CA1083491A

CA1083491A - Device for transmission of electric energy from a stationary installation to a movable vehicle

Info

Publication number: CA1083491A
Application number: CA225,995A
Authority: CA
Inventors: Rolf B. Rasmussen
Original assignee: H Hastrup & Co AS
Current assignee: H Hastrup & Co AS
Priority date: 1974-04-30
Filing date: 1975-04-29
Publication date: 1980-08-12
Also published as: AU498385B2; IT1037691B; SE7504920L; DK186475A; NL7505094A; DD117571A5; FR2269432A1; FI60093C; FI751260A; FR2269432B1; DK142495C; DE2517836A1; DK142495B; DE2517836B2; SE409445B; CH586471A5; AU8059675A; DE2517836C3; BR7502620A; GB1497684A

Abstract

ABSTRACT OF THE DISCLOSURE
A device for transmission of electric energy by means of cable from a stationary installation to a movable vehicle is disclosed in which there is provided a drum unit for winding the cable on and off the drum unit, and in which the axis of rotation of the drum unit is vertical and the drum unit cooperates means for effecting the rotational movements of the drum unit so as to take up slack in the cable as the vehicle moves.

Description

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 _ 3 _ ., .
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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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3gL9~ -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 - 5 - ~
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3L(~83~91 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 - 6 - `
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,' ~L~834~1 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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`, . ~LaB3~9~ ' 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 - 10 - ,, .
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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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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, ' .'' '': " ' :' ''';~. ' ' ''," ,' ,;, ' ,:

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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' . . ' ,., ' ' , ~ ~~34gl 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 ~ 17 -"''~
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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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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 '-- 19 - '' ' '..

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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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A device for transmission of electric energy by means of a flexible cable from a source installation to a movable vehicle, preferably a fork lift truck, said vehicle being provided with a drum unit for winding the cable automatically off and on during driving, said drum unit having a vertical axis of rotation and two drum parts, one mounted above the other, characterized in that the two drum parts have opposite upwinding torque from a common mechanical spring battery of spiral disc type, the outer ends of the springs being connected to one drum part and the inner ends of the springs being connected to the other drum part, whereby said vehicle can be driven in any direction including circles without twisting said cable.

2. A device according to claim 1, wherein one of the two drum parts carries a flexible power supply cable and the other carries a wire for controlling the tensioning of the spring battery when driving said vehicle in circles.

3. A device according to claims 1 and 2, wherein said flexible cable is suspended in one free span from said cable drum to plug and socket means on said source installation.

4. A device according to claim 2, wherein said wire is suspended in one free span from the wire drum on the vehicle to said source installation, suitably to said plug and socket means.

5. A device according to any of the claims 1, 2 or 4, wherein said cable drum unit has a freely rotatable guiding means permitting winding action of said cable and wire at any angular direction.

6. A device according to the claims 1, 2 and 4, wherein said power cable is of the flat type having its flat major section horizontal in the free span and vertical when wound on the drum, the 90 degrees twisting of the cable between said span and the drum being provided by said guiding means.

7. A device according to claims 1, 2 and 4, wherein said cable has its sheath made from polyvinylchloride and said guide means has guiding rollers made from polytetrafluorethylene.

8. A device according to claim 2, wherein said wire is a steel wire and said guiding means for the wire is made from a polyamide.

9. The device of claim 1, wherein said drum means and torque means are movably adjustable in a vertical direction.

10. The device of claim 2, wherein said drum means comprises locking means including locking pin means extending through holes of the periphery of the drum for locking said drum to remove tensioning and drag in said cable means and wire means.

11. The device of claim 1 wherein said source installation comprises free running, rail tracking trolley means incorporated in a rail system with rail means.

12. The device of claim 11, wherein said trolley means is relatively long along said rail means one end of said cable means is connected to one end of said trolley means and one end of said wire means is connected to the other end of said trolley means.

13. The device of claim 11, wherein the power source for said trolley is provided through second flexible cable means from second double drum means each of which is provided with common torque means, said second drum means mounted at one end of said rail means and guide wire means passing around said first and second drum means and caster means at the opposite end of said rail means.

14. The device of claim 11, wherein said power source for said trolley means is provided by current collector means slidably engaging current bar means disposed parallel to said rail means.