TUNNEL THRUSTER

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to US patent application serial No 63701677 filed October 1 2024 which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a tunnel thruster and particularly, although not exclusively, to a tunnel thruster suitable to be installed within the hull of a pleasure craft such as a pontoon boat.

BACKGROUND

Manoeuvring larger 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 thruster, 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. They comprise 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 generates lateral thrust for the vessel. However, VRTTs are relatively complex and require that the hull is in water deep enough to provide clearance for movement from the retracted to the deployed state. In shallower water, the VRTT would be susceptible to damage by grounding.

Another type of additional thruster is a tunnel thruster. Such thrusters comprise a motor, a drive shaft, a propeller and a tunnel. The propeller is mounted for rotation within the tunnel and the tunnel is installed so as to extend laterally through the hull, below the waterline, opening to the water at respective ports on either side of the hull. Tunnel thrusters are therefore relatively simple, in the sense that the position of the motor, drive shaft and the axis of rotation of the propeller are fixed. The propeller is protected form damage by grounding because it does not project from the hull, even when in operation.

The present inventors have realised that further improvements to tunnel thrusters are possible, particularly for vessels intended to be used in relatively shallow water. A known example of a such a vessel is a pontoon boat. Pontoon boats comprise a flat deck attached on top of buoyant elongate tubes (known as pontoons, or pontoon hulls). 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 600mm. Pontoon boats with two pontoons are known. Also known are pontoon boats with three pontoons, one of which is centrally located. Pontoon boats with three pontoons may sometimes be known as tritoons.

Pontoon boats are particularly suitable for use on inland waters and are typically highly stable, allowing boat manufacturers to build comfortable user accommodation space on the deck, such as seating, sun-loungers and fishing stations. As mentioned, one of the advantages of pontoon boats is that they may have a shallow draft, allowing them to explore areas of relatively shallow water without risk of grounding. This is made possible because the multiple shallow pontoons provide stability without the need for a keel or centreboard. However, this presents challenges when considering incorporating thrusters for such boats.

The present invention has been devised in light of the above considerations.

SUMMARY OF THE INVENTION

The present invention is based on the inventors’ realisation that it would be advantageous to provide a tunnel thruster that is adapted for installation on a shallow draft vessel. The use of a tunnel thruster is desirable in view of their relatively simple construction and therefore cost-efficiency to manufacture and install. However, for shallow draft vessels, there is typically only a small proportion of the depth of the hull (e.g. pontoons) that is below the waterline. There is therefore a risk that part of a tunnel thruster installed in the hull will be above the waterline, at least sometimes, and therefore disadvantageously aspirate air, leading to a loss of efficiency and unwelcome noise.

Accordingly, in a first aspect, the present invention provides a pleasure boat having at least one hull and a tunnel thruster, wherein: the tunnel thruster includes a motor, a propeller and a tunnel; the tunnel is installed through and across the at least one hull, from a first aperture at a first side of the hull to a second aperture at a second side of the hull; the propeller is mounted for rotation about a propeller principal axis within the tunnel so that, when the pleasure boat is level, the propeller principal axis is substantially horizontal and substantially perpendicular to a disc swept by the propeller; the tunnel thruster is operable to drive water between the first and second apertures to provide lateral thrust to the hull; and each of the first and second apertures has a respective highest point, and the top of the disc swept by the propeller is located at a position higher than the respective highest points of the first and second apertures when the pleasure boat is level.

In a second aspect, there is provided a tunnel thruster for installation in a hull of a pleasure boat, wherein: the tunnel thruster includes a motor, a propeller and a tunnel; the tunnel is suitable for installation through and across the hull of the pleasure boat, from a first aperture at a first side of the tunnel thruster to a second aperture at a second side of the tunnel thruster; the propeller is mounted for rotation about a propeller principal axis within the tunnel so that, when the tunnel thruster is level, the propeller principal axis is substantially horizontal and substantially perpendicular to a disc swept by the propeller; the tunnel thruster is operable to drive water between the first and second apertures to provide lateral thrust; and each of the first and second apertures has a respective highest point, and the top of the disc swept by the propeller is located at a position higher than the respective highest points of the first and second apertures when the tunnel thruster is level.

In a third aspect, the present invention provides a pleasure boat having at least one hull and a tunnel thruster, wherein: the tunnel thruster includes a motor, a propeller and a tunnel; the tunnel is installed in the at least one hull, from a first aperture at a first position through the hull to a second aperture at a second position through the hull; the propeller is mounted for rotation about a propeller principal axis within the tunnel so that, when the pleasure boat is level, the propeller principal axis is substantially horizontal and substantially perpendicular to a disc swept by the propeller; the tunnel thruster is operable to drive water between the first and second apertures to provide thrust to the hull; and each of the first and second apertures has a respective highest point, and the top of the disc swept by the propeller is located at a position higher than the respective highest points of the first and second apertures when the pleasure boat is level.

In a fourth aspect, there is provided a tunnel thruster for installation in a hull of a pleasure boat, wherein: the tunnel thruster includes a motor, a propeller and a tunnel; the tunnel is suitable for installation in the hull of the pleasure boat, from a first aperture at a first side of the tunnel thruster to a second aperture at a second side of the tunnel thruster; the propeller is mounted for rotation about a propeller principal axis within the tunnel so that, when the tunnel thruster is level, the propeller principal axis is substantially horizontal and substantially perpendicular to a disc swept by the propeller; the tunnel thruster is operable to drive water between the first and second apertures to provide thrust; and each of the first and second apertures has a respective highest point, and the top of the disc swept by the propeller is located at a position higher than the respective highest points of the first and second apertures when the tunnel thruster is level.

Optional features of the invention will now be set out. These may be combined with any aspect of the invention, singly or in any combination, unless the context demands otherwise.

In some embodiments, the boat may be a pontoon type boat with three hulls. In this case, the hulls are parallel and extend along the full length of the pontoon boat. Each hull is typically attached to the deck of the boat, with one running along the middle (i.e. the central hull) and the other two on either side of the central hull. This arrangement results in the deck being well supported across its width. The deck may support a superstructure of any convenient form, including for example seating and helming arrangements for the boat.

The hull may have a bow region and a stern region. There may be a thruster according to an embodiment of the invention installed in the bow region or in the stern region. In a suitable embodiment, there may be a bow thruster installed in the bow region and a stern thruster installed in the stern region. This provides suitable manoeuvrability for the boat.

The tunnel of the thruster may be installed through and across the hull from the first aperture located at a first side of the hull to the second aperture at a second side of the hull.

In another embodiment, the thruster may be installed in the hull in the fore-aft direction, from a forward aperture in the hull to a rearward aperture in the hull. In this configuration, the thruster is capable of providing forwards and/or rearwards thrust for the boat.

In operation, it is intended that the entirety of each aperture is located below the waterline of the boat.

The tunnel may have a central region formed as a generally horizontal tube which accommodates the propeller. The tunnel may additionally have lateral regions which are oriented downwardly towards the respective apertures in the hull. An angle formed between a downward slope of each lateral region and the horizontal may be at least 3° in order to provide a significant effect. This angle may be greater, but increasing the angle limits the thrust (e.g. lateral thrust) provided by the thruster in view of the increasing vertical component of thrust provided by the downward slope of the tunnel. For example, the angle may be at most 45°, more preferably at most 30°.

A vertical distance between the top of the disc swept by the propeller and the respective highest point for each aperture may be at least 2cm. In other embodiments, this distance may be at least 4cm, at least 6cm, at least 8cm or at least 10cm.

The tunnel may be formed of aluminium. The tunnel may be fixed to the hull by welding, suitable processes for welding of aluminium being known to the skilled person.

The motor is typically attached to the tunnel and is located above the tunnel. A drive shaft may extend substantially vertically from the motor, via a suitable seal, to a gearbox held within the tunnel. The gearbox may include gears to transmit the rotation of the drive shaft around a right angle to drive the propeller about its horizontal axis of rotation. Considering the lateral extent of the tunnel extending between the apertures, the tunnel may have a central point coinciding with a fore-aft centre line of the hull. The gearbox may be located on one side of this central point and the propeller may be located on the opposite side of this central point. In configurations in which the thruster is arranged in the fore-aft direction, the total length of the thruster, from the forward aperture to the rearward aperture, is less constrained.

Further optional features of the present invention will be described below.

SUMMARY OF THE FIGURES

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

FIG. 1 shows a cross sectional view through a boat, taken at a cross section perpendicular to the fore-aft direction, through a bow thruster arrangement.

FIG. 2 shows an enlarged view of the bow thruster arrangement 210 indicated in FIG. 1.

FIG. 3 shows a cross sectional view through a boat, taken at a cross section parallel to the fore-aft direction, centrally along the central hull and from the side, showing a bow thruster arrangement and a stern thruster arrangement.

FIG. 4 shows a cross sectional view through a boat, taken at a cross section parallel to the fore-aft direction, from above, showing a bow thruster arrangement and a stern thruster arrangement in the central hull.

FIG. 5 shows a cross sectional view of a tunnel thruster for use with an embodiment of the invention.

FIG. 6 shows an enlarged view of part of FIG. 5 including the propeller.

FIG. 7 shows a side view of the tunnel thruster of FIG. 5.

FIG. 8 shows a top view of the tunnel thruster of FIG. 5.

FIG. 9 shows a fore-aft view from below of the pontoon hulls and base deck structure forming part of a three-pontoon hull vessel 100 according to an embodiment of the invention.

FIG. 10 shows a perspective view from below of the pontoon hulls and base deck structure forming part of a three-pontoon hull vessel 100 according to an embodiment of the invention.

FIG. 11 shows a view corresponding to FIG. 3 but with a different thruster configuration.

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.

FIG. 10 shows a perspective view from below of the pontoon hulls and base deck structure forming part of a three-pontoon hull vessel 100 according to an embodiment of the invention. The superstructure of the vessel is not shown. FIGS. 1 and 9 show different views of the same three-pontoon hull vessel. This vessel is also referred to herein as a boat or a pontoon boat.

The vessel has three elongate pontoon hulls comprising a central pontoon hull 102, port pontoon hull 104 and starboard pontoon hull 106. Each pontoon hull 102, 104, 106 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. A base deck structure is arranged at the upper sides of the pontoon hulls. The deck structure comprises an arrangement of laterally extending beams 108. These are attached to the pontoon hulls 102, 104, 106 by a corresponding arrangement of brackets 110 welded to the pontoon hulls.

Although not shown in the drawings, it is intended that a superstructure is supported on the deck structure. The superstructure may include various items arranged for user comfort and for usability of the boat. For example, there may be provided a deck overlaying the beams 108 (and which may, for example, form part of the deck structure) and providing a surface suitable for users to walk on, a perimeter wall or railing, seating, steering equipment, fishing stations, etc. At the stern of the boat is provided space for positioning an outboard motor. FIGS. 1 and 10 show a swim ladder 111 located at the stern region of the boat.

As best shown in FIG. 10, each pontoon hull 102, 104, 106 has a bow region. Each bow region comprises a forwardly tapering shape, terminating in a longitudinally extending seam 114. Arranged laterally on either side of the bow seam, at least for the central pontoon hull 102, are spray plates 116. The spray plates 116 are arranged to prevent excessive spray from projecting upwardly from the water during high-speed travel of the boat.

Each pontoon hull 102, 104, 106 typically comprises an aluminium structure. The general shape of the structure is cylindrical (circular cylindrical) with a typical maximum diameter of about 600mm. The pontoon hull comprises various compartments which may be sealed from each other via bulkheads. Some of these compartments may be open (typically opening to the top side, to allow positioning of equipment in the compartment, and access to that equipment). Others of these compartments are closed and typically are pressurised. In particular, the bow compartment at the bow region of the pontoon hull is sealed and pressurised. This allows it to withstand impact with the water, and limited impact with solid objects, without significant deformation.

As best shown in FIGS. 9 and 10, the central pontoon 102 has apertures 202, 204, 206, 208. Apertures 202, 204 are located near the bow of the boat and apertures 206, 208 are located near the stern of the boat. Together with the tunnel thruster equipment described below, the apertures 202, 204 provide a bow thruster arrangement 210 and the apertures 206, 208 provide a stern thruster arrangement 212.

FIG. 1 shows a cross sectional view through the boat, taken at a cross section perpendicular to the fore-aft direction, through the bow thruster arrangement. FIG. 2 shows an enlarged view of the bow thruster arrangement 210 indicated in FIG. 1.

FIG. 5 shows a cross sectional view of a tunnel thruster 230 for use with an embodiment of the invention. The tunnel thruster includes a motor 232, a drive shaft 234, gear box 235, a propeller 236 and a tunnel 238. The tunnel 238 is installed through and across the central hull 102 from the first aperture 204 at a first side 102A of the hull to a second aperture 206 at a second side 102B of the hull 102. The propeller 236 is mounted for rotation about a propeller principal axis 240 within the tunnel 238. When the pleasure boat is level, the propeller principal axis 240 is substantially horizontal. FIG. 6 shows an enlarged view of the part of FIG. 5 including the propeller. The propeller principal axis 240 is also substantially perpendicular to a disc 242 swept by the propeller 236, the principal axis of the disc being coaxial with the propeller principal axis 240. The disc 242 is the notional shape of the volume swept by the propeller in space and can be considered to be a cylinder of diameter equal to the diameter of the propeller and a length equal to the axial dept of the propeller.

In use, operation of the thruster to turn the propeller in a forward direction drives water through the tunnel in the direction shown by the arrows, and correspondingly through the apertures 206, 204 in the hull 102. Operation of the thruster in the reverse direction drives water through the tunnel in the direction opposite to that shown by the arrows. In this way, the bow thruster can be controlled to provide lateral thrust to the bow of the boat.

The apertures 204, 206 can each be considered to have a respective highest point 204A and 206A. This is the point for each aperture that, when the boat is level, is highest. The disc 242 swept by the propeller can similarly be considered to have a highest point 242A when the boat is level. The tunnel 238, propeller 236 and apertures 204, 206 are configured so that the top 242A of the disc 242 swept by the propeller 236 is located at a position higher than the respective highest point 204A, 206A for each aperture 204, 206. In this way, it can be assured that the entirety of each aperture 204, 206 is located below the waterline 250 of the boat, even if at least part of the propeller 236 is located above a horizontal extension 250A of the waterline traced through the hull 102 and tunnel 238. This allows the thruster to operate efficiently, without significant aspiration of water into the tunnel.

In the illustrated embodiment, the tunnel 238 has a central region 238A formed as a generally horizontal tube which accommodates the propeller 236 and the gearbox 235. The tunnel has lateral regions 238B and 238C which are oriented downwardly towards the respective apertures 204, 206. The angle 250 formed between the downward slope of the lateral regions 238B, 238C and the horizontal is typically at least 3° in order to provide a significant effect. This angle may be greater, but increasing the angle limits the lateral thrust provided by the thruster in view of the increasing vertical component of thrust provided by the downward slope of the tunnel. For example, the angle 250 may be at most 45°, more preferably at most 30°.

The tunnel may have different shapes in other embodiments, such as a curved shape.

The vertical distance between the top 242A of the disc 242 swept by the propeller 236 and the respective highest point 204A, 206A for each aperture 204, 206 is set to an amount to provide a suitable effect. For example, this distance may be at least 2cm. In other embodiments, this distance may be at least 4cm, at least 6cm, at least 8cm or at least 10cm.

The tunnel 238 may be formed of aluminium. It is typically fixed to the hull by welding, suitable processes for welding of aluminium being known to the skilled person.

As can be seen from FIG. 5, neither the drive shaft 234 of the motor nor the propeller is centrally disposed (in terms of its lateral position) with respect to the tunnel 238. It would be preferred from a thrust point of view for the propeller to be centrally disposed, in order to equalise the thrust in each direction depending on the direction of rotation of the propeller. However, in the embodiment, this would cause the gearbox to be located too far laterally. Therefore the gearbox and the propeller are located on either side of a fore-aft centre line of the hull.

FIG. 11 shows a view corresponding to FIG. 3 but with a different thruster configuration. A cross sectional view of the central hull 102 is shown. This has a single tunnel thruster 430 arranged in the bow region. The thruster 430 has a similar structure to thruster 230 described above but is arranged in a different orientation. Hull 102 in this embodiment has a forward aperture 402 cut at the base of the hull and a rearward aperture 404 also cut at the base of the hull, disposed rearwardly from the forward aperture and aligned in the fore-aft direction of the boat, which is along the base of the hull shown in FIG. 11.

As for the first embodiment described above (refer to FIG. 5), the tunnel thruster 430 includes a motor 232, a drive shaft 234, gear box 235, a propeller 236 and a tunnel. However, in this embodiment the tunnel 438 is installed lengthways along the interior of the hull, from the forward aperture 402 to the rearward aperture 404. To allow for this, the tunnel 438 of thruster 430 differs from the first embodiment in that angled tunnel sections 438B and 438C extend further downwardly in order to meet the hell and seal with the apertures 402 and 404. In this configuration, the thruster is able to provide forward (F) and rearwards (R) thrust for the boat. As will be understood, this thruster arrangement may be used in combination with the lateral thruster arrangements discussed above in order to provide additional manoeuvrability for the boat, particularly while mooring.

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%.