X-ray or gamma ray systems or devices – Source support – Shielding
Reexamination Certificate
1999-02-19
2001-07-10
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Source support
Shielding
C378S200000, C378S202000, C205S131000
Reexamination Certificate
active
06257762
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to x-ray tube casings and particularly to an x-ray tube casing coating for preventing lead contamination of oil.
The casings of x-ray tubes are lined with lead to prevent the leakage of x-rays in directions other than through the window of the tube. This lead is exposed to a dielectric cooling oil which removes heat from the tube insert during operation. X-ray exposure causes a gradual breakdown in the oil forming smaller and less saturated compounds. The lead readily oxidizes and a combination of this oxide and particles on the lead surface make coating the lead necessary to prevent oil contamination.
Currently, various epoxy type paints are used to coat tube casings and prevent leakage of the x-rays. Unfortunately, the lead which lines the casings of x-ray tubes provides a poor surface for adherence. Hence, the hot oil, x-rays and chemicals generated during the x-ray exposure of the oil all gradually promote flaking of the paint from the surface. Furthermore, the enamel and epoxy paints currently used to coat tube casings are susceptible to peeling and scratching during assembly. The particles created by the flaking, peeling and scratching cause tube instability and tube failure. In addition, the casings often require manual touch-up of the paint, and paint damaged during handling and assembly creates rework requirements as well. All of these problems impact casing quality and availability and increase the casing cost.
It is seen, then, that it would be desirable to have a more adherent, durable and long-lasting coating for x-ray tube casings which can overcome the problems of prior art tube casing coatings.
BRIEF SUMMARY OF THE INVENTION
The present invention provides for electroplating of lead sheet linings for x-ray tube casings, as a replacement for the paint coatings currently used in the art. The present invention further addresses the formation and installation of such lead sheet linings, which, if used on prior art structures, would cause peeling of a painted surface.
An adherent and durable coating is provided for a lead-lined x-ray tube casing which is exposed to dielectric cooling oil. Electroplating lead radiation shield material with a corrosion resistant and nontoxic lining material having excellent solderability, softness and ductility, provides a clean corrosion resistant surface which is inert to the oil, independent of temperature and x-ray irradiation. The electroplated lead sheet lining material preserves the lead surface from flaking and corroding to the oil. The use of electroplated lead allows for lead sheet which can be formed by blanking, drawing, rubber forming, rubber punching and hammering, without peeling of the electroplated coating. The lead sheet is electroplated on both sides, and then a surface of the electroplating layer is attached, such as by epoxy, to the aluminum casing.
Accordingly, the present invention provides a lead sheet lining which has been electroplated on both sides, for attachment to x-ray tube casings, thereby providing a more adherent and durable, and longer-lasting x-ray tube casing coating.
REFERENCES:
patent: 2164997 (1939-04-01), Machlett
patent: 3859534 (1975-01-01), Loughlin
patent: 4964148 (1990-10-01), Klostermann et al.
patent: 6062731 (2000-05-01), Guzik
Cabou Christian G.
Dunn Drew A.
General Electric Company
Haushalter Barbara Joan
Porta David P.
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