EP0518229A1

EP0518229A1 - Rudder for watercraft

Info

Publication number: EP0518229A1
Application number: EP92109529A
Authority: EP
Inventors: Giorgio Brighi; Franco Harrauer
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-14
Filing date: 1992-06-05
Publication date: 1992-12-16
Also published as: ITGE910084A1; IT1249231B; ITGE910084A0

Abstract

A rudder for watercraft which comprises two rudder blades (3) with opposite hydrofoil configurations (103) which are arranged at the aft region (4) of the hull, spaced apart transversely thereto and symmetrically with respect to the centerline of the watercraft and which are movable in both senses in the vertical direction, alternately from a contemporaneous raised unoperative position to an immersed operative position, wherein the respectively immersed blade (3) causes the turn or shift of course of the watercraft to the corresponding direction, and vice versa.

Description

The invention relates to a rudder for watercraft.
Generally, watercraft with symmetrical propelling thrusts, and more particularly speed-craft with a deep V shaped hull, theoretically maintain a rectilinear and steady course until affected by external or internal disturbing actions such as, for example, a lateral wind or displacements of load over a transverse plane. Presently, rudders consist of one or more vertical blades which are immersed constantly in their operative position and are supported below the hull so as to be rotatable about a vertical axis. Under way, the action of rudders is limited to very short time periods, i.e. only during either turns or course adjustments. In contrast, however, conventional rudders permanently contribute substantially (about 6% to 10%) to the total hydrodynamic drag of hulls. Moreover, hydrodynamic drag, known also as protrusions drag, increases with the squared speed during the movement. With the use of surface screw propellers, rudders constitute presently also the terminal hydrodynamic drag affecting a hull.
Therefore, the object of the invention is to provide a rudder for watercraft, which is adapted to overcome effectively and with a comparatively small constructional disbursement the disadvantages of known rudders.
Moreover, the invention aims to provide watercraft rudders which can be easily and quickly mounted either on newly-built or on existing watercraft.
The invention achieves these objects by providing a watercraft rudder comprising two rudder blades having opposite hydrofoil configurations and arranged in the aft region of the hull, apaced apart transversely thereto and symmetrically with respect to the centerline of the craft, and movable in both senses in the vertical direction, alternately from a contemporary raised unoperative position to an immersed operative position, wherein the respectively immersed blade causes the turn or shift of course of the watercraft to the corresponding direction, and vice versa, this effect being due to the action of the hydrofoil and to the incidence of the latter, which changes with the twist of the blades.
In the raised unoperative position, the blades are completely raised out of the water, or else they can penetrate the water either partially or completely.
In fact, the blades can be immersed gradually to different levels of their height and their hydrofoil can have a variable action at the different cross sections, for example a helical configuration which tapers towards the free end thereof, whereby the steering effect on the craft varies depending upon the depth of their immersion.
In order to avoid any risk of cavitation or formation of an air space on their suction face, the blades may be provided with anti-cavitation means capable of preventing or anyway minimizing said effects.
The control means for the rudder may be of conventional type, comprising a steering wheel or tiller whose progressive rotation in either directions causes, through a suitable drive of mechanical, pneumatic, hydraulic or the like type and/or of manual or servo-assisted type, the progressive raising and lowering of either the one or the other blade.
During the navigation along a rectilinear course, the rudder blades may be kept in a raised unoperative position, completely out of the water, until a turn or shift of course is desired. For this purpose, the helmsman commands the immersion of only one of the two blades and keeps it in the operative immersed position only during the time period that is required to effect said turn. The hydrodynamic interference between blades and water, therefore, is limited only to the operative periods of the rudder, thus eliminating effectively its dragging contribution to the drag due to the hull. The reduction of drag may be up to 6% to 7% of the total drag of the hull, thus permitting either to obtain an increase of speed or to use propelling engines of correspondingly lower power.
The invention also relates to other characteristics which further improve the invention rudder and which constitute the subject matter of the sub-claims.
The particular characteristics of the invention and the advantages resulting therefrom will appear with further details from the description of some preferred embodiments, shown as non-limiting examples in the accompanying drawings, wherein:

Figures 1 and 2 show a front view and a side view of a first embodiment of the rudder according to the invention;
Figure 3 is a block diagram of a control circuit of a second embodiment of the invention;
Figure 4 is a block diagram of a modification of the control circuit of the servo-assisted type;
Figure 5 is a perspective view of a second embodiment of the rudder according to the invention;
Figures 6 and 7 are a side view and a top plan view of a modified embodiment of the rudder according to Figure 5;
Figure 8 is a perspective and partly sectional view of a first modified embodiment of the example according to Figures 5 to 7;
Figure 9 is a longitudinal vertical sectional view of a second modified embodiment of the example of Figures 5 to 7;
Figure 10 is an enlarged embodiment showing the supporting means for the actuating cylinder of the modification according to Figure 9.

With reference to Figures 1 and 2, a first embodiment of the rudder comprises an arm 1 which is bent intermediately into a V configuration and is provided at the free ends thereof with a respective rudder blade 3 directed transversely to the extent of the V-shaped arm 1 and longitudinally to the hull. The V-shaped arm 1 is secured to a rotatable shaft 2 at the apex of the V. The rotatable shaft 2 is journaled in the intermediate region of the transom or stern plate 4 of a watercraft having a V-shaped careen. The level of the journal for the shaft 2 in the transom 4, the angle of the V-shaped arm 1, and the angle between the rudder blades 3 and respective section of the arm 1 are so dimensioned whereby, in the unoperative position of the rudder (i.e. with the arm 1 in the horizontal position), both blades do not project beyond the lower surface of the careen 5, whereas in the operative position when the rudder fulfils its maximum shifting action (as shown with dot-and-dash lines in Figure 1), the arm 1 is so inclined whereby the respective immersed blade 3 protrudes entirely beyond the lower surface of the careen 5 and is orientated in a substantially vertical position.
The oscillation of the arm 1 in either directions may be controlled by means of the usual steering wheel or tiller through any drive means, for example, of the mechanical, electrical, hydraulic or pneumatic type, etc. In the illustrated embodiment, on the inner side of the transom 4, the rotatable shaft 2 carries, in a mutually non-rotatable manner, a control lever 6 which is pivoted at 7 to the rod 8 of a double-acting actuating cylinder 9 of the pneumatic or hydraulic type, or the like. The cylinder 9 may be controlled by means of a simple hydraulic circuit which is closed by an additional actuating cylinder (not shown) which is connected to the steering wheel or tiller.
Each blade 3 comprises, on its outer side 103, a variable-action hydrofoil. In the illustrated example, the hydrofoil is of helical configuration and is tapered transversely to the blades 3 transversely thereof. The extrados or suction side 203 is substantially planar and the blade 3 merges with the V-shaped arm 1 through the intermediary of a perpendicular plate 303 which is orientated longitudinally of the hull and which, in the fully immersed position of the rudder, is substantially horizontal. On their aft side, the blades 3 are tapered towards their free end with a rounded or helical profile also longitudinally of the hull.
During the navigation along a rectilinear course, the rudder is kept in the raised unoperative position according to Figure 1. In this instance, the blades 3 do not interfere with the water flowing under the careen 5, thus avoiding contributing to the hydrodynamic drag. By operating the steering wheel or tiller, the helmsman causes a corresponding oscillation of the arm 1 in the same direction and, therefore, the immersion of a given length of the respective blade 3 into the water flowing under the careen 5. Since the shifting effect of the blade 3 is determined by the action of the helical configuration thereof which has been immersed, said shifting effect can be proportioned continuously depending upon the extent a blade 3 has been immersed into the water flowing under the careen 5. Increasing steering angles, therefore, will cause increasing immersion extents of the respective blade 3 into the water flowing under the careen 5 and, as a result, a stronger shifting action, i.e. a narrower and more abrupt turn.
In the exemplary embodiment of Figure 3, each blade 3 is actuated independently by an associated hydraulic double-acting cylinder 10. The blades 3 are shown diagrammatically, but the raising and lowering movements of the blades may be carried out as shown in the example of Figures 5 to 7.
The double-acting cylinders 10 are connected to each other and to an actuating pump so as to constitute a closed hydraulic circuit. The steering wheel (not shown) controls a reversible manual pump 12 which is connected separately via the control ducts 13,13' to the upper chamber 110 of each of the two actuating cylinders 10. The lower chambers 210 of the two cylinders 10 are connected to each other via a duct 14. A liquid tank 15 maintains the fluid head and is connected separately to the control ducts 13,13' via the ducts 16,16' having inserted therein the filling valves 17,17'. In order to prevent the control system from reversing, thus locking the blades 3 against the action of external forces acting thereon, a conventional double stop valve 18 is inserted in the control circuits. In the raised unoperative position of the rudder, both pistons 19 in the cylinders 10 are in such an intermediate position whereby the free ends of the associated blades 3 skim the surface of the water. By actuating the manual pump 12 in either direction by means of the steering wheel, the flow of pressurized liquid causes the piston 19 of one of the actuating cylinders 10 to move downwards, and the piston 19 of the other actuating cylinders 10 to move simultaneously upwards, whereby one of the respectively associated blades 3 will be immersed and the other will be raised according to the selected steering angle. Advantageously, in addition to the manual pump 12 or as an alternative thereto, a powered pumping unit 30 may be provided.
The example of Figure 3 is referred to small-sized watercraft wherein manual steering by means of the pump 12 is convenient. In case of larger-sized watercraft, wherein a servo-controlled system is more suitable, a control system according to the example of Figure 4 may be used. The pumping unit 30 is connected to the remaining part of the circuit by means of a hydro-guide 32 of conventional type, for example of the type which is used also on motor-vehicles. The two pipes 36,36' connecting the hydro-guide 32 to the slave cylinder to move it in either direction, in accordance with the actuation of the steering wheel 33, are connected contemporarily to both cylinders 10. More particularly, the right-hand pipe 36' is connected both to the lower chamber 210 of the left-hand cylinder and to the upper chamber 110 of the right-hand cylinder 10 and, vice versa, the pipe 36 is connected to the upper chamber 110 of the left-hand cylinder 10 and to the lower chamber 210 of the right-hand cylinder 10.
Such a circuit causes simultaneously the actuation of a cylinder 10 in one direction and of the other cylinder 10 in the opposite direction, for example, the right-hand cylinder 10 "upwards" and the left-hand cylinder 10 "downwards", and vice versa. However, the essential characteristic of this circuit resides in the fact that the pressurized fluid always enters directly, unobstructed, the lower chamber 210 of the opposite cylinder, whereas the entrance into the upper chamber 110 of the respective hand cylinder is permitted only upon the opening of an interposed sequence-valve 38,38', calibrated at an intermediate value between zero pressure and maximum pressure, generally 10-20 bar.
In fact, bearing in mind that the thrust of the water promotes the retraction of a piston, even with a moderate calibration pressure of the sequence valve 18, 18', the priority of the raising movement of the opposite rudder will be always obtained, before operating the selected rudder. More particularly, the opening pressure of the sequence valve 38,38' will be reached only after reaching the upper limit position, and thereafter the oil may also enter the upper chamber 110 of the opposite cylinder to cause the downward movement of the piston and the immersion of the rudder blade 3 into the water, thus initiating the turn or the shift of course. This circuit has many advantages:

it is faster than the manual system of Figure 3, so that its action is quicker;
the lower chamber 210 of each cylinder has a smaller volume than the upper one due to the presence of the piston rod and, therefore, the time for emergence of the rudder is shorter than the time for immersion, substantially, the lapse of time from the helmsman's decision to steer in the opposite direction to the beginning of the active step of course shift is smaller with respect to the same manoeuver effected with a manual rudder where the speed is always constant;
the speed of the manoeuver may be easily regulated by means of a flowrate regulator (not shown) and, therefore, may closely match the specific operating conditions of a watercraft or the conditions arising from navigational requirements, e.g. the conditions of the sea, or even in connection to the use of an autopilot.

Figures 5 to 7 show a particular embodiment of the rudder according to the invention.
According to the diagrammatic embodiment of Figures 3 or 4, each blade 3 is supported in a mechanically independent manner, and the connection therebetween is implemented through the control circuit. Each blade 3 is secured to the underside of a horizontal supporting plate 21 which is hinged to the lower end of a plate 22 which is fixed to the transom or stern plate 4, so as to be oscillatable about a horizontal axis which is parallel to said transom plate 4. The underside of the supporting plate 21 is planar, while the upper side is provided with a plurality of stiffening ribs 221. The two plates 21 and 22 are connected to each other by a double-acting actuating cylinder 10. The cylinder 10 is pivoted, preferably, at an end of its body portion, to the top end of the attachment plate 22, and at the end of the rod 11 to a connection lug 121 which is suitably arranged on the plate 21, specifically on its intermediate region. The blades 3 will be immersed to their operative position below the lower surface of the careen 5 and will be raised to their unoperative position above said surface thanks to the oscillation of the supporting plates 21. The positioning of the attachment plates 22 on the transom plate 4, the angle of oscillation thereof and of the blades are such as to ensure the operation of the rudder as described with reference to the preceding embodiments, with particular reference to that according to Figure 4.
In the transverse direction, the blades 3 have a helical hydrofoil configuration similarly to the preceding embodiments, while they are suitably curved towards the transom or stern plate, so as to compensate for their angular offset with respect to the horizontal plane which otherwise would occur upon oscillating the supporting plate 21.
Though the rudder according to the invention may be easily arranged both on newly-built watercraft and on existing watercraft, the last-described embodiment is particularly advantageous in that it does not require any direct operation on the hull, and particularly no through-hole below the waterline. All supporting means and actuators are external to the transom or stern plate. Only the control ducts for the actuating cylinders and the other elements of the control circuit are to be arranged within the hull.
With particular reference to Figures 6 and 7, each blade 3 may be associated with means for preventing or limiting the cavitation effects. Said means may consist of a stationary flap which is formed by a horizontal rearwards extension of the attachment plate 22, terminating at a certain distance from the front side of the blade 3.
Figures 6 and 7 show a particular exemplary embodiment wherein the immersion rudder 3 is associated with a trimming flap 23, which is very advantageous in limiting the likelihood of cavitation at said rudder.
An attachment plate 22 is secured to the hull and supports a horizontal planar portion 122, which is suitably ribbed, comprising a hinge 221' for pivotal movement of both the supporting plate 21 for the operative rudder blade 3 through an angle of about 45°-55°, and the ribbed flap 23 through a limited angle of about 12°-15°. Substantially, the blade 3 enters the water by passing through a triangular slot 25 in the flap 23. The up-and-down actuation of the rudder 3 secured to its supporting plate 21 is effected by means of the cylinder 10, while the up-and-down actuation of the flap 23 is effected by means of a pair of parallel cylinders 24.
In the modified embodiments according to Figures 8 to 10, the actuating cylinder 10 for oscillating the blades 3 is embedded within the transom or stern plate 5'.
In the modification according to Figure 8, the stern plate 5' comprises a slot 105' which accommodates a recess-like housing 40 of the attachment plate 22. The actuating cylinder is supported, so as to be pivotable in a vertical longitudinal plane, at its end within the recess-like housing 40, and only its rod 11 protrudes therefrom in a rearwards direction. The attachment plate 22 has also fixed thereon a casing 41 in the shape of a cylinder sector which is co-axial with the pivotal axis 221' of the supporting plate 21 of the blade 3 and which has a radial section complementary to, and slightly larger than, the planform of said supporting plate 21, and which extends angularly substantially from the attachment plate 22 to the completely-lowered supporting plate 21.
By arranging the actuating cylinder 10 inwards of the stern-plate 5', i.e. further afore, the rearwards extension of the rudder can be reduced, in that the pivotal connection of the rod 11 to the supporting plate 21 will be nearer to said stern-plate 5'.
With reference to Figures 9 and 10, the actuating cylinder 10 is supported pivotably at least in said longitudinal vertical plane in the region of the stern-plate 5' thanks to an articulated joint 42 arranged at the outlet end thereof for the rod 11, directed towards said stern-plate. The articulated joint 42 is of the spherical type and is located, preferably, at the free end of an axial tubular extension 43 of said end of the actuating cylinder 10, permitting the outlet of the rod 11 which is guided through the tubular extension 43. The spherical joint 42 is engaged in a complementary spherical seat formed in a supporting bush 44 secured to the stern plate 5' at a through-slot 105'.
As shown in Figure 10, the annular seat comprises two rings 45,46 which are tightened against each other around the joint 42 within the bush 44 thanks to a locking ring 47 which can be threaded in the bush 44. The watertight condition through the bush 44 is ensured by seals 48,49 mounted on the rings 45,46 and interposed between the rings 45 and/or 46 and the surface of the spherical joint 42 and between them and the inner wall of the bush 44, respectively.

Claims

A rudder for watercraft, characterized in that it comprises two rudder blades (3) with opposite hydrofoil configurations (103) which are arranged at the aft region (4) of the hull, spaced apart transversely thereto and symmetrically with respect to the centerline of the watercraft and which are movable in both senses in the vertical direction, alternately from a contemporaneous raised unoperative position to an immersed operative position, wherein the respectively immersed blade (3) causes the turn or shift of course of the watercraft to the corresponding direction, and vice versa.
A rudder according to claim 1, characterized in that in the raised unoperative position, the blades (3) are completely raised out of the water or else they can penetrate the water either partially or entirely.
A rudder according to claim 2, characterized in that in the raised unoperative position, the blades (3) are raised just above the undersurface of the careen (5) of a V-shaped hull, whereas in the operative position they protrude below said surface.
A rudder according to claims 1 to 3, characterized in that the blades (3) may be immersed gradually to different levels of their height, and their hydrofoil (103) can have a variable action at the different cross sections, whereby the steering effect varies depending upon the hydrofoil configuration and upon the incidence of the latter which changes with the twist of the blades (3), or with the depth of immersion of said blades (3).
A rudder according to claim 4, characterized in that each blade (3) has on its outer side a helical profile which tapers transversely to the blade (3) towards the free end.
A rudder according to one or more of the preceding claims, characterized in that each blade (3) tapers in the longitudinal direction of the hull toward its free end, preferably, with a rounded or helical profile on both or on one of its forward and/or rear sides.
A rudder according to one or more of the preceding claims, characterized in that each blade (3) may be provided with anti-cavitation means (23) for either preventing or minimizing the effects of cavitation and formation of air spaces on the extrados or suction side.
A rudder according to one or more of the preceding claims, characterized in that the blades (3) are connected to a steering wheel or tiller (33) by means of a suitable drive of mechanical, hydraulic, pneumatic, oleodynamic type or the like.
A rudder according to one or more of the preceding claims, characterized in that the control drive for the blades (3) may be of either the direct or the servo-assisted type.
A rudder according to one or more of the preceding claims, characterized in that the blades (3) are supported on the outer side of the transom or stern plate (4).
A rudder according to one or more of the preceding claims, characterized in that the vertical displacaments of the blades (3) are interconnected to each other, the displacement of one of the blades in one direction (3) being contemporaneous with an equal displacement of the other blade (3) in the opposite direction.
A rudder according to claim 11, characterized in that the blades (3) are rigidly connected to each other and are disposed, for example, at the ends of an arm (1) which is supported pivotably in a vertical plane which is perpendicular to the vertical, longitudinal central plane of the hull and about a perpendicular axis coinciding with its center of gravity considered in the vertical longitudinal central plane of said hull.
A rudder according to claim 12, characterized in that the arm (1) is bent intermediately into a V configuration and is secured at the apex of the V to a rotatable shaft (2) which is rotatably and sealingly guided on the outer side of the transom or stern plate (4).
A rudder according to claim 13, characterized in that the inner end of the rotatable shaft (2) is engaged operatively with an actuator, e.g. a double-acting cylinder 9, by means of a laver 6.
A rudder according to one or more of the preceding claims 1 to 11, characterized in that each blade (3) is supported independently on the stern-plate (4), the interconnection of the drive thereto being effected at the control system.
A rudder according to claim 15, characterized in that each blade (3) has associated therewith a separate double-acting actuating cylinder (10), the chambers (110) of the actuating cylinders at one side of the piston (19), preferably the upper chambers, being connected separately (13,13') to the control circuit, whereas the chamber (210) of the two actuating cylinders (10) at the other side of the piston (19), preferably the lower chambers, are connected to each other.
A rudder according to claim 16, characterized in that the actuating cylinders (10) are connected to each other and to a manual pump (12) and/or to a motorized power pump (30), said pumps (12,30) being both of the reversible type and actuatable by the steering wheel or tiller, so as to form a closed hydraulic circuit (13,13',14).
A rudder according to claim 15, characterized in that each blade (3) is associated to a double-acting actuating cylinder (10), a powered pump (30) being provided to feed, by means of control ducts (36,36') of a hydro-guide (32) connected to the steering wheel (33), the actuating cylinders (10), each control duct (36,36') being connected respectively to one of the two chambers (110) at one side of the piston (19) of a cylinder (10 for one of the blades (3) by means of a sequence valve (38,38') and directly to the chamber (210) at the opposite side of the piston (19) of the other actuating cylinder (10) for the other blade (3).
A rudder according to one or more of the claims 15 to 18, characterized in that the control circuit comprises means (18) for locking the desired position of the blades (3) against the action of external forces acting thereon, for example, a conventional double lock valve.
A rudder according to one or more of the claims 15 to 19, characterized in that each blade (3) is carried by a respective separate horizontal supporting plate (21) which hinged, so as to be pivotable in the longitudinal direction of the hull, to a corresponding plate (22) for attachment to the stern-plate (4), each supporting plate (21) and respective attachment plate (22) being additionally connected to each other by an actuating cylinder (10) which is pivoted to them at points radially spaced from the hinge axis.
A rudder according to claim 20, characterized in that the blades (3) are curved towards the transom or stern plate (4) substantially correspondingly to the radius of curvature about the pivotal axis of the supporting plate (21).
A rudder according to claim 21, characterized in that each of the attachment plates comprises a longitudinal horizontal extension (122) whose rearward end is pivoted to the supporting plate (21) for the blade (3) and that it extends therebelow with at least one horizontal stationary flap (23) terminating forwards of the front side of the blade (3).
A rudder according to claim 21, characterized in that the attachment plate (22), the blade (3), have associated therewith a flap (23) which is pivotable about an axis parallel to the pivotal axis of the blade (3) and is controlled by means of one or more actuating cylinders (24) which are pivoted at points on the flap (23) and attachment plate (22) that are radially spaced from the pivotal axis.
A rudder according to claim 23, characterized in that the flap (23) extends partially below the supporting plate (21) for the blade (3) and forms in coincidence with the path of travel of said blade (3) a slot (25) for passage thereof.
A rudder according to claims 23 and 24, characterized in that said flaps may be pivoted to an angular position inclined downwards below the supporting plate (21) in its lowermost limit position.
A rudder according to one or more of the preceding claims, characterized in that the actuating cylinder (10) for raising and lowering each supporting plate (21) for the blade (3) is embedded within the transom or stern plate (5') and protrudes rearwards therefrom, preferably, only with the piston rod (11).
A rudder according to claim 26, characterized in that the actuating cylinder (10) is arranged within a housing recess (40) of the stern plate (5') and is pivotably secured at least in one vertical longitudinal plane of the hull at its end within the housing recess (40).
A rudder according to one or more of the preceding claims, characterized in that the stern plate has secured thereto a casing (41) for shielding the supporting plate (21) for the rudder blade (3), said casing (41) being in the shape of a cylindrical sector co-axial with the pivotal axis (221') of the supporting plate (21) to the stern plate (5'), with a radial section corresponding substantially to that of the supporting plate (21) and with an angular extent from the stern plate (5') to the supporting plate (21) in the lowermost position of the blade (3).
A rudder according to claim 26, characterized in that the actuating cylinder (10) is pivotably supported at least in a vertical longitudinal plane of the hull in the region of the stern plate (5') by means of a pivotal joint (42), preferably of the spherical type, provided at the end of said actuating cylinder (10) wherefrom the rod (11) comes out, i.e. the one directed rearwards.