US 3169205 A
Description (OCR text may contain errors)
Feb 9, 1965 H. R. KESTNER ETAL 3,169,205
FLuoREscENT LAMP MOUNT Filed April 5, 1961 '2,9 IDVGDTOVS:
Robecl: A. Huvebbe Theny AelfiOT-heg Havo Ld 1Q. Hescime United States Patent O Hamid R.. Kastner, Maycid Heights, and Robert A. Kuehler, Cieveiand Heights, Ghia, assignors to Generali iiieetric Company, a corporation of New York Fitted Apr. S, 1196i, Ser. No. 1%,892 il@ lairns. (Qi. 3h30-iti?) This invention relates to the manufacture of fluorescent lamps and in particular to the structure and manufacture of the mounts through Whichfvare sealed the lead-in wires Y applyingY the coating.
The object of the invention is to provide a solution to the clear spot problem as stated above.
investigation of this problem has traced it to the gas filling of the lamp on the exhaust machine. In the processing of fluorescent lamps, the elongated tubes which form the envelopes of the lamps are first coated internally with a phosphor by causing the phosphor suspension to flow therethrough yand afterwards drying it. yThe next step involves the sealing machine on which the lamp mounts through which extend the lead-in wires that support the electrodes, are sealed into the ends of the envelope. Following sealing, the lanp is processed on the exhaust rnachine where the electrodes are activated by passing cur- :rent through the filaments in order to heat and decompose the alkaline earth carbonate coating thereon to alkaline earth oxide. At the same time the lamp is evacuated to remove the air and any gases and vapors including carbon dioxide resulting from the decomposition of the alkaline earth carbonatos. The exhaust of the lamp is performed through the exhaust tube of one of the mounts which was previously blown open at the press for this purpose. Finally, at one of the last positions on the exhaust infachine, an inert filling gas is added and a small measured quantity or dose of mercury -is released into the lampy sure of a few millimeters of mercury, for instance at 2 to 3 millimeters.
Surprisingly enough, considering the low filling pressure and the relatively srn-all mas-s ofgas involved, we have determined that it is the addition of the ll gas which causes the clear spot in the phosphor coating next to the mount. The gas lilling system ycommonly used is essentially a constant mass-flow typewith a restrictiony controlling the rate of flow from a pressurized source such as a high pressure cylinder. The blow-out of the conventional mountdesign which `has been commonly used in iiuorescent ylamp manufacture directs the gas jet at an `angle of about 30 relative yto the tube wall. The angle of the blow-out, together with the fact that there maybe some slight constriction `at the exit, results in a gas jet of suihcient force to blow the phosphor coating off the Wall.
We have considered and discardedvarious possible solutions to this problem. For instance the use of a truly axial mount with a blow-out at the tip of the press along the axis of the exhaust tubeis noty desirable because it presents majorrnanufacturing diiiiculties. The mercury dose is formed in accordance with the invention.
3,169,205 Patented Feb. 9, 1965 ice released into the lamp lthrough the exhaust tube and the cathode filament coated with emission mix extends across the axis of the mount. Since the lamp is vertically supported at this time, the mercury charge would strike the filament with the possibility of dislodging rthe emission mix coating. offsetting the cathode to one side of the axis is not a satisfactory solution because it introduces further complications in mount manufacture, and moreover lamp appeanance is adversely affected.
` In accordance with the invention, we have satisfactorily resolved4 the problem by modifying the shape of the blow-out aperture at the press of the exhaust tube. We have flared the exit aperture and increased its width in a direction perpendicular to the axis of the exhaust tube, and we have changed the direction of the blow-out aperture by continuing it into a grooved channel formed in the side of the press and extending towards its end. Preferably the grooved channel makes but a shallow angle relative to the exhaust tube or lamp axis. These modifications have substantially eliminated clear or thin spot formation in the phosphor coating at gas ill.L
For further objects and advantages and for a detaile explanation `of the invention, attention is now directed to the following description of a preferred embodiment taken in conjunction with the accompanying drawing. The features of the invention believed to be novel will be more particularly pointed out in the appended claims` In the drawing: v r
FiG. 1 is a side View, foreshortened and partly sectioned, of a fluorescent lamp embodying the invention.
FIGQZ is a side view of a convention-al mount operatively positioned relative to la mechanism forreforming the blow-out aperture.
FIG. 3 shows the same mount as in FIG. Zwith the reforming jaws actuated up into engagement with the mount press.
FIG. 4 is a side cross-sectional view of the mount re- FIG. 5 is a side view of the reformed mount rotated on its axis 90 relative to FIG. 4 so as to place the wide curved surface of the blow-out aperture in the plane of the drawing.
The typical lamp illustrated inthe drawing comprises a vitreous envelope i which iscoated internally with a phosphor indicated by the .dotted line .at 2.V `To each end of the lamp a mount is sealed such as indicated at 3 in FIG. 2 for the case of the conventional mount heretofore used, yand at 3a in FIGS. 4 and 5 for the improved quasiaxial blow-out mount kin accordance with the invention.
Referring to FiG. 2, the -conventional mount y3' cornprises a stern tube which is formed into aflare i into about the ends of the filament 9 which is Vcoated with alkaline earth carbonate emission mix asindicated at yit) in FIG. 5.v in FIG. 2, the mount 3 has a blow-out aperture ill with an exit surface` i2 at a stecpanglerelative to the axis ofthe exhaust tube. This causes the gas jet which forms during the inert gas lling operation-to strike with considerable force the envelope Wall andto blow off the phosphor coating leaving a spot in the region indicated at i3 in FIG. l whichis either clear or only very thinlyicoated with phosphor.y
In accordance with the illustrated embodiment of the invention, the blow-out aperture ofthe mountis reformed Vto provide a flaring exit aperture 14 and a relatively wide grooved channel l5 in the side of the press and extending towards the end, as indicated in FIGS. 4 and 5. The reforming of the blow-out aperture may be doneon a mount or stem machine wherein the mount is supported inverted position by means of jaws lu which grip the exhaust tube, as conventionally indicated in FEGS. 2 and 3. The blow-out aperture fill shown in FiG. 2 was ormed in conventional fashion at an earlier station on the stem machine by blowing a puit of air through the exhaust tube while lires are played on the sides of the press to maintain the glass in a viscous state. The reforming of the press to give the desired blow-out contour is done by means of matrix jaws i7, i8, shown in FlGS. 2 and 3. l aw i7 is provided with a rounded inclined ridge i@ while jaw 18 is provided with a relief V 2u. rfhe matrix jaws are mounted on pivoting levers 2l, ZZ which are actuated by means of links 23, 24 from a vertically reciprocating crosshead 25. In FIG. 2, the jaws and levers are shown in their outswung retracted position whereas in FlG. 3 2they are shown in their upswung position engaging the press of the mount. The glass engaging surfaces of the matrix jaws diverge slightly in the direction ot the filament so that excess glass not displaced laterally is forced down in the direction of the iilament and may lengths the press slightly.
In conventional mount making, the blow-out aperturev may occur haphazardly on either side of the press, that is to the right as shown in FlG. 2, or to the left. For the present purpose, it is necessary that the blow-out always occur on the same side. This is achieved by offsetting the press-forming jaws to one side of the axis of the exhaust and stem tubes at the first pressing. This results in a press o as illustrated in FiG. 2 wi `h slightly less glass on one (right as seen in the drawing) side ot the axis than on the other. Then when the blow-out is formed, it forms preferentially on the side having the less glass. This preferential forming may be further assisted by making the tires slightly hotter on the side of the mount where the low-out is desired to form.
The contour of the improved mount in accordance with the invention is shown in FGS. 4 and 5. The exit aperture i4 iiares outwardly and is continued into a grooved channel iS'extending between the lead-in wires towards the end of the press. The central portion of the wall oi channel 15, which may be referred to as the exit surface, makes a shallow angle between 5 and 15, preferably about 9, to the axis of the exhaust tube which is also the longitudinal axis of the lamp envelope. Furthermore, as best seen in FG. 5, the exit aperture ld and the grooved channel 1S are widened transversely to the axis of the exhaust tube substantially in excess of the internal diameter of the passage through the exhaust tube. This combination of features insures that the filling gas jet emerges at a relatively shallow angle with respect to the envelope wall and with a lessened velocity. in other words, the gas jet is almost parallel to the lamp axis and has less force with the result that the phosphor is not blown off. At the same time, the shallow angle of the exit surface insures that when the mercury dose (shown as a drop 26 in FIG. l) is released into the lamp through the exhaust tube, it is deiiected olf axis and does not strike the :filament 9. Thusthe possibility of dislodging emission coating from the filament is avoided.
The more common manufacturing procedure is to exhaust and gas till the lamp from one end only, that is from the top end which would have mount 3a. ln such case a so-called dummy mount 3b is used at the other end. The dummy mount may be similar to the conventional mount 3 shown in FIG. 2 except that the exhaust tube is not blown out at the press. An exhaust tube may nevertheless be provided to facilitate locating the end of the lamp in the clamp or holder therefor on the exhaust machine. However, if in order to further increase the machine speed it is desired to exhaust and gas iill from both ends of the lamp, then in such case both ends of the lamps would be provided with the improved mount 3a according to the invention.
The invention thus provides an unexpectedly convenient and ortuitous solution to the problem of clear spot formation in the phosphor coating at gas lill and without requiring any extensive modifications in lamp making machinery or processing techniques. Furthermore, the problem is solved without running aioul of the danger of `emission coating dislodgement from the cathode which is encountered with an axial blow-out mount design.
The preferred embodiment of the invention which has been described in detail and illustrated in the drawing is intended as exemplary and not in order to limit the invention thereto. The scope of the invention is to be determined by the appended claims.
Wha-t we claim as new and desire to secure by Letters Patent of the United States is:
1. A fluorescent lamp mount comprising a flared stein "abe and an exhaust tube extending axially thercinto and torminU a juncture therewith constituting a vitreous press, lead-in wires projecting through said pr ss, and a bl rout aperture formed in one side of said press and cornmunicating with said exhaust tube, said blow-out aperture being ilared outwardly and vwidened relative to the exhaust tube passage so that a gas jet issuing therefrom issues with reduced velocity and in a quasitaxial direction.
2. A fluorescent lamp mount comprising a flared stern tube `and an exhaust tube extending axially thereinto and forming a juncture therewith constituting a vitreous press, 'lead-in wires projecting through said press, and a blow- `out aperture formed in one side of said press and communicating with said exhaust tube, said blow-out aperture being continued into a groove formed in said one side of the press 'and extending towards the end thereof.
3. A iuorescent lamp mount comprising a ilared sten tube and an exhaust tube extending axially thereinto and forming a juncture therewith constituting a vitreous press, lead-in wires projecting through said press and supporting an electrode, and a blow-out aperture formed in one side of said press and communicating with said exhaust tube, said blow-out aperture being iiared outwardly and widened relative to the exhaust tube passage and being continued into a grooved channel formed in said one side of the press and extending towards the end t creci.
4. A fluorescent lamp mount comprising a ilared stem tube and an exhaust tube extending axially thereinto and forming a juncture therewith constituting a vitreous j press, lead-in wires proje ting through said press and supporting a filament transversely to the axis of said exhaust tube, and a blow-out aperture `termed in one side of said press and communicating with said exhaust tube, said blow-out aperture being flared outwardly and widened relative to the exhaust tube passage and being extended as a channel in said one side of the press between said lead wires substantially to tre end of said press so that a gas jet issuing from said aperture issues with reduced velocity in a direction making a shallow angle with said axis but avoiding said filament.
5. A fluorescent lamp mount `comprising a iiared stem tube and an exhaust tube extending axially thereinto and forming a juncture therewith constituting a vitreous press, lead-tin wires projecting through said press and Supporting a filament across the projected axis of said exhaust tube, and a blow-out aperture formed in one side of said press and communicating with said exhaust tube, said blo: -out aperture lbeing widened relative to the exhaust tube passage and `being continued into a grooved channel formed in said one side of the press and extending towards 4the end thereof, the central portion of the channel wall being inclined to said one side at an angle between 5 and 15 to the axis of said exhaust tube.
6. A iiuorescent lamp mount as` defined in claim 5 wherein said central portion or" the channel wall is inclined to said one side at an angle of approximately 9 to the axis of said exhaust tube.
7. A fluorescent lamp comprising an elongated tubular envelope internally coated with phosphor and having mounts sealed into the ends thereof, at least one of said mounts comprising a flared stern tuberand an kexhaust tubeA penetrating thereinto and forming a juncture therewith constituting a vitreouspress, lead-in wires projecting through said :press and supporting a filament Wit-hin said lamp, and a blow-out aperture formed Vin one side of said y press and communicating with said-exhaust tube, said yblowout aperture being kflared outwardly and widened relative to the exhaust ltube passage so that a gas jet issu-` ing therefrom into said lamp at gas lill issues with reduced velocity and in a quai-axialfdirection relative to said enveloper in order to avoid blowing phosphor oil saidV envelope Wall.
, 8. A iluorescent lampcornprising an elongated tubular envelope internally coated with phosphor 4and having mounts sealed into the ends therof, at least one of said mounts comprising a flared stern Itube and an exhaust tube penetrating thereinto and forming a juncture therewith constituting a vitreous press, lead-in Wires projecting through said press and supporting a filament with-in said lamp, and a blow-out aperture formed in one side of said press and communicating with said exhaust tube, said blow-out aperture being lared outwardly and widened relative ato the exhaust tube passage and continued into a grooved channel )formed in said one side of the press and exten-ding to the end thereof, whereby a gas jet 9. y A jlluorescent lamp comprising an elongated tubular envelope internally coated with phosphor and nhaving mounts sealed into the ends thereof, at least one of said mounts comprising a flared stem tube and an exhausttube penetrating rthereinto and forming a juncture therewith constituting a vitreous press, lead-in wires projecting through said press and, supporting a filament within said lamp across its axis, and a blow-out aperture formed in one side of said press and communicating with said exreleased into the lamp through said exhaustY tubeis delected olf axis sufciently lto avoid striking said filament. l0. A lamp :as .in claim 9 wherein said grooved channel is inclined at an angle or approximately 9 to said lampV axis.
issuing from said aperture into said lamp at gas ll issues Y with reduced yvelocity and in `a quasi-axialV direction rela-y tive to said envelope in order to avoid blowing-phosphor olf said envelope wall. L Y
- References Cited in the tile of this patent UNITED STATES PATENTS Y 2,692,347
2,991,386 Szigeti et al. V `l'uly 4, i961 Mason oor. i9, 1954