Title:
Apparatus for producing cold cathode fluorescent lamps or the like
United States Patent 2417361


Abstract:
My invention relates to apparatus, for producing electronic devices, such as gaseous discharge tubes including cold cathode fluorescent lamps, neon lamps, radio tubes or the like. An important object of the invention is to provide apparatus of the above mentioned character for the practice...



Inventors:
Carl, Herzog
Application Number:
US60257045A
Publication Date:
03/11/1947
Filing Date:
06/30/1945
Assignee:
Carl, Herzog
Primary Class:
Other Classes:
65/32.5, 65/43, 65/139, 65/154, 65/157, 141/8, 141/66, 285/41, 285/342
International Classes:
H01J5/42
View Patent Images:



Description:

My invention relates to apparatus, for producing electronic devices, such as gaseous discharge tubes including cold cathode fluorescent lamps, neon lamps, radio tubes or the like.

An important object of the invention is to provide apparatus of the above mentioned character for the practice of a continuous method for performing the various steps in producing the finished product, such as a cold cathode fluorescent lamp, and will reduce the manipulation of the tube to the minimum.

A further object of the invention is to provide an apparatus of the above mentioned character for the practice of a method which will eliminate the baking of the coating of the tube in a separate furnace.

A further object of the invention is to provide an apparatus which may be employed to evacuate the tube and seal in the electrode at the same time.

A furthqr object of the invention is to provide an apparatus which will materially reduce the cost of baking cold cathode fluorescent lamps.

A further object of the invention is to provide apparatus of the above mentioned character which will evacuate the tube through one end, and also introduce an inert gas and mercury into the tube.

A further object of the invention is to provide means for cooling the packing used to form the vacuum-tight joint.

A further object of the invention is to provide apparatus of the above mentioned character having means to connect the electrodes with the opposite pole of the source of current.

Other objects and advantages of the invention will be apparent during the course of the following description.

The present application is a division of my copending application for Method of and apparatus for making cold cathode fluorescent lamps or the like, filed March 7, 1944, Serial No. 525,446.

In the accompanying drawings forming a part of this application, and in which like numerals are employed to designate like parts throughout 4 the same, Figure 1 is a central vertical longitudinal section through apparatus embodying my invention, showing the baking steps, Figure 2 is a similar view through the tube, partly diagrammatic, showing the vacuum baking, Figure 3 is a similar view showing sealing the bottom end of the tube, Figure 4 is a similar view showing cutting off the bottom end of the tube, 5 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 top 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 9 is an enlarged central longitudinal section through the completed lamp, Figure 10 is a perspective view, parts broken away, showing a modified manner of mounting the cathode upon the contact extension of the retainer, Figure 11 is a similar view showing a further modified 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 away.

In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of my invention, the numeral 10 designates a glass tube, constituting the envelope of the cold cathode fluorescent. lamp. This tube may be of any suitable 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 10 is covered or coated with a coating composition containing a finely divided luminescent or fluorescent material, and this coating is dried. I may employ the coating composition disclosed in the patent to T.

M. Cortese, 2,318,060, and this coating may be 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 10, Figure 1, has the coating composition II, which may be the fluorescent coating composition disclosed in the Cortese patent, extending originally throughout its entire length, and dried but not baked, and this dried coating is removed from the ends of the tube 10 to points 12, leaving 0 clean or uncoated zones 13 and 14. The tube 10 with the dried interior coating 11 is vertically arranged with its opposite ends upon and held within a holder 15 to be supported thereby.

Disposed within the opposite ends of the tube 5.10 are electrodes, including electrode shells 16.

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 II of a retainer I 18, surrounding the electrode shell and spaced therefrom. The retainer 18 has a larger diameter than the electrode shell 16 and has a smaller diameter than the tube 10, and the tube is fused to the retainer, to provide a vacuum- l' tight joint, as will be explained. The retainer forms a ring or band extending radially beyond the electrode shell 16. If desired, the electrode shell 16 may be welded to the contact extension I . The retainer 18 is made of a special commer- 1 cial chrome-iron alloy which has the same expansion coefficient as glass. The retainer 18 and the contact extension I1 have their ends imperforate, as shown.

I also contemplate using the form of electrode 2 which is an integral unit, as shown in Figure 21 of my copending application for Method of and apparatus for producing cold cathode fluorescent lamps and to such lamps, filed January 26, 1944, Serial No. 519,666. 2 I may employ the electrode shown in Figure 10.

In this figure, 16' is an electrode shell, identical with the shell 16 and having a closed end 17', which is welded to a wire 18'. This wire is welded to the end of the contact extension 11 of the re- 3 tainer 18. The wire 18' supports the electrode shell 16' in spaced concentric relation to the contact extension I1 and the retainer 18.

In Figure 11, I have shown a slightly different arrangement wherein wires 19' are welded to the sides of the electrode shell 16' and to the bottom of the retainer 18. The arrangement is otherwise identical.

In Figure 12, I have shown a further similar arrangement, wherein a radial ribbon or strap 20' is welded to the end 17' of the electrode shell and extends outwardly beyond the same and is welded to the bottom of the retainer 18. The arrangement is otherwise Identical with that shown in Figure 10.

The advantage of the electrode shown in Figures 10; 11 and 12, is that the electrode shell is spaced from the contact extension 1 and retainer 18 and connected therewith by the wire or wires or ribbon and the amount of heat which is transmitted by conduction from the shell 16' to the contact extension or retainer 18 is reduced.

This is advantageous after the lamp has been made and is operating in use.

The electrode shell 16' corresponds to the electrode shell 16 and the same retainer and contact extension is used.

I will now describe the operating units of apparatus which is used in the practice of the method. The operating units are designated generally by the numerals 19 and 20. Each operating unit includes an outer block 21, 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 a mixture of the same, or any other suitable material for effecting a vacuum-tight joint with the glass tube 10. A follower ring 25 is movable into the chamber 23 to compress the packing 24. The 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. This socket 29 may be resilient. The shank 28 is electrically insulated upon the block 21 by an insulating sleeve 30. The shanks 28 are connected with the opposite poles of a source of current by lead wires 32, for a purpose to be described. Each reduced screw threaded extension 22 has a cap 33 mounted thereon and having screw-threaded engagement therewith, to shift the follower ring 25 and compress the packing. This cap is provided with a water space or jacket 34, and the0 coolant may enter at the pipe 35 and leave by the pipe 36.

The unit 20 is provided with a hot air port 31, leading into the chamber 26 and this hot air port is connected with a pipe 38, having a cut-off valve 39 connected therein. The pipe 38 leads to a source of hot air and the hot air is supplied through the pipe 38 so that it may enter the glass tube 10 at substantially 400" C. The unit 20 also has a vacuum port 40, in communication 0 with the chamber 26 and connected with a pipe 41, having a cut-off valve 42 connected therein.

The pipe 41 is connected with a source of vacuum.

The unit Is has a tube 43, connected therewith, and this tube communicates with a port 45, leading into the chamber 26. The tube 43 has a hot air discharge tube 45 and a gas inlet tube 46, connected therewith. A rotary valve 41 is arranged at the union of the tubes 43, 45 and 46, and may be manipulated to place tube 43 in )0 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 19 is provided in its upper end with a well 48 for holding mercury and has a tapered 35 recess 49 beneath the well to receive a tapered rotory valve element 50. This valve element is turned by a stem 51 having a crank 52 and is urged upon its seat by a spring 53. The valve element 50 has diametrically oppositely arranged 40 pockets 54, for receiving measured amounts of the mercury and discharging the same into an inclined port 55, leading into the chamber 26.

The well 48 is in communication with a vertical port 56 having a horizontal branch 51 which 45 leads into the recess 49 and feeds the mercury into the pocket 54. The vertical port 56 discharges at its lower end into a horizontal recess 51', arranged beneath the valve element 50 It is thus seen that the mercury contacts with the 50 upper and lower ends of the valve element 50 and seals these ends, whereby a vacuum-tight Joint is effected.

The practice of the method is as follows: I take the glass tube 10 having the dried un55 baked fluorescent coating II and its ends open, and insert the same in the holder 15, Figure 1 which vertically supports the tube. The electrode shells 16 are held by the sockets or clanps 29 by inserting the contact extensions 17 into these 60 sockets. The socket or clamp 29 has a smaller diameter than the retainer 18, as clearly shown in Figure 13. The units s1 and 20 are now brought into proximity to the e oppositeends of the tubes 10 and the electrode shells 16. are in65 serted into such opposite ends. The sockets 29 retain the electrode shells in spaced concentric relation to the tube 10. The ends of the tube 10 are passed into the packing 24 within the chambers 23. The units 19 and 20 may be supported by 70 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 with the tube 10. The coolant is properly circulated through the caps 33. The valve ele75 ment 50 may now be in the position shown In Figure 1, whereby the inner pocket 54 is empty while the outer pocket 54 is filled with the mercury. The valve element 47 may now be in the position shown in Figure 1, whereby the port 44 is in communication with the hot air discharge port 45, while the port 46 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 and discharges from the glass tube through the pipe 45. This hot air thus supplied to the glass tube has a temperature of substantially 400° C.

This hot air bakes the dried fluorescent coating I 1 in whole or in part. The baking treatment may continue for about half an hour. During this baking operation, any gases or the like liberated from the coating II pass out 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 baking. The baking in accordance with my method does not plasticize the tube.

After the baking operation, Figure 2, the valve 39 is closed and valve 47 turned to cover port 44, and valve 42 turned to the open position. The interior of the glass tube 10 is now placed in communication with a source of vacuum and is suit* ably evacuated. During this evacuation, the electrode shells 16 are connected with the opposite poles of the source of current, through the wires 32. This is done to heat the electrode shells 16 and drive off undesirable gases and impurities.

When the electrode shells 16 are thus connected with the opposite pole of the source of current, of a suitable character, they become highly heated and the tube 10 is heated, which aids in baking the coating 11. This heating action of the electrode shells 16 is continued for a suitable length of time, indicated by a small piece of paper contacting with the heated tube 10 becoming browned or partly charred. When this occurs, the electrode shells 16 are disconnected from the source of current.

After this and when the proper vacuum is attained within the tube 10, Figure 3, the valve 42 is turned to cover the port 40 and hold the vacuum within the tube. Before the tube has materially cooled, a high frequency coil A is brought into a position for surrounding the lower end of the tube and the lower electrode shell 16, and when the current is turned on, the coil will heat the electrode shell 16 and retainer 18 by induction. This electrode shell and retainer may be heated to a high point and the heat radiating from the same will heat the adjacent portion 57a of the tube, and this portion 57a will be plasticized and drawn inwardly by the action of the vacuum within the tube 10. This portion 57a will then become fused to the retainer 18 for forming a vacuum-tight joint therewith. This action may be aided by the use of forming jaws, if necessary.

The lower end 58 of the tube, Figure 4, is now severed from the tube by knives 59. These knives will not engage the clamp 29 which has a smaller diameter than the retainer 18, as shown in Figure 13.

The valve 47 is now turned to place the tube 46 in communication with the port 44, to supply a small amount of inert gas, such as argon or 7 neon into the tube 10, Figure 5. The amount of inert gas thus supplied is small and does not perceptibly change the degree of vacuum in the tube. The valve 47 is now turned to the neutral position to cover the port 44. 7 By this time, the temperature of the tube 10 is materially reduced and may be at approximately room temperature, Figure 6. The valve element 50 is now turned to introduce the measured amount of mercury into the port 55 and this mercury drops to the bottom of the tube 10. This measured amount of mercury is ordinarily a ball of slightly less than A" in diameter.

Another high frequency coil A, Figure 7, is now applied to the top of the tube 10 adjacent to the upper electrode shell 16, and this electrode shell is highly heated by the action of the coil and the heat radiating from the shell I6 and retainer plasticizes the adjacent portion 60 of the tube, which is drawn inwardly by the vacuum within the tube and becomes fused to the retainer 18.

This provides a vacuum tight joint and the action may be aided by forming jaws if necessary.

The upper end 61 of the tube, Figure 8, is now severed by the blades 62.

Figures 8 and 9 show the complete lamp. The electrode shells 16 are arranged within the opposite ends of the tube 10 and have their parts or retainers sealed therein to provide vacuumtight joints. The retainers 18 hold the electrode shells in spaced concentric relation to the tube 10. The contact extensions 17 project outwardly beyond the ends of the tube 10, for engagement with the socket terminals, for supplying current to the lamp when in use.

When the electrodes embodying the cathode shells 16' and shown in Figures 10, 11 and 12, are used, the coil A heats principally the retainer 18, which, in turn, heats and plasticizes the tube 10. 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 arrangement of parts may be resorted to, and that changes may be resorted to in the order 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, what I claim is; 1. In apparatus for making a cold cathode fluorescent lamp or the like, a pair of units, each unit comprising a body portion having a chamber to receive the open end of a glass tube, means carried by the body portion to effect a vacuum tight joint with the glass tube, means for supplying hot Sair to the chamber of one unit, means for discharging the hot air from the chamber of the other unit, means for connecting the chamber of one unit with the source of vacuum, means for supplying an inert gas to the chamber of one unit, and means for supplying mercury to the chamber Sof one unit.

2; An apparatus for making a cold cathode fluorescent lamp or the like, upper and lower units, each unit comprising a body portion having a 5 chamber to receive the open end of a glass tube, means to effect a vacuum-tight joint with the glass tube, means for supplying hot air to the chamber of the lower unit, means to discharge the hot air from the chamber of the upper unit, 'O means for connecting the chamber of the lower unit with the source of vacuum, means for supplying an inert gas to the chamber of the upper unit, the body portion of the upper unit having a well for holding mercury and a recess, a valve 6 element to turn within the recess and having a pocket for receiving mercury, the last named body portion having a recess below the valve element and a port connecting the recess with the well, such body portion, hving a port leading from the valve element to the chamber of the upper unit, the arrangement being such that the opposite ends of the valve element are sealed with mercury, and means carried by the body portion of each unit for supporting an electrode within the tube. 1' 3. An apparatus for making a cold cathode fluorescent lamp or the like, comprising a unit having a body portion, said body portion having a chamber to receive the end of the glass tube, packing arranged within the chamber to engage 1 with the tube, a cap having screw-threaded engagemeit with the body portion to compress the packing, said cap having a cooling jacket, and means carried by the body portion to support an electrode within the tube. 2 4. In apparatus for making a cold cathode fluorescent lamp or the like, a body portion having a chamber to receive the end of a glass tube, means to effect a vacuum-tight joint with the tube, said body portion having a well for holding 2 mercury and a recess beneath the well, a turning valve within the recess to be turned therein and having a pocket, the body portion having a space beneath the valve element and a port extending between the well and space, the last named port 3 having a part leading to the recess, said body por-, tion also having a port extending from the recess to the chamber, and means to evacuate the tube when its end is held within the chamber.

5. In apparatus for making an electronic de- 3 vice from a tube having an open end, a substantially vertical member provided with a chamber having a lower enlarged portion to receive the open end of the tube, means arranged within the lower enlarged portion to form a vacuum tight joint with the tube, means for supplying mercury into the side of the chamber above the lower enlarged portion, a device mounted upon the member and extending axially through the chamber and outwardly of the chamber and member and including a socket at its free end to receive an electrode, said socket holding the electrode in spaced concentric relation within the tube, the arrangement being such that the tube may be heated and plasticized exteriorly and fused to the electrode, and means to evacuate the tube and to supply an inner gas to the same.

6. In apparatus for making a cold cathode fluorescent lamp or the like from a tube having an open end, a body portion having a chamber provided with an open end to receive the open end of the tube, means engaging the tube for forming a seal, a metallic member mounted upon the body portion and passing through the closed end of the chamber and extending axially of the chamber and including a socket disposed outwardly of the chamber and member, said. socket extending axially of the tube and holding an electrode in the tube, the arrangement being such that the tube may be heated and plasticized exteriorly of the member and fused to the electrode, means to connect the outer end of the metallic member with a source of current, and means to evacuate the tube.

7. In apparatus for making a cold cathode fluorescent lamp or the like from a tube having its opposite ends open, spaced operating units having chambers for receiving the open ends of the tube, means for forming seals with the opened end portions of the tubes, metallic devices mounted upon the units and extending axially through the chambers and including electrode holding elements which are arranged exteriorly of the chambers and units, the arrangement being such that the tube may be heated and plasticized exteriorly of the units and fused to the electrodes, means to connect the metallic devices withithe opposite poles of a source of current, and means to evacuate one chamber. ) 8. In apparatus for making a cold cathode fluorescent lamp or the like from a tube having open ends, spaced opposed operating units having chambers which are closed at their outer ends and open at their inner ends to receive the open ends of the tube, one unit having means to supply mercury into its chamber, packing arranged within the inner ends of the chambers and engaging the tube, nuts having screw threaded engagement with the units for compressing the o packing, members mounted upon the units and passing through the closed ends of the chambers and extending axially of the chambers and including sockets disposed outwardly of the chambers and units, said sockets holding electrodes 5 within the tube, the arrangement being such that. the tube may be heated and plasticized exteriorly of the units and fused to the electrodes, and means to evacuate one chamber.

9. In apparatus for making a cold cathode fluo0 rescent lamp or the like from a tube having opposite open ends, spaced opposed operating units having chambers having outer closed ends and inner open ends to receive the open ends of the tube, means for forming seals with the open end 35 portions of the tube, devices mounted upon the units and extending axially of the chambers and including electrode holding units arranged outwardly of the chambers and the first named units, the arrangement being such that the tube may 40 be heated and plasticized exteriorly of the first named units and fused to the electrodes, and means to evacuate one chamber.

10. In apparatus for making a cold cathode fluorescent lamp from a tube having both ends 45 open and its interior provided with a fluorescent coating, said apparatus comprising spaced operating units having chambers for receiving the open ends of the tube, means for forming vacuum tight joints with such open ends, metallic mem50 bers carried by, the units and extending axially within the chambers and into the open ends of the tube for holding electrodes within the tube and spaced from each other, means to evacuate one chamber while the adjacent end of the tube 53 is open, and means to connect the metallic members with the opposite poles of a source of current during the evacuation period and while such adjacent end is open so that the electrodes become highly heated for driving off undesirable 60 gasses and impurities.

11. In apparatus for making a cold cathode fluorescent lamp from a tube having both ends open and its interior provided with a fluorescent coating, said apparatus comprising spaced oper65 ating units having chambers for receiving the open ends of the tube, means for forming vacuum tight joints with such open ends, metallic members carried by the units and extending axially within the chambers and into the open ends 70 of the tube for holding electrodes within the tube and spaced from each other, means for supplying heated air into one open end of the tube through one unit and discharging the same from the opposite open end of the tube through the 75 Qther unit to bake the coating, means to evacuate one chamber while the adjacent end of the tube is open, and means to connect the metallic members with the opposite poles of a source of current during the evacuation period and while such adjacent end is open so that the electrodes become highly heated for driving off undesirable gases and impurities.

12. In apparatus for making a cold cathode fluorescent lamp from a tube having both ends open and its interior provided with a fluorescent coating, means for forming vacuum tight joints with such open ends, metallic members carried by the units and extending axially within the chambers and into the open ends of the tube within the chambers for holding electrodes within the tube and spaced from each other, means to evacuate one chamber while the open ends of the tube are within the chambers, and means to connect the metallic members with the opposite Poles of a source of current while the open ends of the tube are within the chambers.

CARL HERZOG.

REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS Number 2,313,657 2,374,304 2,326,296 2,006,818 2,078,892 2,215,655 Name Date Marshaus --------- Mar. 9, 1943 Owings --..-- - Apr. 24, 1945 Harrison et al. ------ Aug. 10, 1943 Zimber --------- July 2, 1935 McCullough .---_-- Apr. 27, 1937 Stewart ------------ Sept. 24, 1940