US3338737A

US3338737A - Quartz tube coating

Info

Publication number: US3338737A
Application number: US296032A
Authority: US
Inventors: Walter A Boyce
Original assignee: Westinghouse Electric Corp
Current assignee: Philips North America LLC
Priority date: 1963-07-18
Filing date: 1963-07-18
Publication date: 1967-08-29
Anticipated expiration: 1984-08-29

Description

Aug- 29, 1967 w. A. BOYCE QUARTZ `TUBE COATING Filed July 18, 1963 .Nom

PQEE :com o .odm @MEE ou $525 w. mom 9.0mm o 9,0m@ 50m2 mnd zm NG TII United States Patent Oce 3,338,737 Patented Aug. 29, 1967 3,338,737 QUARTZ TUBE COATING Walter A. Boyce, West Orange, NJ., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 18, 1963, Ser. No. 296,032 4 Claims. (Cl. 117-94) The present invention relates to the method of applying a light impervious coating to the quartz envelope of a high temperature heat lamp.

Quartz lamps capable of producing temperatures of several hundred degrees are finding a steadily increasing demand for numerous usages. However, in many of such applications the production of light along with the high temperature heat is undesirable. In order to materially decrease if not eliminate the light generation, it has been the practice heretofore to utilize a high temperatureresistant colored vitreous tubing, such as that now well known in the glass industry as vycor tubing, .as the envelope for these high temperature lamps. Because of the high cost of this colored vycor tubing resort has also been taken to the application of noble metal lusters to clear quartz envelopes. Heretofore, such luisters have not proven satisfactory due to lack of heat stability, chipping, or lightness of color which renders them insuiiiciently light impervious.

It is accordingly the primary object of the present invention to provide a method of coating the quartz envelope of a high temperature heat lamp which renders such coating heat stable throughout the operating temperature range of the lamp.

Another object of the present invention is the provision of a method for applying a light impervious coating to the quartz envelope of a high temperature heat lamp which is heat stable throughout the useful life of the lamp and of a desired color density to maintain light imperviousness during operation of the lamp.

The foregoing objects of the present invention, together with other objects which will become apparent from the following description, are achieved by applying several thin coatings of a preselected composition to the quartz envelope of a high temperature heat lamp and tiring such coated lamp after the application of each coating at a temperature within a definite preselected range'.

The present invention can be readily understood by reference to the accompanying drawing wherein:

FIG. l is a cross-sectional view of the quartz envelope of a high temperature heat lamp provided with a heat stable red coating in accordance with the present invention, and

FIG. 2 is a block diagram showing the various steps of the method of the present invention for applying the heat stable coating to the quartz envelope of a high temperature heat lamp.

Referring now more specifically to FIG. 1, the quartz envelope 5 of a high temperature heat lamp is therein shown which is provided with a heat stable red coating 6. The coating material itself is a luster which may be prepared as a resinate of metals, such as colloidal gold, or the like, dissolved in a suitable organic binder, as for example, oil of lavender, turpentine, toluol, or the like, in the ratio of about forty parts of luster to twenty-live parts solvent and to which glass frits are added to give bonding to the fired tubing. The method of applying the coating is diagrammatically illustrated in FIG. 2 wherein a first thin coating of such heat stable luster is applied by brushing or dipping. However, the latter method is preferable because numerous lamps with their end seals and lead-wires protected by rubber covers can be racked vertically and immersed in a stainless steel tank containing the coating material. Uniformity of coating is then achieved by withdrawing the rack containing the numerous lamps at a rate approximating three or four feet per minute.

Following withdrawal from the dipping tank, which thus completes the rst step as shown by the rectangular block 7 in FIG. 2, the lamps are allowed to drain and dry for several minutes and then the rubber covers are removed from the ends of such lamps and the latter placed in a stainless steel tiring rack with the ends then covered with ceramic insulating material. The loaded stainless steel rack is then placed on the traveling belt of the furnace and such rack allowed to travel into the furnace firing zone before the furnace door is closed thus allowing the volatiles to be removed easily from the furnace atmosphere. The lamps lare next tired at a temperature ranging from 650 C. to 850 C. for fifteen minutes, as indicated by block 8 in FIG. 2, and then removed from the furnace and after unloading from the rack permitted to cool to room temperature, as shown by block 9 of FIG. 2.

The same procedure is twice repeated, as indicated in FIG. 2 by the block diagram, but such lamps are re- -versed in the stainless steel rack each time when dipped to facilitate uniformity of thickness as between respective layers and upon cooling following the iinal dip, the ceramic end covers are removed and the lamps are ready for use. By utilizing the foregoing method of coating, three complete thin layers each of substantially the same thickness are applied thus producing a high temperature lamp having a heat stable red coating.

It should thus become obvious to those skilled in the art that a method of applying a red light impervious coating to a high temperature quartz lamp has been herein provided wherein such coating is heat stable at the high operating temperature of such lamp. Moreover, such lamp with its integral red coating may be operated for many hours of useful life without the coating crazing, chipping or flaking and at the same time maintaining a substantially constant color density with no noticeable deterioration during lamp life.

Although a specific embodiment of the present invention has been herein shown and described it is to be understood that still further modifications thereof may be made without departing from the spirit and scope of the appended claims:

I claim:

1. The method of coating a high temperature lamp with .a light impervious red coating that will not cr-aze, chip or flake, as a result of the high operating temperatures of said lamp comprising preparing a metallic luster by 'admixing approximately 40 part-s of colloidal gold with approximately 25 parts of toluol and a suitable amount of glass fri-t, applying a thin layer of said metallic lus-ter lto the envelope of s-aid lamp, allowing such layer to dry, tiring such layer in a furnace at a temperature ranging from about 650 C. to 850 C. for approximately fifteen minutes, cooling the coated lamp to atmospheric temperature, applying a second similar lthin layer to the lamp envelope, drying, firing at same `temperature for same period of time, and cooling it, and thereafter applying a third simil-ar thin layer to the lamp envelope and again drying, firing at about 650 C. to 850 C. for approximately fifteen minutes, 'and cooling it to atmospheric temperature, to form a composite light impervious heat stable coating.

2. The method of coating a high temperature lamp with a light impervious heat-stable red coating that will not craze, chip o1 flake, as a result of the high operating temperatures of said lamp comprising dipping said lamp -in a tank of metallic lusterv and withdrawing it at the rate of about three or four feet per minute to form a thin layer on the envelope of said lamp, allowing such layer to dry, tiring the coated lamp in a furnace, cooling the coated lamp to atmospheric temperature, dipping said lamp a second time in the tank of metallic luster and withdraw-ing it at the same rate to form another thin layer, drying, tiring and cooling ias before, and thereafter dipping the lamp in the tank of metallic luster and again withdrawing it at a rate of about three or four feet per minute to form a third thin layer on the envelope of the lamp, drying, ring, and cooling the lamp to atmospheric temperature, to form a composite light impervious heatstable coating.

3. The method of coating a high temperature lamp with a light impervious heat-stable red coating that will not craze, chip or flake, as a result of the high operating temperatures of said lamp comprising dipping said lamp in a tank of metallic luster and withdrawing it at the rate of about three or four feet per minut-e to form a thin layer on the envelope of said lamp, lallowing such layer to dry, firing the lamp in a furnace -at a .temperature ranging from about 650i" to 850 C. for approximately fteen minutes, cooling the coated lam-p to atmospheric temperature, reversing the lamp end for end and dipping it a second time in the tank of metallic luster and withdrawing it lat the same rate to form another thin layer, drying, firing in the furnace at the same temperature range and time period, -cooling to atmospheric temperature as before, and thereafter `again reversing the lamp end for end and dipping it in the tank of metallic luster with Withdrawal thereof at the rate of about three or four feet per minute to form a third thin layer on the envelope of said lamp, drying the coating, firing again at a temperature of about 650 C. to 850 C. for approximately tifteen minutes, and cooling to atmospheric temperature, to form a compositeA light impervious heat-stable coating.

4. The method of coating a high temperature lamp with -a light impervious heat stable red coating that Will not craze, chip or ake, as the result of high operating temperatures of said lamp comprising preparing a metallic lustre by admixing approximately parts of colloidal gold with approximately 25 parts of .toluol and a suitable amount of glass frit, dipp-ing said lamp in a tank of said metallic lustre and withdrawing said lamp at the rate of about three or four feet per minute to form a thin layer on the envelope of said lamp, allowing such layer to dry, ring the lamp in a furnace at a temperature ranging from about 650 C. to 850 C. for approximately 15 minutes, cool-ing the coated lamp to atmospheric ternperature, reversing the lamp end for end and dipping it a second time in the tank of metallic lustre and withdrawing it a-t the same rate to form another thin layer, drying, ring in the furnace at the same temperature `range and time period, cooling to atmospheric temperature as before, and thereafter 'again reversing the lamp end for end and dipping it in the tank of metallic lustre with withdrawal thereof Iat the rate of about three or four feet per minute to form a third thin layer on the envelope of said lamp, drying the coating, tiring vagain at a temperature of about 650 C. to `850 C. for approximately l5 minutes, Iand cooling to atmospheric temperature to form a composite light impervious heat stable coating.

References Cited UNITED STATES PATENTS 2,919,208 12/1959 Treat 117-113 2,972,549 '2/ 1961 Goldsmith 117-113 3,206,632 9/1965 Rokosz 117-333 3,207,838 9/ 1965 McCormack 117-124 ALFRED L. LEAVITT, Primary Examiner.

W. L. SOFFIAN, E. B. LIPSCOMB III,

Assistant Examiners.

Claims

1. THE METHOD OF COATING A HIGH TEMPERATURE LAMP WITH A LIGHT IMPERVIOUS RED COATING THAT WILL NOT CRAZE, CHIP OR FLAKE, AS A RESULT OF THE HIGH OPERATING TEMPERATURES OF SAID LAMP COMPRISING PREPARING A METALLIC LUSTER BY ADMIXING APPROXIMATELY 40 PARTS OF COLLODAL GOLD WITH APPROXIMATELY 25 PARTS OF TOLUOL AND A SUITABLE AMOUNT OF GLASS FRIT, APPLYING A THIN LAYER OF SAID METALLIC LUSTER TO THE ENVELOPE OF SAID LAMP, ALLOWING SUCH LAYER OF DRY, FIRING SUCH LAYER IN A FURNACE AT A TEMPERATURE RANGING FROM ABOUT 650*C. TO 850*C. FOR APPROXIMATELY FIFTEEN MINUTES, COOLING THE COATED LAMP TO ATMOSPHERIC TEMPERATURE, APPLYING A SECOND SIMILAR THIN LAYER TO THE LAMP ENVELOPE, DRYING, FIRING AT SAME TEMPERATURE FOR SAME PERIOD OF TIME, AND COOLING IT, AND THEREAFTER APPLYING A THIRD SIMILAR THIN LAYER TO THE LAMP ENVELOPE AND AGAIN DRYING, FIRING AT ABOUT 650*C. TO 850*C. FOR APPROXIMATELY FIFTEEN MINUTES, AND COOLING IT TO ATMOSPHERIC TEMPERATURE, TO FORM A COMPOSITE LIGHT IMPERVIOUS HEAT STABLE COATING.

4. THE METHOD OF COATING A HIGH TEMPERATURE LAMP WITH A LIGHT IMPERVIOUS HEAT STABLE RED COATING THAT WILL NOT CRAZE, CHIP OR FLAKE, AS THE RESULT OF HIGH OPERATING TEMPERATURES OF SAID LAMP COMPRISING PREPARING A METALLIC LUSTRE BY ADMIXING APPROXIMATELY 40 PARTS OF COLLOIDAL GOLD WITH APPROXIMATELY 25 PARTS OF TOLUOL AND A SUITABLE AMOUNT OF GLASS FRIT, DIPPING SAID LAMP IN A TANK OF SAID METALLIC LUSTRE AND WITHDRAWING SAID LAMP AT THE RATE OF ABOUT THREE OR FOUR FEET PER MINUTE TO FORM A THIN LAYER ON THE ENVELOPE OF SAID LAMP, ALLOWING SUCH LAYER TO DRY, FIRING THE LAMP INA FURNACE AT A TEMPERATURE RANGING FROM ABOUT 650*C. TO 850*C. FOR APPROXIMATELY 15 MINUTES, COOLING THE COATED LAMP TO ATMOSPHERIC TEMPERATURE, REVERSING THE LAMP END FOR END AND DIPPING IT A SECOND TIME IN THE TANK OF METALLIC LUSTRE AND WITHDRAWING IT AT THE SAME RATE TO FORM ANOTHER THIN LAYER, DRYING, FIRING IN THE FURNACE AT THE SAME TEMPERATURE RANGE AND TIME PERIOD, COOLING TO ATMOSPHERIC TEMPERATURE AS BEFORE, AND THEREAFTER AGAIN REVERSING THE LAMP END FOR END AND DIPPING IT IN THE TANK OF METALLIC LUSTRE WITH WITHDRAWAL THEREOF AT THE RATE OF ABOUT THREE OR FOUR FEET PER MINUTE TO FORM A THIRD THIN LAYER ON THE ENVELOPE OF SAID LAMP, DRYING THE COATING, FIRING AGAIN AT A TEMPERATURE OF ABOUT 650*C. TO 850*C. FOR APPROXIMATELY 15 MINUTES, AND COOLING TO ATMOSPHERIC TEMPERATURE TO FORM A COMPOSITE LIGHT IMPERVIOUS HEAT STABLE COATING.