US2520513A - Fluorescent sign lamp - Google Patents

Description

ug. 29, 1950 P. sERl-:No 2,520,513

FLUoREscENT SIGN LAMP Filed April 20. 1949 Patented Aug. 29, 1950 UNITED STATES 4rui'lsin OFFICE l. This invention relates to signs, and, more particularly, is concerned with fluorescent S1211 lamps.

Even more specically, the present invention pertains to thattype of fluorescent sign lamp wherein the sign comprises a plurality of letters, characters and/or symbols (all hereinafter reicrred to as characters) fashioned from iluorescent material and carried by an elongated plate of insulating material which is located within a transparent tube. The tube is filled with rareed gases and is arranged to passl an electric discharge which activates thefiuorescent malterial of the characters. Signs of this type conventionally have the characters formed by tracing the same with fluorescent powders on the elongated plate.

In present-day manufacture of signs of the character described. many diiiculties are present which have made the signs delicate, expensive and complicated. The principal difiiculties have been: failure to obtain a clean and uniform tracing of the characters on the elongated plate, unsatisfactory mounting of the elongated plate in the transparent tube, special care in handling the various components during manufacture, inability to secure a simple and ilrm assembly of the parts in the completed sign, and complicated devices to direct the electrical discharge and obtain a sufilcient intensity of light emanation from the uorescing characters.

It is an object of my invention to provide fluorescent sign lamp wherein the foregoing diilloulties are overcome.

It is a more speciiic object of my invention to provide a fluorescent sign lamp of the character described in which the characters can be traced quickly and easily -by lling in shallow depressions of proper outline so that the finished characters are clean and uniform.

It is another specific object of my invention to provide a fluorescent sign lamp of the character described wherein the plate is indirectly supported by the tube thereby to obtain a iirm and qiuckly assembled plate mounting which will not cause breakage of the fragile tube and plate during either construction or use.

It is another specific object of my invention to provide a iiuorescent sign lamp of the chan acter described wherein the plate mounting constitutes resilient members and cushions so that, although the mounting is firm, the plate, nevertheless, will not exert any sudden or substantial pressure against the tube.

It is another specinc object of my invention to provide a fluorescent sign lamp of the character described wherein the plate is so positioned in the tube that the full electrical discharge passes in front of the plate so that a hitherto unobtained degree of brilliance is attained by the fluorescent characters. l l

Other objects of my invention will in part be oittious and in part will be pointed out hereina r.

My invention accordingly consists in the features of construction, combinations of elements and arrangements of parts which will be exemplified in the constructions hereinafter described and illustrated and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings in which are shown various possible embodiments of my invention,

Fig. 1 is a front view of a iiuorescent sign lamp constructed in accordance with my invention;

Fig. 2 is an enlarged axial section through one of the ends of the sign in a plane perpendicular to the character-carrying plate;

Figs. 3 and 4 are sectional views taken substantially along the line 3 3 and 4 4, respectively, of Fia. 2;

`Iiig. 5 is a broken-away perspective view of the end of the sign shown in Fig. 2; and

Figs. 6 and 7 are transverse sectional views through ends of iluorescent sign lamps having modied forms of plate mountings embodying my invention.

Referring now in detail to the drawings, and, more particularly. to Figs. 1 through 5, the reference numeral Iii denotes a fluorescent sign lamp embodying my invention. Said lamp comprises an elongated transparent tube ii which, conventionally, is Vfabricated from glass and is of circular cross-section, it being understood that the particular conilguration of the cross-section can be varied to suit consumer demand. Both ends of the tube are tapered to hermetically closed stems il. The tube is evacuated 'through a stub i8 which subsequently is sealed. Before sealing, however, the tube is charged at a conventional pressure with one or more of the rare gases which commonly are used in standard uorescent lamps. By way oi example argon or krypton may be employed at a pressure of between 0.5 to 2 mm. of mercury. In addition a small amount of mercury vapor can be present.

At the ends of the tube I provide the usual electrodes il mounted on lead-in wires t-l! which are conventionally sealed in the stems. The

electrodes are shown as representative either of the "cold" electrode type, operating with a nigh voltage drop and a high strikingvoltage, or of the oxide-coated heated electrode type, operating with a low voltage drop and starting with a comparatively low striking voltage. As is well understood. both types are suitable for the purpose of maintaining an electric discharge in. an attenuated gas. For example, elongated cylinders of nickel or iron, coated with barium oxide, may be used as electrodes. The lead-in wires run to terminals 22 which, as illustrated, may be of the type adapted to be plugged in suitable sockets. Energy is supplied to the electrodes through any conventional circuit. The ends of the tube are housed in shells 2l which, conveniently, are made from a plastic, e. g. a phenol formaldehyde condensation resin. The tubes are secured to the shell, for example by cement 26, and'openings are provided for passage and support of the terminals 22.

Located within the tube I2 andextending over substantially its entire length, is a plate 28 which, desirably, is made of an electric insulating material, e. g. glass. The plate has a breadth which is somewhat smaller than the inside diameter of the tube. Pursuant to a principal feature of my invention, the plate is odset from the longitudinal axis of the tube. In other` words, the plate, which is thin and has parallel, plane front and back surfaces, and, moreover, which is arranged with said surfaces parallel -to this axis of the tube, has its front surface spaced from said axis in a direction radially of the tube and its rear surface located on the same side of, said axis. It is on this front surface of the plate that the fluorescent characters are carried, so that said characters face the major portion of the tube space through which the electric discharge between the electrodes passes. I have found that such an arrangement results in an appreciable increase in brilliance compared to an arrangement in all respects similar save for the aforesaid placement of the plate, such plates heretofore having been located so as to include the longitudinal axis of the tube.

Means is provided to hold the plate in its stated position. As shown in Figs. l through 5, said means comprises a spring plate ring 30 cornpressed between the tube and the plate, one such ring being provided at each end of the plate. To avoid contact of the plate with the tube, each end of the plate is Wrapped in a ribbon 32 which is yielding and, preferably, is electrically nonconductive and a poor heat conductor. Examples of materials of ,this nature are asbestos and glass fiber ribbons. By way of illustration, the ribbon is 20 mm. wide and about 2 mm. thereof is permitted to extend beyond the edge of the plate. One turn with some overla-p (see Fig. is wrapped about each end of the plate before the plate is inserted in the tube.

The ring 30 can be simply made from a fiat strip of spring steel provided with a notch on each edge thereof near its ends. The notches are on opposite longitudinal edges and have depths equal to approximately half the width of the strip. The strip is bent to overlap its ends and register the notches, and' the latter are interengaged to fix the ring in an approximately circular shape. The ring then is compressed and inserted between the tube and plate. Contact between the ring and tube is avoided by wr'apping the junction of each ring with a ribbon 34 similar to the ribbon 32 and placing said wrapped junction adjacent the tube. After the ring is released, it will press its associated end of the plate against the tube and rmly and resiliently hold it in position. -the ribbons serving to cushion any shock experienced during assembly or use. A further advantage of this construction is that it permits expansion of the parts during the heating incident to obtaining a vacuum, and also a1- lows large tolerances and slight movements of the parts without causing breakage because of the imposition of sudden or substantial stresses on the delicate tube. Other rigid mounting systems that will not permit movements, or will allow parts to come into contact at different'temperatures or because of diiferent heat conductivity characteristics, will result in breakage.

The ring functions to hold the plate against transverse movement. Means also is` included to hold the plate against longitudinal movement. Such means comprises a nub J8 near each end of the tube and at an end of the plate 2l. Said nubs are formed by locally heating the tube at the desired regions until the tube softens and then indenting the tube with a blunt rounded point. This operation is perfumed after the plate is in the tube and the nubs thus are pressed against the ribbons 22.

The characters are provided by forming shallow depressions 2l of proper outline in the plate 28 and filling the depressions with a fluorescent material 40. The depressions are fashioned in any suitable manner, for instance by sand-blasting through a. stencil, chemical etching, photoengraving or molding when the plate is made.

Over the area of the plate thus treated there is applied, as by',brushing or spraying, fluorescent powders in suspension in a varnish, lacquer or other suitable iluid carrier of the type commonly used for the application of such powders on glass tubes. If desired, powders of different composition can be employed on different areas of the plate in order to obtain differently colored characters when the tube is activated. After the carrier is dry, the front surface of the plate is scraped with 9. straight edge to remove all fluorescentf powder except that inside the depressions. Then the plate is heated to volatilize the solidified carrier, as is done in the manufacture of fluorescent lamps. By way of example, a sat isfactory depth for the depressions is about 0.5 mm. It will be apparent that the formation of the characters is carried out before insertion of the plate in the tube.

It is desired to point out that, when the depressions are formed by actual removal of portions of the plate, i. e. by etching, the surface to which the powders are applied can be thoroughly cleaned and there is no likelihood that the powders will fall of! during use, as now often is the case, because the surfaces to which the powders are applied cannot be kept perfectly clean while manufacturing the plate.

It may be mentioned that the' sequence of steps in the assembly of the sign is to insert the prepared and wrapped plate in the tube, place the rings in posit on, form the nubs, insert the electrodes, form t e stems, evacuate the tube, charge the tube, close the stub, connect the terminals, apply the shells, and mount the terminals.

In Fig. 6 I have shown a fluorescent sign lamp l2 which is similar in all respects to the lamp I0 except for the means to hold the character plate against transverse movement. All parts identical u with parts of the lamp I0 are denoted by the same andere 5 a reference numerals primed. The plate Il' ishcld might be made in the embodiments above set against transverse movement by a ltwo-,ended forth, it is to be understood that all matter herein compression spring 4| having a loop 4l interdescribed, or shown in the accompanying drawmediate its ends. Refractory beads 4l. 50, e. g. ings, is to be interpreted as illustrative and not ceramic beads, are mounted on the ends of the 5. in a limiting sense.

spring.l One bead bears againstthe inner sur- Having thus described my invention, I claim face of the tube l2'- and the other against the asnew and desire tosecure by Letters Patent: plate 2l', the latter bead pressing either directly l. A fluorescent sign lamp comprising a sealed against the plate or engaging the ribbon 32'. To elongated transparent tube, electrodes adjacent hold the spring in place, the tube I2 is heated 10 opposite ends of said tube, a charge of attenuated in the region of the bead 4B. When the tube gas in said tube, a plate in said tube, said plate softens slightly this bead will push out the wall having fluorescent characters on a surface therea short distance to form a depression 52 in which 0f, the width of said plate being less than the the bead 48 remains seated. major cross-sectional dimension of the tube. and The foregoing plete mountinss are resilient: is means to locate said plate in a position onset however, in accordance with another aspect of from the eeuu-9,1 longitudinal axis of the tube myinvention the character nleteisrisidlymvuntwith its character-carrying surface extending ed, this form of the invention being illustrated lengitudmeuy of the tube and radially spaced in F18 7 wherein all Darts Similar 150 those 0f from said axis and the opposite surface of the the lamp It aredenoted by the same reference n plete disposed en the seme side of the exis end numerals double primed. The sign Il shown epeeed further therefrom, in F18- '7 has its 5ba-meter P1te n" held in 03:' 2. Afiuorescent lamp S1811 as set forth in claim eet position by e Deir of meuntin members it i wherein the locating means composee e, resilone at each end o! the plate. Each such memgent member under compressione-between the bei @Prises a Small rod u hvm *im 25 character-carrying surface of the plate and the arms 8l. B2 on an end thereof, so that the memewue wen ef the tube, bei' i8 approximately in the Shape 0f 9' Y o. 3. A iluorescent lamp sign as set forth in claim the rod s., i. e. the of the Y, 110ml 18 1 wherein the means comprises a resuprovided which engages or nts into a correspondgent member under compl-essieu between the mg nomh on the end edge 0f the 30 cmwterming surface of the and 2|", s0 that, two ends thus Supported, the wan of the tube and a cushioning plete is rigidly held 1n the tube- T keep the ciment disposed between the opposite mfaee members in place, each of the end of of the and the adjant wan of the tube. the Y is fashioned an mdentauon wm 4. A nuorescent as set forth in the wan 0f the after for instan@ u 1 wherein me means comprises a spring by the application of heat, is pushed. the result- ,me under mmm-essieu between the characteringconnguration Clearly mmctedinm- 7. um mfm of the and the opl-site lfdesiredathinplyofasbestosorslasswool mefthetube,

ribbon may be inserted between the members It P50170 ammo. and ends oi' the plate 28" to discourage rocking 40 of the plate. It will be observed that in this form REFERENCES CITED of my invention the character plate does not touch the tube and accordingly it is not necessary to interpose any cushioning element between me d um mnt' um plate and tube, .u UNITED STATES PATENTS It thus will be seen that I have provided signs Number Name Date which achieve the several objects of my invention 3,113,000 Wojtkowiak MIIU 17. 1938 and are well adapted to meet the conditions of 3,177,710 Gordon Oct. 31. 1939 practical use. 2,335,712 Price Dec. 24. 1040 Asvarious possible embodiments mizht bemadc I0 3,373,127 Noel Feb 3. i942 of the above invention, and as various changes 3,430,534 xenium et a1. Aug: a0, 1949 The following references are of record in the

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