Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2000-05-23
2001-10-09
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C439S589000
Reexamination Certificate
active
06300572
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sealed conductor, and more particularly to a plastic and ceramic encased electrical conductor for use in high temperature and high pressure environments for electrical isolation of instrument packages. Instrument packages commonly used in the petrochemical industry and military application require electrical feedthroughs which survive extreme environments and maintain electrical isolation while holding extremely high pressures. The instrument packages must meet the most severe requirements for electrical and mechanical integrity at temperatures over 500° F. and pressures exceeding 30,000 PSI. The electronics inside the instrument package must be protected from the harsh outside environment while maintaining electrical connections passing through that environment. The connection is typically made through one or more electrical conductors extending through the wall or bulkhead of the instrument package.
A common method of constructing high-pressure electrical connectors is the glass-sealing method. In the glass-sealing method, the conductor is positioned in a cavity formed in the bulkhead and glass is melted in the cavity forming a plug around the conductor. Materials are chosen to match thermal characteristics of the bulkhead, glass and conductor. Complex heat treatments are necessary to leave the desired residual stresses and some adhesion between the bulkhead, glass and conductor. The geometry of the seal is typically unsatisfactory as the sole insulator for the instrument packaging. Plastic and ceramic insulators are typically added and bonded in place with adhesive. The glass seals method requires a large compromise in material selection, has a limited tolerance to thermal shock and cycling and is very difficult to manufacture with multiple seals in complex geometries.
More recent efforts in designing high temperature and pressure instrument housings have replaced the metal body, glass and secondary insulators in small connector designs with a single piece of molded plastic. The plastic connector is a direct replacement for the older glass/metal connector. For small designs, the all plastic product has met with some success. However, these molded plastic connectors have a limited service life at higher temperatures. Current designs simply use plastic contact blocks as insulators or/and to hold elastomeric seals, as for example the hermetic connector described in U.S. Pat. No. 5,203,723.
Molded plastic connectors are well known. The applications for automotive and general industrial electrical hardware, a great deal of which are all plastic connectors, do not approach the tolerance for adversity and the level of integrity needed for the oil field and military applications or other extreme environment applications. To meet these more stringent requirements, glass seals with ceramic insulators are offered. Glass seals and plastic insulators are offered. Metal-braze seals are offered with ceramic or ceramic and plastic insulators. No one offers a plastic or plastic/ceramic compression seal.
SUMMARY OF THE INVENTION
The electrical connector of the present invention is encased in high temperature plastic and ceramic tubing. One or more holes are machined through the bulkhead of the instrument housing through which the conductor(s) is passed. The geometry of the conductor and ceramic insulators is such that a mechanical interaction between them occurs which introduces a large tensile force in the conductor and a large compressive force in the tubular ceramic and plastic insulators. This produces and maintains a sufficiently high compressive loading in the plastic insulator against the inside surface of the bulkhead so as to form a hermetic seal. Thermal or other mechanical bonding and loading mechanisms could be applied. Impedance limited coaxial configurations are possible with the addition of a sleeve and a second set of insulators.
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Mayo III William H.
Reichard Dean A.
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