NO346005B1

NO346005B1 - Retractable thruster

Info

Publication number: NO346005B1
Application number: NO20210367A
Authority: NO
Inventors: Halvor Torgersen; Lars Erik Andersen
Original assignee: Sleipner Motor As
Priority date: 2021-03-23
Filing date: 2021-03-23
Publication date: 2021-12-20
Also published as: NO20210367A1; WO2022050850A3; WO2022050850A2

Description

RETRACTABLE THRUSTER

TECHNICAL FIELD

The present invention relates to the field of thrusters for watercrafts, such as vessels, ships and smaller boats and sailboats. More particularly it relates to thrusters that can be retracted into the hull of the watercraft when they are not in use, such as thrusters used for docking a boat.

BACKGROUND

Thrusters for manoeuvring a watercraft have been known for a long time.

Different types of thrusters exist, such as the azimuth thruster which is a combined propulsion and steering device that can be rotated to turn the ship or boat. The tunnel thruster used mainly for larger vessels requires a thruster tunnel to be built into the hull below the waterline. An impeller in the tunnel can create thrust in either direction.

Externally mounted thrusters are mainly used for smaller boats where thrusters have to be retrofitted, and the space in the hull is limited. Such thrusters will increase the boats resistance to forward motion if they are below the water line during normal propulsion.

European patent application EP 1876 094 A2 shows a retractable thruster for a vessel where the propeller unit and the electric motor are moved between a recessed position and an operational position. The propeller unit and the electric motor are comprised in a piston element that can be moved inside a housing by applying hydraulic pressure on the piston.

US patent 5152240 describes a retractable and storable thruster for a vessel, using a trapezoidal deformable rotatable device producing rectilinear movement inside a well in the vessel's hull.

US patent application US 2006/0060127 shows a retractable thruster comprising a propulsion assembly comprising a rigid structure secured to a propeller housing and containing a motor driving the propeller inside the propeller housing via at least one rotary shaft between the motor and the propeller. Displacement means enable the propulsion assembly to be moved between retracted and deployed positions by the propulsion assembly performing uniform circular movement about an axis of rotation situated substantially at the level of the hull or beneath the hull.

European patent application EP2 246 252 A2 shows a thruster that can be tilted into a thruster housing in the hull of a boat. The thruster and the thruster motor driving the propeller are both tiltably connected to a swing frame and will rotate around an axis of the swing frame when moving from an extracted position to a retracted position and vice versa.

European patent application EP2548797A1, discloses a retractable thruster comprising a motor arranged for being fixed inside the hull, a propeller unit arranged for moving along an arc with a first direction of rotation between a retracted position inside the hull and an extended position outside the hull, a door arranged for closing the opening when the propeller unit is in the retracted position, the door further arranged for moving with the propeller unit in the first direction of rotation along the arc and for rotating with a second direction of rotation opposite of the first direction of rotation.

US2019389549A1 discloses a retractable thruster with telescopic sections and a universal joint.

US2019389549A1 discloses a retractable thruster with a rotating device for screwing the thruster with the propeller down below the hull.

GB341437A illustrates an outboard motor with a tiltable transmission element.

WO2012168767A1 discloses a marine propulsion system including a gearbox housing that is attached to the stern of a vessel hull, a pivot casing that can pivot relative to the gearbox housing for trim/tilt and a lower unit that can pivot relative to the pivot casing to steer.

DE2422266A1 discloses a propeller drive for motorboats with vertically swivelable propeller and lee board system to avoid damage when grounding.

NL8700535A discloses a retractable propeller type auxiliary motor for motor/sailer that is enclosed in stem casing.

US5108323A discloses a system for deploying a propulsor unit from the hull of a water vehicle, such as a submarine. The system comprises an opening in a submerged portion of the hull that leads to a chamber for storing the propulsor unit and a cover for covering the hull opening.

While the above-mentioned prior art publications illustrate that steps have been taken to improve retractable thrusters, there are still a number of issues that may be improved, e.g. related to size versus performance that that is critical for installation in many boats, as well as reliability and maintainability issues.

SHORT SUMMARY

The present invention is a retractable thruster for a watercraft with a hull according to independent claim 1, allowing the thruster propeller to easily retract into the hull when not in use. The thruster according to the invention may in embodiments have one or more of the following advantages over prior art:

The thruster has large efficiency with regard to its size and may easily fit into small and narrow hull compartments.

The thruster is reliable and require little maintenance.

Power can be efficiently transferred from the motor to the propeller when the propeller is in the extended position.

Adaptation and retrofitting to a large variety of different hull shapes or hull compartments is made possible.

The retractable thruster does not influence the boats resistance to forward motion significantly when the thruster is in a retracted position.

The thruster propeller is well protected against underwater obstacles that may come in its way both in retracted and extended position.

Assembly and alignment of components during the assembly process is easy.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates in a section view an embodiment of the thruster (1) according to the invention, where the propeller (32) is arranged in a retracted position.

Fig. 2 illustrates in a section view the same thruster as in Fig. 1, with the difference that the propeller is arranged in an extended position.

Fig. 3a, 3b and 3c illustrate in a view, the thruster as illustrated in Fig. 1 installed in a hull of a boat. Fig. 3a illustrates the propeller in the retracted position, Fig. 3c illustrates the thruster in an extended position, and Fig. 3b illustrates a middle position. While the stationary elements of the thruster, such as the motor (2) are arranged above a hole in the hull (100), the propeller is allowed to move from its retracted position inside the hull to the extended position outside or below the hull. A door element (101) is attached to the propeller. The door element is flush with the hull when the propeller is in its retracted position, while it shields the propeller in the extended position.

Fig. 4 illustrates in a perspective view from above, an embodiment of the thruster.

Fig. 5 illustrates in a partly transparent view an embodiment of the thruster (1) arranged in the hull (100) of a watercraft. An adapter element (102) with an upper flange configured to interface a lower flange of the housing (7) is mounted inside the hull. The adapter element may be specific for the hull type and be integrated with the hull, or mounted as part of an upgrade of the hull.

Fig. 6 illustrates in a front section view of a hull (100) of a watercraft an embodiment of the thruster (1) arranged in the hull (100) on top of the adapter element (102).

Fig. 7 is an enlarged view of some of the details in Fig. 2.

Fig. 8a, 8b, 8c, 8d, 8e and 8f illustrate in different views an embodiment of a first or second clutch element (41, 51). Figs. 8a and 8c are side views of the clutch element, where there is a 90-degree rotation of the clutch element in Fig. 8c relative to Fig. 8a. Figs. 8b and 8d illustrate section views A-A and C-C as indicated in Figs. 8a and 8c, respectively. Fig 8e and 8f are different perspective views of the clutch element.

Fig. 9 illustrate in a section view a propeller unit according to an embodiment of the invention. The propeller unit comprises two propeller axles (33) extending from a centre position where they are both driven by the perpendicularly arranged driven axle via a bewel gear. Two propellers (32) are arranged on respective opposite ends of the propeller axles. A duct (35) enclosing the two propellers is fixed to the first link element (91). At each end of the duct, there is a curved lip (36) to take advantage of the coanda effect. The curved lip is here part of the second link element (92), and the second link element rotatably holds and supports the duct.

Fig. 10 illustrate in a section view the same embodiment as in Fig. 10, wherein a first surface (37) extending perpendicularly to the propeller axle in an area at the end of the duct is illustrated. The first surface (36) extends as a prolongation of the lip and may improve the thruster efficiency.

EMBODIMENTS OF THE INVENTION

In the following description, various examples and embodiments of the invention are set forth in order to provide the skilled person with a more thorough understanding of the invention. The specific details described in the context of the various embodiments and with reference to the attached drawings are not intended to be construed as limitations. Rather, the scope of the invention is defined in the appended claims.

The embodiments described below are numbered. In addition, dependent embodiments defined in relation to the numbered embodiments are described. Unless otherwise specified, any embodiment that can be combined with one or more numbered embodiments may also be combined directly with any of the dependent embodiments of the numbered embodiment(s) referred to.

EM 1: A retractable thruster (1) for a watercraft with a hull (100), comprising; - a motor (2) configured to be fixed relative to the hull,

- a propeller (32),

- a position actuator (6) configured to reversibly move the propeller relative to the motor between a retracted position and an extended position, wherein the thruster (1) further comprises;

- a driving axle (21) configured to be driven by the motor,

- a driven axle (31) configured to drive the propeller,

- a clutch configured to engage the driven axle and the driving axle when the thruster is in the extended position, and disengage the driven axle from the driving axle when the thruster is in the retracted position.

In a first dependent embodiment, the position actuator (6) is configured to reversibly rotate the propeller (32) and the driven axle (31) a first rotational direction between the retracted position and the extended position about a first pivot point (P1) fixed relative to the motor (2).

In a second dependent embodiment, that may be combined with EM 1 and the first dependent embodiment, the clutch comprises first and second clutch elements (41, 51), wherein the first clutch element is fixed to the driving axle and the second clutch element is fixed to the driven axle.

[0003] In a third dependent embodiment, that may be combined with any of EM 1 and the dependent embodiments above, a first axis defined by the first rotation point (P1) and a rotational centre of the propeller and a second axis defined by the longitudinal direction of the driven axle, intersect.

[0003] In a fourth dependent embodiment, that may be combined with the third dependent embodiments, the first and second axis intersect in the rotational centre of the propeller.

In a fifth dependent embodiment, that may be combined with the third or fourth dependent embodiments, the first and second axis are inclined at least 10 or 15 degrees relative each other.

In a sixth dependent embodiment, that may be combined with EM1 or any of the dependent embodiments above, the driven axle is in-line with the driving axle when the thruster is in extended position.

In a seventh dependent embodiment, that may be combined with any of the second to sixth dependent embodiments above, the position actuator (6) is configured to reversibly rotate a propeller axle (31) of the propeller (32) and the second clutch element (51) between the retracted position and the extended position about the first pivot point (P1) with the same rotational speed, wherein the radius of the propeller axle is larger than the radius of the second clutch element.

In an eight dependent embodiment, that may be combined with any of the third to seventh dependent embodiments, the first pivot point (P1) is arranged between the driving axle (21) and the propeller (32) when the thruster is in the retracted position.

In a ninth dependent embodiment, that may be combined with EM1 or any of the dependent embodiments above, the propeller (32) is configured to be arranged inside the hull (100) in the retracted position, and outside the hull (100) in the extended position.

In a tenth dependent embodiment, that may be combined with EM1 or any of the dependent embodiments above, the driven axle (32) is arranged perpendicular to a propeller axle (33) of the propeller (32).

EM 2: The thruster according to EM 1, wherein the position actuator (6) is configured to reversibly rotate a door (101) a second rotational direction about a second pivot point (B).

The second rotational direction is opposite the first rotational direction.

In a first dependent embodiment, that may be combined with EM 2, the second pivot point (P2) coincides with a propeller axle (33) of the propeller (32).

In a second dependent embodiment, that may be combined with EM 1 and the first dependent embodiment, the thruster comprises a four-bar linkage, wherein the first and second pivot points (P1, P2) are arranged on a first link element (91) of the linkage, and the door (101) is fixed to a second link element (92) of the linkage wherein the first and second link elements are linked in the second pivot point (P2).

In a third dependent embodiment, that may be combined with the second dependent embodiment, the position actuator (6) is configured to rotate the first link element. It may be pivotally connected to the first link element.

In a fourth dependent embodiment, that may be combined with EM 1 and any of the dependent embodiments, the door rotates about the second pivot point (P2) with a lower absolute speed than the propeller rotates about the first pivot point (P1).

In a fifth dependent embodiment, that may be combined with any of the first to fourth dependent embodiments, the thruster comprises a duct (35) or a tunnel, wherein the propeller (32) is arranged inside the duct.

In a sixth dependent embodiment, that may be combined with any of the second to fifth dependent embodiments, the duct is fixed to the first link element (91) and the second link element (92) is arranged to rotatably hold the duct.

In a seventh dependent embodiment, that may be combined with any of the fifth to sixth dependent embodiments, the thruster comprises a curved lip (36) at the end of the duct. The lip may in a cross section have an elliptical shape with an increasing diameter away from the propeller.

In an eight dependent embodiment, that may be combined with any of the fifth to sixth dependent embodiments, the thruster comprises a first surface (37) extending perpendicularly to the propeller axle in an area at the end of the duct.

In a nineth dependent embodiment, that may be combined with the eight dependent embodiment, the first surface (36) extends as a prolongation of the lip for at least parts of the circumference of the duct.

EM 3: The thruster (1) according to EM1 or EM2, comprising a frame (8) comprising a first through bore, wherein the driving axle (21) is rotatably arranged inside the first through bore.

In a first dependent embodiment, that may be combined with EM 3, the thruster comprises a housing (7) fixed to the frame.

In a second dependent embodiment, that may be combined with the first dependent embodiment, the housing (7) comprises a second through bore and the frame is arranged through said second through bore.

In a third dependent embodiment, that may be combined with any of EM3 and the first to second dependent embodiments, the motor (2) is fixed to the frame.

In a fourth dependent embodiment, that may be combined with any of the first to third dependent embodiments, the housing has an inside and an outside, wherein the outside is configured to face towards the sea, and the inside is configured to face towards the hull compartment, wherein the motor (2) is arranged on the inside and the propeller (32) is arranged on the outside.

In a fifth dependent embodiment, that may be combined with any of EM3 and the first to fourth dependent embodiments, the frame comprises first and second frame elements (81, 82) wherein the housing is fixed between the first and second frame elements.

In a sixth dependent embodiment, that may be combined with the fifth dependent embodiments, the second frame element is arranged on the outside of the housing, and wherein the motor is fixed to the second frame element.

In a seventh dependent embodiment, that may be combined with any of EM3 and the dependent embodiments, the first pivot (P1) is fixed relative to the frame.

EM 4: The thruster (1) according to any of EM1 to EM3, wherein the thruster (1) comprises an end stop (81) configured to define the maximum extension of the propeller (32).

In a first dependent embodiment, that may be combined with EM4, the end stop is adjustable, allowing the maximum extension of the propeller to be set to a position where the driving axle (21) and the drive axle (31) are aligned in-line.

In a second dependent embodiment, that may be combined with EM3, the end stop is fixed to the frame (8).

EM 5: The thruster (1) according to any of EM1 to EM4, wherein any of the driving axle (21) and the driven axle (31) is axially resilient and configured to be compressed. This ensures that the clutch elements will be properly aligned when engaged, even after some wear, and in the situations where the clutch surfaces are not clean before engagement.

EM 6: The thruster (1) according to any of EM1 to EM5, wherein the clutch is a dog clutch.

In a first dependent embodiment, that may be combined with EM6, the first clutch element (41) comprises first teeth (42) that are symmetrical about an axis in the longitudinal direction of the driving axle (21).

In a second dependent embodiment, that may be combined with the first dependent embodiment, the first teeth have first and second surfaces (43a, 43b) arranged symmetrically about a first plane defined by the longitudinal direction of the driving axle (21) and the radius of the first clutch element (41).

In a third dependent embodiment, that may be combined with the second dependent embodiment, the surfaces are flat and the inclination of the surfaces is less than 5 degrees with respect to the first plane.

In a fourth dependent embodiment, that may be combined with the second or third dependent embodiment, the first and second surfaces are triangular.

In a fifth dependent embodiment, that may be combined with any of the first to fourth dependent embodiment, the teeth have a radially arranged sharp edge. The sharp edge helps to clean the surfaces of the opposing teeth.

In a sixth dependent embodiment, that may be combined with any of the first to fifth dependent embodiment, the number of first teeth is even.

In a seventh embodiment, that may be combined with any of the first to sixth dependent embodiment, the first clutch element comprises a radial groove (44) between each tooth configured to allow the sharp edges of the teeth of the second clutch element to have some room when the clutch elements are in full engagement, in case there should be any obstacles from the sea between the clutch elements.

In a seventh eight dependent embodiment, that may be combined with any of the first to seventh dependent embodiment, the second clutch element (51) comprises second teeth that are identical to the first teeth.

EM 7: The thruster (1) according to any of EM 1 to EM 6, comprising a retract lock (10) configured to lock the propeller (32) in the retracted position.

In a first dependent embodiment, that may be combined with EM 7, the retract lock comprises a lock actuator (11) and a lock element (12), wherein the lock actuator is configured to actuate the lock element to lock the propeller (32) in the retracted position.

In a second dependent embodiment, that may be combined with the first dependent embodiment, the thruster comprises a propeller unit (3) comprising the propeller and arranged about a circumference of the propeller (32), wherein the lock element is configured to grip and hold a lower side of the propeller unit when the propeller (32) is in the retracted position. The propeller unit may in comprise the second link element.

The motor (2) may in combinations with any of the embodiments above be e.g., hydraulic or electric.

The position actuator (6) may in combinations with any of the embodiments above be e.g., hydraulic or electric.

In the following, a specific embodiment illustrated by the figures will be explained.

Looking first at Fig. 1, we see that the thruster (1) for a watercraft with a hull (100), comprising a frame element (8), and a motor (2) arranged on the frame element. The frame element (8) has a first through bore for the driving axle (21) that is supported by a bearing inside the through bore. A first clutch element (41) is arranged at the lower end of the driving axle.

Further, a housing (7) with a through bore for the frame and fixed to the frame, separates an inside of the hull from the outside, where the motor is arranged on the inside. The motor may be connected to an on-board hydraulic system, not shown here. The outside is in direct contact with the sea when the thruster is in extended position.

In e.g., Fig. 5 and 6, it is illustrated how the housing can be arranged on top of an adapter element (102) with the same perimeter shape as the lower end of the housing. The lower end of the adapter element is configured to be sealingly fixed to the hull, or an integral part of the hull. The hull has a through hole inside the perimeter of the adapter element.

Again, referring to Fig. 1, a propeller (32) can be seen arranged inside the housing. The thruster is here in a retracted position. The propeller is pivotally connected to the frame in a hinge with a first pivot point (P1) via a first link element (91), where the pivot point is arranged between the driving axle (21) and the propeller in the longitudinal direction of the hull.

A driven axle (31) arranged perpendicular to a propeller axle (33), is configured to drive the propeller axle via a bewel gear (not shown). The driven axle is inclined downwards with respect to the first link element when the thruster is in the extended position, as illustrated in Fig. 2. In this embodiment the inclination is fixed to about 20 degree. The driven axle is supported by rotational bearings that are arranged in an axle housing (34) fixed relative to the first link element (91).

A second clutch element (51) is arranged on the far end of the driven axle, as seen from the propeller.

As best seen in Fig. 4 and 5, a hydraulic position actuator (6) arranged inside, is pivotally connected to an end of the first link element (91), where the end is arranged opposite the first pivot point (P1) with respect to the propeller.

As the position actuator retract, the first link element (91) will be forced to rotate about the pivot point (P1), and the propeller will be leaving the housing as seen e.g. in Fig. 3b and Fig. 5.

The rotation continues until an end stop (83) of the frame abuts the axle housing (34). The thruster is now in the extended position and the propeller is free from the housing and the hull as seen e.g., in Fig. 2 and Fig. 3c.

In the extended position the first and second clutch elements are engaged, and the driving and driven axles are aligned in-line. When the motor is operated, in one direction or the other, the propeller will rotate to give the desired thrust.

Fig. 8a to 8f illustrate the first and second clutch elements (41, 51) of the dog clutch used in this embodiment in more detail. The clutch elements are identical. Further, to support two-way operation the first and second teeth (42, 52) are symmetrical about a first plane through the longitudinal centre of the clutch elements, i.e. through the centre of the driving and driven axles in the longitudinal direction, respectively.

The first and second teeth have first and second surfaces (43a, 43b) arranged symmetrically about a first plane defined by the longitudinal direction of the driving axle (21) and the radius of the first clutch element (41). Further, the surfaces are triangular and flat and the inclination of the surfaces is about 2 degrees with respect to the first plane. This ensures a secure transfer of rotational energy through the clutch in both directions. It can also be seen that the sharp edge of each tooth is radial, and that there are 6 teeth on each of the clutch elements.

In Fig. 7, the first and second clutch elements (41, 51), the driving axle (21) and the frame (8) related to this specific embodiment, can be seen in more detail. The frame comprises first and second frame elements (81, 82) wherein the housing (7) is sealingly fixed between the frame elements.

As mentioned previously, the driving axle (21) runs through the frame in which it is rotatably supported by a bearing, and the frame in turn runs through a through bore of the housing.

The driving axle (21) is here configured to be resilient in the axial direction to secure clutch engagement during different operating conditions and wear. The driving axle is rotationally fixed to the motor shaft with a spline joint, and a helical spring arranged about the driving axle providing a constant push force on the driving axle towards the clutch, ensures a secure engagement.

The thruster is configured to hold a door (101) that fits into the hole in the hull (100) when the thruster is in the retracted position, as illustrated in e.g. Fig. 3a. The door follows the propeller about the first pivot point (P), but in order to prevent the door from colliding into the hull, it rotates in a second rotational direction about a second pivot point (B) coinciding with the propeller axis, where the second rotational direction is opposite to the first rotational direction. Thus, instead of colliding with the hull, the door becomes a shield for the propeller in the extended position.

The second rotational movement is achieved by a four-bar linkage, wherein the first and second pivot points (P1, P2) are arranged on the first link element (91) of the linkage, and the door (101) is fixed to a second link element (92) of the linkage, wherein the first and second link elements are linked in the second pivot point (P2). A third link element (93) of the four-bar linkage is part of the frame (8) where one end is pivotally connected to the first link arm in the first pivot point (P1) and a second end is pivotally connected to a first end of a fourth link arm (94). The second end of the fourth link arm is pivotally connected to a first end of the second link arm (92). The second end of the second link arm is the second pivot point (P2). Further, the second link arm is in this case the same element as the propeller unit (3), or constitutes a part of the propeller unit, wherein the door (100) is fixed to the propeller unit, opposite the first end.

In the exemplary embodiments, various features and details are shown in combination. The fact that several features are described with respect to a particular example should not be construed as implying that those features by necessity have to be included together in all embodiments of the invention. Conversely, features that are described with reference to different embodiments should not be construed as mutually exclusive. As those with skill in the art will readily understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit description of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations of features have been omitted for the sake of simplicity or brevity.

Claims

1. A retractable thruster (1) for a watercraft with a hull (100), comprising;

- a motor (2) configured to be fixed relative to the hull,

- a propeller (32),

- a driving axle (21) configured to be driven by the motor,

- a driven axle (31) configured to drive the propeller, wherein the retractable thruster is characterized in that it comprises;

2. The retractable thruster of claim 1, wherein the position actuator (6) is configured to reversibly rotate the propeller (32) and the driven axle (31) a first rotational direction between the retracted position and the extended position about a first pivot point (P1) fixed relative to the motor (2).

3. The retractable thruster of claim 1 or 2, wherein the clutch comprises first and second clutch elements (41, 51), and wherein the first clutch element is fixed to the driving axle and the second clutch element is fixed to the driven axle.

4. The retractable thruster of any of claims 1 to 3, wherein a first axis defined by the first rotation point (P1) and a propeller axis of the propeller and a second axis defined by the longitudinal direction of the driven axle, intersect in the propeller axis.

5. The retractable thruster of claim 4, wherein the first and second axis are inclined at least 10 or 15 degrees with respect to each other.

6. The retractable thruster of any of claims 1 to 5, wherein the driven axle is in-line with the driving axle when the thruster is in extended position.

7. The retractable thruster of any of claims 1 to 6, wherein the position actuator (6) is configured to reversibly rotate a propeller axle (31) of the propeller (32) and the second clutch element (51) between the retracted position and the extended position about the first pivot point (P1), with the same rotational speed, wherein the radius of the propeller axle is larger than the radius of the second clutch element.

8. The retractable thruster of any of claims 1 to 7, wherein the first pivot point (P1) is arranged between the driving axle (21) and the propeller (32) when the thruster is in the retracted position.

9. The retractable thruster of any of claims 1 to 8, wherein the clutch is a dog clutch.

10. The retractable thruster of claim 9, wherein the first clutch element (41) comprises first teeth (42) that are symmetrical about an axis in the longitudinal direction of the driving axle (21), wherein the first teeth have first and second surfaces (43a, 43b) arranged symmetrically about a first plane defined by the longitudinal direction of the driving axle (21) and the radius of the first clutch element (41), wherein the surfaces are flat and the inclination of the surfaces is less than 5 degrees with respect to the first plane.