Marine propulsion – Screw propeller
Patent
1984-10-31
1986-05-06
Basinger, Sherman D.
Marine propulsion
Screw propeller
440 53, 440112, B63H 114
Patent
active
045869073
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Offshore vessel, especially those of the semisubmersible type, are often equipped with thruster propellers, which are rotatable 360.degree. and are used for propulsion, steering as well as for positioning of the vessel. Mounting and dismounting of these thruster propeller units is a difficult and tedious work.
As the propeller units are mounted below the bottom plating of the vessel, the space within the latter, adjacent to the location of mounting, must be separated from the surrounding water. An occasional screening around the opening, where the propeller unit is to be mounted, can easily be arranged, but the lines used for performing the terminating part of the lifting of the unit into the opening has hitherto caused many problems.
Usually there is a vertical tube for each line, which from a hole in the bottom plating, within the vessel, reaches up to or somewhat above the water level. As the decks of the pontoons carrying the semisubmersible vessel during a mounting operation will be located just above water level, the space remaining for the lifting gear will be rather restricted. The required space for the lifting gear must be provided above the deck of the pontoon, in localities needed for other purposes, for instance as bunker or ballast tanks.
SUMMARY OF THE DISCLOSURE
The aim of the present invention is to propose efficient means, which do not require much space, for passing a lifting line through the bottom plating, and which permits some sideward movement of the line.
The invention thus proposes a means for mounting a thruster propeller unit in an opening in the bottom structure of a vessel and comprising at least two lifting lines, operable from inside the vessel, passing out through the bottom plating outside of the opening and being attachable to the thruster propeller unit, when the latter has been brought to a position adjacent to the opening. The invention is characterized in that each lifting line is passed through a lock chamber at the bottom plating, and adjacent to the latter includes a first, rigid tubular member, enclosing a passage substantially wider than the diameter of the lifting line, as well as a second, tubular member being resilient at least transversely to the lifting line, the second member, at its end remote from the bottom plating carrying a packing sealing around the lifting line.
The lock chamber is preferably connected to a source supplying a gaseous fluid at a pressure suited to balance the pressure of the surrounding water. The first tubular member is advantageously formed as the housing for a closure valve.
The second, resilient member preferably includes a bellows-shaped portion, fitted between two flanges, which are held together by means of a number of sidewardly movable, rigid rods. The upper of the two flanges, through which the lifting line passes out from the lock chamber, is preferably provided with a sealing sleeve comprising a number of split rubber washers.
A cowl operable from within the vessel and adapted to close the mounting opening is preferably formed and adapted to permit a watertight fitting of the thruster propeller unit in the portion of the bottom plating surrounding the opening during a preliminary stage of the mounting operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will below be described with reference to the accompanying drawings, in which:
FIG. 1 shows an end view of a semisubmersible offshore vessel during the mounting of a thruster propeller unit,
FIG. 2 shows a cross section through a portion of one of the pontoons of the vessel, and
FIG. 3 shows a detail of the lock chamber at the lift line.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Thruster propellers may be used with various types of vessels and floating bodies, and the offshore vessel shown in FIG. 1 is one example of a possible use. The figure illustrates one manner of mounting and dismounting the housing of a thruster propeller unit.
The offshore vessel shown comprises a working platform 10, which by means of columns 11 is
REFERENCES:
patent: 1771250 (1930-07-01), Feild
patent: 1902360 (1933-03-01), Foster
patent: 2746709 (1956-05-01), Minor
patent: 4036163 (1977-07-01), Pehrsson
patent: 4456267 (1984-06-01), Bacharach
Basinger Sherman D.
Gotaverken Arendal AB
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