US2625622A - Lamp starter - Google Patents

Description

F. H. RIXTON Jan. 13, 1953 LAMP STARTER Filed May 25, 1950 INVENTOR F. H. Fara/v.

ATTORNE Patented Jan. 13, 1953 LAMP STARTER Frederick H. Rixton, Bloomfield, N. J assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 25, 1950, Serial No. 164,183

7 Claims.

The present invention relates to what are now known to the art as glow switcheswhich are presently in common usage for the starting of fluorescent lamps.

Glow switches vary in their starting and operating voltages depending upon the starting and operating voltage of the particular lamp with which they are designed to operate. For example, the fifteen and twenty watt fluorescent lamps are both operable directly from the customary domestic source of potential of 110420 volts and one design of starter operates with both wattage lamps. The thirty and forty watt fluorescent lamps are operable from an auto-transformer which increases the customary domestic 110-120 volt source to approximately 250 volts and while both the thirty and forty watt lamps are operable by a single type starter, its design is necessarily diiierent from that required for the lowervoltage fifteen and twenty watt lamps. However, for satisfactory ope-ration of both types of glow switches, the pressure of the discharge-supporting gas in each instance is critical to assure proper operating voltage and longevity of the glow switch.

Heretofore the manufacture of the low switch ior the fifteen and twenty watt lamps did not readily lend itself to automatic mounting during fabrication, thus requiring costly hand mounting. Upon the recent introduction of the twenty-five watt fluorescent lamp the problem of a glow switch suitable for starting such lamp immediately arose. This posed the question of either designing a new glow switch specifically operable for only this twenty-five watt lamp, or the redesignin of the glow switch suitable for the fifteen and twenty watt fluorescent lamp, so that it would operate over the range from the fifteen watt to the new twenty-five watt lamp, with the latter being obviously the preferable solution from the standpoint of manufacturing costs and public desirability.

It is accordingly the object of the present invention to provide a glow switch for the starting of fluorescent lamps ranging from fifteen toiiuorescent lamps ranging from fifteen to twenty- 'fiv'ewatts and wherein the glow switch is readily :mounted automatically thus eliminating previously required hand mounting and reducin manufacturing costs,

Still further objects or" the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 is a perspective view of a glow switch constructed in accordance with the present invention;

Fig. 2 is a somewhat enlarged fragmentary side view of the glow switch shown in Fig. 1;

Fig. 3 is a view similar to Fig. 2, but taken 99 to the latter as shown by the arrows in Fig. 2;

Fig. 4 is a top plan view of the glow switch portion as shown in Fig. 2;

Fig. 5 is a perspective view of the getter tab or flag as used in the glow switch of Figs. l to i;

Fig. 6 is a fragmentary elevational view, partly in cross-section, of a slight modification which the glow switch of the present invention may take;

Fig. 7 is a top plan view of the glow switch shown in Fig. 6;

Fig. 8 is an elevational view of still another modification which the glow switch of the present invention may take; and

Fig. 9 is a perspective view of the getter tab or flag as used in the modification of Fig. 8.

Referring now to the drawings in detail, the glow switch as shown in Fig. 1 comprises a vitreous envelope 5 provided with a reentra-nt stem press 6 in which a pair of leading-in and supporting conductors l and 8 are hermetically sealed. As shown, the leading-in conductor l connects to a molybdenum rod extending above the press which thus forms a contact electrode 9 for the glow switch and a U-shaped bimetallic element, welded to the other leading-in conductor 8, forms the other or movable electrode 10 of the glow switch and which'is provided with a molybdenum contact I 2.. As shown in Figs. 1 to 5, a

metallic getter flag l3, formed of nickel or nickelplated iron of an area or" about .05 square inch. is shown welded to the bimetallic electrode it although it may just as readily be similarly secured to the inwardly protruding end of the leading-in conductor 8, and has embedded therein, a capsule or the like 14, comprising a mixture of magnesium and Zirconium.

During exhaust of the glow switch through the customary exhaust tubulation 15, the getter capsule I4 is vaporized by high frequency induction heatin to thus getter undesired gases which are trode it with the electron emissive magnesium to produce the desired voltage breakdown to initiate a glow discharge between the electrodes. Prior to sealing-01f the glow switch from the exhaust pump, the switch is filled with an ionizable medium such as 99.5% neon and 0.5% argon, or 99% neon and 1% krypton, at a pressure of about 50 mm.

It will be noted, particularly from Fig. 5, that the getter flag I 3 is desirably stamped or cut from a single piece of nickel or the like, with a portion thereof bent at right angles to the remainder to form a tab which is then welded to the bimetallic electrode ID or the leading-in wire 8, as above mentioned. Fastening this getter flag 13 to the bimetallic electrode [0, or the leading-in conductor 8 therefor, instead of the contact electrode 9, is highly important. A glow switch for starting a fluorescent lamp must perform a sequential operation and in as short a time as possible commensurate with certain functions.

For example, a glow discharge must be initiated between the electrodes as quickly as possible and at the avialable voltage. The pressure of the ionizable medium controls the break-down voltage and the lower this pressure the greater the facility with which the glow discharge is initiated at a given voltage. However, the lower the gas pressure the shorter the useful life of the glow switch. Accordingly, a compromise as to gas pressure must be reached which is sufliciently high to assure a reasonably long useful life and at the same time enable the glow discharge to be initiated with certainty as quickly as possible. The aforementioned pressure of about 50 mm. thus meets these requirements.

Following the initiation of the glow discharge, the bimetallic electrode must be rapidly heated to cause deflection thereof until its contact I 2 engages the contact electrode 9, thus extinguishing the discharge. The time of engagement of the glow switch electrodes naturally depends upon the rate of heat dissipation and such engagement must be for a period suificient to enable the filamentary lamp electrodes to be heated. Upon cooling the glow switch electrodes separate and at the instant of such separation a high voltage surge is produced due to the energy stored in the necessary ballast coil or transformer which is connected to the fluorescent lamp. The magnitude of such voltage surge is in turn dependent upon the resistance of the glow switch and the smaller the electrode area the higher the magnitude of the voltage surge. Again, however, a compromise must be reached for if the electrodes are too small and even though a higher voltage surge is obtained, such small area prolongs the sequential operation of the glow switch, due to the increased time required for the glow discharge to initially heat the bimetallic electrode- Accordingly, the area of the smaller contact electrode 9 is confined to that of a cylindrical electrode, as shown in the drawing, having a volume of not more than .00012 square inch or less than .00008 square inch, i. e. the area is not more than approximately .024 square inch or less than about .0160 square inch, with the getter flag l3 being purposely secured to the bimetallic electrode so as to not increase the contact electrode beyond the above noted area range.

Since the small area of the contact electrode 9 limits the glow current available for the heating of the bimetallic electrode I0, particularly when a condenser is utilized with the customary ballast on the lead-lamp circuit, this is-compensated for in accordance with the present invention by a decrease in the area of the bimetallic electrode [0, but with retention of sufficient glow current density (glow current per unit area) that the bimetallic electrode l0 heats quickly and deflects into engagement with the contact electrode 9, within the required short time period in accordance wih present accepted standards.

The bimetallic electrode 10, which is fast closing with the limited glow current available from the small contact electrode 9 of the above mentioned area, is obtained either by using a bimetal of much narrower width than the inch by .005. inch heretofore employed of say re inch, by utilizing a thinner bimetal of approximately .003 inch. which because of its thinness, has more deflection per degree to temperature change, or both a narrower and thinner bimetal electrode may be employed, with the latter lending itself more readily to automatic mounting. Moreover, the area of the bimetallic electrode desirably does not exceed 0.08 square inch.

In the modification shown in Fig. 6 the getter fiag 13 is of circular configuration and is carried by neither electrode, but by a supportingwire 22 embedded in the reentrant press 5 and bent outwardly and upwardly so as to position the getter flag l3 out of the path of movement of the bimetallic electrode I 0. Figs. 7 to 9, inclusive, show a still further modification of the present invention in which the getter flag !3 again is entirely independent of both electrodes so as to not eifect the area of the latter. In this latter modification the getter flag I3 is welded to one end of a wire 23 which has its other end bent into an open loop 24 imparting a slight spring action thereto. As shown, this loop 24 frictionally engages the inner wall of the glow switch envelope near its closed end which thus depends the getter flag [3 adjacent to but out of the path of deflected movement of the bimetallic electrode II].

It can thus be seen from the foregoing that a glow switch is provided by the present invention which is efiiciently operable for the starting of fluorescent lamps ranging from fifteen to twentyflve watts over a long period of useful life without sacrifice of operating characteristics and wherein the glow switch is so constructed that it can be automatically mounted, thus eliminating costly hand mounting resulting in reduced manufacturing costs. I

Although several specific embodiments of the present invention have been shown and described, it is to be understood that still further modifications thereof may be made without departing from the spirit and scope of the appended claims.

I claim:

1. A glow switch for th starting of fluorescent lamps of varying wattages comprising an enclosing' envelope provided with an ioniz-able medium therein at a pressure of about 50 mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the flow discharge and defiectable into engagement with the other of said electrodes to extinguish the glow discharge, the other of said electrodes having a surface area not less than .016 or more than .024 square inch for increasing the resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter. flag disposed in said envelope without in trodes beyond .024 square inch.

2. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about 50 mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and deflectable into engagement with the other of said electrodes to extinguish the glow discharge and having a surface area not exceeding 0.08 square inch, the other of said electrodes having a surface area not less than .015 or more than .024 square inch for increasing the resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag disposed in said envelope without increasing the surface area of the other or" said electrodes beyond .024 square inch.

3. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about 50 mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and defiectable into engagement with the other of said electrodes to extinguish the glow discharge and having a surface area not exceeding 0.08 square inch, the other of said electrodes having a surface area not less than .016 or more than .024 square inch for increasing the resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag supported by said bimetallic electrode.

4. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about 50 a of electrodes disposed in said en e ope bet n which a glow discharge occurs during operation of said glow switch, one of said. electrodes being a bimetallic element heated by the glow discharge and deflectable into engagement with the other of said electrodes to extinguish the glow discharge and having a width of about one-sixteenth inch and a thickness of about .003 inch, the other of said electrodes having a surface area not less than .024 square inch for increasing th resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag disposed in said envelope without increasing the surface area of the other of said electrodes beyond .024 square inch.

5. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about 50 mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and deflectable into engagement with the other of said electrodes to extinguish the glow discharge and having a width of about onesixteenth inch and a thickness of about .003 inch, the other of said electrodes having a surface area not less than .015 or more than .024 square inch for increasing the resistance of sai: glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag supported by said bimetallic electrode.

6. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about 40 mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and defiectable into engagement with the other of said electrodes to extinguish the glow discharge, the other of said electrodes having a surface area not less than .016 or more than .024 square inch for increasing the resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag having a surface area of about .05 square inch disposed in said envelope without increasing the surface area of the other of said electrodes beyond .024 square inch.

'7. A glow switch for the starting of fluorescent lamps of varying wattages comprising an enclosing envelope provided with an ionizable medium therein at a pressure of about mm., a pair of electrodes disposed in said envelope between which a glow discharge occurs during operation of said glow switch, one of said electrodes being a bimetallic element heated by the glow discharge and deflectable into engagement with the other of said electrodes to extinguish the glow discharge and having a width of about one-sixteenth inch and a thickness of about .003 inch, the other of said electrodes having a surface area not less than .016 or more than .024 square inch for increasing the resistance of said glow switch at the instant of separation of said electrodes upon cooling of said bimetallic electrode, and a getter flag having a surface area of about .05 square inch disposed in said envelope without increasing the surface area of the other of said electrodes beyond .024 square inch.

FREDERICK H. RIXTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,267,098 Hays, Jr Dec. 23, 1941 2,285,805 Chirelstein June 9, 1942 2,398,128 Zyta Apr. 9, 1945

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