Ships – Towing or pushing – Towing by means of cable
Reexamination Certificate
2002-07-10
2004-03-02
Avila, Stephen (Department: 3617)
Ships
Towing or pushing
Towing by means of cable
C114S254000
Reexamination Certificate
active
06698374
ABSTRACT:
The invention relates to a tugboat. The design comprises a towing installation which can turn through 360° in the horizontal plane, and beneath which there are one or more propellers. This design provides optimal thrust in all directions in line with the towing cable, in combination with good resistance and swell properties.
In harbours and restricted sailing areas, ships are usually assisted by one or more tugboats. The ship and the tugboat are firstly connected by cable. The tugboat sails with the ship and positions itself in such a manner that it can tow the ship in a specific direction by means of the towing cable. During these manoeuvres, it is also possible for a tugboat to be manoeuvred against the ship in order to be able to push it.
During towing, there is a cable connection between the tugboat and the ship. On board the tugboat, this cable usually runs through a towing eyelet and is attached to a towing winch or towing hook. The towing eyelet is arranged as low as possible in the vertical direction on the tugboat, in order to minimize the tilting of the tugboat and to prevent the tugboat from capsizing.
With respect to this towing eyelet, the towing cable can turn sideways through 90° or more in the horizontal plane, towards both boards.
In the case of a towing winch, the cable length can be adapted to the desired towing length and manoeuvring distance. In the case of a towing hook or attachment point, the towing cable length is fixed.
On older models, there is only a winch and a towing eyelet at the stern; in many modern tugboats, a towing eyelet and towing winch are arranged both fore and aft.
During manoeuvring, the tugboat turns with respect to the ship, but on account of the design of the towing eyelet, the tugboat can only turn to a limited extent with respect to the towing cable connection. In this embodiment, the towing installation cannot produce a towing cable connection in all directions independently of the direction of the tugboat (i.e. the longitudinal axis of the ship). It is also not possible for the towing cable to turn through a full 360°, since the towing cable then comes into contact with the deckhouse.
A tugboat provides propulsion by means of one or more screws. Many ships are equipped with two screws positioned next to one another. In older models, these screws are positioned aft beneath the ship by means of a propeller shaft. In this case, the thrust is produced predominantly in the longitudinal direction of the ship. This direction is also directed partially sideways by means of rudders. Modern tugboats are often equipped with so-called thrusters. In this case the entire screw/propulsion unit can turn in the horizontal plane and thrust can be produced in any desired direction. In a number of models, these thrusters are arranged beneath the stern (a so-called azimuth-stern-drive tug), and in a number of models the thrusters are arranged roughly ⅓ of the length from the forward part of the ship (a so-called tractor tug).
In all these designs, there is a horizontal distance in the longitudinal direction of the ship between the resultant propulsive force and the direction of the towing cable. In a number of directions (for example the longitudinal direction), this horizontal distance is zero, but in other directions (for example sideways), this distance is relatively great.
The optimum towing force is obtained if the resultant propulsive force in the horizontal plane is in line with the direction of the towing cable; for this purpose, therefore, the tugboat always has to adopt the desired position and direction.
An exception to this is formed by so-called “dish” designs, i.e. convex, round hull shapes without a clear sailing direction; i.e. the ship can sail both forwards and sideways. In addition, the ship can also turn relatively quickly about its axis. These designs have a small length/width ratio. However, this form of ship has a high resistance, with the result that the design can only reach a moderate speed. During towing, the ship's direction is selected in such a manner that the towing eyelet is positioned in the direction of the vessel which is to be towed. Examples of this include the OMNI 2000 (Robert Allen Ltd) and the Ship Docking Module (SDM) Hvide design (Halter Marine USA). These two designs are distinguished by a flat, shallow hull with one thruster at the front on one board and the other thruster at the stern on the opposite board. Similar designs are based on a roughly round shape with two, three or more thrusters. However, this form of ship has an adverse effect on the resistance of the ship (in particular at increasing speeds), and results in a poor sailing performance in rough seas. In many cases, it is impossible to sail on the sea.
Furthermore, conventional tugboat designs are aimed at achieving a high thrust at low speed during towing, the hull shapes being conventional and unsuitable for reaching (relatively) high speeds.
It is clear from this that there are no satisfactory solutions for obtaining the full thrust in line with the towing cable, independently of the ship's direction and in combination with good resistance and swell properties.
The object of the present invention is to provide an improved device which does not have the drawbacks described above, i.e. to obtain full thrust in all directions in line with the towing cable, independently of the ship's direction and in combination with good resistance and swell properties.
This object is achieved by arranging a towing installation which can turn through 360° in the horizontal plane and can rotate irrespective of the direction of the tugboat. This turnable towing installation may comprise all designs which are known in the prior art. It is possible for a conventional towing winch, possibly in combination with a towing eyelet, to be placed on a rotatable platform. Another possibility is for a winch drum to be positioned so that it turns around a vertical shaft. The winch drum and towing eyelet may comprise all designs which are known in the prior art, of numerous forms and dimensions. In addition, the winch drum can be driven in numerous ways.
According to another advantageous design, the towing installation rotates about a predominantly vertical connection to a facility for visual observation of the surrounding area. This facility may comprise all designs which are known in the prior art.
The facility may comprise a visual recorder which records information about the surrounding area and makes this information available for steering the ship. In this case, consideration may be given to a camera with electrical information exchange or an optical installation (with lenses/mirrors) which transmits light rays.
The facility may also comprise an (observation) station for one or more people. In this case, consideration may be given to a deckhouse at which one or more people may be stationed.
According to another advantageous design, the (observation) station for one or more people also includes a steering/operating installation for the tugboat.
According to another advantageous design, the (observation) station for one or more people is positioned at the top side of the vertical shaft, so that the towing installation can rotate without interference. This design produces a low point of action of the towing cable on account of the low position of the towing installation and good visual observation of the surrounding area on account of the high position of the (observation) station. If the steering/operating installation is also arranged at this (observation) station, it is possible for one or more people to manoeuvre the tugboat.
According to another advantageous design, the vertical shaft is designed to have a considerable diameter, resulting in a relatively flat drum of large diameter. The lower height of the drum produces a lower point of action, with the result that the tugboat is much less prone to capsizing. In addition, the flat drum leads to a shorter arm, so that the shaft is better able to absorb the bending moment.
The large diameter of t
Avila Stephen
Browdy and Neimark , P.L.L.C.
Novatug B.V.
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