BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention involves a device for removing paper fibers and dust from air traversing a pneumatic conveying system used in conjunction with printers or other waste fiber producing mechanisms. The invention removes waste fibers and dust from the working environment and pneumatically separates the dust from the fiber, retaining waste paper debris and paper fiber for recycling and collecting dust for disposal while returning purified conditioned air to the work environment. 
     2. Description of the Prior Art 
     In industrial environments such as printing plants and paper converting plants, large amounts of paper debris and paper fibers are generated by the operation of printers and/or paper cutters where scraps of paper are produced. Debris, fibers and dust are required to be removed from the air to maintain a healthy working environment. Generally, such waste is produced in an environment where air is conditioned to maintain a comfortable work place for employees. The normal mode of operation to purify conditioned air is to remove unfiltered air through a conduit to an exterior filtering device, and exhuast the air either to the outdoor environment or return it to the work environment, in either case losing much of the conditioned property of the air. Thus, there exists a need within the art to remove the debris and fibers of paper or other such material from the working environment without the loss of the conditioned property of air (heated or cooled). 
     Paper debris and paper fibers also have monetary value when collected for recycling. Such debris, when collected, accumulates dust and dirt from the environment and it is desirable to retain the large debris fiber in a compact form for recycling while at the same time, removing the dust from the fibers for disposal. 
     While several systems are known which accomplish similar or partially similar tasks of filtering air, no invention is known which meets all of the objectives of the present invention. 
     For example, known to the applicant are Krantz, U.S Pat. No. 4,581,050, and Higgins, U.S. Pat. No. 3,826,066. Each disclose double wall filter bag constructions where there is an annular space between bags. An inner bag separates larger particles from the waste stream, and the outer bag removes finer particles and acts as a second filter. Multi-stage dust removal systems are also disclosed in Dupre, U.S. Pat. No. 4,224,044. Paper balers are also commonly used within the industry. None of the prior art, however, accomplishes all of the objectives of the present system within a single unit or according to the present method. The present invention provides a waste removal system for conditioned air which eliminates the gain or loss of temperature of the filtered air and separates waste such that reusable waste is rid of dirt, segregated, and compacted for recycling, while dirt and dust are accumulated for disposal. 
     SUMMARY OF THE INVENTION 
     The solution to the problem of paper fiber and debris removal from air, while retaining conditioned air within the working environment and simulatneously compacting paper relieved of dirt and dust for recycling is encompassed within the present invention. Conditioned air carrying both paper debris fibers and dirt particles is pneumatically carried through the disclosed invention, whereby unfiltered air is forced into the inner bag of a double bag filter system. Paper debris and paper fiber are collected and deposited in a baler connected to the inner bag while air and dirt enter the outer bag. Some air escapes to the environment through the outer bag wall, leaving dust behind, with most of the dust laden air within the outer bag being carried to a secondary filter system. Clean air is released by migration of air through the porous wall of the secondary filter system and dust is collected for disposal. The results are threefold: conditioned air is retained and purified within the working environment, and paper debris is rid of dirt and dust and then baled for recycling, all within the same system. Flow throughout the system of air, dust and debris is regulated by alternating positive and negative air pressures within the system. 
     It is one object of the invention to provide an air filtering system for conditioned air which removes non-gaseous particles from said air while retaining the conditioned properties of the air and returning it to the internal work environment. 
     It is another object of the invention to provide an air filtering system which is compact enough to be retained within the work environment that it serves and which separates dirt and dust from reusable waste particles contained within unfiltered air. 
     It is a further object of the invention to process reusable waste into a compact form for recycling and to separately collect dirt and dust particles removed from air for disposal. 
     It is yet another object of the invention to enhance the quality of recyclable waste by removing dirt and dust particles therefrom. 
     The preferred embodiment of the method and apparatus for filtering air and separating dust from reusable waste as described herein is characterized by a pneumatic conveying system comprised of an initial filter system having double filter bags or tubes of dissimilar fabrics with the outer bag concentrically enveloping the inner bag. Unfiltered air is drawn and deflected downward into the inner bag. Air carrying dust exits the mesh wall of the inner bag, migrating into the space between the outer and inner bags. A chute connected to a paper baler beneath the inner bag catches paper and large fibers which are forced downward by gravity, air flow, and momentum as the large particles hit the deflector. A portion of the air migrates through the pores of the outer bag wall, depositing dust on the inner wall of the outer bag. The remaining dust and air are drawn through the dust fan and deposited in a secondary bag where the dust is collected and air escapes through the walls of the secondary filter. Thus, air migrates in a filtered state to the work environment rather than being exhausted to an external environment. The dust fan is intermittently operated to alternately create positive and negative air pressures throughout the system, causing both the initial and secondary filter bags to palpitate thereby releasing dust and paper accumulated on the filter walls. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the present invention, connected to a floor pipe which delivers air to be purified to the apparatus from any mechanism or machinery which produces recyclable debris. 
     FIG. 2 is a cross-sectional view of the double bag and baling assembly of the present invention, illustrating the internal operation of the bags and baler. 
     FIG. 3 is a top plan view of the present invention. 
     FIG. 4 is a side elevational view of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred exemplary embodiment of my invention is illustrated in FIGS. 1-4, wherein like numerals represent like parts. The method and apparatus for filtering conditioned air and separating dust from reusable waste is primarily designed for removing paper debris and fiber and dust from conditioned air used in conjunction with printers and paper cutting mechanisms which produce paper scraps. The device is, however, not limited to removing paper debris, but can be used in conjunction with any mechanism that produces a recyclable waste product. Such examples would be wood working mechanisms where sawdust and wood chips are produced, or in metal grinding or molding operations where metal shavings are generated. 
     As a general overview, the method and apparatus for filtering air and separating dust for reusable waste is driven by a double fan system. A system fan 20 draws conditioned air filled with dust, paper debris and paper fibers to the initial filter stage 30. Reusable debris and fibers are separated and drawn into a baler 50 while dust laden air is drawn away from the initial filter 30 to a secondary filter by means of a dust fan 60. The dust fan is operated intermittently, such that positive and negative air pressures are created within the system causing the initial and secondary filter bags to palpitate, thereby releasing the particle build-up on filter walls. 
     In the preferred embodiment the filtering system 10 is connected to any mechanism which produces a waste-rich air stream such as a printer or paper cutter by means of a floor pipe 2 or other means. A system fan 20 draws unfiltered air from the floor pipe 2 into the filtering system 10. The the waste rich air stream is delivered to the floor pipe 2 and thus into the system from any remote area of the work environment in any suitable manner. A sweeping mechanism 4 is attached to the floor pipe 2 such that additional debris, such as floor sweepings, can be manually inserted into the system. The sweeping mechanism 4 is essentially a tributary pipe 6 connected to the floor pipe 2 and includes a trap door 8 by which floor sweepings, dirt, and debris can be manually swept into the filtering system 10. 
     The system fan 20 creates suction from the floor pipe 2 and positively forces the unfiltered air up through a delivery pipe 12 to the initial filter 30. 
     The initial filter 30 consists of a double bag or double tube filter where the inner bag 32 is concentrically contained within an outer bag 34 such that an annular space 33 is maintained between the bags. The double bag arrangement is supported from above by a doughnut shaped duct 14 having a deflector 16 covering the hole 18 in the duct 14. Steel bands 21 and 22 form the inner and outer casings of the top duct 14 and support the inner and outer bags 32 and 34, respectively, so that the annular space 33 is maintained therebetween. The bottom of the double bag arrangement is supported by a lower doughnut shaped duct 36 with a hole 38 having inner and outer steel bands 41 and 42 as support casings. The inner tube 32 is secured about the holes 18 and 38 of the ducts 14 and 36, respectively, by inner steel bands 21 and 41, while the outer bag 34 is supported by the respective exterior steel bands 22 and 42 of the ducts 14 and 36. 
     The delivery tube 12 delivers unfiltered air from the system fan 20, carrying reusable debris combined with dust and dirt to duct 14. An approximate velocity of 5000 ft. per minute is an optimal speed at which the filter system carries unfiltered air through the system. A deflector 16 directs the air downwardly into the inner tube 32 which is composed of a mesh material such that air and dust particles can easily migrate to the annular space 33, but large particles and debris are retained therewithin. A second air drawing system or dust fan is disposed adjacent the lower duct 36 of the initial filter system. The dust fan is intermittently operated and creates a negative air pressure within the initial filter system. Air and dust escape through the coarse mesh comprising the wall of the inner bag 32, to the annular space 33 between inner and outer bags 32 and 34 due to the draw created within the annular space by operation of the dust fan. 
     Paper fiber and debris, by gravity and momentum created when air is deflected, travel downwardly inside the inner bag 32. Extending upwardly through the hole 38 of the lower duct connected to steel band 41 is a passage chute 46 which connects the interior space of the inner tube 32 to a baler 50. Reusable debris and fiber falls through the inner tube 32 to the passage chute 46 and into the baler 50. A ram 52 extends forwardly to compact the debris within the baler. 
     The outer bag 34 is made of a fabric material such as a non-woven polyester or tight weave fabric, so that some air can migrate through outer bag wall 34, but dust particles remain therewithin. Thus, some air escapes from the initial filter stage returning directly to the work environment, leaving dust particles caked on the inner wall of the outer tube 34. 
     The remaining dust and air from the initial filter are passed through the duct 36. The lower doughnut shaped duct 36 is capped around the &#34;doughnut&#34; portion which defines the annular space 33 with a perforated steel grid 54. A collar 56, having walls sloping inwardly toward the hole 38 of the duct 36 is located beneath the steel grid 54. The top of the collar is concentric with the steel grid 54. The bottom of the collar approaches but does not contact the inner steel band 41 forming the duct hole 38. The bottom of the collar is eccentric with the hole 38 of the duct 36 formed such that an eccentrically shaped gap 58 is formed between the bottom of the collar 56 and the inner steel band 41 of the duct with said gap 58 being narrow on one side of the duct 36 and gradually widening as it extends to the opposite side. Located adjacent the doughnut shaped duct 36 at the point where the gap 58 between the collar 56 and the inner steel band 41 is narrowest, is an exit pipe 62 which connects the lower doughnut shaped duct 36 to the dust fan 60. By means of the collar 56 within the duct 36, air and dust are drawn uniformly through the steel grid 54 by the dust fan 60 thereby exiting the initial filter 30. The widening gap 58 allows the suction to be increased along the portions of the duct 36 furthest from the dust fan 60. The dust fan 60 then expels the dust laden air through a second delivery pipe 64 to a secondary filter system 70. 
     The secondary filter sYstem 70 has a plurality of filter bags 72 hanging from a frame 74. Each secondary filter bag 72 has a top portion 76 and a bottom portion 78 connected by a hollow support drum 80. The support drums 80 are connected to the second delivery pipe 64. Dust laden air is blown into the secondary bags 72 which are made of a flexible fabric material. Clean air escapes through the cloth wall of the top portion of the secondary bag 76 while dust collects on the inner wall of the top portion of the bag 76 and drops to the bottom portion 78. When the bottom portion of a secondary bag 74 is full it can be removed and emptied. 
     At both filter stages 30 and 70, dust and/or fiber and debris is caked on the inner wall of a filter bag and then drops off to be drawn and collected for removal. Caked dust is forced to drop by palpitations of both the inner and outer bags 32 and 34 and the secondary bags 72. Palpitations are achieved by creating positive and negative air pressure throughout the system. The system fan 20 is operated continuously, while the dust fan is periodically cycled on and off, changing the amount of air pressure in each of the bags causing palpitations, and thereby releasing dust and/or paper caked on the wall surfaces. 
     When the dust fan 60 is cycled off, a positive air pressure is created in the initial filter system, expanding the inner and outer bags 32 and 34 of the initial filter system. The secondary filter bags 72 retract simulatneously with the expansion of the initial filter system. Restarting the dust fan causes the outer bag 34 to retract, thereby causing dust to drop from the walls to be sucked through the steel grid 54 and the secondary bag to expand. The cycle-off time on the dust fan is actuated by a limit switch 100 on the baler which activates the ram 52 to move forward. As the ram moves forwardly the chute 46 is sealed to avoid dust falling into the baler when the dust fan 60 is not operating and drawing air through the annular space 33. 
     On the secondary bag 72, an elastic band 82 is placed around the upper portion 76 of the bag. The band 82 contracts when the dust fan is cycled off and the bag retracts, thereby aiding in the palpitation of the secondary bag 72. When the dust fan is operating, a positive air pressure is created within the secondary bags such that the clean air is released to the atmosphere through the fabric of the bags. No exhaust is necessary for the system since all air is released through the outer bag wall or the secondary bag during periods when the bags are independently inflated. 
     From the foregoing detailed description of the preferred embodiment it is seen that a method and apparatus for filtering air and separating dust from reusable waste is provided which collects conditioned unfiltered air from the environment and returns it in a filtered state without removing the air from the work environment thereby retaining its conditioned property. Reusable waste is collected free of dust and dirt, and compacted into a baler for recycling while dirt and dust are separately collected for disposal. The invention is a compact filter system for an industrial environment which maintains a clean atmosphere while reclaiming valuable, reusable waste products. 
     Many modifications are contemplated within the design of the preferred embodiment. For instance, as one goal of the present invention is to maintain the temperature of conditioned air, thus requiring filtering within the internal work environment, filter bags of varying heights and capacities may be used to accommodate the individual plant needs. It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same and that various changes in size, shape, material, arrangement and assembly method of parts may be made without departing from the original spirit of the invention or the scope of the subjoined claims.
A compact pneumatic air filter system for filtering conditioned air laden with dust and reusable debris is disclosed, which has an initial filter stage for collecting reusable debris from air and separately storing it for reuse, and a secondary filter system for collecting remaining dust from air for disposal and re-releasing conditioned air to a work environment. The system utilizes alternating positive and negative air pressures to move debris and dirt to appropriate storage spaces within the system, and to move filtered air back into the work environment by migration through filter walls, thereby retaining the conditioned property of the filtered air.