DRIVE MECHANISM FOR A FLUKE DRIVE AND METHOD FOR INSTALLNING THE SAME

Abstract

A drive mechanism and a method for installing a drive mechanism for a fluke drive. The drive mechanism converts rotary movement into pivoting movement, and includes a first part, a second part having second-part engagement means, a third part having third-part engagement means; and a rod part having a first and a second end. The second part is rotatable in relation to the first part along a rotary axis which is common to the first part and the second part. The third part is reciprocatingly pivotable in relation to the first part about a first pivot axis which is not the same as the rotary axis. The first pivot axis is fixed in relation to the first part. The second-part engagement means is arranged eccentrically with respect to the rotary axis. The first end engages with the second-part engagement means. The second end engages with the third-part engagement means.

Claims

1. A drive mechanism for a fluke drive, the drive mechanism being arranged to convert a rotary movement into a pivoting movement, the drive mechanism, comprising: a first part; a second part comprising a second-part engagement means; a third part comprising a third-part engagement means; and a rod part comprising a first end and a second end, wherein the second part is rotatable in relation to the first part along a rotary axis that is common to the first part and the second part, wherein the third part is reciprocatingly pivotable in relation to the first part about a first pivot axis that is not parallel to the rotary axis, wherein the first pivot axis is fixed in relation to the first part, wherein the second-part engagement means is arranged eccentrically with respect to the rotary axis, wherein the first end engages with the second-part engagement means, wherein the second end engages with the third-part engagement means, and wherein the third-part engagement means is pivotally connected to the second end so that the second end can pivot in relation to the third part about a second pivot axis, the second pivot axis being perpendicular to the first pivot axis.

2. The drive mechanism of claim 1, wherein: the first part is fixed to the hull of a vessel.

3. The drive mechanism of claim 2, wherein: the first part is pivotable in relation to the hull of the vessel about the rotary axis.

4. The drive mechanism of claim 1, wherein: the rotary axis is a main axial direction of a propeller axle of a vessel.

5. The drive mechanism of claim 1, wherein: the rotary axis is the main axial direction of a drive axle being connected via a coupling to a propeller axle of a vessel.

6. The drive mechanism of claim 4, wherein: the second part is directly or indirectly connected to the propeller axle so that the second part rotates with the propeller axle.

7. The drive mechanism of claim 1, wherein: the third part is pivotally connected to the first part, allowing the third part to pivot in relation to the first part about the first pivot axis.

8. The drive mechanism of claim 1, wherein: the second-part engagement means comprises a socket for receiving the first end, the socket having a main longitudinal direction which is slanted in relation to the rotary axis.

9. The drive mechanism of claim 1, wherein: the third-part engagement means is pivotally connected to the second end via a second rotary bearing.

10. The drive mechanism of claim 1, wherein: the rod part has a main direction of elongation being set at an angle in relation to the rotary axis of at least 8 degrees.

11. The drive mechanism of claim 10, wherein: the rod part has a main direction of elongation being set at an angle in relation to the rotary axis of between 10 and 60 degrees.

12. The drive mechanism of claim 1, wherein: the third part is connected to a fluke.

13. The drive mechanism of claim 12, wherein: the third part is connected to the fluke via a flexible element comprising a flexible material body, allowing the fluke to pivot in relation to the fluke rod due to the resilience of the flexible material body.

14. The drive mechanism of claim 13, wherein: the flexible material body is dimensioned so that a plane of the fluke is parallel to the rotary axis, within +/10 degrees, when the fluke is driven in water and when the fluke rod is at its maximum/minimum full amplitude pivot position during use at a set cruise operation rotary speed of the rotary axis.

15. A method for installing the drive mechanism of claim 1, the method comprising: providing a vessel having a propeller axle; and mounting the first part to a hull of the vessel and the second part to the propeller axle.

16. The method of claim 15, further comprising: selecting a flexible material body interconnecting a fluke rod to a fluke of the drive mechanism, the flexible material body being selected with resilient properties so that a main plane of the fluke is parallel to the rotary axis when the fluke is driven in water and when the fluke rod is at its maximum/minimum full amplitude pivot position during use at a set cruise operation rotary speed of the propeller axle.

17. The method of claim 15, wherein: the first part is mounted on the hull so that a fluke rod of the drive mechanism pivots in a vertical plane.

18. The method of claim 15, further comprising: mounting two drive mechanisms according to claim 1 in parallel; and mounting the respective first part on the hull so that a respective fluke rod of the respective drive mechanism pivots in non-parallel planes or counter-pivots in a common pivot plane.

19. The method of claim 15, further comprising: connecting the second part to a pivotable drive axle being connected via a coupling to the propeller axle; and providing the first part with a steering mechanism, arranged to pivot the pivotable drive axle in a horizontal plane.

20. The method of claim 15, wherein: the installing of the drive mechanism is a retrofitting of the drive mechanism, wherein the vessel is an already-existing vessel and the propeller axle is an already-existing propeller axle of the vessel, and wherein the method further comprises: installing the drive mechanism onto the propeller axle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0028] FIG. 1 is a perspective view of a drive mechanism comprising a converter, in accordance with some embodiments.

[0029] FIG. 2 is a perspective detail view of the converter of FIG. 1 from a different angle, in accordance with some embodiments.

[0030] FIG. 3 is a perspective detail view the converter of FIG. 1 from yet another different angle, in accordance with some embodiments.

[0031] FIG. 4 is a partly removed cross-sectional perspective detail view of the converter shown in FIG. 1.

[0032] FIG. 5 is a partly removed cross-sectional perspective detail view of the converter shown in FIG. 1.

[0033] FIG. 6 is another partly removed cross-sectional perspective detail view of the converter shown in FIG. 1.

[0034] FIG. 7 is a perspective detail view of a flexible element, in accordance with some embodiments.

[0035] FIG. 8 is a partly removed cross-sectional perspective detail view of the flexible element shown in FIG. 2.

[0036] FIG. 9 is a simplified side view of a vessel and a drive mechanism, the drive mechanism being in a first position.

[0037] FIG. 10 is the simplified side view of a vessel and a drive mechanism of FIG. 9, wherein the drive mechanism is in a second position.

[0038] FIG. 11 is the simplified side view of a vessel and a drive mechanism of FIG. 9, wherein the drive mechanism is in a third position.

[0039] FIG. 12 is the simplified side view of a vessel and a drive mechanism of FIG. 9, wherein the drive mechanism is in a fourth position.

[0040] FIG. 13 is a simplified top view of a vessel and a drive mechanism having a steering mechanism, in accordance with some embodiments.

[0041] FIG. 14 is a simplified top view of a vessel and three parallel drive mechanisms, in accordance with some embodiments.

[0042] FIG. 15 is a flowchart illustrating a method, in accordance with some embodiments.

DETAILED DESCRIPTION

[0043] As is shown in FIG. 1, in one embodiment, the present invention relates to a drive mechanism 102 for a fluke drive. The drive mechanism 102 is arranged to convert a rotary movement, such as coming from a propeller axle 902 (see FIG. 9) into a pivoting movement, such as of a fluke 110, which can be a flexible fluke 110. The conversion can take place along the same main axis.

[0044] For achieving this conversion, the drive mechanism 102 comprises a converter 122. The converter 122, in turn, comprises a first part 104, a second part 202 and a third part 120.

[0045] It is noted that the details of the drive mechanism 102 illustrated in the Figures are exemplary, and that the converter 122 can be implemented also together with other mechanisms for transferring the resulting pivoting movement to a fluke 110.

[0046] Furthermore, in the example shown in the Figures, the first part 104 is fastened, or arranged to be fastened, to a structure, such as a fixed structure or to the hull 906 of a vessel 904 (see FIG. 9), whereas the third part 120 is fixedly fastened, or arranged to be fixedly fastened, to the fluke rod 106 or the fluke 110. Hence, the third part 120 can be connected directly or indirectly to the fluke 110, such as indirectly connected via the fluke rod 106.

[0047] This means that the second part 202 rotates whereas the third part 120 instead pivots. It is, however, realised that it would be possible to provide the converter 122 so that a pivoting second part 202 would instead be correspondingly connected to the fluke rod 106 or the fluke 110, whereas a rotating third part 120 would be correspondingly connected to said structure. In the latter case, the first part 104 would be coaxial with the second part 202 just like in the first case, but then also pivot together with the fluke rod 106. In the following, the converter 122 will, for clarity, be described in the former configuration which is shown in the Figures, but it is realised that the corresponding applies in case the second part 202 and the third part 120 are switched.

[0048] The fastening to the structure can be a rigid or a non-rigid (such as pivotal) fastening to the structure.

[0049] FIG. 2 is a detailed view of the converter 122 from the above and from the side where the propeller axle 902 enters into engagement with the converter 122.

[0050] FIG. 3 is a different detailed view from a perspective roughly opposite to that shown in FIG. 2.

[0051] As is perhaps most clearly shown in FIG. 4, which is a partly removed cross-sectional side view of the converter 122, the second part 202 comprises a second-part engagement means and the third part 120 comprises a third-part engagement means 416.

[0052] Moreover, the converter 122 comprises a rod part 402, for instance in the form of an elongated stiff part arranged to transfer at least compressive and shear forces along and perpendicular to its length.

[0053] The rod part 402 in turn comprises a first end 404, arranged to engage with the second-part engagement means 414, and a second end 406, arranged to engage with the third-part engagement means 416.

[0054] The second part 202 is rotatable in relation to the first part 104 along a rotary axis 112 (see FIG. 1). The rotary axis 112 is common to the first part 104 and the second part 202.

[0055] In contrast thereto, the third part 120 is reciprocatingly pivotable, that is pivotable back and forth on either pivotal side of a pivotal center orientation, in relation to the first part 104. The pivoting occurs about a first pivot axis 116 (again, see FIG. 1). The first pivot axis 116 is not the same as, in other words does not coincide with, the rotary axis 112. In some embodiments, the first pivot axis 116 is not parallel with and/or does not intersect the rotary axis 112. Said pivoting can be arranged to take place only in a pivot plane, which may be vertical, horizontal or inclined.

[0056] As is illustrated in the Figures, the first pivot axis 116 is fixed in relation to the first part 104, such as defined by one or several cooperating pivot points on the first part 104. In other words, the third part 120 can be pivotally connected, via such one or several cooperating pivot points, to the first part 104. When the first part 104 is fastened to said structure, it will then define the first pivot axis 116 in relation to the structure. In case the first part 104 is rigidly connected to the structure, the first pivot axis 116 will also be rigid in relation to the structure, but if the first part 104 is movable (such as pivotally fastened) in relation to the structure, the first pivot axis 116 will be correspondingly movable in relation to the structure.

[0057] Hence, the third part 120 can be pivotally connected to the first part 104, allowing the third part 120 to pivot in relation to the first part 104 about the first pivot axis 116. This pivoting can be defined by said one or several pivot points. The pivot points may in turn be defined by one or several first rotary bearings 302. As is shown in the Figures, the pivot points can comprise two first rotary bearings 302 arranged along said first pivot axis 116, such as on or at opposite external side walls of the first part 104.

[0058] In the embodiments shown in FIG. 1, the first part 104 is fastened to the structure in an orientation so that the fluke 110 pivots upwards and downwards, along a vertical pivot plane. It is, however, realized that the first part 104 can instead be fastened to the structure in an orientation such that the fluke 110 pivots from side to side along a horizontal pivot plane; or the pivot plane can slant. In some embodiments, the first part 104 is pivotally fastened in relation to the structure, such that it can pivot about the rotary axis 112. Then, the pivot plane can be dynamically adjusted (rotated), such as in response to varying modes of operation or operation conditions.

[0059] As is best seen in FIG. 4, the second-part engagement means 414 is arranged on the second part 202 eccentrically with respect to the rotary axis 112. In other words, the second part 202 rotates with the propeller axle 902 and as a result the second-part engagement means 414 rotates along with the rest of the second part 202. As the second-part engagement means 414 is eccentrically arranged on the second part 202 in relation to the rotary axis 112, the second-part engagement means 414 will describe a circular movement path about the rotary axis 112. Since the first end 404 of the rod part 402 engages with the second-part engagement means 414, the first end 404 is also forced to describe such circular movement path. The radial distance of the second-part engagement means 414 from a centre of rotation of the second part 202 can be at least 5 cm, and in some cases much more for large ships and the like.

[0060] The second part 202 can be rigidly connected to the propeller axle 902, such as via a screw joint or other suitable joining means.

[0061] In some embodiments, the rotary axis 112 is the main axial direction of the propeller axle 902 of the vessel 904. The vessel 904 may be an already-existing vessel 904 having an already-existing propeller axle 902, and the drive mechanism 102 can then be a retrofitting of the drive mechanism 102, such as for converting an existing propeller drive into a fluke drive. In such cases, a gear box can be added between the propeller axle 902 and the drive mechanism 102, even if a length of the fluke rod 106 and/or a property (such as a size, a shape and/or a resilience) of the fluke 110 can instead be adapted so that desired operation properties are achieved without using a gear box but instead connecting the propeller axle 902 directly to the first part 104.

[0062] As is understood from the above, the second part 202 can be directly or indirectly connected to the propeller axle 902 so that the second part 202 rotates with the propeller axle 902 and in turn drives the first end 404 of the rod part 402 along said eccentric circular path.

[0063] The second-part engagement means 414 can comprise a socket 410 for receiving the first end 404 of the rod part 402. In such cases, the socket 410 has a main longitudinal direction which is slanted in relation to the rotary axis 112, and that can be roughly or completely parallel to a main longitudinal direction of the rod part 402.

[0064] The socket 410 and the first end 404 can hence comprise cooperating engagement means, that can comprise a third rotary bearing 412 allowing the rod part 402 to rotate about its longitudinal direction in relation to the socket 410. This is illustrated in FIG. 4. However, since the rod part 402 and the socket 410 will be in the same relative angular orientation in relation one to the other as the second part 202 rotates about the rotary axis 112, the first end 404 can alternatively simply rest in the socket 410 in an engagement allowing the rod part 402 to rotate about its longitudinal direction in relation to the socket 410. The second end 406 can then be fastened to the third part 120 in a way not allowing any rotating about the longitudinal direction of the rod part 402 in relation to the third part 120. Alternatively, the second end 406 can engage with the third part 120 in a corresponding way allowing such relative rotation whereas the first end 404 is rigidly connected to the second part 202. In yet further alternative embodiments, both the first end 404 and the second end 406 can engage with the second part 202 and the third part 120, respectively, in a way allowing such rotary movement about the longitudinal direction of the rod part 402. It is also possible that the rod part 402 engages in a way not allowing such relative rotation at either of the first end 404 and the second end 406, but that the rod part 402 instead comprises two parts that are connected one to the other in a way allowing them to rotate relative to each other about the longitudinal direction of the rod part 402 whereas the first end 404 and the second end 406, being formed at either of said two parts of the rod part 402, are connected to the second part 202 and the third part 120, respectively, in a way not allowing such relative rotation.

[0065] Even in case the first end 404 and/or the second end 406 of the rod part 402 simply rests in a respective socket 410 (of the second part 202 and/or the third part 120, respectively), the rod part 402 can be kept in place between the second part 202 and the third part 120 by the second-part engagement means 414 of the second part 202 and the third-part engagement means 416 of the third part 120; by the first part 104 and the third part 120 being kept together by said pivotal connection; and ny the first part 104 keeping the second part 202 in axial position (with respect to the rotary axis 112) in relation to the third part 120. In order to guarantee the latter axial position, the first part 104 can comprise a shoulder 418 or similar means to limit the rotary axis 112 axial freedom of movement of the second part 202 in relation to the third part 120. The first part 104 can also comprise an axially extending cavity in which the second part 202 is accommodated, allowing it to rotate but not move radially in relation to the rotary axis 112. As shown in FIG. 2, the second part 202 may engage with the first part 104 via an axle bearing 204.

[0066] As is furthermore best understood from FIG. 4, FIG. 5 and FIG. 6, the third-part engagement means 416 can be pivotally connected to the second end 406 of the rod part 402. It is noted that this pivotal connection may not allow rotating of the rod part 402 about its longitudinal direction, but instead only allow pivoting in a pivot plane to which said longitudinal direction is parallel or roughly parallel. The pivotal connection may be embodied via a second rotary bearing 408, being arranged so that the second end 406 can pivot in relation to the third part 120 about a second pivot axis 118. The second pivot axis 118 can be perpendicular to the first pivot axis 116.

[0067] In a way corresponding to the pivot points defining the first pivot axis 116 as described above, the second pivot axis 118 can be defined by cooperating pivot points arranged on the rod part and the third part 120, restricting their relative freedom of movement to said pivoting about the second pivot axis 118. Hence, the rod part 402 can have a pair of legs at the second end 406, each leg connecting to a respective one of said pivot points on the third part 120, said pivot points i turn defining the second pivot axis 118.

[0068] This way, the relative pivoting of the rod part 402 in relation to the third part 120 allows the first end 404 of the rod part 402 to describe said circular eccentric path while its second end 406 instead moves up and down so as to drive the third part 120 to pivot in said pivot plane as described above, to drive the fluke 110 up or down, or back and forth, as the case may be.

[0069] The second-part engagement means 414 can be arranged to keep the relative angle between the second part 202 and the longitudinal direction of the rod part 402 fixed, whereas the third-part engagement means 416 can be arranged to keep the relative angle between the third part 120 and the longitudinal direction of the rod part 402 fixed save for the pivoting about the second pivot axis 118.

[0070] The rod part 402 can have a main direction of elongation being set at a relative angle in relation to the rotary axis 112 of at least 8, such as at least 10, such as at least 12. The rod part 402 can have a main direction of elongation being set at a relative angle in relation to the rotary axis 112 of between 10 and 60, such as between 10 and 30, such as between 12 and 24. This angle between said main direction of elongation of the rod part 402 and the rotary axis 112 can be fixed and constant, and can be defined by the relative position and orientation of the second-part engagement means 414 and the third-part engagement means 416.

[0071] In the cross-sectional view of FIG. 5, the removed cross-section is vertical, and hence perpendicular to the rotary axis 112.

[0072] The cross-sectional view of FIG. 6 is similar to that of FIG. 5, but with the removed vertical cross-section slightly offset away from the fluke 110, allowing the second-part engagement means 414 to be more clearly visible.

[0073] FIG. 7 shows the flexible element 108 in closer detail.

[0074] As mentioned above, the third part 120 can be directly connected to the fluke 110 (or indirectly connected to the fluke 110 via the fluke rod 106), the direct or indirect connection being via the flexible element 108. Preferably, the flexible element 108 is directly connected to the fluke 110, such as to an internal supporting structure of the fluke 110. It is noted that as the term is used herein, the flexible element 108 can mediate a direct connection even if the two connected parts are in fact physically separated by the flexible element 108. Hence, the flexible element 108 can be seen as primarily a fastening means rather than a distance element.

[0075] The flexible element 108 can comprise a flexible material body, such as a polyurethane body 114, arranged to allow the fluke 110 to pivot, such as in relation to the third part 120 and/or to the fluke rod 106, due to the resilience of the flexible material body, as the third part 120 pivots in turn, as a result of the rotation of the second part 202 about the rotary axis 112, a rotation that in turn can be caused by rotation of the propeller axle 902. It is noted that this pivoting of the fluke 110 takes place by the inertia of the fluke itself as the third part 120 pivots, and further by the fluid resistance of a medium through which the fluke 110 moves. In preferred cases, the fluke 110 is completely immersed into water during operation.

[0076] In the following, the flexible material body will be described in terms of it being a polyurethane body, in other words a piece of polyurethane material forming the flexible material body. Polyurethane is a suitable choice of material, since it can be made to withstand harsh conditions underwater for prolonged use, and since it can be made to maintain desirable elastic properties. However, it is understood that other materials can also be used, in particular polymeric materials such as various plastic materials. Materials that degrade in water, in particular salt water, may be less desirable. For instance, rubber is not always a suitable choice for the flexible material body. Hence, what is said in the following regarding the polyurethane body is generally applicable to flexible material bodies of other materials.

[0077] As is clear from the partly removed cross-section shown in FIG. 8, the polyurethane body 114 can be cast directly onto the fluke rod 106 (or the third part 120, as the case may be) and to a fastening means 702 of the fluke 110 so as to resiliently connect the fluke rod 106 (or the third part 120) and the fastening means 702 of the fluke rod to each other.

[0078] As seen in FIG. 8, the respective connections can comprise a respective flange part (of the interconnected parts in question) being cast into, and completely immersed in, the polyurethane material of the polyurethane body 114. For instance, the flanges can be blasted and primed, after which the polyurethane is cast directly, as one body of polyurethane material, around the flange in question.

[0079] The fluke rod 106 or third part 120 can be interconnected, inside and through the polyurethane body 114, to the fluke 110 via a link, such as a flexible metal joint. This is, however, not necessary, and the fluke rod 106 or third part 120 can lack any connection to the fluke 110, apart from the polyurethane body 114 and possibly any electric wires or similar for any control of the fluke 110.

[0080] The polyurethane body 114 is preferably manufactured as a solid piece of polyurethane material, such as by casting such a solid piece of material. The piece of polyurethane material can be a homogenous and single connected material body.

[0081] FIG. 9-FIG. 12 is a sequence, showing the drive mechanism 102 and the fluke 110 at four different stages as the second part 202 of the drive mechanism 102 moves one full rotary revolution of 360. In FIG. 9, the fluke rod 106 (and the fluke 110) is in its lowermost position (minimum full pivot amplitude position in the pivot plane), and the fluke rod 106 is not moving. In FIG. 10, the fluke rod 106 is halfway between the lowermost position moving upwards, at peak pivot speed, towards an upwards-most position (maximum full pivot amplitude position) shown in FIG. 11. In FIG. 12, the fluke rod 106 has moved halfway from its uppermost position back towards the lowermost position.

[0082] As can be seen in FIG. 10 and FIG. 12, the fluke 110 bends (pivots) upwards during its transition downwards, due to the fluid resistance and the inertia of the fluke 110 itself; and the fluke 110 correspondingly bends (pivots) downwards during its transition upwards. The corresponding is of course true in case the pivot plane is not vertical.

[0083] In some embodiments, the polyurethane body 114 is dimensioned so that a main plane of extension of the fluke 110 is parallel to the rotary axis 112 when the fluke 110 is driven in water as the fluid and when the fluke rod 106 is at its maximum and/or minimum full amplitude pivot position during use at a set cruise operation rotary speed of the rotary axis.

[0084] In other words, the polyurethane body 114 is dimensioned, for a particular drive mechanism 102, a particular fluke 110 and a particular cruise operation rotary speed (such as a desired cruise speed of a boat to be propelled using the fluke 110 and the drive mechanism 102) so that the fluke 110 has time to pivot upwards, in connection to the reaching by the fluke rod 106 of its top turning point, so that a rotary axis 112 parallel orientation is temporarily assumed before the fluke 110 is again pulled downwards by the fluke rod 106 again pivoting downwards; and/or corresponding for the lowermost turning point.

[0085] In particular for the propulsion of boats and other floating vessels, the present inventors have discovered that arranging the drive mechanism so that the main plane of extension of the fluke 110 assumes a horizontal position, or at least an approximately horizontal position, at the uppermost position of the fluke rod 106, and possibly also at the lowermost position of the fluke rod 106, provides a very efficient drive of the vessel in question in a forwards direction of the vessel.

[0086] It is acceptable for the fluke 110 to assume said parallel orientation, as an extreme orientation of the fluke 110, at or in connection to the uppermost and/or lowermost positions fo the fluke rod 106 within +/10, more preferably +/5. Again, the corresponding applies throughout such embodiments for non-vertical pivot planes (for instance, for a horizontal pivot plane the orientation of the fluke at its turning points will in some embodiments be vertical +/) 5.

[0087] The polyurethane material can have a Shore A hardness of between 40 and 100, such as between 60 and 100, such as between 80 and 90. The stronger the moment transferred via the propeller axle 902 the higher the hardness is generally required for the polyurethane material, even if the dimensioning of the flexible element 108, the length of the fluke rod 106 and other factors of course also affects the movement of the fluke 110.

[0088] In these and other embodiments, the fluke rod 106 can be arranged to describe a pivoting action within said pivot plane, where the pivot action has an angular pivot amplitude of at least 8, such as at least 10, such as at least 12, as the second part 202 performs a full rotary revolution about the rotary axis 112. The pivot amplitude may be between 10 and 60, such as between 10 and 30, such as between 12 and 24. This means that the flexible element 108 should be dimensioned and selected so as to allow a corresponding bending of the fluke 110 in relation to the fluke rod 106 given the moment available via the propeller axle 902 at the selected cruising speed.

[0089] The fluke 110, such as a main plane of a relatively inflexible fluke 110 or an aft-most arranged part of a more flexible fluke 110, can be arranged to pivot between 15 and 50, such as between 20 and 40, in relation to a main longitudinal direction of the fluke rod 106 as the fluke rod 106 performs a full pivotation.

[0090] The flexible element 108 can have any desired shape, such as a cylindrical shape. In FIG. 7, the flexible element 108 is exemplified as having a circular-cylindrical shape. However, the flexible element 108 could also be completely or partly cylindrical with a non-circular cross-section, such as a rectangular cross-section. In some embodiments, the flexible element 108 has a cross-sectional shape corresponding to the fluke rod 106 at the end of the flexible element 108 facing the fluke rod 106 and a cross-sectional shape corresponding to the fluke 110 at the end of the flexible element 108 facing the fluke 110. Between these ends, the flexible element 108 can have a generally smooth surface shape. This is exemplified in FIG. 1 and provides low fluid resistance of the drive mechanism 102.

[0091] As is clear from FIG. 13, a steering mechanism 1308 can be used to control the direction in which the fluke 110 drives the hull 906. Such steering mechanism 1308 can be arranged to control a horizontal such driving direction, which is also the case in the exemplary embodiment shown in FIG. 13.

[0092] The steering mechanism 1308 can comprise a coupling 1304 allowing the converter 122 to swing in a horizontal plane. The corresponding applies if the steering mechanism 1308 is arranged to direct the driving force of the drive mechanism 102 in a non-horizontal plane, as the case may be.

[0093] Concretely, the rotary axis 112 can be the main axial direction of a drive axle 1306 being connected via the coupling 1304 to the propeller axle 902 of the hull 906. The coupling 1304 can be a per se conventional universal joint or similar, arranged to transfer rotary movement across a change in rotary axis direction. The steering mechanism 1308 can be controlled using suitable pneumatic or electric control means in a per se conventional manner.

[0094] FIG. 13 also shows a control device 1302 that can control the steering mechanism 1308 and any other user-settable parts of the drive mechanism 102, such as for instance a user-settable fluke 110 stiffness control. Such a control device 1302 can be used in any embodiment of the present invention.

[0095] FIG. 14 shows the use of several parallel flukes 110 with one single hull 906, in the particular example shown three parallel flukes 110. Each of the flukes 110 is driven by its own drive mechanism 102, where a belt drive 1402 or similar moment transfer device transfers the rotary movement of the propeller axle 902 to respective drive axle 1306 in turn being rigidly connected to of the respective second parts 202 of converters 122 of the respective drive mechanisms 102.

[0096] Hence, this way the same propeller axle 902 can drive more than one fluke 110. Each of the flukes 110 may be pivoted in parallel or non-parallel pivoting planes.

[0097] Irrespectively of if several flukes 110 are driven by one common propeller axle 902 or by one respective propeller axle 902 of the same vessel 904 each, the flukes 110 can be pivoted in individual parallel or non-parallel pivot planes. For instance, two flukes 110 can be pivoted in parallel pivot planes but in opposite directions. In one concrete example, two flukes 110 may be caused to pivot in a common horizontal pivot plane but in counter-cycle so that the two flukes 110 move in a synchronised manner towards and away from each other during the full revolution of their respective second parts 202. Such counter-pivoting may also take place in non-parallel, mutually slanting and symmetric (about a vertical symmetry plan) pivot planes, whereby the flukes 110 move both symmetrically upwards/downwards and towards and away from each other during a full rotary revolution of the second parts 202.

[0098] FIG. 15 shows a method 1500 for installing a drive mechanism 102 of the above-described type.

[0099] In a step 1502, the vessel 904 is provided, the vessel 904 having the propeller axle 902.

[0100] In a subsequent step 1504, a flexible element 108, having a polyurethane body 114, is selected to interconnect the fluke rod 106 to the fluke 110 of the drive mechanism 102, or to connect the fluke 110 directly to the third part 120 as described above. The polyurethane body 114 is selected with resilient properties so that a main plane of extension of the fluke 110 is parallel to the rotary axis 112 when the fluke 110 is driven in water and when the fluke rod 106 is at its maximum/minimum full amplitude pivot position during use at a set cruise operation rotary speed of the propeller axle 902, as has been discussed above. The cruise operation speed preferably corresponds not to a maximum power or speed of the vessel 904, but to a desired normal crusing speed or power of the vessel 904. This means that the fluke 110 may pivot too far up/down if the vessel 904 is driven at higher-than-cruising speeds, and conversely not far up/down enough at sub-cruising speeds. Since operation at cruising speed is optimal, this would in most cases be an acceptable compromise.

[0101] In a subsequent step 1506, the first part 104 is then mounted to the hull 906 of the vessel 904, and the second part 202 is mounted to the propeller axle 902, again in the general way described above. The mounting to the hull 906 may be with bolts or in any other suitable manner.

[0102] Step 1506 can comprise mounting the first part 104 to the hull 906 in a way so that the fluke rod 106 of the drive mechanism 102 pivots in a vertical pivot plane.

[0103] Step 1506 can also comprise mounting two or more drive mechanisms 102 in parallel onto the same vessel 904. Then, the respective first part 104 can be mounted on the hull 906 of the vessel 904 so that a respective fluke rod 106 of the respective drive mechanism 102 pivots in parallel or non-parallel planes, such as counter-pivots in a common pivot plane, as has been discussed above.

[0104] Step 1506 can also comprise connecting the second part 202 to a pivotable drive axle 1306 in turn being connected via the coupling 1304 to the propeller axle 902. Then, the first part 104 can be provided with the steering mechanism 1308, including the control device 1302, as described above, the steering mechanism 1308 in turn possibly being arranged to pivot the pivotable drive axle 1306 in a horizontal plane.

[0105] In some embodiments, the installing of the drive mechanism 102 is a retrofitting of the drive mechanism 102 to an already-existing vessel 904, such vessel 904 having an already-existing propeller axle 902. Then, the drive mechanism 102 can be installed onto the already existing propeller axle 902 for driving of the fluke 110 by the already existing propeller axle 902.

[0106] The converter 122 may in general be encapsulated in a housing, such as a flexible housing, such as a rubber or plastic material housing, which housing may be fluid-tightly mounted on the converter 122 and filled with a lubricant, such as oil.

[0107] The vessel 904 can be a stand-up padel board (a so-called SUP) having a manual propulsion of the propeller axle 902; a small or medium-sized recreational motorboat; a small ship; or even a big ship. The converter 122, the fluke rod 106 and the fluke 110 are then adapted accordingly with respect to resilience, hardness, sturdiness, dimensions and so forth.

[0108] The fluke rod 106 is preferably at least 50 cm long, and longer for larger vessels. The polyurethane body 114 is preferably at least 10 cm long, and again longer for larger vessels. A minimum distance between the fluke rod 106 (or the first part 104) and the fluke 110, the minimum distance being measured through the polyurethane body 114, is preferably at least 5 cm, and again longer for larger vessels.

[0109] The bearings mentioned above can be ball bearings or any other suitable type of bearing, providing low-friction relative rotation.

[0110] All parts of the drive mechanism 102, apart from the polyurethane body 114, may be made from rigid material, such as suitable metal and/or ceramic material, such as stainless steel for structurally supporting parts.

[0111] Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications can be made to the disclosed embodiments without departing from the basic idea of the invention.

[0112] For instance, the properties of the fluke 110 can vary depending on application. For instance, the fluke may be made from a solid piece of elastomeric plastic material and/or comprise reinforcement structures such as metal rods and/or springs.

[0113] The converter 122 can be used with the flexible element 108 described above, but also with other solutions for allowing the fluke 110 to pivot/bend in relation to the third part 120 and/or the fluke rod 106.

[0114] The flexible element 108 can be used with the converter 122 described above, but also with other solutions for transferring the rotary moment available from the propeller axle 902 to a pivoting movement.

[0115] In tests, the present inventors have found very good drive efficiency in drive mechanisms 102 having a converter 122 of the type described herein in combination with a flexible element 108 of the type described herein.

[0116] In general, everything which is said in relation to the drive mechanism 102 is equally applicable to the method, and vice versa.

[0117] Hence, the invention is not limited to the described embodiments, but can be varied within the scope of the enclosed claims.