US 2458748 A
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1949- s. H. STUPAKOFF 8 HERIETIC SEAL FOR ELECTRIC TERMINALS AND THE LIKE Filed lay 1. 1945 INVENTOR Semonli Stupakoff Patented Jan. 11, 1949 HERMETIC SE AL FOR ELECTRIC TERMINALS AND THE LIKE Seinon H. Stupakoii, Latrobe, Pa., assignor to Stupakofl Ceramic & Manufacturing Company, Latrobe, Pa., a corporation of Pennsylvania Application May 1, 1945, Serial No. 591,392
This invention relates to electrical apparatus of the type wherein an electric element is sealed within a housing comprised in all or in part of metal with a terminal or connecting pin outside the housing, or to other like installations where a conductor of high frequency currents passes through a metal wall.
Typical uses for my invention are in connection with electric transformers and condensers where the electric unit is enclosed in a metal casing through which terminal or connector wires project to the exterior of the casing or housing. Glass is fused to the connector wire or terminal and also fused to a metal eyelet or the like welded or brazed to the casing, this eyelet, the glass and the terminal all having matched coefficients of thermal expansion whereby changes of tempera ture do not result in such unequal expansion of glass and metal as would cause the glass to break.
Seals made in this way are often subject to very extreme atmospheric and temperature conditions. The glass does not weather satisfactorily and this results in a continuously decreasing resistance, which is to say that as an insulator between the metal terminal and the metal casing, it
gradually deteriorates. Standard tests to accelerate these weathering conditions and determine likelihood of failure involve hot and cold salt water spray, and these seals are shown by such tests to deteriorate quite rapidly.
Moreover, the glass forming the hermetic seal has to be fused and applied in assembly of the seal, and hence cannot be, in many cases, of the most effective shape or even uniform as to shape, and shape affects insulating properties. This is especially true because of the possibility of a film of moisture or atmospheric deposit forming on the surface of the glass to provide a leakage path for current between the terminal and the casing, a desirable shape lengthenin the path and tending to reduce continuity of such a path.
With these factors in view, the present invention provides a seal in which the contour of the finished seal may be advantageously predetermined; in which substantially improved weathering properties and improved sustained insulating characteristics are provided; and in which protection may be afforded to the glass.
This, in general, is accomplished by the provision, by bonding or fusing of a second preformed insulating body to the exterior of the original glass sealing body, such preformed body thus embracing the original seal, imparting the desired advantageous contour, and preferably is 8. ma
terial diilerent from the glass.
My invention may be more fully understood by reference to the accompanying drawings, in
Fig. l is a transverse vertical section through a typical seal completed except for application of the preformed body;
Fig. 2 is a detail view showing a vertical section through a preformed body;
Fig. 3 is a view similar to Fig. i of the complete seal; and
Fig. 4 is a view similar to Fla. 1 of a modification.
Referring specifically to the drawings, and especially Fig. 1, 2 designates a metal wall or casing and 202 may be regarded as the exterior surface of this wall or casing. Welded, brazed or soldered to the exterior of the casing is an eyelet, ferrule or like support 3 of thin metal to have flexibility and selected with reference to its coefficient of thermal expansion. It may be of nickel, cobalt alloy, of the type known commercially under the trade-marl; Kovar, having its coeiilclent of thermal expansion substantially matched to borosilicate glass. The conductor or terminal l passes through a hole in the casing and through the eyelet 3 but out of contact therewith. A body of glass, as for example borosilicate glass 5 is fused to the ferrule or eyelet 3 and to the conductor 5, the conductor also having its coefllcient of thermal expansion matched to that of the glass. This forms a hermetic insulated seal for the conductor so that air or moisture cannot pass from the exterior to the interior of the casing 2.
However, the shape into which the glass t may be'formed in making the assembly is restricted.
The glass does not weather satisfactorily, and as indicated above, fails rapidly under alternate hot and cold salt spray tests.
According to the present invention there is applied over the exterior of the body of glass a previously formed secondary insulating body or opening 60:, a surrounding sleeve portion 61), a top flange 6c and a depending peripheral skirt 6d.
of seal with which it is employed.
This secondary insulator, as shown in Fig. 3, is placed on top of the glass seal 5. Then heat is applied sufficient to fuse or bond the glass to the secondary insulator 5. In some cases an applied bonding or fusing medium may be used. In fusing the collar or insulator 6 into place, pressure is applied so as to get complete contact between the collar and the glass 5.
The collar 6 may be of appropriate insulating material, including glass and preferably has its coefilcient of thermal expansion matched to that of the glass. Preferably, the collar or shield 8 is of a ceramic nature. When 5 is hard borosilicate glass (such as that known commercially as Corning I05) 8 is formed of zircon porcelain. Zircon porcelain matches the thermal expansivity of the glass; it will not be adversely affected electrically by the sealing atmosphere; it will withstand weathering and the hot and cold salt spray test, and hence the combination is superior to glass alone. It is styled to give a long and devious leakage path on the surface of the seal and has suitable electric, chemical and physical qualities.
If the glass 5 be a lead glass, the collar 6 may, for example, be of alumina or alumina compounds of a thermal expansivity matched to glass, the particular compounds and glasses being known in the art at the present time. In some cases, the applied insulator may be formed of plastic, as for example a phenolic plastic.
In the modification shown in Fig. 4, the overall contour of the seal is not altered, but the after applied insulator is inserted in a groove which extends the leakage path on the surface of the glass. In this modification i0 is the supporting eyelet, II the glass insulator, and i2 is the leadin wire or terminal. In this form, the collar it applied to the glass in a soft condition interlocks with the glass, forming an annular groove id. Also, the glass may be molded with an appropriate groove and the insulating material be applied, either as a preformed body or molded and cured in situ.
While I have shown and described one typical form of my invention and a specific embodiment it will be understood that this is illustrative, and that many variations therefrom may be made within the scope and spirit of my invention.
1. A hermetic seal construction comprising a conductor, a body of glass fused to the conductor, a sup-porting eyelet to which the glass is also fused, and a separately formed insulating collar encircling the glass and intimately bonded thereto and spaced away from the conductor.
2. A hermetic seal construction comprising a conductor, a body of glass fused to the conductor with the conductor passing through opposite points on the body, a supporting eyelet to which the glass is also fused, and a preformed insulating collar fused to the glass and intermediate the points of the glass body through which the con collar being of ceramic material and being be-.
tween the points where the conductor emerges from the glass body, and being spaced from such points.
4. A hermetic seal construction comprising a conductor, a body of glass fused to the conductor, a supporting eyelet to which the glass is also fused, and a preformed insulating collar encircling the glass and intimately bonded thereto and spaced from the conductor and eyelet, the glass being a borosilicate glass and the collar being a zircon porcelain refractory.
5. A hermetic seal construction comprising a conductor, a body of glass fused to the conductor, a supporting eyelet to which the glass is also fused, and a preformed insulating collar encircling the glass and intimately bonded thereto and spaced from the conductor and eyelet, the glass being a lead glass, the collar being formed of a ceramic material comprised principally of alumina.
6. A hermetic seal comprising a supporting member with an opening therethrough and a conductor passing axially through the opening, a body of glass fused to the supporting member and fused to and surrounding the conductor and forming a solid insulating body between the support and the conductor, and a ceramic insulating ring surrounding the glass body and intimately bonded thereto, the ceramic insulating ring being spaced from both the supporting member and the conductor and serving to interrupt the continuity of the exposed glass surface between the supporting member and the conductor.
SEMON H. STUPAKOFF.
REFERENCES CITED The following references are ofrecord in the file of this patent:
UNITED STATES PATENTS Schwartzwalder Oct. 19 1943