Ships – Steering mechanism – Remote control steering excluding manual operation
Patent
1984-11-26
1986-09-16
Blix, Trygve M.
Ships
Steering mechanism
Remote control steering excluding manual operation
74480B, B63H 514
Patent
active
046115498
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a rotation control system for use in a vessel such as a tug boat.
BACKGROUND ART
In recent years, harbors have become much crowded with vessels of a large size, and therefore it has been required that tug boats should operate to move the vessel toward and away from the shore in a safe and rapid manner. For this reason, there have now been extensively used tug boats equipped with a Z-type propulsion apparatus which can easily vary the direction of propulsion over the range of 360 degrees. In such a Z-type propulsion apparatus, for example, shown in FIG. 1, the rotation of a main engine 1 is transmitted to an input shaft 6 via a universal joint 3, an intermediate shaft 4 and a universal joint 5 when a clutch 2 is connected, and the rotation of the input shaft 6 is transmitted to a propeller 12 attached to a propeller shaft 11 via bevel gears 7, 8, 9 and 10 so that the propeller 12 is rotated to advance the vessel. At the same time, the rotation of a hydraulic motor 14 controlled by a rotation control unit 13 is transmitted to a hollow rotary housing 17 via a worm gear 15 and a worm wheel 16 to angularly move the rotary housing 17 so that the direction of propulsion of the propeller 12 is changed to turn the vessel.
One conventional method of controlling the rotation of the Z-type propulsion apparatus is to control the speed of rotation of the hydraulic motor 14 with respect to the speed of rotation of the main engine 1. In such a conventional method, the main engine 1 drives a hydraulic pump so as to control the hydraulic motor 14. Alternatively, a motor drives the hydraulic pump to control the hydraulic motor 14. In the method in which the main engine 1 drives the hydraulic pump, the speed of rotation of the main engine 1 is detected and the angle of inclination of the hydraulic pump is controlled to be in inverse proportion to the speed of rotation of the main engine 1 so that the speed of rotation of the hydraulic motor 14 becomes constant. Alternatively, the speed of rotation of the hydraulic motor 14 is detected and the angle of inclination of the hydraulic pump is controlled so that the speed of rotation of the hydraulic motor 14 becomes constant.
Among these control methods, in the case where the vessel is equipped with the Z-type propulsion apparatus of the type by which a turning force exerted on the vessel is proportional to the square of the speed of travel of the vessel, it might be considered that the speed of rotation of the rotary housing is decreased to prevent an increase in the hydraulic drive force and an abrupt turning of the vessel when the speed of rotation of the main engine 1 is high. On the other hand, it might also be considered that when the speed of rotation of the main engine 1 is low, the speed of rotation of the rotary housing is increased to make use of the surplus of the hydraulic drive force and to rapidly turn the vessel.
However, vessels provided with such a Z-type propulsion apparatus are mostly used as tug boats. In the case where the tug boat has to carry out the mooring of a vessel, the speed of rotation of the main engine 1 is not always proportional to the speed of the boat or the number of revolution of the propeller. There are occasions when the speed of rotation of the main engine 1 is low while the speed of the boat is high and occasions when the speed of rotation of the main engine 1 is high while the speed of the boat is low. Therefore, in the method of controlling the speed of rotation of the rotary housing merely in inverse proportion to the speed of rotation of the main engine 1, the motor for driving the hydraulic pump is subjected to overload and is stopped by a safety device and also the hydraulic pump is damaged when the rotation of the main engine 1 is low while the speed of the boat is high (when the tug boat is tugged by the vessel). Also, when the speed of rotation of the main engine is high while the speed of the boat is low (when the tug boat tugs the vessel), a high speed of turning can not be a
REFERENCES:
patent: 4055135 (1977-10-01), Wesner
patent: 4301759 (1981-11-01), De Vries
patent: 4469041 (1984-09-01), Bilen
Aizawa Yasuo
Ichijo Kohji
Kodera Masanori
Avila Stephen P.
Blix Trygve M.
Niigata Engineering Co. Ltd.
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