Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to vessels for transporting cargo, and it
particularly relates to improvements in vessels in which the buoyancy of the
cargo is utilized to support a substantial portion of its own weight, leaving
the remaining, typically minor portion to be carried by the hull. In this
vessel, the hull serves to contain the cargo securely and at the same time to
provide a smooth external envelope of a desired form to minimize hydrodynamic
resistance; at the same time, the hull enables employment of buoyancy of the
cargo by always maintaining water within the hold common with the sea, by
means of permanent openings in the bottom of the hull for free passage of
water in and out. The vessels of this invention may have their floating cargo
loaded and unloaded into the hold by cranes, but in many instances the vessels
are preferably loaded and unloaded through a gate at either or both ends. The
vessels may also carry deck cargoes which are supported by the buoyancy of the
vessel and excess buoyancy of any floating cargo carried.
The invention is particularly helpful in transporting cargo of the
type that is shipped in barges or floating containers. A series of these
barges or containers is typically moved on water by a tugboat up to a location
adjacent the bow or stern of the vessel; then the series of barges or contain-
ers is loaded in through a gate in the bow or the stern. After the voyage,
the same series of containers is unloaded through a gate in the bow or stern
and towed away by a tugboat.
Many patents disclose vessels wherein the cargo-carrying hold of the
vessel is partially filled with water but only during loading and unloading.
Gates in the bow, in the stern or in the sides of the vessel have been used,
and various types of cargoes have been floated in and floated out. In these
vessels the practice has been to pump all the water out of the hold after the
cargo has been loaded, keeping the water out until the cargo is to be unloaded
so that the vessel carries the full deadweight of the cargo. In all these
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patentsl the water inside the hold is used only for floating the cargo into
and out from the hold, and water is never carried in the hold during the
voyage.
In contrast, United States Patent No. 3,356,058 to Thomas T. Lunde
discloses and claims a vessel for transporting logs. In this log-transporting
vessel of Lunde, there are a ballast system and ports through the hull to
achieve a flotation of part of the logs during the transport.
The present invention has the important advantage over the Lunde
device that it can be used for transporting barges or containerized cargo of
the type in which the containers can be floated in the water, whereas the
Lunde vessel cannot.
There exist well-known systems in which barges or lighters are
handled on a large high-speed, ocean-going vessel. One such system calls for
towing the barges or lighters out to the vessel where they are floated over
a submerged elevator which then lifts the barge or lighter out of the water to
a deck level where the barge or lighter is transferred over rollers to a final
stowage position. Another such system tows the lighters or barges out to the
vessel where they are hoisted aboard by large cranes on board the vessel.
These systems both are used so that large vessels need not be delayed in port
2Q by having to handle cargoes at a pier. They can also transport cargoes to
and from small ports that otherwise could not accommodate ocean-going vessels.
In many instances, this system of loading and unloading is more economical
than other marine transport systems.
In seeking to accommodate such barges or lighters on vessels
generally of the type of the Lunde vessel, there are problems that are not
encounterd in transporting logs. Logs have substantially identical specific
gravities, even though they are of different shapes and sizes. The cargo
containers that comprise the lighters and barges are normally identical in
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size and shape but, due to different degrees of loading, the containers vary
considerably in their specific gravities. To load them into a ship and then
allow-them to float freely would not be feasible. They would float at dif-
ferent levels, would tend to bob around, and could, under disturbed weather
conditions, exert forces that could severely damage their hulls as well as
the vessel's hull and might even cause the vessel to sink. Thus, there are
difficult problems in making it possible to employ the buoyancy of empty or
lightly filled lighters to help share the load of the heavily filled lighters
with the hull. It cannot be done with the device shown in the Lunde patent.
Yet, the solution of the problems gives rise to very beneficial results.
Problems relative to the loading and maintenance of the barges or
lighters, as well as of other floating cargo, and problems relative to the
specific situation described are also encountered.
Summary of the Invention
The present invention shares in common with United States Patent
No. 3,356,058 to Lunde the concept of employing buoyancy forces through the
use of a perforate hull and side walls of the vessel. However, the present
invention calls for securing means which hold floating containerized cargo
units, such as barges or lighers, in a positively fixed position during
transport, so that the bottoms of all of the units are in firm engagement
with the hull, and holding devices secured to the frame of the vessel and
spaced above the hull extend down from the deck level to engage the tops of
the units. Since individual barges or lighters usually have different den-
sities, depending upon their degree of loading and on the specific gravities
of their loads, those which are substantially empty or are lightly loaded,
provide a considerable amount of excess buoyancy. In the present invention
thi~ excess buoyancy is transferred through the securing devices so as to
enable the excess buoyancy effect to assist in supporting of the entire vessel
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and its floating cargo. Thereby, it becomes possible and practical to employ
a lighter weight design of hull construction and to transfer floating cargoes,
barges or lighters, through one end of the vessel directly from the ocean or
other body of water common to both the barges or lighters and the vessel.
In a broad aspect, the invention resides in a vessel for transport
of a floating buoyant cargo such as barges, ligh~ers, and pontoons, wherein
said cargo can be partially supported in the vessel by its own buoyancy, in-
cluding in combination: a hull having a bottom shell with rigid submarine
cargo-supporting and hull-reinforcing structure, a bow, a stern, and side
walls providing a series of buoyancy compartments, and a hollow enclosed in-
terior including a cargo hold, and conduit means communicating with said hold
for passage of water therethrough into and out from said hold, means for in-
troducing and expelling water from said buoyancy compartments to adjust the
draft, trim, and list of said vessel, gate means in said hull for opening to
enable flotation loading and unloading of said floating cargo and for closing
during transportation thereof, and securing means for releasably locking said
cargo in place in said hold against movement relative to said hull all during
a voyage of said vessel, with a lower portion of said cargo engaging said
submarine cargo-supporting structure, said securing means including means for
2Q engaging an upper portion of said cargo, whereby, when said hold is flooded,
the water in the flooded hold enables the buoyancy of the cargo to support the
cargo, at least in part.
Brief Description of the Drawings
In the drawings:
Figure 1 is a schematic view i;n side elevation of a vessel embodying
the principles of the invention and a series of barges or lighters previously
aligned for loading into the vessel; the portion of the barges or lighters
belo~ the waterline are shaded. The barges or lighters are also shown, in
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broken lines, in their final, transporting position within the vessel.
Pigure 2 is a schematic top plan view of the vessel and floating
containers of Figure 1.
Figure 3 is a view similar to Figure 1I showing the barges or
lighters just after the unloading operation.
Figure 4 is a view in side elevation and in section, somewhat
schematic in character, of a vessel embodying the principles of the invention
with the barges or lighters loaded and stabilized with the securing devices
as well as with deck cargo stowage. The bow gate is shown in solid lines in
its closed position and also is shown, in broken lines, in its open position.
Figure 5 is a plan view in horizontal section taken along the line
5 - 5 of Figure 4, showing the barges or lighters in their stowed position
.
for transport within the vessel.
Figure 6 is an enlarged view in cross section taken along the line
6 - 6 in Figure 4 showing the lighters held in stabilized position by means
of securing devices.
Figure 7 is a fragmentary view in elevation taken along the line
7 - 7 in Figure 6.
Figure 8 is a graph of tons per inch immersion plotted against the
2Q draft in feet of the vessel, showing the effect of buoyancy on the vessel
~ith and without barges or lighters stowed on board.
Figure 9 is a fragmentary view in side elevation and partly in sec-
tion of one of the hydraulic cylinders used in the securing device at adjacent
corners of two barges or lighters, these two having different densities and
shown floating at different levels.
Pigure 10 is a vie~ like Figure 9 with the members in their final
s~tabilized position, the hydraulic apparatus being fully extended and a
mechanical safety lock pin set in place.
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Flgure 11 is a fragmentary view in perspective of a portion of the
vessel near the bottom of the hull, showing one of the transverse box beams
or girders.
Figure 12 is a fragmentary view in section of a portion of the hull.
Figure 13 is a view in section taken along the line 13 - 13 in
Pigure 12.
Pigure 14 is a view in section taken along the line 14 - 14 in
Pigure 12.
Pigure 15 is a fragmentary view of a forward portion of the vessel
shnwing a modified form of bow gate. The gate is shown in broken lines in its
open position.
Pigure 16 is a plan view of the region of Pigure 15.
Figure 17 is a view in elevation taken along the line 17 - 17 in
Pigure 15, showing a swash bulkhead.
Figure 18 is a diagrammatic plan view of the buoyancy tanks and
pumping system.
Figure 19 is a diagrammatic plan view like Pigure 2 showing an
alternate form of loading system employing a single winch.
Pigure 20 is a diagram of an hydraulic circuit for operating all
of the securing devices simultaneously.
Figure 21 is a diagram of an hydraulic circuit for operating each
of the securing devices separately.
Figure 22 is a view similar to Figure 3 except that the unloading
is proceeding through a stern gate instead of a bow gate.
~igure 23 is a view similar to Pigure 4 of a vessel embodying the
principles of the invention and having both a bow gate and a stern gate, both
opening upwardly.
Figure 24 is a view similar to Pigure 19 showing discharge aft
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through a stern gate.
Pigure 25 is a fragmentary view of an aft portion of a vessel like
that of Figure 23 or Figure 24 showing a stern gate. Its closed position is
shown in solid lines, and its open position is shown in broken lines.
Figure 26 is a plan view of the region of Figure 25.
Pigure 27 is a view similar to Figure 10 showing a modified form of
hydraulic apparatus.
Figure 28 is a diagrammatic fragmentary view of three barges in
the hold before operation of the securing device, showing their individual
waterlines.
Figure 29 is a view like Figure 28 after operation of the securing
device showing the buoyancy effects of the barges after securing and illus-
trating transfer of buoyancy according to this invention.
Detailed Description of a Preferred Embodiment
In a vessel 10 such as that shown in the drawings, the ship 10 is
provided with a suitable hull 11 having a perforate bottom shell 12 with inlet
openings 13 that at all times are open to the body of water in which the vesel
lQ floats (See Figures 4 and 6). The shell 12 can be thin, for the water ex-
erts equal pressures on both surfaces thereof. The hull 11 is preferably
strengthened by bottom transverse box girders 14 to take a suitable load and
provide a rigid submarine cargo-supporting and hull-reinforcing structure,
the hull and girders being shaped so that there will be a flat surface 15 for
a series of identical floatable containers 16, such as lighters or barges.
The vessel 10 can also be used for transporting other buoyant cargoes.
The side walls 17 of most of the hull 11 comprise a series of
~atertight buoyancy tanks or compartments 18, each of which is provided with
ballast piping 18a (See Figure 18), connected to a ballast manifold 18b.
The manifold 18b is connected to a suitable ballast pump 19 for transfer of
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sea water into the buoy~ancy~ tanks 18 from a sea chest l9a and for transfer
of water out from the buoyancy tanks 18 into the sea via pipes l9b and l9c,
suitable valves being provided for control. Air vents 20 are provided on top
of the buoyancy tanks 18 to vent air in and out to the atmosphere as the tanks
are filled or emptied. The waterline of the vessel 10 is determined by the
weight of the cargo, the weight of the vessel 10, and the weight of the water
in the buoyancy tanks 18, as supported by the buoyancy of the vessel 10 and
the 6uoyancy provided by the barges and lighters 16. To control the draft
of the vessel 10, the buoyancy tanks 18 can be filled to any desired degree
to give any desired buoyancy or draft to the vessel as a whole and in combina-
tion with its barges or lighters. List and trim are controlled in the same
way, by selective fill of certain tanks 18.
At the aft end of the vessel 10 is a vessel propulsion portion 21,
which may be constructed substantially as is satisfactory in any such vessel,
and there may be suitable and necessary crew accommodationsJ etc.
A suitable gate for flotation loading and unloading is provided at
either or both ends of the vessel 10.
At the bow 22 of the vessel 10 of Figures 1 - 4 is a gate 23 which -
may, as shown in Figure 4J normally extend above the waterline and may be
sHung down about a pivot that is at all times below the waterlineJ to enable
the handling by flotation, of a series of containers 16 through it. The gate
23 is closed during the forward progress of the vessel 10 while enroute on
the voyage.
A modified form of bow gate 63 is shown in Figures 15 to 17. This
bow gate 63 opens upwardly about pivots 64 and includesJ spaced from the
actual gate, a swash bulkhead 65, which is a generally vertical plate with
openings 66 therethrough for preventing water from sloshing back and forth
for the full distance between the bow gate 63 and the front edge 67 of the
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first container 16.
As Pigure 22 shows, a vessel 10a embodying this invention may have
a stern gate 81, preferably opening upwardly for loading and unloading opera-
tions. Moreover, as Figure 23 shows, a vessel 10b, also embodying the inven-
tion may have both a bow gate 63 and a stern gate 81. Figures 25 - 26 show
the stern gate 81 in more detail. The gate 81 moves up around pivots 82 and
may carry with it one or more propulsion thrusters 83. The stern gate 81,
when used, is closed when the vessel 10a or 10b is transporting its cargo,
being raised only for loading or unloading.
When a vessel 10b is used having both a bow gate 63 and a stern gate
81, one gate may be used for loading and the other for unloadingJ thereby
achieving a first-in, first-out operation of floating cargo units.
As shown in Figures 1 and 3, a principal cargo for the vessel prefer-
ably comprises a series of containers 16, such as standardized covered lighters
or barges, each of which is a standard member and each of which is outfitted
~ith standard equipment. All the containers 16 are contemplated to be sub-
stantially identical in size and shape, and each has certain fittings, as shown
in some of the drawings such as in Figures 9 and 10, which may include cylin-
drical projections 25 at their upper ends 24 with frustoconical terminal pro-
jections 26 extending above the projections 25. They also preferably have
cylindrical recesses 27 at their bottoms 28 with frustoconical terminal
sockets 29. These are availed of to lock the containers 16 securely in place
during the voyage. Heretofore, they have been used mainly for stacking the
containers 16 on board a large ship, but the containers 16 are not stacked
in the hold of the present invention; they are all retained on the same level,
and these same fittings 25, 26 and 27, 29 are employed for stabilization of
the cargo. Other parts of these lighters or barges which are not essential
to the present invention are not shown. They are well known in most cases,
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and if other types are devised they can be adapted to this vessel or the
vessel can be adapted to them.
In a vessel lOb, the barges or lighters 16 are typically floated in
through the bow and out through the stern of the vessel in a train or tandem
series. Where there is only one gate, it is used for passage both in and out.
As shown in Figures 1 - 3, the containers 16 may be attached to each other by
ropes or cables 30, employing anchoring or winching at~achments that exist in
such containers as they are already made, so that each container 16 is linked
to a succeeding container 16. Tugboats 31 push or pull the trains. Normally,
due to various degrees of loading and various cargo densities, the containers
16 will not all float at the same level. In order that they float at the same
draft or water level, they would all have to be either empty or all loaded
with exactly the same amount and density of cargo. So a random probability
of drafts would be as shown in Figures 1 and 3, floating at different levels;
some are heavy with their upper ends 24 practically at the water level, while
others are light with their lower ends 28 nearly at the water level. The ves-
sel 10 is designed to accommodate such differences, so that during barge hand-
ling operations there is sufficient space 32 between the bottom transverse
hull girders 14 and the deck transverse girders 33, and that space is substan-
tially twice that of the height of the containers 16.
When the containers 16 are towed or pushed up to the vessel 10,
the bow gate 23 is opened so that the containers can be floated into the ves-
sel, ant when the containers 16 approach the vessel 10 closely, a pair of
winches 35 on the ship 10 are attached by cables 36 to the foremost of the
containers 16. The winches 35 are preferably located at about the center of
the vessel 10. There are pulleys 37 near the stern which are used during
loading and pulleys 38 near the bow 22 which are used during unloading. Thus,
during loading the cables 36 from the winches 35 go over the stern pulleys 37,
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one on the port and one on the starboard side of the vessel 10, and then one
is brought back to the bow 22 and through the gate 23 and attached to the
foremost of the containers 16. Then the winches 35 are powered to pull the
containers 16 into the hold 32; the tugboat 31, being disengaged, returns to
port. Other types of loading or container-propelling means could be used,
including a single winch 35 with a bridle 39 on the end of the line, as shown
in Figure 19.
When all the lighters or barges 16 have been brought inside the hold
32 of the vessel 10, they are roughly positioned with respect thereto. The
inside walls 40 of the buoyancy tanks 18 slope downward and inward, so that
the buoyancy tanks 18 are narrower at their upper ends than at their lower
ends, and along these side walls 40 are diagonal fender strips 41 of matting
or elastomer which protect the buoyancy tanks 18 from damage from the barges
and lighters. The buoyancy tanks may be deballasted by pumps 19 to lighten
the vessel so as to lift the heaviest laden of the barges or lighters 16 on
the cross girders 14 of the hull 11. The containers 16 are aligned during de-
ballasting so that they will eventually seat on bottom projections 44 located
on the girders 14 and enter the receptacles 27, 29 of the containers 16, there
aeing one such receptacle at each corner, as shown in Figures 9 or 10. The
2Q projections 44 each have cylindrical portions 45 ending in frustoconical por-
tions 46.
Above the containers 16 and suspended from the deck 33 is a series
of hydraulic (or pneumatic) devices 50, each of which comprises a stationary
housing 51 secured to deck girders 33 to which is secured a stationary piston
rod 52 and a stationary piston 53. A movable cylinder 54 is provided, and
to this cylinder 54 a movable spud or housing member 55 is secured by a
trunnion pin 56. Thus, when hydraulic or pneumatic fluid is sent by a port
57 into the space between the lower end of the piston 53 and the cylinder 54,
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the cylinder 54 is moved down and carries with it the outer spud 55. When the
fluid is applied by a port 58 between the piston 53 and the upper end of the
cylinder 54, the cylinder 54 is retracted upwardly. Each spud 55 of Figures
9 and 10 has a receptacle 59 suitable for engaging two, projections 25, 26.
As shown in Figure 27, each spud 55a unit may have a receptacle 59a
which engages only one projection 25, 26, and this receptacle 59a is shown on
a rod 52a of a movable piston 53a with this unit having a stationary cylinder
54a. Both types of spuds 55 and 55a have their advantages and disadvantages.
Either type may be used in conjunction with a modulating control valve of a
type well known so that all spuds move down at the same speed whether or not
they have engaged a projection 25, 26 and are pushing down on a load.
When the containers 16 are all engaged and pushed down to their
lowermost position, they are secured in placel and there is a buoyancy trans-
fer action which is novel. For example, as shown in Figure 28, each container
16 has its own waterline and typically, some containers 16 have a higher water- -
line than others. When floating freely, all three containers 16a, 16b and
16c of Figure 28 are buoyant, but the container 16a has the highest waterline `or deepest draft, and the container 16b has the lowest waterline or lightest
draft. When secured in place by the buoyancy transfer and securing means
described, they appear as in Figure 29; all held at the same level. Their
initial waterlines WlLl are shown as well as their present waterline W2L2
in Figure 29. The shaded portions in Figure 28 indicate the portions below
the original waterline WlLl while the shaded portions in Figure 29 indicates
the displacement of the original waterline WlLl from the new water line W2L2.
When the displacement is above the waterline W2L2 ~as it is for the container
16~, then the net effect is that a proportion of the weight of the container
(corresponding to the proportion of the shaded portion in Figure 29 to the
whole container) is weight borne by the hull 11. When the displacement is
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below the waterline W2L2 ~as for the containers 16b and 16c), then the effect
is to add upward buoyancy to the vessel 10 - to transfer a buoyancy corres-
ponding to the shaded portion of Figure 29 from the containers 16_ and 16c
to the vessel 10 and thus to cause the buoyancy of the containers 16b and
16c to help buoy up the vessel 10 and help carry the load of the shaded por-
tion of the container 16a.
The devices 50 may be actuated independently of each other, as shown
in Figure 21, but for most situations they are linked together to a single
control and operate simultaneouslyJ as shown in Pigure 20. The cables 30 are
left alone, becoming slack when the barges 16 are secured by the devicesl50
in position for transit.
In the Figure 20 form of the invention a single motor 47 and a
single pump 48 are usedJ with the cylinders 54 in parallel with each other;
in the Figure 21 form of the invention the motor 47 may operate a whole series
of pumps 49 in parallel with each otherJ with each pump 49 operating only one
cylinder 54.
As shown in Figures ll - 14, the vessel 10 may be constructed with
the transverse girders 14 in the form of watertight box girders with top
plates 70 and side plates 71 and 72 which are welded to the bottom plates 12.
The openings 13,(which may be conduits as shown in Figure 12J do not open into
the girders 14, which are watertight voids to provide buoyancy at all times.
The girders 14 are strengthened by perforate webs 73 and by angle irons 74
secured to plates 70, 71, and 72, the webs 73 having openings 75 through
w~ich the angle irons extend. The plates 70 are strengthened at the locations
where the projections 44 are located, as by thickening and by diagonal members
76 going to angle irons 74. Lengthwise, between successive girders 14, the
hull bottom 12 is strengthened by lengthwise-extending beams 77 such as
T~shaped beams. The buoyancy tanks 18 may also be strengthened by perforate
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webs 78 and angle irons 79 secured to the plates providing the walls of the
tanks 18.
The decks over the flooded hold may be hinged pontoons or removable
pontoons handled by the vessel's cranes 80, o:E which there are usually two,
located one on each side. A conventional mast and boom cargo handling system
may also be employed.
When the lighters or barges 16 are inside the hold 32 of the vessel
10, then the fluid is applied to the lower ports 57 of all devices 50 and all
s-puds 55 (or 55a) are lowered carfully in unison, to accommodate the alignment
of the containers 16 automatically, so that each spud 55 engages first the
projections 25, 26 of the more buoyant barge or lighter 16 and pushes it down,
and then engages the projections 25, 26 of the less buoyant barge or lighter
16, eventually pushing the sockets 27, 29 of both of them against the bottom
projections 44, so that the containers 16 are locked securely in place and
cannot thereafter move during the voyage. (Similar action occurs with the
spuds 55a, with the differences clearly apparent.) As a safety precaution
a lock pin 60 is inserted through an opening 61 in the housing 51 to engage
the upper end 62 of the spud 55 to prevent upward movement thereof. While
this is being done, or after it has been done, the buoyancy tanks 18 are ad-
justed to give the proper waterline, trim, and list. Since there will always
be water inside the hold 32 and since some of the containers 16 will be so
heavy that they will rest directly on the hull girders 14, the total load of
the vessel 10 is lightened by the lighter containers 16, which may be com-
pletely empty or may be considerably lighter and thereby, in effect, impart
a negative load to the hull 11, counteracting to some extent the positive
load of the filled and heavy barges or lighters 16. This transfer of
buoyancy enables a sharing which is very effective.
Once all of the containers 16 are in place, or even at the same
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time, additional cargo 84 not of the floatable type may be taken on and loaded
on deck as shown.
When the ship 10 has reached its port of destination and anchors in
protected watersJ the pins 60 are pulled out, the lock spuds 55 are all re-
leased, and the vessel 10 is ballasted so that all the containers 16 float
freely. Unloading operations may proceed as shown in Figure 3, by opening
the bow gate 22 and with the winch 35 then being attached over the forward
pulley 38 and then to the aftermost container 16, and then the containers are
pulled out through the bow in order, still locked together. Then the unloaded
series of barges or lighters 16 may be push or pull-towed by a suitable tug-
boat 31 to cargo distribution points. Alternatively, unloading operations
may proceed as shown in Figures 22 and 24, with the winch 35 attached to the
after pulley 37 and then to the forwardmost container 16, pulling the con-
tainers out through the stern, all still locked together. With the vessel
lob having both a bow gate 63 and a stern gate 81, the loading and unloading
proceed in the same direction, the first barge or container 16 to go in being
the first to come out, a procedure especially useful when some containers 16
are to be unloaded at a first port of call and other containers picked up
there, and other containers are delivered to other ports of call, whether
2Q still others are acquired at each port or not. For this purpose the contain-
ers are initially loaded in the order in which they are to be unloaded later.
Thus at each port of call the devices 50 are released, as are pertinent cables
30, a few containers 16 may be moved out through the stern gate 81 for delivery
to that port; then the remaining containers 16 are moved by the winch 38 clos-
er to the stern, and finally containers 16 from that port are moved into the
hold through the bow gate 63 and all containers again locked in place. Other
practices may be followed in partial discharge and loading operations.
A typical vessel of this structure would have a displacement of
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about 10,000 tons, would be about 360 feet long, would have a beam of about
80 feet, and a draft of about 15 feet. The lock spuds would typically be
about five feet in diameter or five feet square and 14 feet high. About eight
barges or lighters would be accommodated, these typically being about 60 feet
long by 30 feet wide by 14 feet high.
As Figure 8 shows, the tons-per-inch immersion increases rapidly for
the first foot of draft and then, bears a linear relationship up to a draft
of about ten feet, the level of the upper surface 15 of the transverse girders
14. At that level, the tons-per-inch immersion can vary widely, reducing to
a low value with the ship empty or increasing rapidly if loaded with barges
or lighters. With the ship empty at the draft of ten feet, the tons-per-inch
immersion rises linearly to a draft of fifteen feet where it is at a value
less than that at ten feet. With the vessel 10 loaded at the draft of ten
feet, the tons-per-inch immersion rises linearly to its maximum value as the
ship lowers in the water to its preferred operating draft of about fifteen
and one-half feet. The curve shown in Figure 8 illustrates the transfer of
buoyancy concept of this invention in which the excess buoyancy of lighter
floating cargoes, such barges and lighters, is transferred to the vessel
through locking spuds to assist in support of vessel and other heavier barges.
To those skilled in the art to which this invention relates, many
changes in construction and widely differing embodiments and applications of
the invention will suggest themselves without departing from the spirit and
scope of the invention. The disclosures and the description herein are purely
illustrative and are not intended to be in any sense limiting.
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