US2030963A - Discharge tube - Google Patents

Description

' Patented Feb. 18, 1936 UNITED STATES,

mscnAneE TUBE Claude, Nanterre, France, assignor to Socie't Anonyme pour les Applicationsde lElectricit et des Gaz Bares Etablissements Claude-Paz & Silva, Paris, France, a corporation of France No Drawing. Application April 8, 1934, Serial No.

718,885. In France April 8, 1933 8 Claims. (01. 176-122) It has already been proposed to modify the light emitted from electric discharge tubes or ,receptacles. In one process, the glass envelope is constituted by colored or fluorescent substances, or is covered by them. It has also been proposed to produce a kind of light specially chosen, for example a sky-blue effect, by the application or use of a filter in conjunction with a mercury discharge lamp, or to fit up a double walled receptacle for the like purpose. It has also been proposed to mount a luminous. discharge tube in a recess, the interior of which is coated with a suitable phosphorescent or other lining, or again, to provide an axial partition extending the whole length of the interior of the electric discharge tube: and having on at least one side a coating of a fluorescent substance, for example zinc sulphide, oxide-of scandium, or calcium tungstate, orentirely composed of a fluorescent 20 material. Coatings of gold or silver have also been proposed with, as filling materials, sodium,

cadmium or mercury. There has been suggested a combination of incandescent lamps and discharge tubes constituting table lamps, standard lamps, and hanging or ceiling lamps; arranged with the hot electrodes, heating, igniting and stabilizing apparatus'in the feet or the handlesof the saidlamps. Finally, it has been suggested to apply a homogeneous and adhesive coating to the interior of electric discharge tubes by spraying luminous paint over a binder of low surface tension and high viscosity, as for example a polyvalent alcohol such'as glycerine, and to remove the binder or adhesive by means of heat or vacuum or both of these; it has also been proposed to add to the adhesive to be volatilized,

compounds of metalloid elements such as boric acid, borax or other boron compounds, or sodium silicate.

As far as applicant knows, no tube provided with an internal luminous coating has yet been manufactured commercially.

An object of the present invention, is to provide electric discharge tubes and receptacles for as the adhesive must not be in excess and that this 'commercial'use, the interior of which is coated- Bass adhesive or binder will only have the desired effect when it is. applied in the form of an extremely thin and homogeneous film, and that, finally; in order to. avoid undesirable deposits of metallicvapors, the additionof the mercury or any other metal must. be carefully measured according to the particular conditions applicabl It is also. necessary to take care to ensure the ceptacles by preventing as far as possible any satisfactory construction of the discharge rediffusion of hydrocarbon vapors on the final sealing-in after the evacuation and filling'up with 4 neon or any other gas or vapor.

. A further advantage of the present invention consists in that, by a suitable selection of colorlessor colored glass constituting the discharge.

receptacle, in combination with the luminous coating which it is desired to apply,,it is possible to produce color effects which hitherto it has been impossible to. obtain. For example, by using a tube of green glass and the known'mixtur'e of' mercury, neon, argonand helium, as the conduc tive gas of the luminescent discharge, and by coating the inside of the tube, in accordance with -'the invention, with a luminous material such as a mixture of zinc sulphide and cadmium sulphide, there is obtained a yellow color, whereas hitherto j the known dischargewas of a green color.

Evidently a large variety of luminous effects thus become possible by varying the .glass, the filling gas, and the internal luminous material;

'In carying' out the present invention, whether the glass used is colorless or colored, and, whatever may be the filling gas or the internal luminous coating, it is possible to construct novel discharge tubes or receptacles provided with the internal luminous coating, and in which the electric contactis established-by means of suitable terminals capable of insertion in, a handle or hollow support equipped with corresponding conor other auxiliary apparatus for the ignition or maintenance of the discharge in the tube.

It is also necessary to prevent the production of unusual reactions which would counteract the effect of. the luminous coating or which would tend to diminish the adhesion of the luminous substance to thefinnersurface' of the glass, or

which would form deposits adapted to soil the discharge tubes. To better understand the. man- 45, tacts, containing when necessary the transformer ufacture of the tubes according to the presentinvention, there will be given the following special particulars, it being understood that they do not restrict the scope of the invention.

A colorless or colored tube is given the final shape desired,'for example that of a circle or-any other shape; it is carefully freed from all fatty or like matter by the known process of washing withalcohol and then drying with ether. By

means of a string passed through the tube, as is done for glass beads, there ispassed through the tube a plug of fabric or a sponge which has been impregnated to the desired extent with a temporary binder; for example glycerine containing boric acid in solution. This process has however the disadvantage of causing irregularities and interruptions in the deposit of the liquid containing the luminescent substances; furthermore,

it often happens and especially when the electric discharge apparatus has curves, or pronounced bends, that the string or the tube breaks. These v disadvantages may be avoided by producing the movement of the impregnated body by the effect of a regulated force. In the elbows in particular the force should be greater than in the straight parts. The movement of the body may be obtained by means of the pressure of thegas, the said pressure being regulated for example by means of a two-way cock. on passing elbows. the pressure will be increased progressivel and, when the body has passed the elbow, the pressure will be brought to its initial value. This pressure the other face may be obtained.

. The displacement of the impregnated, body in the discharge apparatus may also be effected by the action of a magnetic field on one or more magneticmasses connected to the said impregnated body. This magnetic field may be adjustable-so as to be increased with agview to the movement of the "body in the bent part of the tube.

sive, the plug is passed along in the opposite direc- As regards the character of the adhesive, applicant has found that the mixture of one part of boric acid and of five parts-of anhydrous glycerine is very. suitable for the operation. In order to ensure the homogeneity; of the temporary adhetion, the operation being repeated, using, if desired, decreasing quantities of glycerine or similar products. ,To complete the uniform application of the glycerine or the like, it is'even essential in order to remove any excess beyond the quantity necessary to constitute a very thin and homogeneous film, to pass through. the tube a dry plug or sponge and torepe'at the operation in the reyerse direction to remove as far as possible any trace of glycerine or the like, visible oncareful examination. Ony then is the luminescent substance introduced into the tube. This is effected by shaking the tube, rfwhich there is an excess for example of sulphide of zinc, containing the ingredients necessary for producing the luminescence and withdrawing by shaking or other means any material not adhering to the film of glycerine. or like product; itshouldbe pointed 2,oso,oos V out in this conn'ection that any accumulation of glycerine or similar product in the bends would cause a diminution of luminosity.

After the luminous coating has been applied on to the internal surface of the tube, the temporary adhesive is removed by heating. when the mixture of glycerine and boric acid has been used, the inventors have found that it is advis- .able to heat the tube slightly above the boiling point of the glycerine, and to maintain a temperature of 330 to 350 C. for about twenty to thirty minutes. 1

The heating is stopped when the temperature of 350C. is reached, and the tubes are allowed to slowly cool. The electrodes are then inserted and sealed; 1 the sealing must be carried out in such manner as to prevent any diffusion of hydrocarbon gases into the discharge tube. If considered necessary, a spirit flame may be used to this end. After'this, the tubes are ready for the vacuum to be created, and this is obtained by the known process, taking care to free the electrodes from any occluded gas, by heatin by means of high potential or the like, and also reducing the temperature to the limit which will not cause deterioration'of the luminous substance. In general, a temperature of 350 C. approximately is necessary and has given satisfactory results. 1

Before sealing the tube, one or more rare gases from the air are introduced at a low pressure and, if desired, a small quantity of metal, such as mercury, taking care to avoid any excess of the said metal beyond that which is actually necessary.

The discharge receptacle or tube is now ready for insertion in the contact pieces of a support, handle or other. similar apparatus which, for

greater conveniencewill be hollow and in which the supply terminals, the transformer-if necessaryand another auxiliary apparatus required for the ignition and the stabilization of the discharge will be fitted.

I claim:

1. The method of manufacturing gas filled electric luminous discharge tubes and the like having. their inner surface provided, by the intermediary of a. volatilizable cementing agent, with a layer of luminescent or phosphorescent substance, comprising applying the. cementing agent in an extremely thin andsuniform layer on said surface by wiping with a plug of elastic absorbent material impregnated with the cementing agent, depositing the luminescent or phosphorescent substance in a thin film on the wiped surface. and eliminating the cementing agent.

2. The method of manufacturing gas filled electric luminousdischarge tubes and the like having their inner surface provided, by the intermediary of a volatilizable cementing agent, with a layer of luminescent or phosphorescent substance, comprising applying the cementing agent in an extremely thin and uniform layer on said surface by wiping with a plug ,of elastic absorbent material impregnated withlthe cementingagent, attenuatingthe layer of cementing agent by wiping with a plug of dry elastic material, depositing the luminescent or phosphorescent substance in a thin mm on the wiped surface. and eliminatplug is moved 5. A method according to claim 1 in which the plug is moved through the tube by means of a magnetic field operative upon a magnetic body embedded in the plug.

6. A method according to claim 1 in which the luminescent substance is introduced along with and in solution in the cementing agent.

7. The method of manufacturing gas filled electric luminous discharge tubes and the like having their inner surface provided, by the intermedian of a volatilizable cementing agent, with depositing the luminescent or phosphorescent,

substance in a thin film on the wiped surface, and sealing the electrodes in the tube with avoidance of diflfusion of hydrocarbons into the tube.

8. A method according to claim 7 in which the electrodes are scaled into the tube with the aid of a spirit flame.