STERN THRUSTER

FIELD OF THE INVENTION

The present invention relates to a stern thruster and particularly, although not exclusively, to a stern thruster suitable to be installed on the transom of a hull of a boat such as a pontoon boat.

BACKGROUND

Maneuvering vessels in the confines of a busy harbour or marina can be challenging, with cross winds and tides making mooring particularly difficult. In order to ease the mooring process, large vessels can be equipped with an additional thruster, which is oriented transversely to the main propulsion unit, to provide lateral thrust. One type of known additional thruster is a vertical retracting tunnel thruster (VRTT).

VRTTs are known to be installed within the hull of a vessel. A VRTT typically comprises a motor, a drive shaft, a propeller and an actuator for axially moving the propeller in a vertical direction relative to the hull. In operation, VRTTs can adopt a retracted state, where the propeller remains within the hull, and a deployed state, where the propeller projects out of the hull. It is when the VRTT is in the deployed state that the propeller is capable of generating lateral thrust for the vessel.

Another type of thruster is a swing thruster, which also has a retracted state and a deployed state.

A known example of a vessel is a pontoon boat. Pontoon boats comprise a flat deck attached on top of buoyant elongate tubes (known as pontoons). These pontoons extend the length of the boat and can house a variety of marine equipment, such as the fuel & water tanks, windlass and pressurised tanks. Pontoon boats are popular, relatively low-cost boats in the leisure boating industry. The pontoons of such pontoon boats may for example have an internal diameter in the region of 600 mm.

Pontoon boats with two pontoons are known. Pontoon boats with three pontoons are known and may be referred to as “tritoons”. The individual pontoons may be referred to as “hulls”.

The present inventors have realised that VRTTs and swing thrusters are not readily adaptable for pontoon boats because there is only limited available space to house the VRTT in the retracted state in one or more of the pontoons (hulls) of the pontoon boat. Furthermore, such thrusters are difficult to install after manufacture of the boat.

The present invention has been devised in light of the above considerations. Furthermore, although the present invention was devised with the intention to be implemented on pontoon boats, the present inventors have realised that it has wider applicability.

SUMMARY OF THE INVENTION

The present inventors have realised that it would be advantageous to provide a stern thruster that can be more conveniently mounted to a boat than has previously been considered.

Accordingly, in a first aspect, the present invention provides a boat with at least one hull and an outboard motor, the at least one hull having a transom wherein the outboard motor comprises:

- a powerhead;
- a mounting bracket attaching the outboard motor with respect to the hull;
- a midsection leg extending downwardly from the powerhead;
- a lower unit provided at a downward end of the midsection leg, the lower unit comprising
- a propulsion propellor configured to be positioned below a waterline of the hull in use,
  
  the boat further comprising a stern thruster, the stern thruster comprising:
- at least one thruster motor;
- at least one thruster propellor;
- a sleeve housing the at least one thruster motor and the at least one thruster propellor;
  
  wherein the stern thruster is attached with respect to the transom, at a position below a waterline of the hull in use, with the stern thruster positioned between the midsection leg or lower unit of the outboard motor and the transom, the stern thruster configured to provide lateral thrust to the hull.

Accordingly, embodiments of the invention provide a stern thruster that can be conveniently mounted to a boat. Such a stern thruster can be mounted in a position that does not disturb the typical mounting of an outboard motor on such a boat. Therefore it is particularly suitable as an aftermarket modification, which may even be suitable for installation by the boat owner themselves.

The present invention has applicability for example for pontoon boats. However, the stern thruster may alternatively be attached to a transom of a hull of another type of boat, whether mono hull or multi hull. The expression “boat” is intended to include pleasure craft in general, including sailing boats to the extent that an outboard motor is provided on such a sailing boat.

It is considered that embodiments of the invention provide improvements over alternative approaches to the fitting of stern thrusters. For example, stern thrusters that attach to the boat transom may have unwieldy mounting arrangements with the result that they cannot be fitted between the transom and the outboard motor. In other approaches, stern thrusters may be mounted to the outboard motor itself, for example to a cavitation plate of the outboard motor. However, this may cause issues of corrosion if raw holes are drilled into the cavitation plate of the outboard motor in order to attach the stern thruster. Additionally, imposing lateral forces on the outboard motor may compromise the mounting of the outboard motor and/or may affect the steering mechanism of the outboard motor.

Further optional features of the invention are now set out. The invention includes the combination of any aspect of the invention and any optional features described except where such a combination is clearly impermissible or expressly avoided.

In some embodiments, where the boat is a pontoon boat, is has two pontoon hulls. In some embodiments, the pontoon boat has three pontoon hulls. In this case, it is typical for the stern thruster to be attached to a central one of said three pontoon hulls.

There may be provided a thruster mounting bracket. The thruster mounting bracket may be attached to the transom and the stern thruster being attached to the thruster mounting bracket. In some embodiments, the thruster mounting bracket is permanently attached to the transom and permits temporary removal and reattachment of the stern thruster.

The stern thruster may comprise a complementary connector configured to slide onto the thruster mounting bracket from above in a substantially downwards direction. For example, at least one of the thruster mounting bracket and the complementary connector may be shaped to permit the complementary connector to attach to the thruster mounting bracket in only one orientation.

In some embodiments, the stern thruster further comprises a second thruster motor and a second propellor. The propellors of the stern thruster may be provided at opposing lateral sides of the stern thruster, with the thruster motors disposed inwardly of the propellors.

The sleeve may provide a passage from one lateral side of the stern thruster to another lateral side of the stern thruster. Each thruster motor may be held within the passage such that water flows axially along the passage and around each thruster motor when operated to drive the respective thruster propellor.

The at least one thruster propellor may have a diameter of not more than 185 mm. The at least one thruster propellor may have a diameter of at least 80 mm or at least 90 mm.

Considering that the pontoon boat has a fore-aft direction extending between a bow and a stern of the pontoon boat, the at least one thruster propellor may be rotatable about a rotation axis that is oriented transverse the fore-aft direction. Also considering that the transom has a top and a bottom, the rotation axis of the propellor may be positioned not lower than the bottom of the transom. The rotation axis may be positioned not more than a distance equal to the sum of the thruster propellor radius and 20 mm from the transom. In some embodiments, the rotation axis may be positioned not more than a distance equal to two times the thruster propellor diameter from the transom.

In some embodiments, the sleeve has a waisted central portion facing the midsection leg or lower unit of the outboard motor in order to provide clearance between the stern thruster and the outboard motor.

SUMMARY OF THE FIGURES

Embodiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

FIG. 1 shows a port orthographic view of a three pontoon hull vessel (a tritoon) according to an embodiment of the invention.

FIG. 2 shows an aft orthographic view of the tritoon shown in FIG. 1.

FIG. 3 shows a partial view of FIG. 1 showing the stern portion of the tritoon.

FIG. 4 shows a view similar to FIG. 3 with the outboard motor omitted in order to provide an unobstructed port side view of the stern thruster.

FIG. 5 shows a view similar to FIG. 2, with the outboard motor omitted in order to provide an unobstructed aft side view of the stern thruster.

FIG. 6 shows a bottom orthographic view of the stern thruster and the thruster mounting bracket.

FIG. 7 shows an orthographic view, from starboard, of the stern thruster and the thruster mounting bracket.

FIG. 8 shows an orthographic view, from aft, of the stern thruster and the thruster mounting bracket.

FIG. 9 shown an orthographic view, from port, of the stern thruster and the thruster mounting bracket.

FIG. 10 shows a perspective view, from starboard and from above, of the stern thruster and the thruster mounting bracket.

FIG. 11 shows a cutaway view of FIG. 10 with internal elements of the stern thruster visible.

FIG. 12 shows an exploded perspective view, from starboard and from above, of the stern thruster and the thruster mounting bracket.

FIG. 13 shows another exploded perspective view, from port and from above, of the stern thruster, the thruster mounting bracket and the transom of the tritoon, with the thruster mounting bracket attached to the transom.

FIG. 14 shows an orthographic view, from aft, of the tritoon shown in FIG. 1, with the outboard motor and the stern thruster omitted in order to show an unobstructed view of the thruster mounting bracket.

FIG. 15 shows a partial view, from port, of the tritoon of FIG. 1, showing the stern portion with the outboard motor omitted and the stern thruster in a pre-attachment configuration.

FIG. 16 shows a perspective view, from the port and from above, of the tritoon of FIG. 1, showing the stern portion with the outboard motor omitted and the stern thruster in the pre-attachment configuration seen in FIG. 15.

FIG. 17 shows a partial view, from port and from above, similar to FIG. 15 but with the stern thruster in a partially attached configuration.

FIG. 18 shows a perspective view, from port and from above, similar to FIG. 16 but with the stern thruster in the partially attached configuration.

FIG. 19 shows a perspective view, from port and from above, similar to FIG. 18 but with the stern thruster in the attached configuration wherein the stern thruster is attached to the transom.

DETAILED DESCRIPTION OF THE INVENTION

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference in their entirety.

Where appropriate, corresponding features in the figures are given corresponding reference number and the description of some features of some figures may be omitted where they have been described previously.

FIG. 1 shows a (port) side orthographic view a three pontoon hull vessel (a tritoon) 100 according to an embodiment of the present invention. FIG. 2 shows a different (rear, aft, orthographic) view of the same three pontoon hull vessel. This vessel is also referred to herein as a boat or a pontoon boat. As discussed above, the stern thruster of the present invention may be used on a different type of vessel, such as a mono hull pleasure craft.

The vessel has three elongate pontoon hulls, central pontoon hull 102, port pontoon hull 104 and starboard pontoon hull 106. Each pontoon hull extends in the longitudinal (fore-aft) direction of the vessel, from a bow region of the vessel to a stern region of the vessel.

The pontoon hulls 102, 104, 106 are parallel to each other. Although not shown, a base deck structure is arranged at the upper side of the pontoon hulls. The base deck structure comprises an arrangement of laterally extending beams. These are attached to the pontoon hulls by a corresponding arrangement of brackets 103 welded to the pontoon hulls.

A superstructure is supported on the base deck structure. The superstructure includes various items arranged for user comfort and for usability of the boat. For example, there may be provided a deck 105 overlaying the base deck structure and providing a surface suitable for users to walk on, a perimeter surround 110 or railing, seating, steering equipment, fishing stations, etc. In the illustrated tritoon 100, the superstructure includes a swim ladder 112.

Each pontoon hull typically comprises an aluminium structure. The general shape of the structure is cylindrical (circular cylindrical) with a typical maximum diameter of about 600 mm. Each pontoon hull has a stern region. The stern region of the central pontoon hull 102 comprises a blunt or flat end that forms the transom 114 of the vessel 100 (seen in FIG. 4). The transom 114 has a bottom at the lower end and a top at the upper end. In alternative embodiments, the transom 114 of the tritoon may be separate from the pontoon hulls 102, 104, 106 and positioned aft the central pontoon hull 102.

FIGS. 2 and 3 show an outboard motor 120 of the tritoon 100 arranged at the stern portion. The outboard motor 120 is positioned aft the transom 114, centrally between port and starboard, and is attached with respect to the central pontoon hull 102 (i.e. the transom 114, having a top 114a and a bottom 114b) using a mounting bracket. As best shown in FIG. 3, the outboard motor 120 comprises a powerhead 122, a midsection leg 124 extending downwardly from the powerhead, and a lower unit 126 provided at a downward end of the midsection leg 124. The lower unit 126 extends beneath a lower end (i.e. the bottom 114b) of the transom and comprises a propulsion propellor 128 configured to be positioned below a waterline 101 of the pontoon hull in use.

A gap is provided between the transom 114 and the outboard motor 120. More specifically, a gap is provided between the transom 114 and the midsection leg 124 and/or lower unit 126. The gap is positioned below the waterline 101 of the pontoon hull in use, and extends across the stern (i.e. the transom 114).

As best shown in FIG. 3, a stern thruster 130 is positioned within the gap beneath the outboard motor 120. The stern thruster is thus positioned between the transom 114 and the outboard motor 120, such that it is positioned below the waterline 101 of the tritoon 100 when in use.

FIGS. 4 and 5 show the stern portion of the tritoon 100 without the outboard motor to provide an unobstructed view of the stern thruster 130. The stern thruster 130 is externally mounted to the transom 114 (i.e. to the central pontoon hull 102) using a thruster mounting bracket 160 (seen in FIG. 13). The stern thruster 130 may be directly or indirectly mounted to the transom 114, provided it is positioned beneath the outboard motor 120 and below the waterline 101 of the pontoon hull in use.

FIGS. 6 to 10 show the stern thruster 130 and the thruster mounting bracket 160 in isolation from the rest of the tritoon 100 and in an attached configuration (i.e. a configuration in which the thruster mounting bracket 160 is attached to the transom 114 and the stern thruster 130 is attached to the thruster mounting bracket 160). FIG. 6 shows a bottom orthographic view of the stern thruster 130 and the thruster mounting bracket 160. FIG. 7 shows a right orthographic view of the stern thruster 130 and the thruster mounting bracket 160, as would be seen from starboard. FIG. 8 shows a side orthographic view of the stern thruster 130 and the thruster mounting bracket 160, as would be seen from aft. FIG. 9 shows a left orthographic view of the stern thruster 130 and the thruster mounting bracket 160, as would be seen from port. FIG. 10 shows a perspective view from above and from starboard.

The stern thruster 130 comprises a sleeve 132 with a complementary connector 134 that is configured to slide onto the thruster mounting bracket 160 in a substantially downwards direction. The complementary connector 134 and/or the thruster mounting plate 160 are shaped to permit the complementary connector 134 to attach to the thruster mounting bracket 160 in only one permitted orientation. The shape of the thruster mounting bracket 160 can be seen in FIGS. 12 to 14. The stern thruster 130 is attached to the transom 114 using a pair of mechanical fasteners 136 (bolts) that are received by concentric apertures 137 in the sleeve 132 and the thruster mounting bracket 160 (as seen in FIG. 12). The purpose of the thruster mounting bracket 160 is to permits temporary removal and reattachment of the stern thruster 130 with the transom 114.

The sleeve 132 has a waisted central portion 132a facing the midsection leg or lower unit of the outboard motor in order to provide clearance between the stern thruster and the outboard motor.

When viewed from above or below as in FIG. 6, the sleeve 132 therefore has a concave external profile. The sleeve has open ends that correspond to the lateral sides 138 of the stern thruster 130 (in a port-starboard direction). The sleeve 132 therefore has a reduced diameter at the central region (as best seen in FIG. 6) compared to the diameter at the open ends, when the diameter is measured in the fore-aft direction of the vessel. The stern thruster 130 therefore has an external profile that conforms to the shape of the outboard motor. This is particularly advantageous when the diameter of the open ends must be greater than a width of the gap adjacent the outboard motor, in the fore-aft direction. However, in order to ensure efficiency of operation of the stern thruster, the sleeve has a convex outer profile 132b when viewed from aft. Accordingly, the inner diameter of the sleeve at the central portion of the sleeve is larger when measured in the vertical direction than when measured in the fore-aft direction. This is as shown in FIG. 8. This ensures a more consistent cross sectional area for water travelling through the stern thruster in operation.

The stern thruster 130 has a thruster propellor 140 disposed at each lateral side 138. Each thruster propellor 140 is housed within the sleeve 132 and has a diameter (i.e. a propellor diameter) of not more than 185 mm for example. A suitable diameter for example is about 90 mm. The propellor diameter may determine the diameter of the sleeve 132 at the open ends. The thruster propellors 140 at the lateral sides 138 oppose each other but may be operated in synchronisation. The thruster propellers may be operated to provide bidirectional thrust (in either direction, port or starboard). As best seen in FIG. 5, when the stern thruster 130 is attached to the tritoon 100, each thruster propellor 140 is rotatable about a rotation axis that is oriented (substantially) transverse to the fore-aft direction. The rotation axis is therefore (substantially) parallel to the port-starboard direction and provides thrust across the stern. Advantageously, the rotation axis is positioned not lower than the bottom of the transom 114, and not more than a distance equal to two times the propellor radius from the transom 114.

FIG. 11 shows a cutaway view of FIG. 10 with internal elements of the stern thruster 130 visible. As seen here, a passage extends between the lateral sides 138 of the stern thruster 130 (in the port-starboard direction). Each thruster propellor 140 is attached to, and operated by, a thruster motor 141 housed within the sleeve 132 using a tube 142, which is itself housed within the sleeve 132. The tube 142 extends through the passage and positions each thrust propellor at the lateral sides 138 of the stern thruster 130. The tube 142 is slightly curved to accommodate the wasting of the sleeve 132. The rotation axes of the propellors is substantially or nearly parallel to the port-starboard direction to provide lateral thrust. In use, lateral thrust is provided by water flowing axially along the passage (around the tube 142 and thruster motor 141) when the thruster propellors are rotated (i.e. driven or operated by the respective thruster motor 141).

FIG. 12 shows an exploded perspective view, from starboard and from above, of the stern thruster 130 and thruster mounting bracket 160. Here, it is seen that the stern thruster 130 comprises a first thruster motor 144 and a second thruster motor 146 positioned adjacent the respective thruster propellor 140 at opposing lateral sides 138 of the stern thruster 130. A thruster propellor 140 is attached to a shaft 148 of the first thruster motor 144. The shaft 148 is position along the rotation axis of the thruster propellor 140, parallel to the passage, and allows the thrust propellor 140 to be operated by the first thruster motor 144. Likewise, a thruster propellor 140 is attached to a shaft 148 of the second thruster motor 146, that is positioned along the rotation axis parallel to the passage and allows the thrust propellor 140 to be operated by the second motor 146. The thrust propellors 140 can therefore be operated independently and/or in tandem to provide bidirectional thrust. In alternative embodiments, each thruster propellor 140 may be operated by a single thruster motor to provide bidirectional lateral thrust.

FIG. 13 shows another exploded perspective view, from port and from above, of the stern thruster 130 and thruster mounting bracket 160, and further showing the central pontoon hull 102 and the transom 114.

It can be seen that the thruster mounting bracket 160 is fixed to the transom 114. This may be permanent or temporary. For example, the thruster mounting bracket may comprise apertures 139 for attaching the thruster mounting bracket 160 to the transom 114, as shown in FIG. 12. Regardless, the purpose of the thruster mounting bracket 160 is to permit the temporary removal and reattachment of the stern thruster 130 to the transom 114, or replacement of the stern thruster 130. The thruster mounting bracket 160 is positioned and orientated for engagement with the complementary connector 134 of the stern thruster 130 and, when engaged, ensures the stern thruster 130 is correctly positioned to provide lateral thrust across the transom 114. This position and orientation is further illustrated in FIG. 14 which shows an unobstructed view of the thruster mounting bracket from aft the tritoon 100.

The method of attaching (and temporarily removing) the stern thruster 130 from the tritoon 100 is discussed with reference to FIGS. 15 to 19.

FIGS. 15 and 16 show the stern thruster 130 in a pre-attachment configuration with the thruster mounting bracket 160. In the pre-attachment configuration, the thruster mounting bracket 160 is attached to the transom 114, and the stern thruster 130 (and each of the mechanical fasteners 136) is in a position remote from the thruster mounting bracket 160. The stern thruster 130 (and each of the mechanical fasteners 136) is orientated and positioned such that the complementary connector 134 is aligned with the thruster mounting bracket 160. In this orientation and position, the stern thruster 130 may be slid onto the thruster mounting bracket 170 by moving the stern thruster 130 in the permitted direction. In the present example, there is a single permitted direction that is a substantially downwards direction. The stern thruster 130 is therefore oriented and positioned above the thruster mounting bracket 160 in the pre-attachment configuration.

FIGS. 17 and 18 show the stern thruster 130 in a partially attached configuration. In the partially attached configuration, the stern thruster 130 has been slid in the permitted direction (i.e. in the substantially downwards direction) so that the complementary connector 134 is at least partially slid onto the thruster mounting plate 160.

FIG. 19 shows the stern thruster 130 in the attached configuration. In the attached configuration, the stern thruster that has been slid in the permitted direction to position the stern thruster 130 as discussed above. Here, the complementary connector 134 envelops the thruster mounting bracket 160 and the mechanical fasteners 136 temporarily secure the stern thruster 130 to the transom 114.

The stern thruster 130 can be temporarily removed from the tritoon 100 by reversing these steps. In other words, the stern thruster 130 can be temporarily removed from the transom 114 by removing the mechanical fasteners 136, and sliding the stern thruster 130 in a direction opposite to the permitted direction (i.e. a substantially upwards direction) into a position in which the stern thruster 130 is detached and remote from the thruster mounting bracket 160.

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/−10%.

STERN THRUSTER

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CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

Provisional Applications (1)