Abstract:
A nonintrusive inspection apparatus is described of the kind having a base frame, an elongated shield on the base frame, a conveyor belt passing through the shield which is used for transporting closed containers, and a rotating CT scanner subsystem which is used for scanning the container on the conveyor belt. The CT scanner subsystem is mounted through the shield to the base frame. The shield provides sufficient rigidity for the CT scanner subsystem. A cover is positioned over the CT scanner subsystem, but only over a portion of the shield, thereby allowing for a person on one side of the shield to see a person on an opposite side of the shield.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/300,472, filed Nov. 19, 2002 now U.S. Pat. No. 6,859,518, entitled. “An X-Ray Technique-Based Nonintrusive Inspection Apparatus”. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Certain aspects of this invention were developed with support from the FAA (Federal Aviation Association). The U.S. Government may have rights in certain of these inventions. 

   BACKGROUND OF THE INVENTION 
   1). Field of the Invention 
   This invention relates to an x-ray technique-based nonintrusive inspection apparatus, particularly of the kind that may be used for nonintrusively inspecting closed containers before being loaded into a loading bay of an aircraft. 
   2). Discussion of Related Art 
   Inspection apparatus are commonly used for nonintrusively inspecting luggage and other closed containers before being loaded into a loading bay of an aircraft. Older generation inspection apparatus relied merely on conventional x-ray technology for nonintrusively inspecting closed containers. More recently, inspection apparatus which rely on computer tomography (CT) scanning technology have also been utilized. An inspection apparatus utilizing CT scanning technology is described in U.S. Pat. Nos. 5,182,764 and 5,367,552 by Peschmann, et al., which are assigned to the assignee of the present case and which are hereby incorporated by reference. 
   An inspection apparatus of the aforementioned kind usually has a relatively strong support structure that allows for a CT gantry to be accelerated and decelerated without much distortion in the support structure. The support structure is usually complex and expensive to manufacture. Such an apparatus is also usually intimidating, because it is large and obstructs view and communication between persons standing on opposite sides of such an apparatus. 
   SUMMARY OF THE INVENTION 
   The invention provides a nonintrusive inspection apparatus, comprising a base frame, a first shield, a first bearing race, a second bearing race, a gantry, and an x-ray source. The first shield defines a tunnel having a width through which an object can pass. The shield has a length that is at least equal to the width of the tunnel, and is mounted along its length to the base frame. The first bearing race is circumferentially mounted to the shield and through the shield to the base frame. The second bearing race is mounted to the first bearing race for rotation relative to the first bearing race. The gantry is mounted to the second bearing race. The x-ray source is mounted to the gantry. 
   The system preferably includes a conveyor system, having first and second spaced rollers and a conveyor belt over the rollers, the conveyor belt extending at least partially through the first shield. 
   The system may also include a channeling structure within the first shield and positioned so that containers entering the first shield on the conveyor belt are moved away from the first shield. 
   The system may further include a second shield mounted to the base frame on a side of the gantry opposing the first shield, the container moving sequentially through the first shield, the gantry, and the second shield. 
   The system may further include a cover over at least the gantry and the x-ray source. 
   The cover may be located over only a portion of the first and second shields. 
   The cover may include at least one panel which is movable to expose the gantry. 
   The system may further include a liner on an inner surface of the first shield, of a material different than the first shield, that substantially attenuates x-ray radiation. 
   The first shield may be made of steel, and the liner may be made of lead. 
   The first shield may be a circular pipe. 
   The system may further include a plurality of circular roller members in a space between the first and second bearing races. 
   According to a further aspect of the invention, a nonintrusive inspection apparatus is provided, comprising a base frame, an elongated first shield, a gantry, an x-ray source, and a cover. The elongated first shield is mounted to the base frame and defines a tunnel through which a container can pass. The gantry is rotatably mounted to the base frame. An x-ray source is mounted to the gantry. The cover is located over the x-ray source, the gantry, and a portion only of the first shield. 
   The gantry may be mounted through the first shield to the base frame. 
   The cover may be located over less than 50% of the first shield. 
   The system may further include an elongated second shield mounted to the base frame on a side of the gantry opposing the first shield, the cover being located over a portion only of the second shield. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of example with reference to the accompanying drawings, wherein: 
       FIG. 1  is a cross-sectional side view illustrating a nonintrusive inspection apparatus according to an embodiment of the invention; 
       FIG. 2  is an enlarged view of a portion of the apparatus; and 
       FIG. 3  is a perspective view of the apparatus. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  of the accompanying drawings illustrates a nonintrusive inspection apparatus  10  according to an embodiment of the invention, including a base frame  12 , first and second shields  14 A and  14 B mounted on the base frame  12 , a bearing assembly  16  mounted to an end of the first shield  14 A, a gantry  18  mounted to the bearing assembly  16 , and an x-ray source  20  mounted to the gantry  18 . 
   The base frame  12  is constructed of various panels  22  that together provide a rigid construction. Each shield  14 A or  14 B is made of a circular pipe having a diameter of 711 mm, a wall thickness of 6.35 mm, and a length L of 2.18 meters. Weld joints secure each shield  14 A or  14 B along its length L to the base frame  12 . 
   Referring to  FIG. 2 , the bearing assembly  16  includes a flange  24 , an inner bearing race  26 , an outer bearing race  28 , and a plurality of circular roller members  30 . The flange  24  has a circular opening which is positioned over a left-hand end of the first shield  14 A. The flange  24  is secured to the first shield  14 A by means of weld joints  32 . The outer bearing race  28  is located around the inner bearing race  26 , with the roller members  30  located in a space between the inner and outer bearing races  26  and  28 . The roller members  30  align the outer bearing race  28  relative to the inner bearing race  26 , while allowing for rotation of the outer bearing race  28  about the inner bearing race  26 . The inner bearing race  26  is positioned adjacent to the flange  24  and secured to the flange  24  by means of a number of bolts  34  (one of which is shown). 
   It can thus be seen that the outer bearing race  28  is mounted for rotation about the first shield  14 A. A simple and inexpensive construction is provided by mounting the bearing assembly  16  directly to the first shield  14 A. As discussed with reference to  FIG. 1 , the first shield  14 A is also rigidly mounted on top of the base frame  12 , in particular because the first shield  14 A is welded along its length L to the base frame  12 . The first shield  14 A thus provides a structure through which the bearing assembly  16  is rigidly mounted to the base frame  12 . 
   The gantry  18  essentially includes opposing gantry plates  40  and interconnection pieces  42 . The gantry plates  40  are spaced from one another and secured to one another by the interconnection pieces  42 . The gantry plate  40  on the right is located against the outer bearing race  28  and secured thereto. The gantry  18  thus rotates together with the outer bearing race  28 . The gantry  18  is typically made of steel and a lead liner  43  is formed on an inner surface thereof, and on inner surfaces of the shields  14 A and  14 B. The lead liners  43  have the capability to substantially attenuate x-ray radiation. 
   The x-ray source  20  is mounted to one of the interconnection pieces  42 , and thus rotates together with the gantry  18 . The x-ray source  20  and the gantry  18  jointly form a rotatable CT scanner subsystem. Power can be provided to the x-ray source  20  so that the x-ray source  20  generates x-rays that are emitted through an x-ray channel  44  and a shutter  45  into the gantry  18  and through a gap  46  between ends of the first and second shield  14 A and  14 B. 
   Referring to  FIG. 1 , the nonintrusive inspection apparatus  10  further includes a conveyor system  50  and a channeling structure  52 . 
   The conveyor system  50  includes conveyor belt rollers  54  and a conveyor belt  56 . The conveyor belt rollers  54  are mounted on opposing sides of the base frame  12 . The conveyor belt  56  runs over the conveyor belt rollers  54  and a portion thereof is always within the first and second shields  14 A and  14 B. 
   The channeling structure  52  includes a number of panels that are positioned within the first and second shields  14 A and  14 B. These panels are spaced from an inner surface of the first and second shields  14 A and  14 B. 
   In use, a container is transferred on the conveyor belt  56  through the second shield  14 B and then through the first shield  14 A. The channeling structure  52  serves to keep the containers on a central area of the belt  56 , and thereby prevents contact between the container and inner surfaces of the shields  14 A and  14 B. The inner surfaces of the shields  14 A and  14 B, and in particular the lead liners thereon, are thus protected by the channeling structure  52 . 
   The contents of the container are scanned in x-ray line-scanning mode by transmitting x-rays from the x-ray source  20  through the container and detecting the x-rays with x-ray detectors  58  that are located on the gantry  18  opposing the x-ray source  20 . In certain instances it may be required to scan the container in CT mode from opposing sides, in which case the gantry  18 , together with the x-ray source  20  and the detectors  58 , are rotated on the bearing assembly  16  about the container. The first shield  14 A provides a rigid construction that allows for acceleration and braking of the gantry  18  without much movement of a center line of the gantry  18  relative to a center line of the first shield  14 A. 
   In another embodiment, it may be possible for the first shield  14 A to be somewhat shorter, without departing from the scope of the invention. The first shield  14 A may, for example, have a length that equals its diameter, but preferably has a length that is at least 1.5 times its diameter. 
   As illustrated in  FIGS. 1 and 3 , the nonintrusive inspection apparatus further has a cover  60  located over the x-ray source  20 , the gantry  18 , and portions only of the first and second shields  14 A and  14 B. The cover  60  includes a number of panels  62  and a door  64  that jointly form an enclosure that seals circumferentially at a periphery  66  on each shield  14 A and  14 B. The door  64  can be opened to expose the gantry  18  and the x-ray source  20 . The cover  60  is located over approximately 0.50 meters of each shield  14 A or  14 B, so that a circular outer surface of approximately 1.67 meters of each shield  14 A or  14 B is exposed. In another embodiment, the cover  60  may enclose a larger portion of each shield  14 A and  14 B, but preferably less than 50% of each shield  14 A or  14 B. 
   The cover  60  serves to protect the rotating components, including the x-ray source  20  and the gantry  18 , and prevents persons from being injured by these rotating components. However, by locating the cover  60  over only portions of the shields  14 A and  14 B, a smaller system is provided. The shields  14 A and  14 B are only approximately 50 inches off the ground, which means that a person on one side of, for example, the shield  14 B, can still see the head of a person standing on an opposite side of the shield  14 B. The cover  60  thus allows for communication between persons on opposite sides of the system  10 , at least across the exposed portions of the shields  14 A and  14 B, while still protecting the persons from the rotating parts of the system  10 . 
   While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative and not restrictive of the current invention, and that this invention is not restricted to the specific constructions and arrangements shown and described since modifications may occur to those ordinarily skilled in the art.