Support for Propulsion Apparatus for a Water-Borne Vessel, and Propulsion Apparatus Incorporating Such Support The present invention relates to a support for a propulsion apparatus for a water-borne vessel, and relates particularly, but not exclusively, to a support for a propulsion pod for mounting to the hull of a ship. The invention also relates to propulsion apparatus incorporating such supports Propulsion units known as azimuthing pods are known in which one or more pods carrying a propeller driven by an electric motor located in the pod are pivotably mounted to the hull of a ship.

Each pod is rotatable through 360° or more relative to the hull of the ship. Such arrangements are disclosed, for example, in W001/70569 and EP0590867. Electrical power and cooling fluid are supplied to each motor from the interior of the hull of the ship by means of cables passing through the joint between the corresponding pod and the hull. In this way, electrical generators can be located at convenient places inside the hull of the ship, as a result of which space in the hull is used much more efficiently than in the case of ships driven by propellers driven directly by means of an engine located inside the hull.

These known arrangements suffer from a number of drawbacks. In particular, because the pod is rotatable through 360° or more relative to the hull, it is pivotally mounted to the hull at a single location, as a result of which the joint at which each pod is mounted to the hull of the ship is subjected to significant bending moments. Another consequence of each pod being rotatable through 360° or more is that arrangements for supplying electrical power and cooling fluid to each pod are of complicated and expensive construction in order to operate over the wide range of rotation of the pods. Also, in the case of a ship having more than one pod rotatable through 360° or more, when manoeuvring at low speed, it is difficult for ship operators to intuitively ascertain how to control a ship when two pods with arbitrary helm angles are provided, which may be driving in a forward or reverse direction. Furthermore, in order to accommodate pods which are rotatable through 360°, the stern to which the pods are mounted must be relatively flat (known to persons skilled in the art as"prammed") in order to allow space for rotation of the pods. This in turn causes further disadvantages, including increased impact shocks as the vessel pitches, lessened directional stability, and greater construction time and cost than in the case of conventional sterns of V-shaped cross section.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to an aspect of the present invention, there is provided a support for a propulsion apparatus for a water-borne vessel, the support comprising:- at least one first support member adapted to support a housing of a propulsion apparatus and to be mounted to at least one second support member integrally mounted to a hull of a water-borne vessel to enable the propulsion apparatus to pivot about an axis relative to the hull, wherein at least one said first support member is adapted to be mounted to at least one said second support member at a plurality of locations separated along said axis.

By providing at least one support member adapted to be pivotably mounted to at least one second support member at a plurality of locations separated along the axis of pivoting of the propulsion apparatus relative to the hull, this provides the advantage of reducing the stress moments to which the bearings mounting the first and second support members together are subjected compared with the single point mountings of the prior art. This in turn increases the reliability of propulsion apparatus incorporating a support embodying the invention. In particular, it is a widely held belief in the art that it is necessary to be able to rotate propulsion pods through at least 360° for them to operate correctly, and that only single-point mountings are possible because the components of multiple-point mountings would therefore prevent rotation of the pods through 360°. However, the present invention provides the surprising and advantageous result that accelerated water flow generated by the propeller of at least one propulsion apparatus impinges on at least one second support member, which can generate forces in a direction transverse to the direction of travel of the vessel, and therefore assist in steering the vessel. This in turn provides the advantage of providing better manoeuvrability than in the prior art. The invention provides the further advantage that because the propulsion apparatus no longer needs to rotate through at least 360°, it can be provided with electrical power, cooling fluid and other services supplied from inside the hull of the vessel, by means of much more cost effective connections, such as cables, which are not subjected to twisting as a result of the limited angular range through which the propulsion apparatus pivots.

An edge of at least one said first support member remote from said pivot axis may be inclined relative to said axis in use.

This provides the advantage of enabling a propulsion apparatus mounted to the support to be mounted to a conventional stern of V-shaped cross section, which in turn improves the directional stability of the vessel, reduces the impact shocks to which the vessel is subjected during pitching, and reduces the cost of building the vessel.

According to another aspect of the present invention, there is provided a propulsion apparatus for a water-borne vessel, the apparatus comprising:- a housing; at least one electric motor in said housing; at least one propeller mounted to said housing and adapted to be rotated relative to said housing by means of at least one said electric motor; and a support as defined above.

In a preferred embodiment, at least one said propeller is adapted to direct water onto at least one said second support member.

This provides the advantage of enabling at least one said second support member to assist in steering of the vessel.

According to a further aspect of the present, there is provided a water-borne vessel comprising a hull, at least one propulsion apparatus as defined above, and at least one second support member, wherein at least one said first support member is pivotably mounted to at least one said second support member.

According to a further aspect of the present invention, there is provided a method of mounting a propulsion apparatus to a hull of a water-borne vessel to enable the propulsion apparatus to pivot about an axis relative to said hull, the method comprising mounting at least one first support member of a propulsion apparatus as defined above to at least one second support member mounted to said hull of said vessel at a plurality of locations separated along said axis.

The method may further comprise the step of mounting at least one second support member to said hull prior to mounting of at least one said first support member thereto.

Preferred embodiments of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:- Figure 1 is a schematic cross-sectional view of a propulsion apparatus of a first embodiment of the present invention, mounted to a hull of a ship; Figures 2a to 2d are schematic perspective views of the apparatus of Figure 1 ; Figures 3a to 3c are schematic views of manoeuvres using the apparatus of Figures 1 and 2; Figure 4a is a schematic side view of a propulsion apparatus of a second embodiment of the present invention; Figure 4b is a rear view of the propulsion apparatus of Figure 4a; Figure 4c is a plan view of the propulsion apparatus of Figure 4a; Figure 4d is a side perspective view of the propulsion apparatus of Figure 4a; Figure 5 is a schematic side view of a propulsion apparatus of a third embodiment of the invention; and Figures 6a and 6b show a comparison of stern forms used with the embodiment of Figure 5 and with conventional azimuthing pods.

Referring to Figures 1 and 2, a propulsion pod 2 for mounting to a hull 4 of a ship 6 has a housing 8 containing an electric motor 10 for driving a propeller 12 via propeller shaft 14 mounted to the housing 8 by means of bearings 16,18. As will be appreciated by persons skilled in the art, a pod 2 will typically be mounted to each side of the rear of the hull 4.

A hydrodynamic lifting body 20 is integrally mounted to the hull 4 of the ship 6, and has a mounting part 22 integrally formed therewith. The mounting part 22 contains a bearing 24 for pivotably supporting the pod 2. A further hydrodynamic lifting body 26 is integrally attached to the housing 8 of pod 2, for example by welding, and has a tubular part 28, a lower part of which passes through connecting part 22 and bearing 24, and an upper part of which is mounted to mounting part 30 on hull 4 via bearings 32,34 so that second lifting body 26 can pivot relative to first lifting body 20 about pivot axis 36. Tubular part 28 also serves as a transfer duct for electrical power and coolant fluid, which are delivered by means of cables shown schematically at 38 for powering and cooling electric motor 10. The second lifting body 26 can rotate through approximately 125°, i. e. inboard up to 35° and outboard up to 90°.

The operation of the apparatus shown in Figures 1 and 2 will now be described.

The electric motor 10 is operated by means of cables 38 connected to a source of electrical power and coolant fluid located inside the hull 4 of ship 6. As the propeller 12 rotates with shaft 14 relative to housing 8, accelerated water flow is caused to flow rearwards from propeller 12 in the direction of arrow A to drive the pod 2 and the ship 6 forwards in the water. The forward movement of pod 2 imposes a forward directed force on bearing 24 and bearings 32,34, but the separation of bearings 24,32, 34 results in significantly smaller torque acting on the connection between the hydrodynamic lifting bodies 20,26 than is the case in prior art pods.

In order to manoeuvre the ship 6, the pod 2 is pivoted about axis 36 relative to hydrodynamic body 20. As a result, accelerated flow driven by propeller 12 in the direction of arrow A impinges on a larger cross-sectional surface of hydrodynamic body 20, which thereby assists in manoeuvring of the ship 6.

Referring to Figures 3a to 3c, a series of manoeuvres for a ship 6 having two propulsion pods 2 as shown in Figures 1 and 2 are shown. Firstly, as shown in Figure 3a, a turning manoeuvre for a ship having both propulsion apparatus 2 initially oriented to travel straight ahead (Figure 3a (i) ) is initially achieved by rotating both apparatus 2 through the same angle relative to the hull 4, as shown in Figure 3a (ii). A greater helm angle is achieved by only rotating the apparatus 2 arranged on the outside of the curve as shown in Figure 3a (iii).

A stopping manoeuvre is shown in Figure 3b, in which the two propulsion pods 2 are inclined outwardly of the direction of travel by the same angle.

Referring now to Figure 3c, a crabbing manoeuvre is achieved by rotating one of the propulsion pods 2 through 90° to operate as a transverse thruster, and operating the other pod 2 to control longitudinal position. It is found that this arrangement has the advantage of being much more intuitive to operate compared with prior art propulsion arrangements.

Referring to Figure 4, in which parts common to the embodiment of Figures 1 to 3 are denoted by like reference numerals but increased by 100, a propulsion pod 102 of a second embodiment of the present invention has active pitch control surfaces 140 pivotally mounted on either side of hydrodynamic lifting body 120. Pitch of the ship 6 is controlled by pivoting the control surfaces 140 relative to lifting body 120 about a generally horizontal axis. The control surfaces 140 can also be used to control pitch and roll simultaneously.

Figure 5, in which parts common to the embodiment of Figures 1 to 3 are denoted by like reference numerals but increased by 200, shows a propulsion pod of a third embodiment of the invention.

The pod 202 has a lifting body 226 integrally mounted to pod housing 208, the lifting body 226 having an inclined edge 250 on a side thereof remote from its pivot axis. As shown in Figure 6b, this allows the pod 202 to be mounted to a conventional stern 260 having a generally V-shaped cross section defining a stabilising fin 262, as opposed to a prammed stern as shown in Figure 6a.

This in turn improves the directional stability of the vessel compared with a vessel having a prammed stern, while also reducing the impacts to which the stern is subjected during pitching and reducing the cost of building the vessel.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the inventions as defined by the appended claims.