US 3145681 A
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Aug. 25, 1964 ETSUO NAKAGAWA 3,145,681
HULL CONSTRUCTION Filed June 24, 1965 3 Sheets-Sheet l g- 1964 s'rsuo NAKAGAWA HULL CONSTRUCTION 5 Sheets-Sheet 2 Filed June 24, 1965 Fl Mix V Aug. 25, 1964 ETSUO NAKAGAWA 3,145,681
HULL CONSTRUCTION Filed June 24, 1963 3 Sheets-Sheet 5 United States Patent This invention relates to hull constructions. It is an object of the invention to provide an improved hull constructed to decrease the longitudinal bendingmoment acting thereon.
It is known that oil tankers, ore carriers and the like are becoming larger and larger. In such ships, the larger longitudinal bending moment acting on the hull inevitably results in its hogging and sagging. Accordingly, reinforcement members acting against longitudinal moments for preventing the breaking down of the hull have been enlarged resulting in substantial increases in hull weight.
Conventially, the divided fore and aft sections of a hull are connected to each other by pins at their upper end parts near the deck, and have confronting ends inclined to provide a wedge-shape space for accommodating the bending moment which acts on the hull due to hogging.
Also, on said end parts, projections and concave parts slidably inter-engage to guide relative rotating movement of the fore and aft sections of the hull and to prevent torsion. Further, plates are mounted aside said wedgeshape space to prevent sea-water turbulence which increases resistance.
With constructions of hulls in the prior art, it has been necessary to widen the wedge-shape space provided at the ends of the hull. Otherwise, under hogging conditions the fore hull end and aft hull end may collide and break down. However, if said space is made larger, the plates mounted aside the wedge-shape space must be huge. Hence, not only does the machining therefor become diflicult, but also the plates are likely to deform and break down due to Waves or contact with quays when approaching the same.
Furthermore, as the projection and concave parts, which guide the rotary movement around the joining pins of the fore and aft sections of the hull at their confronting ends and which prevent torsion of the fore and aft sections of the hull, are required to be larger, the construction thereof becomes very complicated and sagging increases. Then, if engagement between the projections and concave parts is released due to increased sagging, the torsion movement acting on the hull must be resisted by the pins only, and the pins may break thus disassembling the fore and aft sections of the hull.
Accordingly, an object of this invention is to provide a hull construction without the above-noted defects in which a fore hull section and an aft hull section, divided transversely, are joined together in such a manner that rotary movements of each section in the up and down direction along the transverse center line are free to decrease the longitudinal bending moment acting on the hull.
Other objects and advantages are also effected by the invention, as will be apparent from the following description and claims taken in connection with the accompanying drawing, in which:
FIGURE 1 is a plan view of joined sections of a hull;
FIGURE 2 is a side view thereof;
FIGURES 3, 4 and 5 are sectional views along lines III-III, IV-IV and VV of FIG. 1, respectively; and
FIGURES 6, 7 and 8 are side views of the hull with sections joined together, showing respectively the states of floating on still water, hogging and sagging.
3,145,681 Patented Aug. 25, 1964 In the drawing, element 1 is the fore section of a hull which is transversely divided along an appropriate central portion thereof. Element 2 is the aft section. At the confronting ends of the fore section 1 and the aft section 2 of the divided hull, there are provided, respectively, projections 5, 5 and 6, 6, 6" which extend across the width of the hull in half-cylindrical or semi-circular form defining a common aXis near the middleof depth of the hull, and half-cylindrical concave portions 8, 8', 8" and 7, 7' which respectively confront said projections 6, 6, 6 and 5, 5' and which are inserted therein in hinge form.
Elements 9, It 11, 12 and 13 are shaft tubes transversely penetrating through the centers of the half-cylindrical projections 5, 5' and 6, 6', 6" respectively. These are in a transverse rectilinear arrangement. Shaft sections 3 and 4 are rotatably inserted through the shaft tubes 9, 10, 11, 12 and 13. The shafts 3 and 4 rotatably connect the fore and aft sections 1 and 2 of the hull with each other. Elements 14- and 15 are respectively the longitudinal and the transverse bulkheads.
In FIGS. 2 to 4, angle 6, with its center on the axis of shaft 3, is the relative rotational angle of sagging between the fore section 1 and the aft section 2 of the hull, and 0 is the relative rotational hogging angle between the fore section 1 and the aft section 2 of the hull. The maximum permissible angles 0 and 0 vary in corre spondence to the radius R of the half-cylindrical projections 5, 5' and 6, 6, 6" and to the dimension of space C provided at the opposed ends of the fore section 1 and the aft section 2 of the hull. The maximu mangles 0 and 0 allowable may thus be set as desired by selectively adopting appropriate values of R and C according to the size of the ship and that of the waves on its voyage.
If necessary, adequate reinforcements can be added to the shaft tubes 9, it), 11, 12 and 13 which accommodate the shaft sections 3 and 4 connecting the fore section 1 and the aft section 2 of the hull and to the parts of the hull Whereon the shaft tubes are fitted.
When floating on still water as shown in FIG. 6, the hull of the above construction is in rectilinear disposition. However, if the hull is brought to hogging or sagging conditions by waves as respectively shown in FIGS. 7 and 8, the fore and aft sections 1 and 2 (the latter having a rudder and propeller) of the hull may smoothly and freely turn relative to each other around the shafts 3 and 4. Therefore, a longitudinal bending moment acting on the transverse plane at the central part of the hull may be kept at zero.
As above mentioned, the hull of the present invention comprises half-cylindrical projections and concave portions conforming thereto on the opposed ends of the hull sections which constitute a transversely divided hull. The projections and mating concave portions extend across the width of the hull and define a center or axis around the middle of the depth of the hull. These projections and concave portions being engaged with each other, rotatably join the divided hull sections around the center of a cyllinder, thereby preventing longitudinal bending moments from acting on the center of the shaft of the hull. Accordingly, as no strengthening member is required in the hull, the structure becomes very simple and stable and lightweight.
Further, as the hull sections can make rotary movements very smoothly and freely in hogging and sagging conditions, this eliminates collisions between the fore and aft sections of the hull. Consequently, there is no fear that damage might occur.
It will be obvious to those skilled in the art that the invention is not limited to the specific construction disclosed herein, but covers all modifications and variations within the scope of the following claims without departing from the spirit of the invention.
What is claimed is:
1. A hull construction comprising at least two hull sections in longitudinally aligned relationship, each of said hull sections including longitudinal extending bulkhead plates and shell plates, said sections including facing end portions, one of said end portions including at least one semi-cylindrical projection having side members, said side members being integral extensions of the plates of said one section, the other of said end portions including at least one semi-cylindrical recess having side members, said side members of said recess being integral extensions of the plates of said other section, said projection and said recess being in substantially mating relation and defining a common horizontal axis located at about the center of the hull with respect to the height thereof, and means for coupling the hull sections together for relative rotation about said axis.
2. A construction as claimed in claim 1 wherein each end portion includes a plurality of said projections and is provided with a plurality of said recesses between said projections, the projections and recesses extending transversely of the hull, said end portions being fit together to constitute a hinge structure.
3. A construction as claimed in claim 2 wherein said means comprises at least one shaft section extending 25 4 means comprises axially spaced shaft sections extending through said projections to connect said hull sections.
5. A construction as claimed in claim 2 wherein the diameters of the recesses exceeds the diameter of the projections for defining the angle of relative rotation about said axis.
6. A construction as claimed in claim 2 wherein the diameters of the recesses and projections are substantially equal .to the height of the hull.
7. A construction as claimed in claim 2 wherein the hull sections are of substantially the same length.
8. A construction as claimed in claim 2 wherein one of the hull sections includes both of the outermost projections.
9. A construction as claimed in claim 2 wherein one of the hull sections includes a propeller and rudder.
10. A construction as claimed in claim 2 wherein the projections and recesses extend entirely across each of the hull sections.
References Cited in the file of this patent UNITED STATES PATENTS 2,715,380 Archer Aug. 16, 1955 3,035,536 Archer May 22, 1962 FOREIGN PATENTS 349,647 France Apr. 5, 1905 5,234 France Dec. 2, 1905