Abstract:
The instant invention is directed to a active-over-passive coordinated motion winch designed to be used in combination with a class of existing offshore lifting systems such as A-Frames, booms or cranes to minimize the relative movement between a payload position and a destination position occurring commonly in offshore operations. The configuration of this system allows a remote operated vehicle (ROV) or any other launched load to be firmly captured until it is delivered to the desired destination. The configuration of the system also permits towed loads, such as sonar devices, to closely maintain level tow paths along the sea floor.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to an active-over-passive coordinated motion winch; particularly to an active-over-passive coordinated motion winch suited for minimizing the relative movement between a payload position and a destination position occurring commonly in offshore operations.  
       BACKGROUND OF THE INVENTION  
       [0002]     One of the challenges in working on offshore operations is dealing with the constant motion due to the ocean&#39;s waves. The constant heaving and surging of the waves presents numerous challenges to those involved in the transfer of payloads from ships or platforms to positions on or below the ocean&#39;s surface.  
         [0003]     In a typical lowering situation, the payload is first lifted off the deck of a ship using a winch having a cable running through a sheave rotatably mounted on an A-frame or crane boom. The crane or A-frame luffs overboard and the winch cable is paid out to lower the load. Once the payload touches the peaks of the waves, the ocean&#39;s influence causes relative motion between the ocean&#39;s surface and the object being moved. The relative motion engendered between the ocean&#39;s surface and the object being moved must be taken into account and compensated for to accurately deliver the payload. Movement of towed loads that travel close to the ocean floor represent a risky endeavor for many reasons, one of which is that large relative degrees of motion are induced into the towed load due to the ship&#39;s response to movement of the water&#39;s surface. Docking or maneuvering an object suspended from a ship&#39;s crane or other lifting device near fixed objects, in the ocean or on the ocean floor, is nearly impossible unless special means are taken to reduce or eliminate the relative motions. Additionally, when the relative motions are in excess of the load&#39;s terminal velocity in the water, snap loads occur in the lowering cable. These snap loads are dangerous to the survival of the cable, its terminations, and to the load and lifting device in general. Since these relative motions increase with increasing seas, the range of weather in which these lowering operations can be carried out is restricted. Since larger ships induce smaller motions, larger ships are often required for critical lowering operations.  
         [0004]     Various heave compensation devices have been proposed in an effort to overcome these difficulties. These devices generally attempt to maintain the load in a more or less fixed position relative to the earth, regardless of the motions that the ship is undergoing by creating reciprocal movements in the lowering cable in an attempt to compensate for the relative motion. Control of these devices may be either passive or active, with relative expense, space and weight considerations being deciding factors in this regard. Various mechanisms have been utilized in attempting to raise and lower the required amount of cable to produce the reciprocal movements, including active winch drums, flying sheaves, and nodding booms.  
       PRIOR ART  
       [0005]     U.S. Pat. No. 4,593,885 discloses a motion compensating device which is installed on a lift line and situated between a crane and an object to be lifted. The device consists of a hydraulic system and sheave mechanical system arrangement together with a balancing system for a given load range.  
         [0006]     U.S. Pat. No. 4,354,608 discloses a motion compensating device for a crane hoist. A counterweight, connected to the reeving system, maintains a level of pretension upon the line. A hydraulic cylinder provides a cushioning effect at both ends of the counterweights travel and allows locking movement of the counterweight.  
         [0007]     U.S. Pat. No. 4,544,137 provides a motion-compensated lifting apparatus which provides a traveling weight for maintenance of tension upon the load-lifting member, and a locking mechanism for prevention of movement of the traveling weight in one direction. Load direction sensing devices prevent lifting when the vessel is falling.  
         [0008]     U.S. Pat. No. 4,632,622 provides an apparatus for transferring cargo including a pivotally connected linkage for connecting two locations so as to accommodate relative movement therebetween. Interaction of the linkage via the use of hydraulic cylinders articulates a compensating motion between the two locations.  
         [0009]     U.S. Pat. No. 5,685,683 teaches a system for unloading bulk material from a ship. A float is positioned in the water transverse from and intermediate the ship and a stationary land-fixed location. An outer intake end of a pivotal bulk conveyor on the float is supported and maintained at a fixed height above the body of water and adjacent the ship. An opposite inner outlet end of the pivotal bulk conveyor on the float is supported at a fixed height above the stationary location. As the material is moved, it is transferred to an intermediate bunker car which is moved synchronously longitudinally with the pivotal bulk conveyor and the bucket conveyor.  
         [0010]     U.S. Pat. No. 5,028,194 is drawn to a marine crane having an additional controllable variable lifting capability which is operably connected with the crane&#39;s load line and separately connected to the surface upon or from which an object is being lowered or lifted. The motion of the crane is compensated to provide for safe initial lifting of cargo from a supply vessel in response to wave action.  
         [0011]     U.S. Pat. No. 5,114,026 describes a hoisting device including a cable controlled conventional crane winch assembly which operates in conjunction with a traction winch assembly inclusive of a traction device and storage winch. The use of the crane winch and traction winch assembly, in concert, enables both critical and long haul travel of cargo.  
         [0012]     U.S. Pat. No. 5,511,922, teaches a cargo loading and unloading system. A transport car carrying weight enters the ship through a gunwale opening via a ramp. A lift table, which permits the car to board, is positioned by various raising and lowering mechanisms and sensors which operate under the direction of a controller mechanism. Ramp angle and horizontality are maintained within fixed limits irrespective of the relative displacement of the ship&#39;s hull with respect to the adjacent wharf, so as to maintain smooth operation of the transport car between the wharf and lift table.  
         [0013]     Although the specialized loading and unloading equipment listed above does have the ability to partially compensate for the wave motion, they also have a number of disadvantages. One disadvantage is the complexity and mass of many of these systems which limits their usefulness and the environments in which they can be utilized. A disadvantage of completely passive systems is they are only able to compensate for a portion of the relative motion incurred by most payloads. A disadvantage of completely active systems is they require enormous amounts of horsepower once there is a significant overboard load. Additionally, completely active systems attempting to predict a ship&#39;s motion have failed to compensate for conditions such as rogue waves. Loss of feedback with either type of these systems results in dangerous conditions for operators as there is no back-up system to compensate for snap loads.  
         [0014]     Accordingly, what is lacking in the art is an active-over-passive coordinated motion winch. The active-over-passive coordinated motion winch should include a primary passive heave compensation assembly and a secondary active heave compensation assembly. The passive assembly should cooperate with a control assembly to substantially carry the load and passively compensate for a large portion of motion due to the ocean&#39;s waves. The active assembly should cooperate with the passive assembly and actively compensate for at least a portion of the remaining wave motion.  
       SUMMARY OF THE INVENTION  
       [0015]     The instant invention is directed to an active-over-passive coordinated motion winch designed to be used in combination with a class of existing offshore lifting systems such as A-Frames, booms or cranes. The configuration of this new system allows a remote operated vehicle (ROV) or any other launched load to be firmly captured until it is delivered to the desired destination. The configuration of the system also permits towed loads, such as sonar devices, to closely maintain level tow paths along the sea floor. This greatly enhances data acquired from such towed instrument packages, especially when used for bottom mapping and/or search and discovery missions.  
         [0016]     The winch assembly includes a drum having a hub defining an axis of rotation and a pair of flanges at opposing ends of the hub and perpendicular to the axis of rotation. Mechanically linked to the drum is a control assembly, a passive heave compensator and an active heave compensator to provide selective rotation to the drum. The passive heave compensator assembly cooperates with the control assembly to substantially carry the weight of the payload and compensate for a substantial amount of the ocean&#39;s wave movement. The active heave compensation assembly is constructed and arranged to monitor various parameters within the winch assembly and the passive heave compensation assembly, process the feedback with a computer and apply rotational force or braking force to the winch drum for enhanced stabilization of the payload in all zones of ocean operation.  
         [0017]     There are five distinct zones of the ocean that each provides problems for ship operations that involve lowering payloads into the water. These same zones affect towed systems equally. They are as follows: 
    Zone I: SPLASH ZONE which is comprised of the distance from the crest of the wave down to the trough of the wave plus two times the height of the package.     Zone II: NEAR SURFACE which begins once the package is lowered below the trough of the waves. It&#39;s ending is somewhat vague but is typically approximately 200′ to 300′ in depth.     Zone III: WATER COLUMN is basically the water between the ending on Zone II and Zone IV.     Zone IV: NEAR BOTTOM is the last 50′ of water depth before landing the package on the sea floor.     Zone V: the deepest point, the last 15″ and landing on the sea floor.    
 
         [0023]     Offshore operations vary depending on what the requirements of that particular job are. They can involve operations at any or all of the zones listed above. It is important to remember that the package must pass through these zones on its way to and from the deepest point of the operations. Each zone offers its own set of distinct problems and motion compensation reduces most of the detrimental effects.  
         [0024]     By utilizing the aforementioned construction, the relative movement between the payload position and the destination position can be substantially neutralized, regardless of whether the payload is neutral (weightless in water), or negative (has weight in water) in all of the aforementioned zones of operation.  
         [0025]     In addition, because the active heave compensation assembly only needs to supplement the passive portion of the system, horsepower requirements are reduced allowing this portion of the system to be built much smaller and lighter than previous active systems. The aforementioned construction also provides increased safety when compared to prior art active systems. In the event the active heave compensation portion of the instant invention fails, the system reverts to a passive heave compensation system.  
         [0026]     Accordingly, it is a primary objective of the present invention to teach a coordinated motion compensating winch system for use in a marine environment to instantaneously position a load and thereby neutralize relative movement between a payload position and a destination position.  
         [0027]     Another objective of the instant invention is to teach a coordinated motion compensating winch system for use in a marine environment which utilizes a primary passive heave compensating assembly to substantially neutralize relative movement between a payload position and destination position.  
         [0028]     Yet another objective of the instant invention is to teach a coordinated motion compensating winch system for use in a marine environment having a secondary active heave compensating assembly to dynamically enhance the primary passive heave compensating assembly to substantially neutralize relative movement between a payload position and destination position.  
         [0029]     Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein set forth, by way of illustration and example, certain embodiments of this invention.  
         [0030]     The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objectives and features thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a block diagram illustrating the instant invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]     Although the invention will be described in terms of a specific embodiment, it will be readily apparent to those skilled in this art that various modifications, rearrangements and substitutions can be made without departing from the spirit of the invention. The scope of the invention is defined by the claims appended hereto.  
         [0033]     Referring to  FIG. 1 , a block diagram for an active over passive coordinated motion winch device of the instant invention is illustrated generally at  100 . The active over passive coordinated motion winch is particularly suited for use in a marine environment to position a payload and neutralize relative movement between a payload and a destination position. The instant invention winch generally includes a winch assembly  10 , a control assembly  20 , a passive heave compensation assembly  50  and an active heave compensation assembly  70 .  
         [0034]     The winch assembly  10  includes a drum  12 , said drum having a hub  14  defining an axis of rotation A and a pair of flanges  16  at opposing ends of said hub and perpendicular to said axis of rotation. The drum and flanges cooperate to facilitate storage, take up and pay out of one or a group of flexible elongate member(s) (not shown) in continuous evenly distributed coils as is well known in the art. Suitable flexible elongate members may include, but should not be limited to, wire rope cables, ROV umbilical cord, communications cable, combinations thereof and the like.  
         [0035]     The control assembly  20  is generally constructed and arranged to selectively and operatively engage the winch assembly  10  whereby variable torque and rotational speed or free rotation of said drum  12  is provided. A main hydraulic power unit  22  is fluidly connected via a primary supply tube  26  to supply pressurized liquid to a primary hydraulic motor  24 . The primary hydraulic motor is mechanically connected to the drum  12  by means well known in the art for providing selective power assisted rotational movement thereto. A directional control valve  28  is fluidly connected along the primary supply tube  26  between the main hydraulic power unit  22  and the primary hydraulic motor  24 . The directional control valve is constructed and arranged for infinitely variable positioning capability. Thus it can control the direction of fluid flow through the main hydraulic motor as well as the amount of fluid allowed to flow through the main hydraulic motor. Operation of the directional control valve  28  in a first direction permits the pressurized liquid to flow from the hydraulic power unit  22  to the primary hydraulic motor  24 , via the primary supply tube  26 , to rotate the primary hydraulic motor  24  in a first direction; and operation of the directional control valve in a second direction causes the primary hydraulic motor to rotate in a second direction. Directional control valves either mechanical, electro-mechanical, pneumatic-mechanical, servo-mechanical or suitable combinations thereof, that are suitable for infinitely controlling hydraulic fluid flow are well known in the art. In the preferred non-limiting embodiment the directional control valve utilized is a manually actuated, spring-centered, three way valve.  
         [0036]     The passive heave compensation assembly designated generally at  50  includes means for providing passive coordinated reciprocal movement between the payload position and the destination position. The means for providing passive coordinated reciprocal movement between said payload position and said destination position generally includes a gas spring accumulator  52 . The gas spring accumulator includes a variable volume gas portion  54  and a variable volume oil portion  56 , said gas portion and said oil portion being separated by a piston member  58 . The gas portion  54  is fluidly coupled to an infinitely variable gas pressure source via a gas supply tube  60 . The gas pressure source illustrated herein as at least one tank  62  filled with compressed fluid. The oil portion  56  is fluidly coupled to said primary supply tube  26  preferably between the primary hydraulic motor  24  and the directional control valve  28 . The gas spring accumulator  52  is constructed and arranged to passively dampen response of the winch drum  12  thereby reducing relative movement between the payload position and destination position. The means for providing passive coordinated reciprocal movement between the payload position and the destination position may also include a gas intensifier  64  fluidly connected to the gas supply tube  60  preferably between the gas pressure source  62  and the gas portion  54  of the gas spring accumulator  52 . The gas intensifier  64  is constructed and arranged to accept pressurized gaseous fluid from the gas pressure source  62  at a first pressure and deliver the gaseous fluid to the gas portion  54  of the gas spring accumulator  52  at a second pressure. In the preferred non-limiting embodiment the second pressure is greater than said first pressure. In a most preferred embodiment the first pressure is at least about 500 pounds per square inch and the second pressure is up to about 5,800 pounds per square inch.  
         [0037]     The active heave compensation assembly generally designated at  70  includes means for providing active coordinated reciprocal movement between the payload position and the destination position. The means for providing active coordinated reciprocal movement generally includes a secondary hydraulic power unit  72  for supplying pressurized liquid to a secondary hydraulic motor  74 , said secondary hydraulic power unit fluidly coupled to said secondary hydraulic motor via a secondary supply tube  76 . The secondary hydraulic motor is mechanically connected to said drum  12  for providing selective power assisted rotational movement thereto. A servo-valve  76  is fluidly connected along said secondary supply tube  78  preferably between said secondary hydraulic power unit  72  and said secondary hydraulic motor, the servo-valve having a controller  80  for generating a signal to said servo-valve in response to data received from at least one sensory input  82 , wherein pressurized fluid supplied by said secondary hydraulic unit  72  is allowed to flow to said secondary hydraulic motor  74  for rotation thereof. Suitable controllers and sensory inputs are well known in the art and may include, but should not be limited to controllers and sensors constructed and arranged to monitor drum acceleration, drum position, drum speed, gas spring piston position, payload acceleration, payload deceleration, gas intensifier pressure, stored fluid pressure, directional control valve position, pressurized fluid pressure, suitable combinations thereof and the like. The active heave compensation assembly  70  may also include a booster accumulator  84  connected along the secondary supply tube  78  between the secondary power unit  72  and the servo-valve  76 . The booster accumulator is constructed and arranged to maintain a supply of pressurized fluid during operation of the secondary power supply  72 . The booster accumulator includes a variable volume gas portion  86  and a variable volume oil portion  88 , the gas portion and the oil portion being separated by a piston member  90 .  
         [0038]     It should also be noted that while the preferred non-limiting embodiment disclosed herein fluidly connects the hydraulic components using tubing alternative means suitable for connecting hydraulic accessories which are well known in the art including, but not limited to hoses, pipes, manifolds, castings and suitable combinations thereof are also contemplated and may be utilized to connect the hydraulic components of the instant invention.  
         [0039]     All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.  
         [0040]     It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification.  
         [0041]     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.