NL2015491B1

NL2015491B1 - Retractable Flanking Rudders.

Info

Publication number: NL2015491B1
Application number: NL2015491A
Authority: NL
Inventors: Simon Van Buren Edwin; Sander Groen Niels
Original assignee: Damen Marine Tech Holding B V
Priority date: 2015-09-23
Filing date: 2015-09-23
Publication date: 2017-04-20

Abstract

A retractable steering assembly (40) for mounting in a hull of a vessel, comprising a rudderstock (44) along a rudder axis (Ar), and adapted for repositioning the rudderstock between a retracted state and an extended state with respect to the hull. In the extended state, the rudderstock is pivotable via a neck bearing (46) around the rudder axis with respect to the hull. The retractable steering assembly comprises first guiding members (50) that are fixed to the hull, and a second guiding member (52) that surrounds the rudderstock. The first and second guiding members are configured to cooperate to restrict radial motion of the neck bearing and rudderstock in the retracted and extended states, while allowing rectilinear motion of the neck bearing and the rudderstock along the rudder axis with respect to the first guiding member between the retracted and extended states.

Description

Retractable Flanking Rudders

TECHNICAL FIELD

[0001] The invention relates to a retractable rudder assembly for mounting in or on a hull of a vessel, and to a vessel comprising a retractable rudder assembly.

Furthermore, the invention relates to a method for retrofitting a hull of a vessel to incorporate a retractable rudder assembly.

BACKGROUND ART

[0002] Rudder assemblies are generally employed in ships to provide steering capability by means of a pivotable submerged surface. This surface, referred to as “rudder blade”, is adapted to be pivoted around a rudder axis, to generate hydrodynamic pressure differentials between the two sides of the surface. Typically, the predominant direction of motion for ordinary vessels corresponds with a keel line of the hull. The orientation of the rudder blade with respect to the keel line then defines the rudder’s pivot angle. Tilting/pivoting of the rudder blade with respect to the ship hull causes the oncoming flow of water to exert substantial hydrodynamic forces on the blade. The component of these forces perpendicular to the flow direction is associated with a lift force, which is proportional to the pivot angle of the rudder blade and which exerts a torque on the ship as a whole. The resulting steering forces cause the ship to alter course. These steering forces correlate with the angle of incidence of the rudder blade with respect to the propulsion direction, as well as with the propulsion speed of the entire ship with respect to the water.

[0003] Typically, a rudder assembly is provided with a so-called “rudderstock”, which is a shaft that is directly mechanically fixed to the rudder blade on one end and typically coupled to a steering actuator on another end, so that the rudderstock passes steering torques from the actuator on to the rudder blade. The steering actuator can thus be used to adapt the pivot angle of the rudder blade with respect to the vessel hull to vary the generated steering forces.

[0004] Rudder assemblies with one or more retractable rudder blades are known. Such retractable rudder assemblies are capable of selectively transitioning between a retracted state wherein the one or more rudder blades are partially or even fully withdrawn inside the contours of the ship hull when steering is not required, and an extended state wherein the one or more rudder blades protrude with respect to the ship hull so as to allow pivoting of the rudder blade(s).

[0005] Patent document CA1198939 (FULLER) describes a rotatable and retractile rudder blade that is slidably mounted for rectilinear movement in a collar assembly, which is mounted in a bearing that is coupled to a nozzle of a ducted propeller assembly. The collar is rotatable to vary the angle of the rudder blade relative to a keel line of the vessel. The retractable rudder mechanism in CA1198939, however, requires a relatively long rudder blade to be able to transition between the extended and retracted states with respect to the collar. In addition, the collar assembly requires a complex bearing mechanism for allowing linear motion of the rudder blade through the collar assembly in a manner that ensures sufficient sealing against water leakage. A reliable leak proof implementation of such a rudder mechanism will be difficult to implement, especially for larger ships.

[0006] It would be desirable to provide a reliable retractable rudder assembly for a vessel, and a vessel provided with such an assembly.

[0007] A vessel may be provided with a retractable flanking rudder system. The term “flanking rudder” refers herein to an additional rudder blade or pair of rudder blades fitted forwards of the vessel’s propulsion system (e.g. propeller), to provide steerage and improve maneuverability when the vessel moves along the aft direction. Rearward vessel maneuvering capability is not continuously needed. Llanking rudder blades cause significant drag effects and increase fuel consumption if retained in the extended when the vessel is moving forward. The flanking rudder assembly should therefore preferably be employed (in the extended state) only when the vessel moves rearwards. Vessels adapted for pushing or pulling a flotilla of transport barges through inland waterways may greatly benefit from such a retractable flanking rudder system. A flotilla of barges may be several hundreds of meters long and difficult to control because of mass inertia and unwanted water and wind forces. The pilot of the vessel typically needs to maneuver the vessel and barge flotilla several times in the forward and rearward directions, to be able to pass relatively sharp river bends. The corresponding intermittent flanking rudder deployment calls for a reliable retractable flanking rudder assembly.

SUMMARY OF INVENTION

[0008] According to a first aspect of the invention, there is provided a retractable steering assembly for mounting in or on a hull of a vessel, comprising a rudderstock extending along a rudder axis. The retractable steering assembly is adapted for repositioning the rudderstock between a retracted state and an extended state with respect to the hull. In the extended state, the rudderstock is pivotable via a neck bearing around the rudder axis and with respect to the hull. The retractable steering assembly comprises at least one first guiding member that is fixable with respect to the hull, and a second guiding member that surrounds the rudderstock. The first and second guiding members are configured to cooperate and restrict radial motion of the neck bearing and rudderstock in the retracted and extended states, while allowing rectilinear motion of the neck bearing and the rudderstock along the rudder axis with respect to the first guiding member into the extended state.

[0009] In general, the rudderstock serves to transfer axial steering torques from a steering mechanism to a rudder blade in such a manner that the rudderstock and rudder blade are jointly pivotable about the rudder axis to provide steering capability. The rudderstock is directly mechanically attached or attachable to a rudder blade, typically at one end thereof. The rudderstock may be fixed to an edge of the rudder blade, or may partially or fully extend through the rudder blade. Preferably, a rudder blade is integrally formed with the rudderstock prior to installation in a rudder system. This allows the stock and blade to be mutually aligned and mechanically bonded by methods known in the art, to yield good structural integrity. Accordingly, the proposed retractable rudder assembly may be mounted in/on the vessel with the rudderstock and blade already in place. In alternative embodiments, the assembly may initially be mounted in/on the vessel without rudderstock and blade, which may be installed in the assembly at a later stage. Yet other embodiments of the assembly are conceivable, wherein at least one rudderstock is provided with coupling means for selectively connecting and/or detaching a (replaceable) rudder blade e.g. to facilitate maintenance.

[0010] In the “retracted state”, the rudderstock and rudder blade are at least partially retracted with respect to the hull. In the “extended state”, the rudderstock and rudder blade protrude with respect to the hull to allow pivoting of the rudder blade to provide steering capability.

[0011] The neck bearing is arranged around the rudderstock and is provided closest to the rudder blade. In the extended state, the rudderstock (and rudder blade) protrude outward from the hull, so as to allow pivoting via the neck bearing around the rudder axis and with respect to the hull. Preferably, the rudder axis is oriented predominantly or entirely along a vertical direction with respect to the vessel hull, to optimize steering forces in the lateral directions. During vessel navigation, lateral hydrodynamic steering forces acting on the rudder blade create so-called “non-axial steering torques” with respect to the neck bearing. These non-axial steering torques tend to bend the rudder blade and lower portion of the rudderstock away from the rudder axis. The neck bearing should be sufficiently robust to counteract such non-axial steering torques. The first and second guiding members in the proposed retractable steering assembly cooperate to allow translational motion of the neck bearing and rudderstock between the retracted and extended states, while restricting radial motion of the rudderstock and neck bearing in both states. This allows the neck bearing to be lowered together with the rudderstock and rudder blade, and to remain relatively close to the rudder blade in the extended state, so that the non-axial steering torques may be kept within acceptable boundaries without needing a complexly shaped bearing arrangement for passing through the rudder blade.

[0012] The retractable steering assembly preferably forms part of a flanking rudder system, with the rudder blade positioned at a leading side near a propulsion system of the vessel. The proposed retractable rudder assembly with torque reducing transitioning mechanism is particularly effective if employed on a vessel with flanking rudders near the propulsion system.

[0013] According to an embodiment, the retractable steering assembly comprises a rudder trunk that directly surrounds the rudderstock. In this embodiment, the second guiding member is fixed to the rudder trunk and is configured to cooperate with the first guiding member to allow rectilinear motion of the rudder trunk together with the rudderstock and the neck bearing along the rudder axis, to jointly lower the rudderstock, the rudder trunk, the second guiding member, and the neck bearing along the rudder axis into the extended state.

[0014] The term “rudder trunk” refers to a watertight enclosure around an upper portion of the rudderstock. The rudder trunk is typically located above the neck bearing or incorporates the neck bearing on a lower end of the trunk. The rudder trunk may additionally include an additional bearing near an upper side of the rudderstock, which is referred to as a “carrier bearing”. The inclusion of a rudder trunk that is repositionable together with the rudderstock and neck bearing yields a robust retractable steering mechanism in which rotational bearing and non-axial steering torque reduction are implemented in a reliable manner.

[0015] To improve robustness, the second guiding member may be fixed directly to the rudder trunk. The second guiding member may be a separate body that is directly mechanically attached to the rudder trunk or may form an integral part of the rudder trunk (e.g. made via a single casting procedure).

[0016] According to an embodiment, the rudderstock is directly attached to a rudder blade, and the retractable steering assembly comprises a base with a lower passageway for passing through the rudder blade outwards through the hull into the extended state.

[0017] According to a further embodiment, the rudder trunk is at a lower end fixed to a streamline body, which is jointly translatable with the rudderstock and the rudder trunk along the rudder axis with respect to the first guiding member between the retracted and extended states. In this embodiment, the streamline body is at least partially situated inside the lower passageway when the assembly is in the extended state.

[0018] The lower passageway in the base of the assembly allows passage to the rudder blade when transitioning between the extended and retracted states. In the extended state, the rudder blade and a lower portion of the associated rudderstock protrude outward from the vessel hull. In the extended state, the streamline body fixed at the lower end of the rudder trunk is allowed to fill up the space in the lower passageway that is left open by the (extended) rudder blade. This bars the lower passageway and reduces hydrodynamic drag.

[0019] The streamline body may have a cross-sectional shape similar to a cross-sectional shape of the rudder blade, so that an annular space between the lower passageway on the one hand and the streamline body and rudder blade on the other hand may be kept small for each possible position between the retracted and extended states. Preferably, a lower face of the streamline body follows a contour of an outer surface region of the vessel hull in the extended state. This allows optimization of the rudder blade surface that will be available for pivoting in the extended state. Especially the upper portion of the rudder blade should be made as large as possible, because the upper part of a propeller (which will be near the upper rudder blade portion) contributes greatly to the hydrodynamic propulsion forces (and thus to the associated steering forces).

[0020] According to a further embodiment, the rudder blade has an elongated shape that, in an alongship direction, extends along a rudder plane. Here, the at least one first guiding member comprises elongated linear bodies that extend parallel with the rudder axis and at lateral distances along an athwartship direction away from the rudder plane.

[0021] The lateral arrangement of linear guiding bodies increases the robustness of the rudder assembly with respect to the non-axial steering torques that correspond to lateral hydrodynamic steering forces on the rudder blade with a significant force component along the athwart direction.

[0022] Preferably, the linear guiding bodies are transversely displaced over the lateral distances in direct perpendicular directions away from the rudder axis. In this case, the elongated bodies extend along body axes that are substantially parallel with the rudder axis and which lie in a transverse plane through the rudder axis and orthogonal to a plane spanned by the rudder blade.

[0023] Preferably, the second guiding member comprises a collar that is directly fixed to the rudder trunk, and which is provided with apertures for passing through the elongated linear bodies. The guiding members may for example be formed as reinforced rods with low-friction surfaces adapted for providing a sliding motion of the rudder blade with respect to the hull between the retracted and extended states.

[0024] According to an embodiment, the retractable steering assembly comprises a housing adapted for mounting on an inner region of the hull of the vessel. The housing defines a chamber for accommodating the rudder blade and at least part of the rudderstock in the retracted state.

[0025] The housing and chamber define an accommodation region for the rudder blades and lower portion of the rudderstock in the retracted state, which is separate from and sealed with respect to other regions inside the hull.

[0026] According to a further embodiment, the rudder streamline body comprises a lateral circumferential protrusion provided with a lower sealing member adapted for engaging the base to seal off the lower passageway of the housing in the extended state.

[0027] During navigation, the operational propulsion system typically generates significant hydrodynamic forces that create an overpressure in the water on the expulsion side. The retractable rudder assembly is typically located near the propulsion system and subject to this overpressure. Cooperation between the circumferential protrusion with lower sealing member on the one hand and the base with lower passageway on the other hand (in the case that the rudder mechanism is in the extended state) efficiently seals the chamber from the water body located outside the hull. This sealing helps to reduce or even avoid unwanted propulsion-induced overpressure effects on components inside the chamber (e.g. on bearing/sealing mechanisms in an upper portion of the chamber).

[0028] The rudder streamline body may define an outer lateral periphery with a shape that is similar to an inner lateral periphery of the lower passageway, but defining an annular space in the extended state. The lower sealing member may for example comprise a layer of soft resilient material arranged along the circumferential protrusion of the rudder streamline body. This layer of resilient material may be translated downwards into to extended state, to engage with, cover, surround, fill up, or otherwise seal off the annular space left open between the rudder streamline body and the inner lateral periphery of the lower passageway.

[0029] Preferably, the lateral protrusion and first sealing member are provided on an upper side of the streamline body. The first sealing member may be provided downwards with respect to the circumferential protrusion, and face towards the passageway, so that a rectilinear motion of the rudder streamline body towards the extended state will cause this sealing member to engage with an upward periphery of the lower passageway. Alternatively or in addition, the housing may be provided with such a lateral circumferential protrusion and sealing member for sealing off the lower passageway.

[0030] According to a further embodiment, the housing comprises an upper wall with an upper aperture for passing through the rudderstock, and the second guiding member comprises an upper sealing member adapted for engaging the upper wall of the housing to seal off the upper aperture in the retracted state.

[0031] During navigation, the operational propulsion system typically generates an underpressure in the water located near the inlet side. The retractable rudder assembly is typically located near the propulsion system and subject to this underpressure, in the case of a primary rudder provided at a rear side and a propulsion system operated in a reverse direction, as well as in the case of a flanking rudder provided at a leading side and a propulsion system operated in a forward direction. Cooperation between the second guiding member with upper sealing member on the one hand and the upper wall with upper aperture on the other hand (in the case that the rudder mechanism is in the retracted state) efficiently seals the region above the chamber from water and/or air located inside the chamber. This sealing helps to reduce or even avoid unwanted propulsion-induced underpressure effects on components associated with the upper aperture and above.

[0032] According to a further embodiment, the rudder blade comprises a lateral flange at a free distal end, wherein the lateral flange extends outwards beyond an inner circumference of the lower passageway, and wherein the base defines an enlarged recess directly below the lower passageway, to accommodate the lateral flange and cover the lower passageway in the retracted state.

[0033] The lateral flange at a free distal end of the rudder blade and the enlarged recess below the lower passageway of the base jointly close off the lower passageway when the rudder blade is in the retracted state. A tortuous path is thereby formed near the lower passageway, which prevents solid object from entering the chamber when the rudder blade is in the retracted state, and reduces the probability of jamming and failure of the steering assembly. This is particularly effective for inland waterways with an abundance of solid objects floating in the water (e.g. debris, tree branches, etc).

[0034] According to a further embodiment, the at least one first guiding member extends through the chamber and is fixed with respect to the upper wall and the base of the housing, and wherein the second guiding member is configured to translate along the first guiding member between the upper wall and the base inside the chamber.

[0035] According to an embodiment, the retractable steering assembly comprises a steering actuator coupled to the rudderstock, and adapted for exerting a steering torque on the rudderstock about the rudder axis. The steering actuator is jointly translatable with the rudderstock and the second guiding member along the rudder axis with respect to the first guiding member between the retracted and extended states.

[0036] A steering actuator that is translatable along with the rudderstock allows a simple yet robust rudder transitioning mechanism. This obviates the need for a complex error-prone transmission mechanism between a stationary steering actuator and a translatable rudderstock.

[0037] According to an embodiment, the retractable steering assembly comprises an end plate for delimiting upwards rectilinear motion of the rudderstock along the axis when transitioning into the retracted state.

[0038] The end plate may define a robust mounting point that is stationary with respect to the vessel hull. The end plate may for example be associated with the deck or floor of the steering gear room of the vessel.

[0039] According to an embodiment, the retractable steering assembly comprises a mounting body onto which the steering actuator is mounted and from which the rudderstock is rotatably suspended. The mounting body is supported on the upper wall of the housing in the extended state.

[0040] Preferably, the rudder trunk is rigidly fixed to the mounting body and can jointly be translated with the mounting body, the rudderstock, the rudder blade and the confinement member along the axis, to transition between the retracted state and the extended state.

[0041] According to a further embodiment, the steering actuator is provided on an upper side of the mounting body.

[0042] According to a further embodiment, the guiding members are coupled with respective distal ends to the lower wall of the housing and with opposite distal ends to the end plate.

[0043] According to an embodiment, the retractable steering assembly comprises at least one socket, which is arranged at the base of the housing. The socket defines a void for accommodating a distal end of a guiding member and for rigidly fixing the guiding member to the base. The socket may be provided with a supply conduit for selectively supplying a hydraulic fluid to the void, to force the distal end of the guiding member out of the void and to release the guiding member from the socket.

[0044] In this embodiment, the one or more guiding members extend at least partially through the chamber (which serves to accommodate the rudderstock and -blade), and are therefore frequently exposed to water. The provision of a socket with pressurization conduit in/on the base of the housing allows rigid fixation of the guiding member to the base of the housing, and allows controlled detachment of the guiding member from the base. By selectively supplying hydraulic fluid (e.g. oil) to the void of the socket, a pressure inside the void will be increased, which may serve to force the distal end of the guiding member out of the socket. This yields and controllable and user-friendly mechanism for removing the guiding members from the chamber for maintenance and/or replacement purposes.

[0045] According to a second aspect, and in accordance with the advantages and effects described herein above, there is provided a vessel, comprising a hull with: - a propulsion system for generating hydrodynamic propulsion forces with respect to a water body, and - a retractable steering assembly in accordance with the first aspect, which is mounted in or on the hull near the propulsion system.

[0046] Typically, a propulsion system creates a local pressure/displacement field in the body of water, which causes the entire vessel to obtain a macroscopic forward (or rearward) speed with respect to the entire water body. The phrase “near the propulsion system” refers herein to a location that is sufficiently close to the propulsion system for the retractable rudder assembly to experience the local hydrodynamic propulsion forces, which exceed the macroscopic hydrodynamic forces due to macroscopic vessel displacement.

[0047] Preferably, the propulsion system comprises a propeller that is rotatable with respect to the hull about a propeller axis. More preferably, the propeller is provided with a nozzle that surrounds the propeller and has a leading aperture and a trailing aperture that face predominantly along the propeller axis, in forward and aft directions respectively.

[0048] According to an embodiment, the retractable steering assembly forms part of a flanking rudder system with the rudder blade positioned at a leading side near the propulsion system. The vessel may be adapted for maneuvering a large flotilla of coupled barges for transporting bulk cargo.

[0049] According to a further embodiment, the propulsion system comprises a propeller and a propeller shaft which are jointly rotatable with respect to the hull about a propeller axis. In this embodiment, the retractable steering assembly includes at least two flanking rudder blades that are arranged near a leading side of the propeller and on lateral sides of the propeller shaft. For example, two such rudder blades may be provided, which are coupled to the hull on port and starboard sides of the propeller axis. The propulsion system may include one or more propellers and corresponding propeller shafts, each with a corresponding retractable steering assembly and couple of rudder blades.

[0050] According to a third aspect of the invention, there is provided a method for retrofitting a vessel with a hull comprising a propulsion system, wherein the method comprises: - providing a retractable steering assembly according to the first aspect, and - attaching the retractable steering assembly in or onto the hull near the propulsion system, so as to allow the rudderstock to move respect to the hull along a rectilinear trajectory between: a retracted state wherein the rudder blade is at least partially retracted with respect to the hull, and an extended state wherein the rudder blade protrudes with respect to the hull to allow pivoting of the rudder blade and to provide steering capability.

BRIEF DESCRIPTION OF DRAWINGS

[0051 ] Embodiments will now be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts. In the drawings, like numerals designate like elements. Furthermore, multiple instances of an element may each include separate letters appended to the element number. For example, two instances of a particular element “42” may be labeled as “42a” and “42b”. In that case, the element label may be used without an appended letter (e.g., “42”) to generally refer to every instance of the element, while the element label will include an appended letter (e.g., “42a”) to refer to a specific instance of the element whenever the distinction is material.

[0052] Figure 1 schematically shows a side view of a vessel provided with a retractable rudder assembly according to an embodiment; [0053] Figure 2 schematically shows a perspective view of an embodiment of a retractable rudder assembly in the extended state; [0054] Figure 3 presents a perspective view of the embodiment of Figure 2, but now in the retracted state; [0055] Figure 4 presents a lateral cross-section of the embodiment in Figure 2; [0056] Figures 5a and 5b show frontal cross-sections of a retractable rudder assembly in the retracted state and the extended state respectively, and [0057] Figure 6 shows a perspective cross-section of a portion of a retractable rudder assembly in the retracted state.

[0058] The figures are meant for illustrative purposes only, and do not serve as restriction of the scope or the protection as laid down by the claims.

DESCRIPTION OF EMBODIMENTS

[0059] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the figures. Cartesian coordinates will be used to describe spatial relations for exemplary embodiments.

[0060] Reference symbol X is used to indicate a longitudinal direction, which corresponds to the elongated direction of the vessel hull. Prepositions “front” and “rear” pertain to this longitudinal direction X. The “for” or “forward” direction +X extends towards the bow of the vessel. The “aft” direction -X extends towards the stem of the vessel.

[0061] Reference symbol Y is used to indicate a lateral direction that is perpendicular to the longitudinal direction X. This lateral direction Y generally relates to the terms “left” and “right”. The lateral direction Y relates to the athwartship directions (“aporf ’ i.e. towards the port side +Y of the vessel, and “astarboard” means towards the starboard side -Y).

[0062] Reference symbol Z is used to indicate a vertical direction that is perpendicular to X and Y. Prepositions “above” and “below” pertain to the vertical direction Z.

[0063] It should be understood that the directional definitions and preferred orientations presented herein merely serve to elucidate geometrical relations for specific embodiments. The concepts of the invention discussed herein are not limited to these directional definitions and preferred orientations. Similarly, directional terms in the specification and claims, such as “longitudinal”, “leading”, “trailing”, “top,” “bottom,” “left,” “right,” “up,” “down,” “upper,” “lower,” “proximal,” “distal” and the like, are used herein solely to indicate relative directions and are not otherwise intended to limit the scope of the invention or claims.

[0064] Figure 1 schematically shows a perspective view of a vessel 10, which in this exemplary embodiment forms a pusher tug 10 that is suitable for marine and/or inland waterway navigation. Such a pusher tug 10 may be adapted for maneuvering a flotilla of mutually coupled barges for transporting bulk cargo.

[0065] The vessel 10 comprises a hull 12 with an elongated shape along a longitudinal direction X, which corresponds to the (main) propulsion direction of the vessel 10. The hull 12 defines a bow 14 in a forward direction +X, a stem 16 in an aft direction -X, and a keel 18 on a lower side of the hull 12.

[0066] On a lower side of the stem 16, the hull 12 comprises a propulsion system 24 and a primary mdder 32, which is pivotably coupled to the hull 12 via a primary rudderstock 34. In this example, the propulsion system is formed by a ducted propeller assembly 24 that comprises a propeller 26, a propeller shaft 30, and a nozzle 28. The propeller 26 is fixed to the propeller shaft 30 to form a body that is rotatably coupled to the hull 12. The propeller 26 is rotatable with respect to the hull 12 about a (virtual) propeller axis Ap to generate hydrodynamic propulsion forces. The nozzle 28 forms a non-rotating shell that surrounds the propeller 26.

[0067] The exemplary vessel 10 is further provided with a flanking mdder system comprising a retractable mdder assembly 40. In this exemplary embodiment, the retractable mdder assembly 40 is fixed in the hull 12 and located in a mounting region 22 near the ducted propeller assembly 24, on a forward side thereof. The retractable steering assembly 40 includes two flanking mdder blades 42a, 42b that are arranged on lateral sides of the propeller shaft 30. The two flanking mdder blades 42a, 42b protmde predominantly downwards with respect to the vessel hull 12 and are coupled to the hull 12 on port and starboard sides of the propeller shaft 30 (only one flanking mdder blade 42 is visible in Figure 1). Each flanking mdder blade 42 is directly coupled to a mdderstock 44 that extends along a corresponding mdder axis Ar.

[0068] Exemplary retractable mdder assembly 40 embodiments are further explained with reference to Figures 2-6.

[0069] Figures 2 and 3 present perspective views of an embodiment of a retractable mdder assembly 40, depicted in the extended state and in the retracted state respectively. The retractable mdder assembly 40 is fixed with respect to the hull 12, located in a mounting region 22 thereof. The exemplary mdder assembly 40 comprises a set of two mdder blades 42a, 42b and associated mdderstocks 44a, 44b. Each mdder blade 42 is directly attached to a corresponding mdderstock 44, which extends at one distal end inside the mdder blade 42, where it is fixed. This mdderstock 44 forms a rigid shaft that extends along a mdder axis Ar, which in this embodiment is directed predominantly along the vertical direction Z. In the retracted state, the mdder blades 42 are at least partially retracted inside the hull 12. In the extended state, the rudder blades 42 protrude with respect to the hull 12.

[0070] In Figure 2, the exemplary retractable rudder assembly 40 is depicted in the extended state, wherein the rudder blades 42 protrude downwards with respect to the hull 12, to provide steering capability. In the extended state, the rudderstocks 44 extend downwards to allow the rudder blades 42 to protrude at least partially below the mounting region 22 of the hull 12.

[0071] The retractable rudder assembly 40 comprises a steering actuator 58, and a support body 66 onto which the steering actuator 58 is mounted. The rudderstocks 44 are attached to and suspended from the support body 66, in a manner that allows the rudderstocks 44 and associated rudder blades 42 to rotate about the rudder axes Ar with respect to the support body 66.

[0072] Steering torques generated by the steering actuator 58 are transferred via the rudderstocks 44 to the rudder blades 42, and cause the rudderstocks 44 and the rudder blades 42 to jointly rotate with respect to the hull 12 about the respective rudder axes Ar. Such torques are referred to herein as “axial steering torques”. Each rudderstock 44 is directly surrounded in radial directions by an associated rudder trunk 45. The rudder trunks 45 are fixed to and suspended from the mounting body 66. The mounting body 66 is translatable together with the rudder trunks 45, the rudderstocks 44, and the rudder blades 42 along the rudder axes Ar, to transition between the retracted and extended states. A streamline body 48 is fixed at a lower end of each rudder trunk 45. The streamline body 48 has a transverse cross-sectional shape (in XY-plane), which is similar to a transverse cross-sectional shape of the rudder blade 42.

[0073] The retractable rudder assembly 40 comprises a transitioning mechanism for repositioning the rudder blades 42 between the retracted and extended states. The transitioning mechanism comprises first guiding members 50 that are fixed relative to the hull 12, and second guiding members 52 arranged around the rudderstocks 44 and adapted for confining movement of the rudderstocks 44 in directions transverse to the corresponding rudder axes Ar.

[0074] In this example, the first guiding members 50 comprise rigid rods 50a, 50b, 50c, 50d, which are fixed with respect to the hull 12. The rigid rods 50a-50d are configured to cooperate with the second guiding members 52 to allow rectilinear motion of the rudder blades 42, rudderstocks 44, rudder trunks 45, and streamline bodies 48 along the rudder axes Ar with respect to the hull 12, when transitioning between the retracted and extended states. In this example, the rectilinear motion of these rudder components 42-48 along the rudder axes Ar coincides predominantly with the vertical direction Z. Cooperation between the guiding members 50, 52 ensures that radial motion of respective rudder trunks 45 and rudderstocks 44 away from the corresponding rudder axes Ar is prevented in all positions along the rectilinear trajectories.

[0075] In this example, each second guiding member 52 is formed as a collar, which is directly fixed to an associated rudder trunk 45 at a lower end thereof, and situated directly above the associated streamline body 48. The collar 52 is provided with vertically extending apertures (not indicated) for passing through and cooperating with associated rods 50, to allow rectilinear sliding motion of the collar 52 and rudder trunk 45 with respect to the rods 50 along the rudder axis Ar. The cooperating collar 52 and rods 50 allow the lower end of the rudder trunk 45 to be kept as close as possible to the rotatable rudder blade 42, both in the retracted and extended state.

[0076] The retractable rudder assembly 40 comprises a housing 54 that is accommodated inside the vessel hull 12. The housing 54 comprises several walls that define chambers 55 a, 55b. Each chamber 55 accommodates a respective rudder blade 42 and at least part of the associated rudderstock 44 in the retracted state. The housing 54 comprises an upper wall 60 and a base 62, which delimit the chambers 55 from above and below respectively. When the rudder blades 42 are in the extended state, the support body 66 with the steering actuator 58 is supported on the upper wall 60 of the housing 54.

[0077] The guiding rods 50 are mounted in a fixed arrangement with respect to the housing 54. The guiding rods 50 extend through the respective chambers 55, and are fixed with respect to the upper wall 60 and the base 62 of the housing 54. The second guiding members 52 are slidably arranged inside the chambers 55 along the guiding rods 50.

[0078] The base 62 of the housing 54 comprises lower passageways 63 for passing through the rudder blades 42 outwards through the hull 12 when the system is lowered. In the extended state, the streamline bodies 48 are at least partially situated inside the lower passageways 63 of the housing 54.

[0079] The retractable steering assembly 40 comprises an end plate 68 for delimiting upwards rectilinear motion of the rudderstocks 44 along the rudder axes Ar when transitioning into the retracted state. A lifting device 80, 82 is also included, which is adapted for translating (i.e. raising and lowering) the rudder blades, stocks, trunks, and streamline bodies 42-48 along the rudder axes Ar to effect transitioning between the retracted and extended states. This lifting device 80, 82 is in this example formed as a hydraulic linear actuator comprising a piston cylinder 80 and a piston rod 82, which are coupled in a mutually slideable manner. In this example, the piston cylinder 80 is fixed with an upper end to the upper wall 60 of the housing 54, and the piston rod 82 is fixed with an upper end to the support plate 66. When the lifting device 80, 82 is energized to lift the rudder assembly from the extended state into the retracted state, support plate 66 moves upwards away from the upper wall 60, carrying the steering actuator 58 and the rudder blades 42, stocks 44, trunks 45, and streamline bodies 48 along via the fixed first guiding rods 50.

[0080] The guiding rods 50 extend further from the upper wall 60 of the housing 54 onwards to the end plate 68. The guiding rods 50 are fixed to the end plate 68 to keep the end plate 68 at a fixed distance from the upper wall 60 of the housing 54.

[0081] In Figure 3, the exemplary retractable rudder assembly 40 is depicted in the retracted state, wherein the rudder blades 42 are retracted inside the hull 12. Figure 3 illustrates that in the retracted state, each chamber 55a, 55b of the housing 54 accommodates one rudder blade 42 and at least part of the associated rudderstock 44 and streamline body 48.

[0082] The upper wall 60 of the housing 54 comprises upper apertures 61, each for passing through an associated rudderstock 44 and a surrounding rudder trunk 45.

[0083] Sufficient space is defined between a lower side of the end plate 68 and an upper side of the support plate 60 to accommodate the steering actuator 58 in the retracted state.

[0084] Figure 4 presents a lateral cross-section of the embodiment from Figures 2 and 3. Figure 4 illustrates that the rudder trunk 45 includes a neck bearing 46 on a lower trunk side and a carrier bearing 47 on an upper trunk side. In the extended state, the rudderstock 44 and associated rudder blade 42 are pivotable via the neck bearing 46 and the carrier bearing 47 around the rudder axis Ar, and with respect to the rudder trunk 45 and streamline body 48. The cooperating collar 52 and rigid guiding rods 50 allow the neck bearing 46 of each rudder trunk 45 to be kept as close as possible to the associated rudder blade 42, in both the retracted state and the extended state.

[0085] A lower surface of the streamline body 48 is adjacent to and faces an upper surface of the associated rudder blade 42. Preferably, the adjacent upper and lower surfaces are sufficiently near to reduce or even minimize hydrodynamic drag caused by an intermediate gap between the streamline body 48 and the rudder blade 42 in the forward position, but sufficiently far to avoid direct engagement (i.e. jamming) of the streamline body 48 and the rudder blade 42. In this example, the lower surface of the streamline body 48 and the upper surface of the rudder blade 42 approximate an outer contour of the mounting region 22 of the vessel hull 12.

[0086] The rudder streamline bodies 48 define outer lateral surfaces with shapes that are congruent with inner lateral surfaces of the lower passageways 63. In the extended state, annular spaces are formed between these inner and outer lateral surfaces. The rudder streamline body 48 comprises a lateral circumferential protrusion 70, which forms a ledge that extends along the periphery on an upper side of the streamline body 48. The circumferential protrusion 70 is provided with a lower sealing member 72. The lower sealing member 72 may for example comprise a layer of soft resilient material (for example rubber, polytetrafluoroethylene, or a suitable elastomer) attached to the circumferential ledge 70 of the rudder streamline body 48. When the rudder assembly 40 transitions to the extended state, the lower sealing member 72 is translated downwards, to ultimately engage the base 62 of the housing 54. The lower passageway 63 of the housing 54, more particularly the annular space between the rudder streamline body 48 and the inner lateral periphery of the lower passageway 63, is thereby sealed off. This sealing of the lower passageway 63 prevents excess hydrodynamic pressure and/or forces resulting from the propulsion system to create an overpressure inside the chamber 55.

[0087] In this example, also the second guiding members 52 comprise sealing members 74. These second sealing members 74 may be formed e.g. by annular gaskets provided on an upper side of the collar 52. This upper sealing member 74 is adapted for abutting the upper wall 60 of the housing 54 on an inner surface of the respective chamber 55, when the rudder assembly 40 is in the retracted state. The second sealing members 74 help to establish seals between the collars 52 on the one hand and the upper apertures 61 of the housing 54 on the other hand. This prevents fluid leakage from the chamber 55 via the upper aperture 61 upwards into the hull 12.

[0088] Figures 5a and 5b show frontal cross-sections of the exemplary retractable rudder assembly in the retracted state and the extended state respectively. The rudder blades 42 have elongated shapes that, in a forward steering position extend along virtual rudder planes that are parallel with the alongship direction X and the vertical direction Z. Each pair of guiding rods 50a-50b and 50c-50d extends parallel with the corresponding rudder axis Ar. The respective guiding rods 50a-50d are spaced at transverse distances Ay away from the respective rudder axes Ar, along the (positive and negative) athwartship directions ±Y (in this case, predominantly perpendicular from the rudder axes Ar). This lateral arrangement of the guiding rods 50a-50d renders the rudder assembly 40 more robust against the non-axial steering torques related to lateral steering forces acting on the rudder blades 42 with respect to the neck bearings 46 and second guiding members 52.

[0089] Figure 6 shows a perspective cross-section of a portion of a retractable rudder assembly 40 in the retracted state. Only one lateral side of the assembly is depicted, but it should be understood that the opposite lateral side of the assembly may be provided with similar features, e.g. in a mirror-symmetric arrangement.

[0090] At a free distal end, the depicted flanking rudder blade 42a is provided with a lateral flange 84a. In this case, the flange 84a is defined by a lateral periphery of a plate portion mounted onto the free distal end of the rudder blade 42a. This plate portion corresponds to an initial cutout of a rudder blade’s cross-sectional shape from the mounting region 22 of the hull 12, prior to installation of the retractable rudder assembly 40. In this exemplary embodiment, the flange 84a and the surrounding hull region 22 may be substantially flush when the assembly 40 is in the retracted state, to reduce hydrodynamic drag effects.

[0091] The flange 84a extends laterally outwards beyond an inner circumference of the lower passageway 63a. In addition, the base 62 of the housing 54 defines an enlarged recess 86a provided directly below the lower passageway 63a. The size and shape of the enlarged recess 86a allow it to accommodate the lateral flange 84a, so that cooperation between the lateral flange 84a and the recess 86a yields an obstruction of the lower passageway 63a when the rudder blade 42a is in the retracted state. A tortuous path 88a is thereby formed near the lower passageway 63a, which prevents solid object from entering the chamber 55a, so that the probability of jamming and failure of the steering assembly 40 is effectively reduced.

[0092] Figure 6 shows that this exemplary embodiment of the retractable steering assembly 40 may include sockets 64a, 64b, which are provided at the base 62 of the housing 54. Each socket 64 is associated with a distinct guiding rod 50, and defines a void for accommodating a distal end of the associated guiding rod 50, in order to rigidly fix the guiding rod 50 to the base 62. Each socket 64 is provided with a supply conduit 65 for selectively supplying a fluid into the void. Via controlled supply of hydraulic fluid to the void, a pressure inside the void may be increased. Such controlled pressurization helps to force the distal end of the guiding rod 50 out of the void, to effectively decouple the guiding rod 50 from the socket 64.

[0093] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than by the foregoing description. It will be apparent to the person skilled in the art that alternative and equivalent embodiments of the invention can be conceived and reduced to practice. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0094] In the above-described embodiments, the first and second guiding members for guiding the transitions between the retracted and extended states were implemented as a plurality of reinforced rods and collars with sliding bearings. In alternative embodiments, the first and second guiding members may be formed differently, for example as rails and wheels or grooves and protrusions, provided that the resulting guiding mechanism allows relative linear motion but restricts or even prevents transverse relative motion of the guided parts.

[0095] In the above-described embodiments, a hydraulic piston arrangement was provided as a lifting device for moving the retractable rudder assembly along the rudder axes between the retracted and extended states. In alternative embodiments, the lifting device may be implemented differently, for example by means of pulleys and cables or guy wires, a rack-and-pinion arrangement, a screw spindle, electric cylinder, or similar actuator arrangement.

[0096] Although the exemplary embodiments in the detailed description related to pushing tugs, the principles of the retractable flanking rudders described herein and defined in the claims also pertain to other types of vessels, like sea-going boats and ships (e.g. short sea boats and ships).

[0097] Vessels may generally be provided with at least one, but also with two or even more rudder blades per retractable rudder assembly.

[0098] Any or all features relating to the retractable rudder assemblies that have been described herein above and defined in the claims may also be present in vessels with multi-propulsion system configurations (e.g. with two or more propellers). These propulsion systems may be laterally spaced across the vessel hull (e.g. at the stem) at lateral mutual distances, preferably in an athwart symmetrical arrangement. In this case, a retractable rudder assembly may be accommodated in the hull in distinct regions corresponding with the distinct propulsion systems. These distinct rudder assemblies may be independently moveable between their corresponding retracted and extended states, to be able to temporarily provide augmented steering capability with respect to a selected propulsion system. LIST OF REFERENCE SYMBOLS 10 vessel (e.g. boat, ship) 12 hull 14 bow 16 stem 18 keel 22 hull mounting region 24 ducted propeller assembly 26 propeller 28 nozzle 30 propeller shaft 32 primary rudder 34 primary rudderstock 40 retractable rudder assembly (e.g. flanking rudder) 42 flanking rudder blade 44 flanking rudderstock 45 flanking mdder trunk 46 neck bearing 47 carrier bearing 48 mdder streamline body 50 first guiding member (e.g. rod, tube, bar, reinforced rails) 52 second guiding member (e.g. collar with apertures) 54 housing 55 chamber (e.g. unsealed/wet region) 58 steering actuator (e.g. hydraulic steering gear) 60 upper wall 61 upper aperture 62 base 63 lower passageway 64 socket (for guiding rod) 65 supply conduit 66 support plate 68 end plate 70 lateral circumferential protrusion (e.g. ledge or flange) 72 lower sealing member (e.g. gasket) 74 upper sealing member (e.g. annular gasket) 80 first actuator member (e.g. piston cylinder) 82 second actuator member (e.g. piston rod) 84 lateral flange 86 flange accommodation recess 88 tortuous path 100 body of water

Ara first rudder axis

Arb second rudder axis

Ap propeller axis X longitudinal direction (alongship direction; forward/aft directions ±X) Y transversal direction (athwart direction; aport/astarboard directions ±Y) Z vertical direction Φ angular direction (azimuthal direction)

Claims

A retractable steering assembly (40) for mounting in or on a hull (12) of a ship (10), provided with a rudder king (44) extending along a rudder axis (Ar), and adapted to reposition the rudder king between a retracted state and an extended state with respect to the trunk; wherein in the extended state, the rudder king is rotatable via a neck bearing (46) around the rudder axis and relative to the hull; wherein the retractable steering assembly is provided with at least a first guide member (50) that is fixable with respect to the hull, and with a second guide member (52) surrounding the rudder king; wherein the first and second guide members are adapted to cooperate to limit radial movement of the neck bearing and rudder king in the retracted and extended states, but to direct linear movement of the neck bearing and rudder king along the rudder axis with respect to the first guide member to the extended state.

The retractable steering assembly (40) according to claim 1, comprising a hemp sleeve (45) that immediately surrounds the stirring king (44), the second guide member (52) being secured to the hemp sleeve and adapted to cooperate with the first guide member (50) to allow linear movement of the hemp sleeve together with the rudder king and neck bearing (46) along the rudder axis (Ar), so as to lower the rudder king, the hemp sleeve, the second guide member, and the neck bearing together along the rudder axis line to the vast state.

The retractable steering assembly (40) according to any of claims 1-2, wherein the stirring king (44) is directly attached to a rudder blade (42), and wherein the retractable steering assembly comprises a base (62) with a lower passage (63) ) for allowing the rudder blade outwardly through the body (12) to the extended condition.

The retractable steering assembly (40) according to claims 2 and 3, wherein the hemp sleeve (45) is secured at a lower end to a streamline body (48), which is jointly with the rudder king (44) and the hemp sleeve along the rudder axis (Ar) is translatable relative to the first guide member (50) between the retracted and extended states, and wherein in the extended state the streamline body (48) is at least partially located within the lower passage (63).

The retractable steering assembly (40) according to claim 3, wherein the rudder blade (42) has an elongated shape extending along a rudder surface (XZ) in a longitudinal direction (X), and wherein the at least one first guide member ( 50) includes elongated linear bodies (50a, 50b, 50c, 50d) which extend parallel to the rudder axis (Ar) and are located at a lateral distance (Ay) along a transverse direction (Y) away from the rudder surface.

The retractable steering assembly (40) according to any of claims 1-5, comprising a housing (54) adapted to mount to an inner area of the hull (12) of the ship (10), the housing comprising a chamber (55 ) for accommodating the rudder blade (42) and at least a portion of the rudder king (44) in the retracted state.

The retractable steering assembly (40) according to any of claims 4-6, as far as dependent on claim 4, wherein the stirring streamline body (48) comprises a laterally peripheral protrusion (70) provided with a lower closure member (72) arranged is for contacting the base (62) in the extended state to seal the lower passage (63) of the housing (54).

The retractable steering assembly (40) according to claim 6 or 7 as far as dependent on claim 6, wherein the housing (54) comprises an upper wall (60) with an upper opening (61) for passage of the stirring king (44), and wherein the second guide member (52) comprises a higher closing member (74) adapted to contact the top wall (60) of the housing (54) in the retracted state to seal the top opening.

The retractable handlebar assembly (40) according to any of claims 3-8, as far as dependent on claim 3, wherein the rudder blade (42) comprises a laterally raised edge (84) at a free end, the laterally raised edge extending outwardly extending beyond an inner circumference of the lower passage (63), and wherein the base (62) defines an enlarged recess (86) immediately below the lower passage, to receive the laterally raised edge in the retracted state and to lower the lower passage cover.

The retractable control assembly (40) according to claim 8 or 9 as far as dependent on claim 8, wherein the at least one first guide member (50) extends through the chamber (55) and with respect to the top wall (60) and the base (62) of the housing (54) is fixed, and wherein the second guide member (52) is adapted to translease within the chamber (55) between the top wall and the base along the first guide member (50).

The retractable steering assembly (40) according to any of claims 1-10, comprising a steering actuator (58) coupled to the rudder king (44) and adapted to exert a steering moment on the rudder king around the rudder axis (Ar) wherein the control actuator together with the rudder king and the second guide member (52) along the rudder axis and relative to the first guide member (50) is translatable between the retracted and extended states.

The retractable steering assembly (40) according to any of claims 1-11, comprising an end plate (68) for restricting upward linear movement of the rudder king (44) along the rudder axis (Ar) as it passes into the retracted state.

The retractable steering assembly (40) according to claim 11 as far as dependent on claim 8, comprising a mounting body (66) on which the steering actuator (58) is mounted and on which the stirring king (44) is rotatably suspended, the mounting body in the extended position is carried on the top wall (60) of the housing (54).

The retractable control assembly (40) according to claim 12, wherein the guide members (50) are coupled with respective ends to the base (62) of the housing (54) and are coupled to the end plate (68) with opposite ends.

The retractable handlebar assembly (40) according to any of claims 3-14, as far as dependent on claim 3, comprising at least one pot (64) disposed at the base (62) of the housing (54), the pot defines a recess for accommodating an end of a guide member (50) to secure the guide member to the base, and wherein the pot is provided with a supply conduit (65) for feeding a liquid to the recess around the end forcing the guide member out of the space and releasing the guide member from the pot.

A ship (10) comprising a hull (12) with: a drive system (24) for generating hydrodynamic propelling forces relative to a body of water (100), and a retractable steering assembly (40) according to any of claims 1-15 , which is mounted in or on the hull near the drive system.

The ship (10) of claim 16, wherein the retractable steering assembly (40) is part of a flank rudder system, which is located on a front side of the drive system (24).

The ship (10) of claim 17, wherein the propulsion system (24) comprises a propeller (28) and a propeller shaft (30) that are jointly rotatable about a propeller shaft line (Aβ) and relative to the hull (12), and wherein the retractable steering assembly (40) comprises at least two rudder blades (42a, 42b) disposed on transverse sides of the propeller shaft.

A method for refurbishing a ship (10) with a hull (12) comprising a drive system (24), the method comprising: mounting a retractable steering system (40) according to any of claims 1 to 15 in or on the hull near the drive system (24) such that the rudder king (44) is movable relative to the hull along a linear path between a retracted state in which the rudder blade (42) is at least partially retracted with respect to the hull, and an extended state in which the rudder blade projects relative to the hull to allow rudder blade rotation and to provide control capacity.