US2440832A

US2440832A - Gas discharge lamp

Info

Publication number: US2440832A
Application number: US596560A
Authority: US
Inventors: Pennybacker Miles
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-05-29
Filing date: 1945-05-29
Publication date: 1948-05-04
Anticipated expiration: 1965-05-04

Description

` UNITED `s'liirlss PATENT ori-*ICE v Gasiil'szmanm 4 VvMiles Pennybocker, Westport, Golm. Application my 29. i945, serial No. 596,560Y

columnV gas discharge.

f invention includes 'certainelements and ieaturesof the lamp described in my co-pending applicationV Serial #569,488,` illed December 23,

`comme (ci. 17e- 122) Positive column gas discharge lamps are y usually constructed in the form of a relatively long Vand narrow cylinder of glass, .quartz vor other suitable transparent or translucent material, pro- -videdwith suitable electrodes at b oth ends thereof. In one widely used form, the internal surface'of the transparentenvelope is coated with as ultra violet. toanother portion ofthe spectrum better suited for general illuminating purposes. Y

For most purposes, it is 'desired that the light from a l'lamp be emitted over anfarc of not exceeding 180 degrees. Accordingly, when a cylindrically-shaped lamp is'employed, it is usually found necessary, or, at lleast lhighly desirable, to employ a reflector whichvwill render available a portion of the light otherwisewastedby reason of the fact thatit is emitted in an undesired direction. Y

One object 'of thisinventionjis to provide a novel form of elongatedcylindrical lamp 'from which the externally available light isemitted substantially wholly along onev longitudinal hall' of the cylinder. thus causing thelminous output of the lamp tov be compietely'available without which optical eillciency is increased by causing the useful light to proceed directly from the surface of the phosphor which is acted 'upon by radiations coming from the positive-column discharge, and'causing this light to pass` directly to the exterior of the tube, without having to pass through any other layers of phosphonor through other semi-opaque material.

Other purposes and advantages of this invention will be apparent to those skilled in the art from the following description of several embodiments thereof. l.

Reference is now made to the drawings hereunto attached; where Fig. 1 is a perspective view of a. tube embodying one torm-oithis invention.

Fig. 2A is-a cross-sectional view of the tube oi l Fig. 1,

Fig. 2B is a cross-sectional view oia tube embodying another form ofI this invention,

- tive form of this invention, using a divided reelements which have hitherto been formed as n metallic deposits', or the like, upon such internal wall, and lwhich reflector may also act as asupport forja iluorescent coating.. 4 l

A still further ,purpose of this invention is to provide a tubular lamp in which the reilector can be manufactured independently of the tube vand` only,l insertedV therein when the tube is ready to be sealed. This discrete construction is 'well adapted .toA economical large scale production, in

contrast to certain hitherto; vemployed methods' of constructinggan internal reiiector, in situ.`

ector strip.

Referring now to Figs. 1 and 2A, there is here.

shown an elongated tube I, of suitablegas-contlning material such as glass.` This material is chosen to be transparent to radiations having such wave lengths as are to be utilized externally. For example, the tube may be constructed of ultra violet transmitting glass `or of quartz, if the radiations lie in the ultra violet portion of the spectrum. Suitable electrodes of the cold cathode type, 2, are shown at each end of the tube, but hot cathodesmay optionally be used. Extending longitudinally of the tube, but prefer.- ably terminating short of each electrode is a rejflecting strip 3. As shown in Fig. 2A, it is preferred that thisstrip extend for approximately degrees around the internal periphery of the tube. However. strips extending over a greater or lesser anglemay be employed without departure fromV this invention. Strip 3 may be" nesium and aluminium, but this invention is not qfthe' tube wall covered thereby. It is, however,

' possible to use a relatively less elastic material for the strip and to provide a coating of adhesive material between the strip and the tube wall, in order that the strip shall remain in the proper position, or it is possible to mount or fasten the strip in place by any other means.

In Fig. 2B there is shown Ia variant form 3" which the stripjust described may assume. In this particular form, the apex of the V and extremities 'of the two arms of the V lconstitute three points of contact extending longitudinally along the tube wall. The tendency of the V to expand laterally may be used to hold the strip in place.

Evidently the surface of the reflecting strip should be chosen of a nature to act as an eflicient reflector for the particular wave lengths which are to be emitted from the tube.

For confining the positive column discharge to the proper path thereof, it has been found desirable but not essential that the surface of a conducting reflecting strip which faces this path within the tube be covered with a layer of insulating material I. If the material constituting the surface of the reflector strip be metallic in nature, it may be desirable to place over it an outside layer of some material which is relatively transparent or reflecting, but which is also nonconducting. Many white materials such as aluminum oxide, magnesium oxide, or other metallic oxides, and the like, function both as a suitable rescent type, the visible light proceeds from Va material which is usually non-conducting and only somewhat, transparent. Such phosphors may be used to cover the surface of the reflecting strip, in which case the material functions not only as a light emitter, but also to a certain extent as a light reflector.

Another method of limiting undesired current flow through a conductive reflector is to form the reflector las a series of separate sections, electrically insulated from one another, so that the total voltage which would be required to supply the sum of the cathode-fall voltages as each such section is greater than the maximum voltage of the corresponding length o'f the positive discharge column, during norm-al starting or running. This arrangement will be hereinafter delscribed in greater detail.

an arc correspondingly less than 180 degrees.

4 This arrangement will in many cases eliminate the need for external reflectors. By my use of a separate reflector strip bearing the phosphor.

Asuch type of lamp may be manufactured very simply. whereas it has been found very dimcult to coat the internal wall of a tube over only a portion of the periphery thereof.

In the particular form of construction just described, employing a fluorescent coating, it is evident that the luminous eillciency of the lamp will be increased, at least as far as light emission in a about loss of efficiency. for reasons which have previously been mentioned. The possibility, thus secured, of using a relatively thick coating of phosphor leads to ease in manufacture, since such coating may be applied with a considerable factor of safety above the minimum thickness required to cover the strip.

Measurements made upon a fluorescent type tube employing a reflecting strip covering approximately 180 degrees, and covered with a phosphor, showed a luminous output, over ap-- proximately 180 degrees, of 33 units in comparison with 23 units from a similar tube, drawing the same amount of electrical energy, but employing a phosphordistributed over the entire inner surface .ofthe tube, according to the hitherto prevailing practice in the art.

In many cases, and particularly in the case of the form of strip of Fig. 2B, it is preferred that an insulating coating cover the rear of the reflector strip also. The rear side of the strip may be coated with a less permeable or impervious insulation, such asporcelain enamel, in order to minimize unwanted discharge on this side of the strip.

It will be evident that for ease in replacement,

, it will be desirable that the reflector strip be placed within the tube at a predetermined angular relationship to the 'contact-making pins usually provided in pairs. at both ends of the tube. This will ensure that, when a fixture or other device mounting the two sockets in which the tube is to v ylight source and the eye will be needed because of the opaque strip in the lamp. In either case, the strip serves as a reflecting surface or secondary light source which cannot be reached by dust and dirt.

Referring now to Fig. 3. there is here shown a bulb In. provided at one end with a conventional type of screw base. The electrodes il and l2 pass through the press Il and connect to the terminals of the base. A partition or strip Il extends from the press upwardly to a point near the other end of the bulb. 'I'his partition is shaped and sized to meet the internal walls of the "bulb, s'o that the bulb is divided into two discrete compartments, open to one another only at the upper end of the bulb, and may be formed either of metal. as shown, or of insulating reilective materials. 'I'he sides of this strip, if

formed of conductive material, are preferably coated with a suitable reilective and insulating material 4, such as previously described, so that the latter will tend to minimize unwanted current ilow through the strip.

The discharge extends upwardly in one chamber, crosses the upper end of the bulb, and descends in the other chamber. f i

In Fig. 4 there is shown a tube of the same general type as that shown in Fig. 1, the strip preferably being formed as shown in Fig. 2A or 2B. In this case the reflector strip is divided, at or near the center, so that there are really two strips, discrete from one another, and operating eiectively in series with one another. The general method of operation of this bulb is similar to that already described in connection with Fig, 1. However, the two reflector strips, 31 and 32, present, together with the two electrodes, a total of three gaps, over which the cathode glow discharge must be initiated, before any appreciable current will ilow through the reector system.

With the multiple reector strip employed in this particular form of structure of this invention, the total voltage drop across the gaps of the reflector strips and electrodes will be raised to a point where the positive column will present less resistance to the current discharge than will the reflector system. In this form, bare metallic surfaces may be used, as there is no need for any insulating coating to prevent undesired current now through the multiple reflector strip.

Among the novel advantages of that form of this invention which embodies a separable strip is the fact that the actual application of the insulating or fluorescent material does not have to take place within the relatively narrow confines of the glass tube. The strip is preferably coated before insertion in the tube, thus making possible coating methods not so readily applicable to coating the inside of glass tubes. 'I'hese methods permit the use of iiuorescent powder or pigu ments which do not have to be subjected to the prolonged grinding or ball-milling now customary in making suspensions for coating the inner sur- 'faces of iluorescent lamps.

The less the grinding of the fluorescent particles, the more eiiicient they are. Likewise, less care will be needed in applying this coating than is needed in applying it to an ordinary fluorescent lamp, since excess thickness upon any portion of the strip will not give rise to uneven illumination of the bulb. I have found that coatings made from the usual iluorescent silicates may be as much as several thousandths of an inch in thickness.

It is often 'advantageous to combine in one element a reflector and a starting strip. This embodiment o! my invention is described in the above-identiiled co-pending application.

While there have been described certain nonlimlting forms o! this invention, other forms will be apparent to those skilled in the art, and the charge within said envelope, a plurality of metallic reilectors insulated from one another and substantially coextensive with the path of said discharge and means for substantially preventing discharge via said reflectors, said discharge preventing means including the plurality of insulating gaps separating said reflectorsinto electrically discrete sections and presenting a total series cathode fall of potential in excess of the potential required for establishing said positive column discharge co-extensively with said reiiectols.

2. A device according to claim 1, also including a coating of discrete non-conductive particles substantially completely covering the illuminated surfaces of said reflectors.

3. A device according to claim 2, in which said coating is formed of a iiuorescert material.

4. In a gas discharge lamp, a gas-containing tube, a reflector situated longitudinally along a substantial portion of the path of gas discharge and comprising a plurality of metallic reilective elements, electrically separated from one another and from the tube electrodes and sufficient in number so that the total cathode fall of potential required to establish a discharge via said series of reflective elements exceeds the potential established along said portion of said gas discharge path, whereby electrical discharges via said reflector are prevented, said reflective elements being made of resilient metal strips,`each having a normal width greater than the internal diameter 4 of Asaid tube, each element being deformed from a single plane, whereby the expansive tendency of the elements retains said elements in position within said tube.

MILES PENNYBACKER.

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

UNITED STATES PATENTS