertically extending abutment disposed so that on pivoting of the pivotable portion in one direction to a fixed stop, said abutment engages a first supporting wire of each electrode to rotate the electrodes about the mandrel and load the other supporting wires thereof against said first joining wire for fusing thereto.

14. A method according to claim 13, wherein said pivotable portion includes means for supporting a second joining wire in correct disposition to said first supporting wires so that on pivoting of the pivotable portion in the other direction to a fixed stop, said second joining wire is loaded against the first supporting wires for fusing thereto.

15. A method according to claim 10, wherein said interplate screen is mechanically supported from the third anode of the electron gun electrodes, and is attached to said joining wires by means of the third anode supporting wires only as a separate step from the attachment of the remaining electrodes of the second sub-assembly.

16. A method according to claim 5, wherein said electrodes are assembled to said temporary support frame in a fourth jig device which includes a horizontal mandrel for supporting and locating said first and second sub-assemblies, support and locating means for said X" and Y" plates and said screen potential electrodes and a horizontal surface disposed around the mandrel to angularly locate the electrodes about the axis of the electron gun by means of the supporting wires of the electrodes, and which includes support and locating means to hold said temporary support frame beneath and just spaced from the supporting wires of the electrodes, the electrodes and support frame being positioned in said fourth jig device and the supporting wires attached to the support frame with adhesive.

17. A method according to claim 16, wherein said adhesive is strain free on curing.

18. A method according to claim 2, wherein said envelope portions are assembled around said electrodes in a fifth jig device positioned within an oven chamber, the fifth jig device comprising means for locating said temporary support frame and means for locating the envelope portions in correct disposition around the electrodes, the envelope portion seam edges being coated with fusable glass frit material of a lower melting point than the material of the envelope portions, before positioning in the jig device, and the oven temperature being raised to fuse the frit to seal and join the envelope portions to each other and the supporting wires of the electrodes.

19. A method according to claim 18, wherein said glass frit is a de-vitrifiable glass frit and is applied to the envelope portions mixed with a nitro-cellulose binder and an organic volatile solvent.

20. A method according to claim 19,-wherein said oven temperature is raised from ambient temperature at the rate of between 7C and 10C per minute to a with fusable glass frit at the end and positioned in said jig before raising the oven temperature so that it is sealed to the envelope when the envelope portions are sealed together, and wherein the oven chamber is provided with means communicating with said tube for the evacuation of the envelope after sealing and cooling, and means for fusing and sealing the glass tube after evacuation of the envelope.

t I II 1 t

Claims

2. A method according to claim 1, wherein ''''X'''' and ''''Y'''' deflection plates, an interplate screen and a screen potential electrode which are also each provided with supporting wires by which they are supported from the envelope wall of the tube and located with respect to one another and the electron gun in the finished tube, are assembled together with said electron gun electrodes in their correct relative disposition thereto on said temporary support frame before the envelope is assembled there-around.

4. A method according to claim 3, wherein filament and grid electrodes of said electron gun are pre-assembled as a first sub-assembly of electrodes.

5. A method according to claim 4, wherein first, second and third anodes of sAid electron gun together with an interplate screen are pre-assembled as a second sub-assembly of electrodes.

10. A method according to claim 5 wherein said second sub-assembly is formed by attaching the supporting wires of the electrodes thereof to one or more glass coated temporary joining wires, the attachment being achieved by fusing the glass coating of the joining wires to the electrode supporting wires.

16. A method according to claim 5, wherein said electrodes are assembled to said temporary support frame in a fourth jig device which includes a horizontal mandrel for supporting and locating said first and second sub-assemblies, support and locating means for said ''''X'''' and ''''Y'''' plates and said screen potential electrodes and a horizontal surface disposed around the mandrel to angularly locate the electrodes about the axis of the electron gun by means of the supporting wires of the electrodes, and which includes support and locating means to hold said temporary support frame beneath and just spaced from the supporting wires of the electrodes, the electrodes and support frame being positioned in said fourth jig device and the supporting wires attached to the support frame with adhesive.

20. A method according to claim 19, wherein said oven temperature is raised from ambient temperature at the rate of between 7*C and 10*C per minute to a temperature of 380*C to 400*C to fuse the glass frit, then raised further at the rate of approximately 30*C per minute to a temperature of 420*C to 460*C and maintained at that temperature for a period of time to de-vitrify the glass frit.

21. A method according to claim 18, wherein said fifth jig includes means for holding and locating a glass evacuating tube in engagement with an aperture in one of said envelope portions, the glass tube being coated with fusable glass frit at the end and positioned in said jig before raising the oven temperature so that it is sealed to the envelope when the envelope portions are sealed together, and wherein the oven chamber is provided with means communicating with said tube for the evacuation of the envelope after sealing and cooling, and means for fusing and sealing the glass tube after evacuation of the envelope.