WO2007071890A1

WO2007071890A1 - Container inspection system

Info

Publication number: WO2007071890A1
Application number: PCT/GB2005/005034
Authority: WO
Inventors: Aijaz Anwar; Thomas Bromell
Original assignee: Eg & G Middle East
Priority date: 2005-12-22
Filing date: 2005-12-22
Publication date: 2007-06-28

Abstract

An inspection system provides for inspection of cargo containers. A scanning tunnel has an entrance and an exit, a plurality of scanning entrance doors, each having an open position and a closed position, at least one of the plurality of scanning entrance doors interior to the scanning tunnel; a plurality of scanning exit doors, each having an open position and a closed position, at least one of the plurality of scanning exit doors interior to the scanning tunnel. A scanner is adapted to scan the contents of a container inside the scanning tunnel when at least one of the plurality of scanning entrance doors is in the closed position and at least one of the plurality of scanning exit doors is in the closed position. A carrier carries the container through the tunnel.

Description

TITLE: Container Inspection System

SPECIFICATION

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001 J The present invention relates to the field of inspection systems and in particular, to a system for inspection of containers.

2. Description of the Related Art

[0002] Travelers are familiar with carry-on luggage inspection systems. These systems typically allow a screener to X-ray carry-on luggage and other traveler items that the traveler places on a conveyor belt for inspection. Flexible curtains typically shield the entrance and exit of an X-ray scanning chamber. While in the chamber, a low-energy X-ray source irradiates the luggage, presenting an image on a display for the screener. The system typically requires the luggage to be stationary while being irradiated. Many airports use similar systems for checked luggage, in addition to carry-on items.

[0003] However, such systems are not typically suitable for screening large cargo containers or container transporters, such as large trucks. Low-energy X-rays may not be capable of penetrating the cargo containers or transporters. Further, conveyor belts used by luggage screening systems are typically not suitable for supporting the weight of folly loaded cargo containers or transporters. Previous techniques for screening of such cargo containers include personal inspection by an inspector and metal detection technology, as well as detection of contraband by high-energy X-ray systems.

[0004] The assignee of the present application has implemented a truck-transported cargo container inspection system for a customs agency in China. A radiation shield door at each end of a scanning tunnel blocks radiation from escaping the tunnel. At an entrance location, operators drive trucks onto intelligent platens mounted on rails, after which the driver exits the truck and walks to the exit around the tunnel. When the entrance door opens, the platen carrying the container moves into the tunnel then stops and waits for the entrance door to close. The platen then starts moving again and passes by the scanner, which produces a display for the system operators. After scanning, the platen waits for the exit door to open, then exits, after which the exit doors close. The driver then returns to the truck, drives off the platen,. and exits the area. The platen then returns to the loading area for a future truck. However, throughput of this system is limited because of the need to start and stop the platen to wait for the entrance door and the exit door to open and close, with only one platen allowed in the tunnel at a time. In addition, the platens, which are self-propelled intelligent platens coupled to complex power delivery systems by trailing electrical leads or moving electrical pickup systems, can present reliability concerns.

BRIEF SUMMARY OF THE INVENTION

(00051 Briefly, an inspection system comprises: a scanning tunnel having an entrance and an exit; a plurality of scanning entrance doors, each having an open position and a closed position, at least one of the plurality of scanning entrance doors interior to the scanning tunnel; a plurality of scanning exit doors, each having an open position and a closed position, at least one of the plurality of scanning exit doors interior to the scanning tunnel; a high- energy scanner, adapted to scan the contents of a container inside the scanning tunnel when at least one of the plurality of scanning entrance doors is in the closed position and at least one of the plurality of scanning exit doors is in the closed position; and a carrier, adapted to carry the container through the tunnel.

[0006] In a further embodiment, the carrier is unpowered. In a yet further embodiment, a plurality of friction drive units are operatively coupled to the carrier for moving the carrier through the scanning tunnel. In another embodiment, the carrier is self-propelled.

[0007] In a further embodiment, a conveyor system conveys the carrier through the tunnel. In a yet further embodiment, the conveyor system returns the carrier from the exit to the entrance exterior to the tunnel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] A better understanding of the present invention can be obtained when the following detailed description of various disclosed embodiments is considered in conjunction with the following drawings, in which: Figure 1 is a plan view illustrating a container scanning system according to one embodiment;

Figure 2 is a schematic diagram illustrating interconnection between several subsystems of the scanning system of Figure 1 ;

Figure 3 is elevation view illustrating a scanner subsystem for a container scanning system according to one embodiment;

Figure 4 is a block diagram illustrating platen movement through an embodiment of a container scanning system;

Figures 5-9 are plan views illustrating movement of a truck carrying cargo through the container scanning system of Figure 1;

Figure 10 is a block diagram illustrating a system computer network of one embodiment of a container scanning system;

Figures 11-22 are plan views illustrating use of the scanning system of Figure I;

Figure 23 is a perspective view illustrating the rails and lowerator pits of the system S;

Figure 24 is a top view of the system S, illustrating an exemplary placement of motor drives;

Figure 25 is a perspective view illustrating the load end of the system S without the rails;

Figure 26a is a detail cross-sectional view along line V-V of Figure 24;

Figure 26b is a detail cross-sectional view along line W-W of Figure 24;

Figure 27 is a side view illustrating a lowerator at the primary loading station of the system S;

Figures 28, 29, and 30 are enlarged portions of Figure 27;

Figure 31 is enlarged view of a transverse motor drive unit illustrated in Figure 27; Figure 32 is an enlarged view of a shot bolt illustrated in Figure 27;

Figure 33 is an expended view of a longitudinal motor drive unit illustrated in Figure

27;

Figure 34 is a side view illustrating a lowerator at the secondary loading station of the system S;

Figures 35, 36 37, 38, and 39 are enlarged views of portions of Figure 34;

Figure 40 is a side view illustrating a lowerator at the secondary unloading station of the system S; and

Figure 41 is a side view illustrating a lowerator at the primary unloading station of the system S.

DETAILED DESCRIPTION OF THE INVENTION

[0009J Although the following is presented in terms of an X-ray inspection system, all references to X-rays should be understood as exemplary and illustrative only, and other types of radiation beams can be used for scanning. Further, the terms "cargo" and "trucks" in the following include containers of all types and their contents including self-propelled cargo- carrying apparatus and containers designed to be transported by other modes of transport, as well as self-contained cargo.

(00101 A typical cargo X-ray inspection system according to one embodiment consists of five main elements: a scanning building or tunnel, an X-ray system, a motion system, an information-site control system and ancillaries.

[0011] In a typical embodiment, the system automatically conveys containers through the motion system into a scanning chamber where the container passes through a highly colUmated narrow fan shaped X-ray beam at a constant speed. An array of crystals coupled to sensitive photodiodes detects X-rays that pass through the containers. Electronics located in the same module digitize the signals from the detectors. A number of inspection stations can then use image-processing techniques on data from the X-ray detectors to enhance the radiographic images of the inspected carriers. Based on visual analysis of the X-ray image, the system operator decides whether to call for further intrusive inspection of the inspected carrier. A typical inspection system can inspect containers for 20 hours per day, 7 days a week, 52 weeks per year.

[0012] According to one embodiment, a five-platen motion system is used to carry various types of containers, singly or in multiples, within limits of size and weight for the platens. In one embodiment, the inspection system can inspect 50 containers per hour. The modularity of the system's basic design allows the motion system to continue full operation with the remaining platens if one or more platens are removed for maintenance. Although described herein using five platens, other numbers of platens can be used as desired.

[0013] The system design includes a number of safety features that protect both the operators and the general public. The scanning building ensures that the building will emit radiation levels that are well within known safety requirements.

[0014] Figure 1 is a plan view of a container inspection system S according to one embodiment. A scanning inspection building or tunnel 100 allows inspection of containers with high-energy X-rays without emitting radiation outside the building 100. An X-ray generation room 106 houses an X-ray generator 105, typically a linear accelerator (LINAC), although other types of X-ray generators can be used. A radiation beam 107 from the X-ray generator 105 traverses a scanning chamber 101 of the tunnel 100 as shown and excites detectors in a linear array system (LAS) room 108 as described in detail below. Personal access doors (PADs) 102 allow controlled access to the scanning chamber 101 (PAD 102a), as well as to the X-ray generation room 106 (PAD 102b) and LAS room 108 (PAD 102c), for maintenance and other purposes, as described in detail below. A security fence 109 surrounds at least a portion of the system S, to prevent unauthorized access to the facility.

[0015J Four doors 110, 112, 114, and 116 shield the scanning chamber 101, preventing X-ray emission on either end of the tunnel 100. Although as shown in Figure 1, doors 110, 112, 114, and 116 comprise split doors l lOa-HOb, I 12a-1 12b, 114a-l 14b, and H6a-116b that separate to open, other types of doors can be used, including unitary doors. Although as described below, the doors sections 110a— HOb, 1 12a— 112b, 114a— 114b, and 116a— 116b move sideways to open and close, other door open and close movements can be used. [00161 Two sets of rails or tracks 130 and 135 provide for movement of a plurality of carriers 120, shown in Figure 1 as carriers 120a-120e, in a longitudinal direction, together with transverse rails 140 and 145, allowing the carriers 120 to circulate through the system S. Although Figure 1 shows transverse rails 140 and 145 as comprising three rails each, other numbers of rails can be used. The carriers 120 are described in detail below. Various stations or locations around the system S are also indicated in Figure 1. At process station 1 (150) a loaded carrier 120 prepares to enter the tunnel 100 when door 110 opens. A linear drive or motion system 137, described in more detail below, then moves the loaded carrier 120 into the tunnel 100. At process station 2 (152) the container on the loaded carrier 120 is inside the tunnel 100 and the door 11 Oa-110b can close. At process station 3 (154) the container is scanned by X-ray generator 105. At process station 4 (156) the scanned container exits the tunnel 100, stopping at process station 5 (158). The carrier 120 then traverses buffer station 160 until the carrier 120 reaches unloading station 175, where the inspected container is off-loaded and leaves the system S. The now-empty carrier 120 returns by track 135 to load station 170, where another container can be loaded onto the carrier 120. The loaded container moves through buffer station 165 to the process station 150 to prepare for inspection.

[0017| Not shown in Figure 1 for clarity of the drawing are other buildings or rooms used to house equipment, display stations, maintenance and repair facilities, and offices. These may be situated within the fenced area of the system S or elsewhere as desired. Also not shown in Figure 1 for clarity of the drawing are air-conditioning and heating systems and power generation and distribution systems used to generate and deliver electrical power to the several elements of the System S.

[0018] As best shown in Figure 25, the system S provides access pits at load station 170, process station, process station 150, process station 158, and unload station 175. These pits allow personnel access for maintenance and other purposes to the lowerators used to lower and raise the carriers 120, which are positioned in these pits underneath the rails 130 and 135, as described in detail below. As shown in Figure 25, stairs 2520 provide entry to the floor level of pits 2310 and 2320 from the rail level. Pits 2310 and 2320 can be connected to each other, as can pits 2330 and 2340, allowing maintenance personnel to walk from one to the other. [0019] In one embodiment, as shown in Figure 1, transverse rails 140 extend beyond longitudinal rails 135, allowing moving a carrier 120 out of service. In other embodiments, rails 140 extend as shown in Figure 24, allowing moving the carrier 120 onto another section of longitudinal rails 2410, for removing and maintaining the carrier 120. Other configurations for removing carriers 120 from the main path for maintenance can be provided.

[0020] Access roads typically allow trucks and other container transporters to enter and exit the area. Alternatively, external railroad tracks can provide the ability to deliver and pickup containers from the inspection system S, allowing inspection of rail cargo containers. Other transport modes for transporting containers to and from the system S can be used as desired.

[0021] For truck-transported containers, the driver will dismount the truck after driving the truck onto one of the carriers or platens 120 at the loading station 170, then walk to the unload station 175, reenter the truck after the inspection, and exit the area. Should the X-ray inspection determine the need for further inspection or other action that action or actions can be performed before the driver exits the area.

[0022] Figure 2 is a schematic diagram of an inspection system according to one embodiment, showing how major subsystems of the system S interface with each other.

[0023] Site facilities 200, including shield doors 110, 112, 114, and 116, alarms, closed circuit TV (CCTV), services, power building, fences, and safety systems, provide overall support for the entire system S. A site control system 210 provides a system operator interface 212 for overall control of the site, as well as process control and CCTV- displays. The site facilities 200 also interface with the X-ray generation room or cell 106, including the LINAC 105, the conveyor system 250, and the site control system 210. An X-ray imaging system 220 under the control of the site control system 210 captures images from the LAS room 108 detectors and performs signal conditioning on the images. The X-ray imaging system 220 then transmits those images to the analyst interface 230, which provides a plurality of display stations 235 for analysts to perform image processing and archiving. The X-ray imaging system 220 and analyst interface 230 also interface with data processing facilities 240, which include an administrator terminal 241, manifest scanner 242, and image printer 243, as described in more detail below. One skilled in the art will recognize that the system diagram shown in Figure 2 is illustrative and exemplary only, and other elements and arrangements of elements can be used.

[0024] The design and construction of the tunnel 100 is guided by the International Commission on Radiological Protection (ICRP) recommended limits for the general public or other desired radiation regulations or guidelines.

[0025] Structural elements of the tunnel 100 are built free of cracks and fissure using concrete of density 2350 Kg/m3 compacted to eliminate voids, based on the ICRP recommended limit of lmSv/year. The floor slabs of the building 100 are highly leveled to maintain the exact alignment of the X-ray source 105, collimators, rail tracks and LAS 108. The X-ray cell 106 is separated from the scanning chamber 101 by a radiation shield wall in one embodiment. Entry to the X-ray cell 106 can be controlled through an interlocked Personnel Access Door (PAD) 102b fitted at the entrance of a labyrinth from the scanning chamber 101. The labyrinth is required to shield the PAD 102b from scattered and leakage radiation.

[0026] Entry to the scanning chamber 101 is via a PAD 102 installed at the exit or entry end of the building 100, shown in Figure 1 at the exit end. Other locations for the PAD 102 can be used as desired.

[0027] Suitable techniques can be used in the LAS area 108 to remove water from the lower floor level generated by condensation that may have formed on collimator outer faces. Floor ducts and wall boxes can be provided where necessary for routing cables and hoses.

[0028] Transporter loading and unloading ramps (not shown) can be constructed at the entrance and exit areas of the inspection systems to allow safe transporter movement and support a weight up to a desired limit. In one embodiment, that limit is 60 tons.

[0029] The entire facility is preferably fenced to a desired minimum height to prevent casual entry. In one embodiment, the fence is approximately 2 meters high; however, other fence heights can be used. A driver's walkway guides truck drivers from the entry to the exit end of the system S. [0030] A foil height barrier can be installed at entry of the facility. The barrier can be located at the top of the loading ramp immediately prior to platen entry. A full height barrier can also be installed at the exit of the facility. The barrier can be located at the top of the unloading ramp immediately prior to platen exit. In one embodiment, the barriers are minimum height 2.5 meters, but can be any desired height.

(00311 Each barrier can have sensors fitted that indicate the status of the relative barrier so that if any obstruction is present the sensors can sense this obstruction and return the barrier to the up position. The sensors feed back the status to an X-ray system controller (XSC) of the site control system 210 so that the XSC can control the overall flow with other interlock signals. The XSC will control the operation of these barriers.

[0032] An axle count system, if desired, can be fitted at entrance and exit from the inspection system S immediately before the barriers or directly underneath the barriers so that the system S can count trucks on and off the facilities. In one embodiment, the axle count system is designed such that when a carrier drives over it a signal will be generated and sent back to a system control station of the site control system 210. In another embodiment, sensors can be used to confirm entry and exit of trucks from the facility instead of an axle count system.

[0033] At each end of the tunnel 100, radiation shield doors 110 and 116 are fitted. In one embodiment, the shield doors 110 and 116 are constructed from steel of density 7800 Kg/m3 minimum of such a thickness that the radiation leakage does not exceed the ICElP recommended levels for the general public or local regulations. A radiation overlap is provided to minimize the radiation levels immediately in front of the doors. The shield door design prevents radiation leakage due to scatter at the top and bottoms of each door leaf. Likewise, interior entrance door 112 and interior exit door 114 are similarly constructed and placed interior to the tunnel 100, such that a platen 120 between doors 112 and 114 will have clearance on both ends of the platen 120. Other door constructions can be used.

[0034] AH areas of the building or tunnel 100 can be equipped with air conditioning. In one embodiment, the scanning chamber 101 can be un-air conditioned. In one embodiment, all air conditioning units have fresh air make up facility of 10%; however, other fresh air made up values can be used. A fan and air vent system can be installed between the X-ray cell 106 and scanning chamber 101 to prevent ozone build up in the X-ray cell 106. The rate of air transfer can be one room volume per hour minimum or any other desired rate.

[0035] The X-ray control, power distribution, X-ray cell 106, and LAS room 108 can be controlled to maintain a temperature between 10 ⁰C to 35 ⁰C. The X-ray control room has an aperture fitted in the wall to allow the LINAC hoses and other cables to be routed from the outside. An aperture, in one embodiment by 460mm by 460mm, can be installed in the wall between the LAS room 108 and the scanning chamber 101. A louvered vent can also be installed in the LAS access door 102c.

10036] Figure 3 shows the arrangement of the LINAC 105 and LAS 108 in the X-ray tunnel or building 100. As shown in Figure 3, truck T and its cargo are being inspected by X-rays generated by the LENAC 105.

[0037] The radiation source in one embodiment is a high-energy 9 MeV linear accelerator (LINAC) 105, which has its own control/drive electronics, and can emit 3000 Rads/min @ 1 meter. The LINAC 105 is controlled by a site X-ray control system (XCS) via a set of hardware and software interlocks intended for safe operation. The 9MeV LINAC system 105 consists of an X-ray head (.001% low leakage), a modulator, a water chilled pump stand, a transformer, a control rack, and a voltage regulator. All equipment with the exception of the X-ray head preferably positioned outside of the X-ray cell 106. This 9 MeV setting is typically used for all containers. This setting provides photons of sufficient energy and intensity to penetrate the densest containers and cargos. The actual dose per inspection is expected to be less than 50μSv. However, other LINAC energy settings can be used as desired, as well as varying those settings based on declared cargos.

[0038] The LINAC 105 can be a standard industrial unit, designed for continuous use. A re- circulating chiller can be used to supply cooling water to the X-ray head. The LINAC 105 can be mounted on a platform that will allow alignment of the X-ray head with the collimators and LAS 108. The LINAC 105 mounting platform can be secured to a smooth rendered concrete floor with normal concrete fixings (such as rag or Rawl bolts).

[0039] In one embodiment, the Linear Array System (LAS) 108 consists of a linear array 312 of detector elements mounted directly onto the rear face of Collimator 3 (302). Each detector element comprises a scintillating crystal and photodiode. The array 312 in one embodiment consists of approximately 1600 such elements on a 4.6mm pitch, forming an array of total height of nearly 7.5 meters. The number and pitch of the elements and array height are illustrative and exemplary only, and other numbers, pitches, and heights can be used. Each crystal is individually screened and optically coupled to a separate photodiode. The signal from each photodiode is integrated and digitized within the module, minimizing signal transmission errors and noise intrusion.

[0040] The rear face of the collimator 302, on which the detector elements 312 are mounted, approximates to an arc, focused on the LINAC 105, improving the clarity of the image formed. Other configurations and techniques for improving the clarity of the image can be used.

[0041] The entire array 312 can be housed in a lightproof housing that also provides for air ducting for a forced-air cooling system. A stand-alone control unit 310 that interfaces with the X-ray system controller controls the complete array 312.

[0042] As show in Figure 3, according to one embodiment, there are three collimators used to control the shape of the X-ray beam. Other numbers, placements, and arrangements of collimators can be used. Collimators 1 (305) and 2 (307) are used to form a narrow fan shaped beam that the truck T passes through when being scanned. The beam is only 5.5mm wide when it leaves collimator 2 (307), which minimizes the radiation dose experienced by the item being inspected. The beam width is illustrative and exemplary only and other beam widths can be used as desired.

[0043] Collimator 3 (302) has two main functions. Firstly, it is thick enough to protect the detector electronics from the X-ray beam 107. Secondly, collimator 302 is designed to prevent X-rays that have been scattered by the cargo from reaching the detectors, which would otherwise blur the image. In order to prevent image blurring, collimator 3 (302) has a 4.6mm. wide slot that is over 800mm deep over its entire length. This slot size is exemplary and illustrative only and other sizes and depths can be used.

[0044] In one embodiment, a 5-platen conveyor system is used to offer a smooth throughput of 50 containers per hour, assuming an efficient queuing and loading operation. However, other numbers of platens and throughput rates can be provided as desired. The conveyor system transports the container and its cargo through the X-ray beam. The conveyor system is controlled by the site X-ray control system (XCS); however, the conveyor system contains a degree of built-in intelligence so that the control structure remains simple. The conveyor system in one embodiment can carry containers that have a maximum dimension of 18m in length, 3.5m in width and 4.6m in height with a maximum gross weight of 60 tons. The maximum axle weight of the trucks or other wheeled containers is limited to 12 tons. Other conveyor system and container dimensions and weight limits can be used. Although described herein in terms of single trucks or containers, each platen can carry multiple containers and their cargo if desired, allowing inspection of multiple smaller containers simultaneously.

[0045] The carriers 120 used by the conveyor system to carry the containers through the tunnel 100 are typically flatbed platens. The platen's frames are of a plain carbon steel (such as defined by the BS 4848 and EN 10155 or other suitable standards) construction frame covered on the top surface with a steel plate thus providing a flat working surface. Other grades of steel can be used as desired.

[0046] In one embodiment, standard "A" section railway track is used to guide the platens 120 forming a loop passing through and around the building. The tracks can be mounted on sole plates to aid leveling and provide greater load distribution. Railway technology can be used for laying guide rails. An extra area of rail (not shown) is preferably provided to allow platens to be taken out of the flow of the system S for maintenance purposes.

[0047] Th^e carriers or platens 120 comprise a platform with a hollow section frame around the periphery of it. The platform will have flanged wheels (arranged as pairs) for longitudinal travel and smaller wheels for transverse travel. Other wheel types can be used as desired. The platen platform and frame can be cleaned and blasted in accordance with BS 5493 "code of practice for protective coating of iron and steel structures against corrosion" or other desirable standard and painted with a two-pack coating or equivalent.

[00481 In one embodiment, track transfers are provided for the system S at stations 150, 158, 175, and 170. The purpose of the track transfers is to transfer the carrier platens from longitudinal movement to cross movement and vice-versa. This is achieved by raising and lowering the appropriate tracks to the correct wheels. The raise and lower functions can be carried out by mechanical means using standard 3-phase electrical motors.

[0049] Each transfer system can sustain a load equivalent to the maximum allowable load. In order to provide stability in the X-Y planes, a steel fabricated structure can be used to support the rails. Side restraints can also be provided to prevent undesired side movements.

[0050] In a further embodiment, the carrier loading station 170 can be fitted with a load cell system mounted under the platen lift system enabling the container to be weighed prior to loading into the scanning system. The fabricated track transfer structure is duly shot-blasted and painted in accordance with BS 5493 or other desired standard.

[0051] Lowerators can be used at stations 150, 158, 175, and 170 to raise and lower the platens 120 instead of raising and lowering the tracks. In one embodiment, the longitudinal tracks 135 are elevated 60mm above the transverse tracks 145, the transverse tracks 145 are elevated 60mm above longitudinal tracks 130, and longitudinal tracks 130 are elevated 60mm above transverse tracks 140. The lowerator at the load station 170 lowers the platen 120 and the container carried by platen 120 onto the transverse tracks 145 from longitudinal track 135. After transverse movement of the platen 120, the lowerator at load station 150 lowers the platen 120 from the transverse tracks 145 onto the longitudinal tracks 130. The platen 120 then moves along longitudinal track 130 for scanning. After scanning is complete, the lowerator at unload station 158 lowers the platen 120 from the longitudinal tracks 130 onto the transverse tracks 140. The platen 120 then moves along the transverse tracks to unloading station 175. After the container carried by the platen 120 is unloaded, the lowerator at the unloading station 175 raises the platen 120 onto the longitudinal tracks 135 for return along tracks 135 to loading station 170 for reuse with another container. Thus the lowerators at load stations 170 and 150 and unload station 158 each lower loaded platens 120 by 60mm, while the lowerator at unload station 175 raises unloaded platens 120 by 180mm to recirculate the platens 120. This configuration allows securely lowering fully loaded platens 120, raising only unloaded platens 120. The relative elevations and arrangement of lowerators is exemplar}' and illustrative only and other relative elevations and arrangements of lowerators can be used. The lowerators and their method of operation are discussed in more detail below. [00S2J A drive system provides motion power to the platens 120. Motion power to the platens 120 can be provided by friction drives using 3 -phase electrical geared motors, which can be mounted at a number of strategic positions around the periphery of the guide rails 130 and 135. Any desired positioning of the friction drives can be used for movement of the platens 120.

[0053J Steel hubbed rubber wheels mounted on custom designed axle mountings can be connected to the geared motor units that provide the friction drive. Each motor unit can have its own inverted control thus providing flexibility of speed and acceleration. The rubber wheels then engage the platens 120 to move the platens 120.

[0054] In one embodiment, an independent friction driven encoder can be positioned under the platens 120 while they are being driven past the X-ray beam 107. This encoder can be used to regulate the platen speed through the X-ray 107 and also provide feedback to the X- ray system. In another embodiment, an independent speed measuring device, such as a laser speed measurement device, can be used to confirm the platen speed. Other types of speed measurement devices can be used.

[0055] In other embodiments, other types of drive systems can be used. For example, a motor drive system mounted on the platens 120 can provide self-propelled platens, which may require additional electrical power distribution elements.

[0056] The shielding door leaves llOa-HOb, 112a-112b, H4a-U4b, and I16a-116b can be fabricated from plain carbon steel plate and their thickness is sized to provide adequate personnel protection from radiation outside the X-ray tunnel 100. In one embodiment, each door 110, 112, 114, and 116 comprises two electrically driven trolleys with which the two halves llOa-HOb, 112a-112b, 114a-114b, and 116a-116b of the doors 110, 112, 114, and 116 are mounted. To prevent undue movement in the horizontal plane, the doors 110, 112, 114, and 116 can have floor mounted guide rails. In another embodiment, the doors 110, 112, 114, and 116 are unitary doors.

[0057] The doors 110, 112, 114, and 116 can be powered using positive drives and electric motors controlled via the motion control programmable logic controller (PLC). A separate push button control can be provided to operate the doors in a manual mode of operation. In the event of a power failure, a mechanical recovery system can be provided. The doors 110, 112, 114, and 116 can be grit blasted and painted yellow with black stripes using a two-pack paint system or any other desired color or colors.

[0058] An electrical and control system for the inspection system S can include traffic control interfaces and barrier drive units, an carrier weight load cell interface, a control logic system, platen drive starters and variable speed drive units, platen lift control units, shield door drive units and safety interlocks, X-ray equipment interfaces and safety interlocks, an operator interface SCADA (Supervisory Control and Data Acquisition) system or similar system, power distribution from the main supply panel, proximity switches, limit switches, safety light curtains and emergency stops, and cable installation associated with the above. In one embodiment, the control logic system is an Allen Bradley ControlLogix PLC. Other control logic systems, such as a Seimens Control System, can be used.

[0059] The system can be powered from a 3-phase 380-480VAC supply and all power requirements are preferably derived from the incoming supply.

[0060] A main control panel containing the power distribution and PLC can be fitted with cooling fan and filters. The control panels can be housed under cover in a temperature- controlled environment.

[0061] Motor sizes are designed to meet the load and acceleration requirements of the system. In one embodiment, all motors can be controlled by Allen Bradley 1336 Impact Adjustable Frequency Drive Units or their equivalent. In another embodiment, Siemens motors can be used. These will allow ambient operating temperature range of 0-50 C, speed adjustment directly from the PLC or SCADA via a communications network, and motor overload protection.

[0062] Hardwired protection is preferably provided to prevent the X-ray unit 105 from activating until at least one of entrance shielding doors 110 and 112 and at least one of exit shielding doors 114 and 116 are closed. Locks to prevent the PADs 102 opening while the X- ray unit 105 is activated can be provided via a key exchange system or other desired interlocks. [0063] The PLC control system can be based on the Allen Bradley ControlLogix range of equipment or any other desired logic system, such as a Siemens system.

[0064] A communication networks can allow communications between the PLC, I/O modules, load cells, motor controllers, SCADA and PLC programming terminals and the system operator computer terminal, as described below.

[0065] An operator interface 212, can allow the operator to control and monitor the carrier handling system from on-screen buttons and displays, providing access to the handling system status information, set points and fault information. A printer can be included if system information or faults are to be printed. Any SCADA or HMI (Human Machine Interface) system can be used for the operator interface 212. In one embodiment, the operator interface 212 is based on the Allen Bradley RSView 32 SCADA package. In another embodiment, the operator interface 212 can be a system provided by Siemens. [Inventor: please identify the Siemens system by name for best mode purposes.]

[0066] Figure 4 is a block diagram illustrating movement of platens 120 around the system S. Containers are loaded onto an empty platen 120 at load position 400, corresponding to the load station 170 of Figure 1. Once loaded, the platen 120 will move on transverse tracks 145 as shown in block 405, to load position 410, corresponding to process station 150 of Figure 1. When door 110 opens, platen 120 moves into entry position 415, corresponding to process station 152 of Figure 1. Without stopping, platen 120 continues to move as door 112 opens, allowing entry to the screening area 420 in the screening chamber 101, while door 110 closes. Once door 110 closes, if one of doors 114 or 116 is closed, the platen 120 can continue to move without stopping through the screening area 420 and beam 107. In one embodiment, the platen 120 once entering entry area 415 moves at a constant nominal scanning speed of 0.5 m/s ± 5%, until exiting the tunnel 100. In another embodiment, the platen 120 moves at 1 m/s until it reaches the beam 107, then slows to .5 m/s while being scanned, then accelerates back to 1 m/s to exit the tunnel 100. Other speeds can be used. Non-stop movement allows higher throughput by avoiding the need to reaccelerate a stopped platen to the desired scanning speed.

[0067] A number of alternative methods of operation can be provided to allow operation of the motion system at a reduced capacity in the event of breakdowns. For example, instead of recirculating platens 120, forward and backward movement of the platens through tunnel 100 can be used, at a correspondingly lower throughput rate.

[0068] The normal mode of operation of the inspection system S is described below with respect to Figures 5-9. The indicated actions are illustrative and exemplary only, and other actions and order of actions can be performed.

[0069] First, a transporter, such as a truck 500 drives to the barrier at load position 170. A traffic light and barrier system controls the transporters entering the facility. The driver then drives the truck 500 onto platen 120a, as shown in Figure 5.

[0070] At an appropriate point in the sequence for the preceding carrier, the system controller will raise the entry barrier, thus indicating to the driver to drive the transporter onto the loading area 170 of the conveyor system. The transporter can be weighed prior to or after driving onto the loading area 170.

[0071] Once a transporter or container is loaded onto platen 120a, the driver leaves the transporter and goes to register the transporter's cargo with a site administrator. The administrator enters all carrier and cargo details onto an electronic data processing (DP) form on a data entry terminal 1060, described below with respect to Figure 10. The administrator also produces a scanned image of the cargo manifest documents). The image is filed automatically with the DP form. Once registered, the driver leaves the entry area and walks around the building to the exit area to await the driver's transporter.

[0072] Manifest details are entered into the system as a scanned image. This task is carried out before the carrier is X-rayed. Manifest images will be logged with reference to a carrier number to allow the system to match the manifest against the X-ray image generated.

[0073] The system associates a DP record with every X-ray image generated. The layout and content of the DP record form can be customized as desired.

[0074] The platen 120a is then side transferred to the buffer position 145 on the side transfer. If, however, process station 150 is vacant, the platen 120a travels to that position as shown in Figure 6. The truck 500 is preferably weighed prior to the side transfer. [0075] The entry door 110 then opens. On confirmation of door 110 being open, the platen 120a enters the X-ray building 100. Warning klaxons and flashing lights activate as the platen accelerates to 1 m/s and enters the building via the shield door. Platens 12Ob-12Oe are correspondingly moving around the system S as shown.

(00761 The platen 120a enters and exits the facility via shield doors HO, 112, 114, and 116, which protect personnel from the X-ray source. Hardwire safety interlocks are provided to prevent the source being exposed unless the doors are closed. Platens are moved through the system by the friction drives, as described above.

[0077] When one of doors 110 and 112 is closed and one of doors 114 and 116 is closed and the safety interlocks are engaged, the site control system 210 commands the X-ray system control computer to initiate the generation of X-rays from the LINAC 105. The platen 120 is then moved at constant speed through the X-ray beam. Having penetrated the cargo, the resultant X-ray beam is detected by the linear detector array 312.

[0078] The X-ray beam at the array is converted to a "slice" of electrical signals. The signals are amplified and integrated for a period equivalent to 4mm of cargo movement. The resultant signals are then digitized and stored in a computer as one "slice" of the X-ray image. Continuous storage of these slices results in an image of the whole carrier being generated with pixel sizes of 4mm by 4mm.

[0079] The data stored in each pixel is represented by a 16-bit digital word, which provides a range of contrast information that can be manipulated by the processing software to maximize image quality.

[0080] As stated above, in one embodiment, the platen slows down from 1 m/sec 0.5 m/sec when passing the X-ray as shown in Figure 7. As the X-ray process takes place, the X-ray control system carries out signal conditioning to correct for environmental tolerances within the array. The system also monitors the LINAC 105 output and carries out a correction for any variation. [0081] The platen continues to move past the X-ray. Once the platen 120a has cleared the X- ray, it is accelerated to a speed of 1 m/sec and exit doors 116 are allowed to open allowing the truck to exit the tunnel 100 as shown in Figure 8.

[0082] The X-ray screening images are displayed on one of the analyst display stations 235 in the inspector room for assessment. The platen 120a is then side transferred to the unload station 170. The driver is allowed to remove his truck as shown in Figure 9, normally in approximately 30 seconds. Once the carrier has come to rest in the exit area, the personnel gate giving access to the exit area by the driver is unlocked. The driver returns to his carrier and the exit barrier is lifted. The carrier may then be driven off and parked in a holding area awaiting a decision on the scan that has taken place. Any suspect container can be checked manually.

[0083] As a carrier is moved to the holding area, the scan assessment relating to it is printed out on the exit printer 1052 described below.

[0084] The Iowerator at the unload station 175 then lowers the platen 120a and the empty platen 120a is then driven to the load position 170.

[0085] What has been described above is the normal operating mode of the system S. A secondary or manual operating mode can also be provided. In this mode, the system operator is given control of each individual piece of equipment, allowing the operator, for instance, to open and close shield doors, start and stop sub-systems, etc. Manual mode provides a first- line maintenance, inspection, and diagnostic tool to allow detailed control of the system S from a central point. The system, even in manual mode, still implements all internal safety checks to ensure that X-ray alarms are sounded before emission, no attempt is made to emit X-rays with the shield doors open, etc.

[0086] The site control system 1000 is a distributed processing system that provides overall control of the system, coordinating the operation of the other sub-systems and carrying out all data processing functions. The various systems are linked via an Ethernet network 1005 or other desired networking technology, which is illustrated in Fig 10. Any desired wiring or networking system can be used to interface sensors and other devices to the operator's control station 1010, including AS-Interface devices and wiring. The majority of the systems on the network can use standard commercially available hardware.

[0087] In one embodiment, communication and control of the site control system 1010 and the associated devices adhere to the Actuator Sensor-Interface (AS-I) standard. The specification of the AS-I standard is described in Werner R. Kriesel & Otto W. Madelung, AS- I Interface The Actuator-Sensor-Interface for Automation (2nd ed. 1999) and discussed in the following patents (all of which are hereby incorporated by reference in their entirety for all purposes): U.S. Patent No. 6,294,889 for a Process and a Control Device for a Motor Output Suitable for being Controlled through a Communication Bus, U.S. Patent No. 6,378,574 for a Rotary Type Continuous Filling Apparatus, U.S. Patent No. 6,332,327 for a Distributed Intelligence Control for Commercial Refrigeration, U.S. Patent No. 6,127,748 for an Installation for Making Electrical Connection Between an Equipment Assembly and a Command and Control System, U.S. Patent No. 6,173,731 for an Electroβuidic Modular System, U.S. Patent No. 6,222,441 for a Process and Circuit for Connecting an Actuator to a Line, U.S. Patent No. 5,978,193 for a Switchgear Unit Capable of Communication and U.S. Patent No. 5,955,859 for an Interface Module Between a Field Bus and Electrical Equipment Controlling and Protecting an Electric Motor.

(0088J The operator's control station 1010, corresponding to station 212 of Figure 2, is used to display the status of the inspection system. A mimic display 1004 is used to show the position of each carrier as it passes through the X-ray scanner. The doojs 110, 112, 114, and 116 are shown as open, closed, opening or closing. Other information such as the status of the image analysis stations 1040 is also displayed on screen 1014. An error message from any of the subsystems will result in the icon representing that subsystem changing color to indicate either a potential problem or one that has stopped the system. Digital I/O circuits 1012 connect the control station 1010 to doors, alarms, and other sensors.

[0089] The operator's control station 1010 is also used to drive the system when in maintenance or manual mode. In this state, each stage of the scanning cycle can be started manually by selecting the appropriate icon on the display. This mode can be used during commissioning or when carrying out repairs to the system. Under certain fault conditions, it also allows continued operation of the system while waiting for a repair to be carried out. [0090J The control station 1010 is also connected by network 1005 to the XCS 1020, which uses digital I/O interface 1022 to connect to the LINAC 105 and LAS 108, receiving raw X- ray data as desired.

[0091] Six analysis stations 1040, corresponding to stations 235 of Figure 2, are provided to monitor traffic through the system S. Each image analysis station 1040 consists of a high- performance image processing workstation, equipped with stand-alone graphics workstations and two color monitors 1042 and 1044. Monitor 1042 displays the X-ray image and the monitor 1044 displays the manifest data and Data Processing form. This provides a graphical user interface where all commands can be entered by using icons.

[0092] All operations on the image screens 1042 and 1044 can be controlled using a mouse. Images are scrolled using slider bars. Areas of interest can be selected by clicking and dragging the mouse. Image processing functions, including zooming, can be invoked by clicking on icons. The mouse cursor will only appear on one screen at a time. As it moves out of the right side of the one screen, it will appear on the left of the other.

(0093] The analysis station 1040 contains sufficient disc space to hold copies of at least two images: the one currently being viewed and the next in line. This means that when the analyst has finished viewing one the analyst can immediately start looking at the next without waiting for it to be passed from the server.

(0094] By default, the analyst is provided with an image already enhanced by an image- processing algorithm specifically developed for optimizing the images obtained from the container. The analyst can then conduct a search procedure that shows every part of the image enhanced in this way, giving the analyst opportunity to spot any anomalies in the shortest possible time. The analyst may stop this procedure at any desired time, apply further enhancements, or print out a color copy of the enhanced image.

[0095] A wide range of enhancements can be provided together with the flexibility to apply the enhancements in multiple ways. Enhancements may be applied to the complete viewing area or just a portion of it and enhancements may be nested in any order. The analyst can also be provided with an "undo" facility to go back a step if an enhancement does not have the desired effect. [0096] While viewing an image, or having viewed the entire image, the analyst enters an assessment. This is typically made up of two parts: a required recommendation and an optional justification. The recommendation can be one of clear, search (suspicious object or misrepresentation identified), or caution (uncertain, may need to search). If the "caution" recommendation is entered, then the analyst can enter one or more of the following justifications: cargo too dense, cargo too complex, or anomaly identified.

[00971 These assessments can be entered using an icon-based system. These assessments and justifications are exemplary and illustrative only and other assessments and justifications can be used. ,

[0098J A central server 1030 holds any image data that is waiting to be analyzed. This computer is also used to store the images in online storage 1032 from at least the last 600 or other desired number of carriers that have been scanned. In addition, image files can be stored on permanent media, such as archive tape drive 1034, for long term archiving.

[0099J Once an assessment has been entered, the analyst "closes" the viewed image. This deletes the copy of the image held in the display station 1040 but not affect the "master" copy held by the system server 1030. The "master" copy remains available for archiving or for other analysts to view, together with the DP record, including the assessment, and the manifest associated with that image.

[00100] Some text may need to be input to accompany the image file. This includes the customs inspector's identification, the result of the analysis and any comments. This data can be input onto the screen 1044 containing the manifest image using a conventional keyboard.

[00101] Data processing functions such as the routing and storage of manifest data, carrier details, inspection results, etc. are carried out by the system control 1010, analyst display stations 1040 or any of the terminals connected to the system such as exit station 1050 and entrance station 1060. When the driver provides the manifest for the container to be inspected to personnel at the entrance station, the manifest can be scanned by the scanner 1062, checked on display 1064, then sent to the appropriate analyst workstation 1040, where the analyst can see the manifest on screen 1044 to compare with the digitized X-ray image on screen 1042. [010Oj The exit station 1050 allows exit personnel to view inspection results on screen 1054 and print any desired papers on printer 1052 for delivery to the driver or for any other desired purpose. This provides a computerized "forms management" system, which ensures that manifest data, X-ray images and inspection results are kept together.

[0101] The site control system 210 controls building entry and exit X-ray shield doors. Door interlocks and alarms are provided to ensure a high level of safety, with the system controller 1010 monitoring all relevant equipment as part of its sequence control function. Current sensing circuitry can be included in all alarms to further enhance the safe operation of the equipment. In addition, public address and CCTV facilities can be provided for the system operator's use.

[01021 The following safety features can be built into the building and equipment in a typical embodiment.

[0103] All equipment, buildings, spares and procedures are designed, constructed, implemented and operated so as to materially comply with all relevant national legislation on safety issues. No personnel will be allowed in any hazardous area during X-ray processing, i.e., scanning chamber 101, Linear Array System (LAS) room 108 and the X-ray Cell 106 housing the LINAC 105.

[0104] The sliding shield doors 110, 112, 114, and 116 have a safety feature intended to prevent objects from being crushed. Detection of an obstruction will stop the doors and, in turn, the conveyor system will be brought to a safe condition. A maintenance activity will then be required to reset and allow the cycle to continue.

[0105] Doors-closed switches are provided to inhibit X-ray generation when the appropriate shield doors 110, 112, 114, or 116 or any of the personnel access doors are not fully closed. A fully integrated safety interlock system can be supplied.

[0106] A controlled access key system can be provided to allow safe entry to the facility and also allow a search and seal activity when leaving the X-ray Cell 106 and X-ray scanning chamber 101 after maintenance activity. This access system can utilize a system of interlock doors, door locks, and key switches. [0107] Fire detectors can be fitted to all areas. Fire alarms should preferably be audible and comply with local regulations. Extinguishing facilities, preferably non-automatic, suitable for electrical and combustible material fires can be provided in accordance with local regulations.

(0108] Audible and visual alarms are provided that operate whenever there is movement by the conveyor system or the shield doors 110, 112, 114, and 116.

[0109] The energizing of alarms in operational and maintenance mode can be for the duration of any conveyor system movement or shield door operation and controlled by the site control system unit (SCS) 210.

[0110] To provide audible and visual indications of potentially hazardous conditions, the SCS 210 can initiate a minimum of 3 internal audible/visual alarm units. Other numbers and types of alarms can be used.

[0111] In addition, in one embodiment, there are three external visual alarms: one situated at the entrance and exit, and one adjacent to the X-ray scanning chamber 101.

[0112] Emergency stops are provided to enable power to be isolated manually. When initiated they require a mechanical reset function before normal operation can be resumed. Emergency stops positions and instructions are clearly marked.

[0113] Emergency stop buttons can be situated at frequent intervals in the X-ray scanning chamber 101, close to maintenance control points, at the X-ray supervisor's console 1020, adjacent to the LINAC control rack, in the X-ray Cell 106, in the LAS room 108, in the entry ^"'reception area between doors llO and 112, and in the exit area between doors 114 and 116.

[0114] In addition, a pull-wire emergency stop system can be supplied along the entire length of the X-ray tunnel 100. Other emergency stop systems and locations can be used.

[0115] Six closed circuit TV cameras are provided in one embodiment. One camera is positioned at each end of the scanning chamber 101 looking along the tunnel 100. The other cameras can be externally mounted at the entry and exit areas, and can be directed to view the loading and unloading positions 170 and 175. [0116] Six CCTV monitors can be supplied according to one embodiment. These can be connected one to each of the CCTV cameras or in any other desired way, and will form part of the System Operator's station 1010, to indicate the logical sequence of cargo movement through the facility. Other numbers, arrangement, and placement of CCTV cameras and monitors can be used.

[01171 Two communications systems can be supplied. The main X-ray facility can have a public address (PA) system covering the carrier entry and exit areas. A jack-socket intercom system can also be provided in the several areas of the system S, to enable communications between personnel during maintenance activities. Typical intercom locations are in the scanning chamber 101, the X-ray cell 106, the LAS room 108, maintenance positions (entry and exit), in the operations/display areas, in the LINAC Control Area (typically located within an electrical services room), in an entry reception room, in an exit room, and in the electrical services room.

[0118J To maintain site safety, radiation-monitoring equipment is provided to allow regular site surveys for radiation leakage.

[0119] The system design incorporates fences, barriers, audio/visual warnings, and operational control procedures to reduce the risk of injury to operational personnel and to drivers of carriers. Both entry and exit areas can be surrounded by fencing of a height sufficient to prevent casual entry. Carrier movement is controlled using pivoting or other movable barriers with warning lights for low visibility operation. Personnel can gain access to controlled areas via secure turnstiles that can require them to have been operated before the control system initiates the next operation in the handling of the containers.

[0120] Notices can be displayed in operation and maintenance areas to warn personnel of certain potentially hazardous equipment. These notices should comply with local, national, and international standards as required.

[0121] Radiation symbols can be painted on the main entry and exit shield doors.

[0122] Nominally, in a disclosed embodiment as described above, the display resolution, as determined by the array geometry, is 4 mm. However, because of the wide dynamic range of the detection and imaging system and because incoming signals to the LAS are integrated over a short period of time, objects significantly smaller than 4mm can be imaged successfully.

[0123] At a scan rate of 0.5 meter/sec as described above, the inspection systems is capable of imaging a step as small as 0.5mm in 100mm of steel and a step as small as 9mm in 300mm of steel. It is also capable of imaging wires of 2mm diameter behind 100mm of steel and wires of 9mm diameter behind 300mm. Other embodiments can have other resolution capabilities.

[0124J Figures 11-22 are plan views of an inspection system according to one embodiment, showing movement of several trucks T0-T5 through the system S, illustrating movement of two carriers through the tunnel at various times. In Figure 11, truck TO has exited the tunnel 100 after inspection. Platens 120a and 12Oe are now empty, ready to be recirculated. Meanwhile, because door leaves HOa and 110b abut each other when closing door 110, and door leaves 114a-114b abut each other when closing door 114, truck Tl can be scanned by the X-ray generator 105, even though interior door 112 is open with leaves 112a-112b separated. Truck T2 is waiting at process station 150, while truck T3 is ready to load onto a platen 120. In the embodiment of Figures 11-22, load station 170 and unload station 175 are in the transverse rail 145 and 140 areas, rather than at the junction of rails 135, 140, and 145 as shown in Figure 1.

[0125] Turning to Figure 12, truck Tl has continued through the beam 107, interior entrance door 112 is closing and interior exit door 114 is opening, while door 110 (and door 116, not shown) remain closed. Figure 13 shows truck Tl beginning to move through door 114 with door 112 now fully closed, allowing truck T2 to begin entering through open door 110, even though truck Tl is still being irradiated by X-ray beam 107.

[0126] In Figure 14, truck Tl approaches opening door 116, while truck T2 continues to enter tunnel 100. At this point, all four doors 110, 112, 114, and 116 are at least partially open. Truck TO has moved transversely to unload station 175, while truck T3 has loaded at load station 170 onto platen 12Oe. Truck T4 awaits loading, while platen 120a is moving along track 135 (not shown) back to the entrance end of tunnel 100. [0127J Turning to Figure 18, door 114 has closed, while truck Tl is still exiting tunnel 100. This allows scanning of truck T2 by beam 107, because door 110 is also closed. Truck TO has been unloaded from platen 120b, which can then recirculate. Continuing with Figure 16, truck T2 is being scanned as door 114 is opening, while doors 110 and 116 are closed and door 112 is closing. Platen 120a is now ready to move to load station 170.

[0128] In Figure 17, truck T4 has loaded onto platen 120a and truck T3 is waiting for door 110 to fully open before entering tunnel 100, even though truck T2 is still being scanned. T2 moves through open door 114 towards closed door 116. Continuing to Figure 18, the X-ray generator is off, even though doors 112 and 116 are fully closed, because truck T2 has now passed the plane of X-ray beam 107 (not shown). Truck T3 has begun to enter tunnel 100. Platen 120b is recirculating. Then in Figure 19, door 116 begins to open when truck T2 approaches the door 116, as shown by separated door leaves 116a and 116b. Truck T2 has not stopped moving while inside tunnel 100, because the conveyor system and site control system control the ^"movement of doors and platens together. Likewise, truck T3 continues forward to nearly fully open door 112 without having to wait for truck T2 to exit tunnel 100. Truck T5 has arrived and waits to be loaded onto a platen 120, while truck T4 waits in buffer station 165 for truck T3 to leave process station 150.

[0129] In Figure 20, all four doors 110, 112, 114, and 116 are fully open, as trucks T3 and T4 continue moving through tunnel 100. Doors 112 and 114 are positioned within tunnel 100 far enough apart to accommodate the longest container to be _^scanned between them, plus clearances on either end. The length of tunnel 100 is also determined by the maximum desired container length, so that there is clearance between door 110 and the maximum length container, and simultaneously between the container and the beam 107. Likewise, the tunnel 100 provides clearances for the maximum length container between beam 107 and door 116. Note in Figure 20, truck Tl is being driven off platen 120c.

[0130 J In Figure 21 , door 110 is closing, while door 112 is folly open and truck T3 is passing the plane of door leaves 112a and 112b. Door 114 is closed, while truck T2 exits runnel 100 through door 116. Figure 22 then shows truck T4 moving towards load position 150, while truck T3 is being scanned, and while truck T2 finishes leaving the tunnel 100. Empty platens 120b and 120c are now being positioned for other trucks, such as waiting truck T5. [0131] Figure 23 is a perspective view illustrating the rails and pits at the lowerator stations of the system s. Pits 2310-2340 provide mounting space for lowerators and access underneath the rails for maintenance. As described previously, trucks or other container transporters are loaded onto a carrier 120 at primary load station 170. The carrier 120 is then lowered by a lowerator (not shown in Figure 23) onto transverse rails 145 and side transferred to station 150. At station 150, carrier 120 is again lowered to the level of rails 130 for passage through the scanning tunnerl 100 (not shown). At station 158, the carrier 120 is again lowered to the level of transverse rails 140 and side-transferred to primary unload station 175. As noted before, stations 150 and 158 can serve as secondary load and unload stations, if necessary or desired.

(0132] Figure 24 is a top view illustrating an exemplary placement of friction motor drives in the system S. Motor drives 2400a-2400p are spaced along and between rails 130. Motor drives 2410a-2410j are similarly spaced along and between rails 135. Motor drives 2420a- 242Oh and 2430a-2430h are spaced along the outside of fails 145 for transverse movement. Likewise, motor drives 2440a-2440h and 2450a-2450h are spaced along rails 140 for opposite transverse movement. These motor drives are described in more detail below. The spacing and number of drives 2400, 2410, 2420, 2430, 2440, and 2450 in Figure 24 are illustrative and exemplary only, and other numbers and arrangements can be used.

[0133] Figures 26a and 26b show cross-section views of the system S along lines V-V and W-W, respectively, showing placement of the lowerators in pit 2310.

[0134] Figure 27 is a side view of lowerator 2700 at station 170. As shown in Figure 27, bogies 2710, 2720 and 2730 of the carriers 120 include wheels for both longitudinal and transverse movement. Turning to Figure 28, an enlarged view of the left most portion and bogie 2710 of Figure 27 illustrates a number of features. A bumper 2805 prevents damage to an end of the carrier 120. A motor drive unit 2810 provides transverse motive power for the carrier 120 when lowered to the rails 145 from rails 135. Wheels 2820a and 2820b are standard railroad wheels, for travel along longitudinal rails 130 and 135. Wheel 2815 is also a standard wheel, but is mounted for transverse movement. Additional wheels for the second rail of each longitudinal pair of rails, as with conventional rail road bogies, but not visible in this view. To lower the carrier 120, hydraulic pistons 2840a and 2840b lower short rail sections 2830a and 2830b for the longitudinal wheels of the bogie 2710. Figure 28 shows these rail sections lowered, allowing wheel 2815 to contact rail 145 for transverse movement. Motor unit 2810 will then be pivoted upwards so that the wheels engage the under surface of carrier 120. Skates 2845, in one embodiment caterpillar action skates manufactured by Dorvic Engineering Ltd., provide stability during upward and downward movement of the carrier 120. When in the lowered position, rail sections 2830a and 2830b are below wheels 2920a and 2820b, allowing the wheels 2820 to pass above those rail sections when moved transversely.

[0135] Figure 29 is an enlarged view of a middle portion of the carrier 120 and bogie 2720. A friction motor drive unit 2950, described in more detail below, provides motive power for longitudinal movement. As with Figure 28, pistons 2910a and 2910b extend and retract to raise and lower short longitudinal rail sections 2930a and 2930b to variously engage with wheels 2920a and 2920b or transverse wheel 2915. As shown in Figure 29, transverse wheel 2915 does not use a wheel flange on either side of middle transverse rail 145. Again, skates 2845, provide sideways stability for the lowerator during lifting and raising. As shown in Figure 29, the lowerator 2700 is in the raised position, allowing wheels 2920a-2920b to roll along rail 130 for longitudinal movement. Retracting pistons 2910a and 2910b lowers rail sections 2930a and 2930b, as well as drive unit 2950, disengaging motor drive unit 2950 from the carrier 120. Figure 30 shows the other end of carrier 120, with pistons in their extended position, allowing wheels 3020a and 302Ob to roll along rails 135. A shot bolt 3030 can be used to lock the carrier 120 into place to prevent longitudinal movement while loading the carrier 120.

[0136] Figure 31 provides an enlarged view of transverse friction motor drive 2810, corresponding to drives 2420 and 2430 of Figure 24. Wheels 3020a and 3020b use elastomeric tires for friction drive and are powered by motor 3010. Motor drive 2810 pivots on axle 3030, allowing the wheels 3020a and 3020b to move up and down as necessary for maintaining contact with the carrier 120. A spring (not shown) vertically positions the wheel end of the motor drive, as described below in the description of Figure 33.

[0137J Figure 32 is an enlarged view of the shot bolt 3030 of Figure 30. Actuator 3210 can be extended or retracted, to engage bolt 3220 with a formation 3230 on the underside of carrier 120. Figure 32 shows formation 3230 in both a raised and lowered position, corresponding to raised and lowered positions of the carrier 120. The use and configuration of shot bolt 3030 is exemplary and illustrative of shot bolts 3030 can be used. Other techniques can be used to hold the carrier 120 in place, and other configurations of shot bolts can be used.

[0138] Figure 33 is an enlarged side view of motor drive unit 2950 of Figure 29. Motor drive 2950 is identical in construction to drive 2810 shown in Figure 31. In this view, spring 3310 is shown, allowing the wheels 3020 to move up and down as needed. However, drive unit 2950 is longitudinally mounted between the longitudinal rails. In addition, although most of the longitudinal motor drives are fixed to the floor between the rails, drive tinit 2950 is mounted so that extending pistons 2910a and 2910b raises and lowers motor drive 2950, allowing it to engage or disengage the underside of carrier 120 as desired.

[0139] Figure 34 is a side view of the lowerator 3400 at process stations 150 of Figure 1. As with the lowerator 2700 of Figure 27, lowerator 3400 lowers the carrier 120 from transverse rails 145 to rails 130. Unlike lowerator 2700, however, the lowerator 3400 lowers the carrier on the transverse wheels of bogies 3410, 3420 and 3430, as shown in enlarged Figures 35, 36 and 37. Note that lowerator 3400 is mounted underneath the rails 130 in pit 2320.

[0140] Enlarged Figure 35 shows that piston 3510a of lowerator 3400 lowers drive unit 3550 away from carrier 120. Piston 3510b lowers a small section of rail 3530, lowering the carrier onto rails 130. As piston 3520b lowers rail section 3530 below the level of rail 130, wheels 3520a and 3520b engage rails 130, while wheel 3515 disengages from rail 145. Enlarged Figure 36 correspondingly illustrates piston 3610, which lowers middle wheel 3615 until wheels 3620a and 3620b engage rails 130. Motor drive units 3650a and 3650b are shown pivoted into compressed configurations as they would be when engaged with the carrier 120 for moving the carrier 120 along rails 130. Likewise, enlarged Figure 37 shows pistons 3710a nd 3710b lowering wheel 3715 and drive unit 3750.

[0141] Figure 38 illustrates motor drive unit 3750 mounted on a platform 3810, which can then be lowered and raised by piston 371Ob. Figure 39 illustrates drive unit 3650a, which is mounted on a fixed structure 3910 next to the rail section 3730 lowered by piston 3610.

[0142] Figures 40 and 41 illustrate lowerators 4000 and 4100, located at stations 15S and 175 respectively. Lowerator 4000 is similar in structure to lowerator 2700, lowering carrier 120 onto transverse rails 140. Shot bolts 4040a and 4040b lock carrier 120 in place during operation of lowerator 4000. Lowerator 4100 is the only lowerator that raises carrier 120, raising it to the level of rails 135 by the sum of the distances the carrier 120 was lowered by lowerators 2700, 3400, and 4000. Otherwise, the technique and structural elements are the same as described above. By lowering carrier 120 with lowerators 2700, 3400, and 4000, then raising carrier 120 with lowerator 4100, the system S avoids raising a loaded carrier 120. Shot bolts 4140a and 4140b allow locking the carrier in place during operation of the lowerator 4100.

[0143] The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the details of the illustrated apparatus and construction and the method of operation may be made without departing from the spirit of the invention.

Claims

CLAIMS We claim:

1. A system, comprising: a scanning tunnel having an eαtrance and an exit; a plurality of scanning entrance doors, each having an open position and a closed position, at least one of the plurality of scanning entrance doors interior to the scanning tunnel; a plurality of scanning exit doors, each having an open position and a closed position, at least one of the plurality of scanning exit doors interior to the scanning tunnel; a scanner, adapted to scan the contents of a container inside the scanning tunnel when at least one of the plurality of scanning entrance doors is in the closed position and at least one of the plurality of scanning exit doors is in the closed position; and a carrier, adapted to carry the container through the tunnel.

2. The system of claim 1, wherein the carrier is unpowered.

3. The system of claim 2, further comprising: a plurality of friction drive units, operatively coupled to the carrier for moving the carrier through the scanning tunnel, each comprising: an electric motor; and an elastomeric wheel mounted on the electric motor, the elastomeric wheel providing friction drive power to the carrier.

4. The system of claim 3, wherein some of the plurality of friction drive units can be raised and lowered to alternately engage and disengage with the carrier.

5. The system of claim 3, the electric motor pivotally mounted, such that the wheel can be raised and lowered.

6. The system of claim 3, each of the plurality of friction drive units further comprising: a spring coupled to one end of the electric motor and a mounting platform for the electric motor, adapted for movable vertical positioning of the elastomeric wheel.

7. The system of claim 3, wherein each of the plurality of friction drive units is independently driven.

8. The system of claim X at least one of the plurality of friction drive units further comprising: an independent friction drive encoder, positioned under the carrier while driving the carrier, whereby carrier speed can be regulated.

9. The system of claim 1 , wherein the carrier is self-propelled.

10. The system of claim 1, the carrier comprising: a platen.

11. The system of claim 1, wherein a plurality of containers can be carried simultaneously by the carrier.

12. The system of claim 1 , further comprising: a carrier loading station, adapted for loading the container on the carrier prior to entry into the scanning tunnel; and a carrier unloading station, adapted for unloading the container from the carrier after exit from the scanning tunnel.

13. The system of claim 1 , further comprising: a conveyor system, adapted to convey the carrier through the runnel.

14. The system of claim 13, wherein the conveyor system returns the carrier from the exit to the entrance exterior to the tunnel.

15. The system of claim 14, the conveyor system comprising: a first longitudinal track extending through the scanning tunnel.

16. The system of claim 15, the conveyor system further comprising: a second longitudinal track exterior to the scanning tunnel; a first transverse track between the second longitudinal track and the exit; and a second transverse track between the second longitudinal track and the entrance.

17. The system of claim 16, wherein the second longitudinal track is at a first level, wherein the second transverse track is at a second level, lower than the first level, wherein the first longitudinal track is at a third level, lower than the second transverse track, and wherein the first transverse track is at a fourth level, lower than the first longitudinal track.

18. The system of claim 17, wherein the second level is lower than the first level by a predetermined distance, wherein the third level is lower than the second level by the predetermined distance, and wherein the fourth level is lower than the third level by the predetermined distance.

19. The system of claim 17, the conveyor system further comprising: a plurality of lowerators, comprising: a first lowerator, adapted to lower the carrier from the second longitudinal track to the second transverse track; a second lowerator, adapted to lower the carrier from the second longitudinal track to the first longitudinal track; a third lowerator, adapted to lower the carrier from the first longitudinal track to the first transverse track; and a fourth lowerator, adapted to raise the carrier from the first transverse track to the second longitudinal track.

20. The system of claim 19, each of the plurality of lowerators comprising: a plurality of pistons, each of which has an extended position and a retracted position; and a plurality of platforms, each mounted on one of the plurality of pistons, whereby the plurality of platforms can be raised and lowered.

21. The system of claim 19, the carrier comprising: a wheel for longitudinal movement; and a wheel for transverse movement; and each of the plurality of lowerators comprising: means for raising and lowering a short section of track, alternately engaging the wheel for longitudinal movement and the wheel for transverse movement.

22. The system of claim 1, wherein all of the scanning entrance doors can be open simultaneously.

23. The system of claim 1, wherein all of the scanning exit doors can be open simultaneously.

24. The system of claim 1, wherein all of the scanning exit doors and all of the scanning exit doors can be open simultaneously.

25. The system of claim 1, each of the plurality of scanning entrance doors comprising: two door leaves, wherein the two door leaves are separated from each other in the open position, and wherein the two door leaves abut each other in the closed position.

26. The system of claim 1, wherein each of the plurality of scanning entrance doors and each of the plurality of scanning exit doors are fabricated from steel plate.

27. The system of claim 1 , the scanner comprising a linear accelerator.

28. The system of claim 27, wherein the linear accelerator is a 9MeV linear accelerator.

29. The system of claim 27, the scanner further comprising: a plurality of collimators, adapted to control the shape of an X-ray beam produced by the linear accelerator.

30. The system of claim 1 , the scanner comprising: a linear array system of detector elements; and a digitizing module, adapted to integrate and digitize signals from the linear array system of detector elements.

31. A method, comprising: moving a first carrier carrying a container through a scanning tunnel, the scanning tunnel comprising: a scanning location interior to the tunnel; a first door at an entrance to the tunnel; a second door positioned between the first door and the scanning location; a third door at an exit to the tunnel; and a fourth door positioned between the third door and the scanning location; and irradiating the container at the scanning location only if one of the first door and the second door is in a closed position and only if one of the third door and fourth door is in a closed position.

32. The method of claim 31, moving the first carrier through a scanning tunnel comprising: opening the first door; moving the first carrier through the first door into the tunnel; and closing the first door when the first carrier is entirely within the tunnel,

33. The method of claim 32, moving the first carrier through a scanning tunnel further comprising: opening the second door; moving the first carrier through the second door; and closing the second door when the first carrier is past the second door; and reopening the first door when the second door is closed.

34. The method of claim 31, moving the first carrier through a scanning tunnel comprising: opening the fourth door; moving the first carrier through the fourth door; and closing the fourth door when the first carrier is past the fourth door.

35. The method of claim 34, moving the first carrier through a scanning tunnel further comprising: opening the third door; moving the first carrier out of the tunnel through the third door, and closing the third door when the first carrier is past the third door.

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36. The method of claim 31 , further comprising: loading the container on a first carrier at a loading station; and transversely moving the first carrier from the loading station to the entrance of the scanning tunnel.

37. The method of claim 36, transversely moving the first carrier from the loading station comprising: lowering the first carrier.

38. The method of claim 36, further comprising: transversely moving the first carrier from the exit of the scanning tunnel to an unloading station; and unloading the container from the first carrier at the unloading station.

39. The method of claim 38, transversely moving the first carrier from the unloading station comprising: raising the first carrier.

40. The method of claim 38, further comprising: moving the first carrier from the unloading station to the loading station.

41. The method of claim 31 , further comprising: moving a second carrier into the scanning runnel before the first carrier exits the scanning tunnel.

42. The method of claim 31 , further comprising: moving a second carrier through the first door while irradiating the container at the scanning location.

43. The method of claim 31 , further comprising: moving a second carrier through the third door while irradiating the container at the scanning location.

44. The method of claim 31 , wherein the carrier is self-propelled.

45. The method of claim 31, wherein the carrier is unpowered.

46. The method of claim 45, further comprising: providing motion power to the carrier from a plurality of friction drive units.