Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
33~91
The present invention relates to a device for trans-
mission of electric energy by means of a cable from a
stationary installation to a movable vehicle, preferably
a transporting means, said vehicle being provided with a
drum unit for winding the cable off and on said drum unit.
The invention is in particular applicable for e.g.
transmission of electric energy from a 220 Volts, 380 Volts
or 440 Volts three-phase A.C. voltage installation to a
fork lift truck driven by an A.C. powered electric motor
and a step-free,controlable, hydrostatic device operating
in the cargo hold of ships. The invention is, however,
not limited to this field of use, and may also be used
in warehouses, factory halls etc., and not necessarily
in connection only with electro-hydraulic fork lift trucks.
The following description discloses for reason of simplicity
and as example only, the device used in connection with A.C.
powered, electro-hydraulic trucks working in cargo holds
of a ship, and the invention is of course not limited to
use on board a ship.
A.C. powered operation of fork lift trucks is not
realizable without a safe, electro-mechanical arrangment
capable of transferring the required A.C. energy from the
stationary low-voltage installation to the truck. This
arrangement should enforce the least possible restrictions
on the driving of the truck, preferably the truck should be
capable of driving in the same free manner as a radio car
in an amusement park. However, since trucks most frequently
operate in surroundings being inflammable, the transfer of
electric energy by a flexible cable arrangement is realistic.
From the German periodical "fordern und heben", No.
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~OB349~
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15, November 1972, 22. year, pp. 859-861, "Netzstrom-
gespeiste Stapler fur dauernden Einsatz", Dipl.-ing.
H. W. Stuhr, it is known a fork lift truck for A.C. powered
operation.
The system makes use of a flexible rubber type
cable in combination with a cable drum and a rail system
attached to the ceiling, the cable drum being mounted on
the truck itself.
The system consists substantially of a rail in-
stallation fixed to the ceiling, a flat cable attached to
a number of cable rail carriages, and a drum installation ~
connecting the trolley with the drum on the truck. ~-
The drum has its axis of rotation horizontally
disposed.
The rail installation with cable carriages is a -
somewhat strengthened model of the corresponding in-
stallations used commonly for operation of cranes. The
driving rail is a cold worked channel steel having a
specially shaped profile being adapted to the cable
carriages and the associated ball bearing rollers.
The cable drum is of a conventional type having
an internal or a separate spring-action motor. It may
also be operated hydraulically from the hydraulic system
of the truck.
In order to avoid to the extent possible a
damaging twisting of the cable at the outlet of the drum,
the complete drum unit is mounted on a short vertical
shaft on the underlying mounting plate, said drum being
pivotable approximately 300 in the horizontal plane
about said shaft. The cable is let out from the drum
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through an arrangement of guide wheels mounted on a carrying
arm, said arm being inclined relative to the horizontal.
The tensioning of the cable will cause the drum unit to
turn during the driving operation of the truck in such a
way that the carrying arm points substantially towards the
trolley of the rail system.
In constructing the said known system, it has been
attempted to make use of existing standard elements, in-
corporating the advantages associated therewith both for
the designer and the user.
Partly because the total number of cable rail
carriages require a relatively large parking space when
they all are abutting, the prior art system can only be
used for spaces having an overall length not exceeding
approximately 40 meters.
The prior art system is only suitable for operations
where the truck is to follow a predetermined and routine-
like manoeuvring cyc~us which is repeated for each operation
cycle, the reason being that independent driving or driving
at random is likely to cause a damaging twisting on the round
cable between the rail system and the truck.
The prior art system requires more than sufficient
space between the top edge portion of the safety housing
of the truck and the ceiling due to the drum-structure
requiring a substantial space.
It is an object of the present invention to provide ;
a device enabling the truck driver to drive the truck freely
within the range of the overall system without having to
use a predetermined operation cycle to avoid any twist on
the flexible transmission cable.
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A further object of the present invention is to
provide a device requiring a minimum of free height between
the top of the safety or protective housing on the truck
and the ceiling or ceiling girder, but may also be adapted
to any ceiling level.
Still a further object of the present invention is
to provide a device which can be used in smaller cargo
holds without the 1nstallation of stationary rails or
electrical bar devices, but may as well be adapted to
rooms having a maximum length by cooperation with a longi-
tudinally installed rail system provided with current
transfer through a suitable flexible cable or an electrical
current bar system having sliding contacts.
These and further objects of the invention are
solved according to the characterizing features of the
invention which do apper from the attached claims, and
from the description hereinafter with reference to the
drawings, in which a total of nine embodiments according
to the invention are illustrated as examples only.
The nine embodiments described and illustrated are
all based on the use of a cable drum structure having a
vertical axis and being mounted on the truck. In the three
first embodiments shown, the said cable drum structure inter-
acts with spring action means, in the next five embodiments
the cable drum structure is interacting with hydraulically
operated means, and in the last example the cable drum
structure is once more acted upon by spring action means.
Figs. 1 - 3 illustrate the first embodiment accor-
ding to the invention.
Figs. 4 - 6 illustrate the second embodiment
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according to the invention.
Figs. 7 - 9 illustrate the third embodiment
according to the invention.
Figs. 10 - 12 illustrate the fourth embodiment
according to the invention.
Figs. 13 - 15 illustrate the fifth embodiment
according to the invention.
Figs. 16 - 18 illustrate the sixth embodiment
according to the invention.
Figs. 19 - 21 illustrate the seventh embodiment
according to the invention.
Figs. 22 - 24 illustrate the eighth embodiment
according to the invention.
Figs. 25 - 27 illustrate the ninth embodiment
according to the invention.
Figs. 28 - 30 illustrate a guide means for cable
and wire, and a safety means for the device according to
the invention.
The device as disclosed and shown in the embodiments
~ .
No.l and 4 below,are in particular suitable for a very special
purpose, i.e. transfer of electric A.C.energy from a stationary
installation to an A.C. powered electro-hydraulic fork lift
truck intended for universal use in cargo holds of different ;
ships, without a prior installation on board of special
equipment like rails, cable drum or sofisticated electrical ~ ~
installations. The truck may be located at a fixed harbour, ~ -
.:. - , . . .
and is to operate on board of various ships which are calling `
the harbour. The truck is lowered into the cargo hold by means
of a harbour crane, and the device on the truck is connected
to the electrical installation on board the ship or that of
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the harbour, the latter by means of a conventional extension
cable.
The device according to the embodiments 1 and 4 imply
that the equipment,which is to be attached to the bulk-head
after the truck has been lowered down through the cargo hatch-
way,only includes a tension reliever and said plug-in means. ~
This equipment is easily shifted from one location to another ;
in the cargo hold as required.
The device according to the invention is easily -
adaptable to various ceiling levels in the cargo holds by
means of vertical shifting of the drum unit. In the lower
position of the drum, only a short distance is required
between the top of the truck and the ceiling.
Devices according to the invention having all the
described features, are not previously known. Neither has
a fork lift truck been used as described with reference to
the embodiment No. 1 and 4.
It is, however, possible that a cable system can
be made of conventional, well known components, e.g. by
mounting av spring operated, conventional cable drum
with a horizontal main axis on top of the protective
housing of the truck, said drum being rotatable in the
horizontal plane and having an extra slip-ring set mounted
in connection with the associat`ed bearing having a vertical
axis. Such a system could yet only be used having rela~
tively high ceilings because of the required extra space
which the cable drum would require between the top part
of the truck and the ceiling. Such a system would also be
both complicated and expensive.
Current transfer through electrical bar or rail
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system provided with sliding contacts is generally used
by railgoing vehicles like railway trains, traverse cranes
or the like ,and is of course not novel. The particular
combination of an electrical bar system having its own
railgoing current collector trolley and a vertical drum
unit as described in embodiments No. 3 and 6, is not
previously known. The said combination provides for
virtually unlimited action distance, large action width, a
minimum required space above the truck and finally the
very important feature comprising free driving possibility
through the complete action area without any risk for the
flexible cable being twisted.
The different embodiments will now be described
in detail with reference to their respective drawings.
Embodiment No. 1, figs. 1, 2 and 3.
Fig. 1 illustrates the spring operated, double
drum mounted on the truck and the tension reliever with
the plug-in means attached to the bulk-head.
Fig. 2 illustrates a top view of the embodiment
according to fig. 1.
Fig. 3 is a section through the drum unit according
to flg. 1. ~;
As a flexible cable is preferably used a flat ; ;
cable 1, which is wound on the upper drum 3. One end of
..:
the cable 1 is positioned inside the inner tubular shaft 6
and connected to the slip-rings in the housing ll,and the other
,: . .
end of the cable is connected to terminals in the plug-in
means 13.
One end of the wire is wound onto the lower drum
4, and the other end is connected to the ground terminal
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of the plug-in means 13 together with the ground conductor
of the flexible cable. Thereby, the wire provides an
extra ground connection in addition to the ground conductor
in the flexible cable. This is an important feature with
regard to safety, since the truck itself is insulated from
ground by means of conventional rubber tyres.
The cable and the wire are respectively wound onto
the respective drums in mutually opposite directions.
Inside the freely rotatable spring housing 9
there are mounted two springs of the flat spiral type.
The upper spring 8 is driving the wire drum 4 through the
outer tubular shaft 6, and the lower spring 10 is driving
the cable drum 3 through the inner tubular shaft 7. Both
springs have the housing 9 as their external fixing point
and are mounted with mutually opposite torque directions.
When -the truck is driven away from the tension
reliever 13, the cable and the wire will be unwound from ;
the respective drums 3 and 4, and both springs will be
tensioned. In the opposite situation, i.e. driving the
truck towards the tension reliever, both springs will be
. . .
slacked.
If the truck is driven in an imaginary circle with
the cable drum in the centre, the length of the unwound ;~
cable and wire will be unaltered and therewith also the
spring tensioning.
During this manoeuvring the spring housing 9
will turn relative to the truck, but not relative to
the direction towards the tension reliever. By driving
the truck in larger circles, the situation will be the
same. As a result of this feature, the truck can be ~
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driven in freedom within the range of -the flexible cable
without there being any risk of the flexible cable being
twisted.
The slip-ring housing 11 is fixed by means of
screws to vertical fixing rails 12. The housing contains
a vertical thrust ball bearing supporting the weight of
all rotating parts. By using different holes in the
fixing rails 12, the vertical position of the drum unit
may be adapted to the ceiling level in the cargo hold.
The drum unit is also equipped with guide means
respectively for the cable and the wire, to ensure that
the cable and the wire always will enter properly into
the respective drums. These guide means are shown in
principle on figs. 28 and 29.
As a flexible cable 1 it is preferably used a
flat type cable which is fed through an arrangement of ;
vertical and horizontal rollers 51.
To attain a minimum of mechanical wear on the
sheath of the flexible cable, the rollers of cable guide
are made of PTFE (Polytetrafluorethylene), and the cable
sheath is preferably made of PVC (Polyvinylchloride). This ;
combination of materials yield extremely low mechanical wear ~ -
on the cable sheath and consequently long life for the
flexible cable.
The guide means for the wire 2 is in principle
constructed in the same manner as the guide means for the
cable, said means for the wire comprising horizontal and
vertical rollers 52. In order to have the least possible
mechanical wear on the wire, said rollers are suitably
made of PA (Polyamid). Said rollers for guiding said
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cable and wire are mounted on a common supporting plate
53 being rotatable freely about the centre of the drum unit ;
and guided by casters 54.
Prior to moving the plug-in means and the tension
reliever from one location to the next, it is a requirement
that the tensioning or drag in the cable and wire is removed.
This action may easily be executed as shown in fig. 28 by
introducing a locking pin 55 through corresponding holes
at the peripheries of the respective drum parts. When the
locking pin is not in use, it should be stored in a pocket
56 situated e.g. on the instrument panel of said truck, see
fig. 30. The pocket is provided with electrical switch
means 57 serving as an interlock to prevent the electric
motor on the truck from starting in the event that the
locking pin is not in place in the pocket.
Making the cable sheath from PVC includes the
advantage that the weight of the cable per unit length or
meter becomes relatively low, which in turn makes it
possible to maintain the drag or tensioning in the cable
at a reasonable level. This feature is also advantageous
with respect to the life of the cable, the manoeuvring
properties of the truck and above all the dimensioning of
the driving and operation means. The use of a flat cable
in the cable system offers possibilities for conveniently
extending the use to include also transmission of signals
for manoeuvring circuits andshielded telephone circuits
parallel to the power lines in the cable.
The drum unit provides the truck with an action ~
area having the form of a semi-circle with a radius limi- ;
ted by the length of the cable and the capasity of the
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334~
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spring battery. If the truck is required to drive beyond
this limited area, the tension reliever with the associated
plug-in means will have to be moved from one attachment
location to the next. This is a simple operation which
requires only a few minutes,incorporating easy removal of
the electric plug from said attachment location, i.e. an
electric socket, and moving said plug to another electric
socket where said plug may easily be plugged in.
The cable drum can be equipped with a limit switch
which gives the driver of the truck a signal when the truck
has reached the limit of the action area, the maximum ~-
driving distance being approximately 40 meters.
Embodiment No. 2
In large cargo holds, the required driving dis-
tance can be of such extent that it would be necessary ;
to move the attachment location described ahove for the
embodiment No. 1 for each lifting operation. This would,
,: . ...
of course, be both inconvenient and impractical.
Under such large scale conditions, the drum unit
on the truck may be combined with a similar drum unit 25 -
installed at the ceiling at the end of a rail system,
and being mounted in or near the longitudinal centre line
of the hold.
sy means of such a combined system a cable truck
may be used in holds of extended length and width corre-
sponding to the double length of the flexible cable,
however taking the capasity of the spring battery into
consideration. By making the trolley 21 relatively long,
and attaching the flexible cable to one end of the trolley
and the wire to the other end, this combined system will
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yield the same properties as that of embodiment No. 1,
i.e. that the truck is permitted to be driven in freedom
within the range of the cable system without any risk for
twisting of the flexible cable.
Figs. 4, 5 and 6 illustrate the basic construction
of the device accordiny to embodiment No. 2.
Fig. 4 illustrates the spring operated, double
drum mounted on a truck and a similar drum unit being
stationary mounted at the ceiling at the end of the rail
system.
Fig. 5 is a top view of the embodiment according
to fig. 4.
Fig. 6 is a section through the stationary mounted
drum unit.
The trolley 21 is guided by horizontal and vertical
wheels 22, running in the rails 23. At one end of the
trolley, there is installed a tenstion reliever and
junction unit 24 for the flexible cables from the two drums,
and at the other end the two wires are attached.
The stationary arranged, double drum 25 has
a principle of operation equal to the drum on the truck,
but exhibiting a different mechanical structure. The
spring in the cable drum 26 and the spring in the wire
drum 27 are mechanically linked through the freely bedded
tubular shaft 28. The two springs provide the cable drum
and wire drum with equal torque, but in opposite directions.
The wire 29 runs over the pulley 30 to the trolley;
As a result of this special arrangement, the
trolley will positively follow all longitudinal driving
of the truck, and will as a consequence thereof always
~0~3~
remain approximately symmetrically positioned relative to
the drum unit on the truck, i.e. the angle A approximately
equal to angle B.
When the truck is driven lateraly across the room
and passes below the said rail system, the trolley will,
at the moment of crossing, be in approximately a
symmetrical position above the drum unit on the truck,
and the guide means for the cable and wire will turn to
opposite sides at the drum parts. Thereby, there will be
no interference between the cable and wire, and twisting
,
thereof is avoided. The maximum driving distance will be
approximately 80 meters.
Embodiment No 3
.. __ ~, .
In this embodiment the spring operated, double
drum on the truck is cooperating with a conductor bar
system with current collectors mounted on a railgoing
trolley. The current bars and the associated trolley
rails are fixed to the ceiling, at or close to the
longitudinal centre line of the hold. The cable drum on
the truck is of the same structure as that used in emhodi-
ment No. 1 and 2.
Figs. 7, 8 and 9 illustrate the basic construction
of the embodiment No. 3.
Fig. 7 illustrates the spring operated, double
drum mounted on a truck and a trolley with current
collectors running freely on a rail system having elec- ;
trical bars.
Fig. 8 is a top view of the embodiment according
to fig. 7.
Fig. 9 is a section through the spring operated,
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1~ ~83491
double drum.
Fig. 9 is identical to fig. 3, and is repeated on
this drawing for making the studying of the same easier.
The principle of operation of -this embodiment is
equal to the principle of operation of the embodiment No.
2, with the exception of the stationary arranged cable
drum and the associated flexible cable, the function of
which has been replaced by the electrical bar system.
On the trolley 21 are mounted four current col-
lectors 31 sliding against the conductor bars 32. The
flexible cable from the drum unit on the truck is attached
to the trolley at the attachment location 33, which in-
cludes a tension reliever, and is further connected to
the four collectors, making electrical connection to
the phases R, S, T and ground. The wire is attached to
the trolley at the attachment location 34 and further
connected to the ground collector together with the ground
conductor of the flexible cable.
The embodiment No. 3 may be used in holds of
virtually unlimited length.
Embodiment No. 4
The drum unit installed on the truck in the
embodiments No. 1, 2 and 3 comprises two drum parts, one
for the cable and one for the wire, with a common spring
battery providing both drums with equal torque, but in
opposite directions. The object of this conception is to
avoid that the driving in circles will have influence on
the tensioning of the springs in the spring battery, and to
avoid twisting of the flexible cable. The same property
can be attained without the wire drum if the spriny ;
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; battery is e.g. replaced by a hydraulic mo-tor connected
to the hydraulic system on the truck or by a suitable
electric torque motor providing the cable drum with a
torque through a hydraulic coupling.
Figs. 10, 11 and 12 illustrate the basic con-
struction of the embodiment No. 4.
,
Fig. 10 illustrates, as an example, the hydraulically
operated drum unit mounted on a truck and the cable tension
reliever with the plug-in unit attached to the bulk-head.
Fig. 11 is a top view of the embodiment according
to fig. 10. Fig. 12 is a cross section through the drum
unit according to fig. 10. ~
Suitably, a flat cable may be used as-a flexible ~ ~;
cable also for this embodimentj said cable being wound on
15 the cable drum 3, said cable suitably and preferably in-
cluding a wire. A round cable may, however, be used
instead, but in such a case, the cable drum will have to
be made with a larger space between the lower and upper
disc on the drum, so that the cable can be wound onto the
20 drum in layers. In such a case the drum must also be
equipped with a vertical coiling mechanism, not being
shown on the drawing, to prevent the major part of the
cable to rest against the lower disc only.
One end of the flexible cable is entered down ~
25 through the tubular shaft 6 and connected to the slip- `
rings in the housing 11, and the other end of the cable
is connected to terminals in the plug-in means 13.
The motor 41 provides a torque to the shaft 6
through the gear 42 and thereby winding torque to the
30 cable drum.
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The hydraulic motor will provide almost constant
torque during all driving operations, including both winding
on and winding off the drum. If the truck is driven
along a circular path with the cable drum being at the
centre of an imaginary circle, the length of the cable
wound on the drum will remain unchanged, and the cable
will remain in the same position relative to the tension
reliever 13. By driving in larger circles, the same
situation will apply in that the average amount of cable
on the drum will remain the same. As a result of this
property, the truck may be driven in freedom within the
range of the overall length of the cable without any risk
of causing the flexible cable to be twisted. The maximum
driving lenth will be approximately 60 meters.
Embodiment No. 5
For large scale conditions the hydraulically con-
trolled drum unit of the embodiment No. 4 may be combined
with a spring operated, double drum unit fixed to the ceiling
at the end of a longitudinal rail system at or close to the ;
centre line of the hold. This embodiment possesses a
principle of operation equal to that of embodiment No. 2.
Figs. 13, 14 and 15 illustrate the basic con-
struction of the embodiment No. 5.
Fig. 13 illustrates the hydraulically controlled
drum unit mounted on the truck and the spring operated, ; ;
double drum being stationary attached to the ceiling at the
end of the rail system.
Fig.14 is a top view of the embodiment according
to fig. 13.
Fig. 15 is a cross section through the drum unit
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on the truck, according to fig. 13.
The drum unit on the truck includes a cable drum
3 for the flexible cable 1 and a wire drum 4 for the guide
wire 2. These two drum parts are fixed-to the common shaft
6.
In the same manner as described for embodiment No.
2, the trolley 21 will follow in a positi~e manner all
longitudinal driving of the truck and will always remain
substantially at the same symmetrical position relative to -
the cable drum on the truck, the angle A being approxi-
mately equal to the angle B.
When the truck is driven laterally across the
hold and passes below the rail system, the trolley will,
at the moment of crossing, be in an almost symmetrical
position above the cable drum, and the guide means for
the cable and wire will turn to opposite sides on the drum
parts. Interference or twisting of the cable and wire is
thereby avoided. The maximum drivinglength is approximately
100 meters.
Embodiment No. 6
~ In this embodiment the hydraulically controlled
.
drum on the truck is cooperating with an electric con~
ductor bar system with current collectors installed on -
a railgoing trolley. The electric bars and the associated ;
driving rail are attached to the ceiling, at or close
to the longitudinal centre line of the hold. The cable
drum on the truck is of the same construction as that of
embodiment No. 5. The principle of operation of the
present embodiment is equal to that of embodiment No. 3.
Figs. 16, 17 and 18 illustrate the basic con-
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~ 349~
struction of embodiment No. 6.
Fig. 16 illustrates the hydraulically controlled
drum mounted on a truck and a trolley with current collec-
, tors running in a rail system provided with electrical bars.
Fig. 17 is a top view of the embodiment according
to ~ig. 16.
Fig. 18 is a cross section through the
hydraulically controlled drum, fig. 18 being identical
to fig. 15 and incorporated for completeness.
Four current collectors 31 are mounted on the
trolley 21, said collectors sliding against the conductor
bars 32. The flexible cable from the drum unit is
attached to the trolley at the attachment location 33
including a tension reliever, and further connected to
.
the four current collectors linking the cable with the '~ '
electrical phases R, S, T and ground. The wire is
attached to the trolley at the attachment location 34 '' ~
and further connected to the ground collector together with ;' ~ -
. . .
the ground conductor of the flexible cable. ,~ '
The trolley will, in a positive manner, follow
all longitudinal movements of the truck in the same ,' ~
manner as for embodiment No. 5. The embodiment No. 6 ~ ;' ,
may be used in holds of virtually,unlimited length. ~ ,
.
Figs. 19 - 21, 22 - 24 and 25 - 27 respectively ~ ;
illustrate one of three alternative embodiments of the ,~
device according to embodiment No. 1, figs. 1 - 3.
Embodiment No. 7 ,-.`:'
_. . ._ _ .: : :
In figs. 19, 20 and 21 the cable drum 3 is driven '',, '
by a hydraulic motor 43 by means of a chain drive 44, and
the wire drum 4 is driven by a hydraulic motor 45 by means '-
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of a chain drive 46. This embodiment maintains the use of
the guide wire 2 with its pre-mentioned advantages and the
drum unit is completely hydraulically operated.
Embodiment No. 8
. . . _ . .
The operational system illustrated in figs. 22, 23
and 24 includes a hydraulic motor 47 being mechanically
fixed to the inner hollow shaft 6 and mechanically linked
to the outer hollow shaft 7 by means of gear wheel means
48 between said motor and said outer shaft. The hydraulic ~
oil is fed to and from the motor through pipes 49 via a
rotary hydraulic coupling 50 positioned below the
electrical centre contact. The present embodiment provides
solely hydraulical operation of both the cable drum and
wire drum.
Embodiment No. 9
The operational system of figs. 25, 26 and 27 is
in principle identical to the device as disclosed in
embodlment No. 1 with the exception that the spring battery
is built as a separate unit and placed adjacent the axis
drum unit and connected to the inner hollow shaft 6 and
the outer hollow shaft 7 respectively by means of respective
chain drives. The advantage of the present embodiment is
that servicing on the spring becomes simpler, e.g. re-
placement of the springs of said spring battery.
Due to the structure of the spring battery it is
necessary to have opposite directions of rotation for the ~ -
cable and wire drum respectively. In addition opposite
directions of rotation are important features for making
possible the mutual action which cable and wire have on
the respective guide means, see fig. 29. By having opposite
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direction of rotation for the cable and wire drums it is
also easier to ensure that the drag or tensioning in the
cable and wire respectively is uniform even though '
hydraulical torque mechanisms are used instead o~ said spring
battery, see figs. 19 - 21 and 22 - 2~.
Within the scope of the present invention it is of
course possible to make use of the device according to the
invention and described hereinbefore, e.g. in factory halls,
in harbour installations, in loading areas and warehouses, -
and the invention is not limited to use on board a ship
disclosed above as an example only.
Even though a number of embodiments of the ~ .
device according to the invention have been illustrated . .
and described, it will be obvious to the expert in the art . . .
to modify the said embodiments within the scope and spirit
of the invention, and to dimension the device according to
any set requirement and to provide further means which
offer safe operation and handling of the device. : .
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