Patent Publication Number: US-2015083985-A1

Title: Method and System for Operating Winches and Use Thereof

Description:
THE TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a method and a winch system for operating winches, in particular electrical winches. The invention relates also to a preferred used. In particular the invention relates to a method for powering a winch on a vessel handling loads at an end of a line associated with a winch drum, the winch being powered by means of one or more electric motors and one or more hydraulic motors via a gear system. The invention also relates to a system for powering a winch handling loads. 
     A preferred use of the inventive method and system is also disclosed. 
     BACKGROUND FOR THE INVENTION 
     Electrically driven winches are commonly driven by means of motors based on alternating current (AC) or direct current (DC) at a relatively high number of revolutions per minutes, for example 2000 revolutions per minutes, and with a relatively low torque. 
     For winches having a high pulling capacity, this implies that a gear must be arranged between the winch drum and the motor and that the gear must have a relatively high gear or transmission ratio. The total mass moment of inertia of the gear and the motor will result in a winch having a “stiff” characteristic, i.e. that the winch will have low sensitivity for variation in loads. 
     To have a winch that is sensitive to load variations is of importance for winches onboard for example anchor chain handling vessels where the load often may be stuck in the seabed while the vessel simultaneously moves up and down, following the motion of the sea. With a “stiff” winch the tension in the steel wire may quickly increase and representing a risk for the steel wire or the associated jointing elements to break, or at least causing damage to the winch and associated gear. 
     Winches onboard anchor handling vessels are mots commonly powered by hydraulic motors producing a relatively high torque and operating at low revolutions per minutes. 
     This may imply that the gear or transmission ratio within the gears between the winch drum and the motors may be relatively low. In addition, for such hydraulic motors the control of the appearing torque may quickly be achieved if the appearing load exceeds the torque that the motors are designed to handle. The load control may easily be adjusted from zero to the maximum capacity by means of the winch control system. With such solution the winch will be very sensitive for variations in load in the steel wire out from the drum. If the winch works against an object that is stuck in the seabed, the winch characteristic will be “soft”, so that the winch quickly will pull steel wire in or out as the vessel moves up and down du to waves. 
     JP 2009-269693 discloses a rope winch on a tug boat, capable of imparting back tension according to advancing speed of the tugboat. The rope winch includes a drum for winding a rope and an electric motor for rotating and driving the drum in a rope delivering direction or a rope winding direction. Moreover the winch includes a drum control unit for performing an inverter control of the electric motor to control rotation of the drum and a gear box arranged between the electric motor and the drum. The winch also includes a hydraulic tank and a hydraulic motor interlocked and connected with the gear box, a flow passage switching valve for switching a flow passage of hydraulic fluid and a relief valve and is also provided with a hydraulic circuit incorporated in the gear box. The drum control unit makes the hydraulic motor function as a resistor by switching a flow passage of hydraulic fluid by means of the flow passage switching valve when the drum is rotated in the drum delivering direction. 
     OBJECTS OF THE PRESENT INVENTION 
     It is an object of the present invention to provide a new winch system with an improved gear box for electrically driven winches, in order to improve the dynamic properties of the winch system during operation. 
     Another object of the present invention is providing a winch system that over-comes the drawbacks of both electrically and hydraulically powered prior art winches. 
     THE PRESENT INVENTION 
     The above objects are achieved by means of a winch system as defined in the independent method claim, characterized in that the one or more hydraulic motors are operated when the load in the line exceeds a predetermined load level for taking care of quick hauling in or paying out the line to compensate for vertical motion of the winch, for example due to waves, and the output shaft(s) of said one or more hydraulic motors are connected to the drum shaft through combination of a sun wheel, planet wheels and parallel wheels. 
     The preferred embodiments, variants and alternatives are defined by the dependent method claims  2 - 5 . 
     The system of the present invention is defined in the independent claim  6  and in the dependent claims  7 - 10 . 
     The system and a method as described is preferred used in a winch system that is installed and/or used in association with an anchor handling vessel, handling a load that is stuck in the sea bed while the vessel moves due to waves 
     One advantage of the winch system according to the present invention is that the risk for breaking the wire due to handling a load element, is eliminated, or at least substantially reduces. 
     The hydraulic loop must have installed sufficient cooling capacity to be able to transport away generated heat. This will reduce the need for taking care of the regenerative effect or braking effect from the electromotor in the electrical supply system onboard the vessel. 
     Such hybrid solution will in addition to the described way of operation also provide redundancy to the operation of the winch system. This implies that if there should be a break-down in the electrical motor system, the load may be hoisted by means of the hydraulic motor system. Correspondingly, in case of a break-down of the hydraulic motor system, the electrical motors may be used. 
     The system according to the present invention is well suited for use in case a load such as an anchor or a chain have got stick in the sea bed and required large forces from freeing them off the sea bed, while the vessel at the same time moves because of surface sea. 
     The system and method according to the present invention, i.e. the combination of electrical and hydraulic motors in association with the specified gear box provide improved properties and improved load regulation control on the gear box. This is achieved by using the combination of planet gears and the annulus gear solution. 
     Since many of the modern vessels are provided with heavy duty diesel-electrical systems and thus have a surplus of electrical energy available, it may be appropriate to also use such energy to power the winches. 
    
    
     
       SHORT DESCRIPTION OF THE DRAWINGS 
       In the following an embodiment of the invention shall be described in further detail to enable the skilled person to understand the invention, wherein: 
         FIG. 1  shows schematically a diagram of ne embodiment of the gear system according to the present invention, showing the various essential parts of the winch system according to the invention; and 
         FIG. 2  shows schematically a vertical through the gear box, seen along the line A-A in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS AS SHOWN IN THE FIGURES 
       FIG. 1  shows schematically a diagram of one embodiment of the winch system  10  showing the various essential parts of the winch system  10  according to the invention. It should be appreciated that essential elements such as bearings for rotating input shafts  30 ,  18 ,  32  and rotating output shaft  16  are not shown. Moreover, the gear box housing is only schematically shown. It is apparent for the skilled person in the art that several types of bearings may be used. Given the total applicable rotational speeds and expected design load impact in the system the skilled person will know how to dimension and design such bearings and the surrounding housing of the gear box  17 . 
     Moreover, it should also be appreciated that that the power for driving the drum is both electric and hydraulic power, the energy sources and the control and circuit for delivery of such energy is not shown. 
     The winch system  10  comprises a winch drum  11 , rotatable arranged on a shaft (not shown) that preferably is horizontally arranged. Sufficient length of a rope or a wire  12  is wound up on the drum  11 . One of the sides the drum  11  is provided with cut teeth  14  along the periphery of the drum side, projecting radially, the edges of the teeth  14  being aligned parallel with axis of rotation of the drum  11 . Said teeth  14  mesh together with the teeth  15  a gear wheel  24  rigidly fixed at the end of an output shaft  16  of a gear box  17 . The shaft  16  is parallel with the axis of rotation of the drum  11 , and rotation of the output shaft  16  correspondingly rotates the drum  11 . 
     On the opposite side of the gear box  17 , three input shafts  30 ,  18  and  32  lead into the gear box  17  for providing the required torque to the output shaft  16 , and consequently the drum, either for paying out or winding in wire  12 . 
     A central input rotatable shaft  18  is driven by a hydraulic motor  21  and the opposite end of the shaft  18  is provided with a sun wheel (gear)  22 . The shaft  18  and the sun wheel  22  form a rigid and an integrated unit and rotate in parallel with the drum  12  and aligned with the rotational axis of drive wheel  24 . 
     In order to transfer torque from the hydraulic motor  21  to the drum  11  via the sun wheel  22  and the drive wheel  24  at the end of output shaft  16 , the opposite end of the output shaft  16  (leading into the gear box  17 ) is provided with a rigidly fixed disc  25 . The disc  25  may for example have a circular shape or may be formed as wings, arranged perpendicular on the axis of the output shaft  16 . 
     As shown in  FIG. 1 , three planet wheels  26  are rotatable arranged on three separate shafts  27 , the shafts  27  being rigidly fixed to the disc  25  or wings fixed to the output shaft  16 . 
     Moreover, the axis of rotation of each of the planet wheels  26  is parallel with the axis of the output shaft  18 , the drum  11  and the sun wheel  22 . The planet wheels are also provided with cut teeth being are in mesh engagement with the teeth on the sun wheel  22 . 
     Moreover, the planet wheels  26  are also in mesh contact with a rotatable arranged annulus  28  which is provided with cut teeth arranged along the interior annulus surface. The annulus  28  rotates around an axis which is aligned with the axis of the sun wheel  22 , the disc  25  and the output axis  16 , while it is in parallel with the drum rotational axis and the planet wheels  27 . The annulus  28  is moreover provided with an additional annulus  28 ′ rigidly fixed to the annulus  28  meshed with the planet wheels  26 , thus rotating around the same axis of rotation. The additional annulus  28 ′ is provided with cut teeth arranged around the entire periphery of the additional annulus  28 ′, and they are in mesh contact with the gear wheel  18  on a shaft  30  of a first electric motor  29 . 
     Further the winch system  10  is also provided with a second electric motor  31  the shaft  32  of which being rigidly connected to a gear wheel  19  with cut teeth. Both gear wheels  18  and  19  are in mesh contact the external toothed surface of the second annulus  28 ′. 
       FIG. 2  shows schematically a vertical section of the gear box, seen along the line A-A in  FIG. 1 . 
     The Winch System  10  According to the Present Invention Functions as Follows: 
     In general, the method according is characterized in that the winch drum  11  is driven by one or more electric motors  29 ,  31  combined with one or more hydraulically powered hydraulic motors  21  via a gear box  17 . The winch drum  11  is driven by said three motors  21 ,  29  and  31  via a common output shaft  16  being interconnected through the gear box  17 . The gear wheel  24  rigidly fixed to the shaft  16  drives the winch drum  11  for paying out or winding in the load carrying wire, line or chain  12 . 
     The hydraulic motor  21  is in idling engagement with the gearbox  17  and the output shaft  16  when system is powered by the electric motors  29 ,  31 . In this stage the sun wheel is passive free rotating. The hydraulic motor does not start producing torque until the load in the wire  12  becomes higher than a predefined upper load limit. 
     The hydraulic motor provides a proper torque control through the shaft  18  driving the planet wheels  26  and imposing rotation to the annulus  28 , while the electric motors  29 ,  31  are meshed with the outer annulus  28 ′, forming an integral part with the inner annulus  28 . The output shaft  16  from the gear box  17  is fixed to the disc  25  carrying the shafts  27  for the planet wheels  26 . 
     The mesh ratio between the gear wheel  24  on the output shaft  16  and the sun wheel  22  on the shaft  18  of the hydraulic motor  21  is relatively low, for example in a range of 1:5. The corresponding mesh ratio between the gear wheel  24  on the output shaft  18  and annulus  28 ,  28 ′ is relatively high, for example in a range of 1:50. During normal operation the sun wheel  22  is locked from rotation, while the planet wheels  26  rotate freely around the locked sun wheel  22 . 
     During this normal operation the electrical motors  29 ,  31  are powered, rotating the wheels  18 ,  19 , bringing the annulus  28 ,  28 ′ to rotate and hence transferring torque on to the output shaft  16  through the planet wheels  26  that are rotating and causing rotation of the disc  25  supporting the planet wheels  26 . 
     The torque is controlled by means of the winch control system and is based on valves exerting pressure regulation in the hydraulic motor  21 . 
     The torque control on the hydraulic motor  10  is set to a predefined load level so that the hydraulic motor is idling as long the required torque is below said predefined or set load value. If the pull or load in the wire exceeds the preset level for the hydraulic motor  21 , the hydraulic motor  21  is powered, starting to introduce torque into the gear box  17  shaft  16 . This means that the winch  10  will pay out wire  12  from the drum  11  and thus minimize any possible detrimental build-up of tension in the winch drum wire  12 . Thus, the hydraulic motor will function as a safety measure opening up when the tension in the wire approaches the pre-determined set value. 
     Moreover, the solution according to the present invention makes it possible to add the output from the electrical motors  29 ,  31  with the output from the hydraulic motor  21 . This may in particular be of interest when deploying, since the hydraulic motor  21  may load deploy without having installed corresponding pumping effect. The effect generated is easily absorbed by means of a cooling circuit in the hydraulic system. Such a cooling circuit is simple and economical to calculate and dimension for absorbing the maximum effect of the hydraulic motor. 
     In conclusion, according to the present invention, the hydraulic motor  21  is coupled to the output shaft  16  via the sun wheel  22  of the planet gear, while the electro motors  29 ,  31  are coupled to the output shaft  16  via the outer gearwheel  28  of the planet gear. The output shaft  16  is connected to the planet carrier  25  of the planet gear. The hydraulic motor is connected all the time, but starts to operate only when the load of the line  12  becomes too high.