Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B66—HOISTING; LIFTING; HAULING
  • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
  • B66C13/00—Other constructional features or details
  • B66C13/04—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack
  • B66C13/08—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack for depositing loads in desired attitudes or positions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B66—HOISTING; LIFTING; HAULING
  • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
  • B66C13/00—Other constructional features or details
  • B66C13/04—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack
  • B66C13/10—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack for preventing cable slack

Definitions

• the present invention relates, in general, to a method of lifting a heavy item using a diagonal tension control unit and, more particularly, to a method of lifting a heavy item, which uses a diagonal tension control unit to control lifting loads of crane hooks when the heavy item is lifted using two crane hooks, thus allowing maximum lifting capacities of the crane hooks to be optimally utilized, and immediately responding to variations in weight and a center of gravity of the heavy item.
• Background Art
• a variety of land cranes and marine cranes have been used to lift heavy items in land and marine construction sites.
• the lifting load of the crane is determined by the weight and the center of gravity of the heavy item.
• the lifting capacity of a crane hook is determined according to the weight and the center of gravity of the heavy item, at a designing stage.
• the crane hooks are designed to have different lifting capacities, according to the lifting loads of the cranes.
• the crane hooks usually have the same lifting capacity.
• a required crane is selected, based on the maximum lifting capacity of the crane hook.
• the lifting capacity of the crane hook must have a large allowance so as to immediately respond to variations in the lifting load.
• the crane has a structure to lift the heavy item only in a vertical direction.
• an actual lifting load which is larger than the designed lifting load determined at the designing stage is applied to a crane hook which is closer to the center of gravity determined at the designing stage.
• another actual lifting load which is less than the designed lifting load of the designing stage is applied to a crane hook which is far away from the center of gravity of the heavy item determined at the designing stage.
• a crane hook having a larger lifting capacity must be used at a position which is closer to the center of gravity of the heavy item. Or, the weight of the heavy item must be reduced so as to lift the heavy item.
• a new crane hook having the larger lifting capacity must be prepared at a working stage, thus increasing the costs and complicating a manufacturing process of the crane. Thereby, it is undesirable to use the crane hook having the larger lifting capacity. Consequently, there has been proposed a method of reducing the weight of the heavy item. Disclosure of Invention Technical Problem
• an object of the present invention is to provide a method of lifting a heavy item without changing a capacity of a crane, which includes the step of coupling a predetermined portion of the heavy item close to a center of gravity of the heavy item determined at a designing stage, to a crane hook which is far away from the center of gravity, in a diagonal direction using both a tension control unit and a connection wire while controlling a tension of the connection wire by operating the tension control unit, thus controlling the lifting loads of the crane hooks as desired, and thereby allowing the maximum lifting capacities of the crane hooks to be optimally utilized, therefore increasing operational efficiency of the crane hooks, and immediately responding to variations in the weight and the center of gravity of the heavy item to be lifted.
• FIG. 1 is a schematic view to show a structure of lifting a heavy item using a conventional crane
• FIG. 2 is a schematic view to show a structure of lifting a heavy item using a diagonal tension control unit, according to the present invention.
• FIG. 3 is a graph to show a variation in operational efficiency of crane hooks as a function of the operation of the diagonal tension control unit of FIG. 2. Best Mode
• a heavy item 40 to be lifted by a crane is connected to first and second crane hooks 21 and 22, via main wires 30.
• the crane is provided with a diagonal tension control unit 60.
• the tension control unit 60 is coupled to both a predetermined portion of the heavy item 40 which is close to a center of gravity of the heavy item 40 determined at a designing stage and the second crane hook 22 which is far away from the center of gravity, in a diagonal direction.
• the tension control unit 60 is operated to control the tension of a connection wire 30 which will be described later herein, thus enhancing the operation efficiency of the first and second crane hooks 21 and 22.
• a hydraulic jack or an electric motor may be used as the tension control unit 60.
• the tension control unit 60 and the connection wire 30 are diagonally coupled to both the predetermined portion of the heavy item 40 which is close to the center of gravity of the heavy item 40 determined at the designing stage and the second crane hook 22 which is far away from the center of gravity.
• the connection wire 30 is tensioned by the tension control unit 60, the length of the connection wire 30 is reduced, thus controlling the lifting loads of the first and second crane hooks 21 and 22.
• FIG. 1 shows the heavy item 40 lifted by a conventional crane which does not have the tension control unit 60. It is assumed that the weight of the heavy item 40 is W, a distance between the first and second hooks 21 and 22 is L, and an eccentricity is e. Then, lifting loads Ha and Hb imposed on the first and second crane hooks 21 and 22 are represented by the following Equation 1.
• the lifting capacities of the first and second crane hooks 21 and 22 are determined by the lifting loads Ha and Hb which are calculated according to the Equation [1].
• the actual weight and the actual center of gravity of the heavy item 40 may be different from the weight and center of gravity which are determined at the designing stage.
• the lifting loads imposed on the first and second crane hooks 21 and 22 are represented by the following Equation [2].
• FIG. 3 shows a relation between the operational efficiency of the first and second crane hooks 21 and 22 and the operation of the tension control unit 60.
• H a ⁇ W a Y - D si ⁇ t ⁇ + W Dsin ⁇ " " 2 L
• the weight Wa' and the eccentricity e' are constants, and the tension D is a variable.
• the lifting loads Ha and Hb imposed on the first and second crane hooks 21 and 22 can be controlled by controlling the tension D.
• Such an operation allows the first and second crane hooks 21 and 22 to bear the lifting loads which are determined at the designing stage, thus allowing the maximum capacity of the crane to be utilized, and immediately responding to the variations in the center of gravity of the heavy item 40.
• the maximum lifting loads of the first and second carne hooks 21 and 22 at the actual working stage are represented by the Equation ?2?.
• the weight W of the heavy item 40 and the maximum lifting loads of the first and second crane hooks 21 and 22 maintain the designed values without being changed. That is, the weight W of the heavy item is 1500ton, and the maximum lifting loads of the first and second crane hooks 21 and 22 are 900ton and 600ton, respectively.
• the actual maximum lifting loads imposed on the first and second crane hooks 21 and 22 are calculated as follows by the Equation [2].
• the designed maximum lifting load of the first crane hook 21 is 900ton, but the actual maximum lifting load of the first crane hook 21 is lOOOton.
• the first crane hook 21 is not able to the heavy item 40.
• the actual maximum lifting loads imposed on the first and second carne hooks 21 and 22 at the actual working stage are represented by the Equation ?3?.
• the weight W of the heavy item is 1500ton
• the actual maximum lifting loads of the first and second crane hooks 21 and 22 are 900ton and 600ton, respectively
• the distance L between the first and second crane hooks 21 and 22 is 30m
• the distance a between the first crane hook 21 and the center of gravity of the heavy item is 10m
• the distance b between the second crane hook 22 and the center of gravity of the heavy item is 20m
• the eccentricity e is 5m
• the first and second crane hooks 21 and 22 can lift the heavy item 40 with the maximum lifting loads which are determined at the designing stage.
• Table 1 shows the variations in the lifting loads, the maximum lifting capacities, and the operational efficiency of the first and second crane hooks 21 and 22 according to a variation in the operation of the tension control unit 60.
• Table 1 shows the variations in the lifting loads, the maximum lifting capacities, and the operational efficiency of the first and second crane hooks 21 and 22 according to a variation in the operation of the tension control unit 60.
• the first crane hook 21 when the heavy item 40 is lifted through the conventional method which does not use the tension control unit 60, and the center of gravity of the heavy item 40 moves toward the first crane hook 21 by a distance of 2m, the first crane hook 21 must bear the lifting load of lOOOton. However, because the lifting capacity of the first crane hook 21 is 900ton, the first crane hook 21 is not able to lift the heavy item 40.
• the maxim lifting loads imposed on the first and second crane hooks 21 and 22 are 900ton and 500ton, respectively, so that the maximum lifting load imposed on the crane is 1400ton.
• the tension control unit 60 according to the present invention when used, the lifting loads to be borne by the first and second crane hooks 21 and 22 are controlled, thus allowing the crane to lift the heavy item of 1500ton. Therefore, the crane can be operated while the first and second crane hooks 21 and 22 having operational efficiency of 100%.
• the present invention provides a method of lifting a heavy item using two crane hooks, which uses a diagonal tension control unit, thus allowing the maximum lifting capacities of the crane hooks to be utilized, therefore reducing the costs which are required to lift the heavy items, and immediately responding to variations in the weight of the heavy item, and thereby minimizing the time required for construction.

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Citations (4)

• 2003
  • 2003-08-21 KR KR1020030058037A patent/KR20050020260A/ko not_active Application Discontinuation
• 2004
  • 2004-05-14 JP JP2006522501A patent/JP2007501177A/ja active Pending
  • 2004-05-14 WO PCT/KR2004/001134 patent/WO2005019087A1/en active Application Filing
  • 2004-05-14 CN CNB2004800230614A patent/CN100548858C/zh not_active Expired - Fee Related

Patent Citations (4)

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