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| This is U. S. Patent 4000999 |
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Centrifugally casting hollow glass body around vapor shield
A vapor shield supporting ring is attached to the envelope of a vacuum device. The supporting ring is embedded in the inner wall of the envelope and extends into the interior of such envelope. A welding flange is mounted on the interior portion of the ring. The ring does not extend to the exterior wall of the envelope. To embed the ring in the envelope, the ring is suspended by a holding means such as a magnet, which is placed into the desired position within a centrifugal mold. The molten glass is poured into the mold and the mold is spun, thereby flowing the glass along the walls and surrounding the outer portion of the supporting ring. When the glass solidifies, the supporting ring is firmly embedded in the wall of the envelope. Description BACKGROUND OF THE INVENTION This invention relates to vacuum envelopes, and more particularly, to a vapor shield supporting ring for such envelopes and to the method of installing such supporting rings. In vacuum devices, such as circuit interrupters, the metallic vapors that are produced by arcing between the contacts often condense on the insulating envelope of the device. As is well understood, these vapors tend to form a metallic coating which may cause the device to fail. To protect these devices from such metal depositions on the envelope, metal shields are often provided about the contacts such as, for example, the shield disclosed in U.S. Pat. No. 3,048,681 in the name of George Polinko, Jr., and assigned to the same assignee as this invention. Often such shields are held in place by pins or the like extending through the envelope or embedded in the glass, in the manner taught by U.S. Pat. No. 3,048,681. However, the use of such pins leads to problems in obtaining proper alignment or orientation of the pin as well as increasing the cost of manufacture of such vacuum devices. | U. S. 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