US2557530A - Electric heating element - Google Patents

Electric heating element Download PDF

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Publication number
US2557530A
US2557530A US695421A US69542146A US2557530A US 2557530 A US2557530 A US 2557530A US 695421 A US695421 A US 695421A US 69542146 A US69542146 A US 69542146A US 2557530 A US2557530 A US 2557530A
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Prior art keywords
filament
cavity
zone
coating
resistance
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US695421A
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George H Bancroft
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Eastman Kodak Co
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Eastman Kodak Co
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24Vacuum evaporation
    • C23C14/26Vacuum evaporation by resistance or inductive heating of the source

Description

June 1951 Y v G. H. BANCROFT 4 2,557,530

ELECTRIC HEATING ELEMENT F led Sept. 7, 1946 INVENTOR.

BY M64 CLMw-V Aime/sax Patented June 19, 1951 ELECTRIC HEATING ELEMENT George H. Bancroft, Rochester, N. Y., assignor, by mesne assignments, to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application September 7, 1946, Serial No. 695,421

1 2 Claims.

This invention relates to an improved filament for use in a coating machine which operates by the vaporization and condensation of substances in a low pressure chamber and more particularly to an improved filament for evaporating aluminum in a lens coating machine.

The prior art includes many inventions dealing with vacuum coating apparatus. For example, Patents 2,401,433 and 2,384,576 disclose apparatus for the production of mirrored surfaces in which a wire filament is used. In Patent 2,387,970, vacuum coating apparatus is described in which the filament is the metal to be evaporated in a refractory vessel. Vacuum coating apparatus of this type comprises an evacuable chamber, means for evacuating the chamber, holding means for the articles to be coated, filament means for holding and vaporizing coating material, and means for energizing the filament means.

The usual types of filament used in vacuum coating machines have consisted of a thin coating of the metal to be evaporated on a short length of wire of tungsten Or some other highmelting material in the form of a helix or conical spiral. These filaments are resistance heated by the passage of a suitable electric current.

If the coating substance is a nonconductor a small quantity of it may be placed in the center of a spiral of tungsten wire and resistance heated. Another type of filament may be formed of thin sheets of tungsten in the shape of boats or receptacles which are filled with metal to be evaporated and heated by electrical resistance. A further type of filament consists of a non-conducting material, for example, alumina, in the shape of a boat in which metal may be placed for resistance heating. In this arrangement conducting wires must make contact with the melt. Disadvantages of these various filaments are the limited capacity of a coated tungsten wire and the short life of the receptacle in the case of both tungsten and nonconducting materials due to alloying or combination of the material being evaporated with the receptacle.

The object of this invention is to provide a filament which will have a long life. Another object is to provide a filament of large capacity. A further object is to provide a filament composed of material which will not readily react with material being evaporated. Still another object is to furnish a filament which will act as a conductor in the resistance heating of nonconducting materials. Another object is to improve the state of the art. Other objects will appear hereinafter.

These and other objects are accomplished by my invention which includes an elongated carbon filament with a. center section of small crosssectional area containing a cavity in which material to be evaporated may be placed for resistance heating.

In the following description I have set forth several of the preferred embodiments of my invention but it is understood that these are given by way of illustration and not in limitation thereof.

In the accompanying drawing I have set forth a preferred form of my invention. Figure 1 is a top view of the carbon filament which may be constructed of a cylindrical carbon rod. Figure 2 is a front view of the filament. Figure 3 is: a cross-section taken at plane 3-4.

Numerals 2, 2 designate the end sections of the carbon filament. Numeral 3 designates the center section of the filament which may be given a narrower cross-section by tapering or which may be cut down abruptly to the narrower cross-section. Numeral 4 designates the cavity in center section 3 in which the substance to be evaporated may be placed.

In operation the carbon filament is placed between electrical terminals within a vacuum chamber (not shown) and the cavity filled with aluminum or other substance to be vaporized. After the vacuum chamber has been evacuated an electric current is run through the filament. The resistance at the center section is greater due to the narrower cross-sectional area and this section heats up to a higher temperature than .do the end sections. The temperature may be controlled by varying the current flowing through the filament.

To maintain the end sections cool, the electrical resistance of the center section including the charge must be greater than the resistance of the end sections. A cross-sectional area of section 3 must be considerably less than the cross-sectional area of the end sections in order to effect this, but the exact dimensions will vary with the substance to be vaporized. If a nonconductor is being vaporized the cavity and center cross-sectional area may both be comparatively large since the resistance of the carbon alone is the source of heat. If a metal, such as aluminum, is vaporized both the cavity and center cross-sectional area must be comparatively small as the aluminum ofiers less resistance to current flow than does the carbon .of the cavity wall. If the cavity is too large the end sections will heat more than the center sectiom.

By the use of my invention it is possible to evaporate as much as times the load of material using a coated tungsten filament. Carbon has very little tendency to alloy and a carbon filament lasts over 12 times as long as a tungsten filament of the cavity type.

What I claim is:

1. A filament for vacuum coating apparatus, said filament comprising a unitary elongated member formed of carbonaceous resistance material and comprising spaced apart terminal zones and an intermediate vaporizing zone therebetween, said intermediate zone having an unlined cavity therein arranged to receive vaporizabie solid coatin material, said intermediate zone throughout its extent having a relatively small cross-section as compared to said terminal zones and said cavity having a relatively small crosssection as compared to said intermediate zone, the combined cross-sectional area of said intermediate zone and said cavity being substantially less than the cross-sectional area of each said terminal zone, the cross-sectional dimensions of said zones and of said cavity being so correlated that the electrical resistance of the carbonaceous material of said intermediate zone is substantially higher than of said terminal zones when said cavity contains relatively low resistance electrically conductive coating material, whereby said terminal zones remain substantially cooler than said intermediate zone when said intermediate zone'is heated, by passage of current through said filament, to a temperature sufiiciently high to evaporate said coating material.

2. Coating apparatus comprisin a vacuum chamber arranged to receive a succession of objects to be coated with volatilizable solid coating material, an electrically heated unitary filament arranged within said chamber for volatilizing said material, and terminal means for supplying electric current to said filament, said filament consisting essentially of carbon and having a generally elongated configuration, said filament being formed with spacedapart terminal zones of relatively large cross-section for respective connection with said terminal means and also having an intermediate vaporizing zone connecting 4 said terminal zones and having throughout the extent of said intermediate zone a substantially narrower cross-section than said terminal zones, said intermediate zone having therein an unlined cavity arranged to receive said volatilizable solid coating material for evaporation therefrom onto said objects, the combined cross-sectional area of said intermediate zone and said cavity being less than the cross-sectional areas of said terminal zones and the cross-sectional area of said cavity being relatively small as compared to the cross sectional area of the carbon in said intermediate zone and all said cross-sectional areas being correlated so that the electrical resistance of said intermediate zone is substantially greater than the resistance of said terminal zones when said cavity contains either electrically conductive material or electrically nonconductive material, whereby said terminal zones remain substantially cooler than said intermediate zone when said intermediate zone is heated, by passage of current through said filament,to a temperature adequate to vaporize said coating material.

GEORGE H. BANCROFT.

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

UNITED STATES PATENTS Number Name Date 923,425 Gin et al June 1, 1909 1,279,146 Peacock Sept. 17, 1918 1,291,106 Payne Jan. 14, 1919 1,323,576 Bristol et al Dec. 2, 1919 1,839,518 Woods et al Jan. 5, 1932 2,013,755 Hediger Sept. 10, 1935 2,100,045 Alexander Nov. 23, 1937 2,430,994 Reynolds Nov. 18, 1947 40 2,433,922 Osterberg Jan. 6, 1948 FOREIGN PATENTS Number Country Date 5,508 France May 2, 1906 411,417 France June 16, 1910 83,973 Switzerland June 8, 1918 Certificate of Correction Patent No. 2,557,530 June 19, 1951 GEORGE H. BANCROFT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 9, for the patent number 2,401,433 read 2,401,443;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of August, A. D. 1951.

THOMAS F. MURPHY,

Assistant Gammz'ssioner of Patents.

Certificate of Correction Patent N 0. 2,557,530 June 19, 1951 GEORGE H. BANGROFT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 9, for the patent number 2,401,433 read 2,401,443;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 28th day of August, A, D. 1951.

THOMAS F. MURPHY,

Assistant C'ommz'ssz'oner of Patents.

US695421A 1946-09-07 1946-09-07 Electric heating element Expired - Lifetime US2557530A (en)

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615060A (en) * 1951-08-14 1952-10-21 Gen Electric Crucible for the purification of molten substances
US2665229A (en) * 1951-11-05 1954-01-05 Nat Res Corp Method of coating by vapor deposition
US2664853A (en) * 1952-05-12 1954-01-05 Nat Res Corp Apparatus for vapor coating
US2693521A (en) * 1951-12-26 1954-11-02 Alexander Vacuum Res Inc Heater for vacuum metalizing apparatus
US2703334A (en) * 1950-06-30 1955-03-01 Nat Res Corp Coating
US2717915A (en) * 1952-11-13 1955-09-13 Zalman M Shapiro Apparatus for production of purified metals
US2756166A (en) * 1951-01-27 1956-07-24 Continental Can Co Vacuum metallizing and apparatus therefor
US2903544A (en) * 1956-04-18 1959-09-08 Heraeus Gmbh W C Coating
US2962538A (en) * 1958-01-30 1960-11-29 Continental Can Co Vaporizing heater for vacuum deposition and method of employing the same
US2996412A (en) * 1958-10-10 1961-08-15 Continental Can Co Art of depositing metals
US3150225A (en) * 1961-10-26 1964-09-22 Owens Corning Fiberglass Corp Apparatus for melting heatsoftenable materials
US3155759A (en) * 1962-07-03 1964-11-03 Leslie H Marshall High temperature furnace
US3582611A (en) * 1969-11-24 1971-06-01 Sylvania Electric Prod Apparatus and method of metal evaporation including an evaporation boat having lower electrical resistivity ends than the center thereof
US3657515A (en) * 1970-08-21 1972-04-18 Westinghouse Electric Corp Diving suit
US4247735A (en) * 1978-02-16 1981-01-27 Rigatti Luchini Luchino Electric heating crucible
US6349108B1 (en) 2001-03-08 2002-02-19 Pv/T, Inc. High temperature vacuum furnace
ITMI20131171A1 (en) * 2013-07-11 2015-01-12 Getters Spa Improved dispenser of metal vapors

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US923425A (en) * 1907-03-22 1909-06-01 Gustave Gin Device for singeing threads.
FR411417A (en) * 1909-06-14 1910-06-16 Oerlikon Maschf Electric furnace for heating or quenching metals, with indirect heating of the bath of molten metal salts
US1279146A (en) * 1918-03-01 1918-09-17 Haslup & Peacock Inc Electric furnace.
US1291106A (en) * 1917-11-21 1919-01-14 Gen Electric Electrical resistance.
US1323576A (en) * 1919-12-02 Electric furnace
CH83973A (en) * 1919-05-23 1920-02-16 Morgan Crucible Company Limite Electrically heated melting crucible
US1839518A (en) * 1929-11-07 1932-01-05 Hughes Tool Co Method of forming tungsten carbide
US2013755A (en) * 1934-05-07 1935-09-10 Globar Corp Electric furnace
US2100045A (en) * 1935-10-12 1937-11-23 Alexander Paul Deposition of metallic films from metal vaporized in vacuo
US2430994A (en) * 1944-07-29 1947-11-18 Rca Corp Method of coating lenses
US2433922A (en) * 1942-10-15 1948-01-06 American Optical Corp Apparatus for treating surfaces

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1323576A (en) * 1919-12-02 Electric furnace
US923425A (en) * 1907-03-22 1909-06-01 Gustave Gin Device for singeing threads.
FR411417A (en) * 1909-06-14 1910-06-16 Oerlikon Maschf Electric furnace for heating or quenching metals, with indirect heating of the bath of molten metal salts
US1291106A (en) * 1917-11-21 1919-01-14 Gen Electric Electrical resistance.
US1279146A (en) * 1918-03-01 1918-09-17 Haslup & Peacock Inc Electric furnace.
CH83973A (en) * 1919-05-23 1920-02-16 Morgan Crucible Company Limite Electrically heated melting crucible
US1839518A (en) * 1929-11-07 1932-01-05 Hughes Tool Co Method of forming tungsten carbide
US2013755A (en) * 1934-05-07 1935-09-10 Globar Corp Electric furnace
US2100045A (en) * 1935-10-12 1937-11-23 Alexander Paul Deposition of metallic films from metal vaporized in vacuo
US2433922A (en) * 1942-10-15 1948-01-06 American Optical Corp Apparatus for treating surfaces
US2430994A (en) * 1944-07-29 1947-11-18 Rca Corp Method of coating lenses

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2703334A (en) * 1950-06-30 1955-03-01 Nat Res Corp Coating
US2756166A (en) * 1951-01-27 1956-07-24 Continental Can Co Vacuum metallizing and apparatus therefor
US2615060A (en) * 1951-08-14 1952-10-21 Gen Electric Crucible for the purification of molten substances
US2665229A (en) * 1951-11-05 1954-01-05 Nat Res Corp Method of coating by vapor deposition
US2693521A (en) * 1951-12-26 1954-11-02 Alexander Vacuum Res Inc Heater for vacuum metalizing apparatus
US2664853A (en) * 1952-05-12 1954-01-05 Nat Res Corp Apparatus for vapor coating
US2717915A (en) * 1952-11-13 1955-09-13 Zalman M Shapiro Apparatus for production of purified metals
US2903544A (en) * 1956-04-18 1959-09-08 Heraeus Gmbh W C Coating
US2962538A (en) * 1958-01-30 1960-11-29 Continental Can Co Vaporizing heater for vacuum deposition and method of employing the same
US2996412A (en) * 1958-10-10 1961-08-15 Continental Can Co Art of depositing metals
US3150225A (en) * 1961-10-26 1964-09-22 Owens Corning Fiberglass Corp Apparatus for melting heatsoftenable materials
US3155759A (en) * 1962-07-03 1964-11-03 Leslie H Marshall High temperature furnace
US3582611A (en) * 1969-11-24 1971-06-01 Sylvania Electric Prod Apparatus and method of metal evaporation including an evaporation boat having lower electrical resistivity ends than the center thereof
US3657515A (en) * 1970-08-21 1972-04-18 Westinghouse Electric Corp Diving suit
US4247735A (en) * 1978-02-16 1981-01-27 Rigatti Luchini Luchino Electric heating crucible
US6349108B1 (en) 2001-03-08 2002-02-19 Pv/T, Inc. High temperature vacuum furnace
US6529544B2 (en) 2001-03-08 2003-03-04 Lennie L. Ashburn Vacuum heat treating furnace
US6947467B2 (en) 2001-03-08 2005-09-20 Pv/T, Inc. Cooling system for heat treating furnace
ITMI20131171A1 (en) * 2013-07-11 2015-01-12 Getters Spa Improved dispenser of metal vapors
WO2015004574A1 (en) * 2013-07-11 2015-01-15 Saes Getters S.P.A. Improved metal vapour dispenser

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