Abstract:
A device is provided for testing surfaces of a card for the presence of explosives, drugs or other substances of interest. The device includes a slot for receiving the card. Thin metallic wiper blades are dispose in alignment with the slot and wipe over surfaces of the card as the card is passed through the slot. Thus, substances on the surface of the card are transferred to the wiper blade. The wiper blade then is enclosed and rapidly heated to desorb the material retrieved from the card. The enclosure then is placed in communication with a detector to test for the presence of substances of interest.

Description:
This application claims priority on U.S. Provisional Patent Appl. No. 60/462,559, filed Apr. 10, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for testing for the presence of trace amounts of a contraband material on the surface of an object. 
     2. Description of the Related Art 
     Terrorism risks continue to increase at transportation facilities, government buildings, banks, restaurants, hotels and other locations where there is a significant flow of pedestrian or vehicular traffic. 
     Airlines now routinely screen passengers and employees for explosives. Screening typically is carried out in several stages. For example, all passages are required to pass through a metal detector and all baggage is required to pass through an X-ray apparatus. However, a plastic explosive device could be concealed on a person or in a piece of luggage in a manner that might not be detected by a conventional metal detector or an X-ray apparatus. Even a small amount of a plastic explosive can cause sufficient damage to bring down an aircraft. 
     Most airports now include apparatus for detecting trace amounts of explosives. These devices operate on the principle that small amounts of the explosive materials will be transferred to the body, clothing and luggage of people who had handled the explosive. Some detectors employ small flexible fabric-like traps that can be wiped across a package or piece of luggage. The trap removes residue from the surface of the package or luggage. The trap then is placed in an apparatus, such as an ion trap mobility spectrometer, that tests the residue on the trap for trace amounts of explosive materials. A device of this type is disclosed in U.S. Pat. No. 5,491,337 and is marketed by the GE Ion Track. These devices typically are employed in proximity to the metal detectors, and security personnel will perform screening on some of the passengers based on a random sampling or based on a determination that the passenger has met certain criteria for enhanced screening. 
     The ion trap mobility spectrometer disclosed in U.S. Pat. No. 5,491,337 also can operate in a mode for detecting trace amounts of narcotics. Narcotics are illegal and insidious. Furthermore, it is known that many terrorists organizations fund their terrorism through the lucrative sale of narcotics. 
     The above-described ion trap mobility spectrometer and similar devices have been accepted at airports in view of the notorious efforts of terrorist groups to attack commercial airliners. The above-described detectors have not been accepted widely at other potential targets of terrorism, including train stations, bus terminals, government buildings and the like. The screening of personnel entering train stations, bus depots, government buildings and such by the above-described detection devices would significantly slow the flow of people into and through such buildings and would impose a significant cost penalty on the operators of such facilities. 
     Only a fraction of airline passengers have their baggage checked for trace amounts of explosives or narcotics using the available ion trap mobility spectrometers and similar devices. Efforts to use such devices to check all bags for trace amounts of explosives or narcotics would impose greater time and cost penalties on the airline industry. Additionally, explosive detectors typically are used only on luggage and other parcels. An apparatus of this type would not identify plastic explosives worn by a passenger who had no carry-on luggage. 
     U.S. Pat. No. 6,073,499 discloses a walk-through detector. The detector shown in U.S. Pat. No. 6,073,499 operates under the principle that a boundary layer of air adjacent to a person is heated by the person. This heated air adjacent a person is less dense than air further from the person. Less dense air rises. Accordingly, a thermal plume of air flows up adjacent to a person. Minute particles, including particles of explosives or narcotics, will be entrained in this thermal plume of air and will flow upwardly from a person. The walk-through detector disclosed in U.S. Pat. No. 6,073,499 employs an ion mobility spectrometer or ion trap mobility spectrometer to detect microscopic particles of interest that are likely to be entrained in the thermal plume of air flowing upwardly adjacent to a person who walks through and pauses briefly in the detector. The walk-through detector disclosed in U.S. Pat. No. 6,073,499 is very effective for detecting whether a person is carrying explosives or narcotics and whether the person has recently handled explosives or narcotics. 
     A person who had handled explosives or narcotics is likely to have microscopic residue of the explosive or narcotic materials on his or her fingers, and trace amounts of the explosive or narcotic will be transferred to objects that are handled by the person. For example, it has been assumed that residue of such contraband will be transferred from the fingers to an airline ticket, a boarding pass or an identification card. Hence, the contraband conceivably could be detected on the ticket, pass or card. Efforts have been made to develop a detector that identifies particles of interest on such a card-like object. One such effort used a fabric-like trap, similar to those used to wipe down luggage. The trap was mounted on a heated metal drum that would be rotated against a surface of the card-like object being tested. These efforts have not proved to be commercially successful because of the potential for damage to the ticket or boarding pass due to heat generated by the detector. The trap could be cooled between tests, but such cooling would add significantly to the cycle time. Additionally the fabric traps were found to soil quickly and hence required frequent changing. 
     In view of the above, it is an object of the invention to provide an apparatus for testing the surfaces of substantially planar sheet-like materials for the presence of explosives, drugs or other substances of interest. 
     SUMMARY OF THE INVENTION 
     The subject invention is directed to a detector with means for detecting explosives, narcotics or other substances of interest. The means for detecting preferably is an ion trap mobility spectrometer, such as the detector disclosed in U.S. Pat. No. 5,491,337, the disclosure of which is incorporated herein by reference. A product of this type is marketed by GE Ion Track under the trademark ITEMIZER 3®. The detector also could be an ion mobility spectrometer, such as the type disclosed in U.S. Pat. No. 5,200,614. Other means for detecting trace amounts of explosives, narcotics or other volatile substances can be employed as the detector in the apparatus of the subject invention. 
     The detector includes a sampling apparatus with a housing that has a slot for receiving the edge of a thin planar material. For example, the slot may be dimensioned for slidably receiving a passenger boarding pass, ticket, credit card, driver&#39;s license, employee ID card, passport or the like. For convenience, these thin objects will be referred to collectively as cards. 
     The card sampling apparatus includes at least one wiper disposed in the housing and in proximity to the slot. The wiper is dimensioned and configured for wiping across a surface of the card as the card is slid through the slot. The wiping interaction between the card and the wiper is effective for removing materials that may have been deposited on the card and that may be of interest. Two wipers preferably are disposed and configured to engage opposite surfaces of the card so that material is effectively scraped or wiped from both opposed surfaces of the card. The wipers preferably are flexible and preferably are formed from a thin metallic material. 
     The card sampling apparatus includes a switch and/or sensor that is operative to sense that the card has passed completely through the slot. The switch or sensor is operatively connected to an electromechanical device, such as a solenoid, that closes a chamber around the wiper after the card has passed through the slot. The wiper then is heated sufficiently to vaporize and desorb the sampled material on the wiper. The heating may be achieved by applying a voltage across the wiper and thus causing the wiper to heat to approximately 240° C. An airflow then is generated to transfer the desorbed sampled material from the chamber and into the above-described detecting means for analysis. The passage for generating the airflow preferably is heated for delivering air from the chamber at an elevated temperature. The chamber around the wiper preferably remains closed during the analysis. 
     The apparatus may further include means for displaying the results of the analysis. The displaying means may include a monitor, a printer and/or an audible signal generator. 
     The apparatus operates the solenoid or other electromechanical apparatus for opening the chamber upon completion of the analysis and for placing the apparatus in a condition for a subsequent sampling. 
     The apparatus of the subject invention offers several significant advantages. First, the apparatus does not require the time consuming and labor intensive task of rubbing the filter or trap across a surface to be tested, mounting a fabric-like trap or filter into a detector and then waiting for the test results before the tested luggage or parcel can be returned to the customer. 
     The apparatus also has a desirably short cycle time, preferably in the range of 3-5 seconds. This short cycle time is partly attributable to the use of the thin metallic wiper that can be heated very quickly and then cooled very quickly and partly due to the heating of the air drawn from the chamber. Additionally, the wiper functions to collect and concentrate a sample at the leading edge of the wiper. In contrast, known devices that employ fabric-like traps or filters spread a sample out over the surface. Hence, vaporization of a sample and desorbtion from the edges of the wipers is faster and more complete. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a detector that incorporates the apparatus of the subject invention. 
         FIG. 2  is a schematic view of an ion trap mobility spectrometer of the detector shown in  FIG. 1   
         FIG. 3  is a front elevational view of the card sampling apparatus separated from the detector. 
         FIG. 4  is a side elevational view of the apparatus. 
         FIG. 5  is a rear perspective view of the apparatus. 
         FIG. 6  is an exploded elevational view of the apparatus with the outer housing removed. 
         FIG. 7  is an exploded top plan view of the apparatus shown in  FIG. 6 . 
         FIG. 8  is an elevational view of the portion of the apparatus shown in  FIGS. 6 and 7  in a fully assembled condition and with the enclosure in an open ready-to-use position. 
         FIG. 9  is an elevational view similar to  FIG. 8 , but showing the enclosure in the closed position. 
         FIG. 10  is a perspective view of the stationary shell of the enclosure. 
         FIG. 11  is a perspective view of the movable shell of the enclosure. 
         FIG. 12  is a perspective view of the wiper support. 
         FIG. 13  is a perspective view of the wiper. 
         FIGS. 14 and 14A  are perspective views of the apparatus with the outer housing removed. 
         FIG. 15  is a perspective view similar to  FIG. 14 , but having one enclosure and one wiper removed. 
         FIGS. 16 and 17  are perspective views showing structure for delivering heated air to the ion trap mobility spectrometer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detector according to the invention is identified generally by the numeral  10  in  FIG. 1 . The detector  10  includes an outer housing  11  and a flat panel display monitor  12  such as an LCD monitor. An ion trap mobility spectrometer (ITMS) is disposed within the housing  11  and is illustrated schematically in  FIG. 2 . 
     The ITMS of  FIG. 2  comprises a cylindrical detector  20  having an inlet  22  at one end for receiving sample air of interest borne by a carrier gas which that has been doped with a low concentration vapor (typically a few parts per million) employed as a charge transfer mediator. More particularly, the inlet  22  communicates with a source of sample air of interest  14  and a supply of carrier gas and dopant  16  with flows of gases to the inlet  22  being enabled by a flow generator such as a pump illustrated schematically and identified by the numeral  18  in  FIG. 2 . A heated membrane  19  formed from a microporeous refractory material or from dimethyl silicone is disposed near the inlet  22  and in communication with the source of the sample of air  14  for blocking passage of at least selected constituents of the air and for enabling passage of other constituents of the air, including the constituents of interest. The sample air, carrier gas, and dopant molecules pass through the inlet  22  and are spread by a diffuser  24  into an ionization chamber  26 . The ionization chamber  26  is in the form of a shallow cylinder with a diameter D, length L, and cylindrical wall  28  of a radioactive material, e.g., nickel 63  or tritium, which emits beta particles. Inlet  22  communicates with one end of the ionization chamber  26 . A grid electrode E 1  is provided at the end opposite the inlet  22 , and is normally maintained at the same potential as the inlet end and the walls of the ionization chamber  26 . Thus a largely field-free space is provided in which electrons and ion charges build up and interact with the sample molecules under bombardment by the beta-particles from the radioactive walls. Beyond the ionization chamber  26 , the ionized sample gases pass through open electrode E 1  and into an ion drift region  30  having several field-defining electrodes E 2 -E n . A collector electrode or plate  32  is disposed at the end of the drift region  30  for receiving the ion samples reaching that end. 
     Periodically a field is established across the ionization region  26 , by creating a potential difference between the grid electrode E 1  and the inlet diffuser  24  and radioactive source  28 , for about 0.1-0.2 mS, to sweep the ions through the open grid E 1  into the drift region  30  with the assistance of the switching of the field between electrodes E 1  and E 2 . The ions in the drift region  30  experience a constant electric field, maintained by the annular electrodes E 2 -E n , impelling them along the region and down toward the collector electrode  32 . The electrode  32  detects the arriving charge, and produces signals that are amplified and analyzed through their spectra in the spectrometer. The gases exit through an outlet in the wall next to the electrode  32 . After about 0.2 mS the field across the ionization region  26  is again reduced to zero and the ion population is again allowed to build up in the chamber  26  preparatory to the imposition of the next field. The polarity of the fields is chosen on the basis of whether the detector is operated in a negative or positive ion mode. When detecting explosives, a negative ion mode is usually appropriate, but when detecting narcotic samples positive ion mode is preferred. 
     The card sampling apparatus of the detector  10  is identified generally by the numeral  40  in FIGS.  1  and  3 - 15 . The card sampling apparatus  40  includes a housing  42  with a slot  44 . The slot  44  has a wide top and a narrow intermediate section. The wide top of the slot  44  facilitates the guided entry of a card  46  into the slot  44 . The slot  44  defines a depth sufficient to accommodate a major portion of the width of the card  46 . Arrows  48  are embossed or imprinted prominently on the housing  42  near the slot  44  to indicate the direction for moving the card  46  through the slot  44 . The card  46  is depicted to resemble a credit card, an identification card or a driver&#39;s license. However, the apparatus  40  can be used with any other thin object, such as a passenger ticket, a boarding pass, a theater ticket or the like. 
     The card sampling apparatus  40  includes an enclosure identified generally by the numeral  50  in  FIGS. 6-9 . The enclosure  50  includes a stationary shell  52  and a movable shell  54 . The stationary shell  52  is formed with a linear array of protrusions  53  and with an air passage  55 , as shown in  FIG. 10 . The stationary shell  52  is mounted fixedly in the housing  42 . The movable shell  54  is shown in  FIG. 11 , and is mountable to a solenoid for selective movement toward and away from the stationary shell  52 . More particularly, the movable shell  54  is spaced slightly from the stationary shell  52  in the open position shown in  FIG. 8 , but is engaged sealingly with the stationary shell  52  in the closed condition shown in  FIG. 9 . 
     The card sampling apparatus further includes a wiper support  56  as shown in  FIG. 12 . The wiper support  56  is mounted to the stationary shell  52 . The wiper support  56  includes an elongate recess with a linear array of protrusions  58  substantially identical to the protrusions  53  on the stationary shell  52 . 
     The card sampling apparatus  40  further includes two substantially identical wipers  60 , as shown in  FIG. 13 . A first of the first wipers  60  is mounted to the stationary shell  52  and a second of the wipers  60  is mounted to the wiper support  56 , which in turn is mounted to the stationary shell  52 . Each wiper  60  is formed from a spring tempered electrically conductive material, such as stainless steel sheet or foil, with a thickness of about 0.002-0.004 inch, and preferably about 0.003 inch. Each wiper  60  has a wiping blade  62  which terminates in a substantially linear wiping edge  64 . Thin parallel spring arms  66  extend perpendicularly from the wiping blade  62 . The spring arms  66  are disposed and dimensioned such that the distance between adjacent arms  66  exceeds the width of each arm  66 . Thus, each wiper  60  has a very low thermal mass, and can heat and cool very quickly. Each spring arm  66  has a mounting end  68  remote from the wiping blade  62 . The spring arms  66  at the ends of the wipers  60  have large apertures  70  in the mounting end  68  for receiving screws to mount the respective wiper  60  to the stationary shell  52  or the wiper support  56 . All other spring arms  66  have smaller crenulated apertures  72  for force fit engagement onto the protrusions  53  on the stationary shell  52  or the protrusions  58  on the wiper support  56 . The spring arms  66  each include a bend  74  between the blade  62  and the mounting ends  68 . 
     A first of the wipers  60  is mounted to the stationary shell  52  by passing screws through the large apertures  70  and into threaded holes in stationary shell  52  and by forcing the small crenulated apertures  72  onto the protrusions  53 . A second of the wipers  60  is mounted to the wiper support  56  in a similar manner. The wiper support  56  then is mounted to the stationary shell  52  by screws. As a result, the opposed wipers  60  are juxtaposed so that the wiping edges  64  are parallel and preloaded against one another. In the illustrated embodiment, the wiping blades  62  and adjacent parts of the spring arms  66  of the opposed wipers  60  define a V-shape that points in the direction of movement of the card. 
     The subassembly of the stationary shell  52  the wiper support  56  and the wipers  60  are mounted to a support  76  in the card sampling apparatus  40  so that the abutting edges  64  of the wipers  60  are aligned perpendicular to the direction of movement of the card  46  through the slot  44 . Additionally, V-shape defined by the wipers  60  points in the card insertion direction. The movable shell  54  then is mounted to oppose the stationary shell  52 . In other embodiments, the wipers may define oppositely directed Ω shapes so that the card can be slid in either direction. 
     The card sampling apparatus  40  further includes terminals  78  on the stationary shell  52  and on the wiper support  56 . The terminals  78  are connected to wires (not shown) and are operative for delivering an electric current to the wipers  60  for rapidly heating the wipers  60 . 
     The card sampling apparatus  40  further includes sensors  80  for detecting when a card  46  has passed through the slot  44 . Additionally, the card sampling apparatus  40  also includes an outlet  82  as shown in  FIG. 5 . A stainless steel tube  84  extends between the outlet  82  and the enclosure  50 . The end of the tube  84  remote from the outlet  82  passes into the stationary shell  52  and is capped by a conductive cap  86 , as shown in  FIGS. 16 and 17 . The cap  86  is held in place by a set screw  88 . The tube  84  includes a transverse hole  90  as shown in  FIG. 17 . The hole  90  communicates with the air passage  55  in the stationary shell  52 , and hence lets air flow from the enclosure  50  to the tube  84  and then to the outlet  82  so that the desorbed sample can be delivered between the enclosure  50  and the inlet  22  of the ITMS shown in  FIG. 2 . A terminal  92  is connected to the outlet  82 , and a terminal  94  is connected to the cap  86 . Wires connected to the terminals  92  and  94  apply a voltage that enables the stainless steel tube  84  to be heated to about 160° C. for heating the air flowing between the enclosure  50  and the outlet  82 . Furthermore, the card sampling apparatus  40  includes an electrical connector  96  for connecting the card sampling apparatus  40  to a controller (not shown) mounted in the detector  10  for controlling the closing of the enclosure  50  after passage of the card  46  and for controlling the heating of the wipers  60  when the enclosure  50  is closed. 
     The detector  10  is employed by merely swiping a card  46  through the slot  44  in the card sampling apparatus  40 . The movement of the card  46  through the slot  44  causes the card  46  to move between the wiping edges  64  of the wipers  60 . Hence, the spring arms  66  deflect about the respective bends  74 . The spring tempered metallic material of the wipers  60  will cause the wiping blades  62  to exert a biasing force against opposite side surfaces of the card  46 . The spaces between the spring arms  66  are sufficiently large and the spring arms  66  are sufficiently thin to require only a minor force to pass the card  46  between the biased wiping blades  62  of the wipers  60 . However, the resiliency of the spring metal will exert a sufficient force for keeping the wiping edges  64  in contact with the opposed side surfaces of the card  46 . 
     The sensors  80  will sense when the card  46  has completed passing through the slot  44 . Hence, the signal generated by the sensors  80  will cause the controller to move the movable shell  54  toward the stationary shell  52  and into the closed position around the wipers  60 , as shown in  FIG. 9 . Current then will be applied to the terminals  78  for heating the wipers  60  to a temperature of approximately 240° C. This heating can be carried out very quickly in view of the relatively small thickness (e.g. 0.003 inch) of the wipers  60 . Additionally the spaces between the spring arms  66  reduce the thermal mass of metal material that must be heated, and hence contribute to very rapid heating of the wipers  60 . The heating vaporizes and desorbs material collected on the wiping edges  64  of the wipers  60 . Simultaneously, the ITMS illustrated in  FIG. 2  is actuated to draw air and potential vaporized particles of interest through the air passage  55  and into the inlet  22 , both of which are heated. The ITMS then is operated in the manner described above and in U.S. Pat. No. 5,491,337 to identify any minute amounts of substances of interest that will have been wiped from the card  46  by the wipers  60 . The results of the analysis will be displayed on the monitor  12 . The cycle time between the initial swiping of the card  46  through the slot  44  to the display of the test results on the monitor  12  is likely to be approximately 3-4 seconds. 
     The low thermal mass of the wipers  62  and  64  ensures that the wipers will cool quickly after termination of the electric current and the opening of the enclosure  50 . Hence the wipers will be at a sufficiently low temperature to prevent damage to a card  46  during a subsequent cycle. 
     The rapid cycle time and high efficiency of the detector  10  is partly attributable to the concentration of sample material on the edges  64  of the wipers  60 . More particularly, conventional detectors employ a soft fabric-like filter or trap material, and samples are collected across a relatively large surface area of the material. Subsequent desorbtion or vaporization of the sample is slower and less complete. In contrast, the concentration of the samples on the thin edges  64  of the wiper  60  is well suited to rapid desorbtion/vaporization and achieves a very high efficiency and accuracy. 
     The invention has been described with respect to a preferred embodiment. However, variations will be apparent to a person skilled in the art after having read the subject disclosure. For example, the invention has been depicted with respect to a stand-alone dedicated apparatus for detecting the presence of substances of interest on the card. However, the apparatus can be incorporated into a multifunction device. For example, the apparatus can be incorporated into an e-ticket machine common at airport terminals or into a boarding pass scanning machine, common at many boarding gates. Thus, any apparatus that receives and processes a card for some other purpose can be adapted to include the apparatus of the subject invention. Additionally, the apparatus has been described as being used with an ion trap mobility spectrometer. However, other devices are known for identifying particular substances of interest, and any such devices can be employed with the subject invention.