US2491880A - Method of gettering incandescent lamps or discharge tubes - Google Patents

Description

Patented Dec. 20, 1949 ITE nrnon or, GETTERING INCANDESCENT nawirson n scnrmcnrnnns Johannes Antonius Maria van Liempt, Eindhoven,

Netherlands, assignor to General Electric Company, Schenectady, N. Y.

No Drawing. Application April 6, 1946, Serial No. 660,301. In the Netherlands March 4, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 4, 1963 4 Claims.

The invention relates to a method of gettering incandescent lamps or discharge tubes whose glass components consist, at least to a large proportion, of hard glass, with the aid of a getter which is provided in the bulb or envelope of the lamp or tube and which substantially consists of phosphorus. If the glass components of incandescent lamps or discharge tubes consist of soft glass, phosphorus may be utilized as the getter without any particular precautions. In this case, for example a suspension of phosphorus in alcohol is sprayed on to an electric energy translation element such as the filament or the anode. After the stem has been sealed-in, the bulb or tube is exhausted and sealed-ofi, as the case may be, after being filled with gas. During the subsequent burning out of the incandescent lamp or the high-frequency heating of the anode the phosphorus vaporizes and performs the known getter action. With bulbs or tubes consisting of hard glass the above-mentioned method cannot be adopted. By hard glass are meant hereinafter glasses whose coefficients of linear expansion between 25 and 325 C. are lower than 6O 10' For in sealing components into bulbs or tubes consisting of hard glass and in the hotexhaustion of such bulbs and tubes use is made of such high temperatures that the phosphorus is burnt or Vaporizes and, as the case may be, is pumped off.

This drawback is removed by the method according to the invention. In this method the particles of the getter material are coated with a film, owing to which during the sealing-in of components and the hot-exhaustion of the bulb or tube vaporization of the getter material is prevented whilst when heated to a temperature which exceeds the temperature utilized in the sealing-in operation and in the hot-exhaustion this film is vaporized. After being sealed-on the bulb or the tube may be burnt out again in the usual manner or the anode may be submitted to high-frequency heating respectively, at which high temperature the film vaporizes so that it no longer prevents the vaporization of the phosphorus.

According to one mode of realization of the method according to the invention, the film is formed by means of hydrolysis of an ester of silicic acid. This film can be produced in a very simple manner. The filament or the anode is immersed, for example, in a suspension of phosphorus in a solution of ethyl silicate in methyl alcohol and water. Then the filament or the anode is dried in a current of hot air, during 2 which treatment there occurs hydrolysis and the film is formed, which film consists of silicagel and covers the phosphorus particles on the filament or the anode. During the hot-exhaustion of a bulb or tube into which such a filament or anode is sealed, the silicagel is converted into SiOz without the stratified structure being lost. After the bulb or tube has been filled with gas, if desired, and sealed off, the lamp or tube may be burnt out in the ordinary manner or be submittedtohigh-frequencyheatingrespectively. During this operation the S102 film vaporizes whilst at the same time the phosphorus vaporizes and the known getter action takes place. It is possible that a slight white deposit of S102 is produced on the wall of the bulb or tube, more particularly if use were made of an excessive quantity of ethyl silicate. If use is made of the proper quantity of ethyl silicate, this white deposit is so slight that there is no question of any influence being exerted on the luminous flux issuing from the incandescent lamp or discharge tube.

What I claim is:

1. The method of gettering electrical devices of the class comprising sealed envelopes containing electric energy translation elements which comprises coating a translation element by immersion thereof in a suspension of phosphorus particles in a solution of ethyl silicate in methyl alcohol and water, drying the coating to form a film of silica gel on the phosphorus particles by hydrolysis of the ethyl silicate, sealing the said element into an envelope and then hot-exhausting the envelope and sealing it off at temperatures which would be sufiiciently high to vaporize the phosphorus in the absence of the silica gel film thereon, and subsequently heating the said element to a temperature suiiiciently high to vaporize both the phosphorus and the said film thereon.

2. The method of gettering electrical devices of the class comprising sealed envelopes of hard glass containing electric energy translation elements which comprises introducing into the envelope a getter consisting of phosphorus particles coated with a film of silica, sealing the envelope and then hot-exhausting it and sealing it off at temperatures which would be sufiiciently high to vaporize the phosphorus in the absence of the silica coating thereon, and subsequently heating the getter to a temperature sufiiciently high to vaporize both the phosphorus and the said film thereon.

3. An electrical device of the type comprising a sealed envelope of hard glass containing an electric energy translation element and a getter consisting of phosphorus particles coated with a film of silica REFERENCES CITED 4. An electrical device of the type comprising The following references are of record in the a sealed envelope of hard glass containing an file of this patent: electric energy translation element coated with a getter consisting of phosphorus particles having UNITED STATES PATENTS thereon a film of silica gel. Number Name Date J OHANNES ANTONIUS MARIA VAN 1,849,056 Crowley Mar. 15, 1932 LIEMPT. 2,368,060 Wooten Jan. 23, 1945