Abstract:
An autonomously-cleaned conditioning system conducts a routine purge cycle to clear accumulated particulates from a filter, concentrator, or both. The purge cycle is conducted by reversing air flow through the filter and/or concentrator. Air flow is reversed on a periodic basis or on the occurrence of a condition, such as a reduction in air flow exiting the concentrator.

Description:
STATEMENT OF RELATED CASES  
       [0001]     This case is a continuation-in-part of U.S. patent application Ser. No. 11/082,721 (Atty Dkt: 711-048us) filed Mar. 17, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to systems that include filters and/or concentrators for conditioning gas flow to sampling, analysis, or detection systems.  
       BACKGROUND OF THE INVENTION  
       [0003]     A filter, a concentrator, or both, is often used in conjunction with sampling, analysis, and detection devices. The filter is used to prevent certain particulates (e.g., those out of a size range of interest, those likely to cause mechanical problems, etc.) from reaching analysis or detection equipment. The concentrator is used to increase the concentration of particles in a volume of gas (e.g., air, etc.).  
         [0004]      FIG. 1  depicts conventional conditioning system  100  being used in conjunction with detector  114 . In this example, the purpose of detector  114  is to monitor the air for particles within a certain size range, such as between 1 to 10 microns. The function of conditioning system  100  is to deliver particles within the size range of interest, and at a concentrated level, to detector  114  and to prevent particles that are larger than the size range of interest from reaching concentrator  104  or detector  114 . The air-flow through system  100  is depicted by the arrows.  
         [0005]     Conditioning system  100  includes filter  102 , concentrator  104 , and pumps  110  and  112 . Filter  102  traps relatively large particles (i.e., greater than about 15 microns in this example) to prevent them from reaching concentrator  104  and/or detector  114 . Pumps  110  and  112  are used for drawing air through filter  102 , concentrator  104 , and detector  112 . In particular, for the system depicted in  FIG. 1 , pump  110  is used to draw air through port  106  and pump  112  is used to draw air through port  108  toward detector  114 . Particles that are smaller than the size range of interest are drawn through port  106 . Particles within the size range of interest are drawn through port  108 .  
         [0006]     Filter  102  and concentrator  104  typically include surfaces that tend to clog, especially when the filter or concentrator are used in dirty environments, such as underground passages or tunnels, etc. Frequent maintenance is therefore required to maintain the performance of these conditioning-system elements. This drives up the operational cost of devices that use a conditioning system, such as detector  114 .  
         [0007]     This problem of clogging has been addressed in the prior art by using replaceable mesh-filtration systems. But these filters must be replaced when they clog, which occurs frequently in dirty environments.  
         [0008]     As a consequence, there is a need for device or system for addressing the clogging problem in filters and concentrators.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a way to autonomously clean a conditioning system (i.e., a filter, a concentrator, or both, as well as associated conduits and pumps) and avoid the frequent and costly maintenance intervals that are typical of this system.  
         [0010]     The illustrative embodiment of the present invention is an autonomously-cleaned conditioning system. The system autonomously-cleans the filter, concentrator, or both (the term “conditioning elements” is also used to refer to a filter, a concentrator, or both) via a routine purge cycle. The purge cycle is conducted by reversing the gas flow through the conditioning elements. This has been found to be effective for removing particulates that have accumulated on surfaces in and around the conditioning elements. The removed particulates can be exhausted, directed to a trap, or collected for later examination. Gas flow is reversed on a periodic basis (e.g., hourly, etc.) or on the occurrence of a condition (e.g., reduced gas flow in the forward direction through the condition elements, etc.), or both.  
         [0011]     In some embodiments, the autonomously-cleaned conditioning system comprises a purge system and a control system, in addition to the elements normally present in a prior-art conditioning system (i.e., a filter, concentrator, or both, and one or two pumps). The control system comprises at least one multi-way control valve and control elements (e.g., a controller, etc.) for controlling the multi-way control valve. In some embodiments, the purge system comprises a purge pump. In some other embodiments, the autonomously-cleaned conditioning system does not require a separate purge pump. Rather, the one or more pumps that are normally used in conditioning systems are appropriately piped and valved to enable the gas flow to be reversed without using an additional pump. In other words, the standard pumps become part of the purge system.  
         [0012]     A variety of different designs are known and used in the art for filters and concentrators. But all such conditioning elements include surfaces that tend to accumulate particulates. As a consequence, any standard conditioning elements can be reconfigured as an autonomously-cleaned conditioning system in accordance with the present teachings. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0013]      FIG. 1  depicts a conventional conditioning system for use with a detector.  
         [0014]      FIG. 2  depicts an autonomously-cleaned conditioning system in accordance with the illustrative embodiment of the present invention, wherein the system is depicted in a particle detection (i.e., normal operating) mode.  
         [0015]      FIG. 3  depicts the autonomously-cleaned conditioning system of  FIG. 2 , wherein the system is depicted in a cleaning or purge mode.  
         [0016]      FIG. 4  depicts a first variation of the illustrative embodiment.  
         [0017]      FIG. 5  depicts a second variation of the illustrative embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0018]     The following terms are defined below for use in this specification, including the appended claims: 
        The term “upstream” refers to the location of an element in a system relative to another element of the system vis-à-vis the flow of a fluid through the system during normal operation. In other words, a first element that is said to be “upstream” of a second element means that a fluid, etc., flowing through the system during normal operation, will encounter the first element before it encounters the second element.     The term “downstream” is the converse of upstream. That is, a second element that is said to be “downstream” of a first element means that fluid, etc., flowing through the system during normal operation, will encounter the second element after it encounters the first element.     The phrase “fluidically coupled,” when used to describe a relationship between two regions or elements, means that fluid can flow from one of the regions or elements to the other. The flow from one element to another can be through other elements; in other words, two regions or elements that are fluidically coupled are not necessarily physically connected to one another.        
 
         [0022]      FIG. 2  depicts autonomously-cleaned conditioning system  200  in accordance with the illustrative embodiment of the present invention. This system can be used in conjunction with a variety of different types of devices and systems including, without limitation, sampling, analysis, and detection devices.  
         [0023]     Autonomously-cleaned conditioning system  200  includes elements of a standard conditioning system, as well as a purge system, and a control system. In the illustrative embodiment, the elements of a standard system include filter  102 , concentrator  104 , and pumps  110  and  112 . The purge system comprises purge pump  220 . And the control system includes upstream flow control valve  216 , downstream flow control valve  218 , flow sensor  222 , controller  224 , and clock  226 .  
         [0024]      FIG. 2  depicts system  200  during particle detection (i.e., normal operation). In this mode, air is drawn through system  200  toward detector  114  along substantially the same path as for conventional conditioning system  100  (depicted in  FIG. 1 ).  
         [0025]     In particular, air is drawn through filter  102 , which traps relatively large particles (e.g., greater than 15 microns, etc.) to prevent them from reaching concentrator  104  and detector  114 . Responsive to a signal from controller  224 , upstream control valve  216  is configured to pass air flow toward concentrator  104 . In this state, upstream control valve  216  prevents air from flowing to conduit  228 . Likewise, responsive to a signal from controller  224 , downstream control valve  218  is configured to pass air flow toward detector  114 . In this state, control valve  218  prevents air from flowing to conduit  230 . For normal operation (forward flow), autonomously-cleaned conditioning system  200  operates at an inlet pressure of about 2 psig, but can vary upward or downward based on the system design, and variations in system flow rate, filter and orifice resistances, etc.  
         [0026]     In accordance with the illustrative embodiment, and as depicted in  FIG. 3 , autonomously-cleaned conditioning system  200  is automatically subjected to a purge cycle. During the purge cycle, air flows in a reverse direction through at least one of conditioning elements  104  and  102 . During the purge cycle, the pressure at the outlet of concentrator  104  (which is the “inlet” during the purge cycle) is about 20-35 psig, as a function of system design. The reverse flow of pressurized air dislodges clogged particulates and routes them to one of several locations, as described further later in this specification.  
         [0027]     In the illustrative embodiment, the purge cycle can be initiated in either one of two ways. In particular, any given purge cycle is initiated periodically (i.e., on a timed basis) or based on a change in an operating parameter of autonomously-cleaned conditioning system  200 .  
         [0028]     As to the former method, controller  224  periodically initiates a purge cycle in conjunction with clock  226 . For example, in some embodiments, a purge cycle is scheduled and implemented on an hourly basis. The periodicity of the purge cycle is a function of the environment in which autonomously-cleaned conditioning system  200  operates. For example, one way in which to set the cycle time is to perform a field trial to determine how quickly particulates accumulate within conditioning elements  102 / 104 . Based on the trial, the cycle time is set to keep the condition elements free of accumulated particulates. Alternatively, the cycle time might be based on the average time that it takes for air flow to drop to some fraction (e.g., 90 percent, etc.) of its initial rate through clean conditioning elements  102 / 104 . Those skilled in the art, after reading the present disclosure, will be able to set a desired cycle time in conjunction with field testing or other experimentation.  
         [0029]     Notwithstanding the efficacy of field testing to determine a cycle time, any number of upset or seasonal conditions might cause conditioning elements  102 / 104  to clog at an unexpectedly accelerated rate. For example, if construction is taking place in the area in which autonomously-cleaned conditioning system  200  is operating, it is likely that additional particulates will be present in the air. Furthermore, during spring and summer, the pollen count will increase the level of particulates in the air. As a consequence, initiating the purge cycle at a specific time interval might prove to be ineffective for reliably preventing clogs in the conditioning elements.  
         [0030]     Therefore, and in accordance with the illustrative embodiment, autonomously-controlled conditioning system  200  also includes a sensor, wherein the sensor is capable of initiating the purge cycle when it senses a change in a monitored operating parameter, such as, for example: 
        the rate of air flow leaving filter  102 , concentrator  104 , or both individually or collectively; or     the pressure drop across filter  102 , concentrator  104 , or both individually or collectively.        
 
         [0033]     In the illustrative embodiment, the air flow rate leaving concentrator  104  is monitored by flow sensor  222 . This flow sensor is capable of generating a signal that is indicative of the air-flow rate immediately downstream of concentrator  104 . The signal that is generated by flow sensor  222  is transmitted to controller  224 . The controller compares the signal to a set-point signal that is representative of, for example, a minimum acceptable air flow rate. If the air flow rate drops below the set-point, controller  224  generates and transmits signals, as appropriate, to initiate the purge cycle.  
         [0034]     Accordingly, based on either: (1) time or (2) a change in an operating parameter, as described above, controller  224  generates and sends a signal to pumps  110  and  112  to shut down. Also, controller  224  transmits a signal to control valve  218 . When it receives the signal that indicates that the purge cycle is to begin, control valve  218  changes state so that flow from conduit  230  toward air concentrator  104  is allowed while flow toward detector  114  is blocked.  
         [0035]     Furthermore, controller  224  transmits a signal to purge pump  220 , which causes the purge pump to actuate. The purge pump then draws intake air and pumps it into conduit  230 . The pressurized purge-air passes through control valve  218  toward concentrator  104  and, in some embodiments, filter  102 . Accumulated particulates are dislodged and picked up by the purge-air. The particulate-laden purge-air flows through control valve  216  to one of two destinations based on the state of control valve  216 .  
         [0036]     In the illustrative embodiment, control valve  216  blocks the flow of purge air toward conduit  228  and enables the flow of purge-air to filter  102  and then to a recovery system. In some other embodiments (not depicted), control valve  216  blocks the flow of purge air to filter  102  and enables the flow of purge air to conduit  228  and then to a recovery system.  
         [0037]     The purge cycle is continued for a predetermined period of time and then stopped. Controller  224  then transmits signals to the various control valves and pumps, as appropriate, to ready autonomously-cleaned conditioning system  200  for normal operation.  
         [0038]     In the illustrative embodiment, autonomously-controlled conditioning system  200  includes appropriate elements and is suitably programmed to initiate the purge cycle based on both time and a decrease in air-flow, whichever dictates. In some alternative embodiments of autonomously-controlled conditioning system  200 , the purge cycle is initiated only a time basis. And in yet some further alternative embodiments of autonomously-controlled conditioning system  200 , the purge cycle is initiated only on the occurrence of a changed operating parameter. These alternative embodiments might be selected in preference to the illustrative embodiment when, for example, a simpler system is desired or otherwise necessary.  
         [0039]     While in the illustrative embodiment, flow sensor  222  is located downstream of concentrator  104  to monitor the flow from this element, in some other embodiments, flow sensor  222  is located directly downstream of filter  102  to monitor the flow out of the filter. And, in some additional embodiments, flow sensors are located in both locations.  
         [0040]     It was previously disclosed that during the purge cycle, pumps  110  and  112  shut down. In some alternative embodiments, autonomously-controlled conditioning system  200  is appropriately piped and valved so that pumps  110  and  112  continue to operate during the purge cycle. Instead of shutting down these pumps, various control valves (not depicted) change state such that pumps  110  and  112  are no longer fluidically coupled to concentrator  104 . In this changed state, the pumps cannot draw air through concentrator  104 , even though they continue to operate. Meanwhile, purge pump  220  drives the purge cycle.  
         [0041]     In the illustrative embodiment, autonomously-controlled conditioning system  200  includes purge pump  220 . In some alternative embodiments, autonomously-controlled conditioning system  200  does not incorporate purge pump  220 . Rather, pumps  110  and  112  are suitably piped and valved to provide the functionality of purge pump  220 .  
         [0042]     Those skilled in the art, after reading the present disclosure, will be able to design and implement a control system that is capable of cycling autonomously-controlled conditioning system  200  between normal operation and a purge cycle.  
         [0043]      FIG. 4  depicts autonomously-cleaned conditioning system  400 , which is a variation of autonomously-cleaned conditioning system  200 . In the variation that is depicted in  FIG. 4 , purge pump  220  fills ballast  432  with pressurized air (e.g., about 1 liter at 60 psi) for the purge cycle. When the purge cycle initiates (either periodically or based on sensor readings, as previously described), a signal from controller  224  causes control valve  434  to quickly open. This releases the pressurized air from ballast  432 , which courses through the system to dislodge clogged particles, etc. In this embodiment, control valve  216  directs purge air toward conduit  228 , rather than filter  102 . The operation of the other elements of system  400 , including pumps  110  and  112 , control valve  218 , purge pump  220 , flow sensor  222 , controller  224 , and clock  226  is the same as previously described for autonomously-cleaned conditioning system  200 .  
         [0044]      FIG. 5  depicts autonomously-cleaned conditioning system  500 , which is a second variation of autonomously-cleaned conditioning system  200 . In the variation depicted in  FIG. 5 , conduit  228  is not present and, as a consequence, upstream control valve  216  is not required. In conditioning system  500 , purge flow passes through concentrator  104  as well as filter  102 . The operation of the other elements of system  500 , including pumps  110  and  112 , control valve  218 , purge-pump  220 , flow sensor  222 , controller  224 , and clock  226  is the same as previously described for autonomously-cleaned conditioning system  200 .  
         [0045]     Autonomously-cleaned condition systems  200 ,  400 , and  500  include both filter  102  and concentrator  104 . In some other embodiments, only a filter is included in the conditioning system, while in some further embodiments, the only conditioning element present is a concentrator.  
         [0046]     It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Furthermore, it is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.