GB2554045A

GB2554045A - Boat auxiliary propulsion unit

Info

Publication number: GB2554045A
Application number: GB1610196.6A
Authority: GB
Inventors: Simpson Benjamin
Original assignee: Hush Craft Ltd
Current assignee: Hush Craft Ltd
Priority date: 2016-06-10
Filing date: 2016-06-10
Publication date: 2018-03-28
Also published as: GB201610196D0

Abstract

A boat auxiliary propulsion unit 10 adapted to be connected to the outside of a boat hull, preferably at the aft end and preferably below a swimming platform at the transom of the boat. The unit comprises a watertight housing adapted to be retrofitted to an existing hull, an electric motor within or connected to the housing, a propeller 22 connected to and driven by the motor to propel a boat and a battery 26 able to store electrical power and supply it as required to the electric motor. The propeller 22 may have a silencer and may protrude from a cut away section 24 of a base-wall 17 of the housing. The unit preferably has neutral buoyancy and a connection in the housing to interface with an external electric power system. The housing can contain means to alter the speed or direction of thrust of the propeller and it may also have a removable lid 18. A generator 27 may also be located in the housing to supply electricity to the batteries or power the motor, the generator itself may be connected to an external fuel supply and breather.

Description

(54) Title of the Invention: Boat auxiliary propulsion unit Abstract Title: Boat Auxiliary Propulsion Unit (57) A boat auxiliary propulsion unit 10 adapted to be connected to the outside of a boat hull, preferably at the aft end and preferably below a swimming platform at the transom of the boat. The unit comprises a watertight housing adapted to be retrofitted to an existing hull, an electric motor within or connected to the housing, a propeller 22 connected to and driven by the motor to propel a boat and a battery 26 able to store electrical power and supply it as required to the electric motor. The propeller 22 may have a silencer and may protrude from a cut away section 24 of a base-wall 17 of the housing. The unit preferably has neutral buoyancy and a connection in the housing to interface with an external electric power system. The housing can contain means to alter the speed or direction of thrust of the propeller and it may also have a removable lid 18. A generator 27 may also be located in the housing to supply electricity to the batteries or power the motor, the generator itself may be connected to an external fuel supply and breather.

1/4

1206 17

2/4

1206 17

3/4

1206 17

Figure 7

4/4

.i.-V.’··

-1 Boat Auxiliary Propulsion Unit

The present invention relates to boat auxiliary propulsion units. In particularly it relates to a boat auxiliary propulsion unit adapted to be fitted to the outside of a boat hull.

Boats, especially motor driven leisure craft, have a main propulsion unit such as a combustion engine driven by an appropriate energy source such as diesel. On boats above a certain size, such an engine is usually mounted inboard and is coupled to an external drive mechanism such as a propeller or water jet. Such a main propulsion unit is suited to operating over prolonged periods, but uses a nonrenewable resource (e.g. diesel) and is configured to operate best at higher speeds and may have impaired efficiency at low speed operation. Also at low speeds the main engine can be disproportionately noisy.

In certain places such as lakes and inland waterways there are boat speed limits and to abide by these a boat must travel at potentially well below its optimal speed. This can be noisy and fuel inefficient. In addition, a journey may be short such that the main engine may not have time to reach its optimum operating parameters (e.g. engine temperature) before it is switched off the journeys this leads to further inefficient or deleterious operation of the engine.

Alternative motive power mechanisms such electric motors are available but these have different drawbacks and are therefore not normally fitted to boats above a certain size. Further to retrofit a sufficiently powerful motor to an existing boat would entail a significant expense and technical complexity.

It is an aim of the present invention to provide an auxiliary propulsion unit for a boat, which unit may be fitted to the outside of the boat hull either at manufacture or

-2retrofitted later. That propulsion unit will be able to drive the boat forward at a relatively low speed quietly and efficiently without use of thrust from the main boat engine. This permits a hybrid drive arrangement that enhances operation efficiency at various speeds.

According to the present invention there is provided a boat auxiliary propulsion unit adapted to be connected to the outside of a boat hull, the propulsion unit comprising:

- a housing that is watertight and which is adapted to be retrofitted to an existing hull in such a way that it is at least partially below the waterline;

- an electric motor within or connected to the housing;

- a propeller, connected to the motor such that in use it is located below the waterline and driven by the electric motor to propel the boat; and

- a battery that will store electrical power and supply it as required to the electric motor.

In the context of this application the term hull has its normal meaning and includes that part of a boat that locates in the water. It also includes parts connected to or forming part of the main part of a hull, such as a swimming platform, that are appropriately positioned relative to the water. The auxiliary propulsion unit is able to be easily retro-fitted to existing boats but can also be included at initial manufacture without any need to alter the hull design or the internal configuration. This makes its inclusion into existing boats either at commissioning or later on a simple and cost effective operation.

The unit may have an electrical power interface that may permit supply of power from any source external source. That source could be the electrical system on the boat which might include a generator on the boat or forming part of the main engine.

-3In this way the battery could be charged whilst the main engine is running so that it has power when the auxiliary propulsion unit is needed. The power source could also be a shore based power supply, so that the battery will charge when the boat is moored and connected to the electricity network. The battery may be powered by renewable charging means such as wind and solar power whilst the boat is not in use. For example, the housing could include one or more solar panel (ideally on an upper surface) adapted to supply current to the battery.

The unit may also contain a generator within the housing that may be adapted to supply electrical power to the battery and or the motor direct. Such a generator could be connected to an external fuel line or may have a fuel supply within the housing. The generator may have a connection to a breather tube passing out of the housing that permits exchange or air and or exhaust gasses. The generator may be adapted to operate automatically if the battery stored energy drops too low. The generator may also be adapted to supply electrical power to external boat systems through the electrical power interface.

In order that the unit does not affect the trim of a boat on which it is mounted it is desirable that the auxiliary propulsion has neutral buoyancy. That buoyancy may be neutral overall or may be neutral relative to the amount by which it is below the waterline. The unit may have buoyancy adjustment means to allow the buoyancy of the unit to be adjustable to permit variable mounting heights or alterations of boat trim.

The size and storage capacity of the battery(s) may be altered to suit the requirements of operation. It has been found that an ability to drive the boat at a speed of up to about 8 knots for a period of up to about 1-4 hours is convenient. The disposition of components within the housing may be such that it remains broadly balanced with an even weight distribution.

-4The propulsion unit may be provided with means to alter the speed and direction of thrust of the propeller. For example, the rotational speed and direction of the motor and or the gearing of any coupling between the motor and the propeller may be adjustable. Such means may be provided within the housing. The housing can then be mounted in a fixed orientation yet the orientation of the propeller altered to provide manoeuvrability. Control of this may be linked to the boat’s steering system such that the helmsman may control a boat being driven by the auxiliary propulsion unit in the same or broadly similar way to normal operation. Remote connection or control means may be provided to permit control from the normal helm position.

The housing may have a base wall, and that base wall may have a cut-away or recessed section, which is in line with the propeller and its direction of action. This permits the propeller to sit closer and more snuggly under the lower edge of the unit. The cutaway may be tapered to permit a range of angles of the propeller relative to the housing. To reduce noise a silencer may be provided on or adjacent the propeller.

The housing may have a lid or other opening that may be removed to provide access to the contents. This would permit maintenance and repair. Ideally this unit is located on a boat in such a position that the lid or other opening is above the waterline and may be accessed whilst the boat is floating.

According to the present invention there is also provided a boat having an auxiliary propulsion unit as defined herein mounted to the hull. The propulsion unit is ideally mounted at the aft end of the hull. Preferably the hull has a transom and the unit is mounted to the rear of the transom. At least part of the housing is below the waterline at a speed at which the unit is designed to operate. The body may be shaped to reduced drag. Ideally the unit locates at the rear of the hull, preferably behind and above the main propeller. The location behind the transom ensures that the unit is out

-5of the way and so does not cause excessive drag, especially in normal operation of the main engine. The unit is particularly well suited to being mounted below a swimming platform at the transom of the boat.

The housing may be sealed such that in normal use water cannot enter inside. 5 An openable and resealable lid may be provided to permit access to the interior as required.

In order that it be better understood, but by way of example only various embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a side view of a first embodiment of auxiliary propulsion unit according to the present invention;

Figure 2 is a rear view of the auxiliary propulsion unit of Figure 1;

Figure 3 is a rear perspective view of the auxiliary propulsion unit of Figure 1; Figure 4 is a partially cut-away rear view of the same embodiment similar to

Figure 2;

Figure 5 is a partially cut-away perspective view similar to Figure 3;

Figure 6 shows the auxiliary propulsion unit of Figures 1 - 5 mounted on the hull of a boat at the rear.

Figure 7 is a cut-away view of a second embodiment of auxiliary propulsion 20 unit according to the present invention; and

Figure 8 is a series of images of an auxiliary propulsion unit according to the present invention being retro-fitted to a boat.

Figures 1-6 show the same first embodiment of auxiliary propulsion unit.

Figures 1-3 show various external views and Figures 4 and 5 show similar views 25 partially cut-away to show the contents thereof. In Figure 6 the propulsion unit is

-6shown mounted to the stern of a boat. The present invention will be described with reference to all of these Figures simultaneously.

An auxiliary propulsion unit generally indicated 10 is shown in the Figures. This comprises a rectangular housing 12 formed from an appropriate material such as metal, plastics material and fibre reinforced resin. The housing generally comprises a container defined by the four vertical walls (namely, two side walls 14, a rear wall 15 and a front wall 16) and a base wall 17. A motor is provided inside a watertight pod attached to the lower wall 17. The motor is coupled to a propeller 22 at the rearward end of the motor pod. The lower wall 17 has a cut-away portion 24 into which the blades of the propeller 22 extend as they rotate. The cut-away portion is wide enough to permit the motor pod 20 and propeller 22 to rotate about a generally vertical axis to alter the thrust vector and direction of propulsion.

A removable lid 18 is located on and connected to the upper edges of the front, rear and side walls (14, 15, 16). Appropriate sealing means are provided between the lid and housing and at any point where parts pass into or out of the housing. Placing the lid 18 on the rest of the unit closes the housing to seal the contents and to make it watertight. In this embodiment the upper surface of the lid would form part of the deck of a swimming platform and is, therefore, appropriately configured. This embodiment shows it carrying a wooden decking inlay to match that around.

As can best be seen in Figures 4 and 5, the inside of the housing 12 contains a battery assembly 26 adapted to store electrical charge in order to power the motor as desired. A generator 27 is mounted in a damped way using springs 28 to mitigate vibrational noise during operation. If the generator operates it can supply electrical power to the battery and the motor 20. The battery may be charged by that or by connection to an external power source through a power connection interface

-730. Although not visible, this could be linked by appropriate cabling or watertight plug formations as are known in the art.

The motor casing 20 and propeller are, as mentioned, mounted for rotation about a generally vertical axis. A mounting post 32 extends upwards into the housing and is connected to a steering assembly 34 by which rotation of the motor 20 can be achieved. The unit also includes a control mechanism to alter the power output of the motor in order to alter the speed and direction of rotation of the propeller. This allows connection, either physically or wirelessly, to a helm or control console on the boat for operation by a helmsman.

As can be seen in Figure 6, the unit 10 is mounted to a boat 40 below a rearwardly extending platform 42. This platform would comprise a normal swimming or boarding platform frequently provided on such craft. The platform 42 extends rearwardly from the transom 44. By locating the unit 10 in this position it is substantially behind the main part of the hull such that in the normal operation of the boat’s main engines the unit will be substantially out of the water and certainly not causing any significant drag. However, at low speed when the hull of the boat 40 sits lower into the water the unit will be positioned such that the propeller 22 is below the waterline. At normal low speed operation the waterline would normally be somewhere between the upper edge of the propeller as shown in Figure 6 and the lower edge of the platform 42.

When not in use the auxiliary propulsion unit 10 would be receiving electrical current from an external source or the generator. This external source may comprise the boat’s main electrical system powered by operation of the main engine, or an external generator. It could also be shore based power, for example in a marina or other mooring location. It could additionally or alternatively comprise micro-generation

-8systems as a wind turbine or solar panel mounted on the unit or on the boat and wired to the unit. This power supply would charge the internal battery assembly 26 and power regulation means would ideally be provided to ensure optimum charging and prevent damage to the batteries. When the boat is operating under the power of the main engines the auxiliary propulsion unit would not be functioning. However, at the point low speed operation is required the main engine could be turned-off and instead the auxiliary propulsion unit operated to provide motion to the boat. In certain circumstances, for example manoeuvring a boat around a harbour or on waterways where low speed limits exist, the unit would drive the boat forward and permit steering but in a low noise and low environmental impact mode.

The unit could be integrated with the boat’s navigational and control system such that below certain speeds the main engines could cease to operate with thrust being taken over by the auxiliary power unit, whilst it has sufficient charge to operate. Should its charge drop below a required threshold level the generator 27 or main engine could be operated simply to provide the charge, or the main engine could progressively take over thrust. Likewise, if a demand was placed on the system for greater speed than was capable from the auxiliary power unit the main engines can be initiated to provide that thrust.

The auxiliary power unit is a sealed unit such that the components within the housing are protected from submersion and environmental conditions. In addition, the housing will, as far as possible, have a neutral buoyancy at its required level of submersion. This ensures that it does not affect the overall balance or trim of the boat to which it is retro-fitted. In the alternative, the weight of the unit to a boat not designed with its inclusion could adversely affect the performance or safety of the boat.

-9Figure 7 shows a second embodiment in which there is no generator, but is other ways similar to the first embodiment. Like parts will be given the same reference numerals. In this embodiment there are more batteries 26 and no generator so all power for charging comes from outside the unit. Also the profile of the lower part of the housing is different in that it is stepped to fit between twin propellers or outdrives. A mounting post 32 and steering assembly 34 are more clearly shown in this figure.

Figure 8 has 5 images (A to E) which show a series of steps in the retrofitting of a first embodiment of unit 12 to a boat 40. 8A shows a boat 40 with a bathing platform 42. In 8B a rectangular opening 50 has been cut through the bathing platform 10 42, closely to accommodate a unit 12 that is lowered into the opening as shown in 8C and then securely fixed in place and sealed as required. It is also connected as required to the boat’s power and control systems (not shown). Once fully lowered in to place (as shown in 8D) the lower part of the unit 12 and propeller 22 project below the platform 42 and into the water (which is not visible). In 8D the lid 18 is shown not on and this permits access to the contents. In 8E the lid is shown in place on the housing to give the appearance and functionality of a complete deck.

Claims

1. A boat auxiliary propulsion unit adapted to be connected to the outside of a boat hull, the propulsion unit comprising:

5 - a housing that is watertight and which is adapted to be retrofitted to an existing hull in such a way that it is at least partially below the waterline;

- an electric motor within or connected to the housing;

- a propeller, connected to the motor such that in use it is located below the waterline and driven by the electric motor to propel the boat; and 10 - a battery that will store electrical power and supply it as required to the electric motor.

2. A boat auxiliary propulsion unit as claimed in claim 1 which has neutral buoyancy.

3. A boat auxiliary propulsion unit as claimed in claim 1 wherein there is provided 15 a connection in the housing to interface with an external electric power system.

4. A boat auxiliary propulsion unit as claimed in any of the preceding claims in which there is provided within the housing means to alter the speed of the propeller and or the direction of thrust of the propeller.

5. A boat auxiliary propulsion unit as claimed in any of the preceding claims 20 wherein the housing has a base wall and that base wall has a cut-away section aligned with the propeller.

6. A boat auxiliary propulsion unit as claimed in any of the preceding claims wherein a silencer is provided on the propeller.

7. A boat auxiliary propulsion unit as claimed in any of the preceding claims 25 wherein the housing has a lid that may be removed to provide access to the contents.

-11

8. A boat auxiliary propulsion unit as claimed in any of the preceding claims which also includes a generator contained in the housing and adapted as required to supply electricity to charge the batteries and/or power the motor.

9. A boat auxiliary propulsion unit as claimed in claim 8, wherein the generator 5 within the housing is connected to one or more of an external fuel supply and an external breather.

10. A boat auxiliary propulsion unit as claimed in claim 1 and substantially as herein described and illustrated in the accompanying drawings.

11. A boat having an auxiliary propulsion unit as defined in any of the preceding

10 claims mounted on its hull at the aft end thereof.

12. A boat as claimed in claim 11 wherein the auxiliary propulsion unit is mounted below a swimming platform at the transom of the boat.

Intellectual

Property

Office

Application No: