EP4034459B1

EP4034459B1 - Apparatus for the variation of the operating positions of an oleodynamic azimuth stern mounted on a motorized vessel

Info

Publication number: EP4034459B1
Application number: EP20790386.5A
Authority: EP
Inventors: Massimo Labruna; Leonardo MOLLO
Original assignee: Labruna AS Srl
Current assignee: Labruna AS Srl
Priority date: 2019-09-23
Filing date: 2020-09-20
Publication date: 2023-11-29
Anticipated expiration: 2040-09-20
Also published as: EP4034459C0; EP4034459A1; IT201900017012A1; WO2021059105A1

Description

Field of the invention

The scope of this invention generally relates to the sector of marine propulsion systems mounted on the stern of vessels.
More specifically, the invention relates to oleodynamic means for said marine propulsion systems suitable for making it possible to vary the operating positions of the stern unit.
Even more specifically, the invention provides an optimized technological solution for an apparatus used to connect and support the stern unit of a vessel capable of allowing for its movement, with the purpose of achieving numerous operating arrangements of propulsion.

Description of the prior art

An outboard motor is a marine engine which generally adopts a two-stroke or four-stroke explosion engine, be it a gasoline engine or a diesel engine, or an electric motor or other known hybrid motors, manufactured and used for being mounted in the transom of a vessel. Said motor makes the power transmitted to a (fixed) rotary shaft coming out from the transom, available.
Outboard motors comprise an engine external to the hull, supported by an external skeg (stern drive) comprising the transmission members used to transfer motion to a propeller; the direction of a vessel's movement can be modified by rotating the skeg, without using a rudder as with inboard motors.
In an outboard motor, the skeg can be adjusted horizontally, either rightwards or leftwards, in order to direct the hull, but it can also be adjusted vertically, either downwards or upwards, in order to obtain a tilt effect and, above all, to set the trim position which, besides providing transportation and safety in case of collisions, also allows to modify performances, i.e. the trim of propulsion or alternatively, to take it out of the water during a stop, to haul the boat, or to make repairs.
An adjustment of the trim of said motors is necessary to reduce or increase friction with the water in order to obtain an optimum trim during navigation; if friction is decreased, i.e. the propeller of the motor is raised upwards to try and make it come out from the water, the boat will tend to plane and increase its own speed by some knots, an operation that results in also consuming less fuel because of a reduced friction.
In order to make the three orthogonal rotations (the motor shaft one, the swinging one for steering purposes, and the trimming one) simultaneously possible, it is necessary that all of the three axes of rotation of the skeg cross one point, which is the central point of a connection and movement joint.
In the sector of boats, numerous connection systems and devices are known for outboard motors, which allow to adjust the tilt and raising/lowering positions of a propeller in order to achieve the advantages of the principles as mentioned here above.
Said systems comprise propeller raising and lowering devices, which include one or more tilt cylinders basically used for raising the propeller out of the water and lowering it into the water, and one or several trimming cylinders basically used for changing the angle of the propeller underwater.
Numerous patent documents are known which illustrate a variety of configurations for said systems and devices.
Document JP19840056268 discloses a number of embodiments of a hydraulically controlled unit equipped with cylinders for varying tilt and trim of outboard motors. In all of these embodiments, the rods of the pistons of the tilt and trim cylinders are arranged in such a way that they are out of the water whenever the outboard motor is tilted upwards. Some embodiments use such connection system that the external unit will be displaced so as not to significantly increase the actual length of the associated ship whenever the external unit is tilted upwards.
Document US19950486527 discloses a marine propulsion device comprising a tilt/trimming and raising regulation mechanism which allows to vary trim of transmission by keeping a determined angle. The regulation mechanism includes a four-bar linkage system provided with upper leverages comprising a pair of tilt and trim actuators, which vary the length of the upper linkage so as to adjust stern transmission trim and upwards tilt, and lower leverages comprising two flexible joints of a transmission gear set. One of these flexible joints is coupled with a lower drive unit in the stern unit which enables the lower leverages to rotate without modifying the trim angle of the lower transmission unit. Document US20010806719 discloses a vertical trim variation system for an outboard/inboard marine motor comprising a stern plate and arms whose first ends are attached to the plate of the transom and the second ends are attached to a plate connected to the motor.
Document EP0251995A2 relates to a naval propulsion plant that provides a pair of heat engines that drive two independent pumps. In turn these pumps drive two hydraulic motors with which two propellers are solid in rotation. A suitable distributor makes it possible to idle one of the two propellers in case of a breakdown, or to operate both with one of the heat engines.
Upon analyzing the status of the art, it is apparent that none of the systems comprises a regulation mechanism capable of regulating trim, raise, and rotation of an oleodynamic azimuth stern that allows to vary its trim via an oleodynamic transmission directly connected to the engine unit of a vessel.
No devices are known either that allow for a propeller, hydraulically fed by a pressurized circuit of a vessel, to perform different functions, such as, for example, that of an outboard motor or that of a surface propeller, and to vary its trim without being obliged to stop it.
An object of the present invention is to provide a connection and support apparatus for a stern marine propulsion unit provided with oleodynamic means (oleodynamic azimuth stern or azipod) capable of making it possible to vary the operating positions of the unit and allowing its movement in order to obtain numerous operating trims for the propellers. More specifically, an object of the present invention is to provide a propulsion system for vessels that is capable of providing the following movement options for a stern unit either individually or simultaneously:

tilt movement, i.e. raising and lowering of the stern unit, according to the direction of the vertical axis of the propeller shaft,
trim movement, i.e. tilt of the stern unit through a rotation of the propeller around an axis transversal to the propeller shaft,
rotation from 0° to 360° of the azimuth stern around the axis of the shaft.

A further object of the present invention is to provide an apparatus that allows to use an oleodynamic azimuth stern of a vessel as an outboard motor or as a surface propeller. For such purposes, the present invention provides an apparatus for varying the operating positions of an oleodynamic azimuth stern mounted on a motorized vessel.

Summary description of the invention

The apparatus according to the present invention comprises an oleodynamic kinematic mechanism interposed between and removably connected to an oleodynamic azimuth stern provided with a torpedo and a propeller, mounted on a motorized vessel.
Said kinematic mechanism comprises an attachment plate removably connected to the transom of the vessel, provided with oleodynamic connection means, and an attachment plate jointly connected to the rotary oleodynamic joint of the propeller.
The kinematic mechanism also comprises hollow tubular oleodynamic means for passage of a pressurized liquid coming from the engine unit of the vessel, whose ends are connected to cylindrical means capable of rotating in circular seats of the attachment plates removably connected to the transom of the vessel and to the rotary oleodynamic joint of the propeller.
Further cylindrical elements of the kinematic mechanism are connected to a cylindrical mechanical joint operating as an articulated joint for a pair of oleodynamic means, consisting of cylinders and pistons, connected in such a way as to possibly rotate in further circular seats of the attachment plates removably connected to the transom of the vessel and to the rotary oleodynamic joint of the propeller.
The activation of said cylinder- and piston-based oleodynamic means triggered by the oleodynamic fluid passing through the oleodynamic connection means makes it possible for the kinematic mechanism to rotate, thus providing tilt and trim movements of the oleodynamic azimuth stern either individually or simultaneously.
The rotation of the propeller around its own vertical axis takes place by way an oleodynamic motor supplied by means directly connected to the removable plate and placed above the rotary joint that drives a gear mechanism jointly connected to the rotary joint.
The rotary joint makes it possible for oil to reach the oleodynamic motor located in the torpedo under any angles of rotation of the latter.
By virtue of the foregoing, the apparatus according to the present invention makes it possible:

to simultaneously (as well as individually) raise, lower, trim, and rotate the azimuth stern of a vessel;
to move the azimuth stern without being obliged to stop the propeller;
to position the propellers of the azimuth stern in such position as to provide a driving propulsion as well as a reverse propulsion;
to transmit the torque of the engine mounted onboard the vessel to the transmission members of the azimuth stern, without losing production efficiency, via the pipes through which the pressurized oleodynamic liquid is fed, which are parts of the oleodynamic kinematic mechanism;
to easily and quickly connect the apparatus to the transom of the vessel by way of quick release mechanical and hydraulic attachments;
to use the oleodynamic azimuth stern as an outboard motor or as a surface propeller. According to the foregoing, the proposed apparatus makes it possible to overcome the various criticalities featuring the present status of the art and represents a load of technologies aiming at a real technological innovation in the sector of marine propulsion systems mounted at the sterns of vessels.

Brief description of the drawings

Further features and advantages of the invention will be more apparent in the light of the detailed description of one, preferred but not exclusive, embodiment of the apparatus for varying the operating positions of an oleodynamic azimuth stern of a motorized vessel, which is illustrated for explanatory non-limitative purposes, with reference to the attached drawings, wherein:

figure 1 shows an overall axonometric view of an oleodynamic azimuth stern equipped with the apparatus,
figure 2 shows a side view of the apparatus of figure 1,
figure 3 shows a front view of the apparatus of figures 1 and 2 with the attachment plate for attaching to the vessel in the foreground and the propeller in the background,
figure 4 shows an overall axonometric view of the pre-assembled azimuth stern of figure 1, the propeller having been removed,
figure 5 shows a detailed side view of the apparatus for varying the operating positions of the azimuth stern of the preceding figures, the torpedo having been removed,
figure 6 shows a detailed top view of the apparatus of figure 5,
figure 7 shows an overall axonometric view of the pre-assembled apparatus of figures 5 and 6, the torpedo and the propeller shaft having been removed,
figure 8 shows two overall side views of the oleodynamic azimuth stern equipped with the apparatus of the preceding figures, in a raised position a) (torpedo partially rising out), and a lowered position b) (torpedo completely submerged) respectively,
figure 9 shows two overall side views of the oleodynamic azimuth stern equipped with the apparatus of the preceding figures in a counterclockwise trimming position a) (torpedo's propeller in an awash position) and b) in a clockwise trimming position (torpedo's propeller submerged),
figure 10 shows two overall side views of the oleodynamic azimuth stern equipped with the apparatus of the preceding figures in a position a) wherein the axis of the shaft is rotated by 90° (torpedo's propeller transversal to the longitudinal axis of the vessel) and in a position b) wherein the axis of the shaft is rotated by 180° (torpedo's propeller driving).

Description of one preferred embodiment of the invention

A motorized vessel N is equipped with an azimuth stern A according to the present invention, shown in figures 1, 2, and 3 in a preferred embodiment thereof and in a pre-assembled condition in figure 4, provided in turn with a torpedo S, a propeller E and an oleodynamic rotary joint 3 mounted on a shaft T.
The stern is provided with an apparatus, a preferred embodiment of which is shown in figures 5 and 6 and in a pre-assembled condition in figure 7, which consists of an oleodynamic kinematic mechanism 1 removably connected to and interposed between an attachment plate 2, removably connected to the transom P of the motorized vessel N, and an attachment plate 4 jointly connected to the rotary oleodynamic joint 3.
The kinematic mechanism 1 of the apparatus consists of oleodynamic means 100 comprising at least one pair of hollow tubular elements 11, arranged parallel to each other, for passage of a pressurized liquid from the engine unit of the vessel N, whose ends 111, 112 are jointly connected to hollow cylindrical elements, 14 and 15 respectively, provided with cylindrical seats 141, 151 coaxially connected in such a way as to possibly rotate around an oleodynamic cylindrical pin 5 and around an oleodynamic cylindrical pin 6 respectively.
Said oleodynamic cylindrical pins 5 and 6 are in turn coaxially connected in such a way as to possibly rotate within circular seats 21, 41 respectively of the attachment plate 2 removably connected to the transom P of the vessel and of the attachment plate 4 of the oleodynamic rotary joint 3.
The kinematic mechanism 1 is also provided with a first pair of tubular elements 12, whose ends 121, 122 are jointly connected to the hollow cylindrical element 14 and to a mechanical cylindrical joint 16 respectively, the latter being provided with a cylindrical seat 161 for housing a cylindrical pin 162, and a second pair of tubular elements 13, whose ends 131, 132 are jointly connected to the hollow cylindrical element 15 and to the mechanical cylindrical joint 16, respectively.
A first pair of oleodynamic means 17 is arranged in the kinematic mechanism, each pair being provided with a cylinder 171 an end of which includes a circular seat 171.1 connected in such a way as to possibly rotate around the pin 222 coaxially inserted in the circular seats 221 of the mechanical joint 22 of the plate 2 and with a piston 172 provided at one end of a circular seat 172.1 connected in such a way as to possibly rotate around the cylindrical pin 162 of the mechanical cylindrical joint 16.
The kinematic mechanism 1 also includes a second pair of oleodynamic means 18, each provided with a cylinder 181 having one end of a circular seat 181.1 connected in such a way as to possibly rotate around the pin 422 coaxially inserted in the circular seats 421 of the mechanical joint 42 of the plate 4, and with a piston 182 provided at one end of a circular seat 182.1 connected in such a way as to possibly rotate around the cylindrical seat 162 of the mechanical cylindrical joint 16.
Oleodynamic connection means 200 connected to the attachment plate 2 removably connected to the transom P of the vessel N make it possible to supply a pressurized oleodynamic fluid coming from the engine unit to the oleodynamic kinematic mechanism 1 and to the oleodynamic means 30 for driving a gear mechanism 31 integral with the rotary joint 3.
Said elements 14, 141, 5, 21 make up an oleodynamic cylindrical joint 500, 600 featuring an axis of rotation Y, whereas the elements 15, 151, 6, 31 make up an oleodynamic cylindrical joint 600 featuring an axis of rotation Z.
The activation of at least one of said rotations is triggered by the oleodynamic fluid passing through the connection means 200 and at least one pair of said oleodynamic means 17, 18; said connection means 200 consist of quick-release mechanical and hydraulic attachments.
Said oleodynamic means 17, 18 are piston- and cylinder-based oleodynamic means whose pistons are opposed so as to rotate around one and the same pin at different angles.
For said purpose, the circular seats 172.1, 182.1 of the pistons 172, 182 respectively of said means 17, 18 respectively are arranged in such a way as to rotate coaxially with the pin 162 of the mechanical joint 16, whereas the circular seats 171.1, 181.1 of the cylinders 171, 181 respectively of said means 17, 18 respectively are arranged in such a way as to rotate coaxially with the pins 222, 422 respectively of the mechanical joint 22, 42 respectively.
Figure 8 illustrates the activation of the oleodynamic means 17 supplied by the oleodynamic fluid passing through the connection means 200, 500, which determines a rotation of the oleodynamic kinematic mechanism 1 around the Y axis of the oleodynamic cylindrical pin 5 and the consequent raising or lowering of the oleodynamic azimuth stern; the two overall side views show the oleodynamic azimuth stern provided with the apparatus in a position a) whereby it is raised (torpedo partially rising out) and in a position b) wherein it is lowered (torpedo totally submerged) respectively; a rotation of the oleodynamic kinematic mechanism 1 around the Y axis can take place by way of an angular variation, for example by approximately 44°, split as follows: from 0° to 14° clockwise and from 0 to 30° counterclockwise.
Figure 9 illustrates the activation of the oleodynamic means 18 supplied by the oleodynamic fluid passing through the connection means 200, 500, 100, 600 which determines a rotation of the oleodynamic azimuth stern 1 around the Z axis of the oleodynamic cylindrical pin 6 and the consequent trimming of the oleodynamic azimuth stern; the two overall side views show the oleodynamic azimuth stern provided with the apparatus in a counterclockwise trimming position a) (torpedo's propeller rising off) and in a clockwise trimming position b) (torpedo's propeller submerged).
Rotation of the oleodynamic azimuth stern A around its own vertical axis X takes place by way of an oleodynamic motor 30, arranged above the rotary joint 3, directly supplied by the connection means 200; the oleodynamic motor 30 triggers the activation of a gear mechanism 31 integral with the rotary joint 3 and a rotation from 0° to 360° around the X axis of the oleodynamic azimuth stern A.
The rotary joint makes it possible for oil to flow to the oleodynamic motor placed in the torpedo under any angles of rotation of the torpedo.
The activation of the oleodynamic motor 30 supplied by the oleodynamic fluid passing through the connection means 200 determines a rotation of the oleodynamic kinematic mechanism 1 around the X axis of the oleodynamic azimuth stern A and the consequent rotation thereof by an angle from 0° to 360°.
Figure 10a shows an overall side view of the oleodynamic azimuth stern provided with the apparatus of the preceding figures, in a position wherein the axis of the shaft is rotated by 90°, i.e. wherein the torpedo is positioned transversally to the longitudinal axis of the vessel.
Should it be required to have the propellers provide a propulsion in the driving direction, the activation of the oleodynamic means 30 supplied by the oleodynamic fluid passing through the connection means 200, determines a rotation around the vertical X axis of the oleodynamic azimuth stern A by 180° (figure 10b).
All means 200, 500, 100, 600, 300 are configured so as to allow supply of pressurized oil from the engine unit of the vessel up to the oleodynamic motor of the torpedo S of the oleodynamic azimuth stern A.
The apparatus is characterized in that any variations of the arrangements of the kinematic mechanism 1, through an oleodynamic activation of the means 17, 18, and any variations of rotation of the azimuth stern A around its own vertical X axis, through the oleodynamic activation of the means 30, can be performed either in separate steps or simultaneously. The apparatus allows the oleodynamic activation of the means 17, 18 and of the means 30 can be performed while the propeller E is rotating.
The apparatus makes it possible to vary the operating positions of the oleodynamic azimuth stern A as an outboard motor or as a surface propeller, in both driving and reverse directions.
By using the apparatus according to the present invention, it is possible to provide for a simultaneous (as well as individual) raising, lowering, trimming, and rotation of the azimuth stern of a vessel.
It is also possible to move the azimuth stern without being obliged to stop the propeller, to position the propeller of the azimuth stern in such a position as to provide not only a driving propulsion but also a reverse one, and to use the oleodynamic azimuth stern as an outboard motor or as a surface propeller.
The apparatus according to the invention also makes it possible to transmit the torque of the engine unit onboard the vessel to the transmission members of the azimuth stern, without losing production efficiency, by way of the pipes used to supply the pressurized oleodynamic liquid which are integral parts in the oleodynamic kinematic mechanism. The specifically designed connection plate provided with quick release mechanical and hydraulic attachments makes it possible an easy and quick connection of the apparatus to the transom of the vessel.
Another outstanding features of the apparatus is in that, being the azimuth stern connected to oleodynamic cylinders and being these provided with shut-off and pressure relief valves, in the case of a collision with dead bodies, the stern raises up and softens the collision, because the pressure relief valves in the cylinders discharge the excess pressure, thus resulting in raising it up.
The apparatus for varying the operating positions of an oleodynamic azimuth stern of a motorized vessel according to the present description is susceptible of numerous modifications and variants, all falling within the inventive concept set forth in the attached claims.
All details can be replaced by other technically equivalent elements, depending on the actual requirements, without leaving the scope of protection of the present invention.
Even though the apparatus has been described with a special reference to the attached figures, the reference numbers used in this description and in the claims are used for making the invention more understandable and shall not be construed to limit the claimed scope of protection in any manners.

Claims

Apparatus for the variation of the operating positions of an oleodynamic azimuth stern (A), provided with a torpedo (S) and a propeller (E), mounted on a motorized vessel (N), and comprising a removable attachment plate connected to the transom (P) of the vessel, an oleodynamic rotary joint jointly connected to an attachment plate and an oleodynamic kinematic mechanism interposed between both said attachment plates and removably connected to them characterized by the fact that said kinematic (1) is provided with:
- oleodynamic means (100), comprising at least a pair of hollow tubular components (11), arranged parallel to each other, for passage of pressurized liquid coming from the engine unit of the vessel (N), whose ends (111) and (112) are jointly connected to cylindrical hollow components (14) (15) respectively, provided with cylindrical seats (141) (151) coaxially rotationally connected to rotate around an oleodynamic cylindrical pin (5) and around an oleodynamic cylindrical pin (6) respectively, which are coaxially rotationally connected to rotate within circular seats (21) (41) on the attachment plate (2), removably connected to the transom (P) of the vessel and on the attachment plate (4) of the oleodynamic rotary joint (3) respectively,

- a first pair of tubular components (12) whose ends (121) (122) are jointly connected to the hollow cylindrical component (14) and to a mechanical cylindrical joint (16), provided with a cylindrical seat (161) for housing of a cylindrical pin (162), respectively,

- a second pair of tubular components (13) whose ends (131) (132) are jointly connected to the hollow cylindrical component (15) and to the mechanical cylindrical joint (16) respectively,

- a first pair of oleodynamic means (17) each one provided with
i. a cylinder (171) having a circular seat (171.1) rotationally connected to rotate around a pin (222) coaxially inserted in circular seats (221) of the mechanical joint (22) of the plate (2) at one end and

ii. a piston (172) having a circular seat (172.1) rotationally connected to rotate around a cylindrical pin (162) of the mechanical cylindrical joint (16) at one end,

- a second pair of oleodynamic means (18) each one provided with
i. a cylinder (181) having a circular seat (181.1) rotationally connected to rotate around a pin (422) coaxially inserted in circular seats (421) of the mechanical joint (42) of the plate (4) at one end and

ii. a piston (182) having a circular seat (182.1) rotationally connected to rotate around a cylindrical pin (162) of the mechanical cylindrical joint (16) at one end,

- oleodynamic means (30) for driving a gear mechanism (31) jointly connected to the rotary joint (3),

- oleodynamic connection means (200) connected to the attachment plate (2), removably connected to the transom (P) of the vessel (N), for the direct supply of the high pressurized oleodynamic fluid coming from the engine unit of the vessel to the oleodynamic kinematic mechanism (1) and to oleodynamic means (30),
in that said components (14, 141, 5, 21) (15, 151, 6, 41) form two oleodynamic cylindrical joints (500), (600) respectively, each of them having a rotation axis (Y, Z) respectively, the activation of at least one of said rotations being triggered by oleodynamic fluid passing through connecting means (200), through at least one of the oleodynamic cylindrical joints (500), (600), and at least one pair of oleodynamic means (17, 18),
and in that the circular seats (172.1, 182.1) of the pistons (172, 182) of said means (17, 18) respectively are rotationally connected to rotate coaxially with the pin (162) of the mechanical joint (16), and the circular seats (171.1, 181.1) of the cylinders (171, 181) of said means (17, 18) respectively are rotationally connected to rotate coaxially to the pin (222, 422) of the mechanical joint (22, 42) respectively, the pistons (172, 182) of said means (17, 18) respectively being opposed so as to rotate, at different angles, around the pin (162).
Apparatus according to claim 1, characterized in that the activation of oleodynamic means (17), supplied by oleodynamic fluid passing through connection means (200) and oleodynamic means (500), provides a rotation of the oleodynamic kinematic mechanism (1) around axis (Y) of the oleodynamic cylindrical pin (5) and subsequent raising or lowering of the oleodynamic azimuth stern (A).
Apparatus according to claim 1, characterized in that the activation of oleodynamic means (18), supplied by oleodynamic fluid passing through connecting means (200) and oleodynamic means (500, 100, 600), provides a rotation of the oleodynamic kinematic mechanism (1) around axis (Z) of the oleodynamic cylindrical pin (6) and subsequent trimming of the oleodynamic azimuth stern (A).
Apparatus as claimed in claim 1, characterized in that fluid passing through oleodynamic means (30), directly connected with connection means (200), triggers the activation of a gear mechanism (31), jointly connected to rotary joint (3), and the rotation around vertical axis (X) of the oleodynamic azimuth stern (A) from 0° to 360°.
Apparatus according to claim 4, characterized in that the activation of oleodynamic means (30), supplied by oleodynamic fluid passing through connection means (200), triggers a 180° rotation around vertical axis (X) of the oleodynamic azimuth stern (A) configured to provide propulsion of the propellers in driving direction.
Apparatus according to any one of the preceding claims, characterized in that variations of arrangements of kinematic mechanism (1), by activation oleodynamic means (17, 18), and the variation of rotation angle of azimuthal propulsion (A) around its vertical axis (X), by activation of oleodynamic means (30), are carried out simultaneously.
Apparatus according to claim 6 characterized in that said oleodynamic activation of means (17, 18) and of means (30) are carried out simultaneously during rotation of propeller (E).
Apparatus according to any one of the preceding claims, characterized in that the plate (2), for removable attachment of the oleodynamic kinematic mechanism (1) to the transom (P) of hull of vessel (N), is provided with quick-release mechanical and oleodynamic connections means (200).
Apparatus according to any one of the preceding claims, characterized in that the oleodynamic engine of torpedo (S) of oleodynamic azimuth stern (A) is supplied by pressurized oil coming from the engine unit of vessel (N) and passing through means (300) of rotary joint (3) directly connected with connecting means (200) of plate (2).
Use of the apparatus for the variation of the operating positions of an oleodynamic azimuth stern (A) according to any one of the preceding claims either as an outboard engine or as a surface propeller.
Use of the apparatus for the variation of the operating positions of the oleodynamic azimuth stern (A) according to any one of the preceding claims for the reverse / driving direction propulsion of a vessel.