Abstract:
A filter system for a surface maintenance machine having a hopper assembly for receiving brush-thrown debris including a cyclonic separator for separating dust and debris from air drawn through the hopper via vacuum action. The cyclonic separator may include multiple cyclone and may be in fluid communication with the hopper assembly so as to periodically receive dust and debris exiting the filter system.

Description:
This application claims priority under 35 U.S.C. 119(e) from provisional U.S. Patent Application No. 60/893,560 filed Mar. 7, 2007 the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure is directed to filtration systems for a mobile surface maintenance machine. More specifically, the present disclosure is directed to a filtration system utilizing a cyclonic filter assembly as a filter stage. 
     BACKGROUND OF THE INVENTION 
     Over the years various kinds of machines have been developed for cleaning and maintaining floors inside buildings, and paved outdoor areas such as streets, sidewalks and parking lots. They include such machines as rotary broom sweepers, vacuum sweepers, scarifiers, burnishers, polishers and scrubbers. For our purposes here they can be divided into machines which apply water to the surface being maintained and machines which operate dry. We are concerned with the latter, which would include many vacuum sweepers, scarifiers, and rotary broom sweepers. They all share one problem which is addressed by this invention. In their normal operation they tend to stir up dust from the surface being maintained. If it is not controlled, this dust is highly objectionable. 
     On many of these machines the problem has received one general solution. The functional tool which generates the dust, such as a rotary broom, a scarifier head, or a vacuum pickup, is provided with a cover and surrounded by walls which have rubber skirts that hang down almost to the surface being maintained. An on board exhaust blower continuously pulls air from the tool chamber thus created so there is a sub-atmospheric air pressure within it which eliminates outflow of dusty air from under the skirts. The blower exhausts this air to atmosphere. One or more air filters are placed in this air path, either upstream or downstream from the blower, to remove dust from the air before it is released so the discharge to atmosphere will be dust free. 
     An aspect of the present invention is to provide a cyclone dust-collector within a debris hopper of a surface cleaning machine having an improved construction which is capable of separating and collecting the fine particles efficiently. 
     The above aspect is achieved by providing a cyclonic prefilter which filters out dust and dirt from drawn-in air. In one example, the cyclonic prefilter includes multiple cyclone units for centrifugally separating the dust and dirt from the drawn-in air, and a cover unit defined as the upper housing of the cyclonic prefilter, for allowing the cyclone-filtered air to fluidly communicate with an air inlet of a filter box for subsequent filtering. 
     The cyclone units may comprise an air guide wall for inducing rotational flow to the air stream. A plurality of the funnel-shaped members may be arranged in a predetermined pattern, forming a multiple cyclone unit. The top housing may comprise a first cover connected to the upper portion of the multiple cyclone unit, and having centrifugal passages for guiding the air discharged from the cyclones to be a vortex, and discharge holes through which air exiting from the discharge holes is drawn. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a filtration system for a mobile surface maintenance machine utilizing a cyclonic air filter stage. The cyclonic filters may prefilter air which subsequently passes through a primary filter. The filtration system can be vacuum-based. In one embodiment, the cyclonic filter stage is combined within a debris hopper to allow dust and debris to move out of the cyclonic filters and be deposited within the debris hopper. The communication of dust and debris may be achieved via one or more flaps which respond to pressure variations across the flap in order to open or close the flap. 
     In one embodiment, the prefilter includes a bank of cyclone filters. Air flow to each of the bank of cyclone filters may be controlled by an air channel. In one embodiment of the present invention some of the air channels route air to establish air flow in opposite directions, e.g., a clockwise and counter clockwise rotation of the air within some of the cyclones. A vacuum fan may be connected to a remote filter box housing. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is a perspective illustration of one embodiment of a cleaning machine utilizing a filter cleaning system in accordance with the present invention. 
         FIGS. 2 and 3  are perspective illustrations of the prefilter chamber and filter box of the cleaning machine of  FIG. 1 . 
         FIG. 4  is an enlarged portion of  FIG. 3  contained within circle C 4 . 
         FIG. 5  is a perspective illustration of the prefilter chamber and filter box of  FIG. 1 . 
         FIG. 6  is an enlarged portion of  FIG. 5  contained within circle C 6 . 
         FIG. 7  is a perspective view of a cover component of the embodiment of  FIG. 1 . 
         FIG. 8  is a perspective view of a housing of the embodiment of  FIG. 1 . 
         FIG. 9  is a perspective view of a filter and filter shaker mechanism of  FIG. 1 . 
         FIG. 10  is a cross sectional view of portions of  FIG. 9 . 
         FIG. 11  is a depiction of components of  FIG. 1  during operation. 
         FIGS. 12 and 13  are depictions of a filter box and prefilter during machine operation. 
         FIG. 14  is a perspective view of the prefilter and filter box of the machine  FIG. 1 . 
         FIG. 15  is a perspective view of the prefilter and filter box of  FIG. 14 , with a portion of the prefilter removed. 
         FIG. 16  is a cross sectional view of the prefilter and filter box of  FIG. 15  taken through a lower prefilter housing. 
         FIG. 17  is a cross sectional view of the prefilter and filter box of  FIG. 15  taken through a lower prefilter housing. 
         FIG. 18  is a perspective view of the upper housing of the prefilter of  FIG. 14 . 
         FIG. 19  is a cross sectional view of the prefilter and filter box of  FIG. 14  taken through the prefilter housings. 
         FIG. 20  is a cross sectional view of the prefilter and filter box of  FIG. 14  taken through the prefilter housing. 
         FIGS. 21-23  are depictional cross sectional views of the prefilter and filter box of  FIG. 14  taken through the prefilter and filter box assembly. 
         FIG. 24-26  illustrate the hopper assembly positioned in a dumping orientation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A conventional forward throw rotary broom sweeper will be used by way of example in the following description of the invention. However, it should be understood that, as already stated, the invention could as well be applied to other types of mobile surface maintenance machines, such as, for example, other types of rotary broom sweepers, scarifiers, and various types of vacuum sweepers. 
     With reference to  FIG. 1 , there is shown an industrial sweeping machine  10 . As illustrate, machine  10  is a forward throw sweeper with an intended direction of motion indicated by arrow marked FM. Machine  10  could as well be an over-the-top, rear hopper sweeper, a type which is also well known in the art. Machine  10  has a rotating cylindrical brush  12  for sweeping debris from a floor or other surface into a debris hopper  13 . Hopper arms (not shown) allow hopper  13  to be lifted during a dumping procedure. The brush chamber generally encloses brush  12  under skirts  14  to control air flow around brush  12 . The skirts  14  largely contain within the brush chamber any dust stirred up by the brush  12 . To complete the dust control there is a suction blower or vacuum fan  16  which exhausts air from the brush chamber to atmosphere in an airflow path shown by the arrows in  FIG. 1 . Vacuum fan  16  is housed within filter box  18  and includes an impeller which is driven by the machine&#39;s hydraulic system. Vacuum fan  16  maintains a sub-atmospheric pressure within the brush chamber so that air is drawn in under the skirts rather than flowing out. Thus relatively little dust escapes from around skirts  14 . During machine  10  operation, vacuum fan  16  draws debris and dust-entrained air through prefilter  17  and filter  19  contained within filter box  18  prior to exhaust. Prefilter  17  is located within debris hopper  13  and is separated from filter box  18  during, for example, a debris hopper  13  lift and dump operation. Shaker mechanism  40  is provided on filter box  18 . Periodic activation of shaker mechanism shakes filter  19  to dislodge dust and debris. Various components of machine  10  have been left out of  FIG. 1 , e.g., the drive engine, housings and operator station have been omitted to improve understanding of the aspects of the present invention. Additional examples of surface maintenance machine suitable for adaptation in accordance with the present invention are found in U.S. Pat. Nos. 5,254,146 and 5,303,448, each patent being incorporated by reference herein for all purposes. 
       FIG. 2  is a perspective view of prefilter  17  and filter box  18 . Filter box  18  houses cylindrical filter  19  as described in more detail hereinafter. Dust and debris-laden air is drawn by vacuum action into prefilter openings  20 . Together the prefilter  17  and filter box  18  remove dust and/or debris from the air stream so the vacuum fan  16  will exhaust relatively clean air to atmosphere during machine  10  operation. Prefilter  17  may comprise a bank of cyclonic filters through which dusty air passes causing separation and retention of at least some of the larger dust particles and debris. 
     In a preferred embodiment, filter box  18  includes a cylindrical pleated media filter  19 , such as are manufactured, for example, by Donaldson Company, Inc. of Minneapolis, Minn. Filter  19  has a pleated media, with the pleats running parallel to the centerline of the cylinder, which makes them vertical when installed as shown. The pleated media is surrounded with a perforated metal sleeve for structural integrity. Outside the metal sleeve may be provided a fine mesh sleeve (not shown) woven from a slippery synthetic filament which stops the coarser dust and sheds it easily during a filter cleaning cycle. The ends of the cylindrical filter are open. Other filter technologies could be utilized in alternative embodiments of filter box  18 . 
     A preferred example of the invention utilizes a cylindrical pleated media filter. However, the invention will accommodate air filters of other types. An alternative design includes two or more flat panel pleated media filters, and other known types of air filters may also be successfully employed. These might include, for example, cloth filters formed into bags, envelopes or socks, which are well known types of filters in the field of air filtration. 
     As shown in  FIG. 3 , filter box  18  has an intake opening  22  at the front of the machine  10  to admit air from the prefilter assembly  17 . As illustrated a flexible coupling, such as foam, is utilized to provide fluid communication between prefilter  17  and filter box  18 . Dust and debris captured by filter box  18  is removable via a lower debris outlet port  23 . Filter air is directed out of filter box  18  at air outlet  24 . Upon deactivation of the vacuum system, an accumulation of dust and debris passes through a seal at debris outlet port  23  and into the machine hopper  13  (not shown). During machine  10  operation, this the debris outlet port seal is kept closed by vacuum action. Filter box  18  includes vacuum fan motor  30  which is coupled to the vacuum impeller (not shown). 
       FIG. 4  is an enlarged portion of the filter box  18  showing details of shaker mechanism  40  as indicated by circle, C 4 , in  FIG. 3 . A hinged cover plate  41  is secured on top of filter box  18  by two hinge assemblies  42  and two clamp assemblies  43 . When clamp assemblies  43  are released, cover plate  41  and connected components rotate about the hinges  42  to allow access into filter box  18 . Cover plate  41  has a large generally rectangular opening in it corresponding to the general location of the cylindrical filter  19 . 
     Shaker mechanism  40  includes an electric motor  44  coupled to an eccentric mass  45 . Electric motor  44  is coupled to a shaker plate  47  which engages the top of filter  19 . Shaker mechanism  40  also includes a vibration-isolating motor mount assembly which permits shaker plate  47  to vibrate generally independently relative to cover plate  41  during a filter shaking procedure. 
     Referring to  FIG. 5 , the motor mount assembly includes a motor clamp  50 , motor saddle  51 , and a pair of slide plates  52  secured to upwardly directed flanges  53  of hinged cover plate  41 . Electric motor  44  and eccentric mass  45  have been removed in this illustration.  FIG. 6  is an enlarged portion of the filter box  18  assembly showing details of shaker mechanism  40  as indicated by circle, C 6 , in  FIG. 5 . 
     Motor  44  is secured between motor clamp  50  and saddle  51 . Saddle  51  is rigidly coupled to shaker plate  47 . Saddle  51  is movably coupled to slide plates  52  via a pair of fasteners  61 . In this example, fasteners  61  are free to move within slots  62  to permit a generally vertical displacement of the saddle  51 , clamp  50 , motor  44  and eccentric mass  45  during a filter shaking procedure. Washers  64  slide against slide plates  52  as limited by slots  62 . 
       FIG. 7  illustrates hinged filter cover plate  41  and slide plates  52 . Fasteners (not shown) pass through openings  71  and secured slide plates  52  to flanges  53  of cover plate  41 . Slots  62  extend through generally equally sized openings in slide plates  52  and flanges  53 . In one example, slide plates  52  are of a durable material with substantially improved wear resistance relative to cover plate  41 . 
       FIG. 8  illustrates housing  80  of filter box  18  and filter box cover  81 . Cover  81  is secured to housing  80  in this example via threaded fasteners. Pin-shaped components  82  are included within hinge assemblies  42  and support cover plate  41  and connected components when cover plate  41  is opened, such as during a filter exchange. 
       FIG. 9  illustrates components of shaker mechanism  40  and filter  19 . In this example, shaker plate  47  is in generally direct contact with one end of filter  19 . The opposite end of filter  19  is supported by a base within housing  80  (not shown). Upper annular seal  90  and lower annular seal  91  control air flow through top openings of filter  19 . 
       FIG. 10  illustrates a cross sectional view of the shaker mechanism  40  and filter  19  of  FIG. 9  in an operational orientation. Top cover  100  is held between a top surface of filter  19  and is in direct contact with shaker plate  47 . Upper annular seal  90  is in contact with a lower surface of hinged cover plate  41 . Forces generated during rotation of motor  44  and eccentric mass  45  are directly applied to the top of filter  19  and cause filter  19  to shake and dislodge dust and debris on filter  19  surfaces. 
       FIG. 11  is a cross-sectional operational depiction of filter box  18  with airflows generally indicated by arrows. In operation, dusty airflow passes first through prefilter  17  and enters filter box  19  at intake opening  22 . Air is drawn through filter box  18  upon activation of impeller  121  which is driven by vacuum fan motor  30  and exhausted toward the rear of the machine at air outlet  24 . This is a preferred arrangement because the air is cleaned before it passes through the vacuum impeller, which reduces abrasive wear on the impeller. However, some sweepers pass the air first through the blower and then through the filters. This arrangement can also be accommodated by the invention. 
     During machine  10  operation, dust and debris accumulates near debris outlet  23 . Seal  123  is held closed by vacuum action during machine  10  use. In the absence of impeller  121  rotation, debris forces open seal  123  and falls out of hopper box  18  through opening  124 . In one example, opening  124  is located near an end of extension conduit  125  which is at least partially located within front hopper  13  of machine  10 . Dust and debris falling out of filter box  18  is directed through extension  125  and drops through opening  124  onto a surface of hopper  13 . 
     During a filter shaking procedure, the motor driven eccentric mass  45  imparts a vibratory motion to filter  19  to dislodge an accumulation of dust and debris. Various means for initiating a cleaning cycle can be envisioned. In one preferred embodiment, shaker motor  44  is activated after each time the vacuum system is turned off. In another embodiment, shaker motor  44  is controlled via a machine controller in response to differential pressure changes across filter  19 . A pressure switch for sub-atmospheric pressure may also be installed at filter box  18 , with one of its pressure ports connected to the duct leading to the exhaust fan and its other pressure port open to atmosphere. In normal service, as dust gradually accumulates on the filters, the differential pressure will rise. When it reaches a predetermined value the pressure switch will signal a controller to initiate an automatic filter cleaning cycle. 
     Details of operation of filter box  18  and prefilter  17  may be found in copending applications U.S. Ser. No. 12/043,945 entitled “External Filter Chamber”, U.S. Ser. No. 12/045,948 entitled “Integral Vacuum Fan Housing”, and U.S. Ser. No. 12/043,932 entitled “Filter Cleaning Apparatus”, each document being incorporated by reference herein for all purposes. 
     During machine  10  operation, dust and debris accumulates near debris outlet  23 . Seal  123  is held closed by vacuum action during machine  10  use. In the absence of impeller  121  rotation, debris forces open seal  123  and falls out of hopper box  18  through opening  124 . In one example, opening  124  is located near an end of extension conduit  125  which is at least partially located within front hopper  13  of machine  10 . Dust and debris falling out of filter box  18  is directed through extension  125  and drops through opening  124  onto a surface of hopper  13 . 
     During a filter shaking procedure, the motor driven eccentric mass  45  imparts a vibratory motion to filter  19  to dislodge an accumulation of dust and debris. Various means for initiating a cleaning cycle can be envisioned. In one preferred embodiment, shaker motor  44  is activated after each time the vacuum system is turned off. In another embodiment, shaker motor  44  is controlled via a machine controller in response to differential pressure changes across filter  19 . A pressure switch for sub-atmospheric pressure may also be installed at filter box  18 , with one of its pressure ports connected to the duct leading to the exhaust fan and its other pressure port open to atmosphere. In normal service, as dust gradually accumulates on the filters, the differential pressure will rise. When it reaches a predetermined value the pressure switch will signal a controller to initiate an automatic filter cleaning cycle. 
       FIGS. 12 and 3  are cross-sectional operational depictions of filter box  18  and prefilter  17  showing airflows generally indicated by arrows. In operation, dusty airflow passes first through prefilter  17  and enters filter box  19  at intake opening  22 . Air is drawn through filter box  18  upon activation of impeller  121  which is driven by vacuum fan motor  30  and exhausted toward the rear of the machine at air outlet  24 . In addition to containing cylindrical filter  19 , filter box  18  also defines a vacuum fan housing for drawing air through filter and conduit  131  and directing air out through conduit  132  which has an expanding cross section as conduit  132  travels from impeller  132  to outlet  24 . In one example of the invention, filter box  18  is a rotationally molded polymer component. 
       FIG. 14  is a front perspective view prefilter  17  and filter box  18 . Prefilter  17  includes a top housing  141  and a bottom portion housing. Air inlets  20  are defined along lower surfaces of upper housing  141 . 
       FIG. 15  represent the assembly of  FIG. 14  with top housing  141  removed. Seal  143  functions as a gasket to minimize air leakage at the junction between top and bottom housing  141 ,  142 . Seal  143  includes a plurality of openings permit air to flow between the top and bottom housings  141 ,  142 . In another example, seal  143  may have fewer openings thereby blocking air flow through one or more cyclone filter sections. Threaded stem  144  and nut  145  are used to secure the top housing  141  to the lower housing  142 . Nuts  145  are shown as wing-nuts, though other threaded or non-threaded fasteners may be utilized in another example of the invention. Nuts  145  are accessible from above top housing  141  of prefilter  17 , thereby allowing inspection of prefilter  17  interior without removing the lower housing  142 . 
       FIG. 16  is a cross sectional view of prefilter  17 . Cones  162  form a lower portion of a cyclone filter. In the illustrated example, cones  162  are integrally formed into lower housing  142 . Each cone has a lower aperture  163  through which dust passes during machine operation. Dust collects on an inner surface of lower housing  142  until hopper  13  is cleared during a dumping procedure. 
       FIG. 17  is another cross sectional view of prefilter  17  taken closer to filter box  18  relative to  FIG. 16 . Lower housing  142  also includes cavities  171  which engage a pin formation on a lower surface of top housing  141 . Referring to  FIG. 18 , pin formations  172  are sized to be received into cavities  171  thereby aligning the top and bottom housings  141 ,  142  during assembly or replacement after inspection. 
     As shown in  FIG. 18 , air inlets  20  are defined by guide walls  193  that extend into top housing  141  and spiral in one direction or the other. In the illustrated example, guide walls  193  define spirals extending in clockwise and counter-clockwise directions. Air and dust flowing into inlets  20  is conducted through channels defined by guide walls  193  with the spiral formations creating a rotational air flow at the top openings of cones  162 . Dust and debris is separated from the airflow by a centrifugal effect and falls through openings  163 . Filtered air flows through openings  191  and into the interior of top housing  141 . 
       FIG. 19  is a cross sectional view of prefilter  17  taken through a row of cones  162 . Top housing  141  includes an opening allowing airflow into air inlet  22  of filter box  18 .  FIG. 20  is a cross sectional view of prefilter  17  taken through another row of cones  162 . Openings  200  are defined upon top housing  141 . As described hereinafter, fasteners  144 ,  145  pass through a cavity defined at its upper extent by opening  200 . 
       FIG. 21  depicts an airflow through prefilter  17  and filter box  18 , such as during machine  10  operation. Dusty air enters prefilter  17  at openings  20  and is conducted through spiral-formed portions of top housing  141 , through the cyclone filter elements, and enters the interior of top housing  141 . Partially filter air then flows through inlet  22  prior to being drawn through filter  19  by vacuum action. 
       FIG. 22  depicts the airflow of  FIG. 21  with a larger cut away portion of top housing  141 .  FIG. 23  depicts airflow through cyclone filter elements, such as during machine  10  operation. Dusty air is drawn through openings  20  and conducted through spiral-forming walls  193  to induce a rotational airflow within cones  162  Dust and debris is separated from the air stream and is deposited within lower housing  142 . 
       FIG. 23  is a cross sectional view taken generally through openings  200  of top housing  141 . This drawing illustrates that the top and bottom surfaces of top housing  141  are joined together to define an open cavity at openings  200  into which fasteners  145  and  144  (not shown) are introduced. Fastener  145  engages a seat defined within the open cavity to secure the housing portions together during machine  10  operation. A rotational molding process has been identified as well suited to form both housing portions of prefilter  17 . 
       FIG. 24  illustrates hopper  13  lifted into a dumping orientation whereby dirt and debris exits hopper  13  through opening  241 . During a sweeping operation, brush  11  throws dirt and debris through opening  241 . Hopper  13  is pivots about hinges  252  on machine arms  253  via hydraulic cylinder  254 . As shown in the drawing, filter box  18  and prefilter  17  are separated when the hopper  13  is lifted. Fluid coupling between prefilter  17  and filter box  18  is restored when hopper  13  is lowered. 
       FIG. 25  is another illustration of hopper  13  lifted into an upright orientation. In this view, brush  11  is visible as is extension conduit  125 , through which dust and debris flows from filter box  18  and is captured within hopper  13  during normal operation. As apparent, two couplings are made between hopper  13  and external filter box  18  during normal operation. A first coupling permits dusty air to flow into opening  22  and a second coupling allows dust and debris to flow from filter box  18  through conduit  125  and onto a surface of the hopper  13 . 
       FIG. 26  is another illustration of hopper  13  lifted into an upright orientation relative to filter box  18 . Visible in this view is the outlet  271  of prefilter  17  which mates with a coupling  262  at opening  22  of filter box  18 . Coupling  262  may be a foam or other resilient material for containing airflow within the vacuum system. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.