Prior art of steering systems

On the today's motorised craft for steering one or more traditional rudders are used generally consisting of a blade providing with a torsion shaft manoeuvred from inside the hull. Similar system is used for the stabilising devices. This kind of appendages are normally maintained immersed in navigation also when not utilised with the drawback of a power consumption particularly on the fast boats as motor yachts, patrol vessels, catamarans etc, considering also that this power consumption increases not proportionally but with the square of the speed .

An other drawback less evident but not less important that will be better illustrated at the end of the Description and in the fig. 6, 7, 8, 9 consists on the fact that, when sailing in rough sea, the action of the water on the rudder blade, usually orientated up to a maximum value of 35° creates, beside a drag, lifting forces perpendicular to the longitudinal axis of the ship (Fig.7) acting abaft alternatively on port or starboard side obliging the ship to follows a zigzagging course. This situation better named in the marine jargon "yawing" reduces speed and increases a lot the fuel consumptions as any skipper knows well .

The system object of this invention will reduce such situation due to the asymmetric drag force induced by the rudder operating only on the veering side. At the end of the ^x 90 years a steering system have been studied and realized maintaining the rudders retracted on board during the course but capable to be inserted into the water each time when necessary for steering. Naturally the immersed rudder was only that one inside the veering. The system was based on the fact that any watercraft having a completely symmetrical keel and with balanced propulsive forces tends to keep a constant direction of the course if no extraneous forces such as wind, wave motion, current etc. intervene to change the direction of navigation.

Rudders based on these assumptions were activated only when required for a limited percentage times and also with limited incidences during the normal steering on course obtaining a considerable fuel saving.

On this base a steering apparatus have been realized consisting of a pair of retractable rudders installed abaft the boat outside the transom one on right side and one on left side immersed only when necessary to veering.

(See the Aplication PCT E 518 229 Al at name Brighi/ Harrauer)

This known kind steering device yielded favourable results in confirming that a watercraft navigating in course with retractable rudders shows no greater instability that the conventional ones but with the considerable advantage to save fuel especially at high speeds.

Nevertheless this kind of steering system was not generally applied because of marine marked tendency to conservatism and because the installation of the equipment attached and projecting outside of the transom created fear that some collision backing to the quay might damage the steering means.

On the basis of the obtained results a different version was found essentially consisting of two units each contained this time in a watertight housing symmetrically installed inside the hull on portside and on starboard side each provided with a retractable rudder blade essentially connected to a prismatic element of guide vertical sliding inside a tubular housing movable by an actuator contained inside the casing, so that it can be retracted or projected out for variable extent in water as shown in fig. 5. More details of this system are contained in the doc. US 7,434527 B2 oct. 2008 and EP 1718522 both at name Brighi .

This system also did not have diffusion on the market manly for two reasons: the first one because the considerable vertical dimensions especially for applications as anti rolling device requiring inside the hull a certain space for the tubular shape of the housing containing the blade, the prismatic guide and part of the actuator . The second important reason consisting on the difficulty to bring outside to the housing in condition of absolute protection and safety the monitoring systems relative to the blade position necessary for the auto pilot system and automatic stabilisation as well. All these problems are resolved by the system described in our present application .

This is in short the actual prior art stage for the steering system at our knowledge.

Prior art concerning the stabilisation equipments As before said in the abstract the equipment object of the invention has the particularity to be used also as stabilisation device in condition of rough sea but also in certain situations as well at high speed when the boat takes a swinging tendency creating serious worries on board.

The today's antirolling stabilisation equipments consist generally of a pair of fins similar to rudders outstanding on both sides of the boat under the water level these fins rotating on its axis automatically monoevered from inside board capable to create a couple opposed to that couple created by the rough sea .

This kind of fins in smaller craft especially if non planning type are normally permanently maintained outside the board being the power consumption limited, while in important faster and evolved craft a suitable chamber is provided where the entire apparatus can be totally retracted by mechanisms very complicate and expensive because the fin must receive in any case both rotating and translating motions .

Description of the invention

The system object of the invention is constructively the same in case to be used for steering or for stabilisation of the craft during navigation and it includes in any case at least two units each contained in a watertight housing to be installed one on starboard side and the other on the port side and particularly in case of steering gear the units will be placed with vertical axis abaft the ship while in case of stabilisation gear will be placed near the middle ship prevalently with horizontal axis Each unit contains inside a blade (or a fin) provided with a particular a moving device capable to retract or to project the fin outboard partially or totally when necessary for steering or for stabilising passing trough the bottom of the housing where a suitable slot is provided.

Such device consists essentially of a plate 2 joined together with the fin 1 and tilting on a shaft 4 pivoting inside the housing 3 but holding out at least one end 5 passing through a hub 44 provided with a sealing 49 to maintain watertight the housing and at same time to receive the remote control by any kind of electric or hydraulic actuator and at same time to transmit remote information of the fin position.

The system will better illustrated by the enclosed drawings .

Brief description of the drawings Fig. 1 is an exploded perspective representation of the unit to be installed on the portboard side (the starboard side unit is symmetrical) .

Fig.2 shows a vertical section in the middle plane of the same unit.

In this figures we can see that the blade 1 is characterized to have a curvilinear profile in order to permit an easy and complete outlet from the watertight housing 3 obtaining a considerable volume reduction .The incidence angle of the blade will be constant or variable along the blade axis according to the boat features. The blade 1 joined together to the plate 2 is tilting around the axis 4.

The housing 3/33 having prevalently a rectangular section, will be structured in one, two or more parts to permit the assembly of the internal components and to facilitate also the inspections when necessary: the inferior section 3 could be less high than the cover 33 but sufficient to locate two side bearing 31/32 proportioned to support all forces of lifting and drag generated from the water action on the blade.

The same housing 3 will be provided on the base plate with a slot or an aperture 34 having appropriated dimensions to permit the passage of the blade.

The closure flanges 35 of the housing sections 3/33 will be connected by a series of bolts non indicated in the figures after interposal of an adequate tested sealing 49 capable to grant a perfect watertight.

About the quality of the materials a strong material as stainless steel should be suggested for the inferior section 3 of the housing supporting the forces transmitted from the plate appendages 21/22 on the bearing while the section 33 having only cover function fibre glass or aluminium material could be appropriated being light and not expensive.

The inferior section of the housing 3 will be provided with appendages like 36 to be established with the Shipyard in order to connect the housings to the craft . In a standard production the components 1-2- 21 -22-4 can be realised in only one piece

Fig.3 shows in details a section made in a horizontal plane corresponding to the control shaft axis 4 of the plate 2 where we can see the following components : the shaft 4 joined to the plate appendages 21/22 by spines 41/42 or similar connections while in case of standard production the components 1-2- 21 -22-4 can be realised in one piece.

The bearing 31/32 connected to the housing sides

3 will consist preferably of two hubs 43/44 in order to facilitate the assembling and the disassembling each provided with long service bushing 46/47 capable to resist to the sea water and supporting all forces of lifting and of drag transmitted by the blades. In case that the units will be used as stabilising system and, considering the particular heavy duty service, a pair of rolling bearing could be used, properly protected.

The terminal hub 44 of the shaft 4 going outside of the housing 3 will be provided with a sealing 49 widely used and tested to maintain total watertight. On the same hub of the shaft 4 or eventually on the opposite side a mechanical or electrical device transmitting signal of the blade position may be installed, being this signal very important as feed back for the electronic controls .

Fig.4 shows an external view of one steering unit in a compact version where the control shaft 4 sorting out of the housing is operated by the lever 5 from one hydraulic actuator 55 requiring a limited power because the forces to win are manly reduced to the friction forces acting on the bearing 46/47. On the cover 33 of the housing one hydraulic power unit has to be installed totally connected to simplify the installation on board.

Fig.5 shows in the same scale of the unit fig.4 an assembled view of a known steering or stabilising unit described in the doc. characterised by a different movable system of the fin essentially requiring major encumbrance on board specially in highness and over all presenting difficulties to obtain outside of the unit the signal giving constantly the fin position, this particular so important specially for the automatic electronic controls .

The system advantages

In the end the advantages consequential to the use of the described system are:

1- The first more evidence is less fuel consumption or more speed because the rudder blades or fins are retracted when they are not used.

2- Less fuel consumption sailing in rough sea for the yawing reduction as represented in fig.7

3- Better evolution qualities for the effect of the asymmetric drag due to the single rudder exposed only inside the veering, see Fig. 8 and

9

4- The rudder exposed only inside the veering could be provided with an hydrodynamic profile with a better lifting feature than the conventional obliged to have symmetric profile to work with both faces.

5- Reduced manoevering forces required on the actuators because the water reactions act all on a horizontal plane discharging the efforts manly on the bushing of plate supports .

6- Simplicity and low cost of the housing units particularly because it could be easy standardised: 4 or 5 housing models could be cover a high range of boats of different lengths and types considering that the rudder blades or the fins only should be changed.

7- Easy and simply installation on board also considering that the couple of units are each independent without any mechanical connection like rudder stock connecting rod etc. living in this way free space for a cabin, tender lodgement etc.