Patent Publication Number: US-9403641-B1

Title: Side loader arm for refuse collection vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application claims the benefit under 35 U.S.C. §119(e) to Provisional Patent Application No. 61/909,814 filed Nov. 27, 2013, and Provisional Patent Application No. 61/921,295 filed Dec. 27, 2013 the entire contents of which are incorporated herein by reference. 
    
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND 
     Refuse collection vehicles can pick up and empty refuse containers from the front of the vehicle or from the side. Loading from the front of the vehicle as in U.S. Pat. No. 6,071,058 requires sufficient access so the front of the large refuse vehicle can approach the refuse container and such access is not possible in narrow alleys. Also, front loading lifts the refuse container over the vehicle cab and operator posing inherent risks if the container or its contents fall onto the cab during operation. In contrast, side-loading refuse vehicles need only drive alongside a refuse container and the container is lifted over the side of the vehicle rather than over the cab so there are access and safety advantages. Unfortunately, a side loading refuse vehicle cannot always get as close to the refuse container for ease of pick-up compared to a front loading vehicles. Thus, side loading refuse vehicles usually have mechanisms to extend from the vehicle and engage the refuse container and that increases complexity. 
     Side loading mechanisms exist that use articulated arms as in EP1142803. But the articulation joints are subject to wear and impart lateral movement to the assembly holding the refuse container when the arm is in the extended position. 
     Current mechanisms for side loading refuse vehicles are illustrated by U.S. Pat. No. 5,702,225 to Ghibaudo, which has a lateral rail extending and retracting the bottom of an arm with a carriage reciprocating along the length of the arm to pick up and empty trash receptacles. A pair of opposing grippers is connected to the carriage and engages a full refuse container resting on the ground. The grippers and refuse container move with a carriage along the length of the arm to lift the container from ground level to the top of the vehicle&#39;s refuse compartment. The top of the single-piece arm is curved so the arm resembles an inverted J shape, referred to as a candy cane shape. As the carriage moves along the curved portion, which extends downward, the container is inverted so as to empty the contents into the refuse compartment at the same location on the vehicle. As the carriage moves to the opposing end of the arm by the ground, the empty container is set back on the ground where the grippers release it whereupon the arm is retracted against the vehicle. The top of the one-piece arm was pivotally mounted at the top so the entire arm rotates about that top pivot, with the tip pivot mounted to move vertically relative to the vehicle. 
     While this is an improvement on prior side loading refuse vehicles. The movement of the arm and carriage rely on a series of pulleys, gears and motors which too often wear, break, or for various other reasons become misaligned sufficiently to require repair. Further, the movement of the carriage, grippers and refuse container and parts around the curved end of the arm caused the container to undergo a rapid acceleration and rotation which comes to an abrupt stop when the carriage hits a stop and that jars the single-piece arm mechanism, contributing to wear, misalignment and breakage. There is thus a need for an improved side loader for refuse vehicles. 
     BRIEF SUMMARY 
     A side loader for a refuse vehicle is provided which as an arm having upper tracks along which a wheeled upper carriage may move in order to carry a conventional gripper and leveler assembly mounted to the upper carriage, along with a refuse container releasably held by the gripper. The arm has a lower and upper arm portion, with the lower arm portion being straight and the upper arm portion being curved and pivotally mounted to rotate about a generally horizontal axis that is perpendicular to the path of travel along the arm, with the upper tracks extending along both the upper and lower portions. 
     The lower arm is pivotally mounted at opposing ends, with the lower end of the lower arm pivotally mounted to a laterally extending rail that moves the lower end toward and away from the vehicle during use. The upper end of the lower arm is pivotally mounted to a support post mounted to the vehicle and constrained to move in a generally vertical direction so that as the lower end of the lower arm moves away from or toward the vehicle the upper end will rise or fall as needed to allow lateral, generally horizontal movement of the lower end. Telescoping posts are believed suitable for the vertical motion. The lower arm portion, the laterally extending rail and the vertical support posts on the vehicle form three sides of a triangle, with the generally vertical support posts allowing the vertical length of the triangle to change as the length of the laterally extending rail changes and as the included angles of the triangle change. Pivotally mounting the lower arm at the top and bottom and allowing vertical movement of the top pivot mount allows the lower end of the lower arm portion to remain generally horizontal as the arm moves extends from the vehicle, making it easier to position the grippers to grab and lift refuse containers, and making it easier to set the containers down on the ground at a desired location, after they are emptied. 
     The curved, upper arm preferably has two straight end segments joined by a curved middle section of 10-20 degrees arc, so the distal end of the curved portion still remains upwardly inclined when the lower arm is extended for pick-up, allowing the weight of the wheeled upper carriage, gripper and refuse container to urge them to roll back down the upper tracks toward the ground. The distal end of the upper arm has a motion limit stop and a sensor such that when the wheeled upper carriage reaches the distal end of the curved upper arm, the upper arm is rotated about a pivot axis to dump the contents of the refuse container held by the upper tracks of the upper arm portion. 
     Extendable hydraulic pistons are believed suitable for the dumping rotation and retraction of the pistons may return the carriage, gripper and (empty) refuse container to the original position with aligned upper tracks so the carriage and connected parts may roll toward the ground to deposit the refuse container and pick up another one. This construction and operation allows a controlled emptying of the refuse containers. Because the carriage and connected parts need not be driven against the end of the upper arm by gravity as occurs when the end of the track curves downward as in prior art candy-cane shaped-arms, the impact forces, wear and misalignment of parts is reduced. The need to control the speed of the carriage toward the end of the arm as in the prior art where the candy cane curved downward, is also reduced or eliminated. Moreover, the rotation of the upper arm portion carriage, grippers and refuse container in order to dump the full refuse container, and then rotate the upper arm portion to align it with the lower arm portion to reposition the empty container for return to the ground is believed to be faster than the prior art, allowing a faster cycle time. 
     The upper carriage and associated parts may be driven by various mechanisms, including endless chain drives with a sprocket and optional gearing of the motor and drive chain assembly. Preferably though, a hydraulic drive is used in which two hydraulic carriage pistons are mounted to a lower carriage so the carriage pistons extend in opposing directions along the length of the lower arm portion. The lower carriage moves on a lower track beneath the upper track and preferably separated therefrom by a divider, with the lower track extending most of the length of the lower arm portion. One carriage drive piston fastens to the vehicle or the upper end of the arm to move the lower carriage toward and away from that upper end of the arm. The other carriage drive piston moves a lower return roller mounted to a wheeled shaft in order to move that wheeled roller along the lower track toward and away from the bottom end of the lower arm. A flexible, elongated member such as a wire rope, belt or preferably a chain has a first end fastened to the vehicle or the upper end of the lower arm so it doesn&#39;t move and has the other end fastened to the upper carriage, preferably at its upper end. The chain passes the lower carriage, reverses direction at the lower return roller to pass on the other side of the lower carriage before passing over an upper return roller that is straddled by the opposing tracks of the upper, curved arm portion, and then extends along the upper side of the lower arm section to connect to the upper carriage. As the carriage chain drive pistons extend the effective length of the chain is shortened and the upper carriage, gripper and refuse container move from the ground to the dump position. The chain wraps around at least one sprocket connected to the carriage pistons so that extension and contraction of the pistons move the upper carriage, gripper and refuse container. As the chain drive pistons retract the effective length of the chain lengthens and the upper carriage and associated parts roll down the arms toward the ground for unloading and picking up the next refuse container. The hydraulic pistons extending in opposing directions cause the chain length to change more rapidly than even a geared rotary motor achieves and is believed to be much faster than prior art drives using electric motors. Further, the extension of the hydraulic drive pistons and the chain length may be selected to suit the specific needs and more accurately control the position of the upper carriage on the upper and lower arms. 
     In more detail, a side loader is provided for emptying refuse containers into a refuse collection vehicle. The side loader has an upper carriage that has wheels. A gripper mechanism has opposing grippers that are configured to open and close to release and engage a refuse container. The gripper mechanism is connected to and moves with the upper carriage. The side loader has a first arm with opposing, top and bottom ends. A pair of spaced apart upper tracks extends between the top and bottom ends of the arm. The upper tracks are configured to guide the wheels of the upper carriage as the carriage reciprocates along the upper tracks of the first arm. The first arm is pivotally connected to the vehicle at the top end of the first arm to rotate about a first arm pivot axis. The first arm is pivotally connected to a laterally extending rail so the bottom end of the first arm may move away from and toward the vehicle. The side loader has a second arm that in turn has opposing lower and upper or distal ends and also has a pair of spaced apart upper tracks extending therebetween. The second arm has a curved portion and is pivotally mounted to the vehicle to rotate about a second arm pivot axis between a first position and second position. In the first position the lower end of the second arm is adjacent the top end of the first arm and the upper tracks on the first and second arms are sufficiently aligned and close together so the upper carriage can roll onto the upper tracks of the second arm. In the second position the second arm has rotated about the second arm pivot axis enough to dump the contents of a refuse container held by the grippers during use of the side loader. 
     In further variations of this side loader, the second arm is preferably curved. In particular, the distal end of the second arm is preferably higher than the lower end of the second arm when the second arm is in the first position. The upper rail on the second arm may have a straight portion adjacent the lower end and at the distal end of the second arm, with a curved portion in between. The curved portion preferably subtends an arc that is not large enough to incline the distal end downward. The distal end of the second arm is higher than the lower end of the second arm when the second arm is in the first position. 
     Additionally, the side loader preferably has a three bar linkage rotating the second arm between the first and second positions. The first arm may pivot about a pair of side supports adjacent the upper end of the first arm and the second arm may be pivotally connected to those side supports—directly or indirectly through a side plate connected to each side supports. The side loader has drive means configured to reciprocate the upper carriage along the first and second arms. 
     The side loader advantageously has a divider extending between the opposing upper rails on the first arm and extending along a majority of a length of the first arm. The divider may connect to a lower side of the upper rails on the first arm and have a center portion between the upper rails that extends outward beyond that lower side of the upper rails. The divider may separate the upper carriage and a lower carriage and associated lower rails, described below. 
     The side loader preferably has a lower carriage having wheels and a pair of spaced apart, lower tracks extending a majority of the length of the first arm and located on a bottom side of the first arm. The lower tracks are configured to guide the wheels of the lower carriage as the carriage reciprocates along the lower tracks of the first arm. First and second extendable drive pistons are connected to the lower carriage and aligned to extend in opposing directions along the length of the first arm. The first drive piston has an extendable end that is connected to a positionable shaft configured to move along a second length of the lower tracks as the second piston extends and retracts. The second drive piston has an extendable end that is pivotably connected to the vehicle during use to reciprocate the carriage along a first length of the lower tracks as the first drive piston extends and retracts. The pistons cooperate with an elongated drive member to move the first and second carriages. 
     A flexible, elongated drive member has a first end connected to the upper carriage and a second end connected to the vehicle, directly or indirectly as being connected to the side supports or the side plates that are connected to the side supports. The elongated drive member passes over at least a first rotating part at the top end of the second arm which reverses the direction of the elongated drive member a second return rotating part on the positionable shaft to also reverse the direction of the elongated drive member so that extension and retraction of the first and second chain drive pistons a total distance X causes the second return rotating part to move a total distance X and the upper carriage to move a distance greater than X. 
     The first and second drive pistons preferably comprise hydraulic pistons. The positionable shaft may comprise a shaft having wheels configured to reciprocate along the lower tracks, with the first length extends along a top portion of the first arm and the second length extends along a bottom portion of the first arm. The elongated drive member preferably comprises a chain. 
     The drive mechanism is preferably located on the opposite side of the outwardly extending portion of the divider as is the first carriage. In this arrangement the first and second extendable drive pistons are connected to the lower carriage and aligned to extend in opposing directions along the length of the first arm, with the second drive piston having an extendable end that is connected to a positionable shaft having wheels configured to move along a second length of the lower tracks as the second piston extends and retracts. The first drive piston has an extendable end that is pivotably connected to the vehicle during use to reciprocate the carriage along a first length of the lower tracks as the first drive piston extends and retracts and a portion of the drive pistons are located within a bottom side of the outwardly extending portion of the divider. In this arrangement the elongated drive member has a first end connected to the upper carriage and a second end connected to the vehicle with the elongated drive member passing over a first rotating part at the top end of the first arm and a return rotating part on the second arm which reverses the direction of the elongated member. The elongated drive member passes over a second return rotating part on the positionable shaft which again reverses the direction of the elongated member and so that extension and retraction of the first and second chain drive pistons to move the lower carriage a distance X causes the upper carriage to move a distance greater than X. 
     There is also advantageously provided a mechanism for moving a gripper mechanism reciprocating along an arm connected to a refuse collection vehicle. The gripper mechanism has arms configured to releasably grip a refuse container. The arm has a lower end extending toward and away from the vehicle during use. An upper end of the arm is sufficiently above a portion of the vehicle to allow the refuse container to be dumped into the vehicle. The mechanism for moving the gripper includes a first gripper carriage to which the gripper mechanism is connected. The first carriage is configured to reciprocate along a length of the arm sufficient to enable the gripper to pick up, dump and set down refuse containers. A second piston carriage is mounted to reciprocate along a length of the arm with the second, piston carriage having first and second carriage pistons each aligned to extend along a length of the arm but in opposing directions. The first carriage piston has a distal end connected to a first rotating part mounted to move along a length of the arm while the second carriage piston has a distal end connected to the vehicle at a fixed location. The flexible, elongated drive member has a first end connected to the first gripper carriage and a second end connected to the vehicle at a fixed location with the chain extending from the first gripper carriage, over a second rotating part at the upper end of the arm where the chain reverses directions and extends past the piston carriage and around the first movable part where the chain reverses direction and extends past the piston carriage to the second end of the elongated drive member, such that a change in length of one carriage piston a distance X moves the first gripper carriage a distance X and a change in length of both carriage pistons a distance X moves the first gripper carriage a distance 2X. The first and second carriages are preferably located entirely on opposing sides of the arm. And move along the arm in opposing directions. The arm may have an upper and lower segment with the upper segment rotatablely mounted to rotate about a generally horizontal axis to rotate the first gripper carriage to a dump position. 
     There is also provided a method for moving a gripper mechanism along an arm connected to a refuse collection vehicle where the gripper mechanism has arms configured to releasably grip a refuse container. The arm has a lower end extending toward and away from the vehicle during use and has an upper end sufficiently above a portion of the vehicle to allow the refuse container to be dumped into the vehicle. The method comprising the steps of moving a first carriage to which a gripper is mounted, along the arm in a first direction and moving a second carriage along the arm in a second direction opposite to the first direction using first and second extendable pistons. The first piston has one end connected to the vehicle to move the second carriage along the arm as the first piston extends and retracts. The second piston is connected to a first rotating part around which an elongated flexible member extends to reverse the direction of the flexible member and to also change the distance between the first rotating part and the second carriage as the second carriage piston extends and retracts. The elongated member extends around a second rotating part to reverse the direction of the elongated member before that elongated member connects to the first carriage with the elongated member having a second end connected to the vehicle. Thus, extending the pistons moves the lower carriage a distance X and moves the upper carriage a distance greater than X and preferably a distance 2X. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the invention will become more apparent in light of the following discussion and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  side plan view of a refuse truck having a side loader with a curved, upper end and a gripper in a stowed configuration; 
         FIG. 2  is a side view of a portion of the vehicle and side loader of  FIG. 1 , in an extended position with the gripper engaging a refuse container on the ground; 
         FIG. 3  is another side view of the side loader of  FIG. 2  with the gripper and refuse container being emptied into the vehicle and with extendable dump pistons being shown in an extended position; 
         FIG. 4  is another side view of the side loader of  FIG. 2  showing several parts in broken lines and in a stowed configuration as in  FIG. 1  and an arm in an intermediate rotated position; 
         FIG. 5 a    is a partial side view of a portion of a side loader with an upper arm in a first position; 
         FIG. 5 b    is a partial side view of a portion of the side loader with the upper arm in a second, emptying position; 
         FIG. 6  is a partial side view with the parts of  FIGS. 5 a  and 5 b    overlaid; 
         FIG. 7  is a partial perspective view of a side loader in an extended position with a carriage and gripper midway along the length of a lower portion of the side loader; 
         FIG. 8  as a partial perspective view of a side loader with the carriage approaching the beginning of the upper, curved portion of the side loader; 
         FIG. 9  is a partial perspective view of a portion of the carriage at the end of the curved, upper portion of the side loader with the carriage and curved portion of the side loader ready to be rotated into a second, dump position, looking from the vehicle outward; 
         FIG. 10 a    is a partial perspective view of a portion of the carriage and curved portion of the side loader in a second position; 
         FIG. 10 b    is partial perspective view of a portion of the carriage and curved portion of the side loader in a first position; 
         FIG. 11  is a partial plan view showing a portion of the carriage and the curved portion of the side loader; 
         FIG. 12  is a partial perspective view showing a bottom view of a lower portion of the side loader of  FIG. 2 ; 
         FIG. 13  is a schematic view of a chain drive using two opposing hydraulic cylinders; and 
         FIG. 14  is a partial perspective view of the upper end of the first arm section looking from the vehicle outward, with the second arm portion removed. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-2 , a side loader  10  is mounted to the side of refuse collection vehicle  12  which has a long hollow body  14  into which refuse is compacted as is known in the art. The front end of the body  14  has an upwardly opening hopper section  15  into which a refuse container is dumped. A cab  18  is at the front of the vehicle for steerage of the vehicle and operative control of the side loader  10 , although additional or redundant controls may be placed on the side of the vehicle  12  adjacent the side loader. As used herein the relative terms above, below, upper, lower, top, bottom refer to the relative directions or positions along a vertical axis perpendicular to the ground surface on which the vehicle  10  rests. The lateral direction refers to a direction more parallel to the ground and relative to the vehicle  10 . The relative directions front, back, forward and backward refer to the relative position or direction along longitudinal axis  21  of the vehicle  12  with front being toward the cab  18  and parallel to the ground and with back or rear being in the opposite direction. 
     Referring to  FIGS. 2-7 , the side loader  10  may be viewed as a lift arm  20  having two separable parts, a first, lower arm portion  22  that is preferably straight, and a second, upper, rotating portion  24  that is preferably curved or contains a curved part, that is rotatably mounted as described later, and that preferably has a distal end that is not extending downward a distance sufficient to cause the carriage to fall downward with gravity. The second, upper rotating portion  24  rotates between or from a first position aligned with the first, lower arm portion  22  to a second, dump position as described later. The upper end of first or lower arm portion  22  is rotatably mounted at pivot joints  28 , with a pivot joint  28   a ,  28   b  being located on each of respective side supports  26   a ,  26   b  which in turn are located adjacent the body of the vehicle  12  near the opening to the hopper  16 . The side supports  26   a ,  26   b  are preferably parallel to each other and more preferably take the form of sturdy plates sized or reinforced sufficiently to carry the loads to which they are subjected. The side plates  26  are preferably orthogonal to longitudinal axis  21 . The side supports  26  pivot about an axis through pivot joints  28  ( 28   a ,  28   b ). As described later this pivot axis preferably moves vertically to allow the lower end of the lower arm  20  to remain generally horizontal as the arm  20  extends away from and toward the vehicle  12 . 
     The lower end of the first arm portion  22  is pivotally supported along a rotational axis through pin and bracket assemblies forming a pivot joint  36  on the outer ends of each of two extendable horizontal support rails  30 . Only one of the pivot joints  36  is visible in  FIG. 2 . The outer support rails  30  slide in parallel relationship on rollers (not shown) journaled thereto inside of corresponding frame elements in the form of hollow box beams  32 . The box beams  32  are welded to the underside of the hopper section  16  and are connected to a pair of longitudinal frame members  34  of the refuse collection vehicle  12 . As needed, bumpers or shock absorbing materials may be interposed between the box beams  32  and the fame members  34 . The frames  34  extend forward and rearward along the body of the vehicle  12  while the box beams  34  extend transversely or laterally beneath the hopper section  16  so the outer support rails  30  extend from and retract into the side of the vehicle body  14  of the refuse collection vehicle  12 . Each box beam  32  receives a corresponding one of the outer support rails  32  in telescoping fashion. Thus, the first arm portion  22  is pivotally mounted at its upper and lower ends so the upper end rotates about the axis defined by pivots  28  while the lower end moves laterally toward and away from the vehicle body  14  as the support rails  30  extend or retract, and rotates about the axis defined by lower pivots  36 . The axes of rotation defined by pivots  28 ,  36  are generally horizontal in the depicted embodiment, and parallel to longitudinal axis  21 . 
     A lateral extension hydraulic piston  38  ( FIGS. 7 &amp; 12 ) has a first end mounted to the vehicle  12  and its distal end connected to the extendable support rails  30  so that extension and retraction of the lateral extension piston  38  extends and retracts the support rails  30 . The connection with the lateral extension piston  38  is a rotating connection. 
     A pair of hydraulically actuated opposing grippers  40  is provided for engaging and holding a refuse container  42  having an optional lid  41 , shown in  FIG. 2  as a frusto-conical shaped trash container  42 . Only one of the grippers  40  is visible in  FIG. 2 . Each gripper  40  extends from a base  43  which is pivotally mounted to an upper carriage  50  so the base and thus the grippers rotate about an axis parallel to longitudinal axis  21  in order to position the grippers parallel to the ground to pick up refuse containers  42 . Also, the base of each gripper  40  is pivotally mounted to the base  43  so as to rotate about an axis that is vertical in  FIG. 2  but which will actually vary if the base  43  rotates to tilt the grippers  40  relative to the ground. A hydraulic gripper piston  44  ( FIG. 1 ) has a distal end connected along a length of the gripper  40 , with the base of the piston connected to upper carriage  50  ( FIG. 1 ) where the grippers are pivotally mounted, so that extending and retracting the gripper piston  44  closes and opens the grippers  40  to grab and release containers  42 . A separate gripper piston  44  is provided for each gripper. Such grippers and their actuating mechanisms are known in the art. A hydraulic actuated, gripper leveling piston  46  has a base end pivotally mounted to upper carriage  50  at pivot  48  ( FIG. 7 ) and an opposing end connected at pivot  49  ( FIG. 4 ) on the base  43  of the grippers  40  so as to orientate the grippers relative to the ground and to the upper carriage  50 . Preferably two leveling pistons  46  are used as seen in  FIG. 7 . The leveling pistons  46  are in fluid communication with the pistons actuating the lateral support rails  30  so that if the later support rails  30  retract or extend as the upper carriage  50  is traversing the lower arm portion  22 , the leveling cylinders  46  maintain the refuse container  42  in an sufficiently upright position to avoid dumping the contents prematurely. Likewise, the control of hydraulic cylinders moving the lateral rails  30  and the leveling cylinders  46  is such that the orientation of the refuse container  42  is in a desire orientation as the upper arm portion  24  rotates to the dump position. The leveling pistons  46  and mechanisms for operating grippers  40  are known in the art as are control mechanisms for actuating the grippers  40  and maintaining the grippers  40  at desired orientations, and these aspects not described in detail. Likewise the connection of the grippers  40  to the carriage  50  is known in the art and is not described in detail herein. 
     The upper carriage  50  reciprocates along the length of the lift arms  22 ,  24  to move the grippers  40  and refuse container  42  toward the hopper  16 . The outer support rails extend a controlled distance to position the grippers  40  on opposing sides of the container  43 , with the gripper leveling piston  46  adjusting the position of the grippers  40  relative to the ground and to the container  42  to enable gripping the container  42 . The grippers  40  and gripper pistons provide a refuse container gripping mechanism. The grippers  40  are raised and lowered relative to the carriage assembly  50  by the leveling cylinders  46 , all of which reciprocate with the upper carriage  50 . During extension and retraction of the lift arm  22 , the leveling cylinders  46  are automatically actuated to maintain the grippers  40  at a substantially level attitude. This level attitude of the grippers  40  is preferably maintained as the upper carriage  50  travels up and down the straight, first portion  22  of the lift arm  20 . This orientation ensures that the refuse container  42  will be maintained in a vertical orientation as it traverses the length of the lower arm portion  22  so that the container contents do not spill onto the sidewalk or road. 
     Referring to  FIGS. 1-12 , the first portion  22  of lift arm  20  comprises spaced apart, parallel, upper tracks  54  which may be connected by divider  56  which is preferably a sheet metal plate. The tracks  54  and divider  56  extend most or all of the length of the first arm portion  22 . The divider  56  and upper tracks  54  preferably defines an outwardly facing (or upwardly facing when extended) open channel for receiving and guiding upper carriage  50  and a flexible, elongated drive member  58 , such as a drive chain or belt which may be repeatedly flexed in opposite directions without undergoing fatigue damage. The divider  56  has a cross-sectional shape that resembles a hat shape preferably formed by two opposing flat sides inclined toward each other at an angle of about 45 degrees and joining a flat top, with the tracks  54  extending along the inclined sides opposite the flat top. The carriage  50  straddles that raised portion of the divider  56  and moves along it. The extending middle portion of this divider creates an enlarged space on the bottom side of the divider within which other parts may fit as described later. 
     The upper tracks  54  each have a generally C-shaped cross-section which opens toward the other upper track  54 , as best seen in  FIGS. 7-8 and 10 . Returning to  FIGS. 1-12  the upper tracks  54  form guide channels within which wheels  60  ( FIG. 13 ) are mounted to upper carriage  50  so the wheels roll along and within the upper tracks  54  so the carriage can move along upper track  54 . The wheels  60  are preferably on axels (not shown) mounted to upper carriage  50  and are confined between opposing ends of C-channel upper track  54  to confine the movement of carriage  50 . There are preferably four wheels  60  on the upper carriage  50 , two on each side. The flat top of the divider  56  is preferably located between the opposing ends of the C-shaped cross-section against which the wheels  60  abut to position the upper carriage  50 . The upper carriage  50  is generally rectangular having sides parallel to the sides of upper tracks  54 . A plurality of the wheels  60  with rotational axes parallel to longitudinal axis  21  are connected to the upper carriage  50  so the round surface of the wheel abuts the ends  62  of the C-shaped channel forming upper tracks  54 . A plurality of wheels are also preferably, but optionally connected to the carriage with their rotational axes orientated orthogonal to the longitudinal axis  21  so the rolling surface of the orthogonal orientated wheels abut the side of the channel or upper track  54  to restrain movement of the carriage parallel to the longitudinal axis. The wheels  60  on carriage allow the carriage to move freely along the upper track  54  which extend the length of the first arm portion  22  and the length of second arm portion  24 . Because the divider  56  extends outward between the opposing upper tracks  54 , the body of the carriage straddles this outward extending section so that most of the body of the carriage  50  is located above the rotational axis of the upper carriage wheels  60 . This has the effect of offsetting the connection with the grippers  40  further away from the rotational axes of the wheels  60  than in the prior art. 
     The upper carriage  50  and upper track  54  are on an outward side of the divider  56  facing away from the vehicle  12 . On the opposing, inner side of the divider  56  and preferably in the space formed by the inclined sides of the bottom are first and second chain drive pistons  62   a ,  62   b . The pistons  62   a ,  62   b  are mounted parallel to each other and extend in opposing directions, with each piston aligned to extend and retract along the length of and parallel to the first arm portion  22 . A pair of spaced apart and parallel lower tracks  64  extends the length of the first arm portion  22 , but on the opposing side of the divider  56  as the upper tracks  54 . The lower tracks  64  are preferably not spaced as far apart as the upper tracks  54  and may be located between the upper tracks  54  but on the opposing side of divider  56 . Advantageously the lower tracks  64  have a partially closed end at each end of the tracks  64  to form a motion limit stop to prevent a lower carriage (described later) from passing beyond the end of the tracks  64  and disconnecting from the lower tracks. 
     Referring further to  FIGS. 12-13 , the lower tracks  64  each have a C-shaped cross section which opens toward the other lower track  64 . A lower carriage  66  having wheels  68  ( FIG. 12 ) is mounted to move along the lower track  64 . A plurality of the wheels  68  with rotational axes parallel to longitudinal axis  21  are connected to the lower carriage  66  so the round, rolling surface of the wheel abuts the ends of the C-shaped channel forming lower tracks  64 . A plurality of wheels  68  are preferably, but optionally also connected to the carriage  66  with their rotational axes orientated orthogonal to the longitudinal axis  21  so the, round rolling surface of the orthogonal orientated wheels abut the side of the channel or lower track  64  to restrain movement of the lower carriage parallel to the longitudinal axis. The wheels  68  on carriage allow the lower carriage to move freely along the lower track  64  which extend most or all of the length of the first arm portion  22 . 
     Referring to  FIGS. 7-13  and especially  FIGS. 12-13 , first chain drive piston  62   a  has a distal end pivotally connected to a lower movable support  70  that can move along the length of the lower arm  22 . The first chain drive piston  62   a  is shown as connected to a shaft, extending between a pair of wheels  68  each of which is sized to fit within and rotate along one of the opposing, lower tracks  64 , between the opposing flanges forming the C-channel of the lower track  64 . A lower rotating part  72 , preferably a lower return roller  72  or sprocket is connected to the lower movable support  70  and may preferably freely rotate about that shaft  70 . As the piston  62   a  extends and retracts the movable shaft  70  and lower return roller  72  move toward and away from the bottom end of the first arm portion  22  and also move toward and away from the lower carriage  66 —depending on the extension of the first piston  62   a.    
     The second chain drive piston  62   b  has its distal end pivotally connected to a ground point, preferable to one or both of the side supports  26   a ,  26   b  and more preferably to a shaft extending between the side supports  26   a ,  26   b . Preferably an upper fixed support  74  such as a cross-bar or shaft extends between the opposing side supports  26   a ,  26   b  and the distal end of piston  62   b  connects to that upper support  74 . Alternatively, a cantilevered post can extend from one of the side supports  26  to connect to the distal end of the piston  62   b . The connection preferably allows rotation of the distal end of piston  62   b . As second piston  62   b  extends and retracts the lower carriage  66  is pushed away from or moved toward the upper fixed support  74  and support plates  26 . 
     Referring to  FIGS. 8-11 and 13 , connected to at least one of the side supports  26   a ,  26   b  are also various rotating parts, preferably upper guide roller  76  ( FIG. 10 ) and a pair of upper support roller  80   a ,  80   b  on the inside of the chain  58  with roller  80   a  above roller  80   b  and roller  80   a  located relative to guide roller  76  so the chain  58  is between them. An upper return roller  78  ( FIG. 8 ) is connected to the second arm  24  and allows the chain  58  to reverse direction. The upper guide roller  76  helps maintain the chain  58  in position to move the upper carriage  50 , helps guide the chain onto the second arm  24 , and helps maintain the chain on the roller  80   a  when the second arm rotates to a dump position as discussed later. Each of the rollers  76 ,  78 ,  80  are preferably mounted so they freely rotate about shafts, with rollers  76 ,  80   a ,  80   b  mounted to shafts extending between side supports  26   a ,  26   b , or cantilevered from one of them, or otherwise supported in position. The use of these rollers with the drive chain  58  to move the upper carriage  50  will be described later. 
     Referring to  FIG. 12 , there is shown a guide block  82  that helps maintain the position of the chain  58  passing below the divider  56 . The chain  58  may be a heavy lift chain, with a 15,000 pound rating being believed suitable, but the size may vary with the intended use. Because the chain  58  is heavy it will sag downward differing amounts depending on the tension in the chain and the distance between supports for the chain. Guide blocks  82  are made of a suitable, durable elastomer and allow the chain  58  to either pass over them and avoid rubbing against the metal parts of the divider  56  and sliding sideways off the various sprockets, or the guide block may have an opening through which the chain  58  passes as shown in  FIG. 12 , to maintain the position of the chain relative to the first arm portion  22 . The depicted guide block  82  has two rectangular blocks with a slot formed on one face of the block to accommodate the chain  58 , with the slots of two blocks being aligned to restrict movement of the chain except through the slot, thus, clamping the chain to the lower guide block  66  but along it to pass through the block. Such guiding and supporting surfaces may be provided as needed to keep the chain  58  on track. 
     Referring to  FIGS. 3-6, 8 and 10 , the second arm portion  24  is separable from and movable relative to the first arm portion  22 . The second arm portion  24  has the same cross-sectional shape as the first arm portion except it lacks the lower track  64  and shaped divider  56 . The second arm portion  24  thus has C-shaped upper tracks  54  located to provide a rolling surface along which carriage wheels  60  may smoothly travel. The upper arm portion  24  is shown with two short but straight end segments about 7 inches long, connected by a curved middle portion that subtends an arc of 20 degrees and a length of about 9 inches so the lower segment is aligned with the first arm portion and the upper, distal segment is angled about 20 degrees from the longitudinal axis of the first arm portion  22 , toward the hopper  16 . The sprocket or guide wheel  78  is advantageously mounted at the distal ends of the tracks  54  on the second arm member  24  as seen in  FIG. 8 . Some of the curved portion of the arm  24 , and some of the distal straight portion of the second arm portion  24  preferably extend beyond the side supports  26   a ,  26   b . To further strengthen the second arm portion  24 , a bottom support  92  ( FIG. 8 ) may join the lower sides of the cross member  90  and the distal end of second arm  24 . 
     The second arm portion  24  is pivotally mounted to each side support  26   a ,  26   b  by a short trunion or pivot assembly  28  the rotational axes of which is parallel to the longitudinal axis  21  and located slightly below the upper track  54  and adjacent the lower end of that track  54  on the upper arm portion  24 . The pivot assemblies  28  are on a common pivot axis that as noted, is preferably parallel to the longitudinal axes  21  as the arms  22 ,  24  extend in a plane perpendicular to that axis  21 . The second, upper arm portion  24  rotates in part about this common pivot axis to dump the container  42  as described in detail later. 
     The second arm portion  24  rotates between two positions. In the first position the upper tracks  54  of the first and second arm portions  22 ,  24  align and preferably abut along joint line  91  ( FIGS. 7, 8 ) so that the wheels  60  and upper carriage  50  can pass between the first and second arm portions  22 ,  24 . In the second position the upper tracks  54  of the arm portions  22 ,  24  are separated as the second, upper arm portion  24  rotates to dump the refuse container  42  when the carriage  50  is located in the second, upper arm portion. The rotation is achieved by a linkage mechanism described below. 
     Referring to  FIGS. 5 a , 5 b    and  6 , a three bar linkage mechanism on each side support  26   a ,  26   b  may be used to rotate the second arm portion  24  and the carriage  50  held in the upper track  54  of that second arm portion  24 . As the linkages are the same only one is described. The linkage mechanism includes the second arm portion  24  as the driven link that is connected to and rotates about pivot  96  that is in turn connected to one of the side supports  26 , which represents part of the ground link. The side support  26  advantageously does not rotate or move vertically during dumping so the pivot  96  remains stationary during dumping. The pivot  96  connects to the upper arm  24  adjacent the center of the curved part of upper arm  24 , and below the upper track  54 . The pivot point  96  is preferably located on a first end of a rotating link  94  that is welded or otherwise connected to the lower, straight leg of the upper arm portion  24 . A second pivot  97  is located on an opposing, second end of rotating link  94 . The pivots  96 ,  97  may comprise rotating pivot pin assemblies. The second pivot  97  is located adjacent the lower end of the upper arm portion  24 , adjacent the juncture  91  between the upper ends of the lower arm portion  22 . The pivot  97  connects to the extendable end of hydraulic dump piston  98 , which has its base rotatably connected to a shaft  102  ( FIGS. 9-10 ) extending from or between the lower portions of side supports  26   a ,  26   b , to form a pivot axis  100 . The longitudinal axis of the dump piston  98  is offset from and preferably offset below the pivot axis  96  when the upper arm portion  24  is in the first position, with the pivot connection  97  to the rotating linkage  94  and arm portion  24  being below pivot axis  96  when the upper arm  24  is in the first position, and above pivot axis  96  when the upper arm portion  24  is in the second, dump position. 
     As best seen in  FIGS. 5 a , 5 b    and  6 , when the hydraulic dump piston  98  is in the retracted position the upper and lower arm portions  24 ,  22  align and preferably abut along joint  91  ( FIG. 8 ) to form a continuous path along which the carriage  50  travels with the wheels  60  guided by upper tracks  54 . As the dump piston  98  extends it rotates the upper arm portion  24  about pivot  96 , with the piston  98  rotating about pivot  100  into the second, dump position. The extension of the dump piston  98  is sufficient to invert the refuse container  42 . Retraction of the dump piston  98  returns the upper arm portion  22  to its position adjacent the upper end of lower track portions  22  and juncture  91 , with the tracks  54  aligned so the carriage  50  and associated gripper  40  and refuse container  42  may return along the lower arm portion  22 . The three bar linkage is thus formed by the extendable dump piston  100 , the rotating link  94  (part of upper arm portion  24 ) and the side flange  26  which is the ground connecting the pivot axes  96  and  100 . 
     As the dump piston  98  extends it pushes upward on the lower end of the second arm portion  24  and causes the upper arm portion  24  to rotate about pivot  96 . The rotating linkage  94  offsets the pivot axes  96 ,  97  on what is the lower end of the upper arm  24  when the arm  24  is in the first position. In that first position, the carriage  50  and refuse container  42  are on the opposing end of the upper arm portion so the dump piston  98  prevents rotating of the upper arm  24  about the pivot  96 . As the dump piston  98  extends the weight of the upper carriage  50  and refuse container  42  help rotate the refuse container  42  and upper arm  24  to the second, dump position and when the upper arm rotates the weight helps rotation and helps to empty the contents of the refuse container  42 . The dump piston  98  thus rotates the second arm portion  24  about the pivot  96  in the path defined by the movable end (pivot  97 ) of linkage  94  which rotates about pivot  96 . The dump piston  98  thus moves the second, upper arm portion  24  into the second, dump position as it extends. As the piston  98  retracts it moves the second, upper arm portion  24  into the first position where the first and second arms  22 ,  24  preferably abut along joint  91 , with the track  54  on each arm being aligned so the carriage  50  may move along the tracks  54  to set the now empty container  42  on the ground. 
     As the second arm portion  24  rotates between the first and second positions the refuse container  54  rotates along with carriage  50 . The second position of the second arm portion  24  places the refuse container  42  in an inverted position to dump the contents into hopper  16 . Any lid  41  on the refuse container  42  falls open with gravity or forced by the weight of the contents moving downward with gravity. Because the pivot locations which rotate the second arm portion  24  are the same lateral distance from the longitudinal axis  21  of the vehicle  12 , the contents of the container are dumped in the same location in the hopper  16  for a highly repeatable emptying sequence. Advantageously, the leveling cylinder  46  of gripper  40  holds the container  42  at a dump angle of about 50° or more relative to a vertical axis during dumping. Preferably the configuration of the second, rotating arm portion  28  is such that the upper carriage  50  places the container  42  in the desired dump angle as the arm portion  28  rotates from the first position to the second, dump position—without having to alter the leveling cylinders  46  from the angle maintained as the container travels the length of the lower arm portion  22 . This dump angle and the location of the refuse container  42  in the hopper  16  are highly repeatable so the contents of the refuse container are consistently emptied at the same location in the hopper. The preferred location for emptying is centered on or at least intersecting the longitudinal axis of the vehicle  12 . 
     Referring to  FIGS. 2 and 13 , the drive chain  58  has a first end  57  fastened to upper carriage  50  located on the outer side of divider  56 . A clevis and pin connection is preferred for connecting first end  57  to the carriage  50 . The connection, best seen in  FIGS. 7 and 9 , allows the connection with the chain  58  to rotate relative to the upper carriage  50 , while the carriage  50  is constrained to move along the two opposing and parallel tracks  54  in the two arms  22 ,  24 . When the carriage  50  is in the lower position shown in  FIG. 2  to pick up a trash container  42 , the chain  58  runs along the outer surface of the divider  56  and across the top of the upper guide roller  76 , which is positioned so the chain  58  extends in a generally straight line along the divider  56 . After passing over the upper guide roller  76  the chain  58  extends around a majority of the upper return roller  78  so as to change directions and return back along its original path, but offset below that original path. After passing around the upper return roller  78  the chain  58  passes over the top of the upper support rollers  80   a ,  80   b  and then extends along and generally parallel to the divider  56  but on the lower side of that divider until the chain passes the lower carriage  66  and passes around the lower return roller  72 . The lower return roller  78  changes the direction of the chain again so it passes back toward and past the lower carriage  66  to connect to one of the side supports  26  or a shaft extending from or between the side supports. As seen in  FIG. 12 , preferably the chain  58  passes over the lower side of the lower carriage  66  and over the lower return roller  72  and returns along a path that is closer to the divider  56  to connect to the side support  26 . 
     The second end  59  ( FIG. 13 ) of the chain  58  is connected to the vehicle  12  directly or indirectly, and preferably indirectly by being connected to one of the upper end of the first arm  22 , or preferably by being connected to one of the side plates or side supports  26   a ,  26   b  which are in turn connected to the vertically extendable members  110  in vertical members  112  connected to the vehicle  12 . Advantageously the second end  59  of the chain  58  has a resilient, tension device such as a spring  132  as well as a length adjustment device such as a threaded shaft  126  cooperating to adjust the length of the chain and to tighten or loosen the chain  58  while maintaining tension resiliently, and with the spring also absorbing sudden changes in the force in the chain to help reduce sudden jerks as the chain moves. More preferably, the second end  59  of the chain  58  fastens to a support shaft extending between side plates  26   a ,  26   b  with the resilient, tension adjustment mechanism interposed between the end  59  and the location on the vehicle. The second end of the chain  58  thus preferably fastens at a fixed location to the vehicle, but preferably in a manner that allows the second end  59  to pivot about its axis as the angle of the chain  58  may change. 
     Referring to  FIGS. 13-14 , a U-shaped yoke or a pin and clevis joint is believed suitable for connecting the second end  59  of chain  58  to the resilient, tension adjustment device which in turn has a coil compression spring  132  with a central threaded shaft  126  passing through the center of the spring for length adjustment of the shaft  126  and chain  58 . A spring keeper plate is fastened between a pair of interior support plates  136   a ,  136  that are in turn mounted in fixed position relative to and preferably parallel to side supports or side plates  26   a ,  26   b . The spring keeper plate  130  extends across the axis along which chain  58  extends. The keeper plate  130  has a hole through which the threaded shaft  126  extends with the second end connector  59  and chain  58  on the lower side of the plate  130  and the major length of shaft  126  on the other side of the plate  130 . The threaded shaft  126  passes through the spring and nut  128  with the nut being advanced on the shaft  126  toward the keeper plate  130  to shorten the length of the shaft and chain  58  and to compress spring  132 . The nut  128  is moved away from keeper plate  130  to lengthen the chain  58 . Loosening or tightening the fastener  128  adjusts the compression of the spring  128  and adjusts the length of the flexible, elongated member  58 . The exact details of the connection are not as important as it is that the second end  59  be at a fixed location connected to the vehicle  12  and that the first end  57  be connected to the upper carriage  50 , with the chain passing over rotating parts  72 ,  78  to change direction twice, so that movement of the rotating part  78  causes the effective length of the chain to change and thus move the upper carriage  50 . 
     In operation, because the length of the chain  58  is a fixed, predetermined length, then as the lower return roller  72  moves a distance X along the length of the first arm portion  22 , the effective length of the chain  58  changes by a distance of 2X. Chain drive pistons  62   a ,  62   b  control the position of the lower return roller  72 . As the pistons  62  extend the distance between the upper support  74  and the lower return roller  72  increased a distance X, the effective length of the chain connected to upper carriage  50  is shortened by 2X and that causes that upper carriage to move by a distance 2X so that the upper carriage  50  and container  42  move toward the hopper  16  where the container can be emptied. Likewise, by shortening the distance between the lower return roller  72  and the upper support  74  by a distance X, the effective length of the chain is lengthened by 2X, causing the upper carriage to move by 2X in the opposite direction, namely to move away from hopper  16  and toward the bottom end of the first arm portion  22  to pick up or set down container  42 . Because both chain drive pistons  62   a ,  62   b  are connected to the lower carriage  66 , the lower carriage moves a distance X in order to cause the upper carriage  50  to move a distance 2X. By mounting both pistons  62   a ,  62   b  on a movable carriage  66  the effective change in the length of the chain  58  can be doubled, and the use of two shorter, sturdier pistons  62  provides for a more compact construction, more reliable construction, and more accurate positioning as compared to using a single piston with the same extension and retraction length. The extendable drive pistons  62   a ,  62   b  connected to the lower carriage  66  and cooperating with the elongated drive member or chain  58  comprise a drive means. The drive means includes rotating part  78  which reverses the direction of the flexible drive member  58 , and the movable and rotating part  72  which reverses the direction of the flexible drive member  58  and allows the rotating part  72  to move to change the effective length of the drive member. 
     Referring to  FIGS. 8-10 and 13 , as the carriage  50  approaches the upper arm  24  as shown in  FIG. 8 , the chain  58  passes over the upper guide roller  76  and then over and around the upper return roller  78  located on a cross member  90  extending between the distal ends of the upper arms  24 , after which the chain passes along the support sheet  92 , over upper support roller  80   a  (adjacent roller  78 ) and  80   b  and then returns inside cover  56  and the lower track  64 . When the second arm  24  rotates from the first to the second position, the chain  58  wraps around the upper support roller  80   a , with no chain wrapped around upper guide roller  76 . The divider  58  does not extend onto the second arm portion  24  and that second arm portion  24  is generally open in its central area so the chain  58  does not hit any divider as the second arm portion  24  rotates between positions. The location of the rollers  76 ,  78  is preferably at about the location of the center of the curved portion of the second arm portion  24 . For stability, the distal end of the second arm portion  24  is joined by cross member  90  and the lower portion may have a further stiffening sheet support  92  that preferably does not extend far enough toward the curved portion to hinder movement of the chain  58 . 
     Referring to  FIG. 9 , as seen from the opposing side and with the carriage  50  located at the end of the second, upper arm portion  24 , the chain  58  passes over upper return roller  78  connected to cross member  90  and returns over the upper roller  80   a  and between rollers  80   a  and  76  (not shown in  FIG. 9 ). In  FIG. 9 , the second arm  24  is in the first position just ready for rotation to the second position for dumping the contents of any container held by the grippers and moved with the upper carriage  56 . 
     Referring to  FIG. 10 , after the second upper arm  24  is rotated to the second, dump position by the extended piston arms  98 , the carriage  50  is rotated about pivot  96 . The chain  53  wraps around upper roller  80   a  with the upper carriage  50  shown to the left in  FIG. 10 . Thus, as the second, upper arm portion  24  rotates about pivot axis  96  ( FIGS. 5 a -5 b   ) the chain  58  wraps around the upper support roller  80   a , leaving upper guide roller  76  exposed and uncontacted by chain  58 . 
     After unloading the receptacle  42 , the second arm portion  24  is rotated back to its first position, whereupon the chain  58  is moved in the opposite direction to reverse the sequence and move the upper carriage  50  to the lower end of the first arm portion  22  to release the trash receptacle  42 . The upper carriage  50  is on wheels  60  guided by and contained within upper tracks  54  that preferably take the form of C-shaped channels. The spaced apart upper tracks  54  confine the upper carriage  50  and keep it from moving relative to the tracks  54  as the second arm portion  24  is rotated between the first and second positions. The pivots  96  and  97  are suitably constructed to provide a sturdy and stable support as the second arm portion  24 , upper carriage  50 , gripper  40  and refuse container  42  are rotated between the first and second positions. Moreover, as best seen in  FIGS. 2 and 5   a , during operation the distal end of the second arm portion  24  is slightly inclined in an upward direction during use. 
     One or more sensors  140  ( FIG. 14 ), preferably proximity sensors, may detect the upper carriage  50  or the chain  58  to determine when the upper carriage  50  is at the upper or distal end of the second arm portion  26  either ready for the refuse container to be dumped, or to determine when the upper carriage has been returned from the second, dump position. The sensor(s)  140  confirm the position of the upper carriage, gripper and refuse container before dumping them, and confirm the position after dumping, so the carriage is not caught part way onto or off of the second arm portion  26  during rotation. Various types of known sensors may be positioned to verify the location of the carriages and operation of the various parts, especially the grippers  40 . The sensors may be used to control the speed with which the carriages move. As these controls are known, they are not described in detail. 
     Also shown in  FIG. 14  is an optional resilient stop  142  located inward of the upper rail  54  adjacent the upper end of the rail  54  on the first arm portion  22 . Stop  142  may be used to abut a portion of the lower carriage  66  or items mounted on the carriage in order to resiliently limit the motion of the carriage. 
     When the second arm portion  24  is in the first position, the weight of the carriage  50 , gripper  40  and refuse container  42  provide a downward force which helps keep the chain  58  tight. Thus, as the length of the chain  58  is effectively lengthened by retracting hydraulic pistons  62   a ,  62   b , the weight on the carriage  50  helps move the upper carriage  50  toward the ground where the refuse container  42  may be released. When the upper carriage  50  is in the pick-up position adjacent the ground so the grippers  40  may grab a refuse container  42 , the hydraulic chain drive pistons  62   a ,  62   b  are retracted in order to increase the available length of chain  58  needed to move carriage  58  to the end of the first arm portion  22 . When the chain drive pistons  62   a ,  62   b  are retracted the lower carriage  66  approaches the upper end of the lower arm portion  22 . As the chain drive pistons  62   a ,  62   b  are extended they take up some of the length of the chain and effectively shorten it, causing the upper carriage to move toward the upper, second arm portion  22 . As the chain drive pistons  62   a ,  62   b  extend, the lower drive carriage  66  moves toward the bottom of the lower arm portion  22 , in the direction opposite to that of the upper carriage  50 , and at a slower rate of travel than the upper carriage  50  when both pistons  62  are being extended. Since the chain drive pistons  62   a ,  62   b  extend in opposing directions, the lower drive carriage  66  does not reach the bottom end of the lower arm portion  22 , but the lower return roller  72  approaches that lower end. To ensure that the lower roller and its traveling shaft and wheels  68  are not pushed out the end of the lower arm portion, the lower end of the lower tracks  64  is blocked with a motion stop. 
     One of the pistons  62  is connected to one or both of the side supports  26   a ,  26   b , as by rotatably connecting to a shaft extending between the side supports  26 , so as to position the lower carriage  66  relative to the side supports. The upper end of the first arm portion  22  is rotatably connected to those same side supports  26 . As both the pistons  62  and first arm portion  22  are connected to the same part the side supports act as a ground allowing the lower carriage to be moved along the length of the arm portion  22 . 
     The use of hydraulic pistons  62  to vary the effective length of the chain  58 , and the use of sprockets and rollers to provide a multiplying effect, thus allow the position of the upper carriage  50 , grippers  40  and refuse container  42  to be controlled and to be moved a distance sufficient to have the upper carriage traverse the length of at least the first arm portion  22 . While the described embodiment uses a chain drive as the preferred embodiment of the flexible, elongated drive member  58 , and uses rollers  72 ,  76 ,  78 ,  80   a ,  80   b  to maintain the chain on a predetermined pathway, other devices could be used, including chain drives with sprockets, chain drives with combinations of sprockets and rollers, or any type of suitably flexible elongated member, including belts, ropes, cords, wire ropes, etc., and including elastomeric, ribbed drive belts used with suitable combinations of shaped sprockets, rollers and/or pulleys. 
     Referring to  FIGS. 2-4 and 7 , the orientation of the side supports  26  relative to the vertical will change depending on the angle of the lower arm portion  22 , since the side supports  26  rotate about pivot axis  28 . While the second arm portion  24  is always the same lateral distance from the longitudinal axis  21  when emptying the contents of the container  42 , the arm portion  24  may be at a different vertical location. The side supports  26  are mounted to vertically extendable members  110  which are guided by and received in base tubes  112 , preferably having a similar shape to the extendable members  110 . A vertically extendable member  110  having a tubular configuration with a square cross sectional shape, telescopically sliding in a slightly larger base tube  112  with a slightly larger square cross-sectional shape are believed suitable. The vertically extendable members  110  allow the pivot points  28  to move up and down vertically, generally parallel to the side of the vehicle  12 . The vertical motion of the pivot points  28  is especially useful as the support rails  30  extend laterally as it allows the triangle formed by the rails  30 , lift arm  20  and extendable members to change shape as the arm  20  rotates about pivot points  28 . 
     As the first, lower arm  22  extends outward to pick up a refuse container  42 , upper end  24  of the arm rotates about pivots  28  and as the length of the lower arm  22  is fixed the lower end of the arm would normally travel a curved path. But the lower end of the lower arm  22  may be raised and lowered by telescoping the extendable support member  110  into the base  112  so as to allow the lower end of the first arm portion  22  to maintain a generally horizontal path rather than a curved path. As the first, lower arm  22  is retracted toward the vehicle  12  the second, upper end that is connected to pivot  28  may be raised by extending the support member  110  from the base  112  in order to allow the lower end of the first arm portion  22  to maintain a horizontal path. The second arm portion  24  moves with the lower arm portion  22  and support member  110 . A triangle is formed by the generally vertically oriented members  110 , the lower arm portion  20 , and the generally horizontal oriented support rails  30 ,  32 . The support arm  22  has a fixed length and extends between pivot  28  on vertically movable member  110  and pivot  36  on horizontally movable member  30 , such that as lateral extension piston  38  ( FIG. 12 ) moves the lower rails  30  laterally toward or away from the vehicle  12 , vertically extendable members  110  are forced to slide within their bases  112  to accommodate the movement need to keep from deforming the fixed length lower arm portion  22 . The ability to maintain a horizontal path by raising and lowering the pivot joint  28  connected to support member  110  allows the grippers  40  to be positioned more easily to pick up refuse containers  42 . 
     To help the parts fit together compactly, the two extendable members  110  extend along the outward facing sides of the side supports  26   a ,  26   b , which sides face opposing directions along axis  21 . Each side support  26   a ,  26   b  is connected to a different one of the extendable members  110  by a different cantilevered pivot  28  aligned along a common axis. One end of pivot  28  is affixed to the upper distal end of extendable member  110  and the other end connects to one of the side supports  26 . The pivot  28  is preferably located on an outward facing side of the side supports  26 , while the pivot  96  is located on an inward facing side of the side supports  26 . 
     The use of two opposing chain drive pistons  58  is believed to permit a faster travel of the carriage  50 , gripper  40  and refuse container  42  than previously available. Motion stops at the lower end of the lower arm portion  22  prevent the wheels  60  and carriage  50  from passing out the lower end of the lower arm  22 . A closed end is preferably provided on the distal end of the upper track  54  on the upper arm portion  24  at its distal, upper end. Advantageously a resilient stop member  116  ( FIG. 8 ), such as a coil spring, is fastened to that closed end and located to abut the wheels  60  or a portion of the carriage  50  as it approaches the distal end of the second or upper arm portion  24 . The cross member  90  provides a redundant stop member in addition to the closed end of the track  56 . 
     In the prior art, the chain drive pulled the carriage over the top, curved portion of the candy-cane shaped drive path which resulted in the chain pulling the carriage downward against the end of the track but also resulted in the weight of the carriage, gripper and refuse container urging the carriage downward against the end of the track. That configuration resulted in severe shock when the carriage was brought to a stop, leading to high breakage and wear on the parts associated with the carriage, gripper and track. Slowing the drive chain down toward the end could help a little but unfavorably increased the time to pick up and dump a refuse container. Moreover, the rapid acceleration around the 180 degree curved portion of the candy-cane shaped track still led to high accelerations at the end of the track and resulted in high impact forces. 
     In contrast, the present design has the carriage  50  pulled by the chain  58  along the arms  22 ,  24  that preferably, but optionally, does not move the carriage in a downward direction until after the carriage reaches the end of the upper arm portion  24  and the end of the upper track  54 . In short, the end of drive chain  58  is attached to what is the upper end of the carriage  50  when the upper arm  24  is in the first position and the chain drive pistons  62   a ,  62   b  increase the distance between rollers  72 ,  78  which shorten the effective length of the chain to pull the carriage against the distal end of second, upper arm  24  and stops and resilient member  116 . At that point, the dump piston  98  is actuated causing the second, upper track portion  24  to rotate about a pivot axis through pivots  96 , causing the carriage to rotate enough to dump the contents of the refuse container  42  into the hopper  16  of the vehicle  12 . Optionally, the leveling pistons  46  may be retracted as the second arm  24  is rotated to further invert the refuse container  42 . Retraction of the dump piston  98  places the first and second arm portions  22 ,  24  in alignment at juncture  91  and orientates the gripper  40  and refuse container  42  is more horizontal orientation. If the leveling pistons  46  were retracted as the second arm  24  was rotated then the leveling pistons  46  are returned to their initial position to place the grippers  40  generally horizontal or at a predetermined position for traveling along the length of the lower arm  22 . The hydraulic chain drive pistons  62   a ,  62   b  are then retracted, causing the distance between upper and lower return sprockets  72 ,  78  to decrease, causing the chain  58  to move in the opposing direction and thus moving the upper carriage  50  off of the second, upper arm  24  and onto the lower arm portion  22  and toward the ground where the grippers  40  release the refuse container  42 . 
     The second arm portion  24  does not re-curve over 180 degrees to extend in a downward direction as in the prior art candy-cane designs and instead ends at a slight upward elevation even when the lower arm  22  is extended to its maximum distance from the vehicle  12 . Because the effective combined length of the arms  22 ,  24  are shorter than the prior art candy-cane design, and because the curved end portion  24  is oriented so the upper track  54  on which the upper carriage  50  wheels  60  rest is preferably inclined “uphill” or less preferably level and is preferably not downwardly inclined when the arms  22 ,  24  abut each other at junction  91 . Also, because the curved portion  24  is shorter and does not extend downward to any great extent, the distance needed to move the carriage  50 , gripper  40  and refuse container  42  to the distal end of the upper arm portion  24  is shorter than in the prior art. Because the oppositely oriented, hydraulic chain drive pistons  62   a ,  62   b  can achieve faster travel than conventional chain driven motors, the travel time is shortened. Because the rotation of upper arm  24  which dumps the container  42  can be very fast the cycle time for picking up, dumping and returning a trash container  42  is further reduced. Because the upper arm  24  is not re-curved with a downward extending end when the carriage  50  is being moved onto that upper arm  24 , there is no need to adjust the speed of the carriage or chain  58  and thus the control system is simplified and the travel time of the carriage  50  is shortened compared to the prior art. Because the rotation of upper arm  24  occurs with the carriage  50  stationary relative to the arm portion  24  and upper track  54 , the impact forces on the upper arm and track are believed to be less severe than the prior art. Because the design avoids having to move the carriage  50 , gripper  40  and refuse container  42  along a large radius path at high speeds, and instead rotates those parts about a fixed pivot axis, the cycle time is shortened and the forces on the parts is reduced. 
     While the forces resulting from dumping by rotation about pivot  96  are believed less, the forces can still be substantial. Thus, reinforcements of the side supports  24  may be made where appropriate. Also, motion stops or motion dampers may be provided to reduce the impact of abutting parts as the second, upper arm  24  rotates to dump the contents of the trash receptacle  42 . Thus, as best seen in  FIGS. 7-9 and 11 , resilient stop member  118  on the upper arm portion  24  may abut and aligned stop member  120  ( FIG. 4 ) on the vehicle  12 . The depicted stop members  118 ,  120  comprise elongated blocks of elastomeric material on a metal support that are located to abut each other when the second arm  24  is in the second, dump position. Other configurations of resilient stop members  118  may be used and other materials may be used as well. 
     Referring to  FIGS. 7, 8 and 10 , a shield or guide  122  is located at the upper end of the first arm portion  22  and extends above the upper track  54 . The guide  122  has a flat sidewall and a curved flange that extends over the path traveled by the lower end of the second arm portion  24  as it rotates about pivot  96  near the abutting juncture  91 . The guide  122  is located slightly outside the path to be traveled by the end of the second arm portion  24  that is lower when abutting the track  54  at juncture  91  as the arm portion  24  approaches that juncture. The guide  122  helps ensure alignment of the arm portion  24  with the lower arm portion  22  and makes access to the juncture  91  more difficult in order to enhance safety. 
     The side loader  10  thus has a laterally extendable first arm  22  with an upper carriage  50  connected to a gripper  40  to releasably engage refuse containers  42 . The second (curved) arm  24  has a first position abutting the top end of the first arm  22  so the upper carriage  50  can reciprocate along the first and second arms,  22 ,  24 . The second arm  24  has a second, rotated position which dumps the refuse container  14  into the hopper  16  of vehicle  12 . A drive chain  58  connected to the upper carriage  50  passes over a return roller  72  which changes the direction of the chain before it is connected to the vehicle  12 , preferably connecting to the first arm  22  or a side support  26 . The lower carriage  66  reciprocates along the lower side of the first arm  22  and holds two oppositely directed, extendable pistons  62   a ,  62   b  (preferably hydraulic). One piston  62  moves the lower carriage  66  relative to the vehicle  12  and the other piston moves the return roller  72  to alter the effective chain length and move the upper carriage  50  faster than the lower carriage  66  while reciprocating the upper carriage  50  along the length of arms  22 ,  24  when the second arm  24  is in the first position. 
     Although these inventions have been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the inventions and obvious, modifications and equivalents thereof. In addition, while several variations of the inventions have been shown and described in detail, other modifications, which are within the scope of these inventions, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combination or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.