DETECTION SYSTEM
Field of the invention
The present invention relates to a detection system for screening packages, such as personal baggage, packets, parcels, letters and other type of articles intended to carry or contain something. Specifically, the present invention is related to a high-speed detection system intended to read, detect or save a specific content(s) measure or more from a sample of a package, surface, person or animal, clothing or other form of material. One possible specific use according to the present invention is also for detecting a specific content(s) measure from a sample of a package and alarming if the same contains dangerous matter or material, such as explosives, chemicals, narcotics, etc.
Technical Background
Detection systems exist today. For instance, in US 201 1 10186436 there is disclosed devices, apparatus and methods for non-contact pneumatic sampling and sampling of surfaces, persons, articles of clothing, buildings, furnishings, vehicles, baggage, packages, mail, and the like, for
contaminating aerosols indicative of a hazard or a benefit, where the contaminating aerosols are chemical, radiological, biological, toxic, or infectious in character.
Furthermore, in US4987767 there is discolsed an explosive detection screening system used for the detection of explosives and other controlled substances such as drugs or narcotics. The screening system detects the vapor and/or particulate emissions from the aforementioned substances and reports that they are present on an individual or object and the concentration of each substance detected. The screening system comprises a sampling chamber for the collection of the vapor and/or particulate emissions, a concentration and analyzing system for the purification of the collected vapor and/or particulate emissions and subsequent detailed chemical analysis of the emissions, and a control and data processing system for the control of the overall system. Moreover, in EP0169057 there is disclosed a method of detecting contraband substances in freight cargo containers in which the container is agitated to disturb particulates therein, and air containing such particulates is then sampled and the particulates collected. The collected particulates include naturally occurring particulates which have adsorbed vapors of the contraband substance during the entire time that the container has been closed, and also include particulates of the contraband substance itself. The collected particulates are heated to drive off vapors indicative of the contraband substance and the vapors are analyzed in a mass analyzer.
The present invention is directed to providing an improved detection system which provides inter alia a high measurement reliability and as such a high level of control, also when a relatively high belt speed is used.
Summary of the invention
The stated purpose above is achieved by a device intended for screening packages, said device comprising
- a unit for exposing a package to compression and thereby liberating an air sample from the package;
- a collecting unit for collecting the air sample; and
- a sensor unit for reading, detecting, alarming and/or saving a specific content(s) measure of the air sample, and wherein the sensor unit comprises one or more tin oxide sensors, polymer sensors, sensors directed to gas chromatography, mass spectrometry, ion spectrometry, ion trap spectrometry or combinations thereof.
There are several advantages of the present invention. First of all, the system is a system which is easy to place as a plug-in to any conventional high-speed conveyor belt. The system according to the present invention may have a design like a U shaped frame which is placed over and around a transportation band. The conveyor belt, roller(s) or other form of transporting unit is transporting or moving a package with speeds of up to 2 m/s, typically from 0.5 to 1 .0 m/s. It may further be said that that the system according to the present invention typically does not comprise the conveyor belt as such, even if this may be the case. Instead, the transporting unit may be seen as the environment in which the present invention should be used. The system is intended to be able to be used for many different types of high-speed conveyor belts, both as a permanent and temporary solution.
Furthermore, it should also be mentioned that the collecting unit in fact may be a unit which comprises the sensor unit. According to one specific embodiment, the collecting unit comprises hoses. Such hoses may e.g. be arranged to be attached to an over-bar, and then hang down from the over- bar and suck up the air around the package which has just been compressed. According to another embodiment of the present invention, the collecting unit is a funnel. This funnel may be arranged to be positioned below or in connection with the transporting unit.
In US 2004/0045342 there is disclosed a system for detecting contaminants in or on objects, comprising a movably mounted container for holding objects and having a plurality of perforations and an entrance opening through which objects may be placed into said container; a housing enclosing said container and forming a barrier to ambient air and having a sealable opening for inserting and removing objects from said container; means for moving said container within the housing to move objects therein for emitting particles which are in or on such object; means providing an air stream for moving air through said housing and container to entrain any emitted particles into the air stream; and a sensor for sensing contaminants in the air stream and providing a signal when a contaminant is sensed. The sensors disclosed in US 2004/0045342 are aerosol or particle sensors. None of the sensors possible to be included in the sensor unit according to the present invention are disclosed or hinted in US 2004/0045342.
Furthermore, in US 2004/0020266 there is disclosed a system for detecting contaminated objects comprising a closed chamber defining a cavity, said chamber having a sealable inlet to accept at least one object into said cavity; a pinching subsystem operably connected to said cavity for receiving said at least one object, said pinching subsystem capable of compressing said at least one object and releasing particles associated with said at least one object into air within said cavity to form cavity air; a cavity air processing subsystem operably connected to said cavity for receiving said cavity air, said cavity air processing subsystem capable of subjecting said cavity air to at least one test; and a means for providing an indication of results obtained from said at least one test, wherein based upon said indication, a decision can be made with respect to further handling of said at least one object. Also in this case, the sensors disclosed in US 2004/0020266 are aerosol or particle sensors, in fact the same type as discussed in
US 2004/0045342. None of the sensors possible to be included in the sensor unit according to the present invention are disclosed or hinted in
US 2004/0020266.
Specific embodiments of the invention
Below, some specific embodiments of the present invention are disclosed.
According to one embodiment, the unit for exposing the package to compression is a unit directed to a stroking, vibrating or pressing operation on the package. As understood from above, this compression may be exerted by different means. To vibrate the package by use of one or more vibrators is one alternative according to the present invention. According to yet another embodiment, the system also comprises some form of pressuring device, which pressuring device e.g. may press on two opposite sides of a package to compress the package and evacuate air from the package in about the same way as with a vibration.
When vibrator(s) are used according to the present invention, both the type and their frequency range may vary. One possible type of interest is eccentric vibrators. Also several vibrators operating within different frequency ranges may be used. According to one specific embodiment of the present invention, the unit for exposing the package to compression is a unit operating with vibration in the range of 5-15 Hz. According to yet another specific embodiment, the unit for exposing the package to compression is a unit operating with vibration in the range of 8-12 Hz. This range may be of particular interest for certain technical applications of the present invention. Smaller and larger packages have different resonance frequency. According to the present invention, one, two or several vibrators may be used to cover packages of different size. Furthermore, also other devices may be used to excite with other wave forms containing the frequency ranges according to above. This may also be a combination according to the present invention to ensure to cover all kinds of package sizes.
Not only the actual frequencies may vary, but also the actual way of compressing may vary in terms amplitude / length of stroke and how to stroke. Different frequencies may also imply different modes of stroking.
Regarding length of stroke this is typically from 0.05 mm up to max about 1 cm, where the latter level should be considered very high. According to one specific embodiment of the present invention, the length of stroke is chosen in the range of 0.5 mm - 3 mm.
According to yet another specific embodiment of the present invention, the unit for exposing the package to compression is a unit providing a calibrated drop of the package. In this case, the system may comprise a belt for receiving and transporting the package, which belt then provides a drop of the package onto the regular conveyor belt. The actual fall may be from 1 to 20 cm, such as 5-10 cm. Also this provides a compression to the package. Another alternative according to the present invention is to use a device, such as a sandbag or the like, which is dropped like a weight onto the package to create the compression. The weight is typically in the range of from 1 to 3 kg. A sandbag according to the present invention may have large advantages if the package or other item intended to be compressed is uneven. In fact, a sandbag functions on all different types of shapes. This is not the case when using rollers, such as in US 2004/0020266.
The present invention facilitates the handling of any type of package shape, which is a great advantage. Furthermore, a sandbag may provide a compressing effect also on sides of a package not being the top side of the package. This is also why uneven packages may be analyzed so effectively in the system according to the present invention when being compared with other systems. The sandbag may have a cloth wound up on a roller. The height of the package being analyzed may be measured before the detection. The software or program used may then alter the final position for the sandbag to be dropped to, based on the height of the package. It may further be said that the hoses, which may be part of the collecting unit, should be positioned close to the compression position for a sandbag which has been dropped onto a package.
Also these other types of means for compression according to the present invention is followed by a liberation / evacuation of an air sample, which then is collected and handled by the sensor unit.
The system according to the present invention may be complemented with other techniques or add-ons. According to one specific embodiment, the collecting unit is provided with positive or negative voltage to attract ions. The hoses or the funnel of the collecting unit mentioned above may be provided with high voltage, both positive and negative, to attract ions. The voltage of the electrodes may be in the range of 0-10 kV, such as 3-7 kV, e.g. around 5 kV.
Moreover, according to yet another embodiment of the present invention, the collecting unit is provided with heating capability to heat up particles. This may be of interest to evaporate molecules with a low vapour pressure at room (ambient) temperature. The temperature provided by the heating unit providing the heating capability is normally in the range of from 100 to 500°C, such as typically from 150 to 250°C, according to the present invention.
As understood from above, also the sensor unit according to the present invention may comprise different possible components based on different technique. According to one specific embodiment of the present invention, the sensor unit comprises one or more tin oxide sensors, polymer sensors, sensors directed to gas chromatography, ion spectrometry, or combinations thereof. According to one embodiment, the sensor unit of the present invention comprises several sensors from the ones disclosed above and where at least some of them are of different type. To use different techniques may have the advantage that different interest areas may be possible to detect.
Moreover, according to one specific embodiment there are humidity and/or temperature sensors arranged in the system. This is in view of the fact that the detection data has a relationship with these parameters. These humidity and/or temperature sensors are in such a case arranged inside of the air chamber in proximity to the sensors. By measuring these parameters the system may be calibrated so that the detection data is adjusted based on these parameters. It is of course important to ensure that the response time constant for these sensors correlate with the gas detection sensor's temperature and humidity response time constant so there is correlation between sets of data points.
According to one specific embodiment of the present invention, the sensor unit comprises one or more tin oxide sensors which are heated by heating elements and cooled by flowing air. Also in this case other sensor types may be comprised in addition. Within the application of the present invention, the tin oxide sensors may operate at a constant heating of a heating element of the sensor. The sensors may at the same time be cooled by flowing air. As such, the sampling time may be decreased considerably when compared to a cycling approach when the heating element is turned on and off. When using such an approach according to the present invention it is possible to get down to measuring cycle times of about 1 second instead of approx. 1 minute which is the normal case when using the other approach and turning on and off the heating element of the tin oxide sensor.
Furthermore, the air streams around the tin oxide sensor may also have a direct effect on the measurement possibilities. According to one embodiment of the present invention, the air stream(s) is directed straightly towards the sensor surface where there is an opening directly to the tin oxide granulate. As such, the cooling may be more effective, and this can affect the measuring cycles. Therefore, a cooling air stream directly "into" the sensor is preferred. Moreover, according to yet another embodiment of the present invention, the sensor unit comprises several tin oxide sensors operating at different temperature ranges. By using different temperature ranges for the tin oxides sensors the actual temperature range covered by the measurement may be increased.
Moreover, the system of the present invention may also be
complemented by a ventilator device so that the system may be quickly ventilated. Therefore, according to one embodiment, the device also comprises a valve and a subsequent ventilator.
According to yet another specific embodiment of the present invention, the device comprises a suction system intended for sucking air into the sensor unit / sensor compartment. Furthermore, according to one
embodiment the suction system comprises a fan and a valve. For instance, the suction system used to suck air into and through the sensor compartment can be made up of a traditional radial or axial fan combined with a high speed valve to switch the airflow on and off. When an inhalation is required the valve opens and the under pressure built up by the fan sucks air in through the sensor unit / compartment. The airflow cools down the sensors and the valve is closed when enough air has been sucked in through the senor
compartment. The sensor substance sampling cycle starts when the inhalation phase commences and stops typically a half second up to 30 seconds after.
This is the core of a basic air handling system according to one embodiment of the presnt invention. Even if this works well it has a number of intrinsic limitations. With traditional types of fans as suctions devices there are always a certain amount of noise in the air flow. The problematic noise is predominantly present at very low frequencies below 10 Hz and the amount of noise has a direct influence on sensor sensitivity. If the airflow is uneven because of noise it will not cool the sensors in a constant fashion creating a stochastic or noisy sensor response signal. Small amounts of substances creates small detection signals form the sensors and they will be drowned in the noise created by uneven air flow. If the unevenness in the air flow is reduced the sensitivity of the system goes up. Based on the above, according to one specific embodiment of the present invention, the device comprises a noise reducer between the suction system and the sensor unit.
As one example, it is possible to reduce the amount of noise by adding a common Helmholtz resonance based noise filter tuned to a very low frequency, typically below 0.5 Hz, between the fan and the sensor
compartment. The filter improves the sensitivity of the system but significant noise still remains.
Yet a better way is to use a bellow as a suction device. Therefore, according to one embodiment, the suction system is a bellow. The bellow allows more precise control of the amount of air sucked through the sensor unit / compartment as well as provides a significant lower noise level. It improves the sensitivity through reduced noise levels and provides the additional benefit of reducing the sensitivity of the whole suctions system to variations in flow resistance. The bellow creates a very high under pressure if the flow is obstructed compared to a fan that has not at all the same steep flow versus pressure relation as the bellow. The bellow improves the stability of the system and sensor operation.
An air handling system comprised of a fan or bellow has another inherent problem, the sensors are only cooled down when a sample of air is sucked into the sensor compartment. If the system does not sample then the sensors heat up. Since it is mandatory to keep the sensors at a constant temperature the only solution is to have the system operating continuously taking sample after sample. This if of course possible but is not very convenient since as an example parcels on a conveyor belt will pass the sensors at random intervals and it is not likely that they will always coincide with the continuous sampling period. Another air suction system in parallel with the fan or bellow can solve this problem however. Based on this, according to one specific embodiment of the present invention, the device comprises parallel suction systems intended for sucking air into the sensor unit. If a relatively small fan continuously sucks a small amount of air through the system at times when no substance sampling cycle is taking place the flow can be adjusted to provide a cooling down effect of the sensors equaling the cooling down effect created by a sampling cycle. Then the system can always be ready to perform a sampling cycle whenever a parcel arrives at the sensors on the conveyor or any another type of external event requires that a sampling cycle takes place.
To further improve temperature stability of the system, especially important if there are substantial environmental temperature fluctuations, then it is possible to pre-heat the air flowing into the sensor unit / compartment. Therefore, according to one embodiment of the present invention, air flowing into the sensor unit for cooling the same is pre-heated. A pre-heating before the air enters into the sensor unit / compartment to a temperature between 25-100°C is conceivable with a preferable range being 40-60°C.