Abstract:
An improved container dumping apparatus is described for automatically lifting residential refuse containers to an elevated position and dumping them into the elevated access area of a collection tank. A carriage with gripping arms is guided up the vertical portion of a set of tracks. The tracks transition into a curved portion at the top end which inverts the container over the access area through movement along the curved track. The carriage is self-powered by a hydraulic motor mounted on the carriage. The dumping apparatus uses an rack and pinion arrangement for forcibly elevating the carriage, with the rack being parallel to the set of tracks and the pinion mounted on the shaft of the motor on the carriage. A piston operated power assistance apparatus is located coincident with the curved portion of the track to engage the carriage as it approaches the curved portion, to provide additional power to aid movement of the carriage over the curved portion, and to control its speed.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application claims priority based upon the following provisional patent application: No. 60/143,597, filed on Jul. 13, 1999, of the same or similar title. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     This invention relates generally to an improved refuse loader and more particularly to an apparatus for lifting, tilting, and emptying on-site trash containers into the access area for a compartment of a mobile collection vehicle. 
     Mobile collection systems for the picking up trash, refuse, or recyclable articles at numerous and separated sites are well known to the art. These systems consist of a vehicle traveling a standard route and standard containers designed to be automatically picked up on-site and dumped into the vehicle by an apparatus associated with the vehicle. These standard sized collection containers all have the same capacity but capacities differ from system to system, usually from approximately 50 to 300 gallons. In practice, the on-site containers are filled by the user and periodically the contents of the container are transferred to a mobile collection vehicle for transportation to a dump, land fill, or recycling center. 
     In order to provide a mechanism for efficiently emptying the on-site containers into the collection vehicle, various devices can be found in the prior art. These devices generally incorporate a vertical mast or boom which supports a means for grasping the container which is resting on a level surface, elevating the grasping means and grasped container to the top of the mast, dumping the container into an access opening in the top of the collection compartment, and returning the grasped container to its original position. Most of these devices also have a means for extending the vertical mast or boom a distance from the vehicle to accommodate the variable distance between the vehicle and the container. 
     B. Description of Prior Art 
     The prior art is replete with various devices for elevating and dumping the contents of a grasped container into a collection vehicle. These devices used to perform these two functions fall generally into two categories, those using chain drives and those using lever arms, either articulated or non-articulated. 
     U.S. Pat. No. 3,910,434, issued on Oct. 7, 1975, to Ebeling, is an example of the chain drive device. The invention employs a continuous linked chain driven by sprockets, or gears, mounted at the top and bottom of the mast, whereby the container grasping means, connected by links to the chain, and grasped container are carried to the top and then over a semicircular shaped mast head. The mast is connected by horizontal supports to the frame of the collection vehicle so that the entire apparatus can be extended away from the collection vehicle a short distance in order to provide more precise positioning to the container. A disadvantage of this device is that it has a large number of moving parts, so that the chains wear and frequently break from the stress of use. 
     The second type of device is illustrated by U.S. Pat. No. 4,427,333, issued on Jan. 24, 1984, to Ebeling, in which the chain drive mechanism is replaced with an articulated arm arrangement powered by a hydraulic cylinder and piston. A special linkage operating in conjunction with the articulated arm assembly and having four separate axes of rotation within its parts rotates an upper arm so as to swing the container grasping means and grasped container up along guide tracks to the top of the mast where the container was tipped and its contents dumped into a collection vehicle. From a pivot point at the top of the mast, the articulated arm lifts the container grasping means and grasped container the vertical distance of the mast. Like the chain drive device, the entire apparatus can be extended from the collection vehicle by various means mounted to the frame of the collection vehicle, whereby the device can be positioned more precisely with relation to the container. However, this device has several disadvantages as well. First, the height of the arms as they swing over the top of the collection vehicle can cause vertical clearance problems in tightly restricted areas. Second, the number of pieces comprising the linkage creates problems of manufacturability and cost. Third, the design itself tends to be heavy and cumbersome and does not lend itself to downsizing for smaller, residential loads which, because of their reduced weight and bulk, can be serviced with a lighter device having commensurate less expense to manufacture. 
     All such refuse loading devices share another common problem, namely, as the container grasping apparatus traverses over the top portion of the mast, more force is required to move the container grasping apparatus. For the linear portion of the mast, the force vector necessary to lift the apparatus only has a vertical component since it is overcoming gravity only. However, when the apparatus changes direction as it begins to traverse the curved portion of the mast, a horizontal component of force is required, so that the vector sum of the original vertical force component and the increasing horizontal force component is now greater in magnitude than the magnitude of the original force. Thus, more power is required as the apparatus traverses the curved portion of the mast. 
     The use of chains, pulleys, and cables employed in the elevation mechanism all increase the part count and thus provide more opportunity for failure of a part. A rack and pinion gear is commonly known in the mechanical arts, as for example in the steering mechanism of cars. Such rack and pinion arrangements can be used for lifting objects, as illustrated by U.S. Pat. No. 5,558,181, issued on Sep. 24, 1996, to Bundo. In this invention, an elevator is driven by a plurality of pinions carried on the elevator cage which engage a plurality of vertical racks secured to the sidewalls of the elevator passage. A primary feature of this device is the presence of a crown gear driven by a screw shaft connected to a motor mounted on the elevator cage, thus creating an irreversible driving device; this arrangement prevents the cage from falling in the event of a motor failure. However, this invention does not suggest or teach the use of a single rack and pinion for such purposes, and emphasizes the irreversible aspect to the invention as a safety device to provide passive braking. 
     What is needed therefore is an apparatus for elevating a trash container and inverting it over the elevated access area of a compartment that will accomplish the following objectives: 
     1. Reduced requirements for horizontal and vertical clearance so that it may be operated within narrow alleyways and driveways in residential areas; 
     2. Reduced number of parts to aid in manufacturability and reduce expense; and 
     3. Reduced number of moving parts to improve repairability. 
     4. Controlled traversal of the container grasping means as it traverses the curved part of the apparatus to reduce centrifugal force on the container and thus reduce strain on the apparatus. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved apparatus for elevating a grasped container from a rest position on a level surface to an elevated position above the access area of a collection compartment and tipping the container so that the contents of the container falls by gravity into the access area. 
     Another object of the invention is to provide a method of controlling the speed of the container grasping apparatus as it traverses a curved portion of the elevating device which causes the container, along with the container grasping apparatus, to be inverted. 
     Another object of the invention is to provide a method of providing power to assist the container grasping apparatus as it traverses the curved portion of the elevating device which causes the container, along with the container grasping apparatus, to be inverted. 
     Another object of the invention is provide an improved means for mounting the invention to a trash collection vehicle. 
     Another object of the invention is to provide a means for mounting the invention to a trash collection vehicle in a location other than the under carriage so as to improve ground clearance for the vehicle which is so equipped. 
     Another object of the invention is to provide a trash elevation apparatus which has a reduced part count so as to aid in manufacturability, maintenance, and expense. 
     These objects of the invention are achieved by an apparatus consisting of an improved track assembly with a linear portion in a substantially vertical plane and with a curved portion at its upper end. The track assembly is supported by extendable, horizontal frame assembly at its upper end connected to the collection tank, and not connected at its lower end connected to the vehicle frame as heretofore. The improved track assembly supports and guides an improved carriage assembly having a self-contained motor which powers the carriage assembly vertically up and down the track assembly and arcuately over the curved top of the mast assembly. To assist movement of the carriage assembly over the curved portion of the track assembly and to control the speed at which the carriage moves over the curved portion, an improved dumping assembly is provided. It consists of a crank on one end of a rotatable tie bar for grasping trunions protruding from either side of the carriage assembly as the carriage assembly approaches the top of the vertical portion of the track assembly, and a piston connected to the opposing end of the tie bar through an arrangement of an articulated, pivotable yoke and offset mounts, whereby the carriage assembly is guided up and over the curved top portion of the track assembly by the crank, the container is upended, and its contents is dumped into the collection tank. The configuration of piston, yoke, and offset mount provides a unique means to, first, brake the momentum of the carriage assembly as it goes over the top of the track assembly and, second, to provide additional power to assist the movement of the carriage assembly as it transitions from a linear to an arcuate path. This configuration also does not extend beyond the confines of the track assembly and thus prevents clearance problems when the vehicle on which the apparatus is mounted travels through narrow streets and alleyways. 
     The method of moving the improved carriage assembly along the track assembly consists of a rack and pinion arrangement, whereby the rack extends the length of the mast and the pinion gear is mounted on the carriage assembly and self-powered by a motor within the carriage assembly. A pair of guide rails are provided on either side of the rack to hold the carriage assembly to the track assembly by means of wheels mounted on the carriage assembly and journeled into channels provided by the guide rails. This arrangement also maintains the pinion gear in close proximity to the rack so that the teeth of the rack and pinion mesh properly. The pinion gear also serves as a brake to prevent the carriage assembly from descending the track assembly when movement is arrested. 
     The vertical portion of the rack is a standard linear sheet of metal in which is stamped or formed a series of spaced ridges forming teeth. The curved rack portion of the rack consists of a unique arrangement of horizontal bars mounted between the guide rails and having the spacing which meshes the bars to the pinion gear. These bars allow the carriage to continue movement beyond the top portion of the track assembly and over the curved portion of the track assembly, by providing engagement points for the pinion gear in the carriage assembly. It is also believed that this arrangement aids manufacturability by removing the necessity of fabricating a curved rack portion from sheet metal which has a different spacing of teeth in the curved portion of the rack due to the rack&#39;s curvature. An additional advantage of this bar arrangement is that debris cannot build up on the curved portion of the rack but will fall between the bars. 
     A container grasping apparatus which is standard to the industry and commonly used is connected to the carriage assembly and powered by hydraulic means. 
     The manner in which the frame assembly is moved transversely is considered to be a unique and innovative part of the invention. A double piston arrangement is used to achieve movement and is powered by the same hydraulic system used to power the carriage assembly, the gripping assembly, and the power assistance assembly. The double piston arrangement is used in lieu of previous chain and sprocket mechanisms and/or nested channel arrangements, so as to achieve a more dependable, less breakage prone mechanism. 
     The improved trash handling apparatus thus described is believed to be more compact and lightweight than similar devices described heretofore, and improves manufacturability of the apparatus because of its reduced parts count and simplicity of construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a collection vehicle upon which the invention is mounted. 
     FIG. 2 depicts a rear view of collection vehicle and invention, with a cutaway portion so that the extension rail arrangement used in the invention may be seen, where the track assembly is horizontally extended from the collection vehicle to permit the container grasping means to engage a container (container not shown). 
     FIG. 3 shows a side view of the upper portion of the track assembly, on which the carriage assembly with gripping arms is depicted as it encounters the crank of the power assistance assembly while moving upwards, and the same carriage assembly with gripping arms is shown in phantom at its final tipped position. 
     FIG. 4 shows a frontal view of the upper portion of the track assembly with the rack assembly cut away so that the yoke of the power assistance may be discerned and with the piston removed for clarification. 
     FIG. 5 shows a top view of the track assembly with the rack assembly being cut away to allow viewing of the power assistance assembly. 
     FIG. 6 shows a detailed side of the upper portion of the track assembly with one guide rail being removed to allow viewing of the power assistance assembly in more detail. 
     FIG. 7 shows top view of the carriage assembly with the top panel cut away. 
     FIG. 8 shows a perspective view of the carriage assembly with the gripping assembly removed so that the pinion gear may be observed more easily. 
     FIG. 9 shows a close-up detail view of the distal end of the frame assembly to illustrate how the pads are attached to the frame assembly to maintain alignment during movement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a vehicle  10  on which a collection tank  15  is mounted. Collection tank  15  has a access area  20  near the front end  25  thereof for receiving trash, garbage, recyclables, or the like, and an end gate  30  for removal of the collection tank contents. A loader  35  for handling a container (not shown) is attached on one side of the collection vehicle  10 , handling being more specifically defined as engaging, elevating, dumping, and returning the container to a desired location. In the illustrated embodiment, the loader  35  is mounted on the passenger side of the collection vehicle  10 , but choice of passenger side or driver side is arbitrary. The loader  35  includes a track assembly  40 , a gripping assembly  45 , a carriage assembly  50 , a power assistance assembly  55 , and a frame assembly  60 . 
     Track assembly  40  is best seen by reference to FIGS. 2,  6 , and  8 . As can be seen in the figures, track assembly  40  includes two spaced apart guide rails  65 , each having a linear portion  66  from the lower end of the guide rail  65  and a curved portion  70  spaced shaped as a semi-circle having center of curvature  610  and terminating in the proximity of the access area  20  of vehicle collection tank  15 . The curved portion  70  of each guide rail  65  is rigidly supported by a horizontal brace  67  welded to the guide rail  65  and extending inwardly and by an angled brace  68  welded to guide rail  65  and extending inwardly, both of which meet at the center of curvature  600  of the curved portion  70 . An inner flange  73  and an outer flange  72  are formed on edges of the guide rails  65  to form opposed, outwardly facing channels  75 , which in turn receive rollers  80  associated with the carriage assembly  50 . Rack  85  is interposed between guide rails  65  and set a constant distance from the outer surface of guide rails  65  along its length. Rack  85  may be constructed in a number of different ways. In its simplest form, rack  85  may be a corrugated piece of sheet metal with the corrugations formed so as to mesh with pinion gear  90  in carriage assembly  50 , discussed later. It can also be more solidly constructed by welding a series of parallel bars to a planar piece of sheet steel or aluminum, spaced appropriately to form teeth of the rack  85 . Teeth can also be formed by molding a gear-like surface on a metal substrate or by attaching appropriately formed teeth my standard means known to the industry, such as by welding, rivets, rearwardly inserted bolts, machining, press forming, and the like. Optionally, a series of stiffening members (not shown), such as rods, channel iron, box beams, and the like, can be inserted along the rear surface of rack  85  along the linear portion  66  of guide rails  65  and welded to the inner surfaces of guide rails  65  for additional structural support. Use of such stiffening members for supporting rack  85  as well as for maintaining a constant separation between guide rails  65  will permit a narrower rack and pinion gear combination to be used, since the rack would not necessarily be required to abut the inner sides of guide rails  65 . 
     The rack assembly takes on a different form along the curved portion  70  of guide rails  65 , as best seen in FIGS. 5 and 6. Horizontally oriented rack bars  95  are inset the same distance as the teeth on rack  85  and spaced along the circumference of curved portion  70 , to allow the teeth of pinion gear  90  to mesh with rack bars  95 . Use of such rack bars allows pinion gear  90 , after leaving rack  85  when carriage assembly  50  traverses the curved portion  70  of guide rails  65 , to properly mesh with rack  85  on the return traversal. 
     The frame assembly  60  is now described, with reference to FIGS. 2,  4 ,and  9 . The frame assembly  60  serves as the sole point of support for the downwardly hanging track assembly and connects loader  35  to collection tank  15  at its topmost portion. The main frame structure is rectangular and comprised of main support member  100 , inner support member  105 , left channel member  110 , and right channel member  115 . Channel members  110 ,  115  run transverse the vehicle and are parallel with one another with channels outwardly oriented with relation to the interior of the rectangle so formed by members  100 ,  105 ,  110 ,  115 . Track assembly  40  is carried by main support member  100  as by welding the guide rails  65  to the outwardly facing surface of main support member  100 . Main gussets  120  are provided to connect guide rails  65  to main support member  100  by providing additional welding surface area and support. Channel members  110 ,  115  are each supported by two frame rollers  125 , each roller being supported on a bearing  126  and axially mounted on a bolt  127 . The location of the innermost two frame rollers  125  is shown best in FIG.  2 . The outermost frame rollers  125  are not shown but are positioned generally at the outermost extent of the tank body. The placement of the rollers is not critical nor is their spacing along channel members  110 ,  115 . Transverse movement of the frame assembly  60  is achieved by use of a double piston assembly  130 , consisting of two opposed pistons  131 ,  132 , the bodies of which are rigidly connected together as by welding. The piston rod of rear facing piston  131  is attached to bracket  133  on the wall of the tank body opposite loader  35 , and the piston rod of forward facing piston  132  is connected to bracket  134  on right channel member  115 . Transverse movement of frame assembly is achieved by simultaneous expansion and simultaneous contraction of pistons  131 ,  132  against one side of the rectangular frame. In order to ensure that the force applied against right support member  115  does not skew the member as against rollers  125  journeled therein, a fin  140  the same length as right channel member  115  is rigidly attached to the bottom flange comprising right channel member  115  as by welding. An outer guide bar  146  and an inner guide bar  147 , each also having the same length as right channel member  115 , are positioned parallel to and on either side of fin  140 . Outer guide bar  146  is supported along its length by a number of rail brackets  149  spaced along its length and attached to the outer guide bar  146  as by welding. Inner guide bar  147  is similarly supported, either directly on a wall of the collection tank or by suitable brackets (not shown). Two pads  148  composed of a suitable resilient material, such as plastic, are interposed between the fin  140  and the respective guide bars  146 ,  147  at the distal end  142  of right channel member  115 , so that the distal end  142  is kept in alignment with the proximal end  141  as force is applied to move frame assembly  60 . 
     The carriage assembly  50  is best described with reference to FIGS. 7 and 8. The gripping assembly  45  is mounted to the carriage assembly  50  for movement along the length of the track assembly  40  by means of a roller connection to each of the guide rails  40 , as best seen in FIGS. 7 and 8. Carriage assembly  50  is formed of a structure having a front panel  160  with sufficient width to span the track assembly  40  and two side panels  165 , each side panel  165  having an inwardly directed shaft  81  at its uppermost end and an inwardly directed shaft  81  at its lowermost end. An inwardly directed roller  80  is journaled on each of the several shafts  81 . The outermost side of each guide rail  65  has an inturned outer flange  72  and an inturned inner flange  73  which form a channel  75  to guide the rollers  80  of the carriage assembly  50  as it traverses the track assembly  40 . A horizontally oriented pinion gear  90  is contained in the carriage assembly  50  so that the pinion gear  90  meshes with rack  85 . Each end of the axis of pinion gear  90  is connected to the rotating shaft  175  of a hydraulic motor  170 . Although a single motor of electrical or hydraulic configuration may be used, the described embodiment has been found to have superior balance and power characteristics and is considered to be the best mode for powering carriage assembly  50 . Each hydraulic motor has a supply fitting  171  and a return fitting  172  for supplying hydraulic fluid to the motor for powering it; the method of controlling the motors is well known to the art and not described here. A pair of trunions  180  horizontally extend from approximately the middle of carriage side panels  165 , the trunions  180  for detachable engagement with a pair of cranks as described later. A pair of outwardly directed rings  185  are provided to serve as a horizontal axis about which the gripping assembly rotates upwardly. A pair of support tabs  190  are also provided to serve as supports for the gripping assembly  45 . A pair of upper mounting lugs  195  are provided as points of attachment the vertical control piston  200  (FIG. 2) associated with the gripping assembly  45 . The upper mounting lugs  195  have opposed holes suitable for insertion of a retaining pin (not shown) which captures an end of the vertical control piston  200 . 
     Another embodiment of the drive mechanism of the carriage assembly  50  is the use of a gear box employing a worm gear driving a crown gear arrangement interposed between the shaft  175  of the motor  170  and the axis of the pinion gear  90  (not shown in figures). Such an arrangement would provide an additional safety feature for the carriage assembly  50 , such that, in the event of a motor failure, gravity would not cause the carriage assembly to forcefully and rapidly fall to the bottom portion of the track assembly  40 . The presence of a worm gear and crown gear arrangement would prevent gravitational force exerted on the carriage assembly from being transmitted back through the pinion gear to the motor, since the worm and crown gear arrangement is not reversible. However, this embodiment is not preferred for the application on trash collection vehicles; the presence of such a gear box would force a hydraulic motor run at high speeds in order to overcome the gear ration presented by the gear box and provide an acceptable speed of operation for the carriage assembly. Such an embodiment might be more acceptable for larger elevating applications in which the weight being moved would preclude rapid movement. 
     The gripping assembly  45  enables a container resting on a level surface to be securely grasped and held by the loader  35  for lifting, tilting, and emptying the container&#39;s contents into the access area  20  of collection tank  15 . Referring to FIGS. 1,  2 , and  5 , the gripping assembly  45  is mounted on the carriage assembly  50  by means of two posts  205  having holes in their upper ends sufficient to accommodate rings  185  therein for upward tilting of the gripping assembly. This upward tilting is accomplished by vertical control piston  200  which is attached on its one end by lower mounting lugs  210  associated with the gripping assembly  45  and to upper mounting lugs  195  associated with the carriage assembly  50 . Gripping assembly  45  includes a pair of oppositely disposed gripping arms  215  and  216 , each having an inner surface which engages the exterior surface of a generally cylindrical container. Clearly, the configuration and shape of the gripping arms will vary depending upon the shape and size of the container used; in this embodiment, the arcuate shape of the gripping arms is suitable for cylindrical containers. The inner ends of each gripping arm  215 ,  216  terminate with a arm mounting bracket  220  having a vertical hole for pivotal attachment to the gripping assembly. Hydraulic actuators  225 ,  225  are attached between the gripping arms  215 ,  216  and the gripping assembly body so that the gripping arms may open and close with sufficient clearance to encircle and capture a container. 
     This general description of the gripping assembly is only indicative of many such devices well known to the art. One such gripping assembly is described in the aforesaid U.S. Pat. No. 3,910,434; another is described in the aforesaid U.S. Patent RE 34,292 (a reissue of U.S. Pat. No. 5,049,026, by Bingman et al.). The gripping assembly is not essential to the inventive concept and is included only for completeness. 
     The structure of the power assistance assembly can best be understood with reference to FIGS. 3,  4 ,  5 , and  6 . A crank  300  having a slot  305  for engagement with trunion  180  is connected to the curved end  310  of tip beam  315  which pivots about axis of rotation  610  common with the center of curvature of curved portion  70  of guide rail  65 . The lower portion of crank  300  is notched to rest on the main support member  100  when at rest, and the curved end of tip beam  315  is similarly structured to rest on main support member  100 . Tip beam  315  is positioned on the outer side of angled brace  68 , horizontal brace  67 , and guide rail  65 , and is configured for rotation by mounting on a cam follower  320  which serves as a bearing. An identical arrangement of crank  310  and tip beam  315  assembly is configured for the other guide rail  65  and joined at the upper end of cranks  310  by a tie bar  325  passing over both guide rails  65 . The non-curved ends of tip beams  315  are joined together by a tie plate  330 , which passes interior to the curved portions  70  of guide rails  65  and below angled brace  68 . Tie bar  325  and tie plate  330  maintain the pair of tip beams  315  and pair of cranks  310  in parallel alignment. Attached to tie plate  330  are two yoke supports  335  extending parallel to tip beams  315 . Spacer blocks  336  parallel to tie plate  330  and spaced therefrom maintain alignment and provide structural support for yoke supports  335 . Yoke  340  is pivotably interposed between the free ends of yoke supports  335  and rotates about axis of rotation  620 . The bight of yoke  340  receives one end of power piston  345 , the opposite end of which is pivotably disposed about a horizontal shaft  346  interposed between two vertical plates  347  which in turn are supported by two horizontal box beam piston supports  348  extending between the interior surfaces of the curved portion of guide rails  65 . The power assistance assembly  55  is configured so that, when the tip beam  315  and crank  310  is resting on main support member  100 , as depicted in FIG. 6, the axes of rotation for the tip beam  315 , yoke  340 , and power piston  630  are all aligned along centerline  640 . Power piston  340  cannot be extended because of the alignment of axes. 
     All activities of the improved refuse collection system, to include (1) lateral extension of loader  35  from the vehicle  10 , (2) reciprocal movement of the carriage assembly  50  on the track assembly  40 , (3) grasping and releasing activity of the gripping assembly  45 , and (4) assistance to movement of carriage assembly  50  over the curved portion  70  of the guide rails  65 , are all accomplished by means of the same hydraulic control system. Such control systems are operable from the cab of vehicle  10  using standard ring and lever means. Design of an appropriate hydraulic system is considered to be well known to the industry and not presented here. 
     The operation of the apparatus will now be described. When vehicle  10  has been positioned adjacent to a container, the loader  35  is extended laterally to engage container with the container gripping arms  215 ,  216 . As stated previously, this gripping operation may be effected with any suitable mechanism. In the illustrated embodiment, the track assembly  40  is extended laterally by expansion of double piston assembly  130  which urges the frame assembly  60  supporting track assembly  40  to move outwardly along rollers  125  and engagement with the container is effected. Subsequent retraction of the track assembly toward the vehicle is effected in order to bring the container into a correct final position adjacent to vehicle  10 . 
     Elevation of the gripping assembly  45  along with the container is initiated by applying power to each of hydraulic motors  170  which cause pinion gear  90  to rotate and advance the carriage assembly  50 , and consequently gripping assembly  45  with its held container, upwards along the rack  85 . As the carriage assembly  50  approaches the uppermost end of the linear portion  66  of track assembly  40 , the trunions  180  are brought into contact with slots  305  in cranks  300 . The power assistance assembly is at the rest, or ready, position as depicted in FIG. 6 with pressure applied to power piston  345 . 
     Trunion  180  enters slot  305  and exerts upward pressure on crank  300 . This upward pressure urges tip beam  315  into clockwise motion, as seen from FIG.  6 . This motion causes a hydraulic valve (not shown) to shift, diverting hydraulic fluid from motors  170  to the power piston  345 . Simultaneously the motion brings yoke supports  335  down, which also moves yoke axis  620  downward and out of alignment with the other two axes  610 ,  630 , thus allowing power piston  345  to expand to produce a clockwise torque about axis  610  to assist movement of the carriage assembly  50  over the curved portion  70  of guide rails  65 . With the assistance of power piston  345 , the carriage assembly  50  is advanced over the curved portion  70  of guide rails  65 , thus upending the container held by gripping assembly  45  so that the contents of the container are emptied into the access area  20  of the collection tank  15 . The final orientation of carriage assembly  50  is shown in phantom lines on FIG.  3 . Carriage assembly  50  is brought back down the track assembly  40  by reversing the process while it is in the final position, that is, forcibly collapsing power piston  345  so that tip beam  315  is moved in a counterclockwise direction to exert a reverse force against the trunions  180  of carriage assembly  50 . 
     While only a preferred embodiment has been illustrated and described, obvious modifications may be made within the scope of this invention and the following claims without substantially changing its functions. Accordingly, the scope of the invention should be determined not by the embodiments illustrated but by the appended claims and their legal equivalents.