Abstract:
Materials and methods of manufacturing radiation shielded enclosures is presented that may replace the use of lead, granite and other heavy, expensive, toxic, environmentally unfriendly or otherwise undesirable materials and manufacturing methods. The present invention provides a high-density radiation shielding enclosure manufactured by cold casting a liquid refined iron ore or taconite composite material into a mold of an enclosure of an appropriate shape and size to house an x-ray imaging system. The method of manufacture may include applying an iron ore or tungsten composite caulking compound to the radiation shielding enclosure in order to seal any radiation leaks in the radiation shielding enclosure.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention pertains generally to the field of radiation shielding, and more particularly to materials and methods of manufacturing radiation shielding enclosures.  
         BACKGROUND OF THE INVENTION  
         [0002]    There are numerous uses for an x-ray shielding container, such as medical x-ray machines and industrial vision inspection machines. For example, x-ray detection is used to image dense objects, such as human bones, that are located within the body. Another application of x-ray detection and imaging is in the field of non-destructive electronic device testing. For example, x-ray imaging is used to determine the quality of solder that is used to connect electronic devices and modules to printed circuit boards.  
           [0003]    X-ray imaging works by passing electromagnetic energy at wavelengths of approximately 0.1 to 100×10 −10  meters (m) through the target that is to be imaged. The x-rays are received by a receiver element, known as an x-ray detector, on which a shadow mask that corresponds to the objects within the target is impressed. Dark shadows correspond to dense regions in the target and light shadows correspond to less dense regions in the target. In this manner, dense objects, such as solder, which contains heavy metals such as lead, can be visually distinguished from less dense regions. This allows the solder joints to be inspected easily.  
           [0004]    X-ray radiation is dangerous to living beings and the environment. Therefore, x-ray equipment is typically contained within an x-ray shielding container.  
           [0005]    The shielding containers in x-ray applications have typically been built from welded steel frames with plates of lead or sheets of granite attached for shielding. Plate lead shielding is very expensive and the sheets of lead are difficult to attach to an enclosure to form a shielded enclosure. A lead enclosure typically requires steel or other exterior enclosure to protect the lead shielding from damage. Lead is also a highly toxic material, making its use in medical, industrial and commercial settings undesirable. It is also very difficult to seal holes, cracks, joints, seams and other leak points in a lead enclosure.  
           [0006]    Although granite is not a toxic material, granite-shielding enclosures suffer many of the same shortcomings as lead shielding enclosures. Granite is also very heavy and difficult to manufacture and work with. As most radiation leakage will occur around seams, joints or holes, granite must be worked with in large sheets for large medical and industrial enclosures. This makes working with and transporting a granite enclosure very difficult due to the weight of the enclosure. Moreover, granite composites typically have poor radiation shielding characteristics.  
           [0007]    Accordingly, there exists a need for an environmentally safe, low cost, radiation shielding enclosure with good radiation shielding properties. In particular, a need exists for a radiation shielding enclosure made of a shielding material other than lead or granite.  
         SUMMARY OF THE INVENTION  
         [0008]    An apparatus for enclosing and shielding x-ray imaging and inspection equipment using a taconite or iron ore composite rather than lead or granite is provided. The radiation shielding enclosure may be manufactured with a casting or injection molding process in an epoxy, polyester, or polymer substrate with or without a fiberglass or other fabric material to reinforce the form of the enclosure.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:  
         [0010]    [0010]FIG. 1 is a schematic diagram illustrating an exemplary x-ray imaging system;  
         [0011]    [0011]FIG. 2 illustrates a radiation shielding enclosure in accordance with the invention; and  
         [0012]    [0012]FIG. 3 illustrates a flow chart of a process for forming a radiation shielding enclosure in accordance with one embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    As shown in the drawings for purposes of illustration, the present invention relates to techniques for providing a radiation shielding enclosure. While described below with particular reference to an x-ray imaging system and with particular illustration of an x-ray imaging system for inspecting solder on printed circuit boards (PCB), embodiments of the invention are applicable in other x-ray systems.  
         [0014]    Turning now to the drawings, FIG. 1 illustrates an exemplary x-ray imaging system  100  in which an x-ray detector  200  resides. The x-ray imaging system  100  includes an x-ray source  102  and a plurality of x-ray detector assemblies, an exemplary one of which is illustrated using reference numeral  200 . A plurality of x-ray detectors  200  is typically supported on an x-ray detector assembly fixture (hereinafter detector fixture)  110 .  
         [0015]    The x-ray detectors  200  and the detector fixture  110  are coupled to an image-processing module  120  via connection  114 . The image-processing module  120  is coupled to a controller  125  via connection  138 . Each image-processing module  120  may receive input from one or more x-ray detectors, depending on the desired processing architecture.  
         [0016]    A controller  125  is coupled to the image-processing module  120  via connection  138 . The local interface  138  may be, for example, but not limited to, one or more buses or other wired or wireless connections, as known to those having ordinary skill in the art. The local interface  138  may have additional elements, which are omitted for simplicity, such as buffers (caches), drivers, and controllers, to enable communications.  
         [0017]    The user interface  136  may be any known or developed I/O or user interface, such as, for example, a keyboard, a mouse, a stylus or any other device for inputting information into the controller  125 .  
         [0018]    The controller  125  may be coupled to a display  118  via connection  116 . The display  118  receives the output of the controller  125  and displays the results of the x-ray analysis.  
         [0019]    In operation, the x-ray imaging system  100  can be used, for example, to analyze the quality of solder joints formed when components are soldered to a printed circuit board (PCB). For example, a PCB  104  includes a plurality of components, exemplary ones of which are illustrated using reference numerals  106  and  108 . The components  106  and  108  are generally coupled to the PCB  104  via solder joints. The x-ray imaging system  100  can be used to inspect and determine the quality of the solder joints. Although omitted for simplicity, the PCB  104  may be mounted on a movable fixture that is controlled by the controller  125  to position the PCB  104  as desired for x-ray analysis.  
         [0020]    The x-ray source  102  produces x-rays generally in the form of an x-ray radiation pattern  112 . The x-ray radiation pattern  112  passes through portions of the PCB  104  and impinges on an array of x-ray detectors  200 . As the x-rays pass through the PCB  104 , areas of high density (such as solder) appear as dark shadows on the x-ray detectors  200 , while areas of less density (such as the material from which the PCB is fabricated), appear as lighter shadows. This forms a shadow mask on each x-ray detector  200  corresponding to the density of the structure through which the x-rays have passed. Although omitted for simplicity, the controller  125  also controls the x-ray source.  
         [0021]    As will be described in further detail below, each x-ray detector  200  is constructed and located within the x-ray imaging system  100  so as to receive the x-ray energy from the x-ray source  102  after it passes through the PCB  104  or other target to be analyzed, examined, inspected or radiated, such as flesh, humans, animals, food, etc. The x-ray detector  200  converts the x-ray energy to an electrical image signal that is representative of the shadow mask that falls on the x-ray detector  200 . The electrical image signals from all of the x-ray detectors  200  are sent to the controller  125 . The image-processing module processes the signals, which can then be provided as an output to the display  118 .  
         [0022]    It will be appreciated that the present x-ray imaging system  100  is provided in high level merely for purposes of example of such a system. Other system configurations and architecture are fully anticipated, as well as other targets  104  for analyzing, examination, inspection and radiation, such as flesh, humans, animals, food, etc.  
         [0023]    Generally, it is desirable to contain the x-rays within an enclosure. This is because x-rays tend to degrade certain electronic devices and are hazardous to living creatures and the environment.  
         [0024]    [0024]FIG. 2 shows a radiation shielding enclosure  300  of an iron ore composite material with main body  304  and lid  302 . Radiation shielding enclosure  300  may have joints  310 , sealed with an iron ore composite compound and input/output holes  320 , sealed with an iron ore composite compound. FIG. 2 shows an x-ray imaging system  100 , such as an x-ray imaging printed circuit inspection system. X-ray imaging system  100  is shown merely for example purposes. Other industrial, manufacturing, and medical radiation emitting systems may be enclosed and shielded with the iron ore composite radiation shielding enclosure  300  of the present invention. During use, the iron ore composite radiation shielding enclosure  300  shields the x-rays from exposure outside of the enclosure  300 .  
         [0025]    [0025]FIG. 3 shows a flow chart for a manufacturing process according to the present invention. An enclosure mold is provided  410 . The enclosure mold may be any shape or size that is capable of functioning as an enclosure for an x-ray imaging system  100 . A liquid iron ore composite material is provided  420 . The liquid iron ore compound may contain refined iron ore, taconite, filler material and any known epoxy binder substrate. The iron ore composite material is preferably 90 percent or more iron ore. The liquid iron ore is poured or cast into the enclosure mold  430  to form the radiation shielding enclosure  300  by a cold casting process. Any radiation leaks in the radiation shielding enclosure  300  are located and filled with an iron ore composite caulking material  440 . The iron ore composite caulking material may contain iron ore filler material and any known caulking or sealant material. The iron ore composite caulking/sealant material is preferably 90 percent or more iron ore.  
         [0026]    Although this preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention, resulting in equivalent embodiments that remain within the scope of the appended claims. For example, the iron ore composite material or caulking compound may also contain tungsten or other dense metals.