US2336960A - Discharge lamp - Google Patents

Description

Dec. 14, 1943. E. A. REUTER ETAL DISCHARGE LAMP Filed Aug. 13, 1941 "/INVENTORS EDMUND D. D. If BY ATTORNEY erated at the Patented Dec. 14, 1943 msonsacn LAMP Edmund A. Renter, East Orange,

Knowles, Vero house Electrlc &

and Dewey D.

na, N.- .L, assignors to Westingurin a mpany.

East Pittsburgh, Pa., a corporation of Pennsylvama Application August 13, 1941, Serial No. 406,580 9 Claims. (Cl. 176-122) This invention relates to discharge lamps, and

more particularly to lamps adapted for steriliz-' ing purposes.

As is known, sterilizing lamps are employed in various places, such .as in refrigerators, for which purpose such lamps must be operable from the usual domestic source of supply, generally 110 volts. Provision is necessary not only to operate the lamp at line voltage, but to start it promptly with that available voltage. Ultraviolet radiation, especially that of short wavelength at about 2537 Angstrom units, which is the most highly bactericidal, is generated most effectively or profusely under favorable conditions of pressure and temperature in the lamp. It has also been found necessary in lamps of the character indicated, to include a ballast in the electrode circuit, and this has introduced physical and thermal difiiculties in manufacture and use.

An object of the present invention is to make a satisfactory sterilizing lamp for low-voltage operation.

Another object of the present invention is to .maintain the lamp temperature .at the point which gives the proper mercury vapor pressure for the most efficient generation of ultra-violet radiations.

Another object of the present invention is to utilize as little heat as possible and to apply it efiectively for the purpose stated.

A further object of the present invention is to incorporate the ballast resistance within the lamp envelope.

A still further object of the invention is to utilize the ballasting resistance for a secondary purpose of producing beneficial heat for maintaining the desired lamp temperature.

Yet another object of the invention is to overcome presence of a dark spot or shadow longitudinally between electrodes intercepting the radiation.

Other objects include provision of a substantially symmetrical construction; to increase sturdiness, lower cost, secure simplicity, and employ a heating-ballast in which the heat is genportion of the resistance curve which gives a small change in temperature for a relatively large change in volume.

Still further objects will appear to those skilled in the art as the description progresses, both by direct statement thereof and by implication from the context.

In the accompanying drawing, wherein hke numerals of reference indicate similar parts near andwherein the only of the many throughout the several views, invention is disclosed in a few possible physical embodiments;

Figure l is a longitudinal sectional view of a discharge lamp embodying features of our invention;

Figures 2 and -3 are cross-sectional views thereo and their mounting;

Figure 5 is an abbreviated longitudinal sectional view similar to Fig. 1, showing a modified construction of ballast- -resistor and electrode In the broad general aspect of use, construction of and gaseous medium involved in the present invention, reference may be had to patent of Robert F. James (issued in consequence of application S. N. 734,620), for radiating apparatus. The present invention utilizes an elongated vitreous envelope I0, opposed electrodes II, II opposite ends thereof, and a gaseous medium with a mercury vapor content, as broadly specified in that patent.

The envelope preferred, however, is one which is elongated and having a screw-threaded base l2 at one end for standard connection through a usual socket (not shown) to the source of potential, and having its end opposite the base formed as a rounded closure in accord with the more usual lamp practice. The character of glass is selected for its beneficial transmission of the desired ultra-violet radiations, for which purpose it may preferably comprise borosilicate glass free from iron and identified in the trade as high transmission glass or Corex D. Said envelope is shown provided at the base end with a re-entrant stem I3 through which are sealed conductors for the current supply, one from the screw threaded conductive portion of the base and another from the central bottom tip Id of the base which is insulated from the said threaded portion.

Turning attention specifically to Figures 1, 2 and 3, the lampthere shown provides a central conductive rod or wirel5 sealed into the press It of stem I3 and in continuation of connection I! which extends downward through the stem where it is in series with a. ballast resistance 18 having a central eyelet 2| gripping the disk and the rod. At outer peripheral parts siidable upon 22 resilient y of the disk are applied spring tabs engaging the side walls of the envelope. longitudinally surrounding the said rod l for the greater part of its length, is an insulative sleeve 23 of tubular formation, dered, as at 24, near its end toward the stem with a reduced neck from said shoulder downward toward the stem. Around this neck is an insulating collar 25 which extends substantially from the shoulder to the press end of the stem l3.

Between the shoulder 24 of the sleeve 23 and juxtaposed transverse disk-like end wall 26 of a cylindrical electrode H which extends upwardly away from said end wall and stem co-axial with and around said rod I5 and sleeve 23 for a portion of the lengths of those parts. The inner diameter of 'the electrode is considerably greater than the I outer diameter of the sleeve thereby providing a material opening or gap between electrode and sleeve and with the far end of the electrode open. A similar electrode II is mounted at thefar end of the sleeve, in this instance the disk-like end wall 26 of the electrode engaging against the end of the sleeve and secured thereagainst by a metallic conductive collar 21 carried therebeyond on the protruding end portion of the rod. The near end of the far electrode ll isalso open and its cylindrical wall spaced from the sleeve, so that the. open end of the two electrodes face each other, but are spaced quite a distance apart longitudinally, representing the glow discharge distance to be effected when the lamp is inoperation. The inner circumferential wall of both electrodes are preferably electron emissive, as by having a coating 28 thereon of emissive material, such as strontium, barium and calcium oxides.

The electrode ll next the press is, as shown and described, insulated from the central rod, and to connect it electrically with the other side of the power supply, is shown as having a lug 28 at its lower closed end depending towards the stem and welded or otherwise secured to a conductor 30 projecting upward from the press and bent at its upper end to cross said lug. er endof conductor 30 sealed in the press has a connection 3| to the screw base 12.

The envelope has a tubulation 32 enabling the usual evacuation to be efiected, after which appropriate gas charging is effected, including introduction of desired amount of mercury for production of mercury vapor. The usual gaseous medium may be any one or combination of noble gases, such as argon, neon, and the like. Introduction of mercury may be by including the same in a pellet 33, here shown as hung from the conductor 30'next the stem where it may be conveniently flashed by a plied for the purpose, all of which is more fully explained in co-pending application of co-inventor herein, Edmund Renter,- S. N. 399,059, filed June 21, 1941.

A feature of the p of means for initiating esent invention is provision the dischare automaticalend of said collar is situated a The low- 1 high f q e y current aply and without moving parts and at normal operating voltage. As a physical fulfillment of this objective, we provide trigger members in the several views, the same being shown in Figures 1 and 3 as strips 34, 35 of terial on diametrically opposite sides of the insulative sleeve 23 extending longitudinally thereof. One of these strips, as 34, is electrically and physically connected with the electrode H nearest the press and extends therethrough out of the open end thereof, along the on said sleeve somewhat within the open end of the far electrode.

- cally and physically connected with far elecpreferably shoultrode II and extends therethrough out of the open end thereof, along the sleeve toward the press and into the open end of the near electrode, terminating somewhat within the same.

Initial application of potential of voltage sufficient to maintain glow discharge betweenthe electrodes when once the discharge is started, is not sufllcient to ordinarily initiate the discharge directly from one electrode to another separated proper operating distance. However, by use of trigger means such as the resistive strips or members 34, 35 coming to closer association wit the electrodes within minimum break-down v'o e distance of the gaseous atmosphere, an ionizing discharge between said electrodes and trigger members .will occur, and by virtue of the ionized atmosphere, the glow discharge between electrodes II, II then follows.

Attention is called to the fact that the glow discharge from one electrode to the other entirely surrounds the intervening portion of sleeve 23, and consequently no shadow is cast by the conductor resultant from its passage to the far end of thelamp. While the provision of the central conductor and sleeve produces a symmetrical construction, full advantage thereof without the resistive trigger members present is not obtained, due to the fact that the starting voltage is then too high because of charges collecting on the central glass spacer or sleeve 23 as well as on the envelope wall. By our construction, however, we overcome the detrimental effects by inclusion of the resistive trigger members or strips. Thus we gain the advantages of a symmetrical construction with its lower cost of material, its simplicity and consequent greater ease of assembiy and reduction of labor cost, its greater sturdiness and its elimination of dark spots or shadows in the ultra-violet output.

There are various ways of providing trigger- .of Fig. 4, with the lamp otherwise formed and operated as above described. While also, the said trigger members may be formed in place by painting or the like, as previously described, aided by the grooves to receive the then plastic material, yet we have chosen to illustrate preformed resistive wire-like members 34, 35' in said grooves, held therein by adhesive or otherwise.

It is a desirable feature of a lamp of the character indicated, to maintain the lamp temperaelectrically resistive masleeve, and terminates Similarly strip 35 is electriwire l8" protrudes from ture at the point which gives the proper mercury vapor pressure for the most efiicient generation of ultra-violet radiation, and to provide a series ballasting resistance. In the above description the series ballasting resistance I 8 is shown within the base. However, for rendering the baseapplying operation more simple, and for utilizing the ballast obtain a desired temperature control in the lamp, it is preferred to incorporate the same within the envelope, as shown in modified constructions of Figures -7.

Referring now to Figures 5 and 6, the parts of resistance to also more efiectively the lamp structure necessary for illustration of the modified parts over the general structure of Figures 1 to 4 are there shown. This showing modifies the stem structure only to the extent that the central rod I5" is sealed in the press without an electrical connection therefrom through the stem. Instead, a lead-in connection ll" direct from the base tip is provided to make connection with a ballast resistance and heater element l8" extending longitudinally of a passage 31 parallel to and ofiset from rod I5". Said offset passage 31 extends the length of the sleeve enabling the far end of the heater-ballast element Hi" to extend to the end wall 26 of the far electrode and be physically and electrically attached The lower end of the heater-ballast a side opening 38 in collar 25" and is attached to aforementioned connection ll". In this showing, therefore, current is carried from tip l4 through connection I1" and heater-ballast I8 to the far electrode H instead of through rod l5 of the previously described assembly. Current to the near electrode H in both arrangements is through connection 3|, conductor 30 and lug 29. Envelope enclosure, basing, gaseous medium, mercury vapor and starting trigger members for the construction of Fig. 5 are to be understood as being identical with the showing and description given with respect to Figures 1 to 4. The structure likewise presents the symmetrical arrangement and advantages above-recited with the added feature of the heater-ballast being included in the lamp and effective for introducing the desirable heat energy dissipated by the heaterballast directly in the lamp. It likewise has the added advantage over construction of Fig. 1 in permitting the tubulation 32 to be situated midway of the sides of the press l6.

If preferred, and especially for use in refrigerators where heat transfer is most pronounced by conduction through the base and socket, the heater-ballast element may be situated next the thereto.

stem. Such arrangement is shown in Fig. 7. In

this illustration, we have shown electrode construction and conductor for the far electrode taking the general form shown and described in copending application of coinventer herein, D. D. Knowles, S. N. 339,441, filed June 8, 1940. Stem 13 with press IS, in this view, provide a substantially central supporting rod 39 for a near electrode 40, but without extending through said electrode. An insulative sleeve 4| is situated around the rod between the press and electrode, and on this sleeve is wound a heater-ballast element 42, the far end of which is physically and electrically attached to the electrode whereas the end next the press is made secure to a lead-in connection 43 through the press to the appropriate base connection. Another lead-in connection 44 through the press from the other base terminal part, is connected above the press to a rod or other connection 45 offset from the electrode to make electrical connection with the far electrode (not shown in this view) corresponding to far electrode ll of Fig. 1.

For initiating discharge in this construction of Fig. 7, a trigger member 46 may be provided efl'ective in'operation to obtain a short path from the electrode emitting surface to the trigger member for initiating ionization at load potential. As shown, a branch connection 41 is made from the feeding connection 44 in the stem to a fixed connection 48 protrudingfrom the stem. To this connection 48 is attached the lower end of trigger member 46 which extends upwardly at the side of but spaced from electrode 40, said trigger member being of electrically resistance wire formation and having its far end bent backward into the end opening of the electrode. The spacing of the trigger member in all showings is to be understood as at the minimum break-down voltage distance of the gaseous atmosphere from the electrode with which associated. Furthermore, it is to be understood that the trigger member in this showing, as well as in the preceding views, includes inherent or other resistance suflicient to render passage of current through it and to the electrode by the electron path therebetween more difficult than direct discharge from one electrode to the other after such discharge has begun, thereby automatically stopping current fiow by way of the trigger member when glow discharge between the electrodes commences.

It is to be understood that while the showing of Fig. 7 provides for connecting the far electrode by a connection at the outside of the electrode, it is within the scope of the invention to utilize the symmetrical construction of rod connection of Figures 1 to 4 with the heater-resistance element 42 of Fig. 7, and to otherwise combine specific parts of one showing with respect to other specific parts of other views. More generally, therefore, it is to be understood that since the various details of construction, as well as the precise relation and functioning of parts are subject to variation and change without departing from the inventive concept or scope of the invention, all matter contained in the specification or illustratedin the drawing, shall be interpreted as exemplary and not in a limiting sense. It is also intended that the following claims are to be covering all of the generic and specific features of the invention herein shown and described and all statements of the scope of the invention herein set forth as a matter of language which might be said to fall therebetween.

We claim:

1. A discharge lamp comprising an elongated vitreous envelope with a single stem and press, a substantially central rod projecting longitudinally into said envelope from said press, opposed electrodes adjacent opposite ends of the rod, said rod extending axially through both said electrodes, an insulative sleeve on said rod, and a trigger member on said sleeve electrically connected with one electrode and projecting into the other in spaced relation thereto.

2. A discharge lamp comprising an elongated vitreous envelope with stem and press, a substantially central rod projecting longitudinally 4- asaaeeo trodes, an insulative sleeve on said rod, and trigger members separate from each other on opposite sides or said sleeve each connected to a diilerent electrode and projecting into the one to which not connected in spaced relation thereto.

3. A discharge lamp comprising an elongated vitreous envelope with stem and press, a substantially central rod projecting longitudinally into said envelope. from said press, opposed electrodes adjacent Opposite ends or the rod, said rod extending axially through both saidrelectrodes, an insulative sleeve on said rod, and a trigger member comprising a painted-on strip of resistive material on said sleeve electrically connected with one electrode and projecting into the other in spaced relation thereto.

4. A discharge lamp comprising an elongated vitreous envelope with stem and pr a substantially central rod projecting longitudinally into said envelope from said press, opposed electrodes adjacent opposite ends of the rod, said rod extending axially through both said electrodes and having grooves on opposite sides of the said rod, and trigger members in said grooves, each trigger member being connected to an opposite one of said electrodes and projecting into the one to which not connected in spaced relation thereto.

5. A discharge lamp comprising an elongated vitreous envelope with stem and press and enclosing a gaseous atmosphere, a substantially central insulative sleeve projecting longitudinally into said envelope from said press, electrodes in said envelope at separated positions for glow discharge, and a heater-ballast carried by said sleeve and connected-to one of said electrodes and at least in part exterior to said electrode for constituting heating means for the gaseous atmosphere in said envelope.

6. A discharge lamp comprising an elongated vitreous envelope with stem and press and enclosing a gaseous atmosphere, a substantially central insulative sleeve projecting longitudi nally into said envelope from said press, electrodes in said envelope at separated positions for glow discharge, said sleeve extending from one electrode to the other partly inside and partly outside said electrodes, and a heater-ballast carried longitudinally within and substantially full length of said sleeve and connected to one of said electrodes and constituting heating means for the gaseous atmosphere in said envelope.

'7. A discharge lamp comprising an elongated vitreous envelope with stem and press and enclosing a gaseous atmosphere, a. substantially central insulative sleeve projecting longitudinally into said envelope from said press, electrodes in said envelope at separated positions for glow discharge, and a ballast resistance carried around said sleeve between said press and the near electrode, and constituting heating means next the stem end of the envelope for the gaseous atmosphere in said envelope.

8. A discharge lamp comprising an envelope having a stem, a pair of cylindrical glow-discharge electrodes carried by said stem, input and output leads through the stem for said electrodes, a conductive rod mounted in said stem forming a support for both said electrodes and passing through the interior of each longitudinally thereof, said rod being electrically connected to one lead and to the electrode more distant from the stem, whereby glow discharge between the electrodes surrounds the said rod and lateral deflection of the discharge and exterior dark areas along the discharge are avoided.

9. A discharge lamp comprising an elongated envelope having a stem at one end thereof through-which all lead-in wires extend into the interior of the envelope, lead-in wires through said stem, a cylindrical cup-shaped electrode at the far end of the envelope from the stem electrically connected to one lead-in wire, another cylindrical cup-shaped electrode at the near end of the envelope to the stem electrically connected to another lead-in wire, and a central rod carried by said stem and extending longitudinally of the envelope, said electrodes being carried by said rod thereby constituting the electrodes, rod and stem a unitary assembly, and said electrodes being spaced from each other with the open ends of the cup shape thereof directed toward each other and receiving the rod therein, whereby glow discharge between the electrodes surrounds the said rod and lateral defiection of the discharge and exterior dark areas along the discharge are avoided.

EDMUND A. REUTER. DEWEY D. KNOWLES.

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