Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
DEVICE FOR INCREASING THE YAW STABILITY IN SHIPS
Document Type and Number:
WIPO Patent Application WO/2005/012075
Kind Code:
A1
Abstract:
A device for increasing the yaw stability of a ship (1) with a bulb (3) and an azimuth propeller drive device (7) which is mounted at the ship's (1) bow (2) and stern (6). According to the invention a bow fin keel (5) protrudes downwardly from the bulb (3), and at the ship's (1) stern (7) at least one stern fin keel (21, 22) protrudes downwardly from each of the ship's sides.

Inventors:
Moe, Stig Endre (Solsvingen 14, Ålesund, N-6014, NO)
Vartdal, Leif (Ulsteinvik, N-6065, NO)
Nerland, Kåre (Ulsteinvik, N-6065, NO)
Borgen, Henning (Kaptein Linges vei 80, Ålesund, N-6006, NO)
Application Number:
PCT/NO2004/000234
Publication Date:
February 10, 2005
Filing Date:
August 02, 2004
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
Rolls-royce, Marine AS. (Ulsteinvik, N-6065, NO)
Moe, Stig Endre (Solsvingen 14, Ålesund, N-6014, NO)
Vartdal, Leif (Ulsteinvik, N-6065, NO)
Nerland, Kåre (Ulsteinvik, N-6065, NO)
Borgen, Henning (Kaptein Linges vei 80, Ålesund, N-6006, NO)
International Classes:
B63B1/06; B63B39/06; B63H5/08; B63H5/125; (IPC1-7): B63B39/06; B63B3/38
Domestic Patent References:
WO2000068072A12000-11-16
WO2000007872A12000-02-17
WO1989005262A11989-06-15
WO2001007314A22001-02-01
Foreign References:
US3934531A1976-01-27
EP0269272A11988-06-01
EP0134767A11985-03-20
US5575230A1996-11-19
US5163377A1992-11-17
Other References:
DATABASE WPI Week 199631, Derwent World Patents Index; Class Q24, AN 1996-305720, XP002983241
Attorney, Agent or Firm:
Onsagers AS. (P.O. Box 6963 St. Olavs plass, Oslo, N-0130, NO)
Download PDF:
Claims:
CLAIMS
1. A device for increasing the yaw stability of a ship (1) with a bulb (3) and an azimuth propeller drive device (7) which is mounted at the ship's (1) bow (2) and stern (6), characterised in that a bow fin keel (5) protrudes downwardly from the bulb (3) and is securely fixed thereto and that at the ship's (1) stern (7) respective stern fin keels (21,22) protrude downwardly from each of the ship's sides.
2. A device according to claim 1, characterised in that the bow fin keel's (5) draught corresponds to the draught of the ship's keel (4).
3. A device according to claim 1 or 2, characterised in that in the forward direction the bow fin keel (5) is terminated on a level with the front portion of the bulb (3).
4. A device according to one of the preceding claims, characterised in that the stern fin keels' (21,22) draught corresponds to the draught of the ship's keel (4).
5. A device according to one of the preceding claims, characterised in that in the astern direction the stern fin keels (21, 22) are terminated on a level with the ship's stern (13).
6. A device according to one of the preceding claims, characterised in that the azimuth propeller drive device (7) comprises at least one azimuth propeller drive unit (11, 12) which is mounted substantially between the stern fin keels (21,22).
7. A device according to claim 6, characterised in that the azimuth propeller drive unit (11, 12) comprises a gear housing (14) which is rotatably connected to a body (17) which is securely fixed to and protrudes downwardly from the ship's hull (16), and the body (17) is in the form of a fin keel and contributes towards an increase in the yaw stability.
8. A device according to claim 6 or 7, characterised in that the azimuth propeller drive device (7) comprises two azimuth propeller drive units (11,12) which are mounted side by side in the ship's (1) transverse direction.
9. A device according to claim 7 or 8, characterised in that the gear housing (14) supports a downwardly protruding fin keel (19) which acts as a rudder.
10. A device according to one of the preceding claims, characterised in that at least one of the fin keels (5,17, 21,22) is streamlined.
11. A device according to one of the preceding claims, characterised in that at least one of the stern fin keels (5,17, 21,22) is rotatable about a vertical axis.
12. A device according to one of the preceding claims, characterised in that at least one of the stern fin keels (5,17, 21,22) has at its rear portion a flap (25) which is rotatable about a vertical axis.
Description:
Device for increasing the yaw stability in ships The invention relates to a device for increasing the yaw stability in ships as indicated in the introduction to claim 1.

The use of an azimuth propeller drive device for ships is advantageous since such a drive device gives the ship good manoeuvring characteristics as its propeller can be swivelled about a vertical axis relative to the ship. Furthermore, the loading capacity of ships with such a drive device can be increased, in addition to which further functional advantages can be obtained.

A disadvantage of azimuth propeller drive devices, however, is that when the ship is underway there is little yaw or course stability, particularly if autopilot is employed.

This can be noticed as a continuous, relatively substantial change of direction or turning relative to a mean course, which is a disadvantage since it leads to increased fuel consumption, reduced sailing speed and increased wear on the drive and steering device. Attempts have been made to eliminate these drawbacks by, e. g. changing steering algorithms and the use of stabilisers.

Furthermore, tractive azimuth propeller drive devices have been employed, i. e. drive devices where the propeller is located in front of the gear housing in which the propeller is mounted, and in front of the vertical axis round which the gear housing can be swivelled, but the results so far have not been satisfactory.

The object of the invention is to provide a device of the above-mentioned type which substantially reduces the above-mentioned drawbacks.

The characteristic of the invention according to the invention will become apparent in the characterising features indicated in the claims.

The invention will now be described in greater detail with reference to the drawing which illustrates an embodiment of the device according to the invention.

Fig. 1 is a perspective view of a bow portion of a ship, as seen from the ship's starboard side and looking aft.

Fig. 2 is a perspective view of a stern portion of the ship, as seen from the ship's starboard side and looking aft.

Fig. 3 is a perspective view of the stern portion viewed from the ship's port side and looking forward.

As can be seen in fig. 1 a ship 1 has a bow portion 2 with a bulb 3. From the bow portion 2 a keel 4 of the ship 1 extends astern. A bow fin keel 5 protrudes downwardly from the bulb 3 and is securely fixed thereto. The bow fin keel's draught corresponds substantially to the draught of the ship's keel 4. Furthermore,

the bow fin keel 5 is terminated in the forward direction on a level with the front portion of the bulb 3. It will be understood, however, that if there is no need for such a large bow fin keel 5, its draught may be less than that of the keel. The bow fin keel 5, moreover, may be terminated astern of or in front of the front portion of the bulb. A bow fin keel 5 of this kind counteracts a yawing or turning of the ship 1 about a fulcrum or axis of rotation behind the ship's bow.

As illustrated in figs. 2 and 3, at the ship's stern 6 there may be mounted an azimuth propeller drive device 7 comprising two identically shaped azimuth propeller drive units 11, 12, which are arranged side by side a short distance in front of a stern 13 of the ship and symmetrically around a vertical symmetry plane of the ship. The ship, however, may have only one such azimuth propeller drive unit or more than two thereof. If a drive unit is provided in addition to the two mentioned above, the additional drive unit may be mounted midway between the two above-mentioned units.

Each azimuth propeller drive unit 11,12 has a gear housing 14 with a substantially horizontal, forwardly extending drive shaft (not shown) which carries a propeller 15 in front of the gear housing 14. These drive units are therefore called"tractive". The upper portion of the gear housing 14 is connected to a body 17 in such a manner that the gear housing 14 can be rotated e. g. 360° about a substantially vertical axis 18 relative to the body 17. The upper portion of the body 17 in turn is securely fixed to the hull 16. To the gear housing 14 there is attached a fin keel or gear housing fin keel 19 which can act as a rudder on rotation of the gear housing 14. The body 17 may be in the form of a fin keel or a drive unit fin keel for the drive unit 11,12, where this drive unit fin keel 17 also helps to increase the ship's yaw stability.

At each side of the ship's stern there are respective downwardly protruding stern fin keels 21,22 which are securely fixed to the hull 16. The stern fin keels'draught corresponds to the draught of the ship's keel, but it will be appreciated that it may be less. In the astern direction the stern fin keels 21,22 are terminated on a level with the ship's stern. This provides a maximum distance between the stern fin keels 21, 22 and the fulcrum or axis or rotation round which the ship may yaw and correspondingly maximises the stern fin keels'contribution to the yaw stability. It will be appreciated, however, that the stern fin keels may be mounted some distance in front of the ship's stern.

Instead of the stern fin keels being securely fixed to the hull, they may be connected to the hull in such a manner that they can be rotated round respective vertical axes.

Alternatively, each stern fin keel can have at its rear portion a pivotable flap 25 (indicated by dotted lines at the starboard stern fin keel 21) in order to provide an improved yaw stability for the ship, as the rotatable fin keels or flaps can interact with a steering device with a suitable steering algorithm to counteract yawing.

Stern fin keels that can be rotated at least 90° can also be advantageous in order to increase the effect of the azimuth propeller drive units when they have been rotated so that their thrust is exerted at an angle relative to the ship's longitudinal direction, e. g. during manoeuvring when the ship comes alongside a quay. By simultaneously rotating the stern fin keels, the object can be achieved that they offer minimal resistance to the water flow towards and away from the drive units.

It is advantageous for some or all of the above-mentioned fin keels to be streamlined.

For cargo ships in particular the fulcrum for the ship's yawing motion may be moved relatively far forwards or backwards dependent on the ship's draught and trim. It is therefore highly advantageous to provide a bow fin keel and/or at least one stern fin keel. The effect of the bow fin keel and the stern fin keels varies depending on the location of the fulcrum. If the fulcrum is located nearer the bow than the stern, the effect of the bow fin keel will be relatively slight and the effect of the stern fin keels will be great and vice versa.

If so desired, in addition to or instead of the two stern fin keels, other fin keels may be mounted at the ship's stern, e. g. a central fin keel (not shown) similar to the above-mentioned stern fin keels and extending in the ship's centre plane.