Abstract:
In one embodiment, the invention provides a method for mounting a plurality of detector modules to a rotatable gantry structure for an x-ray detection machine. The method comprises mounting the plurality of detector modules end-to-end to define a stair-step configuration in an x-ray detection zone of the rotatable gantry structure.

Description:
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. 

   FIELD OF THE INVENTION 
   This invention relates to an x-ray technique based non-intrusive inspection apparatus, particularly of the kind that may be used for non-instrusively inspecting closed containers before they are loaded into a baggage hold of an aircraft. 
   BACKGROUND 
   X-ray inspection apparatus used to inspect objects such as luggage at an airport comprise a gantry structure rotatably mounted around a tunnel through which the luggage to be inspected is conveyed. The gantry structure is designed to support an x-ray source at one end of the apparatus and a plurality of x-ray detectors mounted within an x-ray detection zone of the apparatus and located at an opposite end. 
   Each x-ray detector module includes a collimator piece to collimate the x-rays that emerge after passing through the luggage within the tunnel. 
   The x-ray detector modules are bolted to the gantry structure and have to be periodically removed for maintenance purposes. However, existing x-ray detector module designs include heavy lead shielding and therefore tend to be bulky and not conducive to easy removal. This problem is exacerbated by the fact that a service technician is required to unscrew multiple bolts in order to remove a single detector module. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, there is provided a method for mounting a plurality of detector modules to a rotatable gantry structure for an x-ray technique-based non-intrusive inspection apparatus, the method comprising mounting the plurality of detector modules end-to-end to define a stair-step configuration in an x-ray detection zone of the rotatable gantry structure. 
   According to another aspect of the invention, there is provided an x-ray detector module for an x-ray technique-based non-intrusive inspection apparatus, the module comprising a longitudinally extending collimator piece for collimating x-rays; and a housing within which is housed electronics to generate an electrical signal based on x-rays entering the collimator piece, wherein the housing depends from the collimator piece such that the housing is substantially in-line with the collimator piece when the collimator piece is viewed face-on. 
   According to yet another aspect of the invention, there is provided a gantry for an x-ray technique-based non-intrusive inspection apparatus, the gantry comprising a gantry structure defining an opening shaped and dimensioned to fit around an x-ray tunnel of the x-ray technique-based non-intrusive inspection apparatus, and an x-ray detection zone adjacent the opening wherein x-rays passed through the x-ray tunnel are detected; and a plurality of laterally spaced transversely extending mounting formations connected to the gantry structure in the x-ray detection zone. 
   According to another aspect of the invention, there is provided a gantry assembly for an x-ray technique-based non-intrusive inspection apparatus, the gantry assembly comprising a gantry structure defining an opening shaped and dimensioned to fit around an x-ray tunnel of the x-ray inspection machine, and an x-ray detection zone adjacent to the opening wherein x-rays passed through the x-ray tunnel are detected; a plurality of laterally spaced transversely extending cross-beams connected to the gantry structure within the x-ray detection zone; and at least one line of x-ray detector modules mounted end-to-end between adjacent cross-beams to define a stair-step configuration. 
   According to yet a further aspect of the invention, there is provided an x-ray technique-based non-intrusive inspection apparatus comprising an x-ray tunnel through which goods to be inspected pass in use; a gantry structure rotatably mounted around the x-ray tunnel; an x-ray source mounted at one end of the gantry structure; and at least one line of x-ray detected modules mounted end-to-end to the gantry structure to form a stair-step configuration in an x-ray detection zone of the gantry structure, which zone is located opposite the end with the x-ray source. 
   According to yet another aspect of the invention, there is provided an x-ray technique-based non-intrusive inspection apparatus comprising an x-ray tunnel; a conveyor system to convey goods to be inspected through the x-ray tunnel; a gantry structure rotatably mounted around the x-ray tunnel; an x-ray source mounted at one end of the gantry structure; and at least one line of x-ray detector modules mounted end-to-end to the gantry support structure to form a stair-step configuration in an x-ray detection zone at the gantry structure, which zone is located opposite the end with the x-ray source. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of example with reference to the accompanying diagrammatic drawings wherein like reference numbers indicate like or similar components and wherein: 
       FIG. 1  is a perspective view of an x-ray technique-based non-intrusive inspection apparatus according to one embodiment of the invention; 
       FIG. 2  is a cross-sectional side view representing some of the components of the inspection apparatus of  FIG. 1 ; 
       FIG. 3  is a perspective view representing some of the components of a gantry structure for the inspection apparatus of  FIGS. 1 and 2 ; 
       FIG. 4  is a perspective view of the gantry structure of  FIG. 3 , wherein one of the gantry plates has been removed; 
       FIG. 5  is a side-view of one of the gantry plates of the gantry structure shown in  FIGS. 3 and 4 , wherein a stair-step configuration forming part of the gantry structure may be seen; 
       FIG. 6  is a perspective view showing the components of the stair-step configuration in greater detail; 
       FIGS. 7(   a ) to  7 ( c ) are perspective views of some of the components that make up the stair-step configuration; 
       FIG. 8  shows a perspective view of an x-ray detector module mounted between two cross-beams, in accordance with one embodiment of the invention; 
       FIG. 9  is a perspective view showing how more than one x-ray detector module may be mounted between a pair of cross-beams, in accordance with one embodiment of the invention; and 
       FIG. 10  is a side-view of an x-ray detector module in accordance with one embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  and  FIG. 2  illustrate an x-ray technique-based non-intrusive inspection apparatus  10  in accordance with one embodiment of the invention. 
   The inspection apparatus  10  includes a support frame comprising an elongate base  12  and a vertical support in the form of an arch  14  mounted to the base  12  intermediate its ends. A gantry structure  16  is rotatably mounted to the arch  14  via a mounting arrangement (not shown), but will be understood by one skilled in the art to include components such as, a bearing assembly, mounting brackets, etc. 
   The gantry structure  16  rotates about a longitudinal axis  18  of the inspection apparatus  10  (see  FIG. 2 ). The inspection apparatus  10  also includes a conveyor system comprising a conveyor belt  20  rotatably supported on conveyor rollers  22  which are mounted to the base  12  by mounting brackets (not shown). In use, the conveyor rollers  22  are driven by an electric motor (not shown) which in turn drives the conveyor belt  20  so that an article to be inspected, such as an item of luggage  24 , may be conveyed by the conveyor belt  20  from one end  26  of the apparatus  10  to an opposite end  28  thereof. 
   Cover pieces  30  and  32  are mounted to the base  12  on either side of the arch  14  to define a fore loading tunnel section  34  and an aft off-loading tunnel section  36 , respectively. The loading tunnel sections  34  and  36  are separated by an inspection tunnel section  38 . 
     FIG. 3  shows in perspective view of some of the components that make up the gantry structure  16  in accordance with one embodiment of the invention. Referring to  FIG. 3 , it will seen that the gantry structure  16  includes two gantry plates  40  each defining a central aperture  42 . The gantry plates  40  are bolted to opposed ends of transverse support beams  44 . The aperture  42  of each gantry plate  40  is shaped and dimensioned to fit around the inspection tunnel section  38 . In use, an x-ray source (not shown) is mounted in a first zone  46  between the gantry plates  40  and serves as a source of x-rays which pass through an article to the inspected in the inspection tunnel section  38  and enter an x-ray inspection zone  48  between the gantry plates  40 , where they are detected. 
   A plurality of laterally spaced transversely extending support members (mounting formations) in the form of cross-beams  50  are mounted between the gantry plates  40  in the x-ray detection zone  48 . Part of the function of the cross-beams  50  is to provide stiffness to the gantry structure  16  in the x-ray detection zone  48 . Another function of the cross-beams  50  is to provide support for x-ray detector modules  62  as will now be described. 
   As can be seen from  FIGS. 4 ,  5 , and  7  of the drawings, a plurality of x-ray detector modules  62  are mounted end-to-end within the x-ray detection zone  48  to define a stair-step configuration  64 . Each x-ray detector module  62  has a first end  66  and second end  68  which is spaced from the first end  66  along a long axis of the x-ray detector module  62 . A collimator piece  70  extends between the first end  66  and second end  68  and includes a plurality of collimator blades  72  which serve to collimate x-rays that emerge from the inspection tunnel section  38  after having passed through an article to be inspected. Each x-ray detector module  62  also includes a housing  74  which houses electronics (not shown) for generating an electrical signal based on the x-rays detected by a line of x-ray detectors (not shown) immediately below the collimator piece  70 . 
   The housing  74  depends directly from the collimator piece  70  so that when the collimator piece  70  is viewed face-on, the housing  64  is substantially in-line with the collimator piece and is obscured by the collimator piece  70 . 
   Each x-ray detector module  62  has a mounting bracket  76  fast with the first end  66 . The end  68  of each x-ray detector module  62  has a mounting formation  78  which can best be described as a “quick release” type mounting formation which allows the end  68  of a detector module  62  to be secured to one of the transverse cross-beams  50  without the need for a screw type fastener. In order to achieve this “quick release” characteristic of being able to be secured without the use of a screw type fastener, the mounting formation  78  is bifurcated into prongs  80  which are separated by a transverse slot  82 . The prongs  80  are shaped and dimensioned to mate with a cross-beam  50 . 
   As can best be seen in  FIGS. 8 and 9  of the drawings, each cross-beam  50  includes an elongate body which has an upper surface  52 . A longitudinally extending recess  54  runs along a length of the elongate body and along a side thereof. Each cross-beam  50  also includes a rounded nose  56  which runs along the length of the body and is located immediately below the upper surface  52  between the upper surface  52  and the longitudinally extending recess  54 . In use, the prongs  80  of a detector module  62  bear against the ridge  56  which exerts a force which tends to pry open the prongs  80 . The result is that the end  68  of the x-ray detector module  62  is releaseably locked to the cross-beam  50 . 
   Each cross-beam  50  has a lower surface  58  which induces a plurality of screw-threaded bores (not shown). In use, the mounting brackets  76  of each x-ray detector module  62  are secured to the lower surface of each cross-beam  50  by a bolt (not shown) which extends through one of the bores. 
   Referring now to  FIGS. 4 and 6  of the drawings, it will be seen that the stair-step configuration  64  also includes lead shielding plates  84  which are supported by the cross-beams  50  on either side of an x-ray detector module  62 . The purpose of the lead shielding plates  84  is to prevent leakage of x-rays from the gantry structure  16 . 
   The stair-step configuration  64  shown in  FIGS. 4 and 5  of the drawings only include a single line of x-ray detector modules  62 . However, in other embodiments, a stair-step configuration  64  may be constructed which has more than a single line of x-ray detector modules joined end-to-end. In order to form such a stair-step configuration, it is necessary to mount more than one x-ray detector module  62  between a pair of adjacent cross-beams  50 . Such mounting is possible because the cross-beams  50  have a plurality of laterally spaced recessed formations which define seats  86  as can best be seen in  FIG. 9  of the drawings. The seats  86  are shaped and dimensioned to receive a mounting formation  78  of an x-ray detector module  62  therein and to be releaseably locked thereto as described above. 
   An important aspect of the design of the x-ray detector module  62  is that the lead shielding plates  84  do not form part of the x-ray detector module  62 . Thus, when a service technician has to remove a module  62  on the stair-step configuration  64  in order to service or replace the module. Such removal is easily achieved because the modules  62  do not include the heavy lead shielding plates  84 . Further, each x-ray detector module  62  is held in place within the stair-step configuration  64  by only a single bolt which may easily be removed to allow an x-ray detector module  62  to be removed by the service technician. 
   Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modification and changes can be made to these embodiments without departing from the broader spirit of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than in a restrictive sense.