Patent Publication Number: US-2004045584-A1

Title: Motorized street sweeper

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to motorized street sweeping vehicles.  
       BACKGROUND OF THE INVENTION  
       [0002] Automated street sweeping vehicles are essential equipment for commercial and government organizations. The vehicles are used for cleaning debris from roadways, walkways, parking lots, runways, and many other ground surfaces.  
       [0003] For streets and highways, large sweepers are primarily used. The large sweepers are motorized (typically diesel powered) and can be custom-made or built upon a commercial truck chassis. The large sweepers typically include large main brushes which direct debris onto a paddled conveyor that moves the debris into a large-capacity debris hopper. The large hoppers allow the sweepers to cover greater distances without the need for emptying the hopper. The large brushes allow the sweeper to pick up larger debris (e.g. rocks, tire treads, wood pieces), thus avoiding the need for multiple passes of the sweeper or manual retrieval of the debris.  
       [0004] Although effective, such street sweepers often miss a certain percentage of the debris, even when the sweeper passes directly over the debris. In some cases, the debris bounces around between the brush and conveyor, and can be ejected out from underneath the vehicle. At other times, the debris bounces over the top of the brush and is passed over.  
       [0005] During operation, such sweepers can also generate a dust cloud when sweeping. In some cases, suction is used on side brushes and on the conveyor to control this dust. Regardless, a significant amount of dust is ejected into the atmosphere during sweeping. Besides being a nuisance, the dust is a source of particulate air pollution. In some localities particulate air pollution is a major problem, and municipalities are under government mandates to reduce particulate air pollution.  
       [0006] What is needed is a sweeper that can pick up a higher percentage of road debris, especially large items. Further, the sweeper should reduce the amount of dust ejected into the air. The present invention fulfills these and other needs, and addresses other deficiencies of prior art implementations.  
       SUMMARY OF THE INVENTION  
       [0007] To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a sweeper for a ground surface. The sweeper has a front end, a back end and a forward direction of motion. The sweeper includes a debris mover with an outer surface, a ground contact area, an axis of rotation, a cutoff area, and a recirculation contact area. The ground contact area is defined where the outer surface of the debris mover contacts the ground surface The debris mover rotates about the axis of rotation so that the outer surface of the debris mover moves at least in part towards the front end of the vehicle at the ground contact area. The outer surface of the debris mover moves at least in part upwards at the cutoff area as the debris mover rotates about the axis of rotation. The outer surface of the debris mover moves at least in part downwards at the recirculation contact area as the debris mover rotates about the horizontal axis.  
       [0008] The sweeper also includes a cutoff flap and a recirculation flap. The cutoff flap is mounted forward of the debris mover. The cutoff flap has a distal end adjacent the outer surface of the debris mover along the cutoff area so that a first portion of the debris traveling to the cutoff area is deflected at least in part downward. The recirculation flap is mounted behind the debris mover. The recirculation flap engages the recirculation contact area so that a second portion of the debris traveling to the recirculation contact area is deflected back into the brush.  
       [0009] The sweeper may include debris collector mounted forward of the debris mover and a conveyor flap mounted adjacent a lower edge of the debris collector. The conveyor flap has a distal edge proximate the ground surface. The conveyor flap substantially coves a space defined between a lower edge of the debris collector and the ground surface. A ground gap may be included between the distal edge of the conveyor flap and the ground surface. The conveyor flap may include a plurality of slots at the distal edge. In one arrangement, the distal edge of the conveyor flap is oriented an angle between 40 and 50 degrees relative to vertical.  
       [0010] The sweeper may be configured so that the cutoff area is located between 45 degrees and 140 degrees from the ground contact area. Also, at least a portion of the cutoff flap proximate the distal tip may be oriented between 10 degrees and 30 degrees relative to horizontal. A gap between the distal end of the cutoff flap and the outer surface of the debris mover may be included.  
       [0011] In one configuration, the recirculation flap includes a flexible mounting flap fixably attached to the sweeper. An elongated blade is connected to the mounting flap. An edge of the elongated blade engages the debris mover. In one arrangement, the recirculation contact area is located between 40 degrees and 80 degrees from the ground contact area. The debris mover may include a brush having bristles. A distal end of the recirculation flap may extend substantially within the bristles of the brush.  
       [0012] In another embodiment of the present invention, a method of street sweeping of a debris from a ground surface involves moving a conveyance in a forward direction on the ground surface. A debris mover of the conveyance is rotated to move the debris at least in part forward of the debris mover. The debris is caught on a debris collector facing the debris mover to collect the debris. A first portion of the debris thrown into a space defined between a lower edge of the debris collector and the ground surface is deflected back to recirculate the first portion of the debris back into the debris mover. A second portion of the debris that passes upwards along a forward portion of the debris mover is deflected downwards to recirculate the second portion of the debris back into the debris mover. A third portion of debris that passes downwards along a rear portion of the debris mover is deflected forwards to recirculate the third portion of debris back into the debris mover.  
       [0013] The method may involve drawing a vacuum to move airborne dust from a space surrounding the brush to collect the airborne dust. The method may also involve blocking the airborne dust at the forward portion of the debris mover to prevent escape of the airborne dust therethrough. The airborne dust can also be blocked at the rear portion of the debris mover to prevent escape of the airborne dust therethrough. The airborne dust can further be blocked at the space defined between a lower edge of the collector and the ground surface to prevent escape of the airborne dust therethrough.  
       [0014] In another embodiment of the present invention, a mobile sweeping system is usable for removing a debris from a ground surface. The sweeping system has a forward direction of motion and a sweeping width. The sweeping system further includes a debris moving means moving a debris at least in part forwards across the sweeping width. A debris collecting means catches the debris moved by the debris moving means. A deflecting means covers at least part of a collector clearance space defined between a lower edge of the debris collecting means and the ground surface. The deflecting means deflects a first portion of the debris moved by the debris moving means into the collector clearance space back to the debris moving means. A cutoff means is adjacent to a forward portion of the debris moving means where an outer surface of the debris moving means is moving at least in part upwards. The cutoff means deflects downwards a second portion of the debris passing upwards along the outer surface of the debris moving means. A recirculation means engages a back portion of the debris moving means where the outer surface of the debris moving means is moving at least in part downwards and forwards. The recirculation means deflects a third portion of the debris passing over and behind the debris moving means back to the debris moving means.  
       [0015] The deflecting means may include a distal edge adjacent the ground surface and a substantially flexible portion along the distal edge. The substantially flexible portion can include a plurality of slots along the distal edge. A gap may be included between the cutoff means and the outer surface of the debris moving means. A flexible mounting means can be used to resiliently couple the recirculation means to the sweeping system.  
       [0016] In one configuration, a distal portion of the recirculation means substantially penetrates beneath the outer surface of the debris moving means. The deflecting means can cause a restriction of a flow through the collector clearance space. The restriction of flow prevents release of a portion of airborne dust therethrough.  
       [0017] The sweeper may further include housing means encompassing a rear portion of the debris moving means. The recirculation means causes an air restriction between the debris moving means and the housing means. The air restriction thereby prevents release of a portion of airborne dust of the debris therethrough.  
       [0018] The cutoff means may form an air restriction between the debris moving means and the debris collecting means. The restriction prevents release of a portion of airborne dust of the debris therethrough.  
       [0019] The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0020]FIG. 1 is a cutaway perspective view of a street sweeper vehicle according to an embodiment of the present invention;  
     [0021]FIG. 2 is a side view of the brush, conveyor and flaps according to an embodiment of the present invention;  
     [0022]FIG. 3 is a side view of the brush and recirculation flap showing geometric details according the an embodiment of the present invention;  
     [0023]FIG. 4 is a perspective view of a conveyor flap according to an embodiment of the present invention;  
     [0024]FIG. 5 is a perspective view of a cutoff flap according to an embodiment of the present invention; and  
     [0025]FIG. 6 is a perspective view of a recirculation flap according to an embodiment of the present invention. 
    
    
     [0026] While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail herein. For example, while the title describes a street sweeper, this refers only to a preferred embodiment since the present invention is applicable to all forms of debris gathering equipment. It is to be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.  
     DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS  
     [0027] In the following description of the illustrated embodiments, references are made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration, various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope of the present invention.  
     [0028] Referring now to FIG. 1, a street sweeping vehicle, generally indicated by reference numeral  100 , has a front end  102  and back end  104 . The front end  102  of the vehicle includes a cab section  103  where an operator sits A debris mover, typically a cylindrical pickup brush and generally indicated by reference numeral  106 , is mounted near the back end  104  of the vehicle  100 . The brush  106  includes bristles  108  and a hub  110 . The horizontal axis of the brush  106  is oriented substantially perpendicular to the direction of forward motion of the vehicle  100 , indicated by the bold, straight arrow above the vehicle  100 . It is appreciated, however, that the brush  106  can be oriented skewed (i.e. non-perpendicular to forward motion) to push debris both forwards and sideways.  
     [0029] The brush  106  is powered and rotates about its axis in the direction indicated by the bold, curved arrow. It is appreciated that the brush  106  can be rotated opposite the direction indicated in Fig. 1 , although such a rotation is likely to be less effective. The brush  106  can rotate at varying speeds, typically in the range of  75  to  150  rpm. The brush  106  in this example has an outer diameter ranging from 36 to 18 inches (91 to 45 cm), the outer diameter decreasing with wear of the bristles  108 . The outer surface of the brush  106  (i.e. at the tip of the bristles  108 ) contacts the ground surface  112  at a contact surface  114 . The brush  106  throws debris from the ground surface  112  to a debris collector (in this example a conveyor), generally indicated by reference numeral  120 .  
     [0030] The conveyor  120  includes a belt  122  with paddles or cleats  124  mounted along an outer surface at regularly spaced intervals. Debris is thrown by the brush  106  onto a collecting surface  123  of the belt  122 . The belt  122  rotates in a direction counter to rotation of the broom  106  such the collecting surface  123  of the belt  122  is moves at least in part upwards (and typically forwards as well) away from the brush  106 , as indicated by the angled arrow located over the belt  122 . The debris leaves an exit area  126  at the top of the conveyor  120  and drops into a hopper  127 .  
     [0031] It is well known that debris can escape the brush  106  and conveyor  120  in various ways. In particular, the debris can be ejected out underneath the conveyor  120  or bounce over the top of the brush  106 . In the sweeping vehicle  100  according to the present invention, a set of flaps or plates are included to prevent debris from escaping. These flaps include a conveyor flap  130 , a cutoff flap  140 , and a recirculation flap  150 .  
     [0032] The conveyor flap  130  is mounted adjacent a bottom edge of the conveyor  130 . The conveyor flap  130  covers at least in part a collector clearance space  138  defined between the bottom edge and the ground surface  112  along the width of the conveyor  120 . The conveyor flap  130  improves the sweeping performance of the sweeper  100  and helps contain dust at least within the enclosed space between the brush  106  and conveyor  120 .  
     [0033] Conceptually, the conveyor flap  130  is a structural element that prevents debris thrown by the brush from colliding with a counter rotating cleat  124  and being batted over the brush  106 . The conveyor flap  130  also serves as a device to improve the trajectory of debris so the debris can land on the belt  122  rather than be thrown under the conveyor  120 .  
     [0034] The cutoff flap  140  is mounted above the conveyor flap  130  and forward of the brush  106 . In this example, the cutoff flap  140  is attached to the conveyor shroud  142 . It is possible to attach the cutoff flap  140  to any structure allowing the flap  140  to be adjacent the brush  106 . The cutoff flap  140  includes a distal edge that is adjacent the outer surface of the brush  106  at a cutoff area  144  of the brush  106 . The cutoff area  144  is located on a portion of the brush&#39;s outer surface that is moving substantially upwards as the brush  106  rotates.  
     [0035] The recirculation flap  150  is mounted behind the brush  106 . The recirculation flap  150  engages the outer surface of the brush  106  at a recirculation contact area  152  of the brush  106 . The recirculation contact area  152  is located on a portion of the brush&#39;s outer surface that is moving substantially downwards and forwards as the brush  106  rotates.  
     [0036] Conceptually, the flaps  140  and  150  are structural elements that counteract the trajectory of debris being expelled by the brush  106  or other debris moving device to recirculate/recollect the debris. By forcing the debris back into the brush  106 , the debris will not be expelled until it reaches the appropriate collection portion of the brush&#39;s rotation (e.g. at the debris collector  120 ). In broad terms, the flaps  140  and  150  are constructed to provide at least a barrier (deflector) to ejected debris and, in the case of the recirculation flap  150 , a bias element to re-introduce the debris into the brush  106 .  
     [0037] Turning now to FIG. 2, a side view of the sweeping system shows the orientation of the flaps  130 ,  140 ,  150  relative to the other parts of the vehicle  100 . The brush  106  contacts the ground at the contact surface  114  as it is being rotated in the direction indicated by the curved arrow. If there is a large amount of debris, the rotation of the brush  106  at the contact surface  114  may build up a “wedge”  200  of debris as the vehicle  100  moves forward. Most of the debris is thrown upwards in a debris path  202  tangential to the brush  106  where the brush  106  contacts a top portion of the wedge  200 . This portion of the debris lands on the belt  122  and is carried into the hopper  127 .  
     [0038] If there is not enough debris to form a wedge  200  of sufficient size, debris can be thrown in a path  204  that is more parallel to the ground surface  112 . The debris may shoot forward under the conveyor&#39;s lower edge  205 . The debris may collide also with a counter-rotating cleat  124  and be batted up and over the brush  106  where it can be left on the ground surface  112  behind the machine  100 . Also, since heavier debris (e.g. rocks from 2 cm to 5 cm in diameter) is more prone to travel along the lower path  204 , the heavier debris tends to reciprocate in a space between the brush  106  and conveyor  120 . The more that debris reciprocates between the brush  106  and conveyor  120 , the more likely it is to batted over the brush  106  by a counter-rotating cleat  124  or be launched in a direction (e.g. sideways, backwards) where it is missed by the brush  106  and left on the ground surface  112 .  
     [0039] The conveyor flap  130  has been found to help reduce collisions with counter-rotating cleats and reciprocation of debris between the brush  106  and conveyor  120 , as well as preventing debris from being ejected underneath the conveyor  120 . The conveyor flap  130  typically includes at least a rigid mounting bracket  230  and a flexible blade or skirt  232 . The mounting bracket  230  attaches adjacent to the lower edge  205  of the conveyor  120 . The mounting bracket  230  can either be attached to the conveyor  120  or to any part of the surrounding structure. The mounting bracket  230  extends along the width of the conveyor  120  and forms a rigid blocking member in front of and/or below the conveyor  120 . The conveyor flap  130  thereby covers the collector clearance space  138  between the ground surface  112  and the conveyor&#39;s lower edge  205 .  
     [0040] The conveyor flap  130  may be configured so that a ground clearance gap  234  exists between the flexible blade  232  and the ground surface  112 . The ground clearance gap  234  prevents dust and small debris from accumulating on the flexible blade  232  and lessens wear on the flexible blade  232 . The flexible blade  232  is compliant enough that material that is larger than the clearance gap  234  will deflect the flexible blade  232  upwards so that debris does not get swept forward by the flexible blade  232 , thereby allowing the debris to reach the brush  106 .  
     [0041] It is also known that debris can be carried over the top of the brush  106  such as in a path  240  as indicated in FIG. 2. In prior art sweepers, this debris is usually ejected from behind the brush  106  and therefore missed by the sweeper. By including the cutoff flap  140 , the debris is defected substantially downwards so that the debris can be returned to the collection space  242 , and eventually be recovered at the conveyor  120 .  
     [0042] The cutoff flap  140  in the illustrated embodiment is formed as an elongated blade fixably attached to an angle bracket  243  and a mounting plate  244 . A retainer bracket  246  clamps the cutoff flap  140  to the mounting plate  244 . The retainer bracket  246  may have an angular cross section to further stiffen the cutoff flap  140  and angle bracket  243 .  
     [0043] The angle bracket  243  orients the distal end of the cutoff flap  140  to the desired angle relative to the brush  106 . The angle bracket  243  also positions the cutoff flap  140  so that there is a gap  248  between a distal edge  247  of the cutoff flap  140  and the outer surface of the brush  106  (i.e. at the tip of the bristles  108 ). In most applications, the gap  248  is desired to reduce vibrations and wear on the brush  106  and cutoff flap  140 . In some applications, however, it may be beneficial to allow the distal edge  247  to touch the brush  106  (i.e. gap  248  measures zero), or arrange the cutoff flap  140  so that the distal edge  247  protrudes through the brush&#39;s outer surface to extend into the bristles  108 .  
     [0044] The cutoff flap  140  is preferably made adjustable (e.g. by using elongated mounting slots) thereby allowing the user to adjust the gap  248  to keep it a desired value given various stages of brush wear. The cutoff flap  140  is made from a flexible material, such as rubber or plastic. A cutoff flap  140  using a rigid blade may also be constructed, although the associated gap  248  would typically need to be larger to prevent flap damage due to deflecting large objects or inadvertent contact with the brush  106 .  
     [0045] Debris can also be carried over the top of the brush  106  by being embedded within the bristles of the brush  106  and therefore missed by the cutoff flap  140 . This debris can fall off the back end of the brush  106  as it rotates. By including the recirculation flap  150 , the debris is deflected back into the bristles  108  at the back end of the brush so that the debris can be carried forward (recirculated) to the wedge  200  and eventually be recovered at the conveyor  120 .  
     [0046] The recirculation flap  150  in the illustrated embodiment includes a flexible mounting flap  250  fixably attached to a chassis bracket  251 . The mounting flap  250  allows the recirculation flap  150  to conform to ground surface irregularities so as to prevent breakage of the flap  150 . Alternate structural elements may be used in place of a flexible mounting flap  250  to allow conformance of the flap  150 , including spring loaded and/or slidable mounts. However, such alternates may be more prone to damage due to chassis movement. The flexible mounting flap  250  allows a flexible and resilient mount that is not easily damaged even when contacting the ground.  
     [0047] A rigid angle bracket  252  is coupled to the mounting flap  250  and an elongated blade  254 . The angle bracket  252  can be incorporated as part of the mounting flap  250  and/or elongated blade  254 , or be fabricated as a separate piece as shown. The angle bracket  252  orients the elongated blade  254  so that a portion of the blade  254  is at least touching an outer surface of the brush  106  (i.e. at the tip of the bristles  108 ) along the brush&#39;s width. As shown in FIG. 2, the elongated blade  254  may protrude beneath the outer surface so that a tip  255  of the elongated blade  254  extends into the bristles  108 . An additional skirt  222  extends from the mounting flap  210  to close proximity with the ground. The skirt  222  could also be formed by further extending the mounting flap  210  downward.  
     [0048] A housing  258  typically surrounds the brush  106  and conveyor  120 . It is appreciated that the spaces between the rotating brush  106  and the housing  258  are potential escape routes for airborne dust stirred up by the brush&#39;s rotation. The conveyor clearance space  138  is another escape route for dust. The flaps  130 , 140 , 150  substantially block portions of these spaces and thereby help prevent the airborne dust from escaping. The conveyor flap  130  prevents dust from passing through the collector clearance space  138 , the cutoff flap  140  traps dust in the collection space  242 , and the recirculation flap  150  prevents dust from passing between the inner surface of the housing  258  and a rear portion of the brush  106 . The vehicle  100  may also include a vacuum system  150  (best seen in FIG. 1) to pull dust from inside the housing  258 . The flaps  130 , 140 , 150  create a restriction of outside air flowing into the housing  258 , and thereby help retain the dust in the housing  258  so that it can be more thoroughly removed by the vacuum system  150 . Skirt  222  further contains dust and improves the effectiveness of the vacuum system.  
     [0049] Turning now to FIG. 3, geometric details of the flaps are illustrated. The conveyor flap  130  is mounted adjacent the lower edge of the conveyor  120 , typically at an angle  330  ranging between  20  degrees and  70  degrees. If a ground clearance gap  234  (seen in FIG. 2) is included, it measures preferably between 0.75 and 1.25 inches (0.9 and 3.2 cm).  
     [0050] The cutoff flap  140  is mounted forward of the brush  106  so that the distal edge  247  is adjacent the cutoff area  144 . The cutoff area  144  is preferably located at an angle  340  measuring between 45 degrees to 140 degrees (preferably 94 degrees) from the ground contact area  114 . For a brush  106  with a nominal outer diameter of 35.5 inches (90.2 cm), this corresponds to locating the distal edge  247  of the cutoff flap  140  about 20.0±1.0 inches (51.0±2.0 cm) above ground. The cutoff flap  140  is typically oriented at a mounting angle  342  measuring between 10 degrees and 30 degrees from horizontal, preferably about 23±1 degrees. In this application, the gap  248  ranges from 0.0 inches to 1.0 inch (2.50 cm) or more, preferably 0.75±0.10 inches (1.91±0.25 cm).  
     [0051] At the back end of the brush, the recirculation flap  150  contacts the brush  106  at the recirculation contact area  152 . The recirculation contact area  152  can be located anywhere the brush&#39;s outer surface is moving at least in part downwards. Typically, the recirculation contact area  152  located at a contact angle  350  measuring between 20 degrees to 90 degrees clockwise from the ground contact area  114 , preferably 63±2 degrees. For a brush  106  with a nominal outer diameter of 35.5 inches (90 cm), this corresponds to locating the tip  350  of the recirculation flap  150  between 4.1 and 14.7 inches (10 and 37 cm) above the ground, preferably 6.75±0.50 inches (17.1±1.2 cm). The elongated blade  254  is oriented at a mounting angle  352  which is from 0 degrees to 90 degrees from vertical, preferably 50±2 degrees. It is appreciated that the nominal brush diameter of 35.5 inches (90 cm) used in this example is that of an unworn brush  106 .  
     [0052] The construction and attachment of the flaps  130 , 140 ,  150  can be accomplished using materials and methods well known in the arts. Typically, the portions of the flaps  130 , 140 , 150  adjacent to moving surfaces (e.g. the brush  106 , the ground surface  112 ) are formed a flexible material. In particular, two- or three-ply sheet rubber product such as thick Goodyear Plylon® is suitable for this application. The flaps  130 ,  140 ,  150  are typically adjustably fastened to rigid brackets that are bolted or welded to the structures.  
     [0053]FIG. 4 shows a useful configuration of the conveyor flap  130 . The mounting bracket  230  can be formed from sheet metal, in this example {fraction (3/16)} inch (4.8 mm) thick carbon steel. The mounting bracket  230  is formed into a tubular structure which gives it strength to resist damage yet keeps the bracket&#39;s weight acceptably low. An equivalent strength aluminum sheet may be used where even lower weight or corrosion resistance is desired. A support blade  402  made of relatively thick rubber (e.g. {fraction (3/16)} inch (4.8 mm) 3-ply rubber) may be sandwiched between the mounting bracket  230  and flexible blade  232 , extending out past the mounting bracket  230 . The support blade  402  is relatively flexible, yet will not droop down when mounted.  
     [0054] In this configuration, the flexible blade  232  is mounted on top of the support blade  402  and extends past an edge of the support blade  301 . The flexible blade  232  is formed from a relatively compliant belted rubber, such as ⅛ inch thick (3 mm) bias 2-ply belted sheet rubber. The flexible blade  232  may include edge slots  404  evenly spaced along the distal edge  406  of the conveyor flap  140 . The slots  404  allow large debris that is passing under the flap  130  to deflect only a small, local portion of the flexible blade  232  so that the remainder of the flexible blade  232  remains substantially undeformed, and therefore the blade  232  can continue to deflect debris back onto the brush  106 . The edge slots  404  shown are substantially perpendicular to a distal edge of the conveyor lip  408 , although it is appreciated that the slots  404  can be formed at a non-perpendicular angle relative to the distal edge  406 .  
     [0055] The flexible blade  232  and support blade  432  are attached to the mounting bracket  230  by fasteners  408  (e.g. bolts) and a clamping bracket  410 . The mounting bracket  230  can be mounted to the vehicle  100  by using fasteners or by other means such as welding. It is appreciated that the flexible blade  232  and/or support blade  402  are removably mounted with bolts  408  at least for maintenance purposes. It may also be desired to remove the blades  232 ,  402  for certain tasks such as sweeping up leaves or other lightweight debris. More elaborate quick release methods of blade mounting may be used, although inexpensive and reliable fasteners such as bolts  408  are usually sufficient for assembling and attaching the blades  232 ,  402 . It is also appreciated the conveyor flap  130  provides some benefit even with one or both blades  232 ,  402  removed.  
     [0056] Referring now to FIG. 5, an embodiment of a cutoff flap  140  is shown. The cutoff flap  140  is best made of two- or three-ply sheet rubber product such as ⅜ inch (0.95 cm) thick Goodyear Plylon® (220B {fraction (3/16)}×{fraction (1/16)}, Class I). Making the cutoff flap  140  from relatively flexible rubber helps prevent damage caused by deflecting heavy objects and inadvertent contact with the brush  106 . In another embodiment, the cutoff flap  140  can be made of a rubber blade portion attached to a rigid portion made of metal or some other suitable material. The rigid portion is attachable to the mounting structures of the vehicle  100 .  
     [0057] The cutoff flap  140  can be attached standard fasteners that pass through the retainer bracket  246  (seen in FIG. 2) mounting slots  500  in the flap  140 . The retainer bracket  246  can be formed of angled sheet metal to further stiffen the mounting plate  244  and cutoff flap  160 .  
     [0058] Turning now to FIG. 6, an embodiment of a recirculation flap  150  is shown. The mounting flap  250  and elongated blade  254  are typically made of two- or three-ply sheet rubber product such as ⅜ inch (0.95 cm) thick Goodyear Plylon®). Fabricating the mounting flap  250  from relatively flexible rubber helps prevent damage to the blade and/or vehicle caused by heavy objects and ground surface irregularities. Further, use of sheet rubber in fabricating the mounting flap  250  and elongated blade  254  help provide damping of the assembly and reduce noise.  
     [0059] The mounting flap  250  can be attached to the chassis bracket  251  (best seen in FIG. 2) using standard fasteners through mounting slots  600 . The angle bracket  252  can be formed from sheet metal, typically 0.08 inch to 0.12 inch thick (2.0 to 4.5 mm) carbon steel. An equivalent strength aluminum or magnesium material may be used where low weight or corrosion resistance is desired. The angle bracket  252  is fastened to the mounting flap  250  and elongated blade  254  by using fasteners  602 . Any type of fastener  602  can be used, such as bolts and/or rivets.  
     [0060] Although the sweeping system of the present invention has been described in conjunction with a self propelled vehicle  100 , it is appreciated that a brush  106 , conveyor  120 , and flaps  130 ,  140 ,  150  can be used alone or in combination on any conveyance, such as trailers or push sweepers. The flaps  130 ,  140 ,  150  can also be used on smaller sweeping systems that have alternate conveyor (debris collector)  120  embodiments, such as an auger conveyor or a suction plenum. The flaps  130 ,  140 ,  150  can also be used in systems that do not have a conveyor, such as systems that throw the debris directly into a hopper.  
     [0061] It will, of course, be understood that various modifications and additions can be made to the preferred embodiments discussed hereinabove without departing from the scope of the present invention. Accordingly, the scope of the present invention should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.