Patent Publication Number: US-10308485-B2

Title: Offshore platform lifting device

Description:
This Application is being filed as a Continuation-in-Part of U.S. patent application Ser. No. 16/047,257, filed Jul. 27, 2018, currently pending, which was based on Taiwan Application No. 106127478, filed Aug. 14, 2017. 
    
    
     FIELD OF THE INVENTION 
     Background of the Invention 
     For lifting operation at sea, there is a platform that can be used on the sea. After the platform is sailed to a certain position, it can be used for lifting operation at sea. In order to maintain stability during the lifting operation, especially to avoid vertical fluctuations caused by wind and waves on the platform, a positioning means is used for positioning the platform on the sea surface, which is conducive to the stability and safety of the lifting operation. 
     US Patent Publication No. RE29478 and U.S. Pat. No. 7,219,615 B2 disclose another platform for operations at sea. This platform belongs to a semi-submersible platform and has a lower pontoon below an upper deck. The lower pontoon can be filled with water to sink, and the center of gravity can be moved down toward the sea surface. The platform can be tightened by cables or steel cables to avoid vertical floating caused by wind and waves on the platform to maintain the stability of the platform. However, it has been found in practice that even if the center of gravity of the platform is moved down toward the sea surface and the platform is tightened by the cables or steel cable, the platform is still be vertically fluctuation due to wind and waves, which will inevitably lead to instability during operations at sea. 
     In addition, the existing platform for offshore lifting operations adopts a rotatable davit arm that can rotate 360 degrees. The davit arm is composed of a hook, a support column and a rotating mechanism. The hook hoists the heavy object in cooperation with the rotating mechanism to allow the heavy object to be lifted at sea. However, this type of davit arm only relies on a single support column to bear the load. For the support column to lift the load, it is necessary to increase its volume to strengthen the structure. For the rotating mechanism to bear a large load and to cooperate with the volume of the support column, it is necessary to have a large volume to support the support column. For the rotating mechanism to push the support column to rotate, the rotating mechanism has a complicated structure and needs a plurality of driving units to rotate the support column, so the overall cost of the davit arm is high and the cost of the offshore lifting operation is also increased. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide an offshore platform lifting device, which uses support legs filled with seawater to sink to the seabed and a lower pontoon filled with seawater to move down toward the sea surface, thereby positioning the offshore platform lifting device in an economical and stable manner. 
     Another object of the present invention is to provide an offshore platform lifting device, which provides third winches to wind/unwind third cables for two davit arms to move laterally along a curved rail, in cooperation with second winches to wind/unwind second cables for lifting and lowering a heavy object hanged by hooks of the davit arms. The offshore platform lifting device not only allows the davit arms to load and lift the heavy object but also reduces the total production cost effectively and the cost of offshore lifting through the simple design of the overall structure. 
     In order to achieve the above object, the present invention provides an offshore platform lifting device for lifting operations at sea after sailed to a certain position of a sea surface. The offshore platform lifting device comprises an upper deck, a plurality of upright columns, a rail seat, a base, two davit arms, two first winches, and two second winches. The upright columns are connected to the upper deck and supported on a seabed. The rail seat is disposed on the upper deck. The rail seat has a curved rail. Two ends of the curved rail are provided with retaining walls. The upper deck has a center position relative to the curved rail. The center position is provided with a fixed pulley mechanism. The base is disposed on the curved rail. The base has a pushing device disposed on the upper deck for driving the base to slide along the curved rail. The two davit arms each have a first end and a second end. The second ends of the two davit arms are pivotally connected to the base and arranged side by side. The first end is provided with a first pulley and a second pulley. The two first winches are disposed on the upper deck. The two first winches each have a first cable passing through the first pulley of a corresponding one of the two davit arms and connected to the fixed pulley mechanism. When the two first winches each wind and unwind the first cable, the two davit arms are pivoted up and down with the second end as an axis. Two second winches are disposed on the upper deck. The two second winches each have a second cable passing through the second pulley of a corresponding one of the two davit arms. A hook is disposed at a distal end of the second cable. 
     Preferably, the upper deck is connected to a lower pontoon through the upright columns. Each upright column is provided with a support leg that is longitudinally inserted through the upright column. The lower pontoon has a plurality of chambers therein. The chambers are configured to receive water therein so that the lower pontoon sinks downwardly when the water is introduced into the chambers or floats upwardly when the water is drained out. The support leg has a compartment. The compartment is configured to receive water therein so that the support leg sinks downwardly when the water is introduced into the compartment or floats upwardly when the water is drained out. Each upright column includes a leveling mechanism therein. When the support leg sinks to reach the seabed, the leveling mechanism in each upright column is combined with the support leg to support the support leg. The leveling mechanism drives the upper deck to move up or down along the support leg. 
     Preferably, each upright column is provided with a wave-dissipating channel. The wave-dissipating channel has through holes on a plurality of sides of the upright column. The through holes communicate with each other through a pipe in the upright column. When a wave meets the upright column, seawater flows in through one of through holes and flows out through the other through holes via the pipe to eliminate the force of the wave against the upright column. 
     Preferably, the leveling mechanism located in each upright column has a plurality of upper positioning cylinders disposed in an upper seat and a plurality of lower positioning cylinders disposed in a lower seat. The upper seat and the lower seat are connected by a plurality of jacking cylinders. Each of the upper positioning cylinders and the lower positioning cylinders has a positioning rod that is extendable and retractable horizontally. The support leg supported by the leveling mechanism has positioning holes for receiving the positioning rods of the upper positioning cylinders and the lower positioning cylinders. The positioning rods of the plurality of upper positioning cylinders or the positioning rods of the plurality of lower positioning cylinders are respectively extended into the positioning holes of the support leg. The lower seat is driven to be close to or away from the upper seat by the plurality of jacking cylinders for driving the upper deck to move up or down. 
     Preferably, the fixed pulley mechanism includes a positioning seat and a fixed pulley assembly pivotally connected to the positioning seat. The positioning seat has a rail below the fixed pulley assembly. A bottom of the fixed pulley assembly has a plurality of second rollers. The fixed pulley assembly slides along the rail via the second rollers. 
     Preferably, a hydraulic device is disposed on the positioning seat. The hydraulic device is configured to drive the fixed pulley assembly, so that the fixed pulley assembly is pivoted laterally along the rail with its pivotal joint as an axis. 
     Preferably, at least one bracket is disposed between the two davit arms. 
     Preferably, the base has a pivot portion exposed out of the curved rail. The second ends of the two davit arms are pivotally connected to the pivot portion and arranged side by side. 
     Preferably, the curved rail has a rectangular cross section. The curved rail has a top surface, a bottom surface, a front surface away from the center position, and a rear surface opposite to the front surface. An opening is defined at the junction of the front surface and the top surface. The pivot portion of the base is exposed out of the curved rail through the opening. Each of the bottom surface and the rear surface is provided with a plurality of first rollers. 
     Preferably, the bottom surface is inclined toward the rear surface. Each of the first rollers on the bottom surface has a conical shape that is gradually enlarged toward the rear surface. 
     Preferably, the pushing device is composed of two third winches disposed on the upper deck. The base is composed of two sliders respectively disposed on the two davit arms. Each of the two sliders is provided with a third pulley. Each of the two retaining walls is provided with a diverting pulley. The two third winches each have a third cable passing through the diverting pulley and connected to the third pulley. When the two third winches each wind and unwind the third cable, the two sliders slide along the curved rail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the present invention; 
         FIG. 2  is a partial planar view of the present invention, showing the upper deck, the lower pontoon and the upright columns; 
         FIG. 3  is a schematic view of the upright column having the leveling mechanism and the wave-dissipating channel of the present invention; 
         FIG. 4  is a cross-sectional view of the wave-dissipating channels in the square upright columns of the two lower pontoons of the present invention; 
         FIG. 5  is a partial structural view of the present invention, showing the three-dimensional structure above the upper deck; 
         FIG. 6  is a top schematic view of the present invention; 
         FIG. 7  is a structural view of the fixed pulley mechanism of the present invention; 
         FIG. 8  is a front view of  FIG. 5 ; 
         FIG. 9  is an enlarged view of circle D of  FIG. 5 ; 
         FIG. 10  is a sectional view of the base in the curved rail of the present invention; and 
         FIG. 11  is a schematic view of the present invention when in use, showing a heavy object hanged by the two davit arms. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides an offshore platform lifting device for lifting operations at sea after sailed to a certain position of a sea surface A. As shown in  FIG. 1 , the offshore platform lifting device mainly comprises an upper deck  1 , a plurality of upright columns  3 , a rail seat  6 , a base  7 , two davit arms  8 , two first winches  91 , and two second winches  92 . 
     As shown in  FIG. 2 , the upper deck  1  is connected to a lower pontoon  2  by the respective upright columns  3 . Each upright column  3  is provided with a support leg  4  that is longitudinally inserted through the upright column  3 . The lower pontoon  2  has a plurality of chambers  21  therein. The chambers  21  are configured to receive water therein so that the lower pontoon  2  can sink downwardly when the water is introduced into the chambers  21  or float upwardly when the water is drained out. The operator can adjust the overall center of gravity of the offshore platform lifting device by controlling water filling into or draining out of the chambers  21 . The support leg  4  has a compartment  41 . The compartment  41  is configured to receive water therein so that the support leg  4  can sink downwardly when the water is introduced into the compartment  41  or float upwardly when the water is drained out. The compartment  41 , in this embodiment, is located at the bottom of the support leg  4 . 
     As shown in  FIG. 3 , each upright column  3  includes a leveling mechanism  5  therein. When the support leg  4  sinks to reach the seabed B, the leveling mechanism  5  in each upright column  3  is combined with the support leg  4  to support the support leg  4 . The leveling mechanism  5  can drive the upper deck  1  to move up or down along the support leg  4 . In this embodiment, the leveling mechanism  5  in each upright column  3  has a plurality of upper positioning cylinders  51 . The upper positioning cylinders  51  are disposed in an upper seat  31 . The leveling mechanism  5  further has a plurality of lower positioning cylinders  52 . The lower positioning cylinders  52  are disposed in a lower seat  53 . The upper seat  31  and the lower seat  53  are connected by a plurality of jacking cylinders  54 . Each of the upper positioning cylinders  51  has a positioning rod  511  that can be extended and retracted horizontally. Each of the lower positioning cylinders  52  has a positioning rod  521  that can be extended and retracted horizontally. The support leg  4  supported by the leveling mechanism  5  has positioning holes  42 . The positioning holes  42  are configured to receive the positioning rods  511 ,  521 . Thereby, the positioning rods  511  of the plurality of upper positioning cylinders  51  or the positioning rods  521  the plurality of lower positioning cylinders  52  can be respectively extended into the positioning holes  42  of the support leg  4 . The lower seat  53  can be driven close to or away from the upper seat  31  by the plurality of jacking cylinders  54  to drive the upper deck  1  to move up or down. 
     As shown in  FIG. 4 , each upright column  3  is provided with a wave-dissipating channel  32  having through holes  321  on a plurality of sides of the upright column  3 . The plurality of through holes  321  communicate with each other through a pipe  322  in the upright column  3 . When the wave meet the upright column  3 , the seawater flows in through one of through holes  321  and flows out through the other through holes  321  via the pipe  322  to eliminate the force of the wave against the upright column  3 . As shown in  FIG. 4 , this embodiment has two lower pontoons  2 . Each lower pontoon  2  has two upright columns  3  arranged in tandem. 
     As shown in  FIGS. 5 to 9 , the rail seat  6  is disposed on the upper deck  1 . The rail seat  6  has a curved rail  61 . Two ends of the curved rail  61  are provided with retaining walls  62 . The upper deck  1  has a center position C relative to the curved rail  61 . The center position C is provided with a fixed pulley mechanism  64 . As shown in  FIG. 3 , in the embodiment, the fixed pulley mechanism  64  includes a positioning seat  641  and a fixed pulley assembly  642  pivotally connected to the positioning seat  641 . The positioning seat  641  has a rail  643  below the fixed pulley assembly  642 . The bottom of the fixed pulley assembly  642  has a plurality of second rollers  644 , so that the fixed pulley assembly  642  can slide along the rail  643  via the second rollers  644 . 
     A hydraulic device  645  is disposed on the positioning seat  641 . The hydraulic device  645  is configured to push the fixed pulley assembly  642 , so that the fixed pulley assembly  642  is pivoted laterally along the rail  643  with its pivotal joint as an axis, thereby allowing the fixed pulley assembly  642  to move more smoothly. 
     As shown in  FIG. 7  and  FIG. 8 , the base  7  is disposed on the curved rail  61 . The base  7  has a pushing device  71  disposed on the upper deck  1  for driving the base  7  to slide along the curved rail  61 . In this embodiment, the base  7  is composed of two sliders  72  that are spaced apart from each other. The two sliders  72  each have a pivot portion  721  exposed out of the curved rail  61 . 
     The pushing device  71  is composed of two third winches  711 . The two third winches  711  are disposed on the upper deck  1  and correspond in position to the two retaining walls  62  of the curved rail  61 . The two sliders  72  define two outer sides  722  that are disposed away from each other. A third pulley  73  is disposed on each of the outer sides  722 . Each of the two retaining walls  62  is provided with a diverting pulley  74 . The two third winches  711  each have a third cable  712  passing through the diverting pulley  74  and connected to the third pulley  73 . The two third winches  711  each can wind and unwind the third cable  712  to slide the two sliders  72  along the curved rail  61 , thereby adjusting the lateral position of the two sliders  72 . 
     The two davit arms  8  each have a first end  81  and a second end  82 . The second ends  82  of the two davit arms  8  are pivotally connected to the pivot portions  721  of the two sliders  72  and are arranged side by side. The first end  81  is provided with a first pulley  84  and a second pulley  83 . In this embodiment, two brackets  86  are disposed between the two davit arms  8 , thereby enhancing the overall structure of the two davit arms  8  to bear the load. 
     The two first winches  91  are disposed on the upper deck  1  close to the center position C. The two first winches  91  each have a first cable  911  passing through the first pulley  84  of a corresponding one of the two davit arms  8  and connected to the fixed pulley assembly  642  of the fixed pulley mechanism  64 . When the two first winches  91  each wind and unwind the first cable  911 , the two davit arms  8  are pivoted up and down with the second end  82  as the axis, thereby adjusting the elevation angle of the two davit arms  8 . 
     The two second winches  92  are disposed on the upper deck  1  close to the center position C. The two second winches  92  each have a second cable  921  passing through the second pulley  83  of a corresponding one of the two davit arms  8 . A hook  85  for lifting an object is disposed at a distal end of the second cable  921 . 
     Preferably, as shown in  FIG. 10 , the curved rail  61  has a rectangular cross section, and has a top surface  611 , a bottom surface  612 , a front surface  613  away from the center position C, and a rear surface  614  opposite to the front surface  614 . An opening  615  is defined at the junction of the front surface  613  and the top surface  611 . The pivot portions  721  of the two sliders  72  are exposed out of the curved rail  61  through the opening  615 . Each of the bottom surface  612  and the rear surface  614  is provided with a plurality of first rollers  63 . The bottom surface  612  is inclined toward the rear surface  614 . Each of the first rollers  63  on the bottom surface  612  has a conical shape that is gradually enlarged toward the rear surface  614 , so that the angle θ between each of the first rollers  63  on the bottom surface  612  and the corresponding davit arm  8  is about 90 degrees, thereby increasing the maximum load of the two davit arms  8 . 
     In the actual use of the invention consisting of the above structures, the offshore platform lifting device provided by the present invention is sailed the working place on the sea surface A. The compartment  41  of each support leg  4  is filled with seawater, so the support leg  4  sinks to reach the seabed B to complete the fixing operation of the upper deck  1 . When the operator wants to lift a heavy object, the heavy object is lifted by the hooks  85  of the two davit arms  8  and then the second cables  921  are wound by the two second winches  92 , thereby lifting the heavy object. At the same time, the operator controls the lower pontoon  2  to drain the water in the chambers  21  adjacent to the two hooks  85  to maintain the center of gravity of the offshore platform lifting device (as shown in  FIG. 11 ). The two third cables  712  are retracted by the two third winches  711 , so that the two third cables  712  respectively drive the two sliders  72  to move along the curved rail  61 . Through the two first cables  911  and the two second cables  921  respectively passing through the fixed pulley assembly  642 , the fixed pulley assembly  642  is synchronously moved along the rail  643  along with the two davit arms  8 , and the two davit arms  8  are laterally moved to a designated position. Then, the two second winches  92  unwind the second cables  921  to lower the heavy object vertically to the designated position to complete the lifting operation. 
     From the above description, the advantages of the present invention are described below. 
     1. The upright columns  3  are connected between the upper deck  1  and the lower pontoon  2 . The support leg  4  is inserted through the upright column  3 . After the support leg  4  is filled with water, it sinks to reach the seabed B. The leveling mechanism  5  disposed in the upright column  3  is combined with the support leg  4 . After the lower pontoon  2  is filled with water, the center of gravity is moved down toward the sea surface A, so that the support leg  4  is stably supported on the seabed B. The upper deck  1  is moved up or down to a horizontal position. When the support leg  4  is filled with the seawater and sinks to the seabed B, the buoyancy of the lower pontoon  2  is sufficient to support the entire weight including the upper deck  1  and the lower pontoon  2 , so that the upper deck  1  is maintained to be above the sea surface. When the aforementioned overall weight and the buoyancy of the lower pontoon  2  are balanced, the leveling mechanism  5 , with the aid of the buoyancy of the lower pontoon  2 , can easily elevate or lower the upper deck  1  with buoyancy along the support leg  4 . This is beneficial for the horizontal fine adjustment of the upper deck  1  to achieve the effect of stable positioning of the platform. Besides, the sinking of the lower pontoon  2  and the support leg  4  is caused by injecting seawater, rather than a drive mechanism used for lifting, thereby saving cost and being economical. 
     2. The invention is different from the conventional offshore lifting platform which adopts a rotating mechanism to move and lift the heavy object. The invention adopts the two davit arms  8  to move the sliders along the curved rail  61  and the fixed pulley mechanism  64  located at the center position C, and cooperates with the driving of the first winches  91 , the second winches  92  and the third winches  711 . The invention not only allows the davit arms to load and lift the heavy object, but also moves the heavy object through the two davit arms  8  to perform horizontal and vertical pivoting movements to complete the lifting operation. In addition, through the simple design of the overall structure, the cost is reduced effectively further to reduce the cost of the offshore lifting operation greatly. 
     Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.