Patent Publication Number: US-2019185119-A1

Title: Holding Means for Holding an Apparatus Against a Metallic Surface

Description:
TECHNICAL FIELD 
     The present application relates to a holding means for holding an apparatus against a metallic surface. 
     BACKGROUND 
     A steel hull of a vessel or of other installation requires operations to be made on it, namely an inspection, a maintenance or a repair operation. Such an operation can be cleaning it with a water jet, with a moving brush, with an ultrahigh water jet, cavitation or with any other cleaning means; performing construction work such as installing a sea chest plug or welding; performing at least one measurement in a certain location of the hull, for example for the purposes of executing a detailed survey; or capturing a video feed from a location on the hull. 
     Certain difficulties can be observed when performing such an operation. For example, one difficulty may be when the hull is immersed partially, which creates difficulties when reaching the part of the hull above the surface. Another difficulty may be, for example, related to the specific shape of the hull, which may vary substantially from structure to structure. A further difficulty may be, for example, related to the dimensions of a metallic hull, which are usually observed in structures with big dimensions, when compared to the size of the components used for performing the operation. 
     A known approach for performing an operation on a steel hull, involves the use of a Remote Operated Vehicle (ROV). The ROV is manoeuvred to the vicinity of the intended position on the hull, carrying the necessary components with it for performing the operation. It can be deployed either from a support vessel or from the structure of which the hull is part. This approach is well-known in the prior-art and is considered a proven technology. However, it has critical drawbacks that make impractical. 
     One of the drawbacks is that any surfaced portion of the hull cannot be reached by the ROV. Hence, an additional solution has to be used for performing the operation on the surfaced parts of the hull. 
     Another drawback, is that the ROV does not move in an effective manner when near the upper part of the submerged portion of the hull, known as the splash zone. This zone has challenging hydrodynamic conditions for the driving means of the ROV to tackle, in order keep the ROV in place in relation to the hull. One of the problems in this zone is that the ROV is neutral in water due to its buoyancy element, and therefore needs to be fully submerged in order to operate. Heave and water current bring the ROV, involuntarily, to surface. This can be partially overcome by waiting for the appropriate weather conditions to be achieved. However, if the solution depends on weather conditions, which can be quite strict, it might take a long time to achieve them. For example, in practice it was observed during an intervention to a hull in the North Sea, which required a weather limit of 2.0 m Hs, that it took ten days before the intended limit could be achieved. A scenario in which a structure such as a vessel has to wait for several days before certain weather conditions are achieved can become quite expensive, since during that period the vessel may have to endure through parking costs without generating any income from the usual commercial exercise of the vessel. 
     Another known approach is to send divers into the water to the perform a similar operation to the ROV. This approach is also well-known. Although, in certain circumstances, a diver might be quicker or more precise than a ROV, many of the drawbacks of the ROV are still observed in this approach. Any surfaced portion of the hull cannot be reached by the diver. Also, a diver must be careful and take into account the hydrodynamic conditions when moving in the splash-zone. Further, this approach significantly depends on the skills and experience of the diver. Moreover, some hulls when in operation, need to have thrusters running, which make this approach impossible due to high risk. 
     GENERAL DESCRIPTION 
     Described is a holding means for holding an apparatus against a metallic surface, comprising: at least one magnetic means for exerting a pushing force on the apparatus towards the metallic surface; and a moving means for moving the apparatus on the metallic surface, wherein the moving means is arranged to bear the pushing force from the at least one magnetic means, on the metallic surface. 
     In one embodiment, the moving means comprises a continuous track system for moving the apparatus on the metallic surface. The continuous track system comprises: a continuous track; and at least two conducting means for conducting the continuous track. 
     In another embodiment, the continuous track of the continuous track system is arranged around the at least one magnetic means, for keeping the at least one magnetic means separated from the metallic surface. 
     In a further embodiment, the continuous track is adapted with at least one inner guide for keeping the continuous track aligned with the movement of the apparatus on the metallic surface, and wherein at least two conducting means is adapted with a groove for the at least one inner guide to engage thereon. 
     In one embodiment the continuous track is a track belt. 
     In another embodiment, the at least one magnetic means is arranged in a Halbach array for augmenting a magnetic field of the magnetic means facing the metallic surface. 
     In a further embodiment, the metallic surface is a metallic hull. In one embodiment, the metallic hull is a part of a vessel. In another embodiment, the metallic hull is a part of an offshore unit. 
     Also, disclosed is an apparatus for performing an operation on a metallic surface, comprising at least one holding means. 
     In one embodiment, the apparatus comprises at least one pivoting means for pivoting the at least one holding means in relation to the apparatus, wherein the at least one pivoting means is arranged for adapting the at least one holding means to a shape of the metallic surface. 
     In another embodiment, the at least pivoting means is arranged to pivot in a transverse axis of the apparatus. In a further embodiment, the at least one pivoting means is arranged to pivot in a longitudinal axis of the apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings. 
         FIG. 1  is a schematic illustration showing an orthogonal projection of a first embodiment of the holding means against a metallic surface. 
         FIG. 2  is a schematic illustration showing a side view of the first embodiment in the longitudinal direction of the same. 
         FIG. 3  is a schematic illustration showing an orthogonal projection of a second embodiment of the holding means against a metallic surface, wherein the five permanent magnets are arranged in a Halbach array, as is shown by the arrows therein shown. 
         FIG. 4  is a schematic illustration showing a side view of the second embodiment in the transverse direction of the same. 
         FIG. 5  is a schematic illustration showing a side view of a third embodiment of the holding means against a metallic surface, in the transverse direction of the same, wherein a track belt is shown with inner guides. 
         FIG. 6  is a schematic illustration showing another side view of the third embodiment shown in  FIG. 5 , in the longitudinal direction of the same. 
         FIG. 7  is a schematic illustration showing an orthogonal projection of a fourth embodiment of the holding means against a metallic surface, wherein a track belt is shown being conducted around several instances of the holding means and also being driven by a central drum. 
         FIG. 8  shows a schematic illustration showing a side view of the fourth embodiment in the longitudinal direction of the same. 
         FIG. 9  shows a schematic illustration showing a side view of a fifth embodiment of the holding means against a metallic surface, in the longitudinal direction, while this embodiment moves over a protrusion in the metallic surface. 
         FIG. 10  shows a schematic illustration similar to  FIG. 9 , with some components hidden. 
         FIG. 11  shows a schematic illustration showing an orthogonal projection of an embodiment of an apparatus including a frame and four instances of the fourth embodiment shown in  FIGS. 7 and 8 . 
         FIG. 12  shows a schematic illustration similar to  FIG. 11  including more components connecting the two pairs of instances of the fourth embodiment, the connections being done in the longitudinal direction. 
         FIGS. 13 to 15  show schematic illustrations of the embodiment of the apparatus including various holding means shown in  FIGS. 11 and 12 , in three different positions of a metallic surface in relation to the waterline. 
         FIGS. 16 to 18  show the same schematic illustrations of  FIGS. 13 to 15  respectively from a side view. 
     
    
    
     DETAILED DESCRIPTION 
     A first embodiment of a holding means  3  is shown in  FIG. 1 . The holding means  3  includes five permanent magnets  311  which are arranged in an array. The array is parallel to the metallic surface  11 . Also included in this embodiment, are four wheels  35  for allowing motion on the metallic surface  11  and to keep a fixed distance between the permanent magnets  311  and the metallic surface  11 . Each wheel  35  rotates on a shaft  351  which traverses the array of permanent magnets  311 . 
     The wheels  35  are held against the metallic surface  11  due to a pushing force being exerted by the five permanent magnets  311 , towards the metallic surface  11 . This pushing force results from the magnetic attraction of the permanent magnets  311  towards the metallic surface  11 . In this embodiment, the pushing force is transferred from the five permanent magnets  311  to the shafts  351 , which then transfer it to the wheels  35  in contact with the metallic surface  11 . Hence, at the same time the four wheels  35  and the shafts  351  sustain the pushing force against the metallic surface  11 , they also enable the movement on the metallic surface  11 . 
     If the permanent magnets  311  contact directly with the metallic surface  11 , then, the wheels  35  do not bear the pushing force on the metallic surface  11 . This can happen, for example, due to the wheels  35  being arranged with an insufficient diameter or due to the wheels being arranged with a shaft traversing the array of permanent arrays  311  in a position that would set the wheels  35  to far away from the metallic surface  11  in relation to the permanent magnets  311 . 
     Hence, in this embodiment, the configuration of the diameter of a wheel  35  and of the position of its rotation axis in relation to the permanent magnets  311 , allow arranging the wheels  35  for bearing the pushing force from the permanent magnets  311  on the metallic surface  11 . This aspect can be better observed in  FIG. 2 , where a side view of  FIG. 1  is shown. 
     Also, other types of magnetic means can be used, instead of a permanent magnet  311 , for example an electromagnet. 
       FIG. 2  shows a side view of the first embodiment, shown in  FIG. 1 , in the longitudinal direction of the motion enabled by the wheels  35 . The distance between the metallic surface  11  and the closest surface of the permanent magnets  311  can be observed between the wheels shown. Since the permanent magnets  311  do not touch the metallic surface  11 , then then pushing force is correctly exerted to the shafts  351  and wheels  35 . 
     Moreover, since the diameter of the wheels  35  and the position of the shafts  351  in relation to the permanent magnets  311  is kept fixed, then, the distance between the surface of the permanent magnets  351  which is most proximal to the metallic surface  11  and the points of contact of the wheels  35  on the metallic surface  11 , will be kept constant. This constant distance will be observed while the holding means  3  moves on the metallic surface  11 . 
     A second embodiment of the holding means  3  is shown in  FIGS. 3 and 4 . In this embodiment, the permanent magnets  311  shown in the first embodiment are arranged in a Halbach array, which can be observed with the illustrative arrows drawn in  FIGS. 3 and 4 . Each arrow represents the orientation of the magnetic field of each permanent magnet  351 . 
     This rotating pattern of magnetisation augments the magnetic field facing the metallic surface while cancelling the magnetic field on the other side. In particular, the flux cancelled on one side reinforces the flux on the other side. Consequently, this arrangement allows achieving a stronger pushing force and, as a result, allowing, for example, to hold heavier weights against the metallic surface  11 . 
     Other arrangements of the magnetic means could be achieved for changing the magnetic field. For example, a sub-optimal arrangement of the Halbach array can also be implemented. 
     In  FIGS. 5 and 6  a third embodiment of the holding means  3  is shown. This embodiment is similar to any of the previous embodiments, with the difference that it includes a continuous track system with a track belt  3411  for moving on the metallic surface  11 , instead of the wheels  35  shown in any of the  FIGS. 1 to 4 . 
     The continuous track system includes rollers  3421  for conducting the track belt  3411 . These rollers  3421  are similar to the wheels  35  shown in  FIGS. 1 to 4 , which directly contact the metallic surface  11 . However, in this third embodiment, the track belt  3411  is the component that contacts directly with the metallic surface  11  and the rollers  3421  conduct is the track belt  3411 . 
     The track belt  3411  in this third embodiment is arranged around the permanent magnets  311 . This allows keeping them protected from any metallic piece that might be floating in the water or that might be detached from the metallic surface  11  due to the magnetic attraction. In this way, the track belt  3411  works as a shield for the permanent magnets  311 . 
     The track belt  3411  shown includes two inner guides  343 , which engage on an opposing groove  344  presented by the roller  3421 . This engagement allows keeping the track belt  3411  aligned with the movement on the metallic surface  11 . Whenever the holding means  3  turns on the metallic surface  11 , which happens at the same time the permanent magnets  311  exerts a pushing force that is transferred to the track belt  3411 , the inner guides  343  make the track belt  3411  also turn. Also, a different number of inner guides  343 , and the corresponding grooves  344 , can also be implemented. 
     In the  FIGS. 7 and 8 , a fourth embodiment is illustrated including a track belt  3411  being conducted around four instances of the holding means  3  shown in any of the  FIGS. 5 to 6 . These instances work together, side by side, in exerting the pushing force. The track belt  3411  is conducted around the permanent magnets  311 , including two inner guides  343 , of which only one is visible, and several rollers  3421 . Moreover, the track belt  3411  is also conducted around a driving drum  345  which allows driving the track belt  3411 . 
     Some components have been hidden in the  FIGS. 7 and 8  for allowing a better visualization of the components surrounded by the track belt  3411 . However, these may also be needed in order to keep any of the rotation axes of the conducting means fixed in relation to each other, namely the rollers  3421 , the outer rollers  3422 , and the driving drum  345 . Moreover, in order to allow fine tuning the tension of the track belt  3411 , at least one rotation axis of a conducting means may be adapted to include a mechanism for regulating its position. 
     In this fourth embodiment, the driving drum  345  transmits torque to the track belt  3411 . The driving drum  345  engages the track belt  3411  from the inside, i.e. not on the surface of the track belt  3411  that contacts the metallic surface  11 . For this effect, the driving drum  345  includes a rubber coating to ensure good grip and increase the coefficient of friction. Moreover, the two outer rollers  3422  are also included to ensure a good grip for the track belt  3411  around the driving drum  345 . The positions of these outer rollers  3422  change the amount of force which is transmitted to the track belt  3411 . Preferably, the track belt  3411  is guided at least  180  degrees around the driving drum  345 . 
       FIGS. 9 and 10  show a fifth embodiment of the holding means  3  including three pivots  211 , each arranged to pivot in a transverse axis in relation to the movement on the metallic surface  11 . This embodiment includes the wheels  35 , but it could easily include a continuous track system instead, like the shown in any of the  FIGS. 5 and 6 . Also, the rotation axis of the pivots  211  is parallel to the rotation axis of the wheels  35 . Moreover, the pivots  211  connect to an apparatus and allow to adapt the holding means  3  to a shape of a metallic surface  11 . For example, a hull of a ship is not a flat surface, presenting a curved shape in some parts. Also, the metallic surface  11  may have a protrusion  111 , such as a welded joint. In such case, when this fifth embodiment passes over it, the pivots  211  work together to adapt the permanent magnets  311  accordingly. This adaptation is show in  FIG. 9  and more clearly in  FIG. 10 . 
       FIGS. 11 and 12  show an embodiment of an apparatus  2  including a frame  25  and four instances of the fourth embodiment shown in  FIGS. 7 and 8 . Also included in this embodiment of the apparatus  2  are the pivots  211  for adapting the holding means  3  to different shapes of the metallic surface  11 . Some of the pivots  211  pivot each instance of the fourth embodiment in a transverse axis, and others pivot each longitudinal pair of instances in a longitudinal axis. 
     The frame of the apparatus  2  may be used to carry any tools or devices needed for performing an operation on the metallic surface  11 . 
       FIGS. 13 to 15  the embodiment of the apparatus  2  from  FIGS. 11 and 12 , in three different positions of a metallic surface  11 , for example a hull of an offshore unit, in relation to the waterline.  FIGS. 16 to 18  show the same scenario of  FIGS. 13 to 15 , respectively from a side view. An embodiment of an apparatus  2  including at least one instance of a holding means  3  can be used for performing an operation on a metallic surface which is partly submerged. For example,  FIGS. 14 and 17  illustrate the position of the apparatus  2  in the, so called, splash zone of the metallic surface  11 . In this case, also the apparatus  2  is partly submerged, working under the complex hydrodynamic conditions observed thereon. 
     Any of the above embodiments can be used to perform an operation in a metallic hull. The metallic hull may be part of a vessel, such as a ship, or part of an offshore unit. An offshore unit is considered to be any structure engaged in offshore operations including drilling, oil and gas production and storage, accommodation and other support functions. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.