Patent Publication Number: US-2003229957-A1

Title: Conveyor for mechanical street sweeper

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to conveyors, particularly conveyors for mechanical street sweepers, and to street sweepers comprising conveyors.  
       [0003] 2. Description of the Prior Art  
       [0004] Different kinds of conveyors have been used in mechanical street sweeping machines. There is the squeegee style conveyor that drags material along a conveyor tray and up to a hopper. There is the full-width belt style that carries material up to a hopper on the top of the belt. There is also an auger system that dumps material onto a narrow belt conveyor that ends at a hopper. These systems all use two shafts, one drive shaft and a corresponding driven shaft, located at opposite ends of the conveyor. The size of the material conveyed by such conveyors is generally limited to the distance between the shaft and the lower surface of the conveyor.  
       [0005] In a “squeegee” or drag type conveyor, a number of spaced apart and usually somewhat flexible cleats or flights, commonly known as “squeegees”, is provided. Each squeegee is disposed across the width of the conveyor and is used to drag debris along a surface of a conveyor tray, which is usually disposed immediately below and parallel to the lower straight span of the conveyor, in order to push the debris off the top end of the conveyor tray into a hopper. It is preferable that the squeegees be somewhat flexible in order to make substantially sealing sliding contact with the surface of the conveyor tray, so that debris, including mud and water, is dragged up the conveyor tray. The conveyor tray may terminate at its lower end in a curved lower lip that follows the arc of the distal edge of the squeegees as they arcuately traverse the bottom end of the conveyor. Two shafts, each connecting a pair of pulleys or sprockets located at opposite ends of the conveyor, are generally used to drive the conveyor belt. Normally, the shaft at the top end near the hopper drives the conveyor while the shaft near the bottom end idles and is driven in response to movement of the conveyor belt.  
       [0006] A mechanical street sweeper is generally equipped with a hopper in which debris is stored after being swept up from a roadway. The debris is conveyed from the roadway to the hopper by means of the conveyor, which receives the debris from rotating brushes or brooms in contact with the road surface. As contractors increasingly use such sweepers to pick up larger and larger objects, the conveyor must be able to convey these larger objects to the hopper without plugging or stalling.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention relates to a conveyor for a mechanical street sweeper, in particular to a squeegee style conveyor, and to street sweepers comprising a conveyor.  
       [0008] Thus, there is provided a conveyor for a mechanical street sweeper, the conveyor comprising: a conveyor tray having a first longitudinal end, a second longitudinal end and a surface adapted to have debris conveyed thereon; a first set of laterally spaced apart rotational elements rotationally supported on the conveyor tray at the first end; a second set of laterally spaced apart rotational elements rotationally supported on the conveyor tray at the second end defining a laterally unobstructed passageway through which debris may pass between the second set of spaced apart rotational elements; a set of laterally spaced apart parallel loops supported on and engaged with the set of rotational elements and having laterally extending flights attached to the loops at intervals along the loops, the loops and the sets of rotational elements being located on the conveyor tray such that the flights travel along the conveyor tray to convey debris along the surface; and, a drive means connected to either the first or the second set of rotational elements for rotating the loops.  
       [0009] There is further provided a mechanical street sweeper comprising: a frame; a hopper supported by the frame for holding debris; a brush supported by the frame for selective rotation in contact with a roadway; an inclined conveyor tray supported by the frame and having a first longitudinal end proximate the hopper adapted for delivering debris to the hopper, a second longitudinal end proximate the brush adapted for receiving debris from the brush and a surface adapted to have debris conveyed thereon; a first set of laterally spaced apart rotational elements rotationally supported on the frame or the conveyor tray proximate the first end of the conveyor tray; a second set of laterally spaced apart rotational elements rotationally supported on the frame or the conveyor tray proximate the second end of the conveyor tray and defining a laterally unobstructed passageway between the second set of rotational elements through which debris may pass from the brush to the surface of the conveyor tray; a set of laterally spaced apart parallel loops supported on and engaged with the sets of rotational elements and having laterally extending flights attached to the loops at intervals along the loops, the loops and the sets of rotational elements being located on the frame or the conveyor tray such that the flights travel along the conveyor tray to convey debris along the surface; and, a drive means connected to either the first or the second set of rotational elements for rotating the loops.  
       [0010] The present invention advantageously permits handling debris of a variety of sizes which may be found on roadways. For example, small debris such as sand, leaves and gravel normally found on residential streets and large debris such as blown tires, hubcaps and millings (chunks of pavement) often found on highways can all be picked up while reducing the instances of jamming, plugging and/or stalling. Increased clearance which permits such advantageous handling is facilitated in the present invention by the removal of the shaft at the end of the conveyor closest to the roadway. The size of the debris that the street sweeper is able to pick up is accordingly no longer limited to the distance between the shaft and the surface of the conveyor tray.  
       [0011] Street sweepers generally include a frame, suspension, wheels, an internal combustion engine and other standard vehicle components that will not be discussed here in any detail. The frame typically supports a hopper in which debris is housed until the debris can be disposed of at a site. The upper part of the hopper is open to receive debris from the conveyor. The frame also supports a brush or brushes for sweeping debris off the roadway. Typically there is at least one brush for selective rotation in contact with a roadway whose rotation sweeps debris off the roadway onto the conveyor tray where it is conveyed by the conveyor up to the hopper. Drag shoes located laterally from the brush are also generally employed to minimize the amount of debris which is thrown laterally from the street sweeper.  
       [0012] The conveyor comprises a conveyor tray having a first longitudinal end that is proximate the hopper adapted for delivering debris to the hopper. The conveyor tray also has a second longitudinal end proximate the brush adapted for receiving debris from the brush. The conveyor tray further has a surface adapted for having debris carried thereon from the second end to the first end for delivery into the hopper. The conveyor tray is supported on the frame of the street sweeper and is generally inclined from the roadway up to the hopper.  
       [0013] The conveyor further comprises two sets of laterally spaced apart rotational elements which are rotationally supported on either the conveyor tray or the frame of the street sweeper. Preferably the rotational elements are supported on the conveyor tray to provide a unitized conveyor system that can be more easily put on or taken off the frame of the street sweeper. One set of laterally spaced apart rotational elements (i.e. the first set) is located at or proximate the first longitudinal end of the conveyor tray. The other set of laterally spaced apart rotational elements (i.e. the second set) is located at or proximate the second longitudinal end of the conveyor tray. The first set of rotational elements may be connected by a shaft that extends laterally across and through the conveyor or may be unconnected in this way. It is preferred to connect the first set by a solid shaft to facilitate driving the conveyor.  
       [0014] The second set of rotational elements is supported on the conveyor tray or the frame in such a way as to at least partially open the lateral space through the conveyor between the rotational elements of the second set. This provides more room for debris to pass from the brush to the surface of the conveyor tray permitting larger objects to be conveyed up to the hopper. The second set of rotational elements may be supported in any manner known in the art which opens the lateral space between them, but it is preferred to use a manner which maximizes the amount of room between the rotational elements. Advantageously, the second set of rotational elements may be independently supported on the conveyor tray or the frame, for example, by using spindle hub assemblies such as those typically used on automobile and trailer wheels. The spindle hub assemblies comprise bearings, optionally packed in grease, and preferably include a seal and dust cap to protect the bearings from debris in order to minimize the need for maintenance of the bearings. Two bearings may be advantageously employed. The first set of rotational elements may also be supported in such a manner, if desired. Scrapers supported on the conveyor tray or the frame and located between the top and bottom of the loops just behind each rotational element of the second set may be used to help minimize buildup of dirt and other debris at the second set of rotational elements.  
       [0015] Supported on and engaged with the rotational elements are laterally spaced apart parallel loops. Each loop wraps around the rotational elements of the first and second set which are located in the same longitudinal line along the conveyor tray. In this way, a set of endless, laterally spaced apart, parallel loops form the basis of the conveyor. Rotation of the loops is achieved through rotation of the first and/or second set of rotational elements by a drive means. It is preferred to rotate the first set of rotational elements since this set is located farther from the roadway and does not come into regular contact with debris.  
       [0016] While it is possible to have any number of rotational elements within a set, the width of the conveyor tray may place a practical limit on the number of rotational elements in each set. It is generally preferred to use a pair of rotational elements in each set. Thus, the conveyor preferably comprises a first pair of rotational elements, a second pair of rotational elements and a pair of belts.  
       [0017] It is also possible to have one or more other sets of laterally spaced apart rotational elements rotationally supported on the conveyor tray or the frame and located longitudinally between the first set and the second set. These other sets of rotational elements are generally smaller in diameter than, and located vertically higher in relation to the surface of the conveyor tray than, the first and second sets of rotational elements These other sets of rotational elements typically idle and may be used to help support the loops in the longitudinal space between the first and second sets of rotational elements. These other sets of rotational elements may be connected by a solid shaft that extends laterally across and through the conveyor or they may be unconnected in this way. The smaller diameter and the higher vertical location of these other rotational elements helps in maximizing the increased clearance realized by the conveyor of the present invention.  
       [0018] A wide variety of rotational elements useful in the present invention are known in the art. Advantageously, pulleys and/or sprockets are used. When pulleys are used, the loop is a belt. When sprockets are used, the loop is a chain. It is possible to use a combination of pulleys and sprockets, however, it is preferred to use either pulleys or sprockets. Chains and belts may comprise a wide variety of material typically used in the conveyor arts, for example, steel, rubber, etc.  
       [0019] Attached at intervals along the loops and extending laterally across the conveyor&#39;s width are a series of flights that travel longitudinally along the conveyor as the loops are rotated by the rotation of the rotational elements. The rotational elements and hence the loops and flights are located such that the flights are capable of moving debris longitudinally along the surface of the conveyor tray. The flights are preferably somewhat flexible so that they may make some contact and seal with the surface of the conveyor tray thus enabling the conveyance of water, mud and other fine debris. The flights may be made of any suitable material known in the art, for example, aluminum, steel, rubber, plastic, or combinations thereof. Aluminum flights with rubber edges are particularly useful as they provide both strength and flexibility. The flights generally extend the width of the conveyor tray, therefore, the flights may extend laterally beyond the loops if the distance between outside loops is less than the width of the conveyor tray.  
       [0020] A wide variety of drive means that may be used to drive the conveyor of the present invention are known in the art. Advantageously, motors may be used, preferably hydraulic drive motors. When a set of rotational elements is independently supported on the conveyor tray or the frame, it is possible to use more than one motor to drive the rotational elements independently and to synchronize their speeds using an electronic controller. However, for simplicity, a single motor is generally used to drive the first set of rotational elements, the first set being connected by a laterally extending solid shaft. The drive means is preferably reversible to permit rotation of the rotational means, and hence the loops, in either direction. This is particularly useful for clearing jams and cleaning the conveyor as the flights can then travel longitudinally along the surface of the conveyor tray either toward the hopper or toward the roadway. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0021] In order that the invention may be more clearly understood, a preferred embodiment thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:  
     [0022]FIG. 1 is a side elevational view of a street sweeper of the present invention;  
     [0023]FIG. 2 is a top perspective view of the conveyor included in the street sweeper of FIG. 1; and  
     [0024]FIG. 3 is an exploded view of a spindle hub assembly included in the conveyor of FIG. 2. 
    
    
     PREFERRED EMBODIMENT  
     [0025] With reference to FIG. 1, a street sweeper ( 1 ) includes a frame ( 5 ), wheels, a suspension, an internal combustion engine and other standard vehicle components. Supported on the frame ( 5 ) is a hopper ( 10 ) which receives debris from an inclined conveyor ( 20 ). The hopper ( 10 ) holds debris until it is emptied at a site and at least a portion of the hopper ( 10 ) has the general shape of a box with an upper open end. The conveyor ( 20 ) comprises a conveyor tray ( 21 ) having a surface ( 22 ) which receives debris swept up off the roadway by a brush ( 15 ) located at the rear of the street sweeper and rotating in a clockwise direction as viewed in FIG. 1. Drag shoes ( 17 ) located laterally on either side of the brush ( 15 ) minimize the amount of debris which is thrown laterally from the street sweeper by the brush.  
     [0026] In order to move debris along the surface ( 22 ), a series of laterally extending rubber edged aluminum flights ( 29 ) attached at intervals to a pair of laterally spaced apart parallel reinforced rubber belts ( 28 , one of the pair not shown) are in contact with the surface ( 22 ) and push debris up the surface ( 22 ) as the flights ( 29 ) travel upwardly due to clockwise motion of the pair of belts ( 28 , one of the pair not shown). When one of the flights ( 29 ) travels in a clockwise direction, a flight starting at the bottom of the conveyor tray ( 21 ) travels upwardly to push debris up the surface ( 22 ) to the top of the conveyor tray ( 21 ) where the debris is pushed off the end of the surface ( 22 ) to fall into the hopper ( 10 ). A flight at the top of the conveyor tray ( 21 ) travels around the first pair of pulleys ( 24 , one of the pair not shown) and then travels down the conveyor tray ( 21 ) on the topside of the belts ( 28 , one of the pair not shown) until the flight reaches the bottom of the conveyor tray ( 21 ) and once again contacts the surface ( 22 ) to push debris up to the hopper ( 10 ). Sequentially spacing the flights ( 29 ) on the belts ( 28 , one of the pair not shown) helps ensure continuous movement of debris up the surface ( 22 ).  
     [0027] The pair of belts ( 28 , one of the pair not shown) is supported on and engaged with a first pair of laterally spaced apart pulleys ( 24 , one of the pair not shown) proximate the longitudinal end of the conveyor tray ( 21 ) located near the hopper ( 10 ). The pair of belts ( 28 , one of the pair not shown) is also supported on and engaged with a second pair of laterally spaced apart pulleys ( 27 , one of the pair not shown) proximate the longitudinal end of the conveyor tray ( 21 ) located near the brush ( 15 ). A third, smaller pair of laterally spaced apart pulleys ( 23 , one of the pair not shown) also supports the belts ( 28 , one of the pair not shown) at about the midpoint between the first and second pair of pulleys ( 24  and  27 , one of each pair not shown). All the pairs of pulleys ( 23 ,  24  and  27 , one of each pair not shown) are rotationally supported on the conveyor tray ( 21 ) to permit rotation of the belts ( 28 , one of the pair not shown) as the first pair of pulleys ( 24 , one of the pair not shown) is driven in a clockwise direction, as viewed looking at FIG. 1, by the action of a hydraulic motor (not shown).  
     [0028] An enlarged view of the conveyor can be seen in FIG. 2. In FIG. 2, the belts ( 28   a ,  28   b ) are supported on and frictionally engaged with the first pair of pulleys ( 24 —one referred to as  24   a  and the other as  24   b  ( 24   b  not shown)) and are also supported on and frictionally engaged with the second pair of pulleys ( 27 —one referred to as  27   a  and the other as  27   b ). A third pair of pulleys ( 23 , one referred to as  23   a  and the other as  23   b ) rotationally supported on the conveyor tray ( 21 ) is connected by a shaft and is located about half way along the conveyor tray ( 21 ) between the first pair of pulleys ( 24   a ,  24   b ) and the second pair of pulleys ( 27   a ,  27   b ). The third pair of pulleys ( 23   a ,  23   b ) helps support the belts ( 28   a ,  28   b ) and is smaller in diameter than and located vertically higher on the conveyor tray ( 21 ) than both the first pair of pulleys ( 24   a ,  24   b ) and the second pair of pulleys ( 27   a ,  27   b ). The first pair of pulleys ( 24   a ,  24   b ) is connected by a solid shaft ( 25 ) and the shaft ( 25 ) is rotationally supported on the conveyor tray ( 21 ). A hydraulic motor ( 26 ) drives the shaft ( 25 ) which in turn drives the first pair of pulleys ( 24   a ,  24   b ), therefore, each pulley ( 24   a ,  24   b ) is driven at the same speed. The rotation of the first pair of pulleys ( 24   a ,  24   b ) drives the belts ( 28   a ,  28   b ), which in turn causes the flights ( 29 , only one of which is shown for greater clarity) to travel along the surface ( 22 ) of the conveyor tray ( 21 ). The hydraulic motor ( 26 ) is reversible to permit either clockwise or counterclockwise motion of the first pair of pulleys ( 24   a ,  24   b ) and of the belts ( 28   a ,  28   b ) thus permitting the flights ( 29 ) to also push debris down the surface ( 22 ) of the conveyor tray ( 21 ) to facilitate cleaning and for the removal of jams.  
     [0029] Still referring to FIG. 2, the second pair of pulleys ( 27   a ,  27   b ) is not connected by a shaft, thereby providing an unobstructed passageway ( 40 ) in the lateral space between the second pair of pulleys ( 27   a ,  27   b ). The unobstructed passageway ( 40 ) permits larger debris swept up by the brush ( 15 ) (not shown in FIG. 2) to pass between the second pair of pulleys ( 27   a ,  27   b ) to be deposited on the surface ( 22 ). The debris is then pushed up the conveyor tray ( 21 ) by the flights ( 29 ) off the end of the surface ( 22 ) to be delivered to the hopper ( 10 ) (not shown in FIG. 2). The second pair of pulleys ( 27   a ,  27   b ) is not driven and rotates in response to movement of the belts ( 28   a ,  28   b ), thereby acting as idler pulleys. Scrapers ( 30   a ,  30   b ) are located just behind each of the second pair of pulleys ( 27   a ,  27   b ) to help minimize buildup of dirt and other debris at the second pair of pulleys ( 27   a ,  27   b ). Each of pulleys ( 27   a ,  27   b ) is supported on the conveyor tray ( 21 ) by a spindle hub assembly ( 50   a ,  50   b , respectively).  
     [0030]FIG. 3 depicts an exploded view of a spindle hub assembly ( 50   a ) used at the lower end (second longitudinal end) of the conveyor of FIG. 2. (It is understood that the following description of FIG. 3 also applies to the corresponding spindle hub assembly ( 50   b ) on the other side of the conveyor tray ( 21 ) in FIG. 2). The spindle hub assembly ( 50   a ) includes a spindle hub and drum ( 51 ) on which the pulley is supported and through which a spindle ( 52 ) is inserted. The spindle ( 52 ) is held in the spindle hub and drum by a spindle nut ( 57 ), which is accompanied by a spindle washer ( 56 ) and cotter pin ( 58 ) for additional security. The spindle ( 52 ) also passes through an inner bearing and an outer bearing located on either side of the spindle hub and drum ( 51 ). The inner bearing comprises a bearing cone ( 54   a ) and a bearing cup ( 55   a ) and the outer bearing comprises a bearing cone ( 54   b ) and a bearing cup ( 55   b ). The bearings are generally packed in grease and allow for free rotation of the spindle hub and drum ( 51 ) around the spindle ( 52 ). A grease seal ( 53 ) helps prevent dirt and other debris from getting into the inner bearing. A dust cap ( 59 ), or optionally a grease cap, helps prevent dirt and other debris from getting into the outer bearing. The spindle hub and drum ( 51 ) is mounted on the conveyor tray by stud bolts ( 60 ) which are secured by stud nuts ( 61 ).  
     [0031] Other advantages which are obvious and which are inherent to the structure will be evident to one skilled in the art.  
     [0032] It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.  
     [0033] Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.