Surface sweeping machine
TECHNICAL FIELD 
     The present invention relates to surface maintenance equipment and more particularly to surface maintenance equipment utilizing vacuum pumps for drawing a vacuum stream through such equipment. The present invention relates to such equipment including a filter for removing dust from such stream prior to passage through the vacuum pump. 
     BACKGROUND OF THE PRIOR ART 
     A wide variety of machines is available for use in maintenance of surfaces such as floors, parking lots and streets. These maintenance machines generally include sweeping machines and scrubbing machines. The sweeping machines utilize fans or pumps to draw a vacuum in the brush housing thereby minimizing dusting problems around the sweeping area. A problem which has been long existent in the prior art, is the accumulation of dust on the filter. As the dust accumulates, it tends to block the filter and create a substantial pressure differential between the upstream side of the filter and the downstream side of the filter. Such blockage reduces the dust controlling efficiency of the equipment. Many attempts have been made in the past to overcome such blockage problem generally by vibration or shaking of the filter. Such arrangements have improved the efficiency by removing the dust accumulations to a certain extent. The shaking of the filter, however, has not been as effective in removing the dust as would be desirable. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides a sweeper which may include a cylindrically shaped rotatable brush, a brush housing, a hopper and a vacuum pump. The brush housing surrounds a portion of the brush. The hopper opens from the brush housing. The vacuum pump draws a partial vacuum stream through the brush housing and generally also through the hopper. A filter is located between the hopper and the vacuum pump. The filter is planar in general overall configuration and includes a pleated filter medium. A striker is provided with repeatedly engages the upper edge of the pleats of the filter medium to create a shock wave across the filter medium thereby removing accumulated dust. 
    
    
     IN THE DRAWINGS 
     FIG. 1 shows a perspective view of the present invention; 
     FIG. II shows a top plan view of the filter structure of the present invention; 
     FIG. III shows a cross sectional view of the filter structure taken along the lines III--III in FIG. II; 
     FIG. IV shows a cross sectional view taken along the lines IV--IV in FIG. II; and 
     FIG. V shows a modification of a portion of the filter structure of FIG. IV. 
    
    
     The present invention as illustrated in FIGS. I-IV relates to surface maintenance equipment commonly called sweepers. The sweeper 10 of the present invention may be generally of conventional design including a body portion 11 supported on a plurality of wheels such as 12. The body 11 may have a seat 13 on which an operator may ride and a steering mechanism 14 for control of the direction traversed by the equipment. The sweeper 10 has a housing 16 which contains a filtering element 17 as illustrated in FIG. II. In this instance, the filter element 17 may be disposed in an inclined position, however, having a substantial horizontal component. 
     Various conventional aspects of the sweeper 10 are not specifically illustrated. For example, a vacuum pump is disposed within the body 11 for drawing a partial vacuum stream through the system. Also, a cylindrical brush is disposed beneath the housing 11 and in contact with the surface to be swept. The filter structure 17 may include a metal frame 18 which extends around the entire periphery of the panel filter. The frame 18 may be of light gauged metal such as aluminum. The filter 17 further includes a pleated panel filter medium 19 which is mounted in the frame 18. If desired, a perforated sheet metal member 21 may be disposed over the pleated panel 19. 
     The filter 17 may be suitably mounted in a portion 22 of frame 11. In other words, a well 23 may be defined in the frame 22 for reception of filter 17. Further, suitable structure such as the screw and tabs 24 may be provided to secure the filter in place. 
     A striker member 26 may be superimposed over the filter 17. The striker 26 includes at least one and preferably two straps such as 27, 28 which are in contact with the upper surface of the filter 17. The straps 27, 28 may be of any suitable material such as spring steel. The striker strap 27 may be secured at one end by screws 29 to the body member 22. The other end of strap 27 is free. The strap 28 is secured to the oposite side of body portion 22 such as by screws 31. The other end of strap 28 is free. The straps 27 and 28 may be in contact with the perforated sheet 21 or alternatively, if such a sheet is not present, straps 27 and 28 may be in direct contact with the upper edges of the pleats of filter medium 19. 
     The striker 26 has an electrically operated motor 32 which is mounted on a cross member 33 by bolts 30. Cross member 33 may be secured to the middle portion of straps 27, 28 such as by bolts 34 and 36. The ends of the straps 27, 28 and the cross member 33 may extend over the frame 18 of filter 17. The electrical motor 32 carries an eccentric weight 37. 
     The lower side of the filter 17 may communicate with the hopper of the sweeper 10. Alternatively, the lower side of filter 17 may communicate with the brush housing. The upper side of filter 17 communicates with a plurality of ducts 41, 42, 43 and 44 which lead to the vacuum pump. A cover 46 may be disposed over the filter 17 and striker 26 to provide an air tight chamber. A cavity 47 may be provided in cover 46 in which the electric motor 32 may be disposed. The cover 46 may be suitably held in place by screws 48. The spacing between cover 46 and the filter 17 is sufficient to permit appropriate movement of the motor 32 with an eccentric weight 37 as well as movement of the striker straps 27 and 28 as illustrated in FIGS. III and IV. 
     FIG. V illustrates a modification of the filter structure of FIG. IV. The filter structure 117 of FIG. V may be identical to that of FIG. IV with the exception that the ends of the striker straps, such as 127, are partially restrained in their upward movement. The end of strap 127 may be restrained by the stop 125 which is bolted to body member 122. The degree of restraint may be varied as desired. Of course, various other modifications may be made without departing from the broader scope of the present invention. 
     OPERATION OF THE INVENTION 
     Although operation of the invention would be apparent from the preceding description of the invention, it will be further detailed hereinafter in order to assure a more complete understanding of the present invention. During normal operation, an operator sits on the seat 13, starts the motor or engine and drives the sweeper 10 along the path to be swept. The operator controls the direction in which the sweeper moves by suitable manipulation of the steering wheel 14. The steering wheel 14 and associated mechanism controls the direction of the wheels such as 12. When the sweeper 10 is placed in operation, the cylindrical brush is rotatably driven to sweep up debris such as dirt and dust. Also, when the sweeper 10 is placed in operation, the vacuum pump is operated to draw a partial vacuum in the brush housing, on through the hopper and subsequently through the filter 17. The vacuum stream is then drawn through the ducts 41, 42, 43 and 44 to the vacuum pump. As a vacuum stream is drawn, of course, dust particles are stopped by the filter medium 19 and a layer of fine dust or dirt is accumulated on the lower surface of such filter medium 19. Once dust or dirt debris begins to collect on the filter medium 19, the striker 26 may be placed in operation by closing the electrical switch controlling current to motor 32. As the motor 32 rotatably drives the eccentric weight 37, the motor 32, the cross member 33 and the straps 27, 28 begin to move. As is illustrated in FIG. III, the eccentric weight may first move one end of cross member 33 upwardly, namely, end 33a, with the other end of cross member 33, namely, end 33b, remaining in contact with the filter 17. As the eccentric weight continues to rotate end 33a returns to engagement with filter 17 and the end 33b moves upwardly. In some instances, the cross member 33 may remain parallel with the filter 17 while moving up and down. The cross member 33 moves the center portions 27a and 28a of straps 27 and 28 alternately in an upward direction, thus, alternately raising and lowering the straps 27 and 28. FIG. IV illustrates the configuration of the movement of one of the straps 27. As illustrated, this configuration is in the form of a sine wave which produces a slapping like motion which rolls across the filter medium 19. 
     It has been found that very efficient removal of dust and dirt particles is obtained using the striker shown in the present invention. It is to be recognized that various modifications may be made in the details of the embodiment illustrated in FIGS. I-IV and in FIG. V without departing from the broader scope of the present invention. For example, one may provide a single strap rather than a pair of straps. Alternatively, additional straps may be added if so desired.