Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a tow boat
havin~ winch means for towing objects and handling
anchors and the like, said winch means being arranged
on or adjacent a main deck extending along a part of
the afterbody and comprising a first winch having a
cable leaving the winch and extendable in spaced parallel
relationship to the main deck for ~owing objects and
the like, and a second winch having a cable leaving
the winch and extendable to a stern roller serving
as a cable guide for handling anchors and the like.
A similar tow boat is known from British
patent 1,462,797. For many years it has been known
to use tow boats or maritime transport of vessels
whether or not having their own propulsion mechanism.
Initially, these were practically always cargo ships
or similar vessels. At present, however, there is an
increasing need for towing floating installations,
such as off-shore drilling rigs, working platforms
and the like. These ins~allations are to be anchored
at the destination. For this purpose, tow boats of
the known type are used for handling the anchors; this
is also done for weighing ~he anchors, for removing
or relocating the installa~ion. The anchors weighed
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cannot be installed on the poop deck of the known type
of tow boa~ but, before a start can be made with the
~ransport of the installation, should be transferred
to a different part of the tow boat or be taken on
board the installation to prevent said anchors from
reducing the manoeuvrability of the tow boat during
the towing of the installation.
A further drawback of this known tow boat
is the considerable distance between the point of attach-
ment of the towing cable and the point or axis of rotationof the ship, so that the manoeuvrability of the tow
boat is adversely affected. It has been tried to improve
this manoeuvrability by using a driving mechanism in
the fore-part. However, the effectiveness of this feature,
to say the least, is doubtful in the case of any swell.
A fur~her development in the past few years
has been that many of such installations are towed
in an at least partially sunk condition, which implies
that the place of attachment of the towing cable is
often at a given distance below the water level, so
that the towing cable is prevented by the stern of
the tow boat from extending in a substantially straight
line from the winch to said place of attachment. This
is detrimental to the manoeuvrabili~y of the tow boa~
due to the large distance between the point of application
of the towing cable on the tow boat and its rota~ion
point. The further displacement of the winch towards
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the stern of the tow boat does not remove the drawback
regarding the manoeuvrability of the tow boat, while
moreover the winch can no longer be employed for hauling
objects, e.g. anchors, on deck. In order to preserve
the optimum manoeuvrability of the tow boat by not
allowing the towing cable to be supported on the stern
of the tow boat, said cable may be provided outboard
with a plurality of floating bodies keeping the towing
cable, prior to its submersion, at such a level that
the afterbody of the tow boat can swivel freely underneath
the cable. The installation of floating bodies, however,
and certainly in ~he case of rough weather, is elaborate
and time-consuming, while the floating bodies, moreover,
in inoperative condition, occupy space that could otherwise
be used for transpor~ing cargo. This drawback is ~he
more significant when it is borne in mind that tow
boats are also used as provisioning boats for these
floating installation.
It is an object of the present invention
to provide an optimally manoeuvrable tow boat which,
moreover, enables optimum anchor and cargo handling.
It is another object of the present invention
to maintain an optimum manoeuvrability oE the ~ow boat,
as well as such a cable guide that the time consuming
ins~allation of bulky floats can be dispensed with.
According to the present invention optimum
manoeuvrability and optimum anchor and cargo handling
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are achieved with a tow boat of the above described
type when the main deck extends along the major part
of the afterbody and the second winch includes a cable
leaving the underside of a drum constituting part of
the winch, said first winch having a higher position
than the second winch, a 'tweendeck being provided
at a level below that at which the cable leaves a drum
forming part of the first winch and above the level
at which the cable leaves the drum of the second winch,
said level lying above the main deck.
The~e features allow to minimize the distance
between the point of application of the towing cable
on the tow boat and its point or axis of rotation,
while during both towing and the handling of anchors,
there always renains a deck free for storing and trans-
porting goods, while the total deck area is substantially
increased when the boat is neither towing nor handling
anchors.
When anchors are handled, cargo may be present
on the Itweendeck without entailing impediments or
problems. A further advantage is that the main deck
is covered, at least partly, so that crew members being
at that location for handling the anchors are sheltered.
This is especially important when it is borne in mind
that a tow boat, during the execution of operations,
is preferably positioned in such a manner that in the
case of engine failure or the like it drifts away from
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the installation, which means that the tow boat with
its low afterbody lies in the wind direction with all
adverse effec~s resulting therefrom for the crew members
working at that location.
When towing takes place, at least the part
of the main deck covered by the 'tweendeck is available
for cargo. For instance, the anchors of the floating
installation can be stored at that place during towing.
This means a substantial gain of time when floating
installations are relocated, in particular in rough
weather,since the transfer of the anchors to, and the
take-over from, the floating installation can be dispensed
with.
When no towing or anchor handling takes place,
both the 'tweendeck and the main deck are entirely
available for stowing cargo, so that considerably more
supplies can be transpor~ed.
In order to maintain adequate manoeuvrability
in the case of a relatively low attachment of the cable
2~ to the objec~ in tow, in a further preferred embodiment
of the pr~sent invention, tow rails are provided on
the 'tweendeck. Said two rails can guide the towing
cable during its rec;procating slewing movement relative-
ly to the deck.
For promoting efficient operation and greater
flexibility in the alternation between towing and anchor
handling, in a further preerred embodiment of the
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present invention means are provided for displacing
carg~ from the main deck to the 'tweendeck and vice
versa. Any cargo present can be transferred in a quick
and simple manner from one deck to another by said
means, e.g. one or a plurality of hatches and/or a
simple hoisting apparatus, e.g. during changeover from
towing to anchor handling. For instance, cargo present
on the main deck during towing can be positioned on
the 'tweendeck, so that this becomes entirely free
for optimum and effective anchor handling. After taking
the anchors on board, the cargo can again be lowered
onto the main deck and be secured between or adjacent
the anchors, after which the 'tweendeck is again free
for providing an optimum manoeuvrability during the
towing.
According to a further preferred embodiment
of the present invention there is arranged underneath
and/or behind the winch means a substantially vertical
shaft for passing ~he cable underneath the tow boat,
said shaft being provided at least at a lower end with
a cable guiding and retaining member which, as viewed
in the towing direction, is positioned adjacent the
rear part of ~he lower end. Due to these features,
in fact, the place of attachment oE the towing cable
is displaced to the underside of the towing boat, i.e.
to the c~ble guiding and retaining member situated
at the lower end of the vertical shank, so that this
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point of application can con~;nue to be situated in
proximity to the point of rotation of the towing boat.
It has thus been become superfluous to elaborately
create a bend in the towing cable between the ~ow boat
and the objects to be transported by means of additional,
bulky, loose aids.
An additional advantage of the features proposed
in accordance with the present invention is that at
least one deck of the ~ow boat remains substantially
free and thus becomes available for storing objects,
transporting cargo and/or carrying out operations.
When the vertical shaft is not situated under
the winch means, according to a still further preferred
embodiment of the present invention, for optimum cable
guidance and take-up of towing force that the shaft
is provided at the forward part as viewed in the towing
direction of its upper end with a cable guiding member.
The vertical shaft adjacent the winch means
offers the addi~ional advantage that very large and/or
heavy objects can be towed by means of attachment of
a first cable at a submerged level and a second cable,
e.g. at the level of or above the water line. Moreover,
and advantageously, it thus becomes possible to raise
and/or transport submerged objects in a controlled
manner by engaging the object by means of a cable extending
vertically downwards through the shaft and by means
of one or more cables extending downwards from the
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stern roller. This enables an object to be hoisted
up wh~n the winches are set ;nto operation, after which
said object, suspended from the cable, can be transported
or be inspec~ed or repaired by divers.
Some embodi~ents of the tow boat according
to the present invention will now be described, by
way of example, with reference to the accompanying
drawings, in which
Fig. 1 shows a first embodiment of the tow
boat during towing with cargo on the main deck;
Fig. 2 shows the tow boat according to Fig.
1 during the handling of an anchor with cargo on ~he
'tweendeck;
Fig. 3 shows a second embodiment of a tow
boat during towing with a low point of a~tachment of
the towing cable;
Fig. 4 shows the tow boat according ~o Fig.
3 during the towing of a very large and/or heavy object
with a high and a low point of attachment of the towing
cable; and
Fig. 5 shows the tow boat according to Fig.
3 during the hoisting up or transport of a submerged
object.
The figures very diagrammatically show a
tow boat 1 having a fore-part 2 with a bridge 3 and
an afterbody 4 w;th a main deck 5. The winch means
are arranged approximately amidship, winch 6 with cable
7 serving as a towing winch and winch 8 with cable
9 as an anchor handling winch. Winches 6 and 8 are
arranged and mounted in such a manner that the cable
7 leaves the winch 6 at the top and the cable ~ leaves
the winch 8 at the underside, winches 6 and 8 being
vertically of~set relatively to one another, so that
there is created such a difference in height between
the two cable levels that a 'tweendeck 10 can be mounted
underneath the level of cable 7 when extending horizontal-
ly, thereby obtaining a covered working and/or storage
space for cargo 11 on the main deck 5.
For ~he purpose of a proper guidance of the
anchor handling cable 9, the rear of the t OT`~ boat 1
comprises a stern roller 12, while for ~he purpose
Of a proper guidance of ~he towing cable 7, i.e. in
the case of a rela~ively low attachment to an object
being towed, not shown, there are arranged on the 'tween-
deck 10 tow rails 13, one being shown diagrammatically
in the drawings. Moreover, the 'tweendeck 10 may include
one or a plurality of hat.ches and/or a simple hoisting
apparatus may be provided for displacing cargo in a
quick and simple manner from the main deck to the 'tween-
deck and vice versa.
As shown in Fig. 1, the ~ow boat 1 is adapted
to transport cargo 11 during towing, without said cargo
having an adverse efEect on the manoeuvrability of
the tow boat, i.e. the towing cable 7 leaving the winch
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6, arranged approximately at the point of rotation
of the tow boat 1, can unimpededly perform a reciprocating
swivelling movement over the 'tweendeck 10. Moreover,
~he cargo 11 is present in a covered space.
Fig. 2 sho~s that the main deck 5, in sp;te
of the presence of cargo 11 then positioned on the
'tweendeck 10, is entirely available for handling anchors.
In this arrangement the main deck 5 is covered at least
partly, so that crew members presen~ at that location
are considerably less exposed to weather conditions,
which is par~icularly advantageous in the case of rough
weather, the more so ;f it is considered ~hat the tow
boa~ 1 is positioned preferably leeward of the floating
installation, with the afterbody in the wind, in order
that, in the case of engine failure or the like, the
tow boat drits away from the installation. After the
anchors have been taken on board, the cargo 11 may
again be relocated to the main deck 5 and be secured
at that location adjacent to or between the anchors
taken on board.
When ne;ther the towing cable 7 nor the anchor
handling cable 9 are being used, both the main deck
5 and the 'tweendeck 10 are entirely available for
transpor~ing cargo, which improves the provisioning
function of the tow boat, considerably.
The ~ow boat shown in figs. 3-5, as compared
to that shown in Figs. 1 and 2, is additionally provided
with a vertical ~haft 14 arranged - as view in the
towing direction - at a short distance behind the winches
6 and 8, throu~h which a cable can be passed from the
main deck 5 to underneath tow boat 1. For the purpose
of proper cable guidance, there are arranged at and
in the shank 14 cable guiding mPans, of which the figures
show a roller 15 at the top of shaft 14 and a roller
16 at the bottom of shaft 14, said roller 16 being
designed so that athwar~ship forces exerted on the
cable can be taken up.
Fig. 3 shows the situation during the towing
of an installation, with the towing cable 7 being connected
to the installation at a low level under water. Towing
cable 7 then extends from winch 6 to roller 15, where
cable 7 is bent to a position extend;ng through the
vertical shaft 14 to roller 16, where cable 7 leaves
the underside of tow boat 1 and is bent a second time.
Roller 16 accordingly functions as a point of application
of cable 7 on ~ow boat 1, i.e. tow boa~ 1 can roLate
29 about said point of application relatively to cable
7. It is therefore recommendable to situate roller
16 as close as possible to the centre of rotation of
tow boat 1.
As shown in Fig. 3, in this towing method
both main deck 5 and 'tweendeck lO are available for
the transport of cargo, the storage of objects, e.g.
anchors and/or the execution of operations.
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When very heavy and/or very large objects
have to be towed, the procedure shown in Fig. 4 can
be followed. In addition to a towing cable 7 conventional-
ly passed from winch 6, a cable 9 can be passed over
roller 15 through shank 14 and over roller 16, and
attached to the object to be towed at a low, underwater
level. In this method of towing the main deck 5 remains
available for e.g. the storage of anchors with which
the installation being towed is anchored at a place
of use.
Fig. 5 shows a further possible application
to be realized with the features aecording to the present
invention. By passing cable 7 over stern roller 12
and cable 9 over roller lS, horizontally spaced apart
therefrom, it is possible to hoist up an article 17
from e.g. the bottom under water in a controlled manner.
The article 17 thus lifted is easily accessible to
divers for inspection, maintenance or repair operations
and ~he like or can be transpor~ed in a position suspended
from cables 7 and 9.
It is self-evident that many modifications
and variants are possible without departing from the
scope of the present invention. For instance, 'tweendeck
10 may ex~end over a larger or smaller length than
~5 shown in the drawings. Also, at least a part of itweendeck
lO may not extend parallel to main deck 5, but e.g.
slope towards it, which part may ~hen be arranged e.g.
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for swivelling movement and/or be adap~ed for hoisting
objects, e.g~ anchor~, from the water surface direct
onto 'tweendeck 10~ Although the above descrip~ion
refers to one winch 6 with cable 7 and one winch 8
with cable 9, these may also be a plurality of winches,
e.g. two winches 8~ each having a cable 9. The shaft
14 may be adapted to pass more than one cable under
guidance and/or a plurality of shafts 14 may be provided.
Furthermore, the location of æhaft 14 as shown, longitu-
dinally of the boat, should be regarded merely as anexample, too; shaft 14 could alternatively be positioned
right under winches 6 and 8.
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