Abstract
The apparatus disclosed herein pertains to the detection of trace explosives or narcotics detection. The apparatus comprises the front-end particle dislodge and sample intake portion of a chemical trace detection system utilizing aerodynamic flow as a transport mechanism whereby compounds indicative of explosives or narcotics contamination are liberated from target surfaces of foot or footwear and then transported by air flow to a sample accumulation feature for chemical analysis. The apparatus is intended for inclusion with additional components, such as an efficient pre-concentrator, a thermal desorption unit, and a chemical analyzer/detector to achieve a complete trace detection system.
Claims
1. An apparatus for collection of particulate matter from footwear, comprising: a contoured channel suitable for receiving airflow passed over target footwear and conveying such airflow to a sample accumulation feature; a pressurized gas source to provide gas that is pressurized to gas delivery vehicles that are positioned about a location where the footwear is to be placed and oriented so high velocity airflow from the vehicles impacts target footwear during operation to dislodge particulate matter embedded in or on the target footwear; an air moving device that draws airflow that passed by the target footwear into the contoured channel so airflow into the contoured channel is maintained at or above 400 liters per second at ambient temperature during procurement of sample by the sample accumulation feature that collects entrained particles liberated from the target footwear, the contoured channel and gas delivery vehicles being configured to maintain consistent particle release from the target footwear and minimize particle spillage from the contoured channel; where the channel and the gas delivery vehicles are configured to permit reorientation to sample footwear having an a atypical dimension.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The features of the invention embodiment are described, with reference to accompanying drawings.
(2) FIG. 1 illustrates the invention from above with orientation in the X-Y plane.
(3) FIG. 2 shows a magnified view of the left air jet nozzle orientation in the X-Y plane.
(4) FIG. 3 illustrates the invention from an orientation in the Z-Y plane.
(5) FIG. 4 shows a magnified view of the left air jet nozzle orientation in the Z-Y plane.
(6) FIG. 5 shows the orientation of the far right air jet nozzle and air knife, above the tongue of footwear in the Z-Y plane.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT DRAWINGS
(7) Referring first to FIG. 1, which has a view that is oriented in the X-Y plane, the apparatus of the present invention includes a main sampling structure comprised of a converging channel 3 for intake of sample containing air, four EXAIR super air nozzle (Model no. 1100)-air jets 9, 10, 11, 12, three air jet mounts 4, 5, 6 extending outward from the intake portion of the channel 3a, two EXAIR super air knife (Model no. 110003) 7, 8 and a Chicago Blower Corp. (serial no. 254919-2, part no. 7042535) 2-horsepower centrifugal blower as a primary air moving unit 14. The air sample intake channel 3 is contoured in a converging shape to prevent air recirculation patterns from forming within corners. The central air jet mount 5 has a left central air jet nozzle 9 and a right central air jet nozzle 10 attached at the portion of the mount opposite the intake portion of the channel 3a. The left air jet mount 4 has one air jet nozzle 11 attached at the portion of the mount opposite the intake portion of the channel 3a and the right air jet mount 6 has one air jet nozzle 12 attached to the mount at the portion of the mount opposite the intake portion of the channel 3a. The converging channel 3 contains a sample accumulation feature 13. The collection device 13 is the portion of the invention where sample is collected for testing, this portion may take the form of a pre-concentrator or any means utilized to isolate the sample for analysis. The sample accumulation feature 13 is incorporated within the channel 3 but may in an alternative embodiment be linked to the channel 3 through a bypass mechanism which does not allow air to continuously flow through the sample accumulation feature 13 while the primary air mover 14 is in operation. Air is drawn through the collection device by a primary air mover 14 operating at an ideal flow rate of above 600 liters per second. The flow rate of the primary air mover 14 is an essential element of this invention. Laser light sheet flow visualization experiments using theatrical fog and talc powder have demonstrated that spillage is minimized when the air mover 14 is operating at the optimal flow rate of 620 liters per second through a rectangular channel intake area with a dimensional range from 30-40 inches in width to 4-8 inches in height. Optimal dimensions for such rectangular channel intake area are 34 inches wide by 6.5 inches high 3a. If the flow rate is too low, excess air introduced by the jets 9, 10, 11, 12, and air knives 7a, 8a can overload the system and spill sample laden air from the intake portion of the channel 3a. This will reduce the effectiveness of sampling and particle collection. At a flow rate of 620 liters per second, all particles that are liberated from the footwear surfaces are transported directly through the intake portion of the channel 3a. Outlines of footwear patterns 15 are located beneath the left air knife 7a and right air knife 8b to indicate the location that a subject must stand for sampling. In a field environment, markers such as the shoe sole patterns shown in the figure should be used to position the targeted areas of footwear in a consistent location. The addition of such markers will also ensure distance between targeted footwear surfaces and the air jet nozzles or air knives remains approximately same through sampling of successive subjects.
(8) FIG. 2 shows a magnified view of the area surrounding placement of the left article of footwear with the air jet nozzle orientation in the X-Y plane. Optimal left air jet nozzle 11 orientation is a fixed 45 degrees 16a in the X,Y, Z space, but may be directed through any angle that ensures that air is vectored towards the rear surfaces of the footwear. The left central air jet nozzle is a fixed 45 degrees 16b in the X,Y, Z space, but may be directed through any angle that ensures that air is vectored towards the rear surfaces of the footwear. The distance from the left air jet nozzle exit 11a or left center air jet nozzle exit 9a to the footwear surface should optimally be in the range of 5 to 7 inches. The air knife 7 is located centrally above the left side object of footwear targeted. The distance from the exit of the air knife 7a to the surface of the footwear should optimally be in the range of 2 to 7 inches.
(9) FIG. 3 shows the invention viewed in the Z-Y plane. Outlines of the back of a subject's footwear 17a and legs 17 are shown for completion. A left air jet nozzle 11 is directed through X,Y,Z space, a left central air jet nozzle 9 is directed through the X,Y, Z space, a right central air jet nozzle 10 is directed in the X,Y,Z plane and a right air jet nozzle 12 is directed in the X,Y,Z space. The optimal firing sequence of all air jets is from a location 5-7 inches from the target (shoe surface) with distance from the exit of the air knives 7a, 8a, to the surface of the footwear optimally in the range of 2 to 7 inches. All air jets and air knives release compressed atmospheric gas at 80 psi backpressure, with an air mover flow rate of 620 lps and channel intake 3a area of 18.4 square feet; through a release sequence comprising 1) air knives, 2) central jets, then 3) outside jets. With an on-time of 50 ms, off-time of 200 ms, and 200 ms between each release of pressurized gas. Practical limitations in a field deployment environment will likely limit overall sampling time, to between three and five repetitions of the pressurized gas air release sequence. Optimal repetition was determined to be least three times, with a cumulative time of pressurized gas release equaling 6.75 seconds. Particle release efficiency measurements using fluorescent polymer microspheres embedded in sebaceous material have demonstrated the invention as having the ability to consistently remove approximately 20% of known compound from a targeted surface through particle liberation attributed to the four air jets, with each air knife having the ability to liberate a 10% average of known compound from their respective target surfaces.
(10) FIG. 4 shows a magnified view of the left air jet nozzle orientation on the rear left side of the invention in the Z-Y plane. The optimal left air jet nozzle 11 orientation is 45 degrees within the X, Y,Z space and the optimal left central air jet nozzle 9 orientation is 45 degrees within the X,Y,Z space. The left air jet nozzle 11 may be directed within a range of angles through the X,Y,Z and the left central air jet nozzle may be directed within a range of angles through the X,Y,Z space to ensure that the airflow from the jet is vectored towards the rear surface of the footwear. Reorientation may become necessary due to an abnormal variance in the foot or footwear size of the target.
(11) FIG. 5 shows a right side-view of the invention in the Z-X plane. Outlines of the side of a subject's shoe 17a and leg 17 are shown for completion. The optimal right air jet nozzle 12 orientation is 45 degrees in the X,Y,Z space 19, but may be directed in any angle that ensures that air flow is vectored towards the rear surface of the footwear. The placement of the right air knife 8 above the tongue of the footwear is shown whereby the right air knife 8 is adjacent to the intake portion of the channel 3a.
(12) In an embodiment, the apparatus further includes a detector that is configured to generate a signal responsive to the footwear being position so the airflow is optimized relative to the mouth and gas delivery vehicles.
