WO2013014232A1

WO2013014232A1 - Driving and guiding method for marine propulsion with fins on an endless- path

Info

Publication number: WO2013014232A1
Application number: PCT/EP2012/064693
Authority: WO
Inventors: Jacob Govert Vermeiden
Original assignee: A.P. Møller-Mærsk A/S
Priority date: 2011-07-27
Filing date: 2012-07-26
Publication date: 2013-01-31

Abstract

The present invention relates to a propulsion system for a marine vessel wherein the employed means for propulsion include rotatable fins with their axis held substantially normal to the hull surface, and wherein those fins translate in a mostly submerged, not purely circular, endless path along the surface of the hull. As additional characterizations, a significant part of the path lies substantially perpendicular to the direction of the flow of water that surrounds the vessel, and the rotation axes of the fins are also substantially perpendicular to the endless path.

Description

Driving and guiding method for marine propulsion with fins on an endless- path

Field of invention

In one embodiment, the propulsion system to could resemble a large, actuated, transversal, endless chain held flush with the hull across a barge stern, chain-wheels laying flat and flush with the hull, with fins articulated on the hinges of the chain segments; the atwartships movement of the fins held at the proper rotation angle creates the propulsive force, with one row of fins moving to port, and one row of fins moving to starboard.

According to one aspect, the invention relates to a maritime vessel comprising a hull having an opening though which a propulsion system extends at least partially. The propulsive system may include at least one set of linked elements in the form of an endless chain. This endless chain may be guided in the hull along an endless path comprising at least two substantially straight atwartships parts and at least two curved parts connecting the said straight parts of the path in order to form an endless path. The endless chain may be driven on the straight parts of the path by electromagnetic or mechanical means. The guides of the endless chain on the curved parts of the endless path may translate substantially atwartships to accommodate any unavoidable and minute changes in chain length caused either by chain segments transitioning from the straight parts of the path to the curved parts of the path, or by elasticity, or by thermal expansion, or by wear.

The result is a propulsive system where propulsive means such as fins or foils are driven smoothly substantially from port to starboard and substantially from starboard to port over a part of the width of the ship in two longitudinally spaced apart rows, with their rotation axis substantially perpendicular to one or both of the hull surface and/or the flow direction, and where propulsive forces occur due to a proper rotation angle of the propulsive means along the cycle, and where all parts except the propulsive means are present in the hull without adding any bulges that would affect the flow and would cause increased hull drag.

Background

An important objective of ship designers for new ships is to achieve low fuel consumption compared to ships with a similar functionality.

It is recognised from hydrodynamics (Prandtl) that the boundary layer of a ship constitutes a layer of water of increasing speed when nearing the hull as seen from an observer immobile in the water, and that the thickness of that boundary layer increases from the fore-sections towards the aft-sections of the ship.

It is also recognised that, from an energetic point of view, an optimal marine propulsor makes maximum use of the speed gradient in the boundary layer, that is to say, it should exert the largest possible proportion of its propelling force in the part of the flow that has highest speed as seen from an immobile observer, or that has the lowest speed as seen from the ship. This is akin to a jogger running with low exertion on a band with forward speed in an airport who has the same total speed as another jogger running at higher exertion in the same direction on an immobile floor. For ships, this effect is called 'wake fraction' in the art, and is part of a larger concept called 'hull efficiency' that reflects the interaction between a propeller and the hull it propels.

In modern single-screw merchant ships, propellers make maximum use of the energy of the boundary layer ('high hull efficiency') by being put in the wake of a central skeg in the aft of the ship that directs the boundary layer towards the propeller. Some double-screw propellers utilise the same approach in wide ships. This approach is well proven. It is also well known that the attainable propulsive efficiency with this approach is limited in practice. As an example for a container feeder vessel, a very good propeller typically has open water efficiency in the vicinity of 67%, with a hull efficiency of about 108%, resulting in a total propulsive efficiency of about 73%. This percentage provides a picture that improvements of the order of 27% would be possible with an ideal propulsor. Some authors would argue that even better results would then be possible due to a narrow definition of the notion of propulsive efficiency in the industry.

Several authors have pointed to the fact that a better utilisation of the boundary layer could lead to substantial efficiency improvements, but no practical solutions have been adopted widely by the industry to date, as the rotating propeller propulsion device still is the most commonly utilised device. The present invention relates to a propulsion system for a marine vessel that operates propulsive means within the boundary layer of the ship. In this propulsion system, the employed means for propulsion include rotatable fins with their axis held substantially normal to the hull surface, and those fins translate in a mostly submerged, not purely circular, endless path along the sur- face of the hull. As additional characterizations, a significant part of the said path lies substantially perpendicular to the direction of the flow of water that surrounds the vessel, and the said rotation axes of the fins are also substantially perpendicular to the endless path. Having the fins move in this manner allows operation of the propulsive means within the boundary layer as de- sired. More precisely, the invention relates to a propulsion system for a maritime vessel comprising a hull having an opening through which the said propulsion system extends at least partially. The said propulsive system comprises at least a set of rotatably linked elements in the form of an endless chain that drive and at least partially guide the propulsive means. A guiding system guides this said endless chain in the hull along an endless path comprising at least two substantially straight atwartships parts and at least two curved parts connecting the said straight parts of the path in order to form an endless path. This guiding system transmits a part of the driving forces and moments of the source of mechanical power, a part of the hydrodynamic forces and moments of the propulsive means and a part of the propulsion forces and moments to the hull, and allows the source of mechanical power to deliver mechanical power to the propulsive means through the said endless chain.

The invention "driving and guiding method for marine propulsion with fins on an endless-path", described in this document solves a series of problems, the first being how to drive and guide the rotatable propulsive means along a path composed of substantially straight and composed of curved parts. The difficulty is that no mechanical structures in addition to the propulsive foils are desirable in the water-flow that could disrupt this flow for reasons of hydrody- namic efficiency on one hand, and that on the other hand propulsive means, which are actuated by one or several sources of mechanical power, are subjected to mechanical and hydrodynamic forces of varying intensity, direction and origin, and this at large linear speed with respect to the vessel, resulting in large forces and large moments of varying direction and intensity on the mechanical structure at high translation speed in the path. The invention provides a solution to the outlined problem by guiding and driving the propulsive means through the intermediary of a chain composed of rigid segments that are rotatably connected to each other in an endless manner, without adding any bulges on the hull or wheels in the water that would affect the flow. The invention "driving and guiding method for marine propulsion with fins on an endless-path", described in this document, solves three additional connected problems, the first being how to drive the chain that in turn drives the propulsive foils of such a system while using common sources of power in a ship such as electricity or the torque and rotation of a marine diesel, the second problem being how to avoid large dynamic and large average loading in the said chain, and the third problem being how to accommodate for the unavoidable changes in cumulative length of the said chain.

In the common utilisation of an endless chain in a mechanical environment, most forces occur at the wheels driving or the wheels driven by the chain, and the wheels jointly essentially guide the chain in addition to feeding mechanical power to it or consuming mechanical power from it. Changes in chain-length are then absorbed either through displacement of the rotation axis of one of the wheels, or through mechanical play, or through displace- ment of the free-moving parts of the chain. Forces in the chain are largely concentrated in the plane defined by the trajectory of the chain. No substantial moments are usually applied on the chain segments with respect to axes perpendicular to the rotation axes of the chain-segments.

In the marine propulsion system this invention relates to, the requirements of the chain that drives the propulsive foils are very different from the requirements of a common mechanical endless chain as described previously because:

• The propulsive means such as foils, driven by the chain, cause substantial moments and forces on the chain segments along all three axes, which in turn requires much improved guiding, and that at all locations of the chain-segments

• The cumulated weight of the chain segments and propulsive foils, at tens to hundreds of tons, is very large and would cause substantial dynamic loading and fatigue should the chain be substantially cycli- cally accelerated as it would due to polygoning if being driven by an end-wheel.

• The size of the chain elements is large and the number of segments on the curved parts of the path is very low compared to a conventional chain, which exacerbates the polygoning phenomenon and its consequences

• The required reliability and service-life in a marine propulsion environment is several orders of magnitude better in terms of cycles than in common chain applications

· The placement of shafts or marine-diesels are near horizontal and not near-vertical as would be required to drive a common mechanical chain with two straight sections in front of each other as opposed to on top of each other

The herein described invention provides a solution to drive the chain: · while using commonly accepted prime-mover solutions in a marine environment such as electromagnetic forces or diesels with near horizontal shafts. This is made clear from drawings and associated explanations.

• while allowing guiding of the chain-segments along the path in the two remaining translations and the two remaining rotations at all positions of the chain-segments. This is made clear from drawings and associated explanations.

• while reducing cyclical accelerations and dynamic loading of either the source of power or of the heavy driving chain. This is done through concentrating dynamic forces induced by the polygoning effect in the segments of the driving chain that are transiting in the curved parts of the path towards those segments transiting in the curved parts of the path.

• while allowing cumulated changes in length of the driving chain

needed for polygoning, elasticity, thermal expansion and manufactur- ing deviations. This is done through translation of the guiding system in the curved parts.

• while minimising overall force and levels in the chain and on the guiding systems in the curved parts of the path. This is done by driving the chain on the straight parts of the path in an appropriate manner, and thereby avoiding large cumulated forces in the curved parts of the path.

• While avoiding bulges in the hull or wheels in the water or other parts in the water that would affect the water-flow or would be susceptible of being damaged in the water

Background art

Propulsion by means of translating and rotating fins on an endless path with a substantial part of their path being substantially perpendicular to the flow around the ship possesses attractive features such as a higher efficiency than a rotating propeller and inherent steering, which eliminates the need for a separate rudder with the associated costs and the associated reliability issues; in addition it frees volume inside the hull for increased cargo accommodation. The higher efficiency is achieved through better utilisation of the boundary layer which reduces impulse losses, lowers hydrodynamic friction losses, lowers induced drag losses and lowers the drag of the hull itself. The higher efficiency either results in lower fuel consumption and lower installed power for the prime-movers or results in a higher service speed with the same installed propulsion power and fuel consumption. US patent no 5,401 ,196 published march 28, 1995 (Triantafyllou et al.),

French patent FR 2898580 filed 14.3.2006 (Pyre), and US 2010291814 "Fin propulsion apparatus", with priority date 2007-12-10 (Vermeiden) all disclose a propulsion systems employing flapping foils with oscillatory translation on a substantially straight path. Driving of the propulsive means does not occur utilising an endless chain that follows an endless path, and these patents do not offer useful background for the invention at hand.

US patent application WO8810207, filed 29.12.88 "propellers" (Mistry) is one of the patents describing solutions for a class of marine propulsors with rotat- ing fins placed with their rotation axis at a fixed radius from the axis or a rotating disk. These propulsors are often called cycloidal or trochoidal propulsors in the art, and the most commonly applied of such systems is the Voith Schneider propeller on tugs and ferries. These systems do not use an endless chain to drive the propulsive foils, but utilise a wheel to do so. Patents for cycloidal or trochoidal propulsors such as WO8810207 do not offer useful insight for the driving method of fin-propulsors with endless chains.

US patent US 6435827 dated 20.8.2002 "apparatus for generating a fluid flow" (Steiner) described an approach to thrust generation in a fluid in an endless path largely perpendicular to the direction of thrust, where the propulsive means are driven by a belt on a wheel and being driven by that wheel; these propulsive means always being a pair on the same rotation axis but with independent relative rotation on the said belt. This US 6435827 patent does not utilise a chain composed of rigid articulated segments, nor does it solve how to avoid putting structural elements of the propulsion system in the water-flow which would in turn generate drag and which would be susceptible of being damaged over time by the hostile sea-water environment, nor does it solve how to guide and bear the belt driving the propulsive means or the propulsive means themselves if the end-wheels are not submerged. This US 6435827 patent also includes the necessity of coaxial pairs of independently rotating propulsive means which is not utilised in the presented invention. The specific nature of driving the propulsive-means with a chain is not addressed in the US 6435827 patent and some required functions are not present if a chain where to be utilised instead of a belt: a mechanism to deal with cumulative changes in length of the chain due to polygoning is missing, a solution to drive the chain on the straight parts of the path to avoid high dynamic loading due again to polygoning is missing and the possibility to utilise sliding bearing at the curved parts of the path is not presented as a wheel is utilised in the said patent. The US 6435827 patent therefore offers a completely different solution to drive and guide the propulsive means than the presented inven- tion.

French patent FR2898580-B1 , dated 14.03.2006 utilises a chain or belt to achieve a pure rectilinear path of the propulsive foils and also does not offer insight in manners to drive or guide a driving chain as utilised in the invention set forth in this document. Prior art has so far not solved the problem of how to drive and guide the propulsive means of endless path marine propulsion systems, while:

• allowing the utilisation of a common source of power in the marine industry such as electromagnetic forces or torque from a diesel with a near-horizontal shaft

· keeping low the dynamic forces due to unavoidable polygoning of the chain-segments, and the associated material fatigue if a segmented endless chain is utilised for transmission

• minimising overall forces and losses

• accommodating cumulative changes in length of the said endless said chain that occur due to polygoning, elasticity or thermal expansion

• immobilising the said chain-segments along the two remaining translations and 2 remaining rotations all along the path in order to cope with all moments and forces applied to it.

DE 398832 A discloses a drive mechanism for a ship. The mechanism includes propulsive means configured for moving along an endless path transverse to the longitudinal axis of the ship. Brief description of the invention

It is an objective of the present invention to set forth a propulsive system which, in an operational manner, generally will increase the overall efficiency of a maritime vessel's propulsive system. This is achieved by allowing a maritime vessel to be propelled by means of a propulsion system comprising propulsive means and a hull having an opening through which the said propulsion system extends at least partially. The said propulsive means include rotatable foils; these operate in the water-flow at a varying rotation angle and at a varying translation direction to generate the propulsive force. A guiding and driving system in the propulsive system actuates these propulsive means in the hull along an endless path comprising at least two substantially straight parts oriented substantially perpendicular to the flow around the hull in the vicinity of the said opening, and the said endless path comprising at least two curved parts connecting the said straight parts of the path in order to form an endless path.

A further object of the present invention is to set forth a propulsive mechanism utilising fins or foils on an endless path as disclosed above, however further including an operable system introducing distinct contributions and advantages over prior art. The said propulsive system comprises at least a set of rotatably linked elements in the manner of an endless chain that drives the propulsive means, and at least partially guides the propulsive means. The choice of a segmented structure of rigid elements offers the possibility to simultaneously drive the said foils and guide the said foils in three translations and three rota- tions all directions, while keeping a low part-count and while avoiding material fatigue that would be caused by bending in a flexible structure such as a belt.

In some embodiments, the structure of the endless chain also may, at least partially, guide the propulsive means such that the system may be further simplified by utilising the foil-stems as part of the hinge between the segments of the said endless chain.

In some embodiments the endless driving chain that may also at least partially guide the propulsive means is itself driven specifically on one or more of the substantially straight parts of the path through electromagnetic forces or through mechanical means. This combination of characteristics at first seems complex to realise, and even more so considering the size of a marine vessel, but offers distinct advantages.

Driving the chain on the straight part of the path rather than at the turns re- duces the part of the chain that is affected by cyclical acceleration and deceleration due to polygoning, a well documented unavoidable phenomenon that occurs when a rigid segment transitions from rectilinear movement to circular movement, and which would cause significant dynamic loading of both the chain and the source of mechanical power if the chain would be driven by an end-wheel.

Driving the chain on a straight part also allows the utilisation of an electrical drive with coils placed in the frame and magnets placed in the chain- segments without introducing complex loads at the end-wheels; it also allows driving the chain with a spindle the rotation axis of which would be parallel to the path of the chain. The said spindle would in turn be driven by a conventional marine engine which can have a horizontal axis, which may be placed close to the centerline of the ship, and which would drive the said endless chain with very low cyclical acceleration/deceleration. Driving the said endless chain on the substantially straight part of the path would therefore lead to increased operational safety and lower component weight compared to an endless chain driven conventionally by an end-wheel.

Driving the very large and heavy endless chain with a conventional end- wheel drive would be problematic due to the polygoning phenomenon which causes cyclical dynamic loading of the said endless chain-material, of its hinges, of the bearing systems, and of the powering system at large applicable sizes and masses.

Driving the endless chain on a straight part involves challenges to overcome. For an electromagnetic approach, the linear bearing system of the endless chain must be designed with care to deal with the large perpendicular attraction forces inherent to such a system. For an approach involving a conventional marine engine, the rotational movement of the shaft must be transformed in a smooth rectilinear movement over a sufficient transmission surface. The size of the chain-elements involved, in the order of 1 m, and the positioning requirements of a conventional rack and pinion system, 10 micron or so, do not match well, and a specific mechanical solution involving a spindle offers distinct advantages.

According one embodiment, the endless chain may be driven on all straight parts of the path; this concentrates the cyclical acceleration/deceleration to the chain-elements at the turns and results in the lowest possible average cyclical fatigue loading throughout the endless chain.

According to one embodiment, a driving spindle is driving a segmented nut divided in conformal surfaces each mounted with elasticity on a segment of the endless chain. This elasticity serves to self-align optimally and to spread the load optimally between the available transmission surfaces.

According to one embodiment, two curved parts of the path of the endless chain translate atwartships to accommodate cumulative changes in length of the endless chain due to polygoning, due to elasticity of the chain-segments or due to thermal expansion, and to accommodate manufacturing tolerances. According to one embodiment, the endless chain is driven on two straight parts of the path, and two curved parts of the path of the endless chain translate freely atwartships to accommodate cumulative changes in length of the endless chain due to polygoning, due to elasticity of the chain-segments or due to thermal expansion, and to accommodate manufacturing tolerances. According to one embodiment, one or more complete systems are rotated substantially 90 degrees around the centreline of the vessel and are mounted in a large at least partially submerged vertical surface of the hull, with the propulsive means extending from the said vertical surface. The atwartships movement of the fins becomes a vertical movement with the same propulsive results while reducing manoeuvring capabilities.

According to one embodiment, one or more complete systems are rotated substantially 90 degrees around the centreline of the vessel and are mounted in a large at least partially submerged rudder, with the propulsive means ex- tending from the rudder. The atwartships movement of the fins becomes a vertical movement with the same propulsive results while adding further manoeuvring capabilities

The sliding connection of the segments of the endless chain with the guiding system may be realised in several ways according to common knowledge in the art with hydrodynamic bearings, with hydrostatic bearings or with wheels. The spindle-drive would also be either hydrodynamic or hydrostatic for good efficiency.

Brief description of the drawings Fig 1 is a global side-view of a vessel equipped with one propulsion system according to the invention.

Fig 2 is a general bottom view of a part of a vessel equipped with a propulsion system according to the present invention. It illustrates the rotatable propulsive foils, their path, and the segments of the chain partial vessel. Fig 3a, 3b, 3c and 3d are bottom-views of embodiments of the part of the propulsion system according to the presented invention that is generally placed inside the submerged volume, and these views illustrate important principles of the guiding and transmission system for the propulsive foils Fig 3a and 3b illustrate two embodiments of the mountings necessary to guide the endless guiding and transmission chain of the propulsive means in case wheels are utilised for the curved parts of the endless path of the propulsive means. In Fig 3b the propulsive system allows for translation of both curved-parts of the path to accommodate for changes in length of the chain; this is done by allowing the end-wheels to translate radially in the direction of the straight parts of the path. In Fig 3a only one curved part of the path can translate.

Fig 3c and 3d illustrate two embodiments of the mountings necessary to guide the endless guiding and transmission chain of the propulsive means in case sliding curvilinear guides are utilised for the curved parts of the endless path of the propulsive means. In Fig 3d the propulsive system allows for translation of both guides to accommodate for changes in length of the chain; this is done by allowing the curved-path guides to translate radially in the di- rection of the straight parts of the path. In Fig 3c only one curved part of the path can translate.

Fig 4a and 4b are a bottom view of an embodiment of electromagnetic drive of the transmission- and guiding chain of the propulsion system. Fig 4a is a global view where the coils are visible in some straight-parts of the path to drive the chain. Fig 4b is a detailed view and an enlarged detailed view of a segment of the chain with its permanent magnets; the alternating orientation of the magnets is symbolised by alternating colours in the body of the said chain segment.

Fig 5a, 5b, 5c, and 5d are bottom and side-views of embodiments of rack and pinion drive of the endless transmission- and guiding-chain of the said propulsion system.

Fig 5a and 5c are embodiments where the said endless chain is driven on the straight part by a single pinion, either with near-vertical shaft drive (fig 5a) or with near horizontal shaft drive (Fig 5c) Fig 5b and 5d are embodiments where two rack and pinion connections drive the chain on the two straight parts, and where these two pinions are driven and possibly synchronised by a gear-box driven by a single near-horizontal shaft as is usual in a merchant ship. Fig 6a and 6b are bottom and side-views of embodiments of spindle-drive of the endless transmission- and guiding-chain of the said propulsion system. Fig 6a is an embodiment where the said endless chain is driven on the straight part by a single spindle. Fig 6b shows an embodiment with one spindle on each straight part of the path, driven by a single near-horizontal shaft. Fig 7a and Fig 7b are details of the embodiments described by figures 6a and 6b. Fig 7a shows how the spindle connects to the endless chain, and fig 7b shows how the nut on the chain segments (7) is constituted of elastically connected conformal surfaces

Fig 8a, 8b and 8c are partial views of a detailed realisation of the invention according to embodiments of drawings 1 , 2, 3d, 6b, 7a, 7b, in various levels of detail through varying the distance at which the view is taken.

Fig 8b and 8c show an embodiment where moments along a transversal direction of the marine vessel, stemming from longitudinal propulsion forces exerted by the propulsive means (4) outside the hull, may be borne by two sets of vertically spaced wheels, each set of wheels following parallel, vertically spaced, identical endless paths. Figure 8c also shows how chain- segments (7) may be linked in order for moments in the longitudinal direction, caused by transversal actuation forces, to be subtractive, and lead to low average vertical guiding forces on the immobile structure. Fig 8c also shows some details of an embodiment of a system for angular control of the propulsive means based on a spindle with a nut that follows the vertical displacement of a substantially immobile grove through a hydrostati- cally lubricated grove-follower; the said grove not being visible in the figure. Detailed description of the invention with reference to the figures

Figure 1 , a side view of a marine vessel equipped with the invention shows that, according to the present invention, a marine vessel (1 ) accommodates a propulsion system in a part of a hull (2) that is substantially submerged. The propulsion system includes translating rotatable propulsion means (4) that extend through an opening (3) of a substantially submerged part of the hull (2). In this document the rudder is also seen as part of the hull and the rudder could accommodate a said propulsion system as well. Figure 2, a bottom view of the propulsor, shows that in the present invention, the said rotatable propulsion means (4) are guided in an endless path (6) characterised by substantially curved parts (12) and by complementing substantially straight parts (9) to make the said path (6) endless. The endless path (6) could contain more than two said substantially straight parts (9), but at least two of the said substantially straight parts (9) of the endless path must be substantially perpendicular to the local flow of water; in the embodiment of Figure 2, this means that the straight parts of the said endless path (6) must be atwartships.

Figure 2 also shows the common feature of all embodiments of the presented invention: an endless segmented chain (8) that drives and at least partially guides the said propulsive means (4) in the said endless path (6). The rigid segments (7) of said endless chain (8) are designated in Figures 3, but are also visible in Figure 2, which shows that each propulsive means (4) of the said propulsion system is immobilised in translation compared to at least one segment of the said endless chain (8).

The rotation angle of the said propulsive means (4) co-determines the direction and intensity of the thrust of the propulsive system; setting the rotation angle is not the subject of the present invention, but can be done in several manners including a system, fixed on the said chain segment (7) that immobi- lises in translation a given propulsive means (4), based on following the vertical displacement of a substantially immobile grove during the cycle with a rack and pinion connection, or a nut and spindle connection or a rod and arm connection with the grove follower. Another method to set the rotation angle would be to utilise an angular amplitude limiter in combination with a well chosen chord-wise position of the rotation axis of the foils, and yet another method could be the utilisation of a controllable mechanical actuator for each said propulsive means (4).

Figure 3a, 3b, 3c and 3d are all bottom views of various embodiments of the guiding system of the said endless chain (8) along the said endless path (6) of the presented invention. The said propulsive system has a fixed frame (20) which supports mountings (1 1 ) and (5) which guide and bear the said endless chain (8) along the said straight respectively said curved part of said endless path (6). These figures also display the segmented nature of the said endless chain (8) in segments (7). The said propulsive means (4), if present on a given segment (7) can be placed on any location including the hinges. Friction reduction during translation of said endless chain (8) along said path (6) is done by usual means in the form of wheels or lubricated sliding of confor- mal surfaces between the said segments (7) and said mountings (1 1 ) and (5), and the means for friction reduction are seen as either part of the said mountings (1 1 ) and (5) or part of the said segments (7) according to their translating nature or not.

Figure 3a and 3c are two embodiments of the propulsive system where said mountings (5) of both said curved parts (12) of the said endless chain (8) translate independently in the direction of the straight part (9) of the said endless path (6). This said translation of the said curved parts (12) of the endless path (6) accommodates cumulative changes in length of the said chain (8), the function and importance of which has been described previously. In Figure 3a a wheel is utilised to realise the guiding function of the said chain (8) in the curved parts (12) of said endless path (6). In Figure 3c a linear sliding system is utilised to realise the guiding function of the said chain (8) in the curved parts (12) of said endless path (6).

Figure 3b and 3d are the equivalents of Figure 3a and figure 3c in case only one curved part (12) of the endless path (6) translates. Figure 4a and 4b are partial bottom views of an embodiment of the invention that show how actuation of the said endless chain (8) is done on two said straight parts (9) of the said endless path (6) by electromagnetic means. The function and importance of driving the said endless chain (8) on the straight part of the said endless path (6) has been explained earlier in the text, and includes reduction of dynamic loading of the chain and reduction of forces at the end-turns.

Figure 4a specifically shows coils (17) that create the necessary variable magnetic field to actuate magnets (16) fixed as seen in figure 4b on the said segments (7) of the said endless chain (8). As is usual in electric machines, the permanent magnets (16) fixed on said segments (7) have alternating orientation as symbolised by the alternating black and white colours.

Figures 5a, 5b, 5c, 5d are partial bottom views of an embodiment of the invention that show how actuation of the said endless chain (8) is done on one or two said straight parts (9) of the said endless path (6) by means of a rack and pinion connection from a near vertical or near horizontal shaft. The function and importance of driving the said endless chain (8) on the straight part of the said endless path (6) has been explained earlier in the text, and includes reduction of dynamic loading of the chain and reduction of forces at the end-turns. Figures 5a and 5c show embodiments where a single pinion (18) engages the racks (19) connected to the said segments (7) of the said endless chain that drives and at least partially guides the said propulsive means. Fig 5a also outlines where and how adequate guiding by common means in the art could be positioned to achieve the desired positioning accuracy in any embodiment containing a rack and pinion transmission between a main source of mechanical power and the said endless chain. Fig 5a illustrates an embodiment where the driving shaft would be vertical.

Fig 5c specifically shows an embodiment where the driving shaft is near- horizontal as in common in a marine environment.

Fig 5b and 5d show embodiments where two single pinions (18) engage the racks (19) connected to the said segments (7) of the said endless chain at two different straight parts of the said endless path (6), and where these pinions connect to a single near horizontal shaft through a gear-box. In one embodiment of this solution where the connection between the said pinions (18) to the said single input shaft is without substantial angular elasticity or play, the position of most said segments (7) of the said endless chain (8) are de- termined, and rigidly connected mountings (5) to guide the segments (7) on the curved parts of the said path (6) could be left to translate freely in the direction of the straight part of the path.

Figures 6 a and 6b are partial bottom views of an embodiment of the invention that show how actuation of the said endless chain (8) is done on one or two said straight parts (9) of the said endless path (6) by means of a spindle drive connecting a near horizontal driving shaft to a spindle (13) that drives open nuts (14) connected to the said segments (7) of the said endless chain. The function and importance of driving the said endless chain (8) on the straight part of the said endless path (6) has been explained earlier in the text, and includes reduction of dynamic loading of the chain and reduction of forces at the end-turns.

Fig 6b shows an embodiment where two spindles (13) engage the said open nuts (14) connected to the said segments (7) of the said endless chain on two different straight parts of the said path (6), and where these said spindles (13) connect to a single near horizontal shaft through a gear-box. In one embodiment of this solution where the connection between the said spindles (13) to the said single input shaft is without substantial angular elasticity or play, the position of most said segments (7) of the endless said chain (8) are deter- mined on the said path (6), and rigidly connected mountings (5) to guide the said segments (7) on the curved parts of the said path (6) could be left to translate freely in the direction of the straight part of the said path (6).

Fig 7a and 7b show a front view of the spindle-nut connection of some embodiments according to figs 6a and 6b, where a said spindle (13) engages the nut (14) composed of conformal surfaces (15) flexibly connected to the said chain segments (7). This arrangement offers the advantage of requiring much lower positioning precision between the said spindle (13) and the nut (14). The conformal surfaces (15) adjust their orientation as needed and share the load through elasticity, thereby providing reliable operation. Fig 8a, 8b, and 8c are partial detailed perspective views of an embodiment of the invention according to drawings 1 , 2, 3d, 6b, 7a, 7b.

Fig 8a shows a complete view of the said propulsive system excluding the outside covers and excluding part of the system of rotational control of the said propulsive means (4). The said endless chain (8) that drives and in case completely guides the propulsive foils (4) is visible, as are the two spindles (13) that drive the chain.

Fig 8b shows a partial view where two said chain elements (7) guiding and driving propulsive means (4) are present and rotatably connected on the said endless path. The said mountings (5) and (1 1 ) that guide the said chain along the said endless path are visible, as are the means the reduce friction, in this case the dark wheels. The elements of said nut (14), fixed on the said segment (7) that engages the said spindles (13) are visible.

Fig 8c shows a partial view of a single said chain element (7) and the said propulsive foil (4) connected to it. The said conformal flexibly mounted sur- faces (15) of the said nut are visible as are many details of the structure and mountings of the chain segment in that embodiment, including the spindle control of the rotational angle of the propulsive foil (4), and means to avoid friction between the said chain segment and the said endless path.

Claims

A maritime vessel (1 ) including at least one volume (2) configured to be at least partially submerged, said volume (2) having at least one opening (3) and said volume (2) at least partially accommodate a propulsive system including rotatable propulsive means (4) configured to extend at least partially through said at least one opening (3), said propulsive means (4) is configured for translation along an endless path (6), where said endless path (6) includes at least two elongated and substantially straight parts (9) of which at least two are oriented substantially perpendicular to an external flow of water surrounding said volume (2) in the vicinity of said at least one opening (3), said endless path (6) further include at least two curved parts (12) configured to join said straight parts (9) such that said path (6) become endless, said propulsive system further includes a number of translating segments (7) arranged along said endless path (6), said translating segments (7) are arranged to receive mechanical power mechanical power from a source of mechanical power, characterised in that at least one of said segments (7) contains or at least partially guides at least one of said propulsive means (4), and in that a number of said segments (7) is rotatably linked together to form at least one endless chain (8) that drives said propulsive means (4).

2. A maritime vessel according to claim 1 , wherein said propulsive system further includes at least one source of mechanical power and mountings (1 1) to guide said at least one endless chain (8) to move along said at least one straight part (9) of said endless path (6) and mountings (5) to guide said endless chain (8) to move along at least said curved path (12) of said endless path (6) characterised in that at least part of said mechanical power is transmitted to said segment (7) during its transiting on one of said substantially straight parts (9) of the endless path (6), where said segment (7) further transmits a part of said received power to the rest of said endless chain (8).

A maritime vessel according to claim 2, wherein at least a number of said connected mountings (5) for a said curved part (12) of the said endless path (6) translate in a direction substantially parallel to at least one of said substantially straight parts (9) of the said endless path (6), and thereby accommodate the length variations of said endless chain (8) caused by polygoning, wear, thermal expansion, elasticity of components under strain or manufacturing inaccuracy.

A maritime vessel according to claim 2, wherein at least a part of said mechanical power originating from at least one of said source of mechanical power is transmitted simultaneously to at least two of said segments (7) each transiting on two distinct and substantially straight parts (9) of the same said endless path (6), where said segments (7) further are transmitting part of said received power to the rest of said endless chain (8).

A maritime vessel according to claim 4, wherein at least a part of said mountings (5), for at least two distinct curved parts of said endless path (6) of said chain (8), translate in a direction substantially parallel to at least one of said substantially straight parts (9) of said endless path (6) to accommodate for variations in length of said endless chain (8) caused by polygoning, thermal expansion, wear, elasticity of components under strain or manufacturing inaccuracy.

A maritime vessel according to any one or more of the claims 2, 3, 4 or 5, wherein said at least one source of mechanical power is electromagnetic and includes permanent magnets (16) conveniently attached to at least a number of said segments (7) in patterns configured to limit mechanical vibrations, where a source of electromagnetic mechanical power includes isolated electrically conducting coils (17) distributed in a static part of said propulsive system facing one or more of said substantially straight parts (9) of said endless path (6) of said chain (8), where said coils (17) are arranged in a convenient way to enable proper control and efficiency of the propulsion force at the desired number of phases and at the desired voltage.

A maritime vessel according to any one or more of the claims 2, 3, 4 or 5, wherein the said at least one source of mechanical power is a rotating pinion (18) configured for engaging a continuous succession of racks (19) connected to said segments (7) in a convenient manner, where said racks (19) are guided at the location of said pinion (18).

A maritime vessel according to any one or more of the claims 2, 3, 4 or 5, wherein said at least one source of mechanical power is a rotating spindle (13) with a rotation axis oriented substantially parallel to said substantially straight parts (9) of the said endless path (6), said rotating spindle (13) is configured to engage an angular section of a nut (14) made of conformal surfaces (15) conveniently connected to said segments (7) of said endless chain (8).

A maritime vessel according to claim 8, wherein said conformal surfaces (15) are elastically connected through springs or equivalent to said segment (7) to enable adequate self-alignment and to enable load distribution across several conformal surfaces and more than one of said segment (7) all driven by said spindle (13).