Abstract:
A self-cleaning system and method for removing contaminants captured by an air flow filter media in which a reverse air flow is directed back through the filter media and into an antechamber which is closed during self-cleaning and a vacuum source is connected to the antechamber to quickly evacuate the air in said antechamber containing dislodged contaminants suspended therein.

Description:
BACKGROUND OF THE INVENTION 
     This invention concerns air filtration such as is used in HVAC and industrial air filtration and dust collection systems. 
     High efficiency filters remove a large proportion of contaminants, but will quickly become clogged due to buildup of the contaminants on the filter media since a great proportion of the contaminants in the air flow will be filtered out. 
     Much labor would be required to keep such filters clear by manual removal of the build up of contaminants captured by the filter media. 
     For this reason, disposable or cleanable prefilters are often used to remove the larger contaminants from the air stream in order to reduce the servicing requirements for the more costly high efficiency filters. However, the inclusion of additional prefilters will add to the maintenance costs of the system. 
     Self-cleaning air filters are well known which typically carry out cleaning by establishing a reverse air flow through the filter media to dislodge the contaminants, and collecting these contaminants in a lower space which is accessible for periodic disposal of the collected contents. 
     In this arrangement, dislodged contaminants may be suspended in the air just upstream of the filter media, and can be drawn back onto the filter media when normal operation is restarted. 
     In another arrangement, a sustained reverse flow can be established which is directed to an exhaust port to thereby make sure that the contaminants are not recaptured by the normal air flow after the reverse flow ceases. 
     This approach interrupts normal air flow for a significant time and requires a substantial volume of reverse flow through the filter media and a purging flow through the space just upstream of the filter media. 
     It is also known to periodically direct a brief reverse flow to dislodge the contaminants from the filter media, which it is hoped will settle out and be received in a collection space. This approach minimizes the interruption of normal operation, but is even more likely to result in dislodged contaminants being drawn to the filter media after normal flow through the filter is restored as described above, since only a brief reverse flow occurs, and all of the contaminants will likely not have a chance to settle out away from the filter media before restarting normal air flow. 
     It is an object of the present invention to provide a self-cleaning air filtration system which will minimize the interruption of the normal air flow in the system while insuring a rapid and substantially complete removal of dislodged contaminants. 
     SUMMARY OF THE INVENTION 
     The above recited object of the invention and other objects which will be understood by one skilled in the art upon a reading of the following specification and claims are achieved by periodically establishing a short duration reverse flow of high pressure air through the filter media into an antechamber adjacent the filter media which normally receives the air flow to be filtered. The antechamber is briefly closed off from normal air flow as by closing dampers immediately upstream from the antechamber at the start of the cleaning cycle. A vacuum source is thereafter briefly connected to the antechamber with a sufficiently high vacuum to quickly evacuate air from the antechamber, and in a short time removing all of the solid contaminant particles suspended in the air in the antechamber which have been dislodged by the reverse flow through the filter media. 
     Thus, a minimized period of interruption of normal operation is achieved, while insuring a substantially complete removal of dislodged contaminant particles. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic representation of a filtration section of an air delivery system according to the invention in a normal operating state. 
         FIG. 2  is a diagrammatic representation of the filtration section of an air delivery system shown in  FIG. 1  undergoing a periodic self-cleaning operation. 
         FIG. 3  is a diagrammatic representation of the air delivery system of  FIGS. 1 and 2  showing a combined vacuum and air flow sources. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. 
     Referring to the drawings, a self-cleaning filtration section  10  of an air flow system according to the invention is depicted diagrammatically in its normal operating state, in which a sustained air flow from a source  12  is directed into an antechamber  14  adjacent a filter media on the inlet side thereof. 
     A damper mechanism  16  including an actuator  17  is provided which is normally open but is controllably operable to close off an air inlet  18  at the inlet end of the antechamber  14  which receives the air flow to be filtered. 
     The filter media  20  is disposed at the other end of the antechamber  14  which receives air flow to be filtered, passing through the same and into an outlet  22 . 
     A vacuum suction port  24  is also provided opening into the antechamber  14  with a damper mechanism  26  including an actuator  27  is provided which is also normally closed but is able to be controllably opened. 
     The vacuum port  24  is located adjacent to the inlet side of the filter media  20 , and is connected to a vacuum source  28  which can be comprised of a vacuum pump which is turned on and off to draw air out of the antechamber  14  or another vacuum source which is controllably connected to the antechamber  14 . 
     The reverse air flow delivery system  30  includes a source of high pressure air  32  such as the output of a blower. 
     The reverse air flow delivery system  30  is connected to an array of flow nozzles  34  mounted in the outlet chamber  22  with a manifold  36  positioned just downstream of the filter media  20  to create high velocity jets of reverse air flow directed at the filter media  20 . 
     Various arrangements for generating the vacuum and reverse air flow are possible as will be understood by those skilled in the art. 
     The array of nozzles  34  being juxtaposed to the upstream side of the filter media  20  allows a high velocity reverse flow of air to be periodically directed back through the filter media  20  into the antechamber  14 . 
     The reverse air flow causes gusts of high velocity reverse air flow through the filter media  20  to occur. 
     At the beginning of a self-cleaning cycle, the air inlet damper mechanism  16  is operated by activation of the actuator  17  by system control  38  to close off the antechamber  14  from its air inlet  18 , as seen in  FIG. 2 . 
     At the same time a reverse air flow is initiated, as by establishing a reverse air flow from source  32 , the vacuum port  24  is opened as by operating the damper mechanism  26  with actuator  27  to open the same and establish a fluid connection to the vacuum source  28 . 
     This initiates a rapid evacuation of air from the antechamber  14  to very quickly carry off the dislodged contaminants which have been suspended in the air in the antechamber  14  by the reverse air flow. 
     The vacuum suction port  24  is thereafter operated to close off communication of the vacuum source  28  with the antechamber  14 . 
     The inlet damper mechanism  16  is reopened by actuator  17  at the same time to restore normal operation. 
     Thus, a minimized time of interruption of normal air flow operation is required, since the high velocity jets and vacuum evacuation of dislodged contaminants greatly expedite the self-cleaning process. 
     The actual duration of the reverse air flow and the magnitude of the reverse flow velocities would depend on the needs of a particular application, as will be understood by those skilled in the art. 
       FIG. 3  shows a vacuum source comprised of the inlet  28 A to a blower  40 . 
     A separator  42  is required, such as a cyclonic filter to remove the solid contaminants and deposit the same in a collector  44 . 
     The reverse air flow delivery  30  comprises the outlet  32 A of the blower  40  connected to manifold  36  to supply the reverse air flow to the nozzles  34 .