Patent Publication Number: US-2013243555-A1

Title: Box Lifting Assembly for Dump Trucks or Similar Vehicles

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35USC§119(e) of U.S. provisional patent application 61/416,131 filed Nov. 22, 2010, the specification of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates to box lifting assemblies for dump trucks or similar vehicles. More precisely, the invention pertains to lifting assemblies for selectively loading a box onto a chassis of a vehicle and unloading the box from the chassis. The invention also pertains to a cargo-carrying vehicle provided with a lifting assembly and to a method for unloading a container mounted on a chassis of a vehicle from the vehicle. 
     BACKGROUND 
     Dump trucks are widely used for transporting loose material for construction, goods or waste. Usually, a dump truck has a chassis and a rear container, or box, which is tiltable, most often rearwardly, to allow the transported material to be dumped at a desired site through a rear opening. 
     It may be advantageous to transport the content of the box from one site to another. For instance, if the dump truck transports waste, it may be desirable to transport the waste to a disposal site such as a landfill or the like, which may be far away from the waste collection site or sites. 
     Unfortunately, such trucks are usually not adapted to travel great distances. They are therefore unpractical for transporting material from one site to another when the two sites are far apart. Moving the dump truck away from the collection site for extended periods of time may further be costly and may decrease productivity. 
     SUMMARY 
     According to one aspect, there is provided a lifting assembly for selectively loading a container onto a chassis of a vehicle and unloading the container from the chassis, the lifting assembly comprising: a frame connected to the chassis; an arm having a first end pivotably connected to the frame and a second end releasably connectable to the container; and a pivoting actuator having a first actuator portion pivotably connected to the frame and a second actuator portion pivotably connected to the arm between the first and second ends thereof, the second actuator portion being linearly movable relative to the first actuator portion for pivoting the arm relative to the frame to selectively move the container towards the frame and away from the frame. 
     In one embodiment, the frame is pivotably connected to the chassis. 
     In one embodiment, the lifting assembly further comprises a frame actuator pivotably connected to the chassis and to the frame for tilting the frame rearwardly relative to the chassis. 
     In one embodiment, the arm comprises an arm actuator having a first actuator portion located near the first end of the arm and a second actuator portion located near the second end of the arm, the first actuator portion being movable relative to the second actuator portion to allow the container to be selectively moved frontwardly and rearwardly relative to the frame. 
     In one embodiment, the arm actuator is a linear actuator. 
     In one embodiment, the arm actuator is a hydraulic cylinder. 
     In one embodiment, the arm comprises: a first link member pivotably connected to the frame; and a second link member pivotably connected to the first link member, the second link member being releasably connected to a front end of the container. 
     In one embodiment, the arm is movable between a folded position wherein the second link member is pivoted rearwardly relative to the first link member to form an angle therewith, and an unfolded position wherein the second link member is parallel to the first link member. 
     In one embodiment, the first link member is pivotable rearwardly relative to the frame to enable locating the second end of the arm rearwardly of the frame and orienting the second end of the arm towards a ground surface when the arm is in the folded position. 
     In one embodiment, the second link member is extendable for placing the front end of the container on the ground surface when the second end of the arm is located rearwardly of the frame and oriented towards the ground. 
     In one embodiment, the pivoting actuator is a linear actuator. 
     In one embodiment, the pivoting actuator is a hydraulic cylinder. 
     According to another aspect, there is also provided a cargo-carrying vehicle comprising: a container; a chassis for receiving the container thereon; and a lifting assembly for selectively loading the container onto the chassis and unloading the container from the chassis, the lifting assembly including: a frame connected to the chassis; an arm having a first end pivotably connected to the frame and a second end releasably connected to the container; and a pivoting actuator having a first actuator portion pivotably connected to the frame and a second actuator portion pivotably connected to the arm between the first and second ends thereof, the second actuator portion being linearly movable relative to the first actuator portion for pivoting the arm relative to the frame to selectively move the container towards the frame and away from the frame. 
     In one embodiment, the frame is pivotably connected to the chassis. 
     In one embodiment, the vehicle further comprises a frame actuator pivotably connected to the chassis and to the frame for tilting the frame rearwardly relative to the chassis. 
     According to yet another aspect, there is also provided a method for unloading a container mounted on a chassis of a vehicle from the vehicle, the method comprising: providing a lifting assembly comprising a frame connected to the chassis for supporting the container, and an arm having a first end pivotably connected to the frame and a second end releasably connected to a front end of the container; moving the container rearwardly to locate a rear end of the container rearwardly from the frame; pivoting the arm rearwardly until the front end of the container is located rearwardly from the frame; releasing the container from the arm. 
     In one embodiment, the arm comprises: a first link member pivotably connected to the frame; and a second link member pivotably connected to the first link member, the second link member being releasably connected to a front end of the container. 
     In one embodiment, the method further comprises: after pivoting the arm rearwardly, extending the second link member until the front end of the container abuts a ground surface. 
     In one embodiment, moving the container rearwardly comprises: placing the arm in an unfolded position wherein the second link member is parallel to the first link member and to the frame; retracting the second link member. 
     In one embodiment, the frame is pivotably connected to the chassis, and the method further comprises: tilting the frame rearwardly relative to the chassis to tilt the container rearwardly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be readily understood, embodiments of the invention are illustrated by way of example in the accompanying drawings. 
         FIG. 1  is a schematic drawing showing a side elevation view of a dump truck having a box connected thereto via a lifting assembly, in accordance with one embodiment, with the lifting assembly in the transport position. 
         FIG. 2  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the box removed therefrom and the lifting assembly deployed to show details thereof. 
         FIG. 3  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the frame tilted rearwardly. 
         FIG. 4  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the frame tilted rearwardly and the box spaced from the hopper. 
         FIG. 5  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the frame tilted rearwardly and the pivoting actuator slightly extended to pivot the arm rearwardly. 
         FIG. 6A  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the frame tilted rearwardly and the pivoting actuator further extended to further pivot the arm rearwardly and to thereby move the box away from the chassis. 
         FIG. 6B  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the pivoting actuator further extended and the whole arm pivoted rearwardly. 
         FIG. 7  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the lifting assembly deployed, the second link extended and the box resting on the ground surface. 
         FIG. 8A  is a drawing showing a side elevation view of the dump truck shown in  FIG. 1 , with the box resting on the ground near the deployed lifting assembly and detached therefrom. 
         FIG. 8B  is a drawing showing a side elevation view of a dump truck in accordance with an alternative embodiment in which the length of the frame is different than in  FIG. 8A , with the box resting on the ground near the deployed lifting assembly and detached therefrom. 
         FIG. 9  is a drawing showing a side elevation view of a dump truck having a box connected thereto via a lifting assembly, in accordance with yet another embodiment, with the frame spaced from the hopper and tilted rearwardly. 
         FIG. 10  is a drawing showing a side elevation view of the dump truck shown in  FIG. 9 , with the arm member pivoted rearwardly to thereby move the box away from the frame. 
         FIG. 11  is a drawing showing a side elevation view of the dump truck shown in  FIG. 9 , with the frame actuator extended to further pivot the arm member rearwardly. 
         FIG. 12  is a drawing showing a side elevation view of the dump truck shown in  FIG. 9 , with the arm actuator extended to lower the front end of the box towards the ground surface. 
         FIG. 13  is a drawing showing a side elevation view of the dump truck shown in  FIG. 9 , with the frame spaced from the hopper and the frame actuator extended to tilt the frame rearwardly in order to position the wheels of the box onto an elevated receiving surface. 
         FIG. 14  is a drawing showing a side elevation view of the dump truck shown in  FIG. 9 , with the pivoting actuator extended to pivot the arm member rearwardly until the box rests generally horizontally on the elevated receiving surface. 
         FIG. 15  is a drawing showing a side elevation view of a trailer coupled to a tractor unit, in accordance with one embodiment, with a plurality of boxes positioned on the trailer. 
         FIG. 16  is a drawing showing a side elevation view of a dump truck in accordance with yet another embodiment, coupled to a trailer on which a box is received. 
         FIG. 17  is a drawing showing a side elevation view of a dump truck in accordance with yet another embodiment, coupled to a trailer on which a plurality of boxes are received. 
         FIG. 18  is a drawing showing a side elevation view of a dump truck, in accordance with yet another embodiment, with the lifting assembly in the transport position. 
         FIG. 19  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the box moved rearwardly and spaced from the hopper. 
         FIG. 20  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the pivoting actuator extended to pivot the arm rearwardly. 
         FIG. 21  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the pivoting actuator further extended to further pivot the arm rearwardly. 
         FIG. 22  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the pivoting actuator further extended and the whole arm pivoted rearwardly. 
         FIG. 23  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the pivoting actuator extended as shown in  FIG. 22  and with the arm actuator partially extended. 
         FIG. 24  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the pivoting actuator and the arm actuator further extended such that the front end of the box abuts the ground surface. 
         FIG. 25  is a drawing showing a side elevation view of the dump truck shown in  FIG. 18 , with the box resting on the ground near the deployed lifting assembly and detached therefrom. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     In the following description of the embodiments, references to the accompanying drawings are by way of illustration of an example by which the invention may be practiced. It will be understood that other embodiments may be made without departing from the scope of the invention disclosed. 
     Referring to  FIGS. 1 and 2 , there is provided a dump truck  100  comprising a cab  102  and a chassis  104 . In the illustrated embodiment, the dump truck  100  further comprises a container or box  106  having a front end  108  and a rear end  110 , and a hopper  112  mounted on the chassis  104  between the cab  102  and the box  106 . The box  106  may be of the type known in the art and may comprise a rear door  114  to allow unloading of loose material, such as material used for construction, goods or waste therethrough. 
     The box  106  and the hopper  112  are connected to the chassis  104  via a lifting assembly  150  which allows the box  106  to be selectively loaded onto the chassis  104  and unloaded from the chassis  104 . More specifically, the lifting assembly  150  comprises a frame  200  connected to the chassis  104  and adapted for resting on the chassis  104 , and an actuating assembly  202  for tilting the frame  200  and moving the box  106  relative to the frame  200 . 
     In the embodiment illustrated in  FIGS. 1 and 2 , the frame  200  has a front end  260 , a rear end  262  and an upper receiving surface  264  extending between the front end  260  and the rear end  262  for receiving the box  106  thereon. The hopper  112  is located at the front end  260  of the frame  200  and is secured thereto. The rear end  262  is pivotably connected to the chassis  104  via a rear pivoting axle  266  to allow the frame  200  to be tilted rearwardly, as will be further appreciated below. 
     Still in the illustrated embodiment, the actuating assembly  202  comprises a first linear actuator, or frame actuator  204 , for tilting the frame  200  rearwardly. More specifically, the frame actuator  204  has a first portion  206  pivotably connected to the chassis  104  and a second portion  208  pivotably connected the front end  260  of the frame  200 . The first portion  206  is telescopically movable relative to the second portion  208 . In a first or transport position, in which the frame  200  rests on the chassis  104 , the frame actuator  204  is retracted. When the frame actuator  204  is extended, the front end  260  of the frame  200  is moved upwardly, away from the chassis  104 , and the frame  200  is pivoted relative to the chassis  104  about its rear end  262 . This configuration allows the dump truck  100  provided with the lifting assembly  150  described herein to function as a regular dump truck, as one skilled in the art will appreciate. 
     In the embodiment illustrated in  FIGS. 1 to 8A , the rear pivoting axle  266  connecting the frame  200  to the chassis  104  is not located at the rear end  262  of the frame  200 , but is instead spaced from the rear end  262  of the frame  200 . More specifically, the frame  200  is longer than the chassis  104  and sticks out rearwardly from the chassis  200  when the frame  200  rests on the chassis  104 . In an alternative embodiment shown in  FIG. 8B , the dump truck  100  comprises a frame  800  pivotably connected to the chassis  104  via a rear pivoting axle  802  which is located substantially at a rear end  804  of the frame  800 . In this configuration, when the frame  800  rests on the chassis  104  in the transport position, the rear end  804  of the frame  800  is substantially vertically aligned with a rear end  806  of the chassis  104 . It will be appreciated that in yet another embodiment, the rear pivoting axle may instead be positioned along the frame at an alternative position which the skilled addressee may deem suitable in order to allow the frame to be tilted rearwardly relative to the chassis  104 . 
     Referring back to  FIGS. 1 and 2 , the actuating assembly  202  further comprises an arm  210  removably connecting the box  106  to the frame  200 . In one embodiment, the arm  210  is articulated and comprises a first link member  212  having a first end  214  pivotably connected to the frame  200  via an arm pivoting axle, not shown, and a second end  216 . The arm  210  further comprises a second link member  220  having a first end  222  pivotably connected to the second end  216  of the first link member  212  via an arm pivot  224  and a second end  226  releasably connected to the front end  108  of the box  106  via a box attachment member  228 . Since the arm  210  is articulated, it may be moved between an unfolded position in which the second link member  220  is parallel to the first link member  212 , as shown in  FIGS. 1 ,  3  and  4 , and a folded position in which the second link member  220  is pivoted rearwardly relative to the first link member  212  to form an angle with the first link member  212 , as shown in  FIGS. 2 and 5  to  8 A. 
     In one embodiment, the box attachment member  228  comprises a hook member  230  configured to allow the box  106  to be relatively easily detached from the arm  210  when the box  106  is unloaded from the dump truck  100  and rests on a receiving surface, such as a ground surface, as will become apparent below. Alternatively, the box attachment member  228  may comprise a hook-and-latch mechanism manually operable by a user to allow the user to manually detach the box  106  from the arm  210  once the box  106  has been unloaded from the dump truck  100  and rests on the ground surface. 
     In the illustrated embodiment, the first link member  212  further comprises an abutment portion  232  located proximal to the arm pivot  224 . The abutment portion  232  is positioned to prevent the second link member  220  from being completely folded against the first link member  212  in a jackknife-like fashion. 
     In one embodiment, a stop member  240  is further secured to the frame  200 , below the first link member  212  of the arm  210 , to allow the first link member  212  to abut thereagainst in order to prevent it from pivoting below the frame  200 , as will be further explained below. 
     In the illustrated embodiment, the second link member  220  is a second linear actuator, or arm actuator  242 , and comprises an actuator sleeve  244  an elongated inner member  245  telescopically engaged in the actuator sleeve  244  and linearly movable relative thereto. 
     The actuating assembly  202  further comprises a third linear actuator, or pivoting actuator  246 , for pivoting the arm  210  relative to the frame  200 . The pivoting actuator  246  comprises a first or front end  248  pivotably connected to the frame  200 , near the hopper  112  thereof, and a second or rear end  250  pivotably connected to the actuator sleeve  244  of the arm actuator  242  via an intermediate pivot  252 . When the pivoting actuator  246  is extended, it allows the arm  210  to be first positioned in the folded position. By further extending the pivoting actuator  246 , the arm  210  may be positioned such that the second end  226  of the second link member  220 , releasably connected to the front end  108  of the box  106 , is located rearwardly of the frame  200 , as shown in  FIG. 6B . In this configuration, the frame  200  is no longer under the box  106 , to allow the box  106  to be lowered towards the ground surface. 
     Furthermore, still in this configuration, the second end  226  of the second link member  220  is also oriented towards the ground surface, as further shown in  FIG. 6B . This allows the front end  108  of the box  106  to be lowered onto the ground surface by extending the arm actuator  242  until the front end  108  of the box  106  abuts the ground surface, as shown in  FIG. 7 . 
     In one embodiment, the frame actuator  204 , the arm actuator  242  and the pivoting actuator  246  all comprise hydraulic actuators, which allow a relatively precise control of the speed of each movement, while allowing for boxes containing heavy loads to be moved. Alternatively, the frame actuator  204 , the arm actuator  242  and the pivoting actuator  246  may instead comprise any other type of linear actuators deemed suitable by the skilled addressee, such as pneumatic actuators and the like. 
     A connecting device  234  may further be provided for releasably connecting the box  106  to the hopper  112  to selectively prevent the box  106  from moving relative to the hopper  112  during tilting of the frame  200 , or during the collection and/or transportation of the contents by the truck as will become apparent below. In the illustrated embodiment, the connecting device  234  comprises a hook member  236  configured to selectively engage a latch member  238  secured to the box  106 . The hook member  236  may be pivotably, linearly, or otherwise connected to the hopper  112  by a rotary, linear, sliding or other actuator to allow the box  106  to be remotely detached from the hopper  112 , as will be further explained below. 
     In one embodiment, the lifting assembly  150  further comprises a controller operatively connected to the connecting device  234 , to the frame actuator  204 , to the arm actuator  242  and to the pivoting actuator  246  to allow the lifting assembly  150  to be operated remotely by the user. For instance, the controller may be located inside the cab  102  of the dump truck  100  to allow a driver of the dump truck  100  to selectively load the box  106  onto the frame  200  and unload the box  106  from the frame  200  without having to exit the cab  102 . Alternatively, the controller may be accessible from outside the dump truck  100  and be operable by a user standing next to the dump truck  100 . 
     With reference to  FIGS. 3 to 8A , the operation of unloading the box  106  from the dump truck  100  using the lifting assembly  150  will now be described, in accordance with one embodiment. 
     In a starting or transport position, the frame actuator  204  is retracted such that the frame  200  rests on the chassis  104 , generally horizontally, and the box  106  rests on the frame  200 . The arm  210  is unfolded and extends along the frame  200 . The arm actuator  242  is in an extended position and the pivoting actuator  246  is in a retracted position such that the second end  226  of the second link member  220  is located proximal to the hopper  112 , with the box attachment member  228  engaging the box  106 . In this position, the box  106  is positioned adjacent the hopper  112 , and the connecting device  234  connects the box  106  to the hopper  112 . 
     According to one step illustrated in  FIG. 3 , the frame actuator  204  is extended to move the front end  260  of the frame  200  upwardly in order to pivot the frame  200  about the rear pivoting axle  266 , thereby tilting the frame  200  rearwardly. 
     According to another step illustrated in  FIG. 4 , the connecting device  234  is disconnected to release the box  106  from the hopper  112 . The arm actuator  242  is then retracted to move the box  106  rearwardly, in order to locate the rear end  110  of the box  106  rearwardly from the rear end  262  of the frame  200 . The box  106  is thereby moved rearwardly until the box  106  contacts the ground surface. In one embodiment, the box  106  comprises a plurality of wheels  300  rotatably mounted to the rear end  110  thereof for facilitating movement of the rear end  110  of the box  106  on the ground surface during loading of the box  106  onto the dump truck  100  and unloading of the box  106  from the dump truck  100 . In this embodiment, the arm actuator  242  is retracted until the plurality of wheels  300  contact the ground surface or until the actuator reaches the end of its actuation path. 
     According to another step illustrated in  FIG. 5 , the pivoting actuator  246  is extended to pivot the second link member  220  about the arm pivot  224  until the second link member  220  abuts the abutment portion  232  of the first link member  212 . During this step, the arm  210  is therefore moved from the unfolded position into the folded position. 
     According to yet another step illustrated in  FIGS. 6A and 6B , the pivoting actuator  246  is further extended. Since the second link member  220  abuts the abutment portion  232  of the first link member  212 , the second link member  220  is prevented from further pivoting about the arm pivot  224 . Instead, the whole arm  210 , including the first and second link members  212 ,  220 , pivots about the arm pivoting axle which connects the first link member  212  to the frame  200 . In this step, as the arm  210  pivots, the box  106  is lowered towards the ground surface while the first link member  212  is angled away from the frame  200 . As explained above, the second end  226  of the second link member  220  is now located rearwardly of the frame  200 , such that the frame  200  is no longer under the box  106 . 
     According to yet another step illustrated in  FIG. 7 , the arm actuator  242  is extended such that the elongated inner member  245  moves away from the actuator sleeve  244  to move the front end  108  of the box  106  towards the ground surface until the box  106  rests on the ground surface, generally horizontally. 
     According to yet another step illustrated in  FIG. 8A , the box attachment member  228  is disconnected from the box  106 . In one embodiment, the box attachment member  228  may be disconnected by moving the dump truck  100  forward. In an alternative embodiment, the pivoting actuator  246  is slightly retracted to move the box attachment member  228  away from the box  106 . In yet another embodiment, the box attachment member  228  is manually disconnected from the box  106  by the user. 
     To move the dump truck  100  to a travel position, the frame actuator  204  may then be retracted to lower the front end  260  of the frame  200  towards the chassis  104 . The pivoting actuator  246  may also be retracted to pivot the arm  210  forwardly towards the frame  200 . When the first link member  212  abuts the stop member  240  of the frame  200 , further pivoting of the first link member  212  is prevented. Further retraction of the pivoting actuator  246  then causes the second link member  220  to pivot about the arm pivot  224  towards its starting position along the frame  200 . 
     It will be appreciated that to load the box  106  onto the dump truck  100 , the steps described above may be performed in a reverse order. 
     With reference to  FIGS. 9 to 12 , there is provided a dump truck  100  having a lifting assembly  900  which allows the box  106  to be selectively loaded onto the chassis  104  and unloaded from the chassis  104 , in accordance with an alternative embodiment. 
     The lifting assembly  900  is substantially similar to the lifting assembly  150  shown in  FIGS. 1 to 8A , except that in this embodiment, the arm  210  comprises a single arm member  902  pivotably connected to the frame. More specifically, the arm member  902  comprises an arm actuator  904  having an actuator sleeve  906  pivotably connected to the frame  200  and an elongated inner member  908 , best shown in  FIG. 12 , telescopically movable relative to the actuator sleeve  906  and releasably attached to the box  106 . Still in this embodiment, the pivoting actuator  246  is pivotably connected to the frame  200  and to the actuator sleeve  906  of the arm member  902 . 
     The operation of unloading the box  106  from the dump truck  100  using the lifting assembly  900  will now be described. 
     In a starting or transport position, the frame actuator  204  and the pivoting actuator  246  are in a retracted position. The arm  210  is positioned along the frame  200  in the unfolded position, with the elongated inner member  908  located near the hopper  112 . The arm actuator  904  is in an extended position such that the box  106  is positioned adjacent the hopper  112 . 
     According to one step illustrated in  FIG. 9 , the connecting device  234  is disconnected to release the box  106  from the hopper  112 . The arm actuator  904  is then retracted to move the box  106  rearwardly, away from the hopper  112 . For example, in one embodiment, the box  106  is moved rearwardly by a distance of  48  inches. It will be understood that the actual distance by which the box is moved depends on the specific design of the embodiment and is non-limiting. The pivoting actuator  246  is then extended to pivot the arm member  902  rearwardly, away from the frame  200 , thereby pivoting the box  106  rearwardly until the plurality of wheels  300  of the box  106  contacts the ground surface. 
     According to another step illustrated in  FIG. 10 , the pivoting actuator  246  is further extended to further pivot the arm member  902 . Since the plurality of wheels  300  contact the ground, the box  106  is prevented from further pivoting and instead is moved rearwardly away from the chassis  104 . The arm member  902  is pivoted in this manner until the pivoting actuator  246  is fully extended to position the front end  108  of the box  106  rearwardly of the frame  200 , such that the frame  200  is no longer under the box  106 . In the illustrated embodiment, when the pivoting actuator  246  is fully extended, the arm member  902  is slightly angled upwardly relative to the frame  200 . 
     According to yet another step illustrated in  FIG. 11 , the frame actuator  204  is extended to tilt the frame  200  rearwardly. By doing so, the arm member  902  further pivots rearwardly relative to the chassis  104  and the front end  108  of the box  106  is moved downwardly towards the ground surface. As shown in  FIG. 11 , the arm member  902  is also oriented downwardly towards the ground surface in this step. 
     According to yet another step illustrated in  FIG. 12 , the arm actuator  904  is then extended until the front end  108  of the box  106  contacts or abuts the ground surface such that the box  106  rests on the ground surface, generally horizontally. The box attachment member  228  may then be detached from the box  106  as described above. 
     It will be appreciated that to load the box  106  onto the dump truck  100 , the steps described above may be performed in a reverse order. 
     With reference to  FIGS. 13 and 14 , the operation of unloading the box  106  from the dump truck  100  using the lifting assembly  900  will now be described, in accordance with an alternative embodiment. In this embodiment, the box  106  is unloaded onto a receiving surface  1300  which is located higher than the ground surface  1302 , generally at the same level as the chassis  104 . In one embodiment, the receiving surface  1300  is a trailer  1304  adapted to receive one or more boxes, such as the flat-bed semi-trailer  1500  shown in  FIG. 15 . In such an embodiment, the trailer  1500  may then be attached to a tractor unit  1502  to allow a plurality of boxes  1504  to be transported at once. Alternatively, the trailer  1500  may be directly attached to the dump truck  100 , and may be adapted to carry a single box  1600 , as shown in  FIG. 16 , or a plurality of boxes  1700 , as shown in  FIG. 17 . In yet another embodiment, the receiving surface may instead be an immobile elevated surface such as a loading dock. 
     According to one step illustrated in  FIG. 13 , from the transport position, the arm actuator  904  is retracted to move the box  106  rearwardly, away from the hopper  112 . In one embodiment, the box  106  is moved rearwardly. For example, the box could be moved rearwardly by a distance of  48  inches. It will be understood that the actual distance by which the box is moved depends on the specific design of the embodiment and is non-limiting. The frame actuator  204  is then extended to tilt the frame  200  rearwardly. In this position, the plurality of wheels  300  of the box  106  contacts the receiving surface  1300 . 
     According to another step illustrated in  FIG. 14 , the pivoting actuator  246  is then extended to pivot the arm member  902  rearwardly, thereby moving the front end  108  of the box  106  towards the receiving surface  1300  until the box  106  rests on the receiving surface  1300 . The box attachment member  228  may then be detached from the box  106  as described above. 
     It will be appreciated that to load the box  106  onto the dump truck  100 , the steps described above may be performed in a reverse order. 
     It will be appreciated that the lifting assembly described above allows the box to be completely removed from the dump truck, while still allowing the box to be tilted rearwardly to enable the dump truck to perform as a regular dump truck. 
     It will be appreciated that the sequences of steps listed above could be modified to change the order of the steps and/or to add and/or remove steps, depending on the specific design of the embodiment and on the choice of components. 
     Now referring to  FIGS. 18 to 25 , there is provided a dump truck  100  having a lifting assembly  1800  which allows the box  106  to be selectively loaded onto the chassis  104  and unloaded from the chassis  104 , in accordance with yet another embodiment. 
     This embodiment is substantially similar to the embodiment shown in  FIGS. 1 to 8A , except that in the present embodiment, the frame  200  is secured to the chassis  104  of the dump truck  100  and is not tilted. It could still be tiltable but in the sequence of steps which will now be described, it is not tilted. The frame  200  may even be part of the dump truck  100  and be integrally formed with the chassis  104 . Accordingly, in this embodiment, the lifting assembly  1800  does not necessitate a frame actuator. Instead, the lifting assembly  1800  comprises a pivoting actuator  1802 , best shown in  FIG. 20 , which is extended substantially further rearwardly than the pivoting actuator  246  shown in  FIGS. 1 to 8A  during operation of the lifting assembly  1800 . This allows the arm  210  to still be pivoted such that the second end  226  of the second link member  220  is located rearwardly of the frame  200  and is oriented towards the ground surface. 
     The operation of unloading the box  106  from the dump truck  100  using the lifting assembly  1800  will now be described. 
       FIG. 18  shows the lifting assembly  1800  in a starting or transport position, similar to the position shown in  FIG. 1 . In this position, the arm  210  is in the unfolded position, described above. 
     According to one step shown in  FIG. 19 , the connecting device  234  is disconnected to release the box  106  from the hopper  112 . The arm actuator  242  is then retracted to move the box  106  rearwardly, away from the hopper  112 . 
     According to another step shown in  FIGS. 20 and 21 , the pivoting actuator  1802  is extended to pivot the second link member  220  rearwardly relative to the first link member  212 , until the second link member  220  abuts the abutment portion  232  of the first link member  212 . 
     According to another step shown in  FIG. 22 , the pivoting actuator  1802  is further extended to pivot the first link member  212  of the arm  210  rearwardly, away from the frame  200 , to position the second end  226  of the second link member  220  rearwardly of the frame  200  such that the frame  200  is no longer under the box  106 . In the configuration illustrated in  FIG. 22 , the second end  226  of the second link member  220  is also oriented towards the ground surface. 
     According to another step illustrated in  FIG. 23 , the arm actuator  242  is then extended to further move the box  106  rearwardly, away from the frame  200 . 
     According to another step illustrated in  FIG. 24 , the pivoting actuator  1802  is further extended until the front end  108  of the box  106  abuts the ground surface. 
     Alternatively, the pivoting actuator  1802  may instead be fully extended, in the position shown in  FIG. 24 , before the arm actuator  242  is extended to lower the front end  108  of the box  106  until the front end  108  of the box  106  abuts the ground surface. 
     In yet another embodiment, the arm actuator  242  and the pivoting actuator  1802  are extended simultaneously to simultaneously move the box  1066  rearwardly and lower the front end  108  of the box  106  towards the ground surface. 
     According to another step illustrated in  FIG. 25 , the box  106  is then released from the arm  210 . 
     A person skilled in the art will further appreciate that the lifting assembly and the dump truck may alternatively be configured according to various other embodiments. For instance, the lifting assembly may alternatively be used on other types of cargo-carrying vehicles besides dump trucks, such as pick-up trucks or the like. 
     Although the above description relates to a specific preferred embodiment as presently contemplated by the inventor, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described herein. 
     The embodiments described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the appended claims.