US2250622A - Cathode-ray tube and method of manufacture thereof - Google Patents

Description

y 1941- R. M. sown-z v 2,250,622 CATHODE-RAY TUBE AND METHOD OF MANUFACTURE THEREOF Filed Feb. 17, 1939 4 Sheets-Sheet l Fzy. 2

mam-4w INVEN TOR.

July 29, 1941. R. M. BOWIE 2,250,622

CATHODE-RAY TUBE AND METHOD OF MANUFACTURE THEREOF Filed Feb. 17, 1939 4 Sheets-Sheet 2 Verified] Os cilia to f. 4 INVEN7:0R. By

9 R. M. BOWIE 2,250,622

CATHODE-RAY TUBE AND METHOD OF MANUFACTURE THEREOF Filed Feb. 17, 1939 4 Sheets-Sheet 3 INVENTOR.

y 1941- R. M. BOWIE 2,250,622

CATHODE-RAY TUBE AND METHOD. OF MANUFACTURE THEREOF Filed Feb. 17, 1939 4 Sheets-Sheet 4 A TTORNEY Patented July 29, 1941 CATHODIll-RAY TUBE AND METHOD F 7 MANUFACTURE THEREOF Robert M. Bowie, St. Marys, Pa., assignor to Bygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application February 17, 1939, Serial No. 256,924

3 Claims.

This invention relates to cathode-ray tubes and more especially to such tubes as have a bulb composed at least in part of a tubular metal portion.

A principal object of the invention is to provide a cathode-ray tube which is mechanically strong at all points.

Heretofore, it has been proposed to manufacture cathode-ray tubes having a main body portion of metal which is joined to an elongated neck section of glass. The glass neckwas necessitated in tubes where the beamdeflection or beam focussing was eiiected electromagnetically, because if the neck were of the same material as the main body section, for example iron, steel or the like, the loss of energy by eddy current action would be too great. According y, it is a principalobject of this invention to provide an enclosing envelope for a cathode-ray tube wherein both the main body portion as well as the neck portion are of metal.

Another object is to provide a cathode-ray tube of the type having a main body portion of metal joined to a glass neck portion, with means to shield the glass neckmechanically and electrically.

Another object is to provide an improved header or closure member for a metal wall cathoderay tube whereby the lead-in members and electrodes of the electron gun can be insulatingly sup-.

ported from the metal tube wall.

A feature of the invention relates to a cathoderay tube having a metal bulb or envelope formed of two separate cylindrical half shells joined together to form a single tubular metal unit.

Another feature relates to a cathode-ray tube having an elongated metal neck of non-magnetic material.

A further feature relates to a metal neck cathode-ray tube having welded thereto a metalframed glass header in the form of a thick button-like glass body through which the lead-in method of sealing-in and of supporting electrostatic deflector plates irom a metal wall section of a cathode-ray tube. I

A still further feature relates to the novel organization, arrangement and relative location of parts whereby a cathode-ray tube of the type having a metal wall section can be economically manufactured.

Other features and advantages not specifically enumerated will be apparent from the following detailed descriptions and appended claims. While various features of the invention will be described in connection with certain specific constructions and materials, it will be understood that the invention'isnot necessarily limited thereto. Furthermore, only those parts of a cathode-ray tube are shown as are necessary to understand the various featuresand objects of the invention. Accordingly, in the drawings:

Fig. 1 is a plan view ofan improved form of metal bulb for cathode-ray tubes according t the invention. 7

Fig. 2 is a top end view of Fig. 1.

Fig. 3 is a bottom end view of Fig. 1.

Fig. 4 is a sectional view of another embodiment' of a metal cathode-ray tube embodying features of the invention with portions broken away for the purposes of simplicity in'the draw- Fig. 5 is a sectional view of a cathode-ray tube of the composite glass neck and metal body type,

having a special neck enclosing andprotecting arrangement according to the. invention.

Fig. 6 is a partial sectional view of another embodiment of the invention to illustrate the improved manner of sealing-in and supporting the deflector plates through the metal wall of the cathode-ray tube.

Fig.7 is a detailed view, partly in section, of a preferred form of metal closure cap that may be used with the tubes of'Fig. 5.

Referring more particularly to Figs. 1 to 3, there is shown the tubular portion of a metal walled cathode-ray tube envelope according to the invention. This tubular portion of the envelope consists of an elongated neck section I terminating in a tapered or funnel-like main body section 6. .Preferably, although not necessarily, the end of section 5 is formed with a vided between the flange 4 and the wall of sec- 7 tion 6 a shoulder 40 to receive and bear the thrust of a relatively thick glass window (notshown) having sealed therearound a metal frame as described in detail in U. 8. Patent No. 2,219,578. As described in said application, the metal frame. sealed into the glass window is provided with a radially extending flat flange similar to flange 4 to which it is seam or arc-welded to provide a vacuum-tight seal between the window and the section 8. The open end of section I may likewise be closed off by a metal framed glass header through which are sealed the various lead-in and electrode support wires as will be described hereinbelow in connection with the embodiment of Fig. 4. It will be understood of course, thatwhen the device is to be used as an oscilloscope, television reproducer or the like, the inside surface of the glass window is provided with a suitable fluorescent coating and there is mounted within the neck portion 8 and connected to the various lead-in wires, a suitable electron gun and beam deflecting arrangement well known in the cathode-ray tube art.

While it has been proposedheretofore to provide cathode-ray tubes wherein the section 8 is of metal, in these prior tubes the neck section 5 has been of glass. In these prior arrangements, it is feasible to form the section 8 from a metal blank in successive steps by a deep drawing operation as described for example in U. S. Patent No. 2,232,098. However, this deep drawing method is not entirely feasible where the section 5 is to form an integral part of section 8. This is particularly true where the section 8 as shown in Figs. 1 to 3 for example, is rectangular in cross section and the section 8 is round in cross section. I have found that these parts can be formed as an integral unit while preserving the necessary dimensional accuracy and coaxiality between the neck and funnel sections, by forming these sections as two separate symmetrical half shells. Thus as shown in Figs. 1, 2 and 3, the envelope is formed by the two half sections or shells from suitable sheet metal and the two shells are joined together, preferably by flash welding, along the abutting edges 2, 3. During the formation of the half shells, the funnelshaped half sections 8 may be given any desired shape. Thus, in the tube shown in Figs. 1 to 3, the half sections 8 are formed so that when they are assembled together, the funnel-shaped section 8 is substantially rectangular in cross section with rounded corners and gradually tapers down until it approaches a round or cylindrical shape at its constricted end where it joins the neck section 5. Since it is highly important that the flanges I and 4 be flat andfree from ridges, and since the flash welding operation mentioned above leaves a ridge, this ridge should be ground away as indicated by the numerals 8, 8, and 8a, 9a. While the invention is not limited to any particular metal for the bi-part envelope, it may be made from sheet steel or sheet iron in which event the focussing and deflection of the beam should be effected electrostatically.

If it is desired to' effect the focussing and deflecting actions by electro-magnetic means external to the neck 5, the biepart envelope may be made of suitable non-magnetic alloy such for example as l88 Stainless Steel" or an alloy known as K Monel made by International Nickel Company. Instead of making the entire envelope out of the non-magnetic material, only the neck portion where the magnetic focussing and magnetic deflecting means are located, may be of such nonmagnetic metal or alloy. Such an arrangement is disclosed in Fig. 4. In this embodiment, the funnel-shaped metal body section Il which is shown broken away, is formed of steel or iron as a separate unit, preferably as described for example in U. 8. Patent No. 2,232,098, the larger end of section Il being closed off in any wellknown manner, for example by a'metal-framed glass window. .11! section I1 is rectangular in cross-section, then it preferably tapers down to a circular cross-section at its smaller end, terminating in a ring neck Ila. Joined to ring Ila by seam-welding or in any other suitable vacuum-tight manner, is a more steeply tapered frusto-conical metal member I8 having a ring neck 21 where it is welded to ring Ila. Member I8 also has a ring section l8a at its smaller end where it is joined in a. vacuum-tight manner, for example by seam-welding, to the end of the metal neck I3. It will be understood that the support member l8is not absolutely necessary and that the section Il may be drawn down so that the ring Ila fits directly into the neck I3 where it is welded thereto. Likewise if desired, the neck I3 may. have its upper endspun to form an integral cone similar to member I8 whereby this spun end of the neck can be welded directly to the ring Ila, thus eliminating the weld 25. Preferably, the neck I3 is of a non-magnetic metal or alloy such as 18-8 Stainless Steel or K Monel metal alloy sold by International Nickel Company. The lower end of neck I8 is closed by a metal-framed glass header in the form of a button 28 having a metal ring I2 sealed therein in a vacuum-tight manner. Preferably, the ring I2 is sealed into the button 28 by a method such as described in detail in U. S. Patent No. 2,219,573. In general, 1

this method consists in clamping the ring I2 so that the inwardly extending rim or margin I 2a extends into a mold cavity, the mold cavity being substantially circular in shape. A quantity of molten glass, preferably in the form of an incandescent gather is then deposited in the mold and immediately subjected to molding pressure to cause it to flow outwardly into engagement with the rim I2a which has been previously oxidized as is wellknown in the art. The temperature of the glass gather when it contacts with this oxidized rim I2a is sufllcient to raise the latter to a temperature where a vacuum-tight seal results upon the subsequent cooling of the gather. Preferably, the glass is charged into the mold at such a temperature that it raises the rim I2a to a temperature of the order of 1000" C. During the molding pressure on the glass gather, the mold is also provided with a plurality of projections whereby the button I2a is formed with transverse bores or perforations preferably distributed in a circle around the center of the button 28 and at the same time a central exhaust hole I5a is formed in the button. After annealing and cooling of the formed button with the rim I2a sealed therein, the excess glass can be ground from the faces of the button, the button therefore having openings extending completely therethrough to.

receive the lead-in wires preferably in the form of rigid metal rods I4, Ila, Ilb, c, etc. The header or button 28 with its sealed-in frame I2 is then placed on a suitable rotating head provided with holes in alignment with the holes in removal of the female mold member, a chuck is lowered carrying a piece of exhaust tubing I! which is then molded or welded to the edge of the exhaust opening I541. The completed header consisting of the glass button 28 with the rigid wires or prongs l4, l4a, I41), I40, etc., sealed there- |2 sealed therein and mm the depending exhaust tubulation l5, may be suitably annealed and cooled.

Where the neck I3 is of' non-magnetic mate rial, it is possible to energize the scanning. coils or windings 24 at low frequency. If high frequency scanning is desired, electrostatic deflection may be employed. Thus in Fig. 4, the lowfrequency vertical scanning may be effected electromagnetically and the high frequency horizontal scanning may be effected electrostatically.

Any wellknown type of cathode-ray gun may be mounted on the metal framed header shown.

A simple but satisfactory gun is shown in Fig. 4.

In the center of a circular ceramic insulator i3 is riveted a hollow metal cathode tube 20 having its upper end flat and closed. A heater filament 20a has its ends welded to the prongs |4b, I40, and is supported within the cathode sleeve 20 but insulated therefrom in any wellknown manner. The ceramic insulator I8 is provided with a circular shoulder |8a against which is seated the inverted circular metal cup |9 having a perforation 9a. in its top in alignment with the axis of member 20. The member l8 serves as a control grid and is fastened to insulator |8 in-any suitable manner. A connector tab |9b for the grid, passes through an opening in insulator l3 and is connected to the grid prong sealed through the glass header. The assembly is fastened in place on the prongs l4, Na, in any manner well-' known in the art, for example by eyelets l8b. The rods I4 and Na. extend upwardly through ceramic or glass tubes l4}, Hg, and have the electrostatic deflector plates |4d, He, welded thereto. In order to insure the circular symmetry of the accelerating electric field penetrating through grid hole l9a, a tubular anode IS with a hole Illa in front of grid hole |9a may be attached to the glass rods Hi and Mg by means of clamps H, which in turn are metallically connected to neck l3 by connector- I la. After the gun has been assembled on the header 28, it is inserted through the lower end of metal neck I3 and the frame I2 is welded or otherwise sealed in a vacuum-tight manner to the end of neck I3 as indicated by the numeral 26.

It is of course understood that cathode 20 is connected to a prong (not shown in the drawing) which is sealed through header 28 in order to provide the necessary cathode connection for the return leads of the potentials applied to grid l9 and anode 20. Preferably, the top end 20b of the cathode is coated with electron-emissive materials wellknown in the electron discharge tube art. The electrons leaving the cathode are drawn through the grid aperture l9a by the accelerating anodes and are then focussed into a pencil converging on the screen (not shown) by means of the magnetic focussing device 2|. This device consists of an iron frame 2| which substantially surrounds and encloses the windings 22 except for a small opening 23 extending comthrough, and with the surrounding metal frame pletely around the'neck I3. The type of magnetic fleld penetrating through slot 23 .into the path of the electron beam is known as thin magnetic lens. The focal length or focussing power of the device 2| can be varied or adjusted by adjusting the magnetizing current through thewindings 22 as for example by means of the battery 22a and variable resistance 22b. Any one of a number of wellknown forms of low frequency magnetic deflecting coils may be used, as'indlcated schematically by the numeral 24. The source of the low frequency deflecting currents is indicated schematically in the drawings by the numeral 24a. The plates Md and He will of course have'suitable high frequency deflecting potentials applied thereto in the usual manner.

It will be understood of course, that after the *tube has been completely assembled and exhausted in accordance with wellknown procedures, the tubulation I5 is sealed off.

Should the loss of deflecting power in the metal neck l3 be excessive where magnetic deflection is used v it may be desirable to employ a glass neck which is provided with a suitable 'mechanical and electrical shield. Such an arrange- -ment is shown in Fig. 5. In this flgure, the funnel-shaped main metal body portion of the tube 33 may be the same as the portion I! described in connection with Fig. 4, the larger end of the body portion 38 being closed off by a suitable window as'above described. The tapered member 36 is provided with a rim 3641. which is welded to the corresponding rim or neck 38a. Preferably, the rim 36a is provided with a spun-over flange or lip 39 for purposes to be described.

Member 38 may be of any metal alloysuitable for providing a vacuum-tight seal with the glass neck 3|. Neck 3| may be flared outwardly at its upper-end to provide an enlarged rim '3la where it is sealed in a vacuum-tight manner to the member 36. The glass neck 3| is closed at its lower end by a glass header 32 in the form of a glass button having the lead-in wires or prongs 32a, 32b, 32c, 32d, directly sealed therethrough in a vacuum-tight manner as described in connection with Fig. 4. e

A suitable electron gun designated generally by the numeral 34 may be mounted on an insulator support 34a suitably fastened to the inwardly projecting ends of the prongs 32a, 32b and if desired, the inner surface of the neck 3| may be provided .with a metallic or other conductive coating 35 which extends preferably from the rim 3|a downwardly and slightly overlaps the end 01' the electron gun 34 as shown. The coating 35 may, if desired, be of .Aquadag and suitable electrostatic deflector plates may be mounted within the neck or within the portion 36 as will be described hereinbelow.

The tube is constructed and exhausted in the usual manner without the shielding member |4. After sealing off the exhaust tubulation 33 and after testing, member 44 is forced in place against the lip 39 where it may be soldered or spotwelded with an arc. In the particular tube shown, a type of scanning yoke is required in Such' a yoke maybe fitted into the space both a deflecting yoke and a focussing coil may be inserted between members 2| and 34 as described above in connection with Fig. 4.

In order to improve the mechanical strength of the neck assembly and to hold the deflecting and focussing yokes in place, a cap 42 (Fig. 7) may be provided. Cap 42 has an aperture 43 to fit snugly over the neck II and the rim of member 42 may be provided with three or more bayonet type; slots 4| to engage the corresponding pins 40 on the member 44. A spring or other suitable means may be provided (not shown) within the 'cap 42 to force the magnetic yoke such as represented by 2| and 22 (Fig. 4) against the flared end of neck 3|. In certain cases, it is undesirable to support the electrostatic deflecting plates and the gun assembly from the same header or stem as would berequired for instance in the case of the metal tube of Fig. 1, because such an arrangement frequency introduces excessive capacity between the deflection plate leads or between the deflection plate leads and the grid lead. In glass bulb cathode-ray tubes, it is customary in such cases to take the deflection plate leads directly through the side of the glass bulb. In the case of metal cathode ray tubes however, this method of sealing is much more difllcult since a suitable alloy must be provided to which to seal the glass through which the leads pass. Fig. 6- shows a construction wherein this difiiculty is overcome while providing an excellent means of locating the lead holes with respect to each other and with respect to the gun. In this embodiment, the metal frusto-conical or tapered body portion 53 may be similar to the corresponding portions 6 (Fig. 1); ll (Fig. 2); and 38 (Fig. 3). The portion 53 is provided with a slightly tapered rim 53a which is welded to the correspondingly slightly tapered rim 60 of a metal member 60a. Member 60a is preferably made of an alloy which seals readily to the glass beads 55a. If beads 55a are of '705AJ glass, the member 60a may be of an alloy sold by the General Electric Company under the name Fernico, or it may be desired to employ Corning G-12 glass for the beads 55a in which event an alloy such as Alleghany member 55" may be used for the member 60a. Member 60a is provided with a plurality of struck-up reentrant eyelets 60b to receive the glass beads 65a which have been previously sealed on to the respective support wires 55 which may be of .the same metal as member 60a. Wires 55 carry at their inner ends the usual deflector plates 51. A similar set of deflector plates 58 are mounted at right angles to the plates 51 and the wires supporting these plates are insulatingly sealed through the wall of member 60a similarly to the sealing-in of the wires 55.

The glass neck 5| is sealed at its upper end to the reduced end or collar portion 6| of member 60a and within the neck 5| is mounted any wellknown form of electron gun 54. The gun shown consists simply of a ceramic disk similar to I! (Fig. 4) on which are mounted a cathode and a grid similar to 20 and I 9 (Fig. 4). The anode I ll (Fig. 4) is replaced, however, by the conductive coating 59 on the interior of the neck. The

interior of neck 5| may be provided with a con ductive coating 59 and suitable magnetic focusslng coils may surround the neck as described above in connection with Fig. 4. Itwill be understood of course that if the gun 54 is of the electrostatic focussing type. that the magnetic focussing coils are not necessary. If desired, a member such as member 44 (Fig. 5) may surround and enclose the neck II although in the embodiment of Fig. 6, the tube as shown with he conventional insulator shell base Ha carrying the usual-contact prongs Bib which are connected to the various electrodes of the electron gun.

While in the foregoing description, it hasbeen I mentioned that the larger ends of the metal section 6 (Fig. 1); I! (Fig. 4); 38 (Fig. 5) and 53 (Fig. 6), are closed by transparent glass windows, it will be understood that this is not necessary unless the device is to be used as a television receiving tube or the like. For example, the tube may be used to provide television picture signals corresponding to a stationary picture or view in which event the glass window may bereplaced by a steel sheetwelded to the larger end of the main body section. This plate may carry on its inner surface an aluminum screen bearing the flgures or other design painted thereon with carbon or other similar material. In such an arrangement, the screen when scanned by the electron gun will yield television signals which may be used for advertising, testing or the like. In this latter embodiment, it is not even essential that the main body sections have a frustoconical shape or that they be closed at the larger and by a welding operation. If an aluminum advertising or testing screen of the type referred to is employed, it can be introduced into the bulb 38 (Fig. 5) for instance through the neck 3| before the weld 31. is made.

Various changes and modifications can be made in the disclosed embodiments without departing from the spirit and scope of the invention.

What I claim is:

1. A cathode-ray tube having a flared body portion of metal with a glass window hermetically sealed to the larger end, a neck composed at least in part of tubular glass, an electron gun mounted in said neck and a tubular metallic protective casing for'said glass neck, said casing being integrally fastened to said metal body portion to form a continuation thereof but radially spaced from said glass neck.

2. A cathode-ray tube according to claim 1 in which said casing is of larger diameter than the glass neck and at least one magnetic yoke surrounds the glass neck and is interposed between the neck and said casing.

3. A cathode-ray tube comprising a metal body section having sealed thereto a tubular glass neck, a magnetic focussing coil and a magnetic deflecting coil surrounding said neck, a tubular metal protective casing surrounding said coils and fastened at one end to said metal body portion to form an integral continuation thereof, and a removable metallic closure cap for the other end of said casing.

ROBERT M. BOWIE.

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