Abstract:
A filter cleaning mechanism for a cylindrical filter within a filter box of a surface maintenance machine having a shaker plate engaging a top end of the filter and having vibrations induced via a motor and eccentric mass combination. In one example, the motor and eccentric mass are mounted to a hinged cover plate via a vibration isolating connection. A pair of slot structures may limit movement of the filter to a generally vertical direction relative to ground.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. 119(e) from provisional U.S. Patent Application No. 60/893,356 filed Mar. 6, 2007 the contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure is directed to air filtration systems. More specifically, the present disclosure is directed to a filter shaking mechanism and method of use for extending the useful life of air filters on surface maintenance machines and the like. 
       BACKGROUND OF THE INVENTION 
       [0003]    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. 
         [0004]    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. 
         [0005]    The dust thus removed from the air stream builds up on the filters and in time will block off the airflow through them unless they are periodically cleaned, so a cleaning means is commonly provided which the machine operator must use when needed. Generally the operator must be watchful for dust coming out from under the skirts, which indicates that airflow has been reduced by dust plugging the filters. He or she then must stop the machine, shut off the air flow, and activate the cleaning means. This is most commonly a mechanism that shakes or jolts the filters for a predetermined time to shake off the dust, which falls to a collection tray for later removal. Then the air flow is re-started and the machine operation is resumed. This method is effective when properly carried out, but it takes time away from productive operation. Some operators carelessly neglect doing it when needed, so that dust escapes from the machine while it is operating and settles on objects in the area. Also, filters that are allowed to get too dirty cannot be as effectively cleaned and must be replaced more often than properly serviced filters. 
         [0006]    To eliminate these shortcomings it has been desirable to provide an automatic filter cleaning system that requires no attention from the operator. There have been efforts in that direction. U.S. Pat. Nos. 4,637,825 and 4,756,727 each show a sweeper filter that is automatically cleaned while the sweeper is operating by directing pulses of compressed air sequentially against segments of the filter from its clean side to blow off dust. U.S. Pat. No. 5,013,333, incorporated by reference herein, shows a sweeper filter that is automatically cleaned while the sweeper is operating by application of periodic activation of a mechanical shaker mechanism. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed to a filter cleaning system for a mobile surface maintenance machine and the like. One or more filters are provided within a filtration system. The filter(s) can be cylindrical filters. The filtration system can be vacuum-based. As dust accumulates on the filter surfaces it offers increasing resistance to the air flow, which results in increasing differential air pressure across the filter. This may be sensed by a differential pressure switch which initiates a cleaning cycle when a predetermined differential pressure level is reached. This level may be set low enough to assure adequate dust control for the machine and long life for the filters. At the same time it does not subject the cleaning apparatus or the filters to the wear and tear of continuous cleaning cycles. It is responsive to the work environment, cleaning more often in very dirty conditions and less often in cleaner places. 
         [0008]    In one embodiment, a cylindrical filter shaking mechanism includes an eccentric mass mounted on an electric motor which is in contact with the filter box. The cleaning cycle includes a mechanical shaker device which repeatedly shakes the filter, knocking off the dust on it, which falls into a collection tray or platform. The entire cleaning cycle operates manually or automatically with no attention from the operator. 
         [0009]    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. 
         [0010]    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  
         [0011]    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: 
           [0012]      FIG. 1  is a perspective illustration of one embodiment of a cleaning machine utilizing a filter cleaning system in accordance with the present invention. 
           [0013]      FIGS. 2 and 3  are perspective illustrations of the prefilter chamber and filter box of the cleaning machine of  FIG. 1 . 
           [0014]      FIG. 4  is an enlarged portion of  FIG. 3  contained within circle C 4 . 
           [0015]      FIG. 5  is a perspective illustration of the prefilter chamber and filter box of  FIG. 1 . 
           [0016]      FIG. 6  is an enlarged portion of  FIG. 5  contained within circle C 6 . 
           [0017]      FIG. 7  is a perspective view of a cover component of the embodiment of  FIG. 1 . 
           [0018]      FIG. 8  is a perspective view of a housing of the embodiment of  FIG. 1 . 
           [0019]      FIG. 9  is a perspective view of a filter and filter shaker mechanism of  FIG. 1 . 
           [0020]      FIG. 10  is a cross sectional view of portions of  FIG. 9 . 
           [0021]      FIG. 11  is a perspective illustration of the machine of  FIG. 1 . 
           [0022]      FIG. 12  is a depiction of components of  FIG. 1  during operation. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    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. 
         [0024]    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. 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. 
         [0025]      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. Additional features of the prefilter  17  assembly can be found by reference to U.S. Ser. No. 60/893,560, entitled “Counter Rotating Cyclonic Filter”, and incorporated by reference herein. 
         [0026]    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 . 
         [0027]    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 . 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). Additional details of filter box  18  may be found in Applicants&#39; application Ser. No. ______, for “External Filter Chamber” filed on equal date herewith and incorporated by reference herein. 
         [0028]      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 . 
         [0029]    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. 
         [0030]    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 . 
         [0031]    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 . 
         [0032]      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 . 
         [0033]      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. 
         [0034]      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 . 
         [0035]      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. 
         [0036]      FIG. 11  illustrates hinged cover plate  41  and connected components in an opened orientation, such as during inspection or replacement of filter  19 . Clamp assemblies  43  include knobs  111  which are secured on threaded fasteners  112  held above filter box cover  81 . As depicted, removal of knobs  11  from threaded fasteners  112  permits opening of cover plate  41  and access to filter  19 . 
         [0037]      FIG. 12  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. 
         [0038]    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 within a front hopper of machine  10  and debris falling out of filter box  18  is captured within the front hopper. 
         [0039]    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. 
         [0040]    As a cost reduction a pressure switch and control system might be eliminated, leaving only a manual pushbutton to activate shaker motor  44 . In this configuration the operator would still have to watch for signs of dirty filters, such as dust starting to come out from under the brush skirts. At that point he or she could push the pushbutton and the cleaning cycle would proceed t its completion. This would retain the advantage of cleaning the filters without interrupting the sweeping operation and without shutting off the dust control air flow, and it would simplify the operator&#39;s job. It would also be possible to replace the pressure switch with a timer, while retaining all other features of the system as described. The cleaning cycle could be activated by the timer at predetermined time intervals. This would provide filter cleaning with no attention from the operator and without interrupting sweeping or dust control. 
         [0041]    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.