Patent Publication Number: US-6702135-B2

Title: Universal dumpster

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 09/428,169 filed Oct. 27, 1999, now U.S. Pat. No. 6,296,132. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a dumpster for collecting, containing and controlling solid waste at a refuse collection site. More particularly, the invention is a universal dumpster adapted for use with both a front loading and a roll-off refuse collection truck. 
     BACKGROUND OF THE INVENTION 
     Proper collection, containment, control, transportation and disposal of solid waste are necessary for protecting public health and safety and for promoting a clean environment. Containers, commonly known as dumpsters, that hold large quantities of solid waste generated at multifamily residential, institutional, commercial, industrial, and construction sites, are an important tool in the management of solid waste. 
     There are at least two types of dumpsters for handling solid waste, the “front loader” dumpster and the “rear loader” dumpster. Present dumpster designs incorporate several common features including: a floor, side walls, and end walls which together define an interior compartment; openings through which solid waste is placed into the interior compartment; openings through which the solid waste is discharged out of the interior compartment; and means for supporting the dumpster while the solid waste is being discharged. 
     The front loader type dumpster is typically used at multifamily residential and light commercial sites and is provided with sleeves fixed to the exterior of the side walls to receive the lifting arms of a front loading truck. The front loading truck approaches the front loader dumpster and positions the arms of the truck within the sleeves of the container. The driver then activates a hydraulic system which lifts the dumpster over the cabin of the truck and rotates it to a substantially inverted position to discharge the solid waste into a larger container on the back of the truck, generally referred to as a hopper. Next, the driver lowers the empty dumpster and withdraws the lifting arms of the front loading truck from the sleeves. The driver may then activate a compactor in the hopper to compact the solid waste and thereby increase the amount of solid waste that the hopper can accommodate. The front loading truck then travels to the location of the next front loader dumpster to repeat the procedure until the hopper is full. Once the hopper is full, the front loading truck travels to a disposal site, such as a landfill, to dispose of the solid waste. 
     The rear loader type dumpster is larger than a front loader type dumpster and is typically used at heavy commercial, industrial and construction sites. Rather than being emptied into the hopper of a front loading truck, the rear loader dumpster is pulled onto the bed of a roll-off truck and transported to the disposal site. A typical roll-off truck is equipped with a winch and roller system which positions the dumpster onto the bed of the truck for transportation to the disposal site. Once at the disposal site, the bed and dumpster are tilted so that the solid waste is discharged through one or more rear doors provided in the end wall of the dumpster, much like a dump truck. After being emptied, the rear loader dumpster is returned to the same or a different refuse collection site. 
     Utilizing different types of dumpsters which each require a different method of discharging the solid waste reduces both the cost effectiveness and the efficiency of solid waste collection. Conventional front loader type dumpsters are relatively small and are not provided with a door in an end wall of the dumpster. Furthermore, because the solid waste in a conventional front loader dumpster must be discharged through an opening in the top of the dumpster, it cannot be emptied by a roll-off truck. Conventional rear loader type dumpsters are wider than front loader type dumpsters and are not provided with sleeves. As such, a rear loader dumpster cannot be emptied by a front loading truck. Accordingly, solid waste collection would be more cost effective and efficient if the two types of dumpsters could be combined into a single universal dumpster which can be emptied by either a front loading truck or a roll-off truck. 
     A major environmental concern is the accidental dispersal of solid waste from a front loader dumpster while the solid waste is being discharged into the hopper of the front loading truck. For example, a sudden gust of wind may disperse some of the solid waste onto the ground surrounding the front loading truck as the front loader dumpster is being emptied. Front loader dumpsters are discharged at refuse collection sites that are typically located in areas where people live and work. Thus, the solid waste that is accidentally dispersed has a negative impact on both the public health and safety and the environment. 
     Conventional designs for front loader dumpsters pose additional safety concerns. The sleeves of a front loader dumpster that engage the lifting arms of a front loading truck are typically welded onto the exterior surface of the side walls of the dumpster. Because the solid waste in a conventional front loader dumpster is discharged through an opening in the top, the dumpster must be completely inverted to discharge all of the solid waste from the interior compartment. Completely inverting the dumpster induces shock stresses on the welds holding the sleeves to the side walls because the weight of the dumpster suddenly shifts from the top of the sleeves to the bottom of the sleeves as the dumpster is inverted. Over time, the welds holding the sleeves to the side walls can weaken and ultimately break from repeated emptying of the dumpster. As a result, the dumpster could fall onto the front loading truck as it is being inverted to discharge the solid waste, potentially injuring workers or passersby. 
     In addition to posing a safety hazard, the shock stresses induced on the sleeve welds reduce the efficiency of front loading trucks. The lifting capability of late model front-loading trucks usually exceeds the weight capacity of a front loader dumpster. However, because of the danger of the sleeves breaking away from the side walls, the usable volume of a front loader dumpster is limited by a safety factor. If front loader dumpsters were provided with doors in one of the end walls for discharging solid waste, they would not have to be completely inverted to discharge all of the solid waste from the interior compartment of the dumpster. Eliminating the need to completely invert the dumpster would eliminate the shock stresses on the welds holding the sleeves to the side walls induced by the sudden shifting of the weight of the dumpster on the sleeves. As a result, dumpsters capable of containing a larger volume of solid waste could be utilized with front loading trucks. 
     For the foregoing reasons, it is apparent that a need exists for a universal dumpster that can be emptied by either a front loading truck or a roll-off truck. A need also exists for a universal dumpster that minimizes, and preferably eliminates, the accidental dispersal of solid waste into the environment during discharge of the solid waste into the hopper of a front loading truck. Finally, there exists a need to increase both the safety of front loader dumpsters and the efficiency of front loading trucks. 
     SUMMARY OF THE OBJECTS OF THE INVENTION 
     Accordingly, it is a principal object of the present invention to provide a universal dumpster that is designed and constructed in such a way that it may be emptied by either a front loading truck or a roll-off truck. 
     It is a further object of the present invention to provide a universal dumpster that minimizes the environmental damage caused by the accidental dispersal of solid waste during discharge of the solid waste into the hopper of a front loading truck. 
     It is a further object of the present invention to provide a universal dumpster that is designed and constructed to be emptied by a front loading truck without inducing shock stresses on the welds which hold the sleeves to the side walls of the dumpster. 
     It is a further object of the present invention to provide a universal dumpster that is designed and constructed to be emptied by a front loading truck without exerting excessive forces on the lifting arms of a convention front loading refuse collection vehicle at the beginning of the lifting process. 
     It is a further object of the present invention to provide a universal dumpster that has an expandable volume. 
     It is a further object of the present invention to provide a universal dumpster having sufficient lids and doors conveniently located on the dumpster so that solid waste may be placed in all areas of the interior compartment of the dumpster. 
     SUMMARY OF THE INVENTION 
     The above objects and others are achieved by a universal dumpster constructed in accordance with the present invention. A universal dumpster according to this invention includes a floor having interior and exterior surfaces. A pair of side walls extend upwardly and generally perpendicularly from the floor. Likewise, a pair of end walls extend upwardly and generally perpendicularly from the floor. The end walls are also generally perpendicular to and attached to the side walls. The floor, side walls and end walls together define an interior compartment for collecting and containing solid waste. A sleeve is fixed to each side wall to engage the pickup arm of a conventional front loading refuse collection vehicle. At least one of the end walls of the dumpster includes at least one door which is movable between a first fully closed position and a second fully opened position which exposes an opening through the end wall for depositing solid waste into the dumpster and discharging the solid waste from the dumpster. 
     In one preferred embodiment of the invention, the end wall is formed by a downwardly opening lower door hingedly attached to the floor and having a front panel and a pair of side panels. The front panel and the side panels form a discharge chute when the lower door is in the second fully opened position. In another preferred embodiment, the end wall is formed by a pair of front doors that are movable between a first fully closed position and a second fully opened position. In the fully opened position, the doors form a discharge chute. Each door is hingedly attached to one of the side walls and has a floor panel extending from the base of the door. In another preferred embodiment, the end wall is formed by a pair of front doors that are hingedly attached to a telescoping discharge chute. The telescoping discharge chute is formed by a floor ramp extension panel and side wall extension panels extending upwardly and generally perpendicularly from the floor ramp extension panel. The telescoping discharge chute is attached to the dumpster by at least one telescoping rod. 
     In addition, the dumpster may be constructed with or without a lid. A lid for a dumpster according to this invention is formed by at least one door which is movable between a first fully closed position and a second fully opened position which allows access to the interior compartment of the dumpster for depositing solid waste. Likewise, at least one of the side walls of the dumpster may be provided with a door that allows access to the interior compartment of the dumpster for depositing solid waste. In yet another preferred embodiment, the dumpster may include at least two wheels attached to the floor of the dumpster and a removable trailer hitch. The wheels and the trailer hitch permit the dumpster to be moved to a location that is accessible to a conventional refuse collection vehicle. In yet another preferred embodiment, the dumpster may include a pair of movable sleeves for reducing the forces exerted on the lifting arms of a conventional front loading refuse collection vehicle at the beginning of the lifting process, thereby further increasing the capacity of the dumpster. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In view of the aforementioned objects and others, which will more readily appear as the nature of the invention is better understood, the invention consists in the novel combination and arrangement of parts hereinafter more fully described, illustrated and claimed with reference being made to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 2 is a partial perspective view of the universal dumpster of FIG. 1 with the discharge chute shown in the fully opened position. 
     FIG. 3A is a partial sectional view of the universal dumpster of FIG. 1, taken in the direction indicated by the line  3 — 3  in FIG. 1, with phantom lines indicating the movement of the upper door in the end wall and one of the lid doors from their fully closed positions to their fully opened positions. 
     FIG. 3B is a partial sectional view of the dumpster of FIG. 2 taken in the direction indicated by the line  3 — 3  in FIG.  1 . 
     FIG. 4 is a perspective view of the universal dumpster of FIG. 1 as viewed from the rear of the dumpster. 
     FIG. 5A is a partial perspective view of the universal dumpster of FIG. 4 with the small inset doors shown in the opened position. 
     FIG. 5B is a partial perspective view of the universal dumpster of FIG. 4 with the large rear doors shown in the opened position. 
     FIG. 6 is an environmental view of the universal dumpster of FIG. 1 illustrating the lifting arms of a conventional front loading truck engaging the sleeves of the dumpster. 
     FIG. 7 is an environmental view of the universal dumpster of FIG. 1 illustrating the dumpster being lifted and emptied through the front doors into the hopper of a conventional front loading truck. 
     FIG. 8A is an environmental view of the universal dumpster of FIG. 1 illustrating the dumpster being tilted and emptied through the front doors by a conventional roll-off truck. 
     FIG. 8B is an environmental view of the universal dumpster of FIG. 1 illustrating the dumpster being tilted and emptied through the rear doors by a conventional roll-off truck. 
     FIG. 9 is a partial elevation view and a partial sectional view of another preferred embodiment of a universal dumpster according to the invention. 
     FIG. 10 is a sectional view of the universal dumpster of FIG. 9 taken in the direction indicated by the line  10 — 10  in FIG.  9 . 
     FIG. 11 is an end view of the universal dumpster of FIG. 9 taken in the direction indicated by the line  11 — 11  in FIG.  9 . 
     FIG. 12 is a perspective view of another preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 13 is a perspective view of an alternate embodiment of the universal dumpster of FIG.  12 . 
     FIG. 14 is an environmental view of the universal dumpster of FIG. 12 illustrating the dumpster being pulled from the rear onto a conventional roll-off truck for transportation to a disposal site. 
     FIG. 15 is a partial perspective view of another preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 16 is a partial perspective view of the universal dumpster of FIG. 15 with the front doors shown in the opened position. 
     FIG. 17 is a partial sectional view of the universal dumpster of FIG. 15 taken in the direction indicated by the line  17 — 17  in FIG.  15 . 
     FIG. 18 is a partial sectional view of the universal dumpster of FIG. 15 taken in the direction indicated by the line  18 — 18  in FIG.  17 . 
     FIG. 19 is a partial perspective view of another preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 20 is a partial perspective view of the universal dumpster of FIG. 19 with the front doors shown in the fully opened position and the telescoping floor and telescoping side wall extensions shown in the fully extended position. 
     FIG. 21 is a partial sectional view of the universal dumpster of FIG. 19 taken in the direction indicated by the line  21 — 21  in FIG.  19 . 
     FIG. 22 is a partial sectional view of the universal dumpster of FIG. 19 taken in the direction indicated by the line  22 — 22  in FIG.  21 . 
     FIG. 23 is a perspective view of another preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 24 is an exploded view of the universal dumpster of FIG. 23 with the discharge chute shown in the opened position. 
     FIG. 25 is a perspective view of another preferred embodiment of a universal dumpster according to the invention. 
     FIG. 26 is a perspective view of another preferred embodiment of a universal dumpster according to the invention as viewed from the front of the dumpster. 
     FIG. 27 is an environmental view of the universal dumpster of FIG. 26 illustrating the lifting arms of a conventional front loading truck engaging the sleeves of the dumpster. 
     FIG. 28 is an environmental view of the universal dumpster of FIG. 26 illustrating the dumpster being lifted from the ground by the lifting arms of a conventional front loading truck. 
     FIG. 29 is an environmental view of the universal dumpster of FIG. 26 illustrating the dumpster being emptied through the front doors into the hopper of a conventional front loading truck. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A number of preferred embodiments of the present invention will be described more fully hereinafter. However, the invention should not be construed as being limited to the embodiments described herein. Rather, it is intended that the invention be construed broadly to encompass any and all embodiments of a dumpster having the disclosed features, or equivalents thereof, which are within the skill of an ordinary person in the relevant art. In the description, like reference numerals designate like or corresponding parts throughout the several figures. It is to be also understood that such terms as “front”, “rear”, “top”, “floor”, “side”, and “end” are used in the description for purposes of locating one element relative to another and are not to be construed as limiting terms. Finally, it should be understood that the illustrations provided in the figures are for the purpose of describing various preferred embodiments of the invention, and thus, are not intended to limit the scope of the invention in any manner. 
     Referring now to the accompanying figures, the invention is a large container, hereinafter referred to as a dumpster, indicated generally at  30 , for the efficient collection, containment, and control of solid waste material. In the broadest sense, the dumpster  30  comprises a floor  40 , opposed side walls  50 , and opposed end walls  60 . The floor  40 , side walls  50  and end walls  60  together define an interior compartment of the dumpster  30  for collecting and containing the solid waste. Dumpster  30  is generally rectangular, but may be constructed to any size and shape which will contain the solid waste efficiently and accommodate the conventional apparatus for discharging the solid waste from the dumpster. While dumpsters are generally made of a rigid metal, such as steel, the dumpster  30  of the present invention may be made of any rigid and durable material. The floor  40 , the side walls  50  and the end walls  60  are preferably thin and lightweight to permit conventional refuse collection vehicles to lift and transport as much solid waste as possible. However, the dumpster  30  must also be strong and durable enough to withstand repeated lifting, transportation and discharge of the solid waste, and prolonged exposure to the elements. 
     The floor  40  comprises floor plate  42  that is raised above the ground by support feet  44  attached to the underside of the floor plate  42 . At least one hook  46  is also attached to the floor plate  42  adjacent to at least one of the end walls  60  for pulling the dumpster  30  onto a roll-off truck R, as illustrated in FIG.  14 . The hook  46  is engaged by a conventional winch which pulls the dumpster  30  onto the bed of the roll-off truck R. As the dumpster  30  is pulled onto the bed of roll-off truck R, the support feet  44  engage rollers which assist the winch in positioning the dumpster  30  on the truck R and support the dumpster  30  during transportation. The support feet  44  and hook  46  may be attached to the floor plate  42  by any conventional means, such as welding, which provides a rigid and durable attachment. The floor  40  further comprises a ramp  48  that slopes upwardly from a medial point on the top side of the floor plate  42  in the direction of one of the end walls  60  to facilitate emptying of the solid waste, as will be described hereinafter. 
     The side walls  50  extend upwardly and generally perpendicularly from the floor  40 . Preferably, at least one of the side walls  50  has an opening  52  formed therein (FIG. 3A) which provides access to the interior compartment of the dumpster  30  for depositing the solid waste. More preferably, a door  54  may be provided that is movable from a fully closed position covering the opening  52  to a fully opened position exposing the opening  52 . The door  54  may be provided with a handle  55  to facilitate movement between the fully closed position and the fully opened position. The door  54  is preferably biased in the closed position since it is desirable to cover the opening  52  while the dumpster  30  is being transported or emptied. As is shown in FIGS. 9,  10  and  11 , the side walls  50  may comprise angled side portions  51  which taper inwardly to form a neck having a width narrower than that of the remainder of the interior compartment of the dumpster  30 . The neck allows a dumpster  30  having the width of a conventional rear loading dumpster to be emptied into the hopper of a conventional front loading truck F. 
     A pickup sleeve  56  is fixed to each side wall  50 . The sleeves  56  are constructed to accommodate the lifting arms A of a conventional front loading truck F (FIG.  6 ). In some preferred embodiments, the pickup sleeves  56  are positioned on the exterior surface of the side walls  50  adjacent the floor  40  of the dumpster  30  and flush with one of the end walls  60  of the dumpster  30  (FIG. 1-4,  6 - 8 B,  15 - 16 ,  19 - 20 ). In other preferred embodiments, the sleeves  56  are positioned on the interior surface of the side walls  50  in the space between the floor ramp  48  and the floor plate  42  (FIGS. 9-11,  12 - 13 ,  23 - 24 ). The pickup sleeves  56  may be fixed to the side walls  50  by any conventional means, but preferably are welded to the exterior or interior surface of the side walls  50 . 
     As best shown in FIGS. 1 and 2, in a preferred embodiment of the invention at least one of the end walls  60  is formed by an upwardly opening upper door  62  and downwardly opening lower door  64 . Each of the doors,  62 ,  64  is movable between a fully closed and a fully opened position. The upwardly opening upper door  62  hangs between the ends of the side walls  50  from a lateral hinge  61 . Handle  63  enables a user to open upper door  62  for the purpose of placing solid waste in the dumpster  30 . Upper door  62  is biased in the closed position by gravity. However, hinge  61  may also be provided with a torsion spring (not shown) for biasing upper door  62  in the closed position. Downwardly opening lower door  64  comprises a front panel  64   a  and side panels  65  that overlap the exterior surface of side walls  50  when the lower door  64  is in the fully closed position. The lower door  64  is biased in the closed position by a pre-tensioned torsion spring  66  located along the hinge line formed between the lower door  64  and the floor  40  of the dumpster  30 . Detent latches  67  may be attached to the exterior surface of the side walls  50  to insure that the lower door  64  remains in a closed position until the dumpster  30  is lifted and tilted by a front loading truck F to be emptied. 
     When the dumpster  30  is tilted, the lower door  64  opens automatically under the weight of the solid waste in the interior compartment of the dumpster  30 . A discharge chute, for directing the solid waste from the interior compartment of the dumpster  30  into the hopper H of the front loading truck F (FIG.  7 ), is formed by the front panel  64   a  and the side panels  65  of the fully opened lower door  64 . The upper door  62  also opens when the dumpster  30  is lifted and tilted into position for emptying. Preferably, when the lower door  64  is in the fully opened position, the angle of the front panel  64   a  relative to the floor  40  of the dumpster  30  corresponds to the angle of the ramp  48  relative to the floor  40 . Thus, the front panel  64   a  forms a straight line with the ramp  48 , as shown in FIG.  3 B. Preferably, at least one stop  68  is provided on the dumpster  30  to prevent the lower door  64  from opening beyond the point where the front panel  64   a  and the ramp  48  form a straight line. The stop  68  may be fixed to the floor  40  of the dumpster  30 , as shown in FIG. 1, or may be fixed at any other convenient location on the dumpster  30 . 
     A rear view of the same preferred embodiment of the invention is shown in FIGS. 4,  5 A and  5 B. In the rear view it is apparent that at least one of the end walls  60  is formed by a pair of large rear doors  70  attached to the side walls  50  by opposed vertical hinges  72 . Preferably, each of the large rear doors  70  is biased in the closed position by a pre-tensioned spring located along the hinge line formed between the side wall  50  and the end wall  60 . 
     Preferably, each of the rear doors  70  has an opening  73  formed therein (FIG. 5A) for providing access to the interior compartment of the dumpster  30  to deposit the solid waste. The opening  73  is covered by a small inset door  74  that is movable between a fully closed position and a fully opened position. Preferably, hinges  75  provided between the rear doors  70  and the inset doors  74  are angled relative to vertical to bias the inset doors  74  in the closed position. A handle  76  may also be provided to assist in opening the inset door  74 . 
     The preferred embodiment of the universal dumpster  30  described above has at least three advantages. First, the open upper door  62  and the open lower door  64  define a funnel that directs the solid waste into the hopper H of the front loading truck F. The funnel prevents the solid waste from being accidentally dispersed into the surrounding environment as the dumpster  30  is being emptied into the hopper H of the front loading truck F, as illustrated in FIG.  7 . Second, because the dumpster  30  is emptied through an end wall  60  instead of the top, the dumpster  30  empties with a reduced lifting angle L relative to horizontal. More specifically, the front loading truck F does not have to rotate the dumpster  30  to a substantially inverted position as is required with a conventional front loader dumpster. Accordingly, the lifting angle L generates little or no torque reversal. As a result, the dumpster  30  may be made considerably larger than a conventional front loader dumpster. Third, the universal dumpster  30  of this preferred embodiment may be emptied from either end by a conventional roll-off truck R, as illustrated in FIGS. 8A and 8B. 
     Another preferred embodiment of the invention is shown in FIGS. 9-11. As previously mentioned, angled side portions  51  of side walls  50  allow dumpster  30  having the width of a conventional rear loading dumpster to be emptied into the hopper H of a conventional front loading truck F. This preferred embodiment utilizes pick up sleeves  56  positioned on the interior surface of side walls  50  in the space between the ramp  48  and the floor plate  42 . In order to accommodate the sleeves  56 , the space between the ramp  48  and the floor plate  42  is enlarged by the addition of a ramp portion  48   a.  Ramp portion  48   a  is positioned at less of an angle relative to the floor  40  than that of ramp  48 . Preferably, when the downwardly opening lower door  64  is in the fully opened position, the angle of the front panel  64   a  relative to the floor  40  corresponds to the angle of the ramp portion  48   a  relative to the floor  40 . Side panels  65  of lower door  64  overlap the interior surface of side walls  50  of the dumpster  30 . 
     Another preferred embodiment of the invention is shown in FIGS. 12 and 13. This preferred embodiment also utilizes a downwardly opening lower door  64  comprising side panels  65  that overlap the interior surface of side walls  50  of the dumpster  30 . 
     Another preferred embodiment of the invention is shown in FIGS. 15-18. In this preferred embodiment, at least one of the end walls  60  of the dumpster  30  is formed by a pair of large front doors  80  attached to the side walls  50  by vertical hinges  82  such that the doors  80  are movable between a fully closed position and a fully opened position. Preferably, each door  80  is biased in the closed position by one or more pre-tensioned torsion springs  83  located along the hinge line formed between the side wall  50  and the end wall  60 . Each door  80  comprises an arcuate floor panel  84  that is attached to the base of the door  80  at an angle relative to the floor  40  that corresponds to the angle of the ramp  48  relative to the floor  40  of the dumpster  30 . When the doors  80  are in the fully opened position, the floor panels  84  overlap one another to form an extension of the ramp  48 . In the closed position, the floor panels  84  retract into the open space  85  between the ramp  48  and the floor plate  42 , as best shown in FIG.  17 . In the fully opened position, the ramp  48 , doors  80  and floor panels  84  define a funnel for discharging the solid waste from the interior compartment of the dumpster  30 , as previously described. 
     Another preferred embodiment of the invention is shown in FIGS. 19-22. In this embodiment, at least one of the end walls  60  is formed by a pair of large front doors  90 . The doors  90  are attached to side wall extension panels  92  by vertical hinges  94  such that the doors  90  are movable between a fully closed position and a fully opened position. Preferably, each door  90  is biased in the closed position by one or more pre-tensioned torsion springs  95  located along the hinge line formed between the side wall extension panel  92  and the door  90 . Each side wall extension panel  92  is attached along its base to a floor ramp extension panel  96 . The side wall extension panels  92  are connected to telescoping rods  97  which slide between a fully extended position and a fully retracted position to allow the side wall extension panels  92  and the floor ramp extension panel  96  to alternatively telescope outwardly from the dumpster  30  and retract back into the interior compartment of the dumpster  30 . The telescoping rods  97  are mounted for movement in sleeves  98  that are fixed to the exterior surface of side walls  50  of the dumpster  30 . Preferably, each of the telescoping rods  97  is biased in the fully retracted position by a coil spring  99 . The end of the rod  97  is provided with a stop  97   a  to prevent the side wall extension panel  92  from extending too far. In the fully retracted position, the side wall extension panels  92  overlap the interior surface of the side walls  50  and floor ramp extension panel  96  overlaps the interior surface of the ramp  48  so that the dumpster  30  is available for receiving solid waste in the interior compartment. As the dumpster  30  is tilted for emptying, the side wall extension panels  92  and the floor ramp extension panel  96  slide outwardly from the dumpster  30  as a unit. Once the side wall extension panels  92  and the floor ramp extension panel  96  are fully extended, the doors  90  open outwardly under the weight of the solid waste being discharged from the dumpster  30 . Together, the side wall extension panels  92 , the floor ramp extension panel  96  and the doors  90  form a telescoping discharge chute for guiding the solid waste out of the interior compartment of the dumpster  30 . 
     Preferably, dumpster  30  has a removable lid  100  which can be opened to allow access to the interior compartment of the dumpster  30  from above and can be closed to prevent refuse from blowing out of the dumpster  30  during transportation and during discharge of the solid waste from the interior compartment of the dumpster  30 . One embodiment of the lid  100  comprises a pair of hinged top doors  102 . The top doors  102  may be hinged at the end walls  60  or may be hinged at a medial location between the end walls  60  of the dumpster  30 . Each top door  102  of the lid  100  opens upwardly to allow access to the interior compartment of the dumpster  30  to deposit the solid waste. One or both top doors  102  of the lid  100  may also be removed entirely to allow the dumpster  30  to be utilized, for example, at a construction site to collect and contain large articles of debris, such as building materials. The dumpster  30  may be constructed without any lid  100  as shown in FIG.  12 . However, the lack of a lid  100  increases the likelihood that solid waste will be accidentally dispersed during discharge of the solid waste into the hopper H of a front loading truck F or during transportation by a roll-off truck R. In another preferred embodiment, shown in FIG. 13, the lid  100  of the dumpster  30  comprises a pair of top doors  106  hinged along the side walls  50  of the dumpster  30 . This preferred embodiment allows use of the dumpster  30  at a construction site, or other site where large articles of solid waste are generated, without having to remove any portion of the lid  100 . 
     In another preferred embodiment, shown in FIGS. 23 and 24, the dumpster  30  comprises a removable lid  110  for expanding the usable volume of the dumpster  30 . The lid  110  comprises end walls  112 , side walls  114  and a pair of top doors  116 . A retaining leg  118  provided at each bottom corner of the lid  110  cooperates with a hollow comer post  120  provided at each upper comer of the dumpster to secure the lid  110  on the dumpster  30 . A removable end wall cross bar  122  is also provided to support the end walls  60  of the dumpster  30  when the lid  110  is not in use. The cross bar  122  may be removed to prevent solid waste from catching between the hinged lower door  64  and the hinged end wall  112  during discharge when the lid  110  is in use. The end walls  112  and the side walls  114  of the lid  110  may be adapted for use with any of the preferred embodiments of the invention disclosed herein. 
     In some situations, it may be convenient to locate a dumpster  30  in a place that is not readily accessible to either a front loading truck F or a roll-off truck R. To accommodate these situations, the dumpster  30  could be fitted with wheels  130  and a removable trailer hitch  132  as shown in FIG.  25 . The wheels  130  and removable trailer hitch  132  permit the dumpster  30  to be moved to a location that is accessible to the refuse collection trucks so that the dumpster  30  may be emptied. 
     In yet another preferred embodiment, shown in FIGS. 26-29, the dumpster  30  reduces the forces exerted on the lifting arms A of a conventional front loading truck F. The dumpster  30  is substantially identical to the dumpster shown in FIGS. 1-8B except that the floor  40  does not comprise ramp  48  sloping upwardly from a medial point on the top side of the floor plate  42  in the direction of one of the end walls  60 . As a result, the torsion spring  66  is located nearer to the ground. Accordingly, the front loading truck F is not required to rotate the dumpster  30  quite as far to discharge solid waste from the interior compartment of the dumpster  30  into the hopper H of the front loading truck F (FIG.  29 ). In addition, the pickup sleeves  156  are rotatably mounted to the exterior surface of the side walls  50  adjacent the floor  40  of the dumpster  30 . The pickup sleeves  156  may be rotatably mounted to the side walls  50  in any known manner. As shown, each pickup sleeve  156  comprises a triangular-shaped pivot  160  mounted on a cylindrical trunnion pin  162  projecting outwardly from the side wall  50 . Sleeves  156  are interconnected by a relatively large diameter sleeve bar  164  extending transversely between the side walls  50  such that sleeves  156  and sleeve bar  164  form a generally U-shaped lifting tongue. 
     As previously described, the sleeves  156  are constructed to engage the lifting arms A of a conventional front loading truck F (FIG.  27 ). However, because the sleeves  156  are rotatably mounted to the side walls  50 , the sleeves  156  will be lying on the ground when the lifting arms A initially engage the sleeves  156  of the dumpster  30  (FIG.  27 ). As the lifting arms A fully engage the sleeves  156  and begin to lift the dumpster  30 , the sleeves  156  rotate about the pivots  160  on the trunnions  162 . As a result, the dumpster  30  is dragged in the direction of the front loading truck F until the sleeve bar  164  contacts feet  44  on the underside of the floor  40  of the dumpster  30 . Rotation of the sleeves  156  is terminated once the dumpster  30  has been lifted by the front loading truck F approximately sixty degrees relative to horizontal, as depicted by the broken lines in FIG.  28 . The front loading truck F continues to lift the dumpster  30  upwardly and rearwardly so that the dumpster  30  is substantially horizontal above the front loading truck F, as depicted by the broken lines in FIG.  29 . 
     It should be noted that because the sleeves  156  are rotatably mounted to the side walls  50 , the elevation of the dumpster  30  above the front loading truck F is reduced compared to the elevation of the dumpster  30 , as depicted in FIG.  7 . Accordingly, the center of gravity of the dumpster  30  is closer to the front loading truck F at both the beginning and during the initial stage of the lifting process, and less force is therefore exerted on the lifting arms A. As a result, the capacity of the dumpster  30  may be increased somewhat. The lifting arms A continue to lift and tilt the dumpster  30  rearwardly approximately 105 degrees until the weight of the solid waste in the interior compartment of the dumpster  30  automatically opens the lower door  64  against the torsion spring  66 , as previously described. The lower dumping position, as depicted by the solid lines in FIG. 29, permits the solid waste in the interior compartment of the dumpster  30  to be discharged deeper into the hopper H of the front loading truck F. 
     It is to be understood that the forgoing description and specific embodiments shown herein are merely illustrative of the best mode of the invention and the principals thereof, and that various modifications and additions may be made by those skilled in the art without departing unnecessarily from the spirit and scope of the invention, which is intended to be limited only by the scope of the appended claims.