US2391573A

US2391573A - Method of and apparatus for making cold cathode fluorescent lamps or the like

Info

Publication number: US2391573A
Application number: US525446A
Authority: US
Inventors: Herzog Carl
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-03-07
Filing date: 1944-03-07
Publication date: 1945-12-25
Anticipated expiration: 1962-12-25

Description

Dec. 25, 1945. c. HERZOG 2,391,573

METHOD OF AND APPARATUS FOR MAKING COLD CATHODE 'FLUORESCENT LAMPS OR THE LIKE Filed MaFoh '7, 1944 2 Sheets-SheeI 1 INVENToR. /5 E 0419419519205,

` A fran/wey Dec. 25, 1945. C HERZOG METHOD oF AND APPARATUS FOR MAKING COLD CATHoDE FLUoREscENT LAMPS 0R THE LIKE 2 Sheets-Sheet 2 Filed March 7. 1944 Patented Dec. 25, 1'9'45 l METHOD oF AND APPARATUS Fon mime. com cA'rnoDE FLUonEscENT LAMPS on THE @a1-ll Herzog, Belleville, N. J.

Application March 7, .1944, serial No. 525,446

l1 Claims.

My invention relates to a mewthod of and apparatus for producing electronic devices, such as gaseous discharge tubes including cold cathode uorescent lamps, neon lamps, radio tubes or the like', and to such devices.

An important object of the invention is to pro- (Cl. 316i-11) Figure is a perspective view, parts broken away. showing a modified manner oi mounting the cathoder upon the contact extension of the retainer, i

videa continuouscmethod for performing the various steps in 'producing the iinished product,

such as a cold cathode fluorescent lamp, and will reduce the manipulation of the tube to the minimum.

A further object 'of the linvention is-to provide a method of' the above mentioned character which will eliminate the baking of the coating of the tube in o, furnace as a, separate method.

A further object of the invention is to provide a method which willevacuate the tube and seal in the electrode at the same-time.

A further object of the invention is to provide a methodwhich will Imaterially reduce the cost of baking cold cathode iiuorescent lamps.

, Figure 11 is a similar view showing a further modied'manner of mounting the cathode upon the retainer,

Figure 12 is a similar view showing/ a further modified manner of mounting the cathode upon the retainer, and

Figure 13 is a central vertical section, upon an enlarged scale, through the tube at the point of fusing the tube to the retainer, parts broken l away.

In the drawings, wherein for the purpose of,il lustration is shown a. preferred embodiment of my invention, the numeral l0 designates a glass tu-be, constituting the envelope of the cold cathode fluorescent lamp. 'I'his tube may be of any suit-'- A further object of the invention is toprovide apparatus for use in the practice of the method. A further object of the invention is to so mount the tubular electrode shell upon the contact extension of the retainer or retainer for reducing heat transfer from the electrode shell Other objects and advantages of the invention will be apparent 'during the course of the following description.'

in the accompanying drawings, forming a part of this application and in which like numerals are employed -to designate lilre parts throughout the same.

Figure 1 is a central vertical longitudinal section through apparatus embodying my invention,

showing the baking steps, v

Figure 2 is a similar view through the tube, partly' diagrammatic, showing the vacuum baklng, "l

Figure 3 is a similar view showing sealing the bottom end of the tube,

Figure 4 is a, similar view showing cutting o the" bottom end of the tube, 'l

Figure 5 is a similar view showing gas insertion into the tube,

Figure 6 is a similar view showing mercury insertion into the tube,

Figure 7 is a similar view showing sealing the ktop end of the tube,

Figure 8 is a similar view showing cutting off the top end of the tube -and producing the finished product,

Figure 91s an enlarged central longitudinal sction through the completed lamp,

able diameter and length. These tubes are frequently a half inch in diameter and eight feet long, although the dimensions may be varied. The inner surface of the tube i0 is covered or coated with a coating composition containing a linely divided luminescent or iiuorescent material, and this coating is dried. 1 may empioy the coating composition disclosed in the patent to T. M. Cortese, 2,318,060, and this coating may .tbe applied and dried in accordance with the method disclosed in the Cortese patent. However, the coating is not baked in a separate oven, but the baking occurs as a step in my method. The tube i0, Figure 1, has the coating compositiom il, which may be the fluorescent coating composition disclosed in the Cortese patent, ex-

tending originally throughout its entirelength, and dried but not baked, and this dried coating is removed from the ends of the tube I0 to points 'f i2, leaving cl'ean or 'uncoated zonesi3 and I4.

The tube I0 with the dried interior coating ll is vertically arranged with its opposite ends open and held within a holder I5 to be supported thereby. -4

-Disposed within the opposite ends of the tube l0 are electrodes, including electrode shells I 6. Each electrode shell is made of the purest iron obtainable. and the interior of the shell is coated with an electron emitting material, as is well known. Each electrode shell is press fitted into a cup-shaped contact extension I1 of a retainer i8, surrounding the electrode shell and spaced therefrom. The retainer I8 has a larger diameter than the electrode shell I6 and has a smaller diameter than the tube I0, and the ltube is fused to the retainer, to provide a vacuum-tight joint,

7,) sleeve 30.#

'ment therewith, to shift 'I'his cap is provided with as will be explained. The retainer forms a. ring or band extending radially beyond the electrode port is connected with a pipe shell I8. It desired, the electrode shell I6 may be welded to the contactextension' I1. The retainer I8 is made of a special commercial chromeiron alloy which has the same expansion coel- /cient as glass. The retainer I8 and the contact extension I'I have their ends imperforate, as

shown.

I also contemplate usingthe form of electrode which is an integral unit, as shown in Figure 2l of my copendlng application for Method oi and apparatus for producing cold cathode fluorescent lamps and to such lamps. led January 26, 1944, Serial No. 519,666.

I may employ the` lelectrode shown in Figure l0. In this ligure, I is an electrode shell, identical with the shell i8 and having a closed end Il',

f which is welded to a wire I8'. This wire is welded to the end of the contact extension I1 of the retainer I8. The wire I8' supports the electrode shell I8' in spaced concentric relation to the contact extension I'I and the retainer I9.

In Figure 11, I have shown a slightly diflerent arrangement wherein wires I9' are welded to the sides of the electrode shell I6' and to the4 bottom of the retainer I8. The arrangement is otherwise identical.'

In Figure 12, I have shown a further similar arrangement, wherein a radialribbon or strap is welded to the end I1' of the electrode shell and extends outwardly beyond the same and is welded to the bottom of the retainer I8. The arl rangement is otherwise identical with that shown in Figure 10.

e The advantage of the electrode shown in Figures 10, 11` and 12. is that the electrode shell is spaced from the contact extension Il and retainer I8 and connected therewith by the wire or wires or ribbon and is transmitted by conduction from -'the shell I6' to the contact extension or retainer I8 is reduced. This is advantageous after made and is operating in use.

'I'he electrode shell I6' corresponds to the electrode shell IB and the same retainer and contact extension is used.

I will now describe the operating units of apparaltus which is used in the practice of the method. The operating units generally by the numerals I9 and 28. Each operating unit includes sin outer block 2l, having a reduced inner end 22, which is screw-threaded, and provided with a main vertical chamber 23. This main vertical chamber receives compressible packing 24, which may be rubber, asbestos, or s. mixture of the same, or anyother suitable mate rial for enacting a vacuum-tight joint with'the glass tube I8. A follower ring is movable into the chamber 23 to compressthe packing 24. `Ihe chamber 23 leads into a chamber 26. Each block is provided with a vertical opening 21 to receive the shank 28 of a, clamp or socket 29. Thissocket 29 may be resilient. The shank 28 is electrically insulated upon the block 2l by an insulating The'shanks 28 are connected with the apposite poles of a source of current by lead wires 32, for a purpose to be screw-threaded extension 22 has a cap 33 mounti ed thereon and having screw-threaded engagethe followerring'25 and compress the packing.

s. water space or, jacket 34, and the coolant may enter at the pipe and leave by the pipe 38'. The unit 28 is provided with a hot air the amount of heat which.

the lamp has' been 'l are designated.

311, ieaalng inte the chamber as and this het m- 38, having a cut-oi! valve 39 connected therein. The

v to a, source of hot air and the-hot air is supplied described. Each reduced supplied to the glass tube has a temperature of port 74' through the pipe 38 so that it may enter the glass tube I8 at substantially 400 C. 'I'he unit 20 also has a vacuum port`40. in communication with the chamber 26 and connected with a pipe 4 I, having a cut-off valve 42 connected therein. The pipe 4i is connected with a source of vacuum. f

'Iihe unit I9 has a tube 43, connected therewith, and this tube communicates with a-port 44, leading into the chamber 28. The tube 43 has a hotl air discharge tube 45 and a gas inlet tube 46, connected therewith.` A rotary valve 41 is arranged at the union o! the

tubes

43, 45 and 46, and may be manipulated to place tube 43 in communication with tube 45, or tube 43 in communication with tube 46, or to cover the bore of the tube' 43 or tube 46.

The unit I9 is provided in its upper end with a well 48 for holding mercury and has a tapered recess 49 beneath the well to receive a tapered rotary valve element 50. This valve element is turned by a vstem 5l having a crank 52 and is urged upon its seat by a spring 53. The valve element 58 has diametrically oppositely arranged pockets 54,` for receiving measured amounts of the mercury and discharging the same into an inclined port 55, leading into the chamber 29. The well 48 is in communication with a vertical port 56 having a. horizontal branch 51 which leads into the recess 49 and feeds the mercury into the pocket 54. The vertical port discharges at its lower end into a horizontal recess 51', arranged beneath the valve element 58. It is thus seen that the mercury contacts with the upper and lower ends of the valve'element 50 and seals these ends, whereby a vacuum-tight joint is elected.

The practice of the method is as follows:

I take the glass tube I0 having the dried un baked fluorescent coating yIl and its ends open,y and insert the same in the holder I5, Figure l, which vertically supports the tube. The 'electrode shells I6 are held by the socketsor clamps 29 by inserting the contact extensions I'I into these sockets. The socket or clamp 29 has a smaller diameter than the retainer I8, as clearly shown in Figure 13. The units I9 and 28 are now brought into proximity to the opposite ends o! the tubes I9 and the electrode shells I6 are inserted into such opposite ends. 'I'he sockets 29 retain the electrode shells in spaced concentric relation to the tubev I8. The ends of the tube I0 are passed into the packing 24 within the chambers 23. The units I9 and 28 may be supported by any suitable means. The caps' 33 are now screwed up so that the follower rings 25 place the packing under compression and form vacuum-tight joints Iwith the tube I0. The coolant is properly circulated through the caps 33. The valve element 58 may now be in the position shown in Flgure 1, whereby the inner pocket 54 is empty |while the outer pocket 54 is lled with the mercury. The valve element 4l may now be inthe position shown in Figure l, whereby the port 44 is in communication with the hot air discharge port 45, while the port 48 is covered. The valve element 42 now covers port `40, while valve element 39 is open. Hot air is now supplied-through the pipe 38 and circulates through the glass tube l0 and discharges from the glass ltube through the pipe 45. This hot air thus substantially 400 C. This hot air bakes the dried iluorescent coating II in whole or' in part. The

pipe 38 leads baking.

plied to the top hl heated by the action of.

mg y the shell i3 and retainer plas.

with the hot air through' the pipe 45. It is advantageous to bake the coating in this manner, as the tubes are long and require a large furnace for The bakingy in accordance with my method does not plasticize the tube.

After the baking operation, Figure 2, the valve 39 is closed and valve 41 turned to cover Dort 44,

and valve 42 turned to the open position. The

interior of the glass tube l is no'w placed in communication with a source of vacuum and is suitably evacuated. During this evacuation, the electrode shells I 6 are connected with the opposite poles of the source of current, through the wires 82. This is done to heat the electrode shells` I6 and drive on undesirable gases and impurities. When the electrode shells I6 are thus connected with the opposite pole of the source of current, of a suitable character; they become highly heated and the tube l@ is heated, which aids in baking the coating H. This heating action of the electrode shells l5 is continued for a suitable length of time, indicatedby a small piece of paper contacting with the heated. tube 'l u becoming browned or partly charred. When this occurs, the electrode shells i6 are disconnected from the source oi current.

lAfter this and when the proper vacuum is at tained within the tube l E), Figure 3, the valve d2 is turned to cover the'port Il@ and hold the vacuum within the tube. Before the tube has materially cooled, a high frequency coil A is brought intoav position for surrounding the lower end of the tube and the lower electrode shell lo, and when the current is turned on, the coil will heat the electrode shell I'B and retainer I8 by induction. This electrode shell and retainer may be heated toy a high point and the heat radiating from the same vides a vacuum tight joint and the action may be aided by forming jaws if necessary.

The upper end 6| of the tube, Figure 8, is now` f severed by the blades B2.

will heat the adjacent portion 5l ofthe tube, and

this portion 'i'will be plasticized and drawn inwardly by the action of the vacuum within the,

tube 9E. This portion 51 Will be then become fused Ato the retainer i8 for forming a vacuumtight joint therewith. This action may be aided I by the use of forming jaws, if necessary.

`The lower end 53 of the tube, Figure d, is now severed from the tube by knives 59. Theseknives will not engage the clamp 29 which has a smaller diameter than the retainer i8, as shown in Fig ure 13. The valve i? is now turned to place the tube d6 in communication with the port M, to-supply a small amount of inert gas, such as'argon or neoninto thetube it, Figure 5. The amount of inert gas thus supplied issrnall and does not perceptibly change the degree or' vacuum in the tube. `The valve t1 is nowl turned to to cover the port de.

By this time, the temperature of the tube l0 is materially reduced and may be at approximately room temperature, Figure 6. The valve element Si! is now turned to introduce the measured amount of mercury into the port 55 and this mercury drops to the bottom of the tube lll. This measured amount of mercury is ordinarily a ball of slightly less than de" in diameter.

the neutral position The high frequency coil A, 'Figure 7, is now ai tube it adjacent to the electrode shell is the coil and the of the upper'electrode shell it, and this the tube. which within the tube I8. yThis 91'0- port'ion 6u of the vacuum the retainer Figures 8 and 9 show the complete lamp. The electrode shells I-6 arel arranged'within the opposite ends of the tube l0- and have their parts or retainers sealed therein to provide vacuumltight joints. The retainers I8 hold lthe electrode shells in spaced concentric relation to the tube I0. The contact extensions Il project outwardly beyond the ends of the tube IB, for engagement with the socket terminals, for supplying current to the lampl when in use.

When the electrodes embodying the cathode shells I6' and shown in Figures 10, 11 and 12, are used, the coil A heats principally the retainerl, which, in turn, heats and plasticizes thetube ill. All other steps of the method remain identical with those shown and described.

It is to be understood that the apparatus herewith shown and described is to be taken as a preferred embodiment of the same, and that various changes in the shape, size, and arrangementlof parts may be resorted to, and that changes may be resorted to in the orderl of the steps of the method, and in the shape, size and arrangement of parts of. the cathode units, without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

l. The method of making a coldcathode fluorescent lamp or the like, comprising supporting a glass tube having its opposite ends open and its inner surfacecoated with an unbaked uorescent inert gas into the tube, introducing mercury into the tube, heating the other electrode by induction and causing the same to heat and plasticize the adjacent portion of the tube and fusing such adjacent portion to the electrode, and cutting ou the outer adjacent portion of the tube.

2. The method of making a cold cathode nuorescent lamp or the like, comprising supporting a glass tube having its opposite ends open and its inner surface coated with an unbaked fluorescent compound, introducing electrodes into the tube near its ends and holding them generally concentric with relation to the tube, circulating hot air through the tube to bake the coating, evacuating the tube, connecting .the electrodes with a source of current to heat them and the tube to aidin the baking, heating the tube adjacent to one electrode to plasticize the same. and fuse it to the electrode, cutting oi the outer adjacent end of the tube, introducing an inert gas into the tube, introducing mercury into'the' tube, heating the'tube adjacent tc rthe other electrode to plasticize the same and yfuseit to such electrode, and

cutting off the outer portion ofthe tube.

3,"The method of making a coldy cathode fluorescent lamp or` the like, comprising supporting a .glass tube having its opposite ends open and its inner surface coated with an unbaked uorescent compound, introducing electrodes into the tube near its ends, the electrodes having retainers extending radially beyond the same, supporting the electrodes within the tube, circulating hot air through the tube to bake the coating, evacuating the tube, connecting lthe electrodes with a source of current to heat them and the tube to aid in the baking, heating the tube adjacent to one electrode to plasticize the same and fuse it to the retainer of such electrode, cutting off the outer end of the tube adjacent to such retainer, introducing an inert gas into the tube,` introducing mercury into the tube, heating the tube adjacent to thepther electrode to plasticize it and fuse the same'to the retainer of -such electrode, and cutting of! the outer portion of the tube adjacent to the retainer of the last named electrode.

4. The method of making a cold cathode fluo um-tight joint, iintroducing an inert gas into the Y open end of the tube, introducing mercury into the open end of the tube, heating the tube adiarescent lamp or the like, comprising supporting a glass tube having its opposite end s open and its inner surface coated with a fluorescent compound, introducing electrodes into the ends of the tube and supporting them near and spaced from such ends, evacuating the tube",l connecting the electrodes with a source of current during the evacuation, heating one electrode by induction and caus- V ing the same to heat and plasticize the adjacent portion of the tube and fusing such adjacent por- 5. In the method of making a cold cathode uo- I rescent lamp or the like, the steps of supporting a glass tube having its inner surface coated with a fluorescent compound and having its ends open, introducing into the open ends of the'tube electrodes having` radially enlarged bands, and concent to the other retainer toplasticize the tube and fusing the tube tothe retainer for forming a vacuum-tight joint, the retainers holding the electrodes spaced from the tube.

9. The method of making a cold cathode iiuorescent lamp or the like, comprising introducing into bodyv portions having chambers the open ends of a glass tube having its inner surface coated with an unbaked fluorescent compound,

- supporting within the' tube near itsends electrodes, introducing hot air into one chamber and circulating the same through the tube and discharging the hot air from the tube into` the other such adjacent portion to the electrode, introducing an inert gas into the tube through one chamber, introducing mercury into the tube through one chamber, and heating the other electrode by electrical induction and causing the same to heat and `plasticize the adjacent portion of' the tube and fusing such adjacent portion to the electrode.

necting one open end of the tube' with a source v of vacuum to evacuate the tube, heating the electrodes by electrical induction and causing them to heat and plasticize adjacent portions of the tube and fusing such adjacent portions to the bands for providing vacuum-tight joints.

(j. In the method. of making a cold cathode fluorescent lamp or the like, the steps of supporting a glass tube having its opposite ends open and its inner surface coated with a fluorescent compound, circulating hot airthrough the tube to bake the compound, supporting electrodes within the tube near its ends, and heating the electrodes by electrical induction and causing them to heat and plasticize the adjacent portions of the tube for fusing the adjacent portions to the cathodes.

7.`In the method of making a cold cathode fluorescent lamp or the like, the steps of supportend of the tube, heating the metal band by elec- 10. In the method of making a cold cathode fluorescent lamp or the likeI the steps of supporting a glass tube having one end open and its inner surface coated with a fluorescent compound, introducing into the open end of the glass tube a tubular electrode having a metal band extending .radially beyond the tubular electrode, evacuating the tube through the open end of the tube, heating the metal band by electrical induction and causing the metal band to heat and plasticize the adjacent portion of. the glass tube and fusing such adjacent portion of the glass tube to the metal band for providing a vacuum-tight joint, the metal band holding a tubular electrode spaced from the glass tube.

11. In the method ofmaking a nuorescent lamp or the like, the steps of supporting a glass tube having one end open and its inner surface' coated with a fluorescent compound, introducing into the open end of the glass tube an electrode having a metal band extending radially beyond the electrode, evacuating the tube through the open trical induction and causing the'metal band to heat and plasticize the adjacent portion of the glass tube and fusing such adjacent portion of the glass tube to the metal band for providing a vacuum-tight joint, the metal band holding the electrode spaced from the glass tube.

' CARL mzoo.