US2058293A - Cathode ray tube - Google Patents

Description

oct. zo, l1936.

L. F. BROADWAY ET A`| CATHODE RAY TUBE 2 Sheets-Sheet v1 Filed March 29, 1955 Oct- 20, 1936. L. FQ BROADWAY ET Al. 2,058,293

CATHODE RAY TUBE Filed March 29, 1955 J 2 Sheets-Sheet 2 they tend to bend during .the

Patented Oct. 20, 1936 2,058,293 oA'rHoDE RAY Leonard Francis Broadway,

William Francis .Tedhain, don, England, assignorsto Industriesl LimitedJ-Iayes, a company of Great -Britain Application March 29 Ealing, London, and

Abbey lWood, Lon- Electric .& Musical Middlesex, England,

, 1935, seriaifNo. 13,660

VIn Great Britaln March 26, 1934 The `presentinvention relates to improvements in cathode ray tubes. v l A cathode ray tube is known which comprises a cathode, a modulating electrode, one or more auxiliary electrodes and an anode arrangedfwithin the `tube in the order mentioned.` The auxiliary electrodes and the anode co-operatein focusing the beam ofelectrons vemitted from the-cathode upon a screen, such as a fluorescent screen, associaed with the tube. Frequently,the focusing electrodes are in the form of tubes or cylinders, and two or more of them may be of equal cross` sectional areas. It is found inr this -case that in order to get a good focus of the ray it-is essential that the several electrodes should `be -very accurately aligned within the tube. v Hithertorthe electrodes have been mounted upon wires held in a pinch sealed into one end of the tube or upon wires sealed through the sidewalls of the tube. With such arrangements it has been found diiiicult to locate the-electrodes accurately in their correct relativev positions and, if the wires are thin or of unsuitable`v material, baking process necessary to drive occluded gas out of the `electrodes and theenvelope of the tube. T

An object of the .present invention is to pro-v vide an improved mounting for the` electrodes n which does not suier from the above-mentioned required -on the rods between electrodes.

disadvantages and which facilitates the assembly of the electrodes Within the tube envelope.

A further object is to provide, in a cathode ray tube having an envelope comprising a plurality of electrodes Xed to a support within" said en'- velope, a unitary self-supporting structure comprising at least two of said electrodes disposed co-axiallyone behind the other in predetermined spaced relationship, a pluralityY of rigid -metal rods vdisposed longitudinally'of and around the axis of said electrodes, and Yaclamp, saidelecr trodes and said clamp being rigidly connectedA with all of said rods, and said clamp engaging` said support. Y Y

Another object is to Lprovide a rigid'unitary electrode assembly for a vcathode ray tube whichl can beassembled before attachment to the pinchor any other part of the envelope of the tube.- A still further object is to provide a rigid unitary.- electrode assembly for a 'cathode'fra'ytube in which-a plurality of electrodes are each rigidlyconnected with aplurality of metal rods and wherein' no insulating 'distance-pieces areI Itlia's been found that thediiference in expansion co" efcients between such insulating distance-piecesand metal electrode-supporting rodscauses the loosening of an electrodeassemblyi during the baking process, and that it is difficult to obtain a satisfactory insulating material which can be machined to form distance-pieces of accurate l in the length of suchdistance-pieces are cumulative. The inventionfwill be further described with reference to theexample shown in the accompanying drawings, in which Fig. l is a side elevation of part of a cathode ray tube, with the :envelope in section,

Fig. 2 isgan end elevation of the support collar, IFig. '3 is an *end'elevation of an electrode mounting assembly, *n Y -v Figs. 4, 5, and 6 areend elevations of parts shown inflig, Y v Y Fig.v 7 is a side elevationofthe part shown in 6,-` Y v Y .j v

' Fig. Sis an end elevation of a spacer ring'.

The `cathode ray tube comprises a glass envelope in the 'form of av tubular portion I0 flaringfout into a frusto-conical portion not shown. Upon the inside o f the base of the latter portion there is disposed, a fluorescent screen.l

Thefend ofthe tubular portion remote from length. Furthermore, errors the screen Y'is provided with aninturned tubular foot vl Iv on the'inner end of which is formed a pinch-l2 in which are sealed conductors conneoting with the variousl electrodes. These conductors are omitted from theY drawings for the sake of cle'arness.

'A' cathode shield I4, an accelerator I5, a modulating electrode l5 and a first anode Il, arerarranged cra-axially withthe cylindrical portion of the envelope I.- The cathode shield I4 is in the form o f a cylinderh'avinga transverse diaphragm pro-'videdwith v'an aperture. A cathode heater and a cathode are supported from the pinch, and lie withinfthe cylindrical cathode shield I4, close behind the' diaphragm, hence they are not Visible in the drawings` A second anode, which does not appear in the 'drawings,'is` in the form of silveringv on'thetubewalls. The electrodes |4,.-|` 5,--l6, and Il are mounted upon three 'parallel rods i8, which are fof nickel or of Staybrite steel and symmetricallydistributed aboutthe tube axis. y These rods serve bot-'nuto ,support and'to align theelectrodes'moun'te'd' thereon, and they arefixed'by meansof aclampingcollar I9, to the cylindrical glass foot Il'Vv sealed internally within the tube.' The clamping collar -I9 (Fig. 2) is made of nickel in three similar sections and is` adapted to be clamped upon the glass foot by means Aof clamp'-A ing screwsf Each section has an arcuate central portion and a flange 20 projecting radially outward from each end]- The flanges] of each section arenclamp'ed' tothe adjacent "end anges of ythe neighbouring sections' by pairs of screws Zul L and nuts 'EL' e sections may be4 formed from flat strip materialjandat the centreI of the arcuate portion of eachisectionthe strip `material is bentv radially outward and doubled back upon itself to form a central radiallyk projecting flange 23. In the bending operation an aperture is formed in each flange 23 to receive the end of one of the support rods I8.

Each screw of two of the pairs of screws is provided with a spacing washer 24, these washers serving to space apart the three'sections of the collar correctly. The other pair of screws serves to tighten the collar on to the glass foot or on to suitable packing placed around the foot and these screws are provided with spring washers 25. The foot may, of course, be other thancylindrical, and in order to facilitate the clamping of the collar upon the foot the collar maybe made of corrugated sheet metal.

The rods also pass through holes in bosses 29 formed on three nickel spacer rings 26, 21, and 28. Eachspacer ring is provided at its centre with a circular aperture 30, (Fig. 8). The spacer rings areplaced at any convenient distance from one another along the support rods and serve to hold these rods parallel and at the correct distances apart.

The electrodes that are mounted upon the sup port rods are, in the present case, all in the form of cylinders and'have the same diameter, so that a description of a mounting of one of them applied to all of the others.

The cathode shield electrode I4 is mounted as a sliding t in a flanged nickel collar 3l (Fig. 4) which in turn is mounted upon an insulating annularV plate 32 of mica bearing three holes through which the support rods pass. The mica ring is .shown in Fig. 5, and the assembled electrode mounting is shown in Fig. 3. The flange of the collar 3l carries three symmetrically disposed holes 33 corresponding to three similarly disposed holes 34 in the Amica ring, and the collar and ring are fastened together by nickel rivets 35 passing through these holes. The diameter of the rivets 35 is slightly less than that of the holes 33 and 34 and the exact location of the collar relative to the ring is effected by three lugs 36 punched out of the iiange and which t into three notches 31 cut out of the inner edge of the mica ring.

The three holes in the mica ring through which the support rods pass have a diameter larger than that of the rods, and the holes are tted with nickel eyelets 38 the internal bores of which have a diameter substantially equal to that of the rods. Each eyelet is in the form of a short cylinder having two thin tongues 39 extending outwardly from opposite sides of the cylinder. The tongues are bent over, passed through two slots 40 cut in the mica ring, one on either side of an eyelet hole, and bent back so as to secure the eyelet firmly-in its hole. Alternatively the eyelets may be riveted in their holes.

Thus the electrode and the anged collar 3| are insulated from theeyelets 38 by they mica ring 32, and the ange of the collar may, if necessary, be cut away, as indicated at 4I, so as to be well clear of the eyelets. The external diameter of the mica rings 32 may be equal to the internal diameter of the cylindrical portion of the envelope Ill, so that the rings assist in locating the assembly centrally within the envelope.

The electrodes of the electron. gun, that is to say in this example the cathode shield I4, the accelerator I5, the modulator I6, 'and the rst anode I1 are all mounted in this manner upon separate collars and mica rings, the rst anode, on account of its length, having two sets of colv curately spaced from one another.

lars and rings. These electrodes and the spacer rings 26, 21 and 28 are threaded; in the proper sequence, upon the three support rods and are ac- The spacer rings and the eyelets on the mica rings are then rigidly fixed to the rods for example by spot welding. The cathode and its heater having been mounted in the pinch, the rods are clamped by means of the collar I9 upon the foot II and the latter is sealed within the main part of the envelope I0 of the tube with the pinch and electrode assembly extending within the cylindrical portion of the envelope.

While in the embodiment described above the leads to the electrodes are all taken through the pinch, if desired, leads to one or more of the electrodes may be taken through the side Walls of the envelope to the electrodes. Provision may also be made for maintaining the rods and spacer ringsat earth or any other xed potential. Al-

ternativelysome of the rods may serve as leads to i' some of they electrodes; in this case the appropriate 'eyelets must be connected electrically to theseV electrodes. Furthermore, electrodes of different diameters may be accommodated by making the anged collars of correspondingly diierent bores.

Since the supporting rods for the electrodes are of a substantial thickness of metal, no trouble is experienced in induction heating the metal parts and no distortion results from the heating since the parts are held rigidly by the spacer rings and electrode mounting rings and are substantially free from strain after assembly.

Many of the parts in the assembly are duplicated and can therefore be produced by mass production methods.

, We claim:

1. In a cathode ray tube having an envelope containing an electron gun consisting, apart from a cathode and an anode, of a plurality ofv electrodes xed to a support within said envelope, the arrangement of a unitary structure, comprising a plurality of rigid metal rods, a clamp and electrodes including at least a cathode shield, a modulator and an accelerator electrode, said rods disposed longitudinally of and around the axis of said electrodes spaced from said envelope, said electrodes and said clamp eachrigidly connected with all of said rods, a rigid metal spacer ring rigidly fastened to said rods and spaced from said clamp and electrodes, and said clamp attached to said support.

2. In a cathode ray tube having an envelopecontaining an electron gun consisting, apart from a cathode and an anode, of a plurality of electrodes fixed to a support within said envelope, the arrangement of a unitary structure, comprising a plurality of rigid metal rods, a clamp and electrodes including atleast a cathode shield, a modulator andan accelerator electrode, said rods disposed longitudinally of and around the axis of said electrodes spaced from said envelope, said electrodes and said clamp each rigidly connected with all of said rods, a rigid connection between at least one of said electrodes and all of said rods consisting in an apertured plate of insulating material rigidly connected tosaidrods and said electrode, and said clamp attachedto said support. i

. Y LEONARD FRANCIS BROADWAY.

WLLAMFRANCIS TEDHAM.

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