US3263015A

US3263015A - Heating elements for high vacuum furnaces

Info

Publication number: US3263015A
Application number: US322205A
Authority: US
Inventors: Charles A S Hill
Original assignee: Abar Corp
Current assignee: ABAR IPSEN INDUSTRIES A NY LP
Priority date: 1963-11-07
Filing date: 1963-11-07
Publication date: 1966-07-26
Anticipated expiration: 1983-07-26

Description

July 26, 1966 c. A. s. HILL HEATING ELEMENTS FOR HIGH VACUUM FURNACES Filed Nov. 7, 1963 INVENTOR. C'II'ARLAFS- A61 H/LL BY @TQW ATTORNEY United States Patent 3,263,015 HEATING ELEMENTS FOR HIGH VACUUM FURNACES Charles A. S. Hill, Southampton, Pa., assignor, by mesne assignments, to Abar Corporation, Willow Grove, Pa., a corporation of Pennsylvania (1964) Filed Nov. 7, 1963, Ser. No. 322,205 8 Claims. (Cl. 1325) This invention relates to resistance heating elements for high vacuum furnaces.

The necessity for heating and melting high temperature refractory metals, and specifically zirconium, columbium, tantalum, molybdenum, tungsten, titanium, rhenium, and alloys thereof, which require heating in a vacuum not only for degassing the metal but to prevent undesired reaction, requires the use of vacuum furnaces.

'Serious temperature limitations have been imposed by actual operating conditions on most of the heating elements heretofore available.

In my prior application Serial No. 202,616, filed June 14, 1962, now Patent No. 3,155,758, there is shown animproved heating element with which higher furnace operating temperatures are made available than heretofore. The heating element there shown has limitations, particularly in that it is not as well suited as is desired for electrode materials which are difiicult to weld.

The heating element of the present invention has added advantages over those heretofore available.

It is the principal object of the present invention to provide a resistance heating element for vacuum furnaces which is of simple construction and which will permit attaining higher temperatures than heretofore, which will have a longer useful life and which will be free from other difiiculties heretofore encountered in this field.

It is a further object of the present invention to provide a resistance heating element for vacuum furnaces, which accommodates the elevated temperatures with negligible distortion, which has an improved uniform current input distribution for energization, and which has other improved qualities in use.

It is a further object of the present invention to provide aresistance heating element for vacuum furnaces which is simple in construction, sturdy, and free from difiiculties in use. I i It is a further object of the present invention to provide a resistance heating element for vacuum furnaces which permits the use, in an effective manner, of materials which are difiicult to weld.

It is a further object of the present invention to provide an improved heating element for vacuum furnaces which is freely suspended so as to permit rapid replacement or interchange of heating elements.

It is'a further object of the present invention to provide resistance heating elements for vacuum furnaces which can be readily interchanged so as to substitute one kind of resistance material for another thereby increasing the versatility of the furnace.

It is a further object of the present invention to provide an improved heating element for vacuum furnaces which permits of the use of a wide range of thickness of heating element, including very thin elements, with reduction of power cost and cost of furnace components.

It is a further objectof the present invention to provide an improved mounting for heating elements of vacuum furnaces which is exceedingly simple and avoids the necessity for welding or fusion joining of margins of the element.

It is a further object of the present invention to provide an improved heating element for vacuum furnaces in which the length of the element can be selected to match the power supply with elements of different resistivity.

It is a further object of the present invention to provide a resistance heating element for vacuum furnaces which is supported in a manner which decreases the likelihood of failure.

It is a further object of the present invention to provide a resistance heating element for vacuum furnaces which is supported in a pendant relation in an improved manner.

It is a further object of the present invention to provide a resistance heating element for vacuum furnaces which can be used in furnaces for tension testing at high temperatures and for other purposes.

Other objects and advantageous features of the invention will be apparent from the description and claims.

The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawings forming part thereof, in which:

FIGURE 1 is a view in perspective of a portion of a vacuum furnace having the heating element of the invention mounted therein;

FIG. 2 is a horizontal sectional mately on the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary perspective view of the heating element partially assembled;

FIG. 4 is an enlarged fragmentary sectional view taken approximately on the line 44 of FIG. 3; and FIG. 5 is a fragmentary perspective view of a modified form a free suspended heating element in accordance with the invention.

It should, of course, be understood that the description and drawings herein are illustrative-merely and that various modifications and changes can be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

Referring now more particularly to FIGS. 1 to 4 of view taken approxithe drawings, the furnace and its vacuum equipment have,

been omitted and only the heating element and its associated structure are illustrated. As there shown, an outer water cooled heat sink is provided which comprises opposite pairs of vertical

metallic side walls

10, 11, 12 and 13, preferably in connected contiguous pairs for outward swinging so that access can be had to the interior. The

walls

10, 11, 12 and 13 can be supported in any desired outer furnace enclosure (not shown) and preferably have liquid cooling pipes 14 mounted thereon with cooling liquid supply and delivery pipes 15 and 16.

Within the interior of the pairs of

walls

10, 11, 12 and 13, spaced metallic shields 17 can be provided having notches 18 at their upper margins aligned with corresponding notches 19 in the

side walls

10, 11, 12 and 13

Electrodes

20, 21, 22 and 23 are provided, are supported in any desired manner, are preferably liquid cooled, and have sockets 24 for the reception of hori zont-al heating elementmounting rods 25. The mounting rods 25 are of L-shape with holding arm portions 26 and inner element supporting arm portions 27. The holding arm portions 26 of the rods 25 can be clamped attheir outer ends in the

electrodes

20, 21, 22 and 23, respectively, and held in any desired manner, such as by set screws 28. The holding arm portions 26 extend inwardly through the

notches

19 and 18, and the arm portions 27, preferably disposed in the same horizontal plane with the portions 26 and with each other, have the heating elements 30 freely pendant therefrom.

The rods 25 can be of any desired electric conductive material capable of functioning at the elevated temperatures in the furnace, and can be of the same metal as the heating elements 30 or of different metals.

The heating elements 30 can be of nickel, molybdenum, columbium, tantalum, tungsten, tantalum-tungsten alloys such as 90% tantalum and tungsten, tungsten-rhenium alloys, rhenium, osmium, iridium, or alloys including binary or ternary alloys of these metals, it is also intended for some purposes to employ conductive nonmetals, so long as these have the desired temperature resistant qualities in use and the desired resistivity.

The heating elements 30 are preferably of material in sheet form, and of the desired thickness in accordance with the heating qualities desired. For example, sheet metal of thickness down to about one half a thousandth of an inch may be employed.

The use of relatively thin sheet material permits of using less power for heating as well as lesser qualities of high cost per pound material for the heating elements.

The heating elements 30 are supported by the arm portions 27 and in pendant relation thereto and at their upper ends, as shown in detail in FIG. 4, can have elongated cylindrical sections 31 with seams 32 therealong, such as are employed on sheet metal containers, to retain the cylindrical sections 31 at elevated temperatures.

The heating elements 30, at the bottoms thereof, can have similar cylindrical sections 33 for the reception of L-shaped horizontally disposed connector rods 34 of any suitable material, and preferably the same as that employed for the rods 25.

In the form of the invention shown in FIG. 5, the heating elements 30:: are shown as sleeves, pendant from the rod portions 27, and with the connector rods 34 supported thereby as before.

In use, the

electrodes

20 and 21 can be connected in one phase of the source of electric energy and the

electrodes

22 and 23 can be connected to the same phase or to another phase.

The electric energy supplied through the pairs of

electrodes

20, 21, 22, and 23, and through the rods 25, and by the connection through the rods 34 is effective for resistance heating of the

heating elements

30 or 30a the heating action being available in the space enclosed by the

elements

30 or 30a.

As the heating of the

heating elements

30 or 30a occurs, with expansion due to temperature increase, the

heating elements

30 or 30a are relatively free from restraint, horizontally considered, and likewise are free from vertical restraint.

The manner of suspension of the

heating elements

30 and 30a on the rods 25 and with the lower connector rods 34 loosely mounted therein permits of quick interchange of heating elements so that a heating element of one composition can be substituted for that of another composition, or cross section, with the substituted element, if of different resistivity, of a length to match the power supply, if desired.

Operating temperatures up to 3000 C. can be accomplished by selection of suitable length of the heating element. The direct heat transfer from the

heating elements

30 and 30a to the rods 25 is reduced because of the small cross sectional area of the rods 25 for heat transfer.

The construction of heating elements heretofore de scribed have a uniformity of current distribution with improved resistance heating action. Further, by reason of the uniformity of heating, they have a substantially uniform temperature profile. Freedom from distortion both upon heating and cooling is accordingly attained.

I claim:

1. A resistance heating device for vacuum furnaces comprising electrodes,

a matched pair of upper horizontal supporting rods respectively connected to said electrodes,

a matched pair of resistance heating elements in sheet form extending downwardly from said upper supporting rods,

a common lower horizontal connecting rod engaging the lower ends of said pair of elements,

said elements each having a curved upper end portion and a curved lower end portion extending re spectively around the upper and lower rods.

2. A resistance heating device as defined in claim 1 in which said heating elements are freely slidable along said upper rods for insertion and removal thereof.

3. A resistance heating device as defined in claim 2 in which said lower connecting rod is freely slidable along the lower ends of said elements.

4. A resistance heating device as defined in claim 1 in which said curved end portion is a cylindrical sleeve.

5. A resistance heating device as defined in claim 1 in which the heating elements are each sleeve shaped.

6. A resistance heating device as defined in claim 1 in which said upper and lower end portions are cylindrical, and

said heating elements each has a central section of a single thickness of material with seams at the top and bottom thereof connecting said central section with said upper and lower end portions.

7. A resistance heating device for vacuum furnaces comprising a plurality of electrodes,

a plurality of matched pairs of upper horizontal supporting rods respectively connected to said electrodes,

matched pairs of resistance heating elements for each of said pairs of supporting rods,

said heating elements being in sheet form and extending downwardly from said upper supporting rods,

said heating elements each having a curved upper and a curved lower end portion and said upper end portions being in slidable engagement with said supporting rod,

a common lower horizontal connecting rod of L-shape for each matched pair of heating elements engaging the lower ends of said pair of elements,

said connecting rods being in slidable engagement with said lower ends.

8. A resistance heating device as defined in claim 7 in which said heating elements each has a central section of a single thickness of material with seams at the top and bottom thereof connecting said central section with said upper and lower end portions.

References Cited by the Examiner UNITED STATES PATENTS 1,401,303 12/1921 Baldwin 219-538 1,819,554 8/1931 Hanson 3-25 2,264,716 12/1941 Roth 3-25 X 2,749,424 6/ 1956 Dieterich 325 X 2,966,537 12/1960 Witucki et al. 325 X 3,057,936 10/1962 Hill 3-25 3,155,758 11/1964 Hill 325 3,178,665 4/1965 Matheson et al 3-25 RICHARD M. WOOD, Primary Examiner. ANTHONY BARTIS, Examiner.

V. Y. MAYEWSKY, Assistant Examiner.

Claims

1. A RESISTANCE HEATING DEVICE FOR VACUUM FURNACES COMPRISING ELECTRODES, A MATCHED PAIR OF UPPER HORIZONTAL SUPPORTING RODS RESPECTIVELY CONNECTED TO SAID ELECTRODES, A MATCHED PAIR OF RESISTANCE HEATING ELEMENTS IN SHEET FORM EXTENDING DOWNWARDLY FROM SAID UPPER SUPPORT RODS, A COMMON LOWER HORIZONTAL CONNECTING ROD ENGAGING THE LOWER ENDS OF SAID PAIR OF ELEMENTS,