X-ray or gamma ray systems or devices – Source support – Source cooling
Reexamination Certificate
2001-03-14
2001-09-11
Dunn, Drew (Department: 2882)
X-ray or gamma ray systems or devices
Source support
Source cooling
C378S141000
Reexamination Certificate
active
06286998
ABSTRACT:
BACKGROUND OF THE INVENTION
U.S. Pat. App. Ser. No. 09/244,729, filed Feb. 5, 1999, is incorporated herein by reference. The present invention relates to methods and devices for extending the life of an x-ray tube. Typically x-ray tubes are mounted inside a lead shielded radiation enclosure called a housing or casing. The housing is attachable to the x-ray machine, typically a CT, fluoroscopic, or rad machine. The housing is filled with a fluid of synthetic or petroleum derivative, generally referred to as insulating oil. The insulating oil acts to thermally and electrically insulate the tube. Heat is generally removed to air through fluid to water or fluid to water cooled air transfer.
All such fluids, are damaged, from four major contributors: (1) heat; (2) radiation; (3) high voltage arcing; and (4) corona discharge.
This heating oil is sold by two primary standards: (1) ASTM 877 for unprocessed oil; and (2) ASTM 1816 for processed oil. Insulating oil consists of perhaps 3500 separate hydrocarbons. The hydrocarbons having varying carbon bond lengths with many separate bonded molecules and ions, such as hydrogen, oxygen, hydroxyls, and many others.
For most x-ray products, the end of life is primarily predicated by an arcing process. Failure is accentuated by deposition on the glass or metal window of the insert. Deposition on the high voltage hold off leads to collapse in the insert itself, leading to subsequent deterioration of rotor function. The arcing while starting out infrequently, increases in frequency as the oil deteriorates. As the arcing increases the oil deteriorates more rapidly which, in turn, leads to more arcing.
It is commonly thought that the greases and waxes produced during the life of an x-ray tube are deleterious to the insulating oil, i.e. damaging. Such is the motivation behind U.S. Pat. No. 5,440,608 entitled “Method And System For Extending The Service Life Of An X-Ray Tube” by Peralta, et al. The method taught in Pat. '608, and subsequent patents by Peralta, U.S. Pat. Nos. 5,596,622 and 5,732,123. U.S. Pat. Nos. 5,440,608; 5,732,123; and 5,596,622 are collectively referred to herein as PERALTA. PERALTA describes methods and apparatus for removing the old oil and replacing it with new oil, and methods for filtering the greases and waxes produced during the life of an x-ray tube. As PERALTA points out, the financial risks involved in when working with x-ray tubes and CT scanners is substantial. Tubes are very delicate in some respects and require great care when repairing them.
One problem encountered in the past has been the removal of bubbles which has come out of solution, or removal of those introduced into the system when oil has been replaced. For Siemens and Phillips manufactured tubes it has been quite common for many years to remove bubbles by replacing the oil. Circa 1984, General Electric introduced quick-disconnects into the hydraulic system, i.e. quick-disconnects in-line between the heat exchanger and the x-ray tube housing. This facilitated the removal of bubbles from the system. Since approximately 1985, this inventor has had occasion to open the hoses between the heat exchanger and the x-ray tube to remove bubbles, or replace oil, or both. PERALTA describes these well known techniques.
This inventor believes the greases and waxes are not as damaging as is commonly believed. In fact, the addition of new oil, as taught by Peralta, is contrary to preferred embodiments of the present invention.
SUMMARY OF THE INVENTION
The present invention relates to methods and apparatus for extending the life of an x-ray tube, One embodiment of the invention is directed toward a maintenance method for an x-ray tube having housing and an insert located therein forbade producing x-rays. Insulating oil circulates through the housing and through a processing chamber that does not include the insert. In the processing chamber gas that is in solution with the oil is removed from the oil.
One embodiment of the invention is directed toward an x-ray machine comprising an x-ray tube mounted on a gantry. The improvement comprises positioning a processing chamber segregated from the insert to allow the oil to circulate through the chamber. To reduce pressure in the processing chamber a vacuum is connected such that gas in solution in the oil is removed from the oil.
An x-ray machine, according to an embodiment of the invention, comprises an x-ray tube mounted for operation, wherein the improvement comprises a coalescing element in fluid communication with an insert in the x-ray tube. The coalescing element removes gas in solution with the oil from the oil. This and other means for removing gas from the oil are disclosed herein. Likewise, means for removing water in solution with the oil from the oil are also disclosed. Such removal of gases, and in particular water, from the oil extend the life of the x-ray tube.
It is desirable to process the oil while the x-ray tube is mounted on the gantry to avoid the time, expense and potential risk of dismounting the x-ray tube, remounting the x-ray tube, calibrating the x-ray tube. It is also desirable because it avoids extended down time of the x-ray machine.
One object of the present invention is to provide a means for extending the life of an x-ray tube. Another object of the present invention is to reduce healthcare costs. A further object of the invention is to encourage manufacturers to develop longer lasting tubes at lower costs.
One object of the present invention is to provide a device for drying the housing of an x-ray tube. Another object of the present invention is to provide a device for removing water from the insulating oil of an x-ray tube.
Another object of the present invention is to provide a device for improving the performance of x-ray tubes.
Another object of the present invention is to provide a device for resurrecting “failed tubes.”
Another object is to teach a preventive maintenance program for extending the life of, arid improving the performance of, an x-ray tube. A further objective is to provide a device for performing the preventive maintenance program.
Another object of the present invention is to provide a device for drying insulating oil of an x-ray tube.
Another object of the present invention is to provide a device for taking gases out of a solution wherein the gases are in the insulating oil of an x-ray tube.
A further object of the present invention is to out-gas deleterious gases from the insulating oil.
Another object of the present invention is to remove damaging gases from insulating oil by providing a device which processes the oil in an environment below atmospheric pressure.
Another object is to provide a device for processing oil in a closed system.
Another object of the present invention is to provide a device which forces bubbles back into solution while in the housing, then transfers the solution to a processing chamber, then allows the bubbles to be taken out of solution and removed as a gas by an evacuation process in a processing chamber. A coalescing element is employed in some embodiments to aid removal of the gases from the oil.
Other objects and advantages of the present invention will be apparent to those of skill in the art from the teachings disclosed herein and by reference to the attached drawings.
REFERENCES:
patent: 5086449 (1992-02-01), Furbee
patent: WO95/10345 (1995-04-01), None
Dunn Drew
Hyatt John E.
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