US 3749467 A
Fluorescent lamps which are manufactured by a process in which the lamp envelope, during one step of the process, is exhausted through both ends simultaneously thereby avoiding unnecessary contamination within the lamp envelope. In a preferred embodiment of the process, the electrodes are activated outside of the lamp and the contaminants removed to prevent them from contaminating the lamp. A lamp is also disclosed in which the end caps have electrical contact members mounted directly thereon through which the lamp is to be connected to a fixture to supply current to the lamp, and in which the mounting leads for the cathode of each end cap are connected directly to these electrical contacts. The end caps are also formed to accept an end of the envelope of a fluorescent lamp for direct attachment thereto. In a further embodiment of the invention an end cap is provided having a tubulation which can be sealed by infra-red energy.
Description (OCR text may contain errors)
United States Patent Emidy et a].
[451 July 31, 1973  FLUORESCENT LAMPS AND METHOD OF 732,439 6/1955 Great Britain 316/21 MANUFACTURING THE SAME  Inventors: Thomas J. Emidy, Morris Plains; g f i, w i i Lanham Donald P. Northrop, Glen Rock; i g g we Luke Thorington, Berkeley Heights; omey at y at y Andrew Henry Olsen, Jersey City, all of NJ.  ABSTRACT  Assigneei Dumqest Corporation North Fluorescent lamps which are manufactured by a pro- Bergen NJ cess in which the lamp envelope, during one step of the process, is exhausted through both ends simultaneously  Filed: 1971 thereby avoiding unnecessa contamination within the ry  APPL 124,311 lamp envelope. In a preferred embodiment of the process, the electrodes are activated outside of the lamp and the contaminants removed to prevent them from  U.S. CI. 316/19, 3l 3/lO9 contaminating the lamp A lamp iS also disclosed in  1 9/18 which the end caps have electrical contact members  Fleld of Search 316/18, 19, 24, 12, mounted directly thereon through which the lamp is to 316/15; 53/7, 9, 39; 313/109; 29/25.1l, 25-17 be connected to a fixture to supply current to the lamp, and in which the mounting leads for the cathode of  References Clted each end cap are connected directly to these electrical UNITED STATES PATENTS contacts. The end caps are also formed to accept an 2,465,062 3/1949 Clack 316/21 x end of the envelope of a fluorescent p for direct 3,551,725 12/1970 Brundige tachment thereto. In a further embodiment of the in- 3,215,892 11/1965 Waymouth 313/109 X vention an end cap is provided having a tubulation which can be sealed infra-red energy.
1,015,802 12/1963 Great Britain 316/19 19 Claims, 7 Drawing Figures 100 CLEAN ENDS I02 L COAT 0F BULB END CAPS END CAPS PSE EJEE f BAKE /\/'O4 PSE S EIEE PREESURED C PRESSURE JVIOG- PRESSURE V no r 2 ACTIVATE CATHODE FLUSH WITH 1,- I08 ACTIVATE CATHODE 124 a FLUSH AT MERCURY INERT GAS-REDUCE a FLUSH AT REDUCED PRESSURE TO LAMP PRESSURE REDUCED PRESSURE (I24 n2 ES P RES S'iI RE ASSEMBLE PES SiJ RE 222 2 126 I28 I28 I26 f N 1am; PRESSURE AIR PRESSURE AIR Us g flg ATMoSPHERE' ua PAliimiuJmausn 3,749.46?
sum 3 or 3 com AND LEHR BULBS SEAL lN 2m SUPPLY SUPPLY END cAPS OF 1 END CAPS END CAPS VACUUM EXHAUST 2'6 AND BAKE FLUSH AND 2l8 V FILL w|TH INERT GAS 8 TH 220 ELECTRODES PUMP DOWN TO OPERATING 222 PRESSURE f ADD MERCURY 224 IR SEAL TUBULATlONS" CONDUCT To 22a ATMOSPHERE SUPPLY ATTACH SUPPLY BASE BASE BASE FLUORESCENT LAMPS AND METHOD OF MANUFACTURING THE SAME Conventional fluorescent lamps utilize a structure at each end thereof for holding the cathode or electrode and for supplying current to the lamp. In a conventional electrode structure, a glass stem is provided which has a flared lower end which is sealed to the inner surface of the lamp envelope. In one type of lamp, the stem at one end of the envelope also includes an opening which communciates with the interior of the lamp envelope. The opening is the termination of an exhaust tube, or tubulation, which has a tip which extends outside the lamp envelope. In some lamps a stem with a tubulation is used at each end of the envelope.
In conventional lamps the stem also holds a pair of lead wires which are connected on the end of the stem opposite from the flare to a pair of mounting members to which the cathode is electrically connected. These lead wires extend out of the flared end of the stern. A base is also provided having external contact pins to which the lead wires are connected and which are used to connect and hold the lamp in a fixture.
In accordance with conventional manufacturing processes for prior art lamps with stems, one or both of which has a tubulation, the lamp is normally exhausted of air through one of the tubulation members at an end of the envelope, even though the lamp may have two such tubulation members. The lamp is also filled with mercury and the necessary fill gas through one of the tubulations and one or both tubulations, depending upon the lamp structure, is then sealed or tipped off. A base is then sealed to each end of the lamp.
The present invention is directed to novel types of fluorescent lamps and processes for making the same. In accordance with the invention, several processes are disclosed for the manufacture of fluorescent lamps in which the lamp envelope is exhausted, then flushed and filled with gas through both ends of the lamp envelope simultaneously. This results in a faster and cleaner exhaust and filling operation since any impurities in the envelope do not travel the complete length of the envelope. In addition, the lamps utilize novel end cap structures which, in a preferred embodiment of the invention, are formed to have the contact pins and lead wires for the cathode directly thereon. These end cap structures also are constructed so as to accept an end of the envelope of the fluorescent lamp so that it can be held to the end cap. The preferred embodiment of process of manufacturing lamps using these end caps is such that the cathodes can be activated external to the envelope during processing, thereby avoiding contamination of the lamp. In addition, an end cap is disclosed having a tubulation with the tubulation being formed of an infra-red energy absorbing glass so that the tubulation can be sealed by radiant heating.
It is therefore an object of the present invention to provide novel fluorescent lamps and methods of mak ing the same.
Another object is to provide methods for manufacturing fluorescent lamps in which the lamp envelope during processing is filled and exhausted simultaneously through both ends of the envelope.
An additional object is to provide a novel process for manufacturing lamps in which the cathodes are activated external to the envelope to avoid contaminating the envelope.
Another object is to provide end caps for fluorescent lamps in which the electrical contacts for the lamp and the cathode mounting leads are mounted directly to the end cap.
A further object is to provide fluorescent lamps the ends of whose envelopes are directly attachable and scalable to end caps which have electrical contact members and cathode mounting leads fastened directly thereto.
A further object is to provide an end cap for fluorescent lamps in which the tubulation member is formed of an infra-red absorbing material.
Yet another object is to provide an end cap for fluorescent lamps having contact members and cathode mounting leads connected directly, in which a tubulation member is also formed directly in the end cap.
Other objects and advantages of the present invention will become more apparent upon reference to the following specification and annexed drawings, in which:
FIG. 1 is a flow diagram of a preferred embodiment of one process for making a lamp in accordance with the subject invention;
FIG. 2 is a side elevational view, partially in crosssection, of a lamp manufactured in accordance with the process of FIG. 1, using a preferred form of end cap;
FIGS. 3 and 3A are a side elevational view and top view respectively taken partially in cross-section showing another embodiment of end cap for use with lamps manufactured in accordance with the process of FIG.
FIG. 4 is a flow diagram of another process for making fluorescent lamps in accordance with the subject invention;
FIG. 5 is a side elevational view of a lamp using an end cap which is manufactured in accordance with the process of FIG. 4; and
FIG. 6 is a side elevational view of another form of end cap for use with the process of FIG. 4.
FIG. 1 is a flow diagram of a preferred embodiment of the process for the manufacture of fluorescent lamps. FIG. 2 shows a portion of one form of lamp manufactured according to the process of FIG. 1 having a novel end cap with cathode structure. The end cap structure is described before describing the process of FIG. 1.
The end cap of FIG. 2, includes a circular base 30, of glass or other suitable material which is formed with a pair of upstanding bosses 32 and 34 on the inner surface thereof. Electrically conductive cathode mounting leads 36 and 38 are respectively located in the bosses 32 and 34. Each mounting lead has a slit 36 and 38 in the top end thereof. The ends of filament 40 are located in the slits 36 and 38 which are then crimped to make the electrical contact.
The lower ends of the leads 36 and 38 are of somewhat larger diameter and are located in holes or circular grooves 45 in the bottom of the base to serve as the contact pins. Thus, a simple construction is provided where the cathode leads and contact pins are formed as one-piece units. In assembling the cathode leads and the contact pins to the end cap, it is only necessary to push the cathode mounting ends first through the holes in the bosses 32 and 34. When they are in position with the shoulders of the enlarged diameter portions against the top wall of the circular grooves 45, the members 36 and 38 are then sealed to the base by a suitable sealant, for example, glass frit.
As shown in FIG. 2, the circumferential portion of the base is formed with upstanding walls 54 and 55 defining a groove 56 therebetween. The outer wall 54 is of a greater height than the inner wall 55. Also, the outer wall 54 has a tapered inner edge 57 which is shaped to conform to a shouldered down curved portion 60 on the end of a bulb 62 of a fluorescent lamp. This shouldered down curved portion 60 terminates in an end 64 which rests on the bottom wall of the groove 56. The curved end 60 of the bulb fits in the groove 56, and the solder material is applied therearound to seal the bulb to the end cap by a conventional lamp sealing process.
Referring now to FIG. 1, the process for making the lamp of FIG. 2 is described. While the process can be carried out one lamp at a time, it is preferred that the process be sequential so that a plurality of bulbs for the lamps are sequentially fed into the input of the process and the completed lamps sequentially come out of the output end of the system. Also, the process is such that assembled end caps holding the cathodes are also supplied to the system at the same time. The equipment for performing the sequential process is not described in detail. However, in general, it includes a plurality of chambers having different pressures and/or gases through which the lamps are conveyed on a suitable conveyor system. The chambers are such that the various operations required can be carried out with the lamps in the chamber, i.e., gas flushing, attaching of end caps, etc., either manually or automatically. The necessary air locks, buffer chambers, etc., are present between the chambers. These are conventional.
As a first step 100 in the process of FIG. 1, the interiors of the bulbs are coated with the desired phosphor mix. Next, in step 102, the ends of the bulbs are cleaned off so that the end caps can be attached to the ends of the bulb and sealed thereto. This cleaning is accomplished in any one of a number of ways, for example, by brushing the phosphor off the ends of the bulbs. Steps 100 and 102 can be carried out for a number of bulbs either sequentially or in a batch operation. The bulbs with the clean ends are then processed sequentially into a baking oven 104 to bake out the phosphor binders.
in step 106, the bulbs are subjected to a reduced pressure environment, of less than atmospheric pressure. This is accomplished, for example, by a reduced pressure chamber with an air lock at the input end. Both ends of the bulb being processed are completely open and the reduced pressure is applied to both ends of the bulb simultaneously. This speeds up the process of exhausting as compared with a conventional process in which stems with tubulations with more restricted areas are used. Further, any impurities within the bulb are removed from both ends which results in a faster impurity removal and prevents any impurities from travelling the complete length of the bulb, as is done in lamps with one tubulation or two tubulations, where the stem or stems are attached prior to the exhaust step and exhausting is accomplished only through one end.
In step 108, the bulbs at reduced pressure from step i 106 are flushed with an inert gas such as argon or combination of argon-neon or argon-nitrogen, initially at the same pressure as in step 106, which is less than atmospheric pressure. In step 108, the pressure of the flushing gas is further reduced until the normal operating pressure of the finished lamp, for example, 3mm, is reached. If desired, this can be carried out in a twostep, two-chamber process, rather than in a single chamber in one step. The flushing gas is left in the envelope to provide the operating fill gas for the lamp. If desired, step 106 can be carried out with one inert gas and the fill gas introduced separately in step 108.
With the envelope at the normal operating pressure and with its fill gas, mercury is added to the lamp as shown in step 110. The mercury can be added in any of a number of ways. For example, a small ampule of mercury can be dosed directly into an open end of the lamp. As another alternative, a mercury giver" in the form of a mercury compound or amalgam can be introduced into the lamp after step 108. Such mercury givers then require that the envelope be heated to break down the compound or amalgam. As another alternative, the fill gas which is introduced into the lamp in step 108 can be laden with mercury. If the pressure is reduced down far enough, for example to about 6 microns, the mercury will vaporize to produce the required amount of free mercury. All of these various arrangements for introducing mercury into the lamp are incorporated in step 110.
Considering now the manner in which the end caps for the lamp are processed, two simultaneous process chains running along the drawing horizontally, are shown. This indicates an end cap for each end of the lamp bulb. The feeding of the end caps is preferably also sequential, in step with the processing of the bulbs. The assembled end caps, for example of the type of FIG. 2, or preferably de-gassed in a separate operation prior to being placed into the lamp process stream. The de-gassed caps are first subjected to a reduced pressure environment in step of less than normal atmospheric pressure. This can be accomplished in a chamber with an air lock input. The end caps are then flushed with an inert gas, such as nitrogen or argon, and the pressure is further reduced. This can be accomplished in another chamber.
The cathodes of the end caps are then activated in step 124 by the application of a suitable electric current through the cathodes at a point external, or remote, from the lamp envelope. This boils off the impurities from the cathode. The impurities from the cathodes cannot in any way contaminate the lamp at any subsequent stage of process since they are removed before the caps are applied to the envelope. This, of course, is a decided advantage. During and after activation the cathodes are also preferably flushed with an inert gas, at a further reduced pressure from that of steps 120 and 122.
After activation and flushing of the impurities, the end caps are subjected in step 126 to an atmosphere of the same inert gas used as the lamp fill gas. The pressure of the inert gas is further adjusted in step 128 to approximate that of the fill gas operating pressure, which is the same pressure as in step 108. Step 128 for the end caps serves as a buffer between the end cap processing and the bulb processing.
The end caps are assembled to the lamp bulbs in step 112. As indicated previously, the bulbs coming out of step 108 already are at the proper operating pressure, have the desired fill gas and have already been dosed with mercury. Similarly, the end caps from step 128 have been degassed activated, flushed, and are in an environment at the same pressure of the same fill gas as in the bulbs.
In step 112, an end cap is attached to each end of the lamp bulb, and fastened to it by a suitable sealing technique, such as described previously with respect to FIG. 2 and as is described subsequently with respect to FIG. 3. Since the contact pins are already attached to the end caps, a lamp which exits from step 112 is a complete fluorescent lamp, and the electrode structure has already been activated in step 124.
To complete the processing, the pressure of the chamber environment is increased in step 114 closer to atmospheric pressure, to act as a buffer to the air. The lamps are then subjected to an air pressure environment which is somewhat below that of atmospheric pressure in step 116, and finally to air at atmospheric pressure in step 118. In this step, they can be processed in the normal manner for shipping.
FIGS. 3 and 3A show another embodiment of end cap and lamp according to the present invention. The end cap uses a circular glass button of a glass compatible for sealing with that of a fluorescent lamp tube 12. The latter can be, for example, of lime glass. Thus, the button 10 also can be of lime glass or other material which is compatible for sealing to the fluorescent tube. Button 10 has an outer diameter which is greater than the outer diameter of the lamp bulb 12.
The glass button 10, which is to be sealed to each end of the tube 12, has an annular groove 14 which is tapered from the top down, as shown. The taper is such that the width of the bottom wall 15 of the annular groove is approximately equal to the thickness of the envelope 12 to which the electrode structure is to be attached. The wider portion at the top of the groove 14 is for the purpose of permitting an amount of a glass solder material, such as glass frit, to be placed therein to seal the end of the bulb 12 to the end cap.
A pair of cathode mounting members or leads, 18 and 19, of electrically conductive material, are held in circular depressions 20 formed in the top surface of the button by a suitable material such as solder glass frit 21. The leads can be of any conventional material. It has been found that an alloy such as Sylvania 4, manufactured and sold by the Sylvania Electronics Division of General Electric and Telephone, operates satisfactorily. The cathode leads 18 and 19 terminate in respective electrically conductive contact members 22 and 24 which can be of a solid rather than a hollow construction as is used with conventional bases which have metallic solder-type contacts. The portion between the leads 18 and 19 and the respective contacts is of slightly greater diameter than that of the leads 18 and 19, to give the leads added strength. As should be apparent, the lead-contact pin structure can be made of a one piece solid construction.
To assemble the cathode-contact pin structure to the glass button 10, the ends of the leads 18 and 19 are inserted through holes 25 in the button. The cathode mounting leads 18 and 19 are then sealed into the depressions 20 with the sealing material 21. This holds the entire structure to the cap. After this is done, a filament 26 is then mounted across the ends of the cathode mounting leads l8 and 19 in a conventional manner. The end cap is now ready for sealing to the end of a bulb 12 to form the complete lamp.
Lamps constructed in accordance with the process of FIG. 1, and having the end caps shown in FIGS. 2 and 3, have several advantages. First of all, since there are no stems used with flared ends for the end caps, the arc stream has a longer arc length when the lamp is operated. In general, if the length of the arc stream in a conventional manufactured tube is 44 inches, about 1% inches would be added in the lamps of the present invention, thereby giving an arc stream of approximately 45 H2 inches. By doing this, the lamp output in a conventional lamp can be increased by approximately lumens in a conventional 4 foot T 12 fluorescent lamp. The end losses of light are also considerably reduced since there is no light trapping behind a flare of a stem portion. Also, if desired, the inner surface of the end cap can be made light-reflective to further increase the light output.
The process of making lamps in accordance with the invention is simplified from conventional processes since three major areas of the latter are eliminated. These are: the conventional sealing of the stem to the lamp; exhausting of the tube through the tubulation of the stem; and basing of the contact members to the stems after the interior of the lamp has been processed. This speeds up the processing. Further, since the tubes are flushed and filled with gas through two full open ends, there is less tendency to blow phosphor off the tube wall as happens when gas is introduced and exhausted through a small tubulation. The free flow of gas through the two open ends of the bulb also speed up the processing.
As an another advantage, since the electrodes are pre-treated prior to fastening them into the envelope, there is less chance for sputtering of electrode material into the tube. In addition, the electrode structures are considerably simpler; that is, they are tipless, flareless and stemless, meaning that they are less subject to breaking.
The end caps of FIGS. 2 and 3 of the present invention have, in themselves, several advantages. As indicated before, the contact pins of the end caps are slotted and then they can be stamped or pressed together with the cathode leads as a one-piece unit, rather than providing lead wires through a flared stem and using a conventional base which is later connected to the leads which come out of the standard stem. As should be apparent, this is considerably different from and more economical than prior art electrode end cap structures. If desired, the inner surface of the end caps of FIGS. 2 and 3 also can be coated with a heat (infra-red) reflecting material. This will keep the ends of the lamp cooler.
While a glass-to-glass seal has been shown for the end cap to the bulb in the form of glass frit, other seal material can be used. For example, suitable plastics such as polyamide resins, indium-tin solders, etc., can be used.
The end caps can also be made of materials other than glass; for example, suitable plastic or ceramic materials. Suitable plastic materials which can be used are teflon and viton. End caps of these materials can be snapped over or screwed onto the ends of the envelope and coated with a suitable sealant. The plastic or other material used for the end caps must be resistant to the metals used in the operating lamp, and also must be able to resist ion bombardment. Metal end caps are not as advantageous as caps made of an insulating material, since, if metal is used, some other insulating material has to be used to insulate the contact pins from the remainder of the metal end cap.
FIG. 4 shows a flow diagram for a process for manufacture of fluorescent lamps in accordance with another embodiment of the invention in which different types of end caps and electrode structures are used. Here again the process is a sequential one in which the bulbs and the end caps or electrode structures are fed sequentially to an assembly point where they are assembled at a predetermined time in the processing cycle to form the completed fluorescent lamps.
Before describing the process of FIG. 4, reference is made to FIG. 5 which shows one form of end cap structure which can be used with this process. The end cap of FIG. 5 is similar in some respects to that shown in FIG. 3. Therefore, the same parts are given the same reference numerals and are not further described. Here, in FIG. 5, a hole 70 is formed in the glass button and a tube of infra-red sealing material 74 is fastened within thehole to seal it by any suitable material, such as a glass solder material 76, on the inner surface of the end cap. The tube 74 is made of an infra-red type glass, which absorbs infra-red energy and melts in response to receiving a sufficient quantity of infra-red energy. It need extend only a very short distance into the envelope. The electrical contact pin and cathode structure is the same as for the end cap of FIG. 3.
Referring again to FIG. 4, the first step in the manufacture of the lamps is shown by block 210 which is the coating of the bulbs with any desired phosphor mix in a conventional manner and the cleaning of the bulb ends takes place. The coated bulbs are then lehred, by running them through any of the necessary ovens so that the phosphor will completely adhere to the inner surface of the bulbs.
Two 'blocks 214 are shown, one on each side of the vertical flow path in FIG. 4 to illustrate that one end cap is supplied for assembly to each end of a bulb in step 212. In step 212, the end caps of the type shown in FIG. 5, or of some other suitable type, are sealed into the ends of the bulb at atmospheric pressure. This is accomplished, for example, by using glass frit to solder an end cap to each end of a bulb.
The bulbs with the end caps sealed in are next conducted to a vacuum environment, such as a chamber with a suitable air lock input. In this step 216, they are exhausted through the tubulations 74 at both ends of the lamp simultaneously. The pressure used during the exhaust step is approximately in the order of l micron and the temperature is at about 400500C. The bulb is baked in this step at this temperature for an amount of time sufficient to bake out all impurities. It should be understood that since both ends of the bulb are open through the tubulations 74 at the time the vacuum is being applied, the exhaust of all the impurities within the bulb occurs through both ends of the bulb rather than through one end as in a conventional exhaust process. Thus, there is no problem of entrapping impurities within the bulb or causing the impurities to travel the complete length of the bulb.
The bulbs pass out of the vacuum in step 216 and are next flushed in step 218 with an inert gas. The pressure of the inert gas in step 218 is substantially atmospheric pressure. The gas used in step 218 is to eventually be the till gas. If desired, a buffer step of inert gas, such as argon, at a suitable pressure, such as for example somewhere between atmospheric pressure and lamp operating pressure, can be used between steps 216 and 218.
In step 220 the electrodes are electrically activated to give ofi any decomposition products, which are impurities, that may be present. At the same time the activation is taking place, the lamp is also subjected to a pumping down operation in an argon, or other gas fill mixture, environment where the gas is pumped down to the desired fill pressure, for example, about 3 millimeters. This pumping down is effected through the two tubes 74. While the cathode activation and pumping are shown as two separate steps, it should be under stood that they can be carried out at the same time the lamp is being exhausted simultaneously with the activation.
The decomposition products produced by the cathode activation are exhausted through the tubulations of the end caps of the lamp. As indicated before, these decomposition products also simultaneously pass out through both ends of the lamp due to the respective tubulations rather than passing out through only one end of the lamp where they might have a better opportunity to contaminate other portions of the lamp.
The pumped down lamps, which have approximately the fill gas pressure needed for operation and with the activated electrodes, are then dosed in step 224 of the process with the correct amount of mercury. The mercury can be added through the tubulation 74 of either end cap of the lamp.
After the mercury has been added, in step 226 infrared energy is focused upon the tips of the tubulations 74 of both end caps. Since the tubulations 74 are made of infra-red energy responsive glass, the infra-red energy melts the glass and seals the tubulations. At this time, the internal processing of the lamp is completed.
The lamp is then conducted to the atmospheric pressure in step 228. Since the end caps have the contact pins attached directly to them, there is no need to apply bases to the lamp.
Lamps processed in the manner of FIG. 4 with the end caps of FIG. 5, have many of the advantages of the lamps made with the end caps of FIGS. 2 and 3 according to the process of FIG. 1. For example, the end caps are attached directly to the lamp tube and no bases or stems are needed. However, the cathodes are activated while sealed into the lamp envelope instead of being activated external to the tube.
The process of FIG. 4 also can be used'with an electrode structure of the more conventional type including a stem and base. An electrode structure of this type is shown in FIG. 6 which is conventional except that the tubulation is made of infra-red energy responsive glass such as is used for the tubulation 74 of the end cap of FIG. 5.
The electrode structure 80 of FIG. 6 includes the usual stem 81 with a flared lower end 82 which is to be sealed to the inner surface of an end of the lamp bulb. A tubulation 84 is located within the stem. The tubulation has a hole 86 at the upper end of the stem 81 and a tip end 88. A cathode shown in the form of a coiled filament-cathode 90 is mounted to the stem by leads 91 and 92. The leads 91 and 92 are sealed in the stem and extend through the bottom end of the stem for connection to the contact members of a base which is to be mounted to the end of the tube. v
The electrode structure 80 of FIG. 6 is used in the process of FIG.-4 in the same manner as the end cap of FIG. 5. The lamp is processed as previously described with the exception of step 212 where the stems are sealed into each end of the tube instead of sealing the end caps to the tube. Here, infra-red energy is focussed in step 226 to seal the tips 88 of the two tubulations on the lamp. in addition, a step 230 is added to the process where conventional bases are supplied in step 232, one to each end of the lamp. A base is fastened to each end of the tube over the tip end 88 of each tubulation. The leads 91 and 92 are electrically connected to the contact pins on the base, the contact pins being used to connect the lamp to a fixture. As should be apparent, in this process also the lamp tube is exhausted through both ends simultaneously to reduce the contaminants in the lamp.
What is claimed is:
1. A process for manufacturing fluorescent lamps comprising the steps of:
placing a tube coated with phosphor material within a low pressure chamber with both ends of said tube being left open so as to exhaust the tube simultaneously through both ends to remove contaminants,
providing a pair of end caps each having a cathode,
one for each end of said tube, electrically activating and degassing each said cathode at a location remote from said chamber to remove the contaminants from said cathodes, and
assembling the end caps to the ends of said tube to seal the same.
2. A process as in claim 1 further comprising the step of flushing the lamp through both ends with an inert gas before the cathodes are assembled thereto.
3. The process of claim 2 wherein the inert gas used for flushing is the fill gas to be used with the lamp and further comprising the step of reducing the pressure of said gas to substantially the operating pressure of the fill gas in the completed lamp.
4. The process of claim 3 further comprising the step of adding an ionizable medium to the lamp before the end caps are sealed thereto.
5. A process as in claim 1 further comprising the step of subjecting each end cap and its cathode after the cathode is activated to the fill gas at the operating pressure of the lamp and sealing the end cap to the lamp in an environment of said fill gas at said operating pressure.
6. The process of claim 1 further comprising the step of introducing an ionizable medium directly into an open end of the tube.
7. The process of claim 1 further comprising the step of adding a compound containing an ionizable medium into said tube and subjecting the tube to a temperature sufficient to break down the compound into the ionizable medium.
8. The process of claim 1 further comprising the steps of adding an ionizable medium into the fill gas, thus introducing the fill gas into said tube before the end caps are sealed thereto and reducing the pressure of the tube to vaporize the ionizable medium.
9. The method according to claim 1 further comprising the step of filling said chamber with argon gas and mercury vapor to the desired pressures for operating the lamp prior to scaling the end caps to the tube.
10. A process for manufacturing fluroescent lamps comprising the steps of coating the interior of an envelope with a phosphor, providing an end cap having a cathode for each end of the envelope, filling in a first chamber the envelope with a fill gas and an ionizable material, activating the cathode of each end cap while remote from the first chamber and removing the impurities liberated by activation, and sealing an end cap to each end of the envelope.
11. A process for manufacturing fluorescent lamps comprising the steps of:
providing a tube whose internal wall is coated with phosphor material,
sealing a structure having a cathode and a tubulation to each end of the tube, each said tubulation providing communication between the interior and the exterior of the tube,
introducing an inert gas into said tube through at least one of said tubulations,
electrically activating the cathode of each said structure,
removing at least a portion of the inert gas from the tube simultaneously through the tubulation of each said structure together with decomposition products produced by the cathode activation, and sealing off said tubulations.
12. The process of claim 11 wherein said tubulations are made of a material heat sensitive to energy of a predetermined wavelength, and further comprising the step of applying said energy to said tubulations after the tube is filled with the fill gas at the operating pressure to seal said tubulations.
13. The process of claim 11 wherein each of said structures has a lead wire which extends external to the tube and further comprising the step of fastening a base to the tube and connecting a said lead wire to an electrode terminal on the base.
14. A process as in claim 11 wherein the tube is exhausted at least during a portion of the time that the cathodes are being activated.
15. A process as in claim 11 wherein the inert gas is the lamp operating fill gas and said fill gas is removed to produce a fill gas pressure at which the lamp is to operate.
16. A process as in claim 11 wherein the inert gas introduced into the tube is introduced to substantially atmospheric pressure.
17. A process for manufacturing fluorescent lamps comprising the steps of:
providing a tube whose internal wall is coated with phosphor material, sealing a structure having a cathode and a tubulation of a material heat sensitive to energy of a predetermined wavelength to each end of the tube, each said tubulation providing communication between the interior and the exterior of the tube,
electrically activating the cathode of each said structure,
exhausting at least a portion of the gaseous environment of the tube simultaneously through the tubulation of each said structure,
introducing an inert fill gas into said tube through at least one of said tubulations, and
applying energy of said predetermined wavelength to said tubulations after the tube is filled with fill gas at the operating pressure to seal said tubulations.
18. A process as in claim 17 wherein the step of introducing the inert fill gas into the tube is carried out prior to the activation of the cathodes.
19. A process as in claim 18 wherein the tube is exhausted at least during a portion of the time that the cathodes are being activated.