Abstract:
A container variability system for use with a hook-lift hoist mounted onto a wheeled chassis and including at least one hydraulic cylinder for loading a container onto the chassis and for tilting said container to a raised off-loading position. The hydraulic cylinder is responsible for the horizontal movement of the container on the main frame of the hoist through a telescopic jib member. A tab mounted off of the longsill of the container actuates a switch that prevents further extension of the cylinder.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an improved hook-lift hoist that allows containers of variable length and, more specifically, containers that are shorter than the minimum specified length to be transported on a truck equipped with a single hook-lift hoist.  
         [0002]     The hoist has a pivotable L-shaped arm with a hook on its distal end portion that is used to engage a detachable truck box or container. The arm is pivoted to lift the container onto a wheeled chassis for transport of the container and its contents to any location. It has also become known that the hook-lift hoist is operable to tilt a loaded container to dump its contents rearwardly of the truck. Hook-lift hoists allow for a single truck chassis to be used with a wide variety of truck boxes, each of which has a distinct and advantageous use. A single truck chassis with a hook-lift hoist can be used, for example, to load, transport, and dump open-topped waste receptacles to a disposal site; to load, transport, and unload shipping containers; to mount, use, and dismount road maintenance equipment, such as a salt spreader; to load, transport, and unload wheeled equipment; and so on. This functional versatility makes hook-lift hoists an economical vehicle for transport industries, particularly the street and highway maintenance departments of municipalities, states, and other governmental entities where budgetary constraints and the variety of tasks that must be performed make these multi-purpose vehicles an attractive choice.  
         [0003]     The versatility of a conventional hook-lift hoist is restricted, however, by the minimum container length requirement. Typically, the minimum container length is determined by the shortest container that can be stowed at the forward most position on the hoist, while leaving an adequate amount of the container rearward of the hoist to ensure that the payload or contents of the container do not contact the back of the hoist or truck chassis when the container is raised into a dump position. Therefore, the conventional hook-lift hoist is usually delivered to operators with a minimum specified length requirement for containers to be transported. This minimum length requirement limits the overall range of container lengths and diminishes the usefulness and capabilities of the hook-lift hoist. The invention herein seeks to address this limitation by taking advantage of a telescopic jib boom design in a hook-lift hoist to accommodate containers shorter than the specified minimum length, thereby increasing the versatility of the hook-lift hoist.  
         [0004]     The use of containers of shorter than specified minimum length requires the operator to position the containers properly on the hook-lift hoist so that adequate container overhang behind the hoist is reserved for dumping of the payload. Improper loading of the container could result in damage of the back of the hoist or the truck chassis. Thus a mechanism is needed for proper container placement on the hoist. The present invention relates to such a mechanism incorporated into the hoist design to cause the container to stop at controlled positions.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention herein contemplates the use of a Container Variability System (CVS) consisting of a telescopic jib boom and a container position control mechanism on a hook-lift hoist to maximize the capabilities of hoists in handling containers of variable length. The telescopic jib boom moves a container forward and rearward laterally on the hoist by the extension or retraction of a hydraulic jib cylinder, respectively. CVS facilitates a hook-lift hoist operator to load containers shorter than the minimum specified length by automatically restricting the maximum forward placement of the container on the hoist. Allowance is made for enough forward placement of the container to engage hoist body locks, yet remain sufficiently rearward of the back of the hoist.  
         [0006]     Controlled placement of the container on the hoist is achieved in the preferred embodiment by providing for a bypass in the hydraulic oil required for extension of the hydraulic jib cylinder thereby causing the container to stop at a controlled location. A mechanically operated hydraulic valve is situated next to a lever with an eccentric cam. The lever rotates counter clockwise when it is struck by a tab of a forward moving container. A spool on the mechanical valve is then depressed by the eccentric cam, which actuates the valve. The actuated valve allows the hydraulic oil to flow back into a hydraulic tank and bypass the jib cylinder extension circuit, thereby preventing further extension of the hydraulic jib cylinder. These events cause the container to stop at the specific location along the hook-lift hoist. Similarly, a lever actuated limit switch can be used for a manually operated system. The switch, when struck, would signal an electric solenoid operated hydraulic valve to activate and dump the hydraulic oil back into the hydraulic tank.  
         [0007]     In an alternative embodiment, a lever actuated limit switch, when struck, could interrupt the circuit to the appropriate solenoid on the hydraulic control valve in an electric controlled hoist. In a hoist with pneumatic operated controls, a lever actuated pneumatic valve, when struck, could open and bleed off air supplied to the appropriate pneumatic shift kit on the jib extension circuit of the control valve. The controlled placement of containers, particularly those shorter than the minimum specified length, protects the rear end of the hoist or the truck chassis during dumping of the payload. CVS therefore increases the overall range of container lengths a hoist can carry and dump effectively.  
         [0008]     Accordingly, an object of the invention is to provide a telescopic jib boom that moves a container laterally along the hoist and is controllable by using a lever actuated switch.  
         [0009]     Another object of the invention is to provide a position control mechanism to place the container at a specified location on the hoist.  
         [0010]     A further object of the invention is to enable a hook-lift hoist to accommodate containers shorter than specified minimum length in a single truck chassis for effective transportation and dumping of the payload.  
         [0011]     These and other objects of the invention will be understood by a person skilled in the art upon a review of the specification, the associated drawings, and the appended claims. 
     
    
     BRIEF DESCRIPTION DRAWINGS  
       [0012]      FIG. 1  is a side view of a hook-lift hoist truck with a container variability system of the present invention.  
         [0013]      FIG. 2  is an enlarged, detailed side view of a position control system of the CVS showing a lever with eccentric cam in contact with a tab mounted off of container longsill. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     U.S. Pat. No. 5,601,393 which shows constructional features of a hook-lift hoist is herein incorporated by reference.  
         [0015]     Illustrated in  FIG. 1 , generally at  10 , is a container variability system of the present invention that is incorporated into a hook-lift hoist  12  mounted on a truck  14  having a chassis  13  and cab  16  supported on front wheels  18  and rear wheels  20 . The container variability system  10  allows carrying and dumping of shorter than minimum specified length containers  22  on the same hook-lift hoist  12  equipped truck chassis  13  used for containers that meet the minimum specified length requirement.  
         [0016]     Detailed showings of the hook-lift hoist  12  are illustrated in U.S. Pat. No. 5,601,393. The hoist  12  is made by Swaploader U.S.A., Ltd., Des Moines, Iowa and is sold under the trademark SWAPLOADER. Briefly, the hook-lift hoist  12  includes a mainframe  28  that is mounted to the chassis  13  by a plurality of mounting plates  36 . An articulated hook-lift arm  38  is mounted to the mainframe  28  for pivotal movement about a horizontal axis. The hook-lift arm  38  is pivoted by a pair of hydraulic cylinders that are supplied with pressurized hydraulic oil by a hydraulic fluid supply system. This pair of cylinders are primarily responsible for the lifting and loading of the container  22  onto the hoist. Continued horizontal, forward movement of the container  22  is achieved by the telescopic movement of a jib member through the extension of a jib hydraulic cylinder. Extension and retraction of this jib cylinder is also dependent on the supply of hydraulic oil by a hydraulic pump and valve station.  
         [0017]     The container variability system  10  includes a lever with an eccentric cam  26  that is mounted onto the side of the mainframe  28  of hoist  12  ( FIG. 2 ). The upwardly extending arm of lever  26  is held in place by an angled spring  30 . One end of the spring  30  is affixed to the lower portion of the lever arm  26  by pin  32   a,  and the other end of the spring  30  is suitably mounted onto the lower right hand side of the mainframe  28  by pin  32   b.  The extension of spring  30  allows counterclockwise pivotal movement of the lever  26 . A mechanical hydraulic valve  34  is situated in close proximity to the lever  26 . The spool of the mechanical hydraulic valve  34  is nested in a recess of the eccentric cam of lever  26  when spring  30  is in a relaxed state. The mechanical valve  34  interconnects with the pressurized hydraulic oil supply lines  50 , a line  52  leading to the jib extension circuit, and a line  54  leading to a hydraulic oil tank  56 . An L-shaped tab  58  is installed on the proper position of the longsill  60  of container  22 . When the tab  58  hits the lever  26 , the angled spring  30  extends and the lever  26  pivots counter clockwise. Consequently, the spool of the mechanical valve  34  rotates out of the groove of the eccentric cam of lever  26  and is compressed by the eccentric cam of lever  26 . The compressed spool of the mechanical valve  34  actuates the valve  34 , which allows pressurized hydraulic oil to dump into the hydraulic oil tank  56  and bypass the jib cylinder extension circuit. Continued extension of the jib cylinder  42  is thus halted due to lack of hydraulic oil supply. The forward movement of container  22  on the hoist  12  is in turn stopped at the point of contact between the tab  58  and lever  26 .  
         [0018]     The position of the tab  58  on the side of the container longsill determines the extent of the forward movement of container  22 . This tab  58  can be made of metal or other hard, resistant material such as polypropylene and is found on the side where the CVS is located. It is to be installed along a line that crosses the upper portion of the arm of lever  26  so that it could hit the lever when the forwardly moving container  22  reaches the intended stop point on the hoist  12 . For safe transport of the container  22  and later effective dumping of payload, the location of the tab  58  has to be such that enough allowance is made for forward placement of the container  22  to engage hoist body locks  62  ( FIG. 1 ), and yet there still remains sufficient container overhang past the rear of hoist  12 . The precise location of the tab  58  has to be determined based on each container&#39;s length. For container  22  that is equal to or longer than the minimum specified length, the tab  58  is positioned to allow the jib cylinder  42  to fully extend for maximum engagement of container  22  in hoist  12  through the hoist body locks  62 . For shorter than minimum specified length container  22 , care needs to be taken to position the tab  58  to accommodate enough container engagement in the hoist and sufficient container overhang past the rear of the hoist.  
         [0019]     A shorter than minimum specified length container  22  is raised and brought into contact with a pair of flanged rollers  66  which serve to decrease the force required to drag the container  22  onto the truck  14  and to keep it centered relative to the truck  14  ( FIG. 1 ). The above maneuver is accomplished through the retraction of the pair of hydraulic cylinders. Full retraction of the cylinders brings the container  22  into a transport position where the container  22  is supported on the mainframe  28 . Once the container  22  is placed horizontally on the hoist, it is slid forwardly through the telescopic movement of jib member, which is driven by the extension of jib cylinder. When the tab  58  ( FIG. 2 ) mounted off of the longsill of container  22  hits the lever  26 , the continued forward movement of the container is halted because the hydraulic oil bypasses the jib cylinder extension circuit, which prevents further extension of the jib cylinder and the telescopic movement of jib member. The container  22  is then secured onto the mainframe  28  by hoist body locks  62  for storage and transport. Because of the proper placement of short container  22  on the hoist  12 , dumping of payload from the container  22  does not damage the back portion of the hoist  12 .  
         [0020]     Although the invention has been described with respect to a preferred embodiment thereof, it is to be also understood that it is not to be so limited since changes and modifications can be made therein which are within the full intended scope of this invention as defined by the appended claims.