EP0394320B1

EP0394320B1 - A combined rudder and propeller arrangement

Info

Publication number: EP0394320B1
Application number: EP89900669A
Authority: EP
Inventors: Orvar Björheden; Dan Johansson
Original assignee: Kamewa AB
Current assignee: Kamewa AB
Priority date: 1987-12-09
Filing date: 1988-12-08
Publication date: 1993-10-20
Anticipated expiration: 2008-12-08
Also published as: FI96757C; KR920700142A; SE8704912D0; FI96757B; DK140990A; DK140990D0; EP0394320A1; FI902810A0; SE459249B; DE3885105D1; KR970010830B1; JPH03501714A; AU2821789A; WO1989005262A1; DK162037B; JP2657422B2; DK162037C; DE3885105T2

Abstract

A combined rudder and propeller arrangement for propelling, steering and maneuvring ships and other water craft. The arrangement includes a rudder (1) which is rotatable relative to the ship about a vertical rotational axis. Built together with the rudder (1) is a propeller unit (2) which includes a propeller (6) which is mounted on a horizontal propeller shaft journalled for rotation in a propeller unit housing (9). The unit is also journalled for rotation relative to the ship about a vertical axis. The rotational axes of the rudder (1) and propeller unit (6) coincide, such as to enable the rudder and unit to be rotated relative to one another. The rudder (1) may be connected to a steering machine (11, 13, 14) for rotation of the rudder whereas the propeller unit (2) is selectively lockable to either the ship in a fixed position, or to the rudder for co-rotation therewith.

Description

The present invention relates to a combined rudder and propeller arrangement for propelling, steering and maneuvering conventional ships and other kind of water craft, hereinafter referred to simply as vessel.
DE-C-326 792 discloses a combined rudder and propeller arrangement which comprises a rudder unit having a rudder part, which is journalled for rotation relative to the vessel about a substantially vertical rudder axis, and a propeller unit with a propeller mounted on a substantially horizontal shaft. The propeller unit is mounted on the rudder part and rotatable relative to it about a substantially vertical axis, which in a modification of the arrangement may coincide with the rudder axis. The rudder part and the propeller unit are associated with separate manual control mechanisms.
This arrangement is disadvantageous in that a change of the angular position of the rudder part relative to the vessel will also cause the angular position of the propeller unit relative to the vessel to be changed, unless the control mechanism associated with the propeller unit is also operated. If it is desired to change the relative position of the rudder part relative to the vessel without changing the relative position of the propeller unit relative to the vessel, it is therefore necessary also to operate the control mechanism associated with the propeller unit such that the change caused by the change of the angular position of the rudder part is offset.
Also known to the art are so-called rudder propellers or rudder thrusters in which a propeller is journalled in a bearing housing connected firmly to the rudder. The propeller is normally located forwardly of the leading edge of the rudder and is driven either by an electric motor arranged within the bearing housing or via a bevel gear arrangement which is located in the bearing housing and connects the propeller shaft with a vertical drive shaft which extends upwards, through a tubular shaft intended for rotation of the rudder-propeller combination and being connected to a driving machine in the vessel. In the case of this latter kind of combined rudder and propeller assembly, the propeller has a propelling function in addition to a steering function.
Combined rudder and propeller arrangements of this latter kind afford many advantages and could be used particularly advantageously with a main propulsion or fore propeller, the combined rudder and propeller being preferably placed straight aft of and coaxially in line with the main propeller. In this case, the main propeller and the propeller of the rudder/propeller combination are rotated in mutually opposite directions. It has been found that the total propeller efficiency in forward propulsion of the vessel can be greatly improved in this way.
The aforesaid known combined rudder and propeller arrangement in which the propeller is firmly connected to the rudder and accompanies rotational movement of the rudder when steering and maneuvering the vessel is encumbered with a number of serious drawbacks, however. For example, when the rudder is turned, and therewith also the propeller which is firmly connected thereto, the propeller blade(s) will be subjected to greater dynamic forces and higher torque, because the axis of the propeller no longer lies parallel with the direction of movement of the vessel through the water. These dynamic forces and torque on the propeller blades are very large at high vessel speeds and large rudder angles and, with respect to the risk of fatigue, require the propeller blades, their attachments, and the propeller hub to be heavily reinforced. It should be observed in this respect that the dynamic forces and torque on the propeller blades vary approximately sinusoidally as the propeller rotates. The requisite reinforcement of the propeller blades, their attachments, and the propeller hub increases propeller costs, while the subsequent increase in the diameter of the propeller hub impairs the efficiency of the propeller. When such a known combined rudder and propeller arrangement is used together with a forwardly located main propeller, an additional drawback is that when the rudder is turned the propeller affixed thereto will be moved away from a position in which it lies straight behind and coaxial with the main propeller, which will impair, even at moderate rudder angles, the desired improved total efficiency of two propellers arranged one behind the other and driven in mutually opposite directions of rotation.
Consequently, an object of the present invention is to provide an improved combined rudder-propeller assembly which is not encumbered with the aforesaid drawbacks and which will, in general, afford the same advantages as those afforded by a rudder-propeller or rudder-thruster arrangement and which can be used to particular advantage with a main propeller which is driven in an opposite direction of rotation, but which can also be used alone for propelling, steering and maneuvering a conventional ship or some other kind of water craft.
The main characteristic features of the inventive combined rudder and propeller arrangement are set forth in the following Claim 1. Advantages, embodiments and further developments of the combined rudder and propeller arrangement have the characteristic features set forth in the depending claims.
The invention will now be described in more detail with reference to the accompanying drawings, which illustrate a number of exemplifying embodiments of the invention and in which

Figure 1 is a schematic side view, partly in axial section, of a first exemplifying embodiment of an inventive combined propeller and rudder arrangement;
Figure 2 illustrates in a similar manner a variant of the embodiment according to Figure 1;
Figure 3 illustrates in a similar manner another variant of the embodiment according to Figure 1;
Figure 4 illustrates schematically and in a manner similar to Figure 1 a second embodiment of an inventive rudder and propeller combination; and
Figure 5 illustrates schematically and in a manner similar to Figure 1 a third embodiment of an inventive rudder and propeller combination.

The exemplifying embodiment of the inventive rudder and propeller arrangement illustrated schematically in Figure 1 includes a rudder, generally referenced 1, and a propeller unit, generally referenced 2, which are located beneath the bottom surface 3 of the hull of a ship or some other water craft, e.g. in the stern of a conventional ship or sea-going vessel, said hull, etc., being shown only in part and then very schematically. The rudder 1 has a tubular rudder stock 4 which extends up through an opening in the bottom 3 of the hull and which is rotatably journalled in and carried by a bearing seat 5 encircling the opening. Similar to the manner of a so-called rotatable thruster, the propeller unit 2 includes a propeller 6 which is mounted on one end of a horizontal propeller shaft journalled in a housing 9. In the case of this embodiment, the housing 9 is assumed to include a bevel gear arrangement which connects the propeller shaft to a vertical drive shaft 7. The drive shaft 7 extends from the bevel gearing in the housing 9, up through a tubular strut 8, which at its lower end supports the housing 9. The vertical drive shaft 7, which drives the propeller 6, is connected in some suitable and conventional manner (not shown) to a propeller drive machine (not shown) located in the vessel. The carrying strut 8 of the propeller unit 2 is rotatably journalled and carried in the tubular rudder stock 4. In the case of the illustrated embodiment the propeller unit housing 9 is also provided with a downwardly directed pivot shaft 10 which is journalled for rotation in the part of the rudder 1 located beneath the housing 9. This serves to reinforce both the rudder 1 and the propeller unit 2 against occurrent forces and is not necessary in all cases.
The upper end of the tubular rudder stock 4 is firmly connected, within the hull of the vessel, to a gear ring 11 which is journalled for rotation in a stationary or fixed part 12 of the hull and which is in driving engagement with pinion gears 13. The pinion gear 13 are driven by associated steering motors 14 operative in rotating the gear ring 11, and therewith the rudder stock 4 and the rudder 1, in the same way as conventional steering machinery.
The inventive arrangement also includes devices by means of which the strut 8, and therewith the whole of the propeller unit 2, can be locked selectively either to the hull 12 of the vessel, in at least one given fixed position, or to the rudder stock 4 for rotation together therewith. In the case of the illustrated embodiment, these devices comprise one or more hydraulically, pneumatically or electrically operable pistons 15 having pins which project from both sides of the pistons and capable of being moved between two different positions.
The inventive arrangement will thus enable the propeller unit 2 to be locked in a fixed position during normal propulsion of the vessel, by appropriate positioning of the pistons 15 with the propeller shaft extending parallel with the forward direction of the vessel and constantly located straight behind and coaxial with the fore propeller, when such a propeller is found, whereas the rudder 1 can be rotated by means of the steering machinery or gear 11, 13, 14 within a normal rudder turning range, e.g. a range of 30-40°, for holding and steering a normal course. This will eliminate all of the aforesaid drawbacks associated with known combined rudder and propeller arrangements. On the other hand, when maneuvering the vessel at low speeds, the pistons 15 can be placed in the other of their two positions, in which the propeller unit strut 8 is released from the hull and the strut is instead connected to the rudder stock 4. In this latter case, the rudder 1 and the propeller unit 2 can be rotated together by the steering machinery 11, 13, 14, to any desired angular position for instance through 360° if wished. This provides for a high degree of maneuverability, since the propeller thrust can be brought to bear in any desired direction. When locking the propeller unit 2 to the rudder 1 in this way, the propeller shaft will, of course; preferably extend parallel with the plane of the rudder.
Figures 2 and 3 illustrate variants of the aforedescribed inventive embodiment illustrated in Figure 1, primarily to show that in the case of the inventive arrangement the rudder 1 can be configured in a number of different ways, e.g. in correspondence with the rudder area required by the application in question.
When part of the rudder 1 is located behind the opposite end of the housing 9 relative to the propeller 6, as in the case of the Figurres 1 and 3 embodiments, this end of the housing 9 will preferably have a hemispherical configuration, as in the case of the Figure 1 embodiment, or a semicylindrical configuration, as in the Figure 3 embodiment. In addition, that part of the rudder 1 which is located behind this housing part will have a front or forwardly located edge which faces the housing 9 and which conforms with the hemispherical or semi-cylindrical shape of the housing, the centre of rotation of the rudder coinciding substantially with the centre of curvature of the hemispherical or semi-cylindrical end of the housing 9. The rudder part which lies behind the housing 9 may also be configured with or provided with a thickening or so-called bulb which has a streamlined shape conforming to that of the housing 9. This design affords the least possible disruption in the flow of water past the housing 9 and the rudder 1.
In the case of those embodiments where the rudder 1 is located both above and below the propeller unit 2, the profile of the rudder part located above the propeller unit 2 and the profile of the rudder part beneath the propeller unit 2 may have an asymmetric configuration, with an inlet angle and a profile arch such as to reduce rotational flow in the propeller jet. This will improve the propeller efficiency.
From a purely general aspect, the rudder part of an inventive combined rudder and propeller arrangement may be configured in many different ways, all known per se. For instance, the rudder blade may be fitted with a pivotable flap on its trailing edge, for improving the rudder effect. Alternatively, the rudder part may be configured as a so-called "rotating cylinder rudder", in which case the rudder blade carries a rotating cylinder on its leading or front edge. Another alternative is one in which the rudder blade is fitted with end plates on its upper and/or lower edge in a known manner.
Naturally, the propeller of an inventive propeller/rudder combination may either have fixed blade or adjustable blades. In this latter case, the range within which the propeller pitch angle can be varied can be made so great as to enable the propeller blades to be positioned substantially parallel with the propeller axis, i.e. feathered. This facility is particularly advantageous under such conceivable conditions as those in which the ship or like water craft is propelled without using the propeller 6, for instance with the aid of a fore propeller. According to one conceivable embodiment, the propeller unit of an inventive arrangement may include two propellers, suitable counter-rotating propellers, instead of the single propeller of the illustrated and described embodiments.
Instead of being driven by driving machinery located within the hull of the vessel, via a vertical drive shaft and a bevelled gear arrangement in the housing 9, the propeller 6 may be driven by means of a drive motor arranged within the housing 9 and connected to the propeller shaft, this drive motor suitably being an electric or a hydraulic motor.
Figure 4 illustrates schematically and in a manner similar to Figure 1 another embodiment of a combined rudder and propeller arrangement according to the invention. This embodiment differs from the embodiments of Figures 1-3, in that the strut 8 of the propeller is also connected at its upper end with a gear ring 16 which engages drivingly a number of pin ion gears 18 driven by a commensurate number of steering motors 17 connected to said pinions. In this embodiment the rudder stock 4 and the propeller unit strut 8 are thus each connected to respective steering machinery 11, 13, 14 and 16, 17, 18 within the vessel, such as to enable the rudder 1 and the propeller unit 2 to be rotated in mutually different directions and to be located in mutually different rotational positions quite independently of one another. Naturally, this will afford all of the aforedescribed advantages afforded by the Figure 1 embodiment, while at the same time affording the additional advantage of enabling the rudder 1 and the propeller unit 2 to be brought freely to exactly those mutual positions which are considered to be most suitable for each particular situation and for each particular operating condition.
Figure 5 illustrates schematically and in a manner similar to Figure 1 a further embodiment of an arrangement according to the invention. In this embodiment the propeller unit supporting strut 8 is journalled immediately in and carried by the seating 5 in the hull of the vessel, and the top end of the strut is connected to the steering machinery 11, 13, 14 in a manner to allow the propeller unit 2 to be positioned in any desired direction whatsoever. In this case the rudder 1 is rotatably journalled on and carried by the propeller unit support strut 8.
Arranged within the propeller unit housing 9 is steering machinery (not shown in detail) by means of which the rudder 1 is turned relative to the propeller unit 2 in order to hold the vessel on course and to steer the vessel under normal forward vessel speeds, where the propeller unit 2 is held by the steering machinery 11, 13, 14 in a fixed position relative to the vessel, with the propeller shaft lying parallel with the forward direction of the vessel. This rudder steering machinery may comprise, for instance, servo motors which are connected to the rudder 11, e.g., by a crank 19 and a coupling block which runs in a groove or track 20 provided in the rudder 1. Such steering machinery, e.g. in the form of servo motors, for rotation of the rudder 1 relative to the propeller unit strut 8 can even be placed on the upper end of the strut 8 within the hull of the vessel and connected to the rotatable rudder 1 by means of a connecting rod which extends axially through the tubular strut 8 and which carries a crank, similar to the crank 19, at its lower end.
It will be evident from the aforegoing that the inventive combined rudder and propeller arrangement may have many different forms, and that variants and modifications other than those illustrated and described are possible. For instance, the inventive arrangement need not necessarily be mounted beneath a bottom part of the hull of a vessel, but may instead be mounted behind the stern of the vessel, carried by and journalled in a bearing housing firmly fitted to the transom of the hull.
It will also be understood that there are many methods in which the propeller unit can be locked alternatively and selectively to either the vessel hull or the rotatable rudder part and that the described and illustrated ways of locking the propeller unit are merely examples of such methods.

Claims

A combined rudder and propeller arrangement for propelling, steering and maneuvering a water craft, said arrangement comprising a rudder unit which has a rudder part (1) that is journalled for rotation relative to the water craft about a substantially vertical rudder axis, and which has built together therewith a propeller unit (2) which includes a propeller (6) mounted on a substantially horizontal propeller shaft journalled for rotation in a housing (9) and which is rotatable relative to the water craft about an axis which substantially coincides with the rudder axis, characterized by means (15) for selective locking of the propeller unit (2) against rotation alternatively to the water craft to maintain the propeller unit in a fixed angular position relative to the watercraft independently of the rotation of the rotatable rudder part (1), and to the rotatable rudder part (1) to co-rotate therewith.
An arrangement according to Claim 1, characterized in that the rotatable rudder part (1) includes a tubular rudder stock (4) which extends upwards in the water craft and is journalled for rotation and supported therein; and in that the propeller unit (2) includes a strut (8) which is firmly mounted at its bottom end in the propeller unit housing (9) and which extends up through the tubular rudder stock (4) of the rotatable rudder part (1) and is journalled for rotation about the rudder axis in said rudder stock.
An arrangement according to Claim 2, characterized in that the rudder stock (4) and the strut (8) are each connected to its individual steering machine (11, 13, 14 and 16, 17, 18) for individual rotation of the rudder part (1) and propeller unit (2) respectively in relation to the water craft.
An arrangement according to claim 1, characterized in that the propeller unit (2) includes a substantially vertical strut (8) the bottom end of which is firmly mounted in and carries the propeller unit housing (9) and which extends upwardly in and is journalled for rotation in and supported in the water craft (3); in that the rotatable rudder part (1) is journalled for rotation on and carried by said strut (8); in that the strut (8) is connected to a steering machine (11, 13, 14) for rotation of the propeller unit (2) relative to the water craft; and in that the propeller unit (2) includes means (19, 20, 21) connected to the rotatable rudder part (1) for rotation of the rudder part relative to the propeller unit strut.
An arrangement according to any one of Claims 1 - 4, characterized in that the propeller unit housing (9) is arranged in a recess in the rudder (1), the rudder extending both above and behind the opposite end of the propeller unit housing (9) in relation to the propeller (6), and optionally also below said end.
An arrangement according to Claim 5, characterized in that the opposite end of the propeller unit housing (9) relative to the propeller (6) has a part-spherical or part-cylindrical configuration; and in that the rudder part located behind this end of the housing has a leading or front edge which is contiguous with said housing end and a rotational axis which coincides substantially with the centre of curvature of said part-sphere or part-cylinder.
An arrangement according to Claim 6, characterized in that the rudder part located behind the propeller unit housing (9) has a thickening which conforms with the streamline configuration of the housing.
An arrangement according to any of Claims 1 - 7, characterized in that the rudder part located above the propeller unit housing and the rudder part located beneath said housing have an asymmetric shape with an inlet angle and profile arch such as to counteract rotational flow in the propeller jet.
An arrangement according to any one of Claims 1 - 8, characterized in that the propeller unit includes two mutually spaced and mutually coaxial propellers which rotate in mutually opposite directions.