Bulk cargo ship hold arrangement

The invention relates to an arrangement in ship holds for bulk cargo, for example coal. The hold bottom has one or more rows of discharge openings and is substantially flat on at least one side of the rows of discharge openings. A plurality of drivers are arranged in succession on the flat bottom and are displaceable by drive motors in a direction transverse to said row so as to feed the cargo to the openings.

The present invention relates to an arrangement in ship holds for bulk 
cargo, for example, coal, one or more bulk cargo discharge conveyors being 
arranged beneath the bottom of the hold, the bottom being provided with a 
row of discharge openings for each conveyor, said row of openings being 
situated above the respective conveyor. 
In so called self-discharging bulk cargo ships in which the bulk cargo is 
emptied down onto conveyor belts situated beneath the holds for further 
transportation to conveyors leading out from the ship, the bottom portion 
of the holds are usually provided with inverted V-shaped ridges extending 
in both the fore-and-aft and thwartships directions so that a plurality of 
V-shaped pockets are formed having outlet openings leading to the 
underlying conveyor belts. The purpose of this design is that the material 
will be able to be emptied completely through the various discharge points 
formed by the outlets merely by means of self-pouring. Each discharge 
point has an adjustable hatch by means of which the outflow to the 
underlying conveyor is regulated. 
One disadvantage of this known construction is that the inverted V-shaped 
ridges must be relatively high in order that self-pouring of the material 
will be achieved during the final phase of unloading as well. Said ridges 
intrude upon the volume of the hold so that the effective cargo volume is 
restricted relative the hold in ships which do not self-discharge. It has 
also been found that 100% self-pouring cannot always be secured despite 
the V-shapted ridges. This is due to the fact that arch formation can 
sometimes arise in the material. Finally, another disadvantage is that 
this kind of a cargo ship is restricted to bulk cargos and cannot be used 
for transportation of general cargo or unit load cargos. 
The purpose of the present invention is to achieve a ship hold arrangement 
of the kind disclosed above, by means of which the abovementioned 
disadvantages can be eliminated so that the hold volume can be increased, 
the risk for remaining arch formations is eliminated and the ship can be 
used for general cargo and unit load cargos. 
This is achieved according to the invention by means of the hold bottom 
being substantially flat on at least one side of each row of discharge 
openings, in that a plurality of drivers are arranged in succession on the 
flat hold bottom along each row of discharge openings and in that the 
drivers are connected to a drive unit comprising resilient pulling means 
connected to the drivers, said pulling means extending in a direction 
transverse to the rows of discharge openings over at least a substantial 
portion of the hold bottom and being arranged to achieve controlled 
displacement of the drivers by means of pulling so that the drivers move 
in a direction transverse to the rows of discharge openings so as to feed 
the cargo to the openings. 
A flat hold bottom designed in this manner can be placed deep down in the 
ship far below the level of the abovementioned ridges' upper edge so that 
maximum cargo space is obtained. Furthermore, the possibility of 
alternatively loading general cargo and unit load cargos is created by 
means of the flat bottom. Total emptying of the hold is secured by means 
of the drivers which move in the thwartships direction, said drivers being 
pulled along the hold bottom through the material when it ceases to 
self-pour and tends to hang. 
It has been found that feed capacity is increased and function is improved 
if the hold bottom is arched in the direction of movement of the drivers. 
It has also been found that functional security is further increased if the 
drivers have such inclined drive surfaces that, during the feeding 
movement, the cargo loads the drivers with a force having a component 
directed against the hold bottom. Preferably, the drivers can have a 
trapezoidal cross-section. 
In a preferred embodiment of the arrangement according to the invention, 
said arrangement having a drive unit in the form of a chain for each 
driver, means for prestressing the chain are arranged. This contributes 
considerably to improving the function.

A hold in a coal freighter having an arrangement according to the present 
invention is shown schematically in FIGS. 1 and 2. The hold has a flat 
bottom 1 between two rows of discharge pockets 2 having outlet openings 3 
and hatches 4, said rows extending in the fore-and-aft direction at the 
outer edges of the hold. A conveyor belt 5 runs beneath each row of 
discharge pockets 2, said belt extending in a conventional manner beneath 
all of the holds of the ship and upon which material released through the 
openings 3 down onto the conveyor is fed to a conveyor (not shown here) 
leading out from the ship. 
A plurality of rod-shaped drivers 6 rest upon the flat hold bottom 1. Each 
of the drivers 6 is coupled to a respective chain 7 (c.f. FIG. 1). The 
chain 7 extends across the hold bottom 1 to guide wheels 8 situated 
outside of each longitudinal side, further via said guide wheels 8 under 
the hold bottom to guide wheels 9 and a drive wheel 10 on a drive motor 11 
which can be a hydraulic motor or an electric motor having a gear. By 
means of the guide wheels 9, the angle of contact of the chain on the 
drive wheel 10 will be approx. 180.degree.. Thus, with the help of an 
accompanying chain 7, each driver 6 can be driven individually across the 
flat bottom between the rows of discharge pockets 2. As is shown in FIG. 
2, the drivers 6 are arranged with relatively slight mutual distance in 
the fore-and-aft direction. Thus, when all of the drivers are driven, just 
about the entire bottom surface between the rows of discharge pockets 2 
can be scraped. 
Unloading is carried out in such a manner that the required number of 
hatches (see FIG. 2) are first opened in a conventional manner so that the 
desired feeding capacity is obtained by means of self-pouring. Further 
hatches are opened thereafter until all of the hatches 4 are open. When 
self-pouring ceases, the required number of drivers 6 are activated. They 
are drawn a number of times across the hold bottom 1 between the rows of 
discharge pockets 2 until all the material within their operating area has 
been fed out. Further drivers 6 are activated thereafter and unloading 
continues until the entire ship has been emptied. The different drivers 
can be moved, arbitrarily as required, entire "strokes" between the 
conveyors and/or shorter "strokes" to one of the conveyors. 
FIG. 3 illustrates in more detail an embodiment of a driver 6. It consists 
of a beam having a rectangular cross-section, the broader side of which 
rests upon the hold bottom 1. Angularly bent stays 12 are welded onto the 
opposite short sides with the help of plates 13. The ends of the drive 
chain 7 are intended to be connected to said stays 12. By arranging the 
stays 12 in this manner, it is possible to drive each driver 6 in the 
transverse direction by means of a single chain without any risk of the 
driver being misadjusted. The driver 6 becomes "self-adjusting". 
As all of the drivers 6 can be driven individually by their own drive 
motors 11, for example, hydraulic motors, several of which can have a 
common pump, one obtains a very flexible system which allows for effective 
unloading while maintaining correct trimming of the ship during the entire 
unloading process. Should a single driver "fall out", this has no effect 
on the other drivers and, thus, is of minor importance. The number of 
drivers and their size depends on the size of the ship. An embodiment of 
the invention in a coal freighter of 120,000 tons, for example, has 50 
drivers having a length of three meters, a width of 200 mm and a height of 
100 mm. The small height is to be essentially noticed as it provides an 
effective discharge without requiring unreasonably heavy machinery. 
By means of the invention, the volume of the ship is put to optimum use as 
cargo volume. The distance between the ship's so called tank top 14 and 
the bottom side 15 of the hold bottom 1 (denoted h in FIG. 1) need only 
correspond to normal standing height. 
In order that the bottom area of the entire hold, i.e. the area of the 
discharge pockets 2 as well, shall be able to be used for general cargo, 
the side walls 16 of the hold can be provided with hatches as indicated by 
17, which can be swung down over the discharge pockets 2 so as to form an 
extension of the flat hold bottom 1 out to the sides 16. 
In FIG. 4 a plurality of rod-shaped drivers 6 having a trapezoidal 
cross-section rest upon an arched hold bottom 1. The guide wheels 9 are 
journalled in a horizontally movable fashion and are each connected to a 
respective hydraulic cylinder 12 by means of which the tension of the 
chain can be controlled. Thus, with the help of an accompanying chain 7, 
each driver 6 can be driven individually across the bottom between the 
rows of discharge pockets 2 in the same manner as previously described.