US 3345448 A
Description (OCR text may contain errors)
E. S. MALKIN HIGH TEMPERATURE ELECTRICAL CONNECTION Filed July 28, 1964 I NVENTOR.
EDWiN S. MALKIN 0W ATTO EV United States Patent 3,345,448 HIGH TEMPERATURE ELECTRICAL CONNECTION Edwin S. Malkin, Wilton, Conn., assignor to Union Carbide Corporation, a corporation of New York Filed July 28, 1964, Ser. No. 385,594 2. Claims. (Cl. 13-25) The instant invention relates to an improved form of electrical and mechanical connection. More specifically the invention is directed to a superior connection between a resistor element and the current leads associated therewith.
In vacuum metallizing equipment and other similar apparatus resistance heating is used to fuse and vaporize a metal, the vapors of which are then deposited upon some suitable substrate. Generally, the resistance element or vaporization vessel is connected to the power lead in equipment by metallic bolt-like clamps. Inasmuch as the vaporization is carried out at temperatures above 2300 P. such metal clamps must be water cooled to prevent melting of the clamps. Obviously, the use of water cooled equipment in such metallizing equipment is disadvantageous in that a substantial quantity of heat is no longer available for fusion and vaporization of the metal. The cooling water often removes as much as fifty percent of the heat generated by the current flowing through the system and results in a substantial loss of efiiciency. Moreover, the effect of water cooling is to produce a substantial thermal differential between the center of resistance element and the ends which are attached to the water cooled connections.
Another disadvantage of the rigid metallic bolt type connection is that such connections do not allow for differences in the coefficient of thermal expansion between the resistance element and the clamps. Such variation in the thermal expansion often causes loosening of the con nection during operation. Similarly longitudinal expansion of the resistance element causes stresses on the bolts since there is no provision for sliding motion within the clamp to compensate for such longitudinal expansion. It is therefore quite apparent that alignment of the bolt type clamps must be painstakingly controlled and frequently connected in order to prevent excessive stress and strain.
It is an object of this invention to provide an improved mechanical and electrical connection for use in vacuum metallizing apparatus. It is another object of the invention to provide a simple flexible connection which overcomes the problems caused by thermal expansion of the component parts of vacuum metallizing equipment. It is a further object to provide a suitable electrical and mechanical connection which can withstand the elevated temperatures encountered in the vacuum metallizing process and which does not require water cooling. It is a still further object to avoid the loss of heat and the resulting Waste of current, and the existence of thermal gradients in the resistance elements caused by the use of water cooled metallic clamps.
Broadly, these and other related objects are achieved by the use of a carbonaceous textile material as a supporting and electrically conducting medium between a current lead in body and a current utilizing body. The term current utilizing body as used herein is intended to encompass the various types of bodies through which an electric current passes. Such bodies include electrolytic electrodes, resistance heating elements and the like.
For example a flexible carbonaceous textile, i.e., graphite or carbon, can be used as a means of forming the connection between the current lead-in body and the resistor element or vaporization vessel. The current lead- 3,345,448 Patented Oct. 3, 1967 in body which is connected at one end to the power source is machined with a groove at the other end which groove is slightly bigger than the resistor or heating element which is to be connected thereto. The carbonaceous textile is then placed around the ends of the resistor or heating element which is to be inserted into the grooves, and wedged into the groove along with the heating element. The carbonaceous textile is sufiiciently conductive to allow the passage of electrical current through the resistor element, and is resilient enough to maintain the resistor in a relatively fixed but flexible relationship to the connecting bodies. Moreover, the carbonaceous textile is thermally stable at the elevated temperatures attained in the resistor or heating element.
In the accompanying drawing:
FIG. 1 is a perspective view of a vacuum metallizing vaporization boat and connector blocks of the type employed in aluminum vaporization equipment.
FIG. 2 is a cross section taken along the line 2-2 of FIG. 1. i
' Referring now to FIG. 1 the resistance element is constructed in the form of a graphite vaporization boat 2, which is supported at both ends by graphite connector blocks 4 and 6. Copper power leads 8, 9 are connected to the connector blocks 4 and 6 respectively and to a power supply (not shown). The vaporization boat 2 is positioned in notches having dimensions slightly greater than the vaporization boat which are cut into the connector blocks. The excess space in the notches is filled with a packing of carbonaceous cloth 10 which maintains the electrical and mechanical contact between the connector blocks and the vaporization boat. Electrical current is passed through the connector blocks and the vaporization boat causing the boat to heat up to temperatures of about 1593 C. Aluminum wire is then fed into the cavity of the vaporization boat and the aluminum melts and vaporizes. The vapors contact a substrate which passes over the vaporization boat and a deposit of aluminum is formed on the substrate.
FIG. 2 shows the piece of carbonaceous textile it] which is wedged between the outer surfaces of the vaporization boat 2 and the inner surfaces of the notch cut into connector block 6.
The resistance element can be fabricated from any of the well known conductive refractory materials which are substantially resistant to attack by molten metals. Suitable refractory materials include carbon, graphite and mixtures of boron nitride, titanium diboride and calcium fluoride.
The connector blocks are preferably constructed of a material which has melting or subliming point which is above the operating temperature of the resistance element. Materials such as carbon and graphite are well suited for use in such connector blocks. Alternatively, the connector blocks can be constructed of any of the Well known metals or alloys which are suitable for high temperature operation. However, the use of such metals make water cooling a necessity.
Carbon and graphite cloth or textiles such as are disclosed are used as the supporting and conducting medium between the resistance element and the connector blocks. The only requirements being that the carbonaceous textile be sufiiciently conductive to allow the passage of current through the apparatus and be sufficiently resilient to maintain the resistance element in floating relationship with the connector blocks.
carbonaceous filaments and processes for producing the same are known to the prior art. Such filamentary materials are the result of work ranging from the early work of Thomas A. Edison and W. R. Whitney, whose filaments were rather inflexible and did not retain the textile characteristics of the starting material, to the recently manufactured carbonaceous materials exemplified by Soltes, U.S. Patent 3,011,981 and Abbott, U.S. Patent 3,053,775 whose materials are reported to possess the typical attendant unique electrical, chemical and mechanical properties of natural carbonaceous material in the form of textile structures such as yarn and cloth which also retain the textile properties, such as drape and hand, of the starting materials. In addition, electrically conductive graphite in a flexible fiber and fabric form is reported in Metals Progress, May 1959, pp. 115 116, and in U.S. Patent 3,107,152 issued to Ford et al., and is commercially available in any textile form such as yarn, braid, felt and woven cloth and knit fabrics.
While the present invention has been particularly described in connection with vacuum metallizing equipment such carbonaceous joints are equally suitable for connecting metallic bus bars to prebaked carbon or graphite blocks in aluminum pot linings or to connect carbon and graphite heating rods to power lead-in rods in electric furnaces, or for connecting graphite anodes to graphite connector blocks in chlorine cells.
What is claimed is:
1. In a vacuum metallizing system for vapor depositing a metal on a substrate at elevated temperatures, an assembly of current carrying components comprising:
(a) a pair of current lead-in graphite connector blocks,
each of said blocks having a groove at one end thereof;
(b) a vaporization boat, one end of said boat being positioned in said groove in one of said blocks and the other end of said boat being positioned in said groove in the other of said blocks; and
(c) a mass of electrically conductive resilient carbonaceous textile wedged between said boat and said blocks in each of said grooves whereby said boat is forcefully secured to said blocks.
2. The assembly of claim 1 wherein said vaporization boat is composed of a material selected from the group consisting essentially of carbon, graphite and mixtures of boron nitride and titanium diboride and said carbonaceous textile is selected from the group consisting of carbon and graphite.
References Cited 7 UNITED STATES PATENTS 984,123 2/1911 Conley 13--22 1,681,081 8/1928 Bailey 310249 2,013,755 9/1935 Hediger 1322 3,072,558 1/1963 Myers et al 204-280 3,187,089 6/1965 Cosby et al. 17494 RICHARD M. WOOD, Primary Examiner.
V. Y. MAYEWSKY, Assistant Examiner.