A cableway system for forestry is described, the cableway system being arranged for connection to an object in order to carry the object between two points of support. Further, a carriage unit for use in said cableway system, as well as use of the cable- way system to move an object between the two points of support, are described.

Background of the invention

There is a great deal of mature forest which is so located that it is challenging practically to reach and unprofitable to extract the timber, and thereby the forest is left standing. This may, for example, be the case of relatively small forest areas in such locations that they have no access roads. Practical challenges may be that there is steep and/or difficult terrain, for example a scree or a bog. Other factors that may make it unprofitable to extract such a forest may be, for example, that the forest is too small to justify the purchase of expensive equipment necessary for operation, or that it is necessary to construct a forest road for the transport of equipment and timber. The cableway system, the carriage unit and the method according to the invention as described herein, have as a starting point that larger parts of mature forest should be made accessible for profitable extraction.

Prior art

The use of a cableway system with a carriage unit in the form of a trolley for extracting timber in a terrain where access is difficult for machines is known from before.

Patent publication US 2790561 A discloses a cableway with a trolley for extracting timber, the cableway including a motorized winch at one end, which is placed high in the terrain, in the area from which the timber is to be carried. Further, at the other end, the cableway is fixed to a lower point in the terrain, in the area to which the timber is to be carried. The cableway consists of two cables: a main cable and a transport cable operated by the winch. A trolley is placed on the main cable and is arranged with two rope sheaves which can roll on the main cable. The transport cable is attached to the trolley and controls the movement thereof by means of the winch. The trolley is arranged with a locking mechanism which enables the trolley to be locked to the main cable, and concurrently with this locking, the transport cable may be paid out, so that it will also function as a lifting cable for timber that is to be lifted.

In patent publication US 3022747 A a cableway with a trolley for extracting timber is described, in which, like the trolley of US 2790561, the trolley is placed on a main cable and runs along it, and the movement of the trolley is controlled by a pulley system via a transport cable. Here, the trolley is provided with a cable drum with a cable for lifting timber.

Patent publication US 4515281 A discloses a cableway based on the use of a machine / cable crane with towers and winches, the cableway being used to pull the timber towards the machine. Like the above-mentioned cableways and trolleys, this cable- way, too, is provided with a main cable, along which the trolley is carried, and a transport cable hauling the trolley. Further, the trolley is provided with a cable drum with a cable for lifting timber.

There are several types of cable cranes. In addition to the type mentioned above (US4515281), there are cable cranes with running cables and cable cranes with fixed main cables.

The system with running lines involves several lines moving parallel to each other during the winching. A cableway like that will typically use a three-drum trolley, in which one line is used for pulling the trolley out and a further two lines are used for winching the trolley in towards the tower and for rotating the drum in the trolley to pull in or pay out a hoisting line for lifting timber. A challenge with such a system is the fact that there are many parts moving at the same time, and this increases the risk of parts of the cableway catching on trees or other things.

The above-mentioned challenge may at least partially be solved by the system with a fixed main cable, in which a fixed steel rope is extended between two points and a trolley is then run along the steel rope. The trolley may be a motorized - i.e. self- propelled - trolley, or a trolley which is pulled by cables.

Yet another challenge with cableways of a known type is their relatively short reach. Reaches of between 100 metres and 400 metres have been described for prior art as mentioned above.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect the invention relates more specifically to a cableway system for forestry, the cableway system being arranged to be connected to an object to transport the object between two points of support, the cableway system being characterized by comprising :

- a carriage unit to be suspended between the two points of support, the carriage unit being suspended by means of a first connection of variable length and a second connection of variable length, each of the first connection and the second connection including a cable drum with a cable which is, at least partially, wound on the cable drum;

and by:

- the cableway system being configured to move the carriage unit in the direction from one of said points of support towards the other one of said points of support by winding cable off one of the cable drums while cable is simultaneously wound onto the other one of the cable drums.

Common to cableway systems of known types is the fact that they have a drive placed on the ground, either in the form of a winch system or in the form of a cable crane. When a cableway system of a known type is installed in connection with forestry, the main wire, the cable on which the trolley moves, that is, must be extended between at least two points of support, and then further cables or a motor are/is used to move the trolley along the main wire.

The cableway system according to the invention does not have a trolley moving on a main wire; in contrast, the cableway system is provided with a carriage unit which is suspended between two parts of the cableway system, called a first connection and a second connection above. Both these connections include a cable drum with a cable. That is to say, the carriage unit does not move on a running line, but it is attached to these two connections which in turn are each attached to a respective point of support. Some places herein, the points of support will also be termed supporting elements. The points of support may, for example, be the end points of the cableway. By means of winding/reeling and unwinding/unreeling of cable on/from the cable drums, the carriage unit is then moved between the points of support.

Said points of support may be trees, poles, masts, machines or the like, which can bear the forces that will arise in the cableway when timber or other objects is/are being carried. If the points of support are not strong enough in themselves to resist such forces, guying is used in a manner known per se.

The fact that the carriage unit is moved by means of cable drums placed between the points of support, makes the cableway system much easier to mount than today's systems in places that are difficult to access. The cableway system according to the invention works equally well whether the timber is to be carried in flat terrain, upwards in the terrain or downwards in the terrain. The equipment may thereby be carried to the nearest practical place, called the "starting point" in what follows, that is to say a point or place to which there is good access. From there, the end of the first connection of the cableway system may be pulled to a desired point of support at a desired distance from the starting point. This means, in its simplest form, that the end of a cable is pulled through the forest to a suitable tree, which may be used for a point of support, and is attached to this. The other end of the first connection is connected to the carriage unit which in its turn is also connected to an end of the second connection. The second connection is attached to a suitable point of support at the starting point of the cableway system, whether it is to a tree, a mast, the machine that brought the equipment there, or the like. The cableway system between two points of support may be termed, for example, a cableway stretch, and will be referred to as this in what follows.

Thus, the carriage unit of the cableway system according to the invention is arranged to function as a link between two cables, so that the cables and the carriage unit constitute both the main cable and the hauling cable. By the main cable is meant the cable that is holding the load up, and by the hauling cable is meant the cable that moves the load between the points of support, or the cableway end points. The cableway system according to the invention is thus simpler than known cableway systems, as the cableway system consists of few parts and as the carriage unit is movable between the points of support of the cable stretch by reeling and unreeling cable on/from the two cable drums.

The cableway system is described herein in relation to forestry and the extraction of timber. It must be understood, however, that the cableway system may have many more areas of application. The cableway system may, for example, be used as a res- cue line as it is quick to install and can be used in rugged terrain. Further, the cable- way can be used between boats and/or between buildings and in other places where objects or persons are to be carried between two fixed points. The cableway system according to the invention is also easy to use to carry objects across obstacles such as rivers and gorges. When the cableway system is used as a rescue line at sea, it will be advantageous if it is connected to a heave-compensation system, for example in such a way that the cable of at least one of the connections is a cable directly connected to the heave-compensation system.

The cableway system according to the invention is also particularly well suited for carrying objects between two points of support, of which at least one point of support is moving. A situation like that can arise, for example, if objects are to be carried from land and aboard a boat, or if objects are to be carried between two boats. When the point of support is moving, there will be unforeseen and/or uneven pulling on the cables of the cableway system, but because the cableway system according to the invention comprises connections of variable length, wherein the cable drum may pay out more cable if necessary, rupturing the cable and dropping the object being carried is prevented.

The cableway system according to the invention is further well suited as a hoisting device, for example at a construction site, where it may, at least temporarily, replace a mobile crane. The two points of support may be spaced apart and be of such an elevation that the cableway system will have the necessary reach all around the construction site. Where there is a need to hoist objects from a lower level to a higher level, for example from a ground level up to the first floor of a building, the cableway system may be attached to two supporting elements, for example on the roof of the building, and the carriage unit can then be lowered along the building, be attached to the object and lifted back up to the relevant height. The supporting elements may advantageously be placed at the same elevation, but may also be placed at different elevations.

The cableway system may be provided with a driving means for driving the cable drums. The cable drums of the cableway system may be driven in several ways. In its simplest form, the cableway system according to the invention may be driven manually by means of a crank or the like. However, this is impractical and laborious. It is preferred that the cableway system includes a driving means which includes a form of motor, for example a combustion engine, an electromotor (direct-current/DC motor or an alternating-current/AC motor) such as an asynchronous motor with a frequency converter, or a jet engine. The two cable drums of the cableway system may be arranged to rotate at a first cable speed and a second cable speed, respectively; by cable speed being meant the speed at which a given length of cable can be wound on or off a cable drum.

The first cable speed and the second cable speed are affected by various factors such as the rotational speed of the cable drum, the thickness of the cable, the number of cable layers on the cable drum, and similar things. If the two connections are basically identical as far as cable and cable-drum dimensions are concerned, and if the cable drums are driven at the same rotational speed, the first cable speed and the second cable speed will only be equal for a moment when the carriage unit reaches the middle of the cableway stretch. If the two cables are of equal thickness and the cableway stretch is relatively short, so that the cable is wound only one turn around the cable drum, a solution in which the two cable speeds are approximately equal over the entire cableway stretch is conceivable. Otherwise, the rotational speeds of the cable drums will have to be adjusted relative to each other to maintain an even movement of the carriage unit.

The cableway system may be provided with a transmission device which is arranged to keep the first cable speed equal to the second cable speed in order to enable as much cable to be wound on one of the cable drums as is unwound from the other one of the cable drums.

It is an advantage if the two cable drums of the cableway system work synchronously when the carriage unit is to be moved in the direction from one of the points of support towards the other one of the points of support, so that as much cable is unreeled from one cable drum as is reeled onto the other one. In the opposite case, the carriage unit - and thereby the object being carried - will have an uneven motion in which it is hoisted and lowered. The transmission device may be connected to one or both of the cable drums. A transmission device will give the possibility of changing the direction of the motion of the cable drums, so that the carriage unit can advantageously go back and forth between the points of support. Further, a transmission device will make it possible to adjust the speeds of the cable drums relative to each other. In an advantageous embodiment, the cable drums will be provided with a transmission means each. This gives further advantages by the fact that, in addition to being driven in the same direction, the cable drums can also be driven towards each other or away from each other. Possibly, one drum may be kept at rest while the other drum is driven towards it or away from it. This has several advantages: firstly, a solu- tion like that will entail the fact that a cableway system of this type will not need separate arrangements for tautening the cable, because the tautening of the cable can be adjusted by running the cable drums in such a way that cable is pulled in. In one example, provided that the cable is wound in such a way on the cable drums that it enters on the upper side of the cable drums when they are in a position of use, it will mean that one cable drum is rotated anticlockwise, whereas the other one is rotated clockwise. Consequently, the main line of the cableway system will be self-supporting. Secondly, this will give the carriage unit the property, when it is attached to cables in a cableway, of being lowerable and liftable just by means of the direction of rotation of the cable drums. If one or both of the cable drums is/are rotated in such a way that the cables are tautened, then the carriage unit is lifted, and vice versa, if one or both of the cable drums is/are rotated in such a way that the cables are slackened, then the carriage unit is lowered. The carriage unit may, for example, be provided with a claw or some other gripping device of a kind known per se, possibly a cable with such a gripping device placed at its end, and the gripping device may be lowered towards the object which is to be lifted, for example a log, just by rotating the cable drums relative to each other. It is thus sufficient for one of the cable drums to be rotated while the other one is kept at rest.

Several types of transmission devices will be known to a person skilled in the art. One example of a suitable transmission device may be a gearing device like a planetary gear. A planetary gear and its operation will not be described in more detail herein as it is known to a person skilled in the art. Another example of a known transmission device which can be used herein, may be a cyclone gear, and yet another example may be a variator.

If both cable drums are provided with a transmission device, the transmission devices may be of the same or different type(s) for the two cable drums.

The cableway system may further include a locking means arranged to prevent rotation of the cable drums when the carriage unit is to be stationary. When a cable drum is rotating, the cable will be wound either on or off. When the cable drum is driven by a driving means, that is to say a power source, whether muscular power, a motor, current supply or other is concerned, the power source may ensure that the cable drum is not moved if it is desirable for the carriage unit to be kept stationary. The purpose of the locking means according to the invention is preventing undesired rotation of the cable drums, also when these are disconnected from the driving means. Thus, one effect of the locking means will be preventing the carriage unit from falling down if the power supply should unexpectedly be interrupted. The locking means may include a brake. The locking means may thus be arranged to fully or partially prevent the rotation of the cable drums, or brake the rotational speed of the cable drums. Thus, the locking means may help the carriage unit not to move too fast or in an un- desired direction if the carriage unit is suspended on a cableway stretch with a tilt deviating from the horizontal.

The cable drums may be of a configuration such that they rotate in the same direction, clockwise or anticlockwise, when the cable is unwound from one of the cable drums and wound onto the other one of the cable drums.

The cableway system may be configured to move the carriage unit between a suspension level and a ground level by adjusting the first cable speed and/or the second cable speed in such a way that they are unequal.

By suspension level is meant herein the level above the ground at which the connections of the cableway system are attached to the supporting elements. It must be understood that this is not an exact level as one connection may, for example, be attached higher above the ground than the other connection. The suspension level may thus be said to be an imaginary straight line between the attachment point of the cableway system to the first supporting element and the attachment point of the cable- way system to the second supporting element.

As mentioned above, the carriage unit may be lifted or lowered by running the cable drums in such a way that both cable drums simultaneously reel cable or simultaneously unreel cable, respectively, or that one cable drum is kept at rest while the other cable drum reels cable in or out. In addition to this, the cable drums may also be run in such a way that one is reeling cable while the other is unreeling cable at a different rate, so as to have a lifting/lowering mechanism which, at the same time, allows movement from one of the points of support towards the other one of the points of support. Such a movement may, for example, be desirable as an object is attached to the carriage unit and is to be lifted again, because the object may then be moved towards a desired point of support while it is simultaneously being gradually lifted by cable being reeled onto one drum faster than cable being reeled off the other drum.

The carriage unit may be so arranged that its position between the suspension level and the ground level can be adjusted either by cable being wound onto both cable drums at the same time or by cable being unwound from both cable drums at the same time. At least the cable drum of one connection may be placed in the carriage unit. An effect of this will be that it will not be necessary to carry a cable drum along into the forest to a suitable point of support; it is sufficient to pull along cable arranged to be attached to the point of support.

Possibly, the cable drums of both connections may be placed in the carriage unit. This will have the effect of the cable drums being positioned so close to each other that some of the elements of the cableway system may be shared by the two cable drums, thereby simplifying the cableway system. This may apply to the transmission device, for example, which may now be shared by the two cable drums, or for example the electric motor, if the cableway system has got one, may be shared by the drums. Another effect may be that the cableway system will be more compact in its inactive, packed-up position, that is to say when the cable has been reeled in on both cable drums.

In those cases, in which the two cable drums are placed in the carriage unit, the locking means may include a toothed belt. In practice, the two cable drums are connected to each other when they form part of the same carriage unit. They may thereby easily be connected to each other with a toothed belt. A toothed belt is an advantageous part of the locking means in such an embodiment, because it may engage with the cable drums and prevent them from rotating in opposite directions when such rotation is undesired, and it may set the cable drums free so they can rotate freely, when this is desirable. Further, the toothed belt may be so arranged that it locks the cable drums to each other if the energy supply to the cable drums stops, thereby preventing the cable drums from rotating in opposite directions then. In that way, the toothed belt may prevent undesired lowering of the carriage unit at a power cut, for example. Further, the toothed belt may advantageously be used when the carriage unit is to be run "horizontally", that is to say along the "suspension level" defined above, in order thereby to absorb forces and have an energy-saving effect on the system.

The driving means may be arranged to drive both cable drums, either directly or indirectly. By indirectly is meant here that the driving means drives the first cable drum, for example, which in its turn, via a connection to the second cable drum, drives the second cable drum. How the driving means is to be connected to the cable drums depends on the positioning of the cable drums. If both cable drums are placed in the carriage unit, a motor, for example, may be placed in the carriage unit and be arranged to drive both cable drums. If one cable drum is in or at one of the points of support of the cableway system, then maybe it is more practical for the driving means to be placed in the vicinity of the point of support as well. This driving means may, in its turn, quite possibly drive two cable drums belonging to adjacent cableway stretches.

The effect of having both cable drums operated by the same driving means is that when the driving means sets the first cable drum into motion, the second cable drum, too, will be set into motion. And then, if one cable drum is connected to the other one by way of a belt, they may automatically rotate in the same direction. This entails the fact that if the cable drums are placed in such a way that the cables enter either on the upper side or on the lower side of both drums in the position of use, the first cable drum will unwind cable while the other cable drum is winding cable, or vice versa. The carriage unit thereby moves along the cableway, that is to say the carriage unit changes its distance from the two supporting elements of the cableway system.

The driving means may be arranged to be connectable to an external energy source via a current-carrying cable.

The driving means may get its energy from an energy source such as an aggregate or a battery pack in connection with the driving means, in connection with one or both of the cable drums, that is, or in close connection to the carriage unit if the cable drums are placed in the carriage unit. The energy source may, for example, be attached to the first cable, the cable of the first connection, that is, or the second cable, the cable of the second connection, that is, when the carriage unit is placed in a position of use. The current-carrying cable may extend, for example, between an aggregate or some other energy source and a motor placed in connection with one or both of the cable drums. The aggregate may be placed on the ground, in connection with one of the points of support of the cableway system, or on the first cable or on the second cable.

However, it will be an advantage if the driving means is arranged to be connectable to an external energy source via a current-carrying cable. By positioning the energy source at a distance from the carriage unit, and preferably at a distance from the load-carrying cable, or the main line, when the carriage unit is placed in a cableway system, there will be less strain on the first cable and the second cable, on the carriage unit itself and on the two supporting elements. The energy source may, for example, be placed on the ground somewhere easily accessible.

The current-carrying cable may be the cable of the first connection and/or the cable of the second connection. This constitutes an advantageous embodiment of the invention. The current-carrying cable may be an electromechanical cable such as a wireline / well cable which is known from the offshore industry or a so-called "umbilical". The effect of this is a simplified structure in which one and the same cable functions both as a main cable, hauling cable and current-carrying cable, and the current is carried directly to the cable drum. This is particularly advantageous in embodiments in which one or both cable drums are placed in the carriage unit.

The carriage unit may include an attachment means arranged to be attached to a load which is to be carried by the cableway system.

Such an attachment means may include a hook, a grapple, a claw or the like, suitable for attachment to the object to be carried. In what follows, the attachment means will also be termed a gripping device. The attachment means may be arranged in such a way that part of it can be attached to or around, that is to say grip, for example timber that is to be carried. When the carriage unit is lowered by means of the first cable drum and the second cable drum, the attachment means or gripping device may be brought into contact with the object, which is to be lifted, and be connected to it.

The attachment means may further include a third cable drum provided with a lifting cable. This will have the advantage of the attachment means having a greater reach as the lifting cable may be provided with said claw, hook or grapple and be extended sideways from the alignment route of the cableway system. Further, it is possible in this way to avoid having to lower the carriage unit all the way down to the object which is to be lifted/carried.

The lifting cable may be a current-carrying cable. This will give the effect of enabling the attachment means to be supplied with current and thereby be given functions such as electrically controlled opening and closing, for example in the form of a quick- release coupling. In that way, the possibility of potentially hazardous situations that may arise if attachment and release of the load is done manually is reduced.

The cableway system may include at least one further carriage unit for suspension between the first point of support and the second point of support, the cableway system including a third connection of variable length, the third connection including a cable drum and a cable to be wound on the cable drum.

Accordingly, in one embodiment, the cableway system may be provided with two or more carriage units on the same cableway stretch. This may be done by one of the connections being attached to two carriage units instead of to one carriage unit and one supporting element. One advantage of having several carriage units between two points of support is that the cableway stretch between the points of support may be made longer because the further connection with a further cable drum will contribute to the tautening of the cableway stretch. Further, it is an advantage that the cableway system becomes more efficient by the carriage units taking over from each other and not having to travel the whole cableway stretch with the load before returning to collect more.

The connections of the cableway system, that is to say the first connection, the second connection, the third connection and any further connections, may include a further cable drum. That is to say, one and the same connection may have two cable drums and a cable which is attached, at one end, to one of these cable drums and, at the other end, to the other one of these cable drums. In that way, a connection may have one cable drum at either end and thereby be attached to the carriage unit via one cable drum and to the supporting element via another cable drum. The various connections in one and the same cableway system may be different, so that some connections may include two cable drums, whereas others may include only one cable drum.

The cableway system may be adapted for expansion by further points of support, carriage units and connections.

Accordingly, the cableway system may be extended by further cableway stretches to the desired reach into the forest, for example by further connections, carriage units and possibly aggregates being transported by the cableway system from the starting point to the first point of support inside the forest. From there, the end of a new connection is pulled through the forest to a further point of support, and at least one new carriage unit is hung off between two connections between the first point of support and the further point of support. In that way, the cableway system can be extended infinitely, without expensive access roads having to be constructed.

In a second aspect, the invention relates more specifically to a carriage unit for use in the cableway system according to the first aspect of the invention.

As mentioned above, the two cable drums may be arranged in the carriage unit. This has advantageous effects such as the cableway system being more compact in transport, and the cable drums allowing operation by the same motor, and making it possible for parts of the locking means, for example a belt, to be shared.

The cable drums of the cableway system may further be arranged for remote control, so that the movement of the carriage unit may be controlled from a distance. In a third aspect, the invention relates more specifically to the use of a cableway system according to a first aspect of the invention for moving an object, for example a log, between the two points of support, wherein :

- the cableway system is connected to the two points of support at a distance above a ground level;

- the carriage unit is attached to the object; and

- the carriage unit is moved by rotating at least one of the cable drums.

A connection comprising a cable drum and an electromechanical cable for energy supply to a carriage unit, for example a trolley, is described as well, the electromechanical cable further being arranged to function as a hauling cable for the carriage unit. This has the effect of allowing a connection of said type to be used in an already existing cableway system of a known type for power supply / energy supply to a trolley without any need for batteries in the trolley, aggregate hanging on the cable, or a separate power cable. In this way, it will be possible to simplify an existing system by having a power cable and hauling cable in one, whereas the prior-art trolley cable runs on a main cable.

In what follows, examples of preferred embodiments will be described, which are illustrated in the accompanying drawings, in which :

Figure 1 shows a plan view of a cableway system according to the invention;

Figure 2 show a perspective view of a cableway system according to the invention;

Figure 3 shows a perspective view of a cableway system according to the invention;

Figure 4 shows a perspective view of a carriage unit;

Figure 5 shows a further perspective view of a carriage unit; and

Figure 6 shows a schematic view of a branched cableway system according to the invention.

In what follows, the reference numeral 1 will indicate a cableway system according to the first aspect of the invention. Like reference numerals will indicate like or corresponding elements in the figures. The various elements in the figures are not necessarily drawn to scale. Reference is first made to figure 1 which shows the cableway system 1 for forestry. In the figure, an object 2 which is to be moved by means of the cableway system 1 is shown in the form of timber. However, it must be understood that the cableway system 1 can be used for moving many different forms of objects 2, and also human beings, for example when the cableway system 1 is used as a rescue line. The figure further shows two supporting elements 3 between which a carriage unit 4 is suspended by means of a first connection 5 and a second connection 6. As defined above, the figure thus shows a cableway system 1 consisting of one cableway stretch. The two connections 5, 6 are arranged to have variable lengths as each of them includes a cable drum 51, 61 and a cable 52, 62 for winding on the respective cable drums 51, 61. In what follows, the two cable drums will be referred to as the first cable drum 51 and the second cable drum 61, and the two cables 52, 62 will be referred to, in what follows, as the first cable 52 and the second cable 62. The two connections 5, 6 may be identical or different, both as far as sizes and components are concerned and as far as the length of cable is concerned. In the figure, the two cable drums 51, 61 are each placed in connection with a respective one of the supporting elements 3. The first cable 52 is attached at one end to the first cable drum 51, then, and at its other end to the carriage unit 4. Correspondingly, the second cable 62 is attached at one end to the second cable drum 61 and at its other end to the carriage unit 4, so that the first connection 5, the carriage unit 4 and the second connection 6 together form the cableway system 1 between, and connected to, the two supporting elements 3. The figure further shows an external energy source 7 which is connected to the first connection 5 via a connection element 71, for example a wire, to supply the first connection 5 with the necessary energy, for example electrical power, for driving the cable drum 51. The energy source may be an aggregate, for example. The first cable 52 may be an electromechanical cable, a so-called wireline / well cable, that is, which is well suited for passing current while, at the same time, it is strong enough to haul and carry load. The carriage unit 4 may be arranged with a current-carrying connection element (not shown), so that the current from the aggregate can be carried to the first cable drum 51, via the first cable 52, through the carriage unit 4 and on through the second cable 62, provided the second cable 62, too, is an electromechanical cable, to the second cable drum 61. A structure like that allows the cableway system 1 between the two supporting elements 3, in addition to being usable for carrying objects, also to be usable for carrying energy up to further connections, branches of the cableway system, or other units or tools that require energy supply and that are at a distance from the aggregate / energy source and thereby cannot be connected directly to it. The carriage unit 4 is further provided with an attachment means 41 also termed a "gripping de- vice" 41 in order to be connectable to the object 2 that is to be carried.

To move the carriage unit 4 in the direction from one of the supporting elements 3 towards the other one of the supporting elements 3, one of the cable drums 51, 61 is activated into paying out cable while, at the same time, the other one of the cable drums 51, 61 is activated into pulling in cable. If, at all times, as much cable is being pulled in on one of the cable drums 51, 61 as is being paid out by the other one of the cable drums 51, 61, the carriage unit 4 will then move smoothly, at the same height above the ground, towards one supporting element 3. However, if more cable is paid out from one of the cable drums 51, 61 than is pulled in by the other one of the cable drums, the carriage unit 4 will lose height and be lowered towards the ground. This is to say that in order to lower the carriage unit 4, the first cable drum 51, for example, may be kept at rest while the other cable drum 61 pays out cable, or the first cable drum 51 may pull in less cable than is paid out by the second cable drum 61. Of course, the roles of the two cable drums 51, 61 may be reversed. The carriage unit 4 may also be lowered by both cable drums 51, 61 paying out cable simultaneously. Correspondingly, the carriage unit 4 may be lifted from the ground by both cable drums 51, 61 pulling cable in simultaneously, by one cable drum 51, 61 pulling cable in while the other one is kept at rest, or by one of the cable drums 51, 61 pulling cable in faster than the other one of the cable drums 51, 61 is paying cable out.

Provided both cable drums 51, 61 are so placed in the position of use that the cable is entering the cable drums from the upper side, this is to say, then, that to move the carriage unit 4 from one supporting element 3 to the other supporting element 3, the cable drums must be rotated in the same direction. The direction of rotation is clockwise for the carriage unit 4 to be moved towards one of the supporting elements 3 and anticlockwise to move the carriage unit 4 towards the other one of the supporting elements 3. The same is the case if, in the position of use, both cable drums 51, 61 are so placed that the cable enters the drum from the lower side. If, in one embodiment, the cable drums 51, 61 are so placed that the cable enters one of the drums 51, 61 from the upper side and the other one of the drums 51, 61 from the lower side, then the cable drums 51, 61 must be rotated in opposite directions to have a movement from one of the supporting elements 3 to the other one of the supporting elements 3. Such a movement between the supporting elements 3 will, in some places herein, be referred to as a horizontal movement, but it must be understood that by this is meant a movement that approximately follows a line from the point where the first connection 5 is attached to a supporting element 3 to the point where the second connection 6 is attached to another supporting element 3. Figure 2 shows the cableway system 1 in an exemplary embodiment in which both the first cable drum 51 and the second cable drum 61 are placed in the carriage unit 4. Furthermore, the carriage unit 4 is provided with a cable drum 8 for a hoisting cable 81, and the hoisting cable 81 is attached to the gripping device 41 in order thus to be able to lift and lower the gripping device 41 by, respectively, pulling in and reeling out the hoisting cable 81. In this way, the cableway system will have a larger reach and the carriage unit 4 may be attached to the object 2 that is to be carried, without the carriage unit 4 itself having to be lowered.

Figure 3 shows the cableway system 1 in which two carriage units 4 are suspended between two supporting elements 3. In this case, the two carriage units 4 are connected to each other by means of a third connection 15 comprising two cable drums 151 and a cable 152. It must be understood that it would be sufficient if said third connection 15 were provided with only one cable drum 151 and were attached to one carriage unit 4 only by a hook or some other connection means. Two carriage units 4 on the same cableway stretch allows a more efficient transport of the object 2 because a carriage unit 4 does not have to travel the whole distance between the two supporting elements 3, but may return to collect another load, while the other carriage unit 4 carries the first object 2 forward.

Figure 4 shows a carriage unit 4 which includes both the cable drum 51 of the first connection 5 with the associated cable 52 and the cable drum 61 of the second connection 6 with the associated cable 62. The carriage unit 4 includes a housing, here in the form of two plates 43 connecting the cable drums 51, 61 to each other and further protecting sensitive parts (not shown). The housing further has the function of making the carriage unit 4 not catch so easily on trees and bushes out in the terrain. A third cable drum 8 is shown as well. As mentioned earlier, this is provided with a lifting cable / hoisting cable for connecting the gripping device / attachment means 41 and hoisting the object 2 that is to be carried. This is not shown in this figure, but can be seen in figure 2, for example.

Figure 5 also shows a carriage unit 4 which includes both the cable drum 51 of the first connection 5 with the associated cable 52 and the cable drum 61 of the second connection 6 with the associated cable 62. The cable drums 5, 6 are provided with a locking means which may comprise a belt 9, for example a toothed belt. Alternatively, the belt 9 may be a chain, toothed wheels or the like. The figure further shows that the carriage unit 4 is provided with a driving means 10 in the form of a motor 10, for example an electromotor, for driving the cable drums 5, 6. In this embodiment, both cable drums 5, 6 are also provided with transmission devices 11 allowing the cable drums 5, 6 to be rotated at different speeds and in both directions, both clockwise and anticlockwise, that is. The transmission devices 11 may be gear devices, for example in the form of planetary gears. The belt 9 will ensure that the cable drums 5, 6 are prevented from counter-rotation if the power supply / energy supply is stopped, and in that way, the belt 9 will ensure that the carriage unit 4 will not fall to the ground if the energy supply should be cut for some reason or other, either unexpectedly or, for example, at the end of the working day. The locking means may further include a brake (not shown) which may prevent rotation of the cable drums. It will be understood that if current supply to the carriage unit 4 is via an electromechanical cable and the electromechanical cable is one or both of the first cable 52 and the second cable 62, the necessary components for transferring the current from the cable 52, 62 to the electromotor 10 must have been provided in the cable drums 5, 6. It will then, for example, be necessary for the cable drums 5, 6 to be provided with a swivel (not shown). This and other components for connecting the cable drums, for example various belts and wires, to the motor will be known to a person skilled in the art and will not be described in further detail herein.

The figure further shows that the first cable drum 51 is connected to a secondary motor 12. This motor 12 will be connected to various sensors (not shown) recording, for example, how much cable is on the cable drums 51, 61. The secondary motor 12 is used to control the cable tautening by synchronizing the peripheral speed, earlier termed the cable speed, of the cables 52, 62.

The cable drum 8 which is used for hoisting and lowering the gripping device 41 (shown in figures 1 and 2) may either be connected to the motor 10 by means of a belt 13, for example, or it may be driven by a separate motor (not shown). The carriage unit 4 may further be provided with a control box 14 which is a protective box for sensitive parts. The box 14 or the protection can accommodate various transmitters, encoders, electronics possibly hydraulics which may be vulnerable to the weather.

Figure 6 shows a principle drawing of a cableway system 1 with several cableway stretches, viewed from above. A cableway stretch is defined, as mentioned above, as the part of a cableway system 1 that is between two "neighbouring supporting elements", that is to say connections 5, 6 and carriage units 4 suspended between two supporting elements 3. The figure shows supporting elements 3 as circles and carriage units 4 as triangles. The lines connecting supporting elements 3 and carriage units 4 symbolize cables, preferably electromechanical cables. As shown, on some cableway stretches, there may be more than one carriage unit. This may give increased efficiency and better tautening of the cable. The cable drums 51, 61 belonging to the different connections 5, 6 may be placed either in connection with the supporting elements 3 or in connection with carriage units 4, or both. It is conceivable that, on some cableway stretches, one cable drum is placed in the carriage unit, whereas the cable drum of the other connection is placed in connection with a supporting element 3. Thus, the cableway system 1 according to the invention becomes very flexible and can be adapted for the local conditions. As mentioned above, it will also be possible for a connection to include two cable drums. Such a branched cableway system 1 may be constructed by starting with one cableway stretch and use this to transport equipment necessary for the next cableway stretch into the forest. Several cableway stretches may be in operation concurrently and carry objects/timber to a collecting point, but it is also possible that only one cableway stretch is in operation at a time, and that other cableway stretches, via their electromechanical cables, carry current to the active cableway stretch.

It is also possible to imagine a cableway system of a known type as the starting point for constructing a cableway system 1 according to the invention. There may be cases in which forestry has been started in an area, but the equipment cannot reach particularly difficult terrain. The existing cableway system may then be used to carry connections 5, 6 and carriage units 4 into the terrain, for example to the end point of the existing cableway system, and be built from there on. Either separately or connected to the cableway system.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.