Abstract:
A collection device for collecting particles from a gas is provided. The device comprises a passage defined by a wall and at least one electrical field within the passage for charging particles, where the particles are in a gas. The device further comprises a moving collection surface for collecting charged particles. The moving collection surface is located within the at least one passage. The moving collection surface rotates through the at least one electrical field and then rotates to a detection device for detection of the particles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation-in-Part Application of U.S. patent application Ser. No. 11/426,159; filed Jun. 23, 2006, which is hereby incorporated in its entirety by reference. 
     
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND 
       [0003]    In many instances, it is necessary to determine impurities in a gas, such as air. For instance, collection and testing of a gas sample may be done to determine if any biological and chemical warfare agents are present in the sample. For instance, government facilities, airports, mail rooms, high-profile events, transportation and urban areas may monitor the air for biological and chemical warfare agents. 
         [0004]    Collection and testing of air may also be done to determine whether any environmental toxins are present in the air. For example, indoor and outdoor environments may be sampled to determine environmental impurities present in the air. Impurities may include micro and submicron bioaerosols, target airborne pathogens, including viruses and bacteria, as well as some explosive vapors and certain chemicals. 
         [0005]    Previous methods of concentrating impurities in air have employed filtering technology and collection of impurities in a liquid medium. These prior methods present serious disadvantages of both lowered extraction efficiency and are limited as to the type of particles that may be collected. Many current detection techniques, such as Raman spectroscopy and UV spectroscopic techniques require impurities in a gas, such as air, to be collected before analysis. 
         [0006]    Raman spectroscopy is a technique used in condensed matter physics and chemistry to study the vibration, rotation, and other low-frequency modes in a system. Raman spectroscopy relies on the scattering of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. Raman spectroscopy is commonly used in chemistry, since vibration-type information is very specific for the chemical bonds in molecules. It therefore provides a fingerprint by which the molecule can be identified. 
         [0007]    However, this detection technique often requires the substance to be dry in order to properly determine the substance. For detection of particles, such as chemicals and biological material, Raman detection often requires a collection of particles to be collected on a known substrate to properly determine the wavelengths of particles on the substrate. Furthermore, there are no current Raman detection techniques for continuously and efficiently detecting particles from atmosphere. 
       SUMMARY 
       [0008]    In one embodiment of the present invention, a collection device for collecting particles from a gas is provided. The device comprises t least one electrical field for charging particles, wherein the particles are in a gas and at least one continuously moving collection surface for collecting charged particles. The charged particles are collected on at least a portion of the continuously moving collection surface. Then the continuously moving collection surface is moved to a detection system. 
         [0009]    In another embodiment of the present invention, a method of collecting impurities from a gas is provided. At least one air passage defined by a wall and at least one electrical field within the at least one air passage are provided. Gas having particles is passed through the at least one electrical field to charge the particles in the gas. At least some of the charged particles are collected onto at least one moving collection surface. The at least one moving collection surface is moved so the collected particles and the at least one moving collection surface are presented to a detection system for determination of the type of particles collected. 
         [0010]    In yet another embodiment, a collection device for collecting particles from a gas is provided. The device comprises at least one passage defined by a wall and at least one electrical field within the at least one passage for charging particles, where the particles are in a gas. The device further comprises at least one moving collection surface for collecting charged particles, where the at least one moving collection surface is located within the at least one passage. The at least one moving collection surface rotates through the at least one electrical field and then rotates to a detection device for detection of the particles. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0012]      FIG. 1  is a top plan view of a collection device constructed in accordance with an embodiment of the invention; 
           [0013]      FIG. 2  is a top plan view of a collection device constructed in accordance with an embodiment of the invention with top of the device removed in accordance with an embodiment of the present invention; 
           [0014]      FIG. 3  is a side plan view of a collection device along lines  3 - 3  of  FIG. 1  in accordance with an embodiment of the present invention; 
           [0015]      FIG. 4  is a graphical representation of collection efficiency of a collection device in accordance with an embodiment of the present invention; and 
           [0016]      FIG. 5  is a top side plan view of a collection device constructed in accordance with an embodiment of the invention with top of the device removed in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Embodiments of the present invention relate to an electrostatic device that utilizes electrostatics to collect particles from gas, such as air. The particles are collected onto a moving collection surface such as a cylindrical drum or belt to concentrate particles from the air. The particles collected may be analyzed by inspection of the moving collection surface utilizing a variety of methods, including but not limited to, Raman detection, lasers and UV spectroscopic techniques. Target particles collected may include, but are not limited to, biologicals, such micron and submicron bioaerosols, molds, pollen, fungi, bacteria, viruses and bacteriophages, chemicals, such as low vapor pressure chemicals (LVPCs), explosives, toxins and other particles. 
         [0018]    With reference to  FIGS. 1 ,  2  and  3 , the collection surface  22  is continuously moving  34  during the collection process allowing for simultaneous collection and detection thereby reducing overall cycle times. Arrow  34  depicts the rotation of the moving collection surface  22 . It will be appreciated that the collection surface  22  may move or rotate in any direction. Using electrostatics, the collection system  10  collects incoming particles  50 , such as liquid and solid aerosols, on the moving collection surface  22 . As the collection surface  22  rotates  34 , it presents the particles  50  to a detector  32 . The detector  32  performs the necessary operations to determine the type of particles  50  collected and whether or not those particles are threatening. For example, if 20 particles of a substance are collected, the detector determines that finding ten or more particles of the substance is a threat, the detector sends out proper notification and collection stops. 
         [0019]    If the detector determines that all particles  50  collected are non-threatening, the surface continues moving to the cleaning zone  30 . In one embodiment, the moving collection surface is utilized to collect particles to determine the type of particles whether or not the particles are threatening. For instance, the collection device may be used by scientists and anthropologists to determine if certain particles are in the atmosphere in a certain area. The cleaning zone  30  cleans the particles  50  from the moving collection surface  22  and a vacuum (not shown) removes the particles  50  from the collection device  10  for disposal. The cleaned surface  52  re-enters the collection zone and collection of particles  50  from a gas, such as the atmosphere, starts again. This collection cycle allows for high collection efficiency through use of electrostatics and particle deposition on to a surface that can be readily interrogated utilizing optical detection techniques 
         [0020]    One embodiment the present invention relates to an electrostatic device  10  for the collection and concentration of particles. The device  10  comprises an air passage  16 , at least one corona charging zone  18 , a moving collection surface  22 , an air mover (not shown) and housing  12 . The device  10  brings gas, such as air, into the primary air passage  16  utilizing the air mover. The air is passed through primary air passage  16  and at least one charging zone  18  thereby forcing airborne particles onto the moving collection surface  22 . The electrostatic device  10  concentrates particles in the air to a concentrically located moving collection surface  22  to obtain particle concentration. 
         [0021]    With reference to  FIG. 2 , a corona charging zone  18  is created by a plurality of electrodes  24 . A series of electrodes  24  are spaced substantially equal angular distances on or within a duct  17  or walled space forming the primary air passage  16 . The electrodes  24  are used to create multiple ion streams  26  forming a corona charging zone  18  within the primary air passage  16  surrounding moving collection surface  22 . The amperage for each electrode may be about 0.5 to 5 Micro amps with a nominal of 1 micro amp being preferred. The corona charging zone  18  may be a substantially uniform electrical field. In the present embodiment, the corona charging zone  18  is shown as being a half-moon shape, however, it may be a variety of shapes, including circular, polygonal, square, rectangular and oval. It will be appreciated that charging zone may be created in a variety of ways. An exemplary charging zone  18  is described in described in U.S. Patent Application Publication No. 2004/0179322, the entirety of which is hereby incorporated by reference. 
         [0022]    Multiple rows  15  of electrodes  24  may be used to help improve collection efficiency. Each additional row of electrodes improves collection efficiency by increasing the plasma area of the corona charging zone  18 . It will be appreciated that device  10  may have any number of electrodes  24  and rows of electrodes  24 . 
         [0023]    An exemplary moving collection surface  22  cam be seen in  FIGS. 2 and 3 . The exemplary moving collection surface  22  in  FIGS. 2 and 3  is cylindrical hollow drum or duct. The thickness of the walls of the collection surface may be any size. In one embodiment, the walls are about 0.0625 inches thick. The moving collection surface  22  may also be a belt or tape  22  as shown in  FIG. 5 . The moving collection surface  22  may be of any diameter or length depending of the flow rate of the air through the air passage  16  and the voltage used to control the device  10 . For instance, the moving collection surface  22  may be any diameter. In one embodiment, the moving collection surface  22  is 2 to 4 inches in diameter. One of skill in the art will appreciate that the particles may be collected on any part of the moving collection surface  22 . 
         [0024]    The moving collection surface  22  rotates at approximate on (1) rotation per minute to give the detection system enough time to sample properly. More than one moving collection surface  22  may be located in the electrostatic device  10 . The moving collection surface  22 , while shown as being round, may be polygonal, triangular, rectangular, square or any variety of other shapes. The one or more moving collections surfaces may be removable. 
         [0025]    With reference to  FIGS. 1 and 3 , motor  36  is responsible for turning the collection surface  22 . The motor  36  is coupled to the top of the collection surface  22 . The appropriate internal mechanisms such as bearings and shaft are located within the moving collection surface  22 . The movement of the collection surface  22  may be held at a constant speed, varying speed, or in controlled incremental steps depending on the needs of the chosen detection method. 
         [0026]    The moving collection surface may be made of one or more materials. Preferably, the one or more materials are known materials that may be used with a Raman detection system or UV spectroscopic techniques such as stainless steel or the like. For example, a example the moving collection surface  22  may be made of only one material, for example stainless steel, or may be made of a combination of metals or any other electrically conductive materials. 
         [0027]    Referring again to  FIGS. 1 and 2 , the air passage  16  may be formed by enclosure such as walls or a duct  17 . While the air passage  16  of  FIGS. 2 and 3  is formed by a round duct and two walls  28 , the primary air passage may be any variety of shapes including polygonal, square, rectangular and oval. In this embodiment, air passage  16  is only half-moon shaped portion of the device  10 . However, it will be appreciated that air passage  16  may be any size. The primary air passage  16  surrounding the moving collection surface  22  may any size necessary for collection. In one embodiment, the air passage  16  is about 3-5 inches wide and the moving collection surface  22  is 2-4 inches in diameter. 
         [0028]    Housing  12  encases the air passage  16 , corona charging zone  18  and moving collection surface  22 . It will be appreciated that housing  12  may be any type including modular housing. As can be seen in  FIG. 1 , portions of the modular housing  12  may be removable to gain entry into the collection device  10  for maintenance and repair purposes. For example, the portion of the housing  40  is removable to gain access to the primary air passage  16  and electrodes  24 . A portion of the housing  38  is removable to provide access to the cleaning zone  30 . 
         [0029]    The air mover may be any variety of air movers, including fans. Exemplary air movers include commercial, of the shelf fan, such as small muffin fans like those generally used to aid in the cooling of computer processors. It will also be appreciated that the collection device may be utilized without an air mover. 
         [0030]    Utilizing a fan, the sampling flow rate for the collection device  10  pulls air through the collection zone at a flow rate of 100-200 L/min.  FIG. 4  shows efficiency vs. particle size. As can be seen from  FIG. 4 , collection efficiencies range from about 70 to 85% for particle diameters between about 1 μm and 2 μm, respectively and from about 80 to 95% for particle diameters between about 2 μm and 6 μm. The target particulate size is in the range of about 0.5 to 10 μm in diameter. It will be appreciated that the flow rate, collection efficiency and target particle size collected by device  10  may vary dependent on device configuration. 
         [0031]    A variety of power supplies may be utilized to power collection device  10 . The power supplies include internal and external power supplies. The power supply may power the air mover, electrodes  24 , rotation of the moving collection surface  22  and removal of the particles cleaned from the moving collection surface (described in more detail below). In one embodiment, the system is a 24 volt system. The power consumed by the collection device  10  may vary, but preferably is less than 4 Watts. 
         [0032]    After collection is completed, particles  50  collected on the moving collection surface  22  are moved or rotated to a position such that one or more detectors  32  may analyze the particles  50 . As described above, the detector  32  may be any variety of optic based detection systems including laser detection systems, such as Raman detection systems, direct microscopy and UV spectroscopic techniques. The detection systems may be an integrated part of the collection device  10  or may be separate from the collection device  10 . 
         [0033]    Device  10  includes an integrated cleaning mechanism to remove collected particles from collection surface  22 . Cleaning mechanisms  30  that may be utilized include, but are not limited to, heating the collection surface  22 , employing a brush or other mechanical cleaning method, chemical treatment of the surface and rinsing the collection surface  22  with a liquid, such as water. 
         [0034]    The cleaning mechanism depicted in  FIGS. 2 ,  3  and  5  is a brush cleaning system. The brush  30  is positioned such that particles cleaned from the collection surface  22 , can be easily removed from the unit. Brush is preferable of synthetic materials to reduce the risk of re-introduction of organic materials during the detection cycle. The brush rotates counter to the movement of the collection surface to maximize the cleaning effort and to force the particles toward the vacuum port (not shown). The cleaning system brush is operated at approximately 200 rpm. Particles removed from the device  10  utilizing a cleaning mechanism may be saved for subsequent sampling. The particles may be dry, in vapor form or wet collected. 
         [0035]    The heating of collection surface  22  may be performed to clean the surface converts collected particles into a vapor form. This vapor form may be usable by detectors, such as chemical detectors, mass spectrometry (such as a MEMS mass spectrometer), and ion mobility spectrometry. Heating of the collection surface may be done in a variety of ways including, but not limited to, an internal cartridge heater, coil heating, contact heating, creation of a high-intensity corona, UV heating and laser ablation of particles on collection surface. 
         [0036]    Once the particles have been removed from the collection surface  22  by heating, the resulting vaporized particles are drawn through an external port in the device  10 . The transport of the vaporized particles will be controlled either through a secondary port on the side of the device  10 , or by the primary exit by re-activating the air mover. 
         [0037]    By way of example, and not by limitation, in order to meet a target time of about thirty seconds from starting to finishing, the collection and detection of target particles and cleaning of the collection particles is about 60 seconds. To achieve this target, the moving collection surface completes a rotation through the electrical field for collection, past the detector for detection of particles and through the cleaning zone in about 60 seconds. In this embodiment, the surface area spends 30 seconds in the electrical field, 15 seconds in the detection area, and 15 seconds in the cleaning zone. It will be appreciated, however, that the time for collection, detection and cleaning may vary according to need and may be any amount of time. 
         [0038]    The exemplary collection moving collection surface  22  in  FIG. 5  is a belt. The belt  23  may be wrapped around rollers, ducts or drums. The exemplary collection device  10  of  FIG. 4  depicts the belt  23  wrapping around two cylindrical drums. It will be appreciated that any number of rollers, ducts or drums may be used. The movement of the two cylindrical drums is depicted by arrows  34 . The rollers, ducts or drums may move the belt  23  in any direction necessary for use with a detection system. As the two cylindrical drums rotate, the belt  23  is moved through at least one corona charging zone  18  and particles  50  are collected onto the moving belt  23 . The belt  23  is rotated and the surface of belt  23  having collected particles  50  is presented to a detector  32 . After the detector  32  performs necessary operations to determine the type and number of particles collected on belt  23 , the surface continues to the cleaning zone  30 . 
         [0039]    It will also be appreciated that the belt  23  may be secured to any securing mechanism and is not limited to rollers, ducts or drums. The collection device  10  of  FIG. 5  provides a flat moving surface for use with detectors allowing for improved reading of the particles collected on the belt  23  utilizing Raman detection. The belt  23  of  FIG. 5  is made from stainless steel. However, it will be appreciated that the belt may be made of any variety of materials. 
         [0040]    From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent in the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.