Patent Application
20070267351
The present invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in order to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention.
In this regard, no attempt is made to show structural details in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Identical structures, elements or parts which appear in more than one figure are preferably labeled with a same or similar number in all the figures in which they appear. In the drawings:
The present invention relates to moving particles inside articles and, in particular, to a system and corresponding method that employs acoustic waves to move particles inside articles. The present technology is greatly useful for applications that require noninvasive methods to effect the movement of particles within hermetically sealed articles that may contain materials such as solids, fluids, and/or gases. In addition, the present technology is useful for collecting and/or extracting and/or arranging particles within non-hermetically sealed and hermetically sealed articles.
The present technology may be used as a system and a method for moving and collecting particles. The preferred embodiments are discussed in detail below. It is to be understood that the present invention is not limited in its application by the details of the order or sequence of steps of operation or implementation of the method and/or the details of construction, arrangement, and composition of the components of the system set forth in the following description, drawings or examples. While specific steps, configurations and arrangements are discussed, it is to be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other steps, embodiments, configurations and arrangements can be used without departing from the spirit and scope of the present invention.
The present invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology, terminology and notation employed herein are for the purpose of description and should not be regarded as limiting.
The present invention is preferably operated using low frequency acoustic transducers, e.g., subwoofers, but it is to be understood that in the case where there is no barrier between the wave source and the article interior, the present invention may be operated with sound waves of about 90 Hz or more, so long as the sound wave frequency is suitable for the article under investigation/maintenance. Moreover, it is to be understood that when the acoustic source is part of the article walls, virtually any frequency may be used.
In one embodiment, a sound source, e.g. a subwoofer, reproduces the lower end of the audio spectrum to create air fluid flows both inside and around at least one article. Subsequently, some particles loosen and/or are entrained, causing them to move within the article. Similarly, it should be possible to preferentially cause such flow to predictably move particles in almost any desired trajectory.
In one embodiment, the article may contain a suspected material and the fluid flows within the article cause all or a portion of the suspected material to flow, for example to or outside the periphery of the article.
In one embodiment, the aforementioned article has at least one compartment. The at least one compartment may feature a “hermetically sealed” state, and a “non-hermetically sealed” state.
One embodiment uses low frequency “acoustophoresis”. Low frequency sound waves are able to penetrate an article more easily than higher frequencies, since higher frequencies are increasingly damped by the article walls, and optionally an outer container. The present technology may be used in combination with other particle dispersion methods such as heating, shaking, and/or radiating. In a preferred embodiment the distortion of the sound wave as it passes through the article is slight. Hence, the article represents only a small attenuation element in the surrounding field. The acoustic field is of great advantage since it exerts forces on the items within the article. A wide range of forces and force directions are possible. Moreover, since the acoustic frequency can be selected to be below the range of human hearing, strong sound pressure levels may be used without creating a noise hazard. It is to be understood that the present technology may transmit sound wave frequencies in a variety of ranges, such as, but not limited to, frequencies below 20 Hz, frequencies in the range of 20 Hz to 20 KHz, and frequencies above 20 KHz.
It is also understood that the acoustic energy may be generated by one or more transducers, with or without a resonator, and indeed the transducer system may comprise an array of transducers, for example a selectively disposed spatial array which is adapted to permit control over the spatial acoustic fields and forces imposed on the article. The control system therefore may comprise a digital signal processor for defining a desired spatial and temporal acoustic field pattern, a spatial array of electro-acoustic transducers, and optionally an acoustic feedback system, e.g., one or more microphones (acoustic-electric transducers) and optionally a controllable and/or tunable resonator chamber.
Therefore, in accordance with this embodiment, the peak acoustic power at a selected spatial position, typically at the wall or, or within, the article may be significantly higher than the peak acoustic power available from any one transducer, and the characteristics of the acoustic field may be finely controlled. For example, it may be desired to induce a macroscopic movement in a wall of an article having a compliant wall, to induce air flows therein. Thus, the external acoustic field is defined by the processor to induce a pressure differential across the wall of the article. Since the article has a volume, the acoustic transducer array may also optimize the acoustic fields for the various walls of the article, to induce the desired flow pattern. Likewise, the wall of the article may be transparent or translucent to acoustic waves, permitting the acoustic transducer(s) to define the acoustic field within the article, directly. In that case, the acoustic field within a chamber holding the article may be defined. More commonly, the article will interact with the acoustic field, with a part of the acoustic energy being transduced to a wall or other structures of the article, part passing though any walls, and part being absorbed. Accordingly, the acoustic frequencies, spatial acoustic field characteristics, mass air flows, may all be optimized based on various criteria. The range of these criteria may be a single global optimum, a classified optimum (i.e., where the article is classified into one of a limited number of classes, and a treatment applied with is optimized for that class), a model-based optimum (i.e., where a “type” and parameters of the article are determined, and these are applied to a model of the “type” to determine the treatment), a feedback-based optimum (i.e., where a sensor determines an effect of the treatment, and the acoustic fields modified seeking to achieve a desired effect or condition), or the like.
In some cases, it may be desired to efficiently deposit energy in certain parts of the article; for example, it is desired to transmit energy though a wall of the article, and then absorb or transducer that energy therein. This can be accomplished in a number of ways. One way is to exploit non-linear properties of materials which, for example, can self-modulate or inter-modulate a plurality of waves. Thus, as the waves enter the article, harmonics or inter-modulation products are generated, which can have vastly different acoustic absorption properties in the surrounding materials.
The acoustic field need not be static or have nodal planes with static locations, and in fact, the acoustic field may change dynamically, to scan the article or induce a net movement thorough or out of the article.
While the technology is generally discussed with respect to the sampling of particle within articles, it should also be understood that the technology may also be used to emplace particulates within an article or object. For example, it maybe desirable to disperse an insecticide or biocide within an article; therefore, the technology may be used to bring external particles within the object. Likewise, it may be desirable to tag an article and its contents with a taggant.
In a preferred embodiment, particles are extracted from articles when examining for contraband substances. The examination of articles for contraband substances, such as, but not limited to, explosive materials, narcotics, and biological agents, may include analyzing trace particles collected from the article. The acoustic waves may be used not only to move particles within an article, but also after they are transported out of the article. Analyzing trace particles is well known in the art of security screening services.
The present technology discloses a device and corresponding method for collecting particles from within articles, and optionally from within (hermitically or non-hermetically) sealed articles. It is to be understood that in order to collect particles from a hermetically sealed article, the article has to be opened. This may be in contrast with collecting particles from a non-hermetically sealed article, which may be opened or may remain closed in order to collect particles from within it.
Various trace detection systems require that articles be non-hermetically sealed and usually opened in order to collect particles from within the articles. This results in article delivery delays and long lines at transportation embarkation sites as carry bags and other articles must be laboriously examined for contraband. It is a great advantage of the present invention to be able to collect trace particles from within nonhermetically sealed articles without having to open them.
In another embodiment, the sound sources of the present invention enhance various types of inspection systems, where articles are opened for inspection, such as methods where the interior surface must be “swabbed” and the swab is subsequently placed in a trace analyzer. According to this embodiment, using the sound waves effectively disperses particles throughout the article so that the probability of the swab to pick up any searched for particles is significantly increased.
Moreover, means of particle extraction from articles using “breathing” techniques, where pressurized air enters an article and, upon leaving the article, carries with it particles from within the article are known. This method works well when the particles are subject to the forces exerted by the pressurized air, and the air dilution of the sample is acceptable. For example, if particles are stuck to a surface or exist on the lea side of objects within the article, they may remain out of touch of the airflow and hence not be removed from the article.
Another preferred embodiment uses low frequency sound waves to extract particles from the article using the “breathing” method described above.
Low frequency acoustic waves may penetrate the article, causing air currents to induce particle motion. The air currents can lift particles that are stuck to their surface and otherwise move particles to locations where they are susceptible to being entrained for extraction by “breathing” air currents.
Creating air currents increases the probability that particles within the articles dislodge and subsequently become more susceptible to motion caused by air movement inside the inspected luggage. This improves the detection probability of a particle collection system, since the particles are more distributed across the article interior (i.e. near article openings) and are more likely to be extracted during a breathing cycle. The timing of the generation of low frequency waves can therefore be in accordance with other activities of the trace collection system, so as to improve system performance. Advantageously, the control system for the acoustic process may be integrated or communicate with the control system for a particle extraction and analyzing system, in order to coordinate functions sand pass information.
Using sub-audible acoustic frequency sound waves is advantageous since they are less detectable by the human ear, and do not present a public health hazard. The frequency of the sound pressure levels (for example, standing waves) can be tuned to be undetectable by animals in the proximity of the trace collection system. The at least one sound source may be located almost anywhere around the inspected articles. As is known in the art, sound sources, including subwoofers, may be made to be directional. Using a directional sound source further reinforces the aforementioned significant particular aspect of novelty and inventiveness of the present invention, relating to the ability to locate the sound sources almost anywhere around the inspected article.
Steps, components, operation, and implementation of using acoustic waves for moving particles inside articles, according to the present invention, are better understood with reference to the following description and accompanying drawings.
Referring to
In another embodiment, acoustic resonators that produce high intensity sound waves control the trajectory of particles, i.e. using moving sound pressure levels to move particles inside an article. In an alternative or additional phrasing, this embodiment discloses the ability to concentrate particles in the vicinity of a predefined three-dimensional location. As known, the generation of standing sound waves causes particles to concentrate in the wave's trough. This is due to a force created by unequal sound pressure levels (SPL) across the standing wave that pushes the particle toward the low pressure point. The term “moving sound pressure levels” refers to moving standing waves.
In one embodiment, a sound source, e.g. a subwoofer, which reproduces the lower end of the audio spectrum, is used to create moving sound pressure levels for moving particles both inside and around the inspected articles. Moving sound pressure levels are utilized to dislodge particles, augment particle trajectory, and move particles in a predefined direction, e.g. towards the location of particle inhaling components of the particle collection mechanism. This improves the reliability of the collection process since more particles are extracted from the inspected articles, collected and analyzed.
Using moving sound pressure levels for moving particles inside the luggage can improve on other vibrating mechanisms that instigate the movement of particles in the inspected articles. The timing of the generation of moving sound pressure levels can be in accordance with other activities of the trace collection system so as to improve system performance.
In one embodiment, the inspected article is pressurized so air gets into it by applying the following two steps: (1) applying long waves that move particles from the middle of the inspected article toward article openings. (2) “breathing” in order to take the particles out of the article. It should be noted that there may be circumstances in which the breathing is not necessary if the particles can be removed from the article by using the first step only.
As described above, breathing refers to pressurizing the article within a flexible enclosure and then depressurizing the article. When pressurizing the article, air flows into the article, referred to as inhaling. When depressurized, the air quickly exits the article carrying with it trace particles of whatever was in the article. This is referred to as exhaling. Thus, the inhaling and exhaling is called “breathing.” Of course, it is also possible to provide a unidirectional air flow, or an oscillating or modulated unidirectional flow, rather than a bidirectional flow.
A significant particular aspect relates to moving particles toward openings of an article using moving sound pressure levels. Referring to
Referring to
The creation of standing sound waves is known in the art, and generally such known devices may be used in accordance herewith. The sound sources can be located at a distance apart that is an integer multiple of the wavelength, or may be located in any required distance as long as the sound sources reconstruct the shape of the required sound wave. However, integer distances are not required to create a standing wave. If opposing sound sources using the same frequency tune their phases properly, then a standing wave may be produced using virtually any distance between the sources.
The system may be auto-calibrated by controlling the phase and frequency of every sound source. This provides a relaxation of the requirements that constrain the spread and material of the sound source, thus auto-calibration can reduce system cost.
A preferred embodiment of such an arrangement would be a low frequency acoustic source, such as a subwoofer, at close proximity to an article, which transmits acoustic waves into the article. The waves pass through the walls and through the interior of the article. This induces a unidirectional force pushing particles toward the opposite end. Particles with differing weights are forced apart as the heavier ones are pushed aside the lighter ones and accumulate at the furthest reaches of the article.
In another embodiment, a low frequency acoustic source, such as a subwoofer, at close proximity to the article, transmits acoustic waves into the article. The waves pass through the walls and through the interior of the article. This induces a unidirectional force pushing particles toward the opposite end. Materials with differing densities will be forced apart as the denser ones will push aside the less dense ones and accumulate at the furthest reaches of the article.
By using moving standing waves, the present technology is able to separate between particles that have different weight and/or dimension. This is useful for a variety of needs requiring sorting by size and/or weight.
In another embodiment, the low frequency acoustic waves are used for mixing different materials within a hermetically sealed article. According to this embodiment, suitably arranged acoustic sources are placed around the at least one article and transmit acoustic waves into the at least one article. The waves are arranged in such a way as to induce flows within the material (solid, liquid or gas) that cause materials within the article to mix. Mixing materials within an article is useful for a variety of applications.
For example, it is possible to create waves and move particles inside an article by arranging the placement of the sound sources and by controlling the wave phases. It is to be understood that the method can be used to create virtually any waveform.
There are cases where it is difficult to agitate the particles into motion, or cases where the article or content is fragile, requiring controlled agitation. Low frequency acoustic agitation is useful in such cases, since it is convenient and easy to configure and control.
According to another optional embodiment, the low frequency system is used to mix materials. For example, industrial mixers mix one container of paint at a time; in order to mix large quantities of paint, a very large shaker is needed. By using the present invention, an entire crate of paint or containers of paint may be mixed by using low frequency wave generator mixer without the need of large mechanical apparatus.
Alternatively or additionally, the system of the present invention may be used for preventing sedimentation during long-term storage. According to this case, several low frequency acoustic sources, such as subwoofers, are located in close proximity to the article, and/or within a warehouse/storage enclosure, and transmit acoustic waves into the article. The acoustic waves, which pass through the walls and through the interior of the article, induce material flow. The induced material flow transports particles in the direction of the material flow. As the material flow turns around objects within the article, turn when nearing the walls of the article, the particles mix, and may equally disperse within the article.
In another embodiment of such an arrangement, several low frequency acoustic sources, such as subwoofers, located in close proximity to the article, transmit acoustic waves into the article. The waves pass through the walls and through the interior of the article. This induces material flow that causes the differing materials to move and mix, as if they are being stirred with each other.
In another embodiment, the low frequency waves are used for re-distributing particles within a hermetically sealed article. For example, coagulated liquids, such as blood, are frequently placed in centrifuges to separate the constituent species by density. The centrifuge sets up a force gradient causing an efficient separation of differing elements (since they have different densities) for later extraction of one or more of the constituents. However, there are coagulant fluids containing delicate substances, such as certain living cells, which cannot endure the rigors of centrifugal acceleration, and other means must be used for constituent separation. The present invention disclosed a method that is able to separate the different elements without applying centrifugal acceleration. According to this embodiment, properly aligned, low frequency acoustic moving standing wave energy is made to set up a pressure gradient field within the article to allow migration of heavier species to one side or another.
In order to obtain particle separation, the various sound sources have to be synchronized. If there are two sound sources operating in a fundamental frequency, i.e. the first mode, it is required that the minimum pressure be formed along a line towards the particles to be pushed to. In order to concentrate the particles in a predefined radius, more that two sound sources, for example four sound sources, need to be applying low frequency waves. By changing the phase of the sound sources, it is possible to control the location of concentration.
In another embodiment, the low frequency waves are used for mixing of various substances within a hermetically sealed article to counter the effects of differentiation by settling. According to this embodiment, the low frequency acoustic energy is used for creating a material flow that causes the mixing of species within the article.
There may be many applications where it is not desired to recover trace particles from within a hermetically sealed article, but it is necessary to move particles or other materials inside the hermetically sealed article. A system described herein can accomplish this by the low frequency acoustic wave mechanism as described above. The low frequency acoustic waves cause the walls of the article to vibrate at the same frequency as the incident wave and cause the wave to be created within the article. Hence, the article looks fairly invisible to the acoustic waves. Within the article, the waves create flows in the material, which can be used as a transport mechanism. Properly tuned, the transport mechanism may be used to cause particle separation or sedimentation of materials of differing densities.
In another embodiment, low frequency standing waves are formed within the article. Particles are forced to the antinodes of the standing waves. As the phase of one or more of the standing wave transmitters is varied, the standing wave moves, carrying the particles with it.
It is to be understood that when the particles are denser from the surrounding, the particles are forced to the antinodes of the standing waves. In the opposite case, when bubbles are removed from a liquid (wherein the bubbles may be any material lighter from the surrounding), the bubbles are forced to the nodes of the standing waves.
In another embodiment, low frequency standing waves are formed within an article/container, the article including materials featuring at least two materials having different density. By moving the standing wave within the article, the different materials are separated based on their density. Denser materials will be preferentially moved to the furthest extent of the motion of the antinodes within the container, while less dense materials will be blocked by the denser materials.
In still another embodiment, low frequency standing waves are formed within an article/container, wherein the article has at least two materials having different size. By moving the standing wave within the article, the different materials are separated based on their size. Smaller sized articles will be forced between the larger sized articles, by the movement of the antinodes.
The devices described above correspond to the methods for using low-frequency acoustic waves for moving particles inside articles, in accordance with the present invention. However, it is to be clearly understood that above described devices are readily extendable and applicable to the following description of exemplary methods.
Referring to
Setting particle concentration area and sound source location.
Alternatively stated, this step establishes the required zone of particle concentration and at least one sound source location. In this step, the required particle concentration area and at least one sound source location are defined. The particle concentration area location is measured preferably in relation to the at least one sound source but may be measured in relation to other reference points.
Calculating the sound source operating frequency.
The sound sources should produce standing waves or moving standing waves. The selected frequency depends on the required distance between the sound sources and the match between the specific frequency and the material upon which the sound waves are applied. Optionally, the frequency may be chosen to satisfy the requirement of not creating sound pollution to human or animal ears.
Calculating the available sound sources appropriate phase angles.
It is to be noted that in this case, the sound sources are already placed around the system and are stationary. The phase angles of the sound sources are calculated as known in the art. Moreover, in case the sound sources are not placed at distances that are discrete multiples of the wavelength, the sound sources may need to reconstruct the required phases of the sound waves in order to produce the required standing wave.
Operating the sound sources at the calculated phase and frequency.
The sound sources are operated as known in the art. The sound sources may be controlled by a controller as known in the art by using an open or closed loop control. Optionally, observing the actual location that the particles move to and recalculating the frequency and phase angles based on the difference between the observed location and the desired location.
Optionally, the sound sources are controlled by a closed loop controller, wherein the close loop controller measures the location that the particles move to. According to that measurement, the controller applies an appropriate correction. It is to be understood that the closed loop measurement can be implemented by any other known in the art measurement mechanisms, such as, but not limited to, optical, conductive, resistive, mass, strain, and observed measurements.
As is known in the art of closed loop control mechanisms, the above measurements are used for correcting the operation of the system. As a result, an updated command is fed into the sound source controller. Before changing the phases, the closed loop may take into account the current phase of the sound sources in order to change the phase in a continuous manner.
Referring to
Setting particle concentration area.
In this step, the at least one required particle concentration area is defined. The particle concentration location may be measured in relation to any appropriate reference point.
Setting the sound sources operating frequency.
In this step, the operating frequency of the sound sources is defined. The operating frequency may be defined independently of the location of the sound sources.
Calculating the appropriate location of the sound sources to be used, so that the anti nodes are at the desired locations.
As known in the art, when applying standing waves to particles, the particles are concentrated towards the anti nodes. When the frequency and the phase are given, the location of the antinodes depends on the distance between the sound sources. In this step, the appropriate distance is calculated and the sound sources are placed according to the result. This step refers to particles which are heavier than their surrounding fluid. Should the particles be lighter, then this step is the same except that nodes of the standing waves are used instead of the antinodes.
Operating the sound sources at the calculated frequency.
The sound sources are operated as known in the art. The sound sources may be controlled by a controller as known in the art by using an open or closed loop control.
Optionally, observing the actual location that the particles move to and recalculating the location of the sound sources.
Optionally, recalculating the location of the at least one sound source based on the difference between the observed location and the desired location of particle concentration.
Thus, it is understood from the embodiments of the invention herein described and illustrated, above, that the method and system for moving particles within an article, of the present invention, are neither anticipated or obviously derived from the prior art. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in various combinations in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.
It is to be understood that the present invention is not limited in its application to the details of the order or sequence of steps of operation or implementation of the system and corresponding method set in the description, drawings, or examples of the present invention.
While the invention has been described in conjunction with specific embodiments and examples thereof, it is to be understood that they have been presented by way of example, and not limitation. Moreover, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims and their equivalents.
| Number | Date | Country | |
|---|---|---|---|
| 60802119 | May 2006 | US |
