The present invention relates to a combined rudder and pro¬ peller arrangement for propelling, steering and maneuvering conventional ships and other kind of water craft, herein¬ after referred to simply as vessel-

Combined rudder and propeller arrangements, so-called acti¬ ve rudders, are known to the art, in which the rotatable rudder blade carries a bearing housing for a horizontal propeller shaft on which a propeller is mounted, normally behind the rear or trailing edge of the rudder blade, so that the water flow generated by the propeller will pass on both sides of the rudder blade and so that the propeller will accompany the rotational movements of the rudder blade carried out when steering and maneuvering the vessel. The propeller is normally driven by an electric motor arranged in the bearing housing of the propeller shaft. In the case of active rudders of this kind, the primary purpose of the propeller is to generate a flow of water which will pass the propeller and therewith augment or heighten the rudder effect, particularly at low speeds.

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 propel¬ ler is normally located forwardly of the leading edge of the rudder and is driven either by an electric motor arran¬ ged within the bearing housing or via a bevel gear arrange¬ ment which is located in the bearing housing and connects the propeller shaft with a vertical drive shaft which ex¬ tends upwards, through a tubular shaft intended for rota¬ tion of the rudder-propeller combination and being connec¬ ted 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 steer¬ ing 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 propel¬ ler. 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 pro- -peller efficiency in forward propulsion of the vessel can be greatly improved in this way.

The aforesaid known combined rudder and propeller arrange¬ ment,in which the propeller is firmly connected to the rud¬ der 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 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 propelle 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 posi¬ tion 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 oro- pellers arranged one behind the other and driven in mutual¬ ly opposite directions of rotation.

Consequently, an object of the present invention is to pro¬ vide 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 arrange¬ ment 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 fol¬ lowing Claim 1. Advantages, embodiments and further deve¬ lopments 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 car¬ ried 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 propel¬ ler 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 propel¬ ler unit 2 is rotatably journalled and carried in the tubu¬ lar rudder stock 4. In the case of the illustrated embodi¬ ment 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 con¬ nected, 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 gears 13 are driven by associa¬ ted _, 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 oper¬ able pistons 15 having pins which project from both sides of the pistons and capable of being moved between two dif¬ ferent positions.

The inventive arrangement will thus enable the propeller unit 2 to be locked in a fixed position during normal pro¬ pulsion 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 tτ«.o positions, in which the propeller unit strut 8 is released from the hull and the strut is instead connected to the rudder stoc 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 lock¬ ing the propeller unit 2 to therudder 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 rud¬ der 1 can be configured in a number of different ways, e.g. in correspondence with the rudder area required by the app¬ lication 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 configura¬ tion, as in the case of the Figure 1 embodiment, or a semi- cylindrical 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 hemis¬ pherical or semi-cylindrical end of the housing 9. The rud¬ der part which lies behind the housing 9 may also be con¬ figured 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 dis¬ ruption 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 pro¬ file 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 effi¬ ciency.

From a purely general aspect, the rudder part of an inven¬ tive combined rudder and propeller arrangement may be con¬ figured 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 pro¬ peller 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 conceiv¬ able 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 pinion 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 th. s 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 mutu¬ ally different rotational positions quite independently of one another. Naturally, this will afford all of the afore- described 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 situa¬ tion and for each particular operating condition.

Figure 5 illustrates schematically and in a manner similar to Figure ^' 1 a further embodiment of an arrangement accord¬ ing 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 positio¬ ned in any desired direction whatsoever. In this case the rudder 1 is rotatably journalled on and carried by the pro¬ peller 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 steer¬ ing machinery, e.g. in the form of servo motors, for rota¬ tion 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.