X-ray or gamma ray systems or devices – Source support – Source cooling
Reexamination Certificate
1999-02-05
2001-07-03
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Source support
Source cooling
C378S199000, C378S130000
Reexamination Certificate
active
06254272
ABSTRACT:
BACKGROUND OF THE INVENTION
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 present invention includes a method of extending the life of an x-ray tube having a housing and an insert located therein for producing x-rays. The method comprises the steps of providing the x-ray tube with an insulating oil in the housing; and processing the insulating oil to remove deleterious gases from the oil.
In a preferred embodiment the step of processing the oil to remove deleterious gases from the oil comprises removing water from the oil. The method also includes drying the housing. In one embodiment this is accomplished by circulating insulating oil which has been dried through the housing to absorb water in the housing and drying, or withdrawing, water from the oil.
Another embodiment of the present invention includes an x-ray tube oil processor for extending the life of an x-ray tube. This is accomplished by processing the insulating oil for the x-ray tube. The x-ray tube oil processor includes a processing chamber having an oil inlet, an oil outlet, and a gas outlet. Preferably a coalescing element is positioned in the processing chamber. The coalescing element has a first end in fluid communication with the oil inlet.
Generally a vacuum source is placed in fluid communication with the gas outlet to evacuate the processing chamber. An oil inlet hose and an oil outlet hose are respectively connected in fluid communication to the oil inlet and the oil outlet of the processing chamber. Oil then enters the oil inlet hose, passes through the coalescing element which removes gases, in particular water as a vapor, from the oil, and the oil then exits the oil outlet hose.
Another embodiment of the present invention includes an x-ray tube processing kit for processing oil in an x-ray tube. The kit is important in the present invention because this allows the x-ray tube processor to be readily portable to a field location in which the x-ray tube is mounted on a gantry of an x-ray machine or CT scanner, and the like. The kit generally comprises a processing chamber containing a coalescent filter; a plurality of fluid hoses adapted to connect to the processing chamber. Preferably the kit also includes an oil pump adapter to connect to one of the plurality of fluid hoses; and a vacuum pump adapted to connect to the processing chamber.
It is desirable to process the oil while the x-ray tube is mounted in 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, and 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 i
Dunn Drew A.
Hyatt John E.
Kim Robert H.
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