BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an end view of an x-ray source assembly according to one embodiment of the invention;
FIG. 2 is a side view, partly in cross-section, showing the x-ray source assembly of FIG. 1, as taken along the line 2-2 in FIG. 1;
FIG. 3 is also a side view, partly in cross-section, showing the x-ray source assembly of FIG. 1, as taken along the line 3-3 in FIG. 1;
FIG. 4 is an exploded perspective view of the socket member, socket base and x-ray tube arrangement according to one embodiment of the invention;
FIG. 5 is an exploded perspective view of the x-ray tube and socket base of FIG. 4 shown adjacent the cooling oil tubes which also form part of the x-ray source assembly according to one embodiment of the invention;
FIG. 6 is a partial exploded perspective view of the structure of FIG. 5, taken from an opposing end thereof; and
FIG. 7 is a much-enlarged partial view, in cross-section, illustrating an arc detector according to one embodiment of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings. It is understood that like numerals will be used to indicate like elements from FIG. to FIG.
By the term “x-ray tube” as used herein is meant an x-ray radiation emitting lamp including a glass envelope with end portions (usually opposing), one end portion having an anode structure and the other end having a cathode structure. Examples of such x-ray tubes are described in various ones of the foregoing documents.
By the term “x-ray source assembly” as used herein is meant a structure designed for housing an x-ray tube therein and for providing connections means to electrically couple the x-ray tube to a suitable power source such that the tube can function as intended, and also for cooling the x-ray tube during operation of the assembly. Examples of such assemblies are described in various ones of the foregoing documents.
By the term “socket member” as used herein is meant a socket structure designed for having an x-ray tube positioned therein such that the tube can be electrically coupled to the power source through the x-ray source assembly's connection means.
In FIG. 1, there is shown an x-ray source assembly 11 according to one embodiment of the invention. Assembly 11 includes an outer housing 13 and two power cable ports 15 and 17, the latter designed for accommodating the high voltage power cables 19 (one shown in FIG. 3) designed for providing electrical power to the assembly's x-ray tube 21 (FIGS. 2 and 3) positioned within the assembly. As seen in FIG. 3, cable 19 ends in a “banana” plug 23 and “banana” mounting plug post 25 assembly which in turn is electrically coupled to a conductor plate 27. Plate 27 is in turn electrically coupled to x-ray tube 21 by a conductor bolt 29 which threads into the end of tube 21 as shown. As further seen in FIG. 1, assembly 11 further includes a substantially annular end plate 31 secured to the outer housing 13 just below the two power cable ports 15 and 17. Assembly 11, as also shown in FIG. 1, further includes an end connector 33 which projects upwardly at an angle relative to the central axis of the assembly (when viewed from the side as in FIGS. 2 and 3). Connector 33 is designed for providing electrical coupling to various internal elements of the invention, to be defined in greater detail below. FIG. 1 also illustrates a control module 35, which is positioned atop the outer housing 13 and secured thereto. Control module 35 is also seen in FIGS. 2 and 3, adjacent lifting block 37, which is also secured to the outer housing. The lifting block functions to provide a hoisting point for installation and removal of the assembly. Finally, assembly 11 as illustrated in FIG. 1 is shown to include a mounting flange 38 and at least two locating pins 40 (see also FIGS. 2 and 3) for mounting assembly 11 within a suitable structure such as that defined in the above-identified pending application under Ser. No. 11,091,521.
X-ray tube 21 is preferably an industrial x-ray tube, and in one embodiment of the invention, is one sold by Varian Medical Systems, having a business location at 1678 S. Pioneer Road, Salt Lake City, Utah, under the product designation “V160-32G.” This is not meant to limit the invention, however, as other x-ray tubes may be successfully utilized as part of the instant invention. Briefly, an x-ray tube is a device for generating a particular kind of electromagnetic radiation. Each one is made up of a negatively charged cathode and a positively charged anode. Like a light bulb (or lamp), the cathode contains a filament. Voltage, or current, is applied to the filament, producing a stream of electrons that hurtle the short distance into the metal anode at nearly the speed of light. The collision produces x-rays. The cathode/anode assembly sits in an internal (of the glass bulb) lead-lined housing to prevent radiation from being emitted in all directions. A vacuum is created within this internal housing so that the electrons can move with the greatest possible speed from the cathode to the anode. A hole in the housing directs the x-rays out of the tube. The penetration power of the x-rays coming from a particular tube is dependent on the level of voltage it can handle. Tubes that run at 40,000 volts (40 Kv) can penetrate a small sample of material. Generating x-rays that can penetrate baggage and the human body, for example, require greater voltage levels, and, in the case of x-ray tube 21, are 160 Kv. Baggage inspection x-ray tubes can operate at higher voltages, including 250, and even 300 Kv. As mentioned above, only about a half of a percent of the total energy in an x-ray tube is converted to useable x-rays. About 99.5 percent of the energy becomes useless heat.
In the embodiment of the invention as shown in FIGS. 2 and 3, the cathode 41 is shown to the left end portion of tube 21 while the anode 43 is shown to the right end portion. As explained, the cable 19 is connected to the anode 43 (via bolt 29). The “V160-32G” x-ray tube as used in the invention includes a tungsten filament for the cathode and operates at 160 Kv maximum. It can provide up to 320 continuous watts with a forty-degree target angle and x-ray coverage of seventy-six degrees. Tube 21 includes a copper hood 45 surrounding the anode end. The tube has a length of about 7.3 inches and weighs only about 2 pounds (1 kg.). The glass includes beryllium to assure low filtration which reduces glass wall charges as well as stray radiation by intercepting secondary electrons.
According to the teachings of the invention, x-ray tube 21 is held within a socket member 51 which is comprised of polymer material (a preferred polymer being polyethylene and, more particularly, Ultra High Molecular Weight Polyethylene (UHMWPE), as defined by ASTM D4020-01, which provides a breakdown voltage of 1000 volts per mil.) which provides electrical insulation, and, because of its higher electrical strength, allows for the use of a smaller diameter lead shield (lowering the weight of the assembly in comparison to many known structures designed for having an x-ray tube positioned therein). The socket member 51 does not provide significant radiation shielding because it has a low attenuation rate for x-rays, which is deemed important in this invention. Weight reduction is a primary concern with respect to x-ray assemblies used in apparatus such as baggage inspection machines wherein several such assemblies are utilized. A lesser weight assembly is easier to load and unload, and easier to align within the inspection machine. Significantly, the polymer socket member of the invention is of two-part construction, with one part (53) designed to have the end portion of x-ray tube 21 having the anode 43 therein within said part while the other part (55) accommodates the other end portion of the x-ray tube 21 having the cathode therein. See FIGS. 2, 3 and 4. Parts 53 and 55 are positioned with an abutting orientation within a lead (Pb) shielding structure 61, which serves to substantially surround (and thereby shield) the x-ray tube and its associated socket member. Shielding structure 61 includes a tube member 61′ and end caps 63 and 65 and, as seen, is of substantially cylindrical configuration. In addition to shielding structure 61, assembly 11 further includes a metallic cylindrical member 71, which surrounds the sides of tube member 61′. Member 71 is preferably of aluminum or other sound heat conducting metal and is designed for electrical shielding and oil retention. Significantly, member 71 also provides mechanical structure for the invention because it is coupled to the lifting block 37, which in turn ties into the aluminum body.
As seen in FIGS. 4, 5 and 6, a socket base 75 is also employed and adapted for having the copper hood 45 of x-ray tube 21 positioned there-against. Base 75 is also preferably of polymer material and, more preferably, of the same material as parts 53 and 55. Base 75 fits snugly within part 53 of the socket member (see also FIGS. 2 and 3) and, significantly, defines a channel 77 (see also FIG. 2) within its rear wall so as to allow oil to pass there-through as part of the cooling of tube 21. Base 75 also has the defined conductor plate 27 secured thereto (at its back surface, using bolts 29 and 30) with upwardly extending arms 81 which align with corresponding receiving ports 83 within the base for accommodating the ends of the cylindrical tubes 91 which house the high voltage power cables 19 (not shown). As seen in FIG. 4, each of the tubes 91 passes through associated apertures 93 within part 55 of the socket member. As defined above with respect to FIG. 3, the cables 19 are electrically coupled to plate 27 (understood from FIGS. 4, 5 and 6 to be to upward arms 81) which converge at the base of the “Y”-shaped plate and allow bolt 29 to pass there-through into x-ray tube 21 to form the end connection therewith. Bolts 30 also provide connection in a similar manner. Significantly, base 75 further includes an oil passage port 101 which accommodates the cylindrical open end of an oil tube 103 (see also FIG. 2) designed for having cooling oil pass there-through whereupon the oil will pass down through channel 77, through annular oil port 104 within the base, and into a plurality of parallel oil ports 105 within copper hood 45 of the invention's x-ray tube 21. This passage of oil is partly represented in FIG. 2 by directional arrows “O.” Effective oil flow is essential to assure optimal cooling of the hot x-ray tube during its operation, as explained above. The oil is pumped through assembly 11 by an internal pump 111 (FIGS. 2 and 3) which is driven electrically. Electrical connections to the pump include internal wiring (not shown) which extends to connector 33. Pump 111 is able to pump the desired cooling oil at a rate of from about 0.5 liters per minute (LPM) to about one LPM, depending on the heat generated by tube 21. The pump 111 includes an impellor 113 which is axially rotated on a shaft (not shown), and a tachometer output from the pump is read by a circuit on the arc detector board to determine if the pump is operating properly. The internal pump-impellor assembly is able to cool the x-ray tube effectively so as to assure prolonged life thereof. In addition to the pump, assembly 11 further includes a bellows 115 (FIGS. 2 and 3) which is designed to expand or contract, depending on oil temperature. Bellows 115, in addition to providing for volumetric changes in the cooling oil, provides a sounding diaphragm that, when used in conjunction with the microphone on the arc detector board, make it possible to detect arcs within the housing but external to the tube.
One of the key features of the invention is the definition of an opening 121 (see FIG. 7) by the two parts 53 and 55 of the invention's socket member. See also FIG. 4. Understandably, it is through this defined opening that x-rays from tube 21 pass so as to function as intended (e.g., pass through luggage). FIG. 7 shows the relative positioning of the anode 43 and cathode 41 of x-ray tube 21, and how precisely opening 121 aligns with respect thereto. Relative to opening 121 (as shown), there is positioned a photo detector 131 adapted for detecting ultraviolet (UV) emissions emitted by an arc between the anode and cathode within the x-ray tube. Photo detector 131 is positioned on a printed circuit board 133 which in turn is electrically coupled to connector 33 via wiring 135 (only partly shown in FIG. 7 but understood to extend along a slot 136 (see also FIG. 4) within part 55 of the socket member adjacent shield structure 61 (the tubular portion) and then through appropriately located passages within the assembly. Such added wiring placement is considered well within the skills of one of ordinary skill in the art and further description is not deemed necessary. Positioned immediately above photo detector 131 is a UV band pass filter 137 for filtering the infrared wavelength of the tube's filament to thereby prevent overloading of the photo detector (an arc is high in UV wavelength).
In order to detect arcs within assembly 11 (but external to the tube), the invention also includes an internal microphone 141 (FIGS. 2 and 3) mounted on a second printed circuit board 143 secured to an external side of the assembly as shown, and thus within the invention's housing. The microphone (an arc detector), in conjunction with the bottom of the bellows assembly, is designed to detect arcs which pass externally of the x-ray tube and which generate a noise above one KHz. during operation of the x-ray source assembly. Detection of this sound indicates to the assembly operator that improper arcing is occurring such that the operator must then take the appropriate maintenance steps to prevent permanent damage to the tube housing. The provision of an internal microphone positioned as it is on a circuit board represents another significant aspect of this invention. Like board 133, board 143 is coupled to connector 33 through wiring (not shown) so as to receive power. The placement of such wiring, like that for arc detector 131, is within the capabilities of one skilled in the art and further description is not needed.
Thus there has been shown and described an x-ray source assembly which includes many advantageous features over known such assemblies, including, among others, the provision of a two-part lightweight socket for holding the x-ray tube in precise alignment, an internal pump for circulating cooling oil strategically through the assembly to assure optimal tube cooling, an internal microphone for detecting arcs at certain sound levels, and a photo detector positioned strategically relative to an opening defined by the socket member. In the tube housing taught herein, there are two means of arc detection. A lead shielded photo detector with a UV band pass filter is incorporated within the tube housing to detect an arc and discriminate the arc intensity. The housing also incorporates an audible arc detector, to detect an arc external to the tube but internal to the housing as a whole.
While there have been shown and described what are at present the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
Patent Application
20080043919
