Patent Publication Number: US-6981598-B1

Title: Turn-table dual hoisting crane

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Application No. 60/506,404 filed Sep. 26, 2003, entitled “TURN-TABLE DUAL HOISTING CRANE”, incorporated herein by reference. 

   STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. 

   The present invention relates to the transport of containers on a crane between land-based delivery and dockside sea vessel pick-up locations. 
   BACKGROUND OF THE INVENTION 
   Current facilities for transport of containers between land and ships involve large marine terminal cranes, which typically embody one trolley traveling along the length of a boom for pick-up and delivery of the containers. While such cranes may be adequate for low demand at small scale sea ports, at larger ports such cranes are a disrupting bottleneck to terminal activities, which call for additional equipment and cranes to avoid delays in port traffic and container transfer. It is therefore an important object of the present invention to provide for a more efficient and less time-consuming transfer of containers from trucks to ships through the aforementioned type of marine terminal crane. 
   SUMMARY OF THE INVENTION 
   Pursuant to the present invention, a single crane is provided through which repeated cycles of two simultaneously functioning trolleys may be moved along a fixed boom rail path and one of two 90° related rail paths on a turn-table platform pivotally mounted for rotation about an axis at the intersection of such platform rail paths so as to accommodate transfer of each trolley between the fixed boom rail path and either one of the two platform rail paths positioned in alignment therewith by angular displacement of the turn-table platform. One of the trolleys may thereby be cyclically emptied or loaded from one end of the boom while the other trolley is either loaded with a container or emptied at one of the two positions underlying the platform. 

   
     BRIEF DESCRIPTION OF DRAWING 
     A more complete appreciation of the invention and many of its attendant advantages will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein: 
       FIG. 1  is a side elevation view of a crane constructed in accordance with one embodiment of the present invention; 
       FIG. 2  is a top plan view of the crane illustrated in  FIG. 1 , with a cut-away section thereof exposing a turntable; 
       FIG. 3  is a section view taken substantially through a plane indicated by section line  3 — 3  in  FIG. 1 ; and; 
       FIGS. 4 ,  5  and  6  are section views taken substantially through planes indicated by lines  4 — 4 ,  5 — 5  and  6 — 6  in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
   Referring now to the drawing in detail,  FIGS. 1 and 2  illustrate a crane  10  adapted to be moved to a position for transfer of standard containers, such as a container  12  between pick-up and delivery locations such as a land-based pier  14  and dockside sea vessels  16 . The crane  10  has a support frame  18  embodying four vertical gantry legs  20  interconnected in spaced relation to each other so as to support on their upper ends a rectangular central structure  22  in a horizontal position. An elongated boom  24  extends horizontally from the central structural  22 . Opposite ends  26  and  28  of the boom  24  are spaced from the central structure  22  by different amounts. The boom end  26  is spaced a sufficient distance from the central structure  22  so as to accommodate container delivery thereat when the crane  10  is appropriately positioned by motorized wheel assemblies  30  at the lower ends of the crane gantry legs  20 . Support cables  32  attached to the top of an anchor  33  fixed to the central structure  22  maintains the boom  24  in its horizontal position by connection of the lower ends of the cables  32  to the boom  24  adjacent to its opposite ends  26  and  28 . 
   The container  12  and a spreader bar  48  are suspended below the boom  24  from one trolley  34  for travel along a path on the underside of the boom  24  between its end  26  and the central structure  22 . A second container  36  and spreader bar  48  are suspended below the central structure  22  from a second trolley  37  mounted below a turntable type of switching platform  40  as hereinafter explained. 
   As shown in  FIG. 3 , the platform  40  is pivotally mounted by a post  41  and central bearing  56  from the structure  22 , with the underside of the platform  40  exposed below the structure  22 . Two pairs of tracks  42  and  44  are formed on such underside of the platform  40  to establish a pair of trolley travel paths which may be alternatively aligned with a fixed travel path established along the underside of the boom  24  by fixed tracks  46 . The trolleys  34  and  37  are respectively suspended from the tracks  46  on the boom  24  and the tracks  42  or  44  on the platform  40  as shown in  FIGS. 3 ,  4  and  5 . The spreader bars  48  respectively connect the trolleys  34  and  37  to the containers  12  and  36 . When either one of the platform tracks  42  and  44  is aligned with the fixed boom tracks  46  as shown in  FIG. 3 , the trolley  34  or  37  with its spreader bar  48  may be switched between the boom tracks  46  and the platform tracks  42  or  44  so as to thereby transfer the container  12  or  36  between the underside travel paths on the boom  24  and the platform  40 , after which the platform  40  may be angularly displaced from the position shown in  FIGS. 2 and 3  toward another position at right angles thereto for realignment of the track  42  or  44  with the fixed boom track  46 . Such angular movement of the platform  40  in opposite directions accommodates cyclic transfer of both of the trolleys  34  and  37  between the boom  24  and the platform  40  as hereinafter explained. The turn-table platform  40  has a radially outer rim  52  guidingly supported by bearings  53  on an angular track  54  projecting downwardly from the bottom surface of the structure  22  as shown in  FIG. 6 . The turn-table platform  40  is centrally suspended from the post  41  projecting downwardly from the bottom surface of the structure  22 . The platform  40  rotates about a central pivot hole  43  guidingly supported by bearings  56  on post end  45 . 
   An operational cycle of the crane  10  may be initiated for loading of the sea vessel  16  when one of the two trolleys  34  and  37  with its spreader bar  48  suspended below the platform  40  is picking up the container  12  or  36  at the land-based pier  14  from a vehicle  50  as shown in  FIG. 1 , while the other trolley  34  or  37  is located adjacent the end  26  of the boom  24  for container drop off onto the dockside sea vessel  16  at the delivery location. The trolley  34  or  37  when emptied is then moved along the fixed boom tracks  46  back to the platform  40  for transfer onto the empty platform tracks  42  or  44 . The platform  40  is then rotated 90° under powered drive in a counter-clockwise direction for example from its position as shown in  FIG. 2  by motorized means to displace the emptied trolley  34  or  37  thereon out of alignment with the fixed boom tracks  46 , while the platform tracks  44  with the container laden trolley  34  or  37  is brought into alignment with the fixed boom tracks  46  to permit the trolley  34  or  37  to begin its journey toward the forward end  26  of the boom  24  for container delivery thereat. During such rotation of the platform  40  the container  12  or  36  is angularly displaced through its spreader  48  relative to the trolley  34  or  37  to avoid obstruction thereof by the crane legs  22  during trolley movement along the platform tracks  42  or  44 . The emptied trolley  34  or  37  on the platform  40  will then be positioned for container pick-up to complete one half of a cycle. The latter half-cycle process is repeated in a reverse direction to complete a full cycle with repositioning of the trolleys  34  and  37  on the crane  10  at the pick-up and delivery locations. Upon completion of each of such full cycles, the entire cycle may be repeated in order to accommodate container transfer between ships and piers by use of the single crane  10  with a significantly increased productivity. The foregoing described process may be reversed when desired with the pick-up location on the dockside sea vessel  16  while the land-based vehicle  50  is the delivery location, so as to unload the sea vessel  16 . 
   Obviously, other modifications and variations of the present invention may be possible in light of the foregoing teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.