PROPULSION SYSTEM FOR A MARINE VESSEL AND A USE OF A SLIP CLUTCH ASSEMBLY

Abstract

A propulsion system for a marine vessel is presented. The propulsion system comprising a propulsion unit that is rotatably attached to the marine vessel about an axis, a rotary drive arranged to rotate the propulsion unit about the axis by applying a torque about the axis, and a slip clutch assembly operationally arranged between the propulsion unit and the rotary drive to allow a rotational motion between the propulsion unit and the rotary drive about the axis in case the propulsion unit impacts an obstacle.

Description

TECHNICAL FIELD

The disclosure relates generally to marine propulsion. In particular aspects, the disclosure relates to a propulsion system for a marine vessel and to a use of a slip clutch assembly in marine a propulsion system. The disclosure can e.g. be applied to marine vessels such as powerboats, yachts or sailboats. Although the disclosure may be described with respect to a particular vessel, the disclosure is not restricted to any particular vessel.

BACKGROUND

Marine vessels may be provided with one or more propulsion units to propel the marine vessel in water. There exist various solutions to suspend a propulsion unit, some of which are configured to hinder or at least mitigate the propulsion unit being damaged in case of impact with an obstacle.

Prior art solutions are marred with various drawbacks such as bulky, complex and/or high-cost designs.

SUMMARY

According to a first aspect of the disclosure, there is provided a propulsion system for a marine vessel, the propulsion system comprises a propulsion unit that is rotatably attached to the marine vessel about an axis, a rotary drive arranged to rotate the propulsion unit about the axis by applying a torque about the axis, and a slip clutch assembly operationally arranged between the propulsion unit and the rotary drive to allow a rotational motion between the propulsion unit and the rotary drive about the axis in case the propulsion unit impacts an obstacle.

The first aspect of the disclosure may seek to avoid the propulsion system being damaged in case of impact, for example should the propulsion unit encounter a rock or a floating object. In other words, the propulsion system may be said to comprise a so-called kick-up function, or rotational slip, allowing the propulsion unit to slip in case the propulsion unit impacts an obstacle. The present propulsion system may thereby hinder the marine vessel, typically its transom, from being damaged and in worst case the vessel sinking. Also, the present propulsion system may avoid people getting injured by debris. Another technical benefit is that the propulsion unit may, depending on its size and weight, be manually (not requiring any motor or other drive means) rotated by a person. For example, a relatively small propulsion unit may be manually tilted to avoid damage when trailering. Other technical benefits include that the propulsion unit may be compact, sturdy, low-cost and that the propulsion unit may re-engage after a rotational slip. The slip clutch assembly may be an integral part of other components of the propulsion system, such as a shaft supporting the propulsion unit and the rotary drive.

By the slip clutch assembly being operationally arranged between the propulsion unit and the rotary drive may be meant that the slip clutch assembly may selectively transfer a rotation between the rotary drive and the propulsion unit. Thus, the slip clutch assembly may either transfer a rotation between the rotary drive and the propulsion unit, or not transfer a rotation between the rotary drive and the propulsion unit. In other words, the slip clutch assembly may either allow a rotational motion between the propulsion unit and the rotary drive or not allow such rotational motion. The slip clutch assembly may thus be arranged in an engaged state and in a disengaged state. When the slip clutch assembly is in the engaged state, a rotational motion between the propulsion unit and the rotary drive may not be allowed. When the slip clutch assembly is in the disengaged state, a rotational motion between the propulsion unit and the rotary drive may be allowed.

Optionally, the propulsion system comprises a transom bracket to rotatably attach the propulsion unit to the marine vessel about the axis, the transom bracket being adapted to be secured to the marine vessel. A transom bracket may facilitate mounting the propulsion unit to various vessels.

Optionally, the slip clutch assembly is configured to allow a rotational motion between the propulsion unit and the rotary drive when a torque between the propulsion unit and the rotary drive about the axis exceeds a threshold torque value. A technical benefit may include that the slip clutch assembly may be adapted to provide a tailored threshold torque value. The threshold torque may disengage the slip clutch assembly. Thus, once the slip clutch assembly is subject to the threshold torque, the slip clutch assembly may shift from the engaged state to the disengaged state.

Optionally, the slip clutch assembly is configured to allow a rotational motion along a predetermined slip rotation angle when a torque between the propulsion unit and the rotary drive exceeds a threshold torque value at the beginning of the rotational motion, the slip clutch assembly optionally being configured to allow a stepwise rotational motion along predetermined slip rotation angles. Such a design may facilitate the slip clutch assembly re-engaging after having been disengaged, i.e. after a rotational slip.

Optionally, the propulsion system comprises a shaft to which the propulsion unit is secured, the rotary drive being arranged to rotate the shaft, and thereby the propulsion unit, about the axis. Such a shaft may facilitate integrating the slip clutch assembly into the propulsion system.

Optionally, the slip clutch assembly is formed by the shaft and the rotary drive. Thus, the slip clutch assembly may be an integral part of the shaft and the rotary drive. Such a solution may be particularly compact, require few parts, and be cost effective. The shaft may be arranged inside the rotary drive.

In alternative to the slip clutch assembly being formed by the shaft and the rotary drive, the slip clutch assembly may be provided as a separate part, i.e. a part that is separate from the shaft and/or from the rotary drive.

Optionally, the slip clutch assembly comprises an engaging member and a receiving recess. The engaging member and receiving recess may be engaged or disengaged, i.e. may be in an engaged stage and in a disengaged state. The slip clutch assembly may be configured such that the rotational motion between the propulsion unit and the rotary drive about the axis is allowed when the engaging member and the receiving recess are disengaged, i.e. are in the disengaged state. In the engaged state, the slip clutch assembly may transfer a rotation between the rotary drive and the propulsion unit. A slip clutch assembly that is based on members that physically engage or disengage during operation may be referred to as a mechanical slip clutch assembly.

Optionally, the propulsion system comprises a plurality of engaging members and receiving recesses such that the slip clutch assembly allows a stepwise rotational motion along predetermined slip rotation angles. The plurality of engaging members and receiving recesses may be distanced by the same slip rotation angle. The plurality of engaging members and receiving recesses may be equidistantly distributed along a circumference of the slip clutch assembly.

Optionally, the rotary drive essentially has the shape of a circular cylinder or a conical cylinder. Such a design may be sturdy and cost effective. Optionally, the rotary drive may be essentially disc-shaped.

Optionally, the propulsion system comprises a drive unit arranged to rotate the rotary drive.

Optionally, the drive unit comprises a worm gear and the rotary drive comprises an input interface that is adapted to engage the worm gear. Such a solution may offer an advantageous gear reduction between the drive unit and the rotary drive. Alternatively, the drive unit may be concentric with the rotary drive. The rotary drive may be a part of the drive unit. The rotary drive may be an electric motor that comprises a rotor that is concentric with the rotary drive.

Optionally, the propulsion system comprises an electric trim motor that is arranged to rotate the drive unit. Rotation of the drive unit may cause a rotation of the rotary drive that may cause a trim of the propulsion unit 10, i.e. a rotation of the propulsion unit 10 with respect to the vessel 60.

Optionally, the propulsion unit is rotatably attached to the marine vessel about a trim axis that may be essentially horizontal.

Optionally, the propulsion unit comprises a support part and a thrust part, wherein the thrust part is rotatable with respect to the support part about a steering axis to direct the thrust of the propulsion unit. The steering axis may be essentially vertical when the propulsion unit is operated to propel the vessel.

According to a second aspect of the disclosure, there is provided a use of a slip clutch assembly in a propulsion system for a marine vessel, the propulsion system comprising a propulsion unit that is rotatably connected to the marine vessel, the propulsion system being configured such that the slip clutch assembly allows the propulsion unit to rotate with respect to the marine vessel in case the propulsion unit impacts an obstacle.

Advantages of the second aspect of the disclosure correspond to those of the first aspect. The propulsion system (and the slip clutch assembly) of the second aspect may, but need not, comprise the features of the propulsion system of the first aspect.

According to a further aspect of the disclosure, there is provided a marine vessel comprising the above described propulsion system.

The above aspects, accompanying claims, and/or examples disclosed herein above and later below may be suitably combined with each other as would be apparent to anyone of ordinary skill in the art.

Additional features and advantages are disclosed in the following description, claims, and drawings, and in part will be readily apparent therefrom to those skilled in the art or recognized by practicing the disclosure as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of aspects of the disclosure cited as examples.

FIG. 1 is an exemplary side view of a propulsion system of the present disclosure.

FIG. 2 is an enlarged view of a part of the propulsion system of FIG. 1.

FIG. 3 is a further enlarged view of a part of FIGS. 1 and 2.

DETAILED DESCRIPTION

The detailed description set forth below provides information and examples of the disclosed technology with sufficient detail to enable those skilled in the art to practice the disclosure.

The inventive concept of the present disclosure involves rotatably attaching a propulsion unit to a marine vessel, and utilising a slip clutch assembly to allow the propulsion unit to rotate, or rotationally slip, in case a torque affecting the propulsion unit exceeds a threshold torque value. Such a torque may originate from the propulsion unit impacting an obstacle. The slip clutch assembly thus provides a kick-up function.

Some prior art solutions are based on complex link arrangements that may be relatively fragile, bulky and high-cost in manufacture, assembly and repair. Some such solutions may allow a propulsion unit to move in case of impact, but may not be adapted to re-engage the propulsion unit to make possible a continued operation after impact. Further, some solutions may only allow a very slow raise operation of the propulsion unit, or may encounter problems upon reverse operation of the propulsion unit.

FIGS. 1 to 3 disclose an example of a propulsion system 1 in accordance with a first aspect of the present disclosure. As is illustrated, the propulsion system 1 comprises a propulsion unit 10 that is rotatably attached to the marine vessel 60. The propulsion unit 10 is rotatable around an axis A indicated in FIG. 1. In the present example, the propulsion unit is mounted to a transom of the vessel 60.

The propulsion system 1 comprises a rotary drive 20 arranged to rotate R (indicated in FIG. 1) the propulsion unit 10 about the axis A by applying a torque about the axis A. Thus, the propulsion unit 10 is rotated by means of a torque applied to the propulsion unit 10 via the rotary drive 20.

The propulsion system 1 further comprises a slip clutch assembly 30 operationally arranged between the propulsion unit 10 and the rotary drive 20 to allow a rotational motion R_s between the propulsion unit 10 and the rotary drive 20 about the axis A in case the propulsion unit 10 impacts an obstacle 90 (indicated as a rock in FIG. 1). A rotational motion R_s between the propulsion unit 10 and the rotary drive 20, or rotational slip R_s of the propulsion unit 10, is indicated by the arc-shaped arrow in FIG. 3.

In the present example, the propulsion system comprises a transom bracket 40 to rotatably attach the propulsion unit 10 to the marine vessel 60 about the axis A. The transom bracket 40 may be adapted to be secured to the marine vessel 60 by for example comprising a plurality of through-holes facilitating the transom bracket 40 being bolted to the vessel 60, for example to a transom thereof.

Referring in particular to FIG. 1, the propulsion unit 10 may be rotatable R about the axis A such that the propulsion unit 10 may be raised and lowered. The propulsion unit may also be rotated around the axis A to trim the propulsion unit 10, i.e. to set an optimal angle of the propulsion unit 10 with respect to the vessel 60 during propulsion of the vessel 60. In the present example, the propulsion unit 10 may be raised and lowered, but may not be completely raised out of the water. Still, the propulsion unit 10 may be sufficiently raised to allow for safe propulsion in shallow waters. In other undepicted examples, the propulsion unit may be completely raised out of the water.

The slip clutch assembly 30 may be configured to allow a rotational motion R_s (rotational slip) between the propulsion unit 10 and the rotary drive 20 when a torque between the propulsion unit 10 and the rotary drive 20 about the axis A exceeds a threshold torque value. In a large application, the threshold torque value may be set such that a rotational slip R_s of the propulsion unit 10 only occurs in response to the propulsion unit 10 impacting a stationary object, such as a rock 90, or a heavy object such as a floating log. In a small application, where the propulsion unit 10 has a power of a few kilowatts, the threshold torque value may be set significantly lower, such that a rotational slip R_s of the propulsion unit may be accomplished manually by a person tilting the propulsion unit 10 up to avoid damage when trailering.

Referring in particular to FIG. 2, the slip clutch assembly 30 may be configured to allow a rotational motion R_s along a predetermined slip rotation angle α when a torque between the propulsion unit 10 and the rotary drive 20 exceeds a threshold torque value at the beginning of the rotational motion R_s. In other words, the slip clutch assembly 30 may be configured to allow a stepwise rotational motion R_s.

Thus, the slip clutch assembly 30 may be configured to allow a stepwise rotational motion R_s along predetermined slip rotation angles α. In the disclosed example, the slip rotation angle α is 45 degrees. As is to be apprehended, the slip rotation angle α may for example be 15, 30 or 60 degrees depending on what is suitable for a specific application.

As is best shown in FIGS. 2 and 3, the propulsion system 1 may comprise a shaft 12 to which the propulsion unit 10 is secured, the shaft 12 being rotatably attached to the marine vessel 60 about the axis A. In the present example, the shaft 12 to is rotatably journalled in the transom bracket 40.

Referring to FIG. 1, the rotary drive 20 may be arranged to rotate R the shaft 12, and thereby the propulsion unit 10, about the axis A. As is apprehended, when the shaft 12 is rotated counter-clockwise, the propulsion unit 10 is raised. A small rotational movement of the propulsion unit 10, up to e.g. 10 degrees, may be referred to as a trim movement. A large rotational movement of the propulsion unit 10, of e.g. 45 to 180 degrees, may be referred to as a tilt movement. In the present example, the propulsion system allows for tilting the propulsion unit 10 approximately 90 degrees. It follows that the present propulsion system also allows for trimming the propulsion unit 10.

The present slip clutch assembly 30 is operationally arranged between the shaft 12 and the rotary drive 20, as is best illustrated in FIG. 3. As is shown, the present slip clutch assembly 30 is formed by the shaft 12 and the rotary drive 20. In some detail, the slip clutch assembly 30 comprises an engaging member 24 and a receiving recess 14. The engaging member 24 and the receiving recess 14 may be engaged or disengaged. The slip clutch assembly 30 is configured such that the rotational slip R_s of the propulsion unit 10 is allowed when the engaging member 24 and the receiving recess 14 are disengaged.

With continued reference to FIG. 3 (and as is also shown in FIG. 2), the engaging member 24 may be biased towards the receiving recess 14. As is shown, the engaging member 24 may be comprised in a resilient member 22. In the current example, the resilient member 22 is a cantilever structure that is aligned with the circumference of the rotary drive 20. The outer end of the resilient member 22 comprises the engaging member 24 in the form of a protrusion, or bulge, which protrudes towards the receiving recess 14.

The hollow arrow in FIG. 3 indicates that the resilient member 22 may deform radially outwards such that its engaging member 24 disengages the receiving recess 14. After disengagement, the shaft 12 may rotate with respect to rotary drive 20 to provide the rotational slip R_s. As is to be apprehended, when there is a certain threshold torque between the shaft 12, that supports the propulsion unit 10, and the rotary drive 20, the engaging member 24 will disengage from the receiving recess 14. The threshold torque will cause the shaft 12 to start rotate with respect to the rotary drive 20, and thereby the engaging member 24 will be forced out from the receiving recess 14.

Once the slip clutch assembly 30 is in its disengaged state (the engaging member 24 has disengaged the receiving recess 14), a significantly lower torque than the threshold torque may be required to continue the rotational slip R_s. For this reason, the slip clutch assembly 30 can be said to be configured to allow a rotational motion R_s along a predetermined slip rotation angle α when a torque between the propulsion unit 10 and the rotary drive 20 exceeds a threshold torque value at the beginning of the rotational motion R_s.

As in the current example, there may be provided a plurality of engaging members 24 and receiving recesses 14 such that the slip clutch assembly 30 allows a stepwise rotational motion R_s along predetermined slip rotation angles α.

As is clear from FIG. 2, the plurality of engaging members 24 and receiving recesses 14 that are distributed along a circumference of the slip clutch assembly 30 entail that the rotational slip R_s will continue along the slip rotation angle α until the next engaging member 24 and receiving recess 14 engage. In undepicted embodiments, there may be only one set of engaging member 24 and receiving recess 14, or a greater number of engaging members 24 and receiving recesses 14. Thus, the slip rotation angle α may be customised. As is to be apprehended, if there is only one set of engaging member 24 and receiving recess 14, it may be necessary to rotate either the shaft 12 or the rotary drive 20 to re-engage the slip clutch assembly 30 after a rotational slip R_s.

The threshold torque may be tailored by altering the number of engaging members 24 and receiving recesses 14, their shape and/or the material of the resilient member(s) 22. The present disclosure does not exclude there being different numbers of engaging members 24 and receiving recesses 14.

As is illustrated, the rotary drive 20 and the shaft 12 may be concentric. In undepicted examples, the rotary drive 20 and the shaft 12 may be arranged side by side. It is to be apprehended that the slip clutch assembly 30 need not be a part of the rotary drive 20 and the shaft 12, as is the case in the present example.

Referring to FIGS. 1 and 2, the rotary drive 20 may comprise an input interface 26 that is adapted to engage a drive unit 50 such that the drive unit 50 may rotate the rotary drive 20. As is disclosed, the input interface 26 may be gears, such as spur gears. In the present example, the input interface 26 is realised as teeth arranged around the entire rotary drive 20.

As is shown, the present rotary drive 20 comprises the above-described engaging member 24 that forms part of the slip clutch assembly 30. Further, the shaft 12 comprises the receiving recess 14 that is adapted to cooperate with the engaging member 24. It is to be apprehended that the present disclosure does not exclude the reverse situation, i.e. that the rotary drive 20 comprises the receiving recess 14 and the shaft 12 comprises the engaging member 24.

Thus, the input interface 26 may be arranged on a radially outer surface of the rotary drive rotary drive 20 and the engaging member 24 or receiving recess 14 may be arranged on a radially inner surface of the rotary drive 20. The present rotary drive 20 essentially has the shape of a circular cylinder. The cylinder is provided with the input interface 26 (teeth) on its outer surface and with the engaging member 24 on its inner surface. Since the engaging member 24 is adapted to transfer the rotation from the rotary drive 20 to the propulsion unit 20 (via the shaft 12), the engaging member 24 may be referred to as an output interface.

It is to be apprehended that in alternative examples the rotary drive may be essentially disc-shaped. Such a disc-shaped rotary drive may be positioned radially adjacent a shaft that comprises a disc-shaped radial flange. Resilient members, for examples similar to the ones below, may provide a slip clutch function between the disc-shaped rotary drive and the disc-shaped radial flange of the shaft.

The propulsion system 1 may comprise a drive unit 50 that is arranged to rotate the rotary drive 20. The drive unit 50 may engage the input interface 26 of the rotary drive 20, see FIGS. 1 and 2. In the present example, the drive unit 50 comprises a worm gear and the input interface 26 of the rotary drive 20 is adapted to engage the worm gear. As is shown, the present drive unit 50 is elongated and extends from the vessel 60 to the rotary drive 20 that is positioned aft of the transom of the vessel 60. The distal (here aft) end of the drive unit 50 comprises the worm gear. The proximal (here bow) end of the drive unit 50 is coupled to a merely schematically disclosed electric trim motor 55. The electric trim motor 55 is arranged to rotate the drive unit 50.

As is disclosed in FIG. 1, the propulsion unit 10 is rotatably attached to the marine vessel 60 about a trim axis A that is essentially horizontal. The trim axis A may alternatively be referred to as a tilt axis or a trim and tilt axis.

Referring again to FIG. 1, the propulsion unit 10 may comprise a support part 10a and a thrust part 10b. Typically, the support part 10a is an upper part and the thrust part 10b is a lower part. An electric propulsion motor (not visible) may be arranged inside the thrust part 10b. The thrust part 10b may be rotatable with respect to the support part 10a about a steering axis B to direct the thrust of the propulsion unit 10. Thus, the propulsion unit 10 (the support part 10a and the thrust part 10b) is rotatable about the trim axis A and the thrust part 10b of the propulsion unit 10 is rotatable about the steering axis B. In the present example, the support part 10a is not rotatable about the steering axis B.

It is to be apprehended that the present propulsion system 1 may also find use together with other types of propulsion units 1 that are rotatably attached to a marine vessel. For example, propulsion units that do not comprise a support part 10a and a thrust part 10b that is rotatably suspended for steering purposes.

The propulsion unit may (as disclosed) comprise two propellers that are arranged to rotate in opposite directions, or only one propeller, or another type of propulsion solution such as a waterjet.

The propulsion system may be an electric propulsion system, i.e. the propulsion may be driven by an electric motor (not shown) powered by an on-board battery (not shown). The electric motor may be arranged in the thrust part 10b as described above. However, the present disclosure does not exclude there being a combustion engine that powers a generator driving an electric motor, e.g. arranged in a thrust part. Alternatively, the propulsion system may comprise a combustion engine that is rotatably attached to the marine vessel.

It is to be apprehended that in view of the inventive concept of the present disclosure, in a second aspect the present disclosure relates to a use of a slip clutch assembly 30 in a propulsion system 1 for a marine vessel 60, the propulsion system 1 comprising a propulsion unit 10 that is rotatably connected to the marine vessel 60, the propulsion system 1 being configured such that the slip clutch assembly 30 allows the propulsion unit 10 to rotate with respect to the marine vessel 60 in case the propulsion unit 10 impacts an obstacle 90. The slip clutch assembly 30 may be of the kind described herein, i.e. it may be an integral part of other components of the propulsion system 1, or it may be another kind of slip clutch and for example provided as a separate part.

Also disclosed are examples according to the following clauses:

1. A propulsion system (1) for a marine vessel (60), the propulsion system (1) comprising

• • a propulsion unit (10) that is rotatably attached to the marine vessel (60) about an axis (A),
  • a rotary drive (20) arranged to rotate (R) the propulsion unit (10) about the axis (A) by applying a torque about the axis (A), and
  • a slip clutch assembly (30) operationally arranged between the propulsion unit (10) and the rotary drive (20) to allow a rotational motion (R_s) between the propulsion unit (10) and the rotary drive (20) about the axis (A) in case the propulsion unit (10) impacts an obstacle (90).

2. The propulsion system (1) of clause 1, comprising a transom bracket (40) to rotatably attach the propulsion unit (10) to the marine vessel (60) about the axis (A), the transom bracket (40) being adapted to be secured to the marine vessel (60).

3. The propulsion system (1) of clause 1 or 2, wherein the propulsion unit (10) is rotatable (R) about the axis (A) such that the propulsion unit (10) may be raised and lowered.

4. The propulsion system (1) of clause 3, configured such that the propulsion unit (10) may be raised and lowered, but may not be completely raised out of the water.

5. The propulsion system (1) of any preceding clause, wherein the slip clutch assembly (30) is configured to allow a rotational motion (R_s) between the propulsion unit (10) and the rotary drive (20) when a torque between the propulsion unit (10) and the rotary drive (20) about the axis (A) exceeds a threshold torque value.

6. The propulsion system (1) of any preceding clause, wherein the slip clutch assembly (30) is configured to allow a rotational motion (R_s) along a predetermined slip rotation angle (α) when a torque between the propulsion unit (10) and the rotary drive (20) exceeds a threshold torque value at the beginning of the rotational motion (R_s).

7. The propulsion system (1) of clause 6, wherein the slip rotation angle (α) is 15, 30 or 45 degrees.

8. The propulsion system (1) of clause 6 or 7, wherein the slip clutch assembly (30) is configured to allow a stepwise rotational motion (R_s).

9. The propulsion system (1) of any preceding clause, wherein the slip clutch assembly (30) is configured to allow a stepwise rotational motion (R_s) along predetermined slip rotation angles (α).

10. The propulsion system (1) of any preceding clause, comprising a shaft (12) to which the propulsion unit (10) is secured, the shaft (12) being rotatably attached to the marine vessel (60) about the axis (A).

11. The propulsion system (1) of clause 10, wherein the rotary drive (20) is arranged to rotate (R) the shaft (12), and thereby the propulsion unit (10), about the axis (A).

12. The propulsion system (1) of clause 11, wherein the slip clutch assembly (30) is operationally arranged between the shaft (12) and the rotary drive (20).

13. The propulsion system (1) of clause 12, wherein the slip clutch assembly (30) is formed by the shaft (12) and the rotary drive (20).

14. The propulsion system (1) of clause 12 or 13, wherein the slip clutch assembly (30) comprises an engaging member (24) and a receiving recess (14), which may be engaged or disengaged, and wherein the slip clutch assembly (30) is configured such that the rotational motion (R_s) between the propulsion unit (10) and the rotary drive (20) about the axis (A) is allowed when the engaging member (24) and the receiving recess (14) are disengaged.

15. The propulsion system (1) of clause 14, wherein the engaging member (24) is biased towards the receiving recess (14).

16. The propulsion system (1) of clause 15, wherein the engaging member (24) is comprised in a resilient member (22).

17. The propulsion system (1) according to any of clauses 14 to 16 comprising a plurality of engaging members (24) and receiving recesses (14) such that the slip clutch assembly (30) allows a stepwise rotational motion (R_s) along predetermined slip rotation angles (α).

18. The propulsion system (1) according to any of clauses 10 to 17, wherein the rotary drive (20) and the shaft (12) are concentric.

19. The propulsion system (1) of clause 18, wherein the shaft (12) is arranged inside the rotary drive (20).

20. The propulsion system (1) of any preceding clause, wherein the rotary drive (20) comprises an input interface (26) that is adapted to engage a drive unit (50) such that the drive unit (50) may rotate the rotary drive (20).

21. The propulsion system (1) of clause 20, wherein the rotary drive (20) comprises an engaging member (24) or a receiving recess (14) that forms part of the slip clutch assembly (30).

22. The propulsion system (1) of clause 21, wherein the input interface (26) is arranged on a radially outer surface of the rotary drive (20) and the engaging member (24) or receiving recess (14) is arranged on a radially inner surface of the rotary drive (20).

23. The propulsion system (1) of any preceding clause, wherein the rotary drive (20) essentially has the shape of a circular cylinder.

24. The propulsion system (1) of any preceding clause, comprising a drive unit (50) arranged to rotate the rotary drive (20).

25. The propulsion system (1) of clause 24, wherein the drive unit (50) comprises a worm gear and the rotary drive (20) comprises an input interface (26) that is adapted to engage the worm gear.

26. The propulsion system (1) of clause 24 or 25, comprising an electric trim motor (55) that is arranged to rotate the drive unit (50).

27. The propulsion system (1) of any preceding clause, wherein the propulsion unit (10) is rotatably attached to the marine vessel (60) about a trim axis (A) that is essentially horizontal.

28. The propulsion system (1) of any preceding clause, wherein the slip clutch assembly (30) is a mechanical slip clutch assembly.

29. The propulsion system (1) of any preceding clause, wherein the propulsion unit (10) comprises a support part (10a) and a thrust part (10b), wherein the thrust part (10b) is rotatable with respect to the support part (10a) about a steering axis (B) to direct the thrust of the propulsion unit (10).

30. The propulsion system (1) of any preceding clause, wherein the propulsion unit (10) comprises two propellers that are arranged to rotate in opposite directions.

31. The propulsion system (1) of any preceding clause being an electric propulsion system (1).

32. A marine vessel (60) comprising the propulsion system (1) of any preceding clause.

33. Use of a slip clutch assembly (30) in a propulsion system (1) for a marine vessel (60), the propulsion system (1) comprising a propulsion unit (10) that is rotatably connected to the marine vessel (60), the propulsion system (1) being configured such that the slip clutch assembly (30) allows the propulsion unit (10) to rotate with respect to the marine vessel (60) in case the propulsion unit (10) impacts an obstacle (90).

The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element to another element as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It is to be understood that the present disclosure is not limited to the aspects described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the present disclosure and appended claims. In the drawings and specification, there have been disclosed aspects for purposes of illustration only and not for purposes of limitation, the scope of the inventive concepts being set forth in the following claims.

Claims

1. A propulsion system for a marine vessel, the propulsion system comprising: a propulsion unit that is rotatably attached to the marine vessel about an axis,a rotary drive arranged to rotate the propulsion unit about the axis by applying a torque about the axis, anda slip clutch assembly operationally arranged between the propulsion unit and the rotary drive to allow a rotational motion between the propulsion unit and the rotary drive about the axis in case the propulsion unit impacts an obstacle.

2. The propulsion system of claim 1, comprising a transom bracket to rotatably attach the propulsion unit to the marine vessel about the axis, the transom bracket being adapted to be secured to the marine vessel.

3. The propulsion system of claim 1, wherein the slip clutch assembly is configured to allow a rotational motion between the propulsion unit and the rotary drive when a torque between the propulsion unit and the rotary drive about the axis exceeds a threshold torque value.

4. The propulsion system of claim 1, wherein the slip clutch assembly is configured to allow a rotational motion along a predetermined slip rotation angle when a torque between the propulsion unit and the rotary drive exceeds a threshold torque value at the beginning of the rotational motion, the slip clutch assembly optionally being configured to allow a stepwise rotational motion along predetermined slip rotation angles.

5. The propulsion system of claim 1, comprising a shaft to which the propulsion unit is secured, the rotary drive being arranged to rotate the shaft, and thereby the propulsion unit, about the axis.

6. The propulsion system of claim 5, wherein the slip clutch assembly is formed by the shaft and the rotary drive.

7. The propulsion system of claim 5, wherein the slip clutch assembly is operationally arranged between the shaft and the rotary drive.

8. The propulsion system of claim 1, wherein the slip clutch assembly comprises an engaging member and a receiving recess, which may be engaged or disengaged, and wherein the slip clutch assembly is configured such that the rotational motion between the propulsion unit and the rotary drive about the axis is allowed when the engaging member and the receiving recess are disengaged.

9. The propulsion system of claim 8, wherein the engaging member is biased towards the receiving recess.

10. The propulsion system of claim 8, comprising a plurality of engaging members and receiving recesses such that the slip clutch assembly allows a stepwise rotational motion along predetermined slip rotation angles.

11. The propulsion system of claim 5, wherein the rotary drive and the shaft are concentric.

12. The propulsion system of claim 11, wherein the shaft is arranged inside the rotary drive.

13. The propulsion system of claim 1, wherein the rotary drive comprises an input interface that is adapted to engage a drive unit such that the drive unit may rotate the rotary drive, wherein the rotary drive comprises an engaging member or a receiving recess that forms part of the slip clutch assembly.

14. The propulsion system of claim 1, wherein the rotary drive essentially has the shape of a circular cylinder.

15. The propulsion system of claim 1, comprising a drive unit arranged to rotate the rotary drive.

16. The propulsion system of claim 15, wherein the drive unit comprises a worm gear and the rotary drive comprises an input interface that is adapted to engage the worm gear.

17. The propulsion system of claim 15, comprising an electric trim motor that is arranged to rotate the drive unit.

18. The propulsion system of claim 1, wherein the propulsion unit is rotatably attached to the marine vessel about a trim axis that is essentially horizontal.

19. The propulsion system of claim 1, wherein the propulsion unit comprises a support part and a thrust part, wherein the thrust part is rotatable with respect to the support part about a steering axis to direct the thrust of the propulsion unit.

20. Use of a slip clutch assembly in a propulsion system for a marine vessel, the propulsion system comprising a propulsion unit that is rotatably connected to the marine vessel, the propulsion system being configured such that the slip clutch assembly allows the propulsion unit to rotate with respect to the marine vessel in case the propulsion unit impacts an obstacle.