Patent Application
20140090588
On today's motorized craft, for steering, one or more traditional rudders are used, generally consisting of a blade provided with a torsion shaft maneuvered from inside the hull. Similar system is used for stabilizing devices. Those kinds of appendages are normally maintained immersed during navigation also when not utilized with the drawback of a power consumption particularly on fast boats such as motor yachts, patrol vessels, catamarans etc, considering also that this power consumption increases not proportionally but with the square of speed.
Another drawback less evident but not less important that will be better illustrated at the end of the present Description and in
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 '90s a steering system has been studied and realized maintaining the rudders retracted on board during course but configured 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 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 limited percentage times and also with limited incidences during the normal steering on course, obtaining a considerable fuel saving.
On this basis a steering apparatus has 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 p Application PCT E 518 229 A1 to Brighi/Harrauer)
This known kind steering device yielded favorable results in that a watercraft navigating in course with retractable rudders shows no greater instability that 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 tradition in the marine field and because the installation of the equipment attached and projecting outside of the transom created fear that some collision while 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 port side and on starboard side each provided with a retractable rudder blade essentially connected to a prismatic guide element, vertically sliding inside a tubular housing movable by an actuator contained inside the casing, so that it can be retracted or projected out to a variable extent in water as shown in
This system also did not have diffusion on the market manly for two reasons: the first one being that 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 consisted in the difficulty of bringing outside 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 stabilization also. All these problems are resolved by the system described herein.
This is in short the state of the prior art stage for steering systems to our knowledge.
The equipment object of the invention has the particularity to be used also as a stabilization device in conditions of rough sea but also in certain situations at high speed when the boat takes a swinging tendency creating serious concerns on board.
The antirolling stabilization equipment of today consists generally in a pair of fins similar to rudders outstanding on both sides of the boat under water level, these fins rotating on their axis and automatically maneuvered from inside board being capable to create a torque opposed to that torque created by rough sea.
This kind of fins in smaller craft is normally permanently maintained outside the board, being power consumption limited, while in faster and more evolved craft a suitable chamber is provided where the entire apparatus can be totally retracted by mechanisms that are very complicated and expensive because the fin must receive in any case both rotating and translating motions.
The system object of the invention is constructively the same whether used for steering or for stabilization of the craft during navigation, and includes at least two units each contained in a watertight housing to be installed one on starboard side and the other on port side. Particularly in case of steering gear, the units will be placed with their vertical axis abaft the ship while, in case of stabilization gear, will be placed near the middle of the ship prevalently with a horizontal axis. Each unit contains inside a blade (or a fin) provided with a moving device, capable to retract or to project the fin outboard partially or totally when necessary for steering or for stabilizing, passing through 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 seal 49 to maintain watertight the housing and at same time to receive a remote control by any kind of electric or hydraulic actuator and at same time to transmit remote information on fin position.
The system will better illustrated by the enclosed drawings.
In these figures we can see that the blade 1 is characterized by having a curvilinear profile, in order to permit an easy and complete outlet from the watertight housing 3 obtaining a considerable volume reduction. The angle of incidence of the blade will be constant or variable along the axis of the blade according to 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 tall than the cover 33 but sufficient to locate two side bearings 31/32 proportioned to support all forces of lifting and drag generated from 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 shown in the figures after interposal of an adequate tested seal 49 capable of providing a perfect water tightness.
About the quality of the materials, a strong material such 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 for the section 33 having only cover function a fiber glass or aluminum material could be appropriate being light and not expensive.
The inferior section of the housing 3 will be provided with appendages like 36 to be coordinated with the shipyard in order to connect the housings to the craft. In standard production the components 1-2-21-22-4 can be realized in only one piece.
The bearing 31/32 connected to the housing sides 3 will consist preferably of two hubs 43/44 in order to facilitate assembling and disassembling. Each is provided with long service bushing 46/47 capable of resisting sea water and supporting all forces of lifting and drag transmitted by the blades. In case that the units will be used as a stabilizing system and, with particularly 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 seal 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 a signal of the blade position may be installed, being this signal very important as feedback for the electronic controls.
The advantages consequential to the use of the described system are:
1—Lower fuel consumption or higher speed because the rudder blades or fins are retracted when they are not used.
2—Less fuel consumption sailing in rough sea due to the yawing reduction as represented in
3—The asymmetric drag due to the single rudder exposed only inside the veering, see
4—The rudder exposed only inside the veering could be provided with a hydrodynamic profile having a better lifting feature than the conventional one requires a symmetric profile to work with both faces.
5—Reduced maneuvering forces on the actuators because the reactions of the water act all on a horizontal plane discharging the efforts manly on the bushing of the plate supports.
6—Simplicity and low cost of the housing units particularly because it could be easy standardized: 4 or 5 housing models could be cover a high range of boats of different lengths and types considering that only the rudder blades or the fins should be changed.
7—Easy and simple installation on board, also considering that the couple of units are each independent without any mechanical connection like a rudder stock connecting rod etc., leaving free space for a cabin, tender lodgment etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| GE2011 A000053 | May 2011 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/058634 | 5/10/2012 | WO | 00 | 12/17/2013 |
