The present invention relates to a mechanical arrangement for the interconnection of two rail sections included in a system with a road section and its assigned se- ries-oriented, electrically separated, road sections. The system is intended to, in a track provided in the road section, be able to receive a vehicle-related current- collecting means, with the track being adapted to support a current-feedable and en- ergizable electrical conductor. Technical Background of the Invention

A system for electrical propulsion of a vehicle along a road is known from WO 2010/140964. This system has electrical conductors in the form of energizable rails embedded in elongate tracks or canalizations in the road. The vehicle has a current collector shoe that, upon contact with the rail, allows transfer of electric current be- tween the rail and the vehicle, in order to drive the electric motor of the vehicle and, in such a way, also the vehicle. At the upper edge of the track closest to the roadway, a connection to earth potential is arranged.

The road is divided into different consecutive series-oriented, electrically separated, road sections, whereupon the energizable rails of each individual road section are energized only in connection with a vehicle with its current collector shoe passing the road section in question. The length of the road sections is considerably greater than the length of the vehicles, in order to avoid the need for adapting the length of the road sections to a standard length of the vehicles. Instead, the length of the road sections depends on factors such as surrounding terrain, required current and power transfer from the energizable rails to the vehicles, the speed of the vehicles on the road section in question, or other relevant criteria.

Upon installation and mounting of the track with the associated energizable rails, these have to be carried on the road up to the road section in question. Since the road sections are considerably longer than the vehicles that are conveyed thereon, also the track and the energizable rails will be of a significant length, which makes transportation, as well as manufacture and stock-keeping, more difficult.

The road section comprising the rail sections will be subjected to great temperature variations depending on the season and prevailing climate. Temperature varia- tions cause expansions and contractions of the rail sections that are determined by the coefficient of expansion of the selected material of the rail sections. The expansions and contractions give rise to relative movements between the rail sections, foremost in the longitudinal direction depending on their elongate shape. Therefore, it is very important that the arrangement allows relative movements of the rail sections in the longitudinal direction without the current-transferring capacity of the rail sections and at the joint between the rail sections decaying considerably.

US 5,224,575 discloses an example of an expansion joint for electrically conducting rail sections the end portions of which comprise vertical surfaces mating each other that are formed by halving the rail sections vertically in the longitudinal direction, as well as longitudinal horizontal slots. The expansion joint further comprises fastening members in the form of guide blocks having bolts, nuts and intermediate washers to clamp together the end portions, but allow relative movement in the longitudinal direction. The disclosed coupling requires several parts to accomplish an in- tricate coupling that is laborious to mount and install.

US 3,790,725 discloses another example of a thermal expansion joint for electrically conducting rail sections the end portions of which comprise contact surfaces that define a cavity for the receipt of a connector bar mating the cavity. The contact surfaces are identically shaped and depending on a separate connector bar, which in turn is adapted to be inserted and attached to a support member that is attached to a post. The disclosed coupling requires several different subcomponents to accomplish an intricate coupling that is laborious to mount and install.

Therefore, there is a need for developing track constructions comprising electrically conducting rail sections that are adapted to be interconnected in a simple way and that allow transfer of current at the joint between the rail sections also upon relative movements between the rail sections caused by temperature variations, and thereby guaranteeing a power supply to passing vehicles. Summary of the Invention

The object of the present invention is to provide a mechanical arrangement comprising electrically conducting rail sections that are adapted to be interconnected in a simple way and that allow transfer of current at the joint between the rail sections also upon relative movements between the rail sections caused by temperature variations, and thereby guaranteeing a power supply to passing vehicles.

This is achieved by an arrangement according to claim 1 , for the interconnection of two rail sections included in a system with a road section and its assigned series-oriented, electrically separated, road sections and intended to, in a track pro- vided in the road section, be able to receive a vehicle-related current-collecting means, with the track being adapted to support a current-feedable and energizable electrical conductor, said electrical conductor, in the form of a rail, being, within the road section, divided into at least two essentially similar rail sections, where one longitudinal end portion of a first rail section is electrically and mechanically intercon- nected with a longitudinal end portion allocated to an adjacent second rail section.

The rail sections are similar by the fact that they have essentially comparable or similar length and/or geometrical design. Further, the rail sections preferably comprise the same material.

By allowing the electrical conductor to be divided into a plurality of rail sections the end portions of which are adapted to be interconnectable orjoinable in such a way that the contact structures, at least via a respective part, are flush with each other in spite of relative movements and form an elongate electrical conductor within a road section in question, an electrical conductor is achieved that can be made compact upon transportation. Each of the rail sections constitutes a part of the electrical conductor within a road section and has, therefore, a shorter length than the total length of the road section. The length of the rail sections can be adapted according to the road section in question, for instance shorter in curves or along hilly stretches and longer in straight stretches and in flat terrain. Together, the rail sections forming the electrical conductor may, for instance, be adapted to extend the whole length of the road section in question.

Further, in its one end portion, the first rail section comprises a first contact structure. In its end portion facing one end portion of the first rail section, the second rail section comprises a second contact structure corresponding to the first contact structure, at least a part of the first contact structure being adapted to be received in a cavity in the second contact structure in order to, via said first and second contact structures, allow a relative movement in the longitudinal direction of the rail sections caused by a temperature difference. Accordingly, the rail sections are allowed to move in relation to each other in the longitudinal direction.

The first and second contact structures corresponding to each other are adapted to co-operate electrically and mechanically, allowing a transfer of an electric current and voltage between the first rail section and the second rail section. The mechanical co-operation comprises receiving at least a part of the first contact structure in a hollow or cavity in the second contact structure. The hollow or cavity is formed by a recess in the longitudinal end portion of the rail section.

In a preferred embodiment, said first and second contact structures are adapted to form a sliding contact between the rail sections, which sliding contact preferably is adapted to remain intact in a relative movement between the rail sections in the longitudinal direction up to 2 %o of the length of the rail sections.

In yet another embodiment, said first and second contact structures comprise co-operating means to prevent the contact between the rail sections from being broken in a relative movement in the longitudinal direction.

In an alternative embodiment, the first contact structure comprises a projecting tongue the thickness of which in the vertical direction is smaller or generally smaller than the thickness of the first rail section and adapted to be received in the second contact structure.

In a further embodiment, the underside of the tongue comprises a projection that extends in the longitudinal direction of the first rail section. Preferably, the tongue and the projection together form a T-shaped cross-section

In yet another embodiment, the second contact structure comprises a horizontal cavity adapted to receive the first contact structure. Preferably, the lower surface of the cavity comprises a slot that extends in the longitudinal direction of the second rail section.

The tongue and the T-shaped cross-section of the projection are adapted to be received in the complementary shaped slot in the cavity of the second contact structure.

In another embodiment, the top side of the tongue comprises a shoulder that extends in the longitudinal direction of the first rail section. The shoulder forms a continuous contact surface for the current collector shoe in the joint between the rail sec- tions. Preferably, the front surface of the shoulder comprises an upwardly directed chamfer or bevel cut to prevent gravel and other particles from ending up between the contact structures.

In an alternative embodiment, the upper surface of the cavity comprises a through-going slit, which is delimited by two longitudinal side surfaces and a transverse inner surface, and an opening opposite the inner surface. Preferably, the inner surface of the slit comprises an upwardly directed chamfer or bevel cut to prevent gravel and other particles from ending up between the contact structures.

The shoulder of the first contact structure is adapted to be received in the com- plementary shaped slit in the cavity of the second contact structure.

The projection and the shoulder, respectively, of the first contact structure cooperate mechanically with the slot and the slit, respectively, in the second contact structure to prevent relative movement laterally, perpendicular to the longitudinal direction of the rail sections.

In a further embodiment, the arrangement further comprises an elastic material in a space between the contact structures to prevent accumulation of gravel and other particles in the joint between the rail sections.

Brief Description of the Drawings

Figures 1 , 1 A and 1 B show in a perspective view vehicles propellable on a road section comprising a rail construction according to the present invention.

Figure 1C schematically shows two vehicle-related energy sources and a third source of energy external to the vehicle.

Figure 1 D shows a power/time diagram (P/t) illustrating the passage of the ve- hide along a roadway, its stretch of road and its road section.

Figure 2 schematically shows a vehicle-related electrical arrangement.

Figure 3 shows in an end view a vehicle, having a downwardly directed contact means in a co-operation with the energizable electrical conductors assigned to the road section.

Figure 4 schematically shows an electrical arrangement for a number of series- oriented road sections.

Figure 5 schematically shows a rail construction within an individual road section from Figure 4, with an arrangement according to the present invention.

Figure 6 shows a cross-section of a track supporting an electrical conductor. Figure 7 shows in a perspective view an arrangement according to the present invention.

Figure 8 shows in a perspective view from below an arrangement according to the present invention.

Figure 9 shows in a side view a first contact structure in an arrangement according to the present invention.

Figure 10 shows in a side view a second contact structure in an arrangement according to the present invention.

Figure 11 shows in a side view an arrangement according to the present inven- tion in an interconnected or joined state.

Figure 12 shows in a perspective view a detail of a first contact structure in an arrangement according to the present invention.

Figure 13 shows in a perspective view a detail of a second contact structure in an arrangement according to the present invention.

Figure 14 shows in a side view a detail of a first contact structure in an arrangement according to the present invention.

Detailed Description of the Invention

The mechanical arrangement will be described below in more detail with refer- ence to the figures. However, the invention should not be considered limited to the embodiment or embodiments shown in the figures and described below, but may be varied within the scope of the claims.

Accordingly, Figure 1A shows a system "S" adapted for the conveyance of an electric vehicle 1 , propellable by one or more batteries or a battery kit, along a stretch of road 2 and its road section 2a1 as well as 2a1'.

Here, the vehicle 1 is exteriorly an "A-Ford", but here, the same is converted to a battery-operated vehicle, with a continuous access to an external, a third, source of energy, here designated "s1", "Ml".

The vehicle 1 should then comprise a controlling arrangement 3 (not shown) or a control equipment, so that a driver "F" (not shown) can convey and control the vehicle 1 along said stretch of road 2 and its road section 2a1.

The vehicle 1 could also embrace a gearbox and other parts and details that are required for the conveyance of the vehicle, but since these parts are well known to a person skilled in the art, these will not be described in detail. However, an electrically driven vehicle 1 does not need any gearbox, since a speed regulation and a power output can be effected via known electrical and electronic circuits.

Figure 1 B shows, in the same way as in Figure 1A, an electrically propellable lorry 1 b, having a coupled trailer 1c, along the stretch of road 2, 2a and its assigned road section 2a 1.

Figure 1C now clearly shows two vehicle-related and vehicle-associated energy sources, here designated T and "M", a "first" in the form of a diesel generator "G", a "second" in the form of a battery or a battery kit "B", and a "third" source of energy "III" in the form of a source of energy oriented externally to the vehicle, here formed as, via connection means or switches, energizable parallel conductors or rails within the road sections, recessed in tracks and a cavity along the roadway or the whole stretch of road 2.

In Figure C, these are co-ordinated to a vehicle-related control circuit 100, which, depending on a supplied power to an electric driving motor 5, allows selecting all or a combination of the powering energy sources "1", "II" and "III", respectively. Here, the power regulation is illustrated as an accelerator pedal 100a, the movement of which up and down is connected to an actuation circuit "R2" within the control circuit 100, which in turn embraces a circuit "R1" distributing power and energy between the energy sources.

Figure D illustrates in a P/t (power/time)-diagram how a full power or reduced powers could be distributed and transferred for the passage of the vehicle along the different road sections 2a 1 of a roadway or stretch of road 2 by means of the circuit "R1 " and the actuation circuit "R2".

Between the instants of time ti-t ₂ , it is illustrated, in principle, how a full power output from the three energy sources "I", "II" and "Ml" can be realised, with the power output from the energy source "I" illustrated on top, the power output from the energy source "II" illustrated thereunder (slanting lines), and the power output from the energy source "Ml" illustrated at the bottom.

Between the instants of time t3— , there is illustrated, in principle, a reduced power output from the energy sources "I" and "II", while here, the energy source "Ml" is illustrated disconnected.

Between the instants of time t ₅ — te, there is illustrated, in principle, a reduced power output from the energy sources "II" and "III" During this time duration ts-k, full power can be drawn from the energy source "II" and a small surplus can be allowed to trickle charge the battery kit "II", "B".

The battery kit "B" and the second energy source "II", but particularly the third energy source "III" should primarily, via the distributing circuit "R1", feed the motor 5, and for this purpose, it is required that the battery kit "II", "B" has accumulated an energy and in other respects is dimensioned to drive the motor 5 at full power.

The battery kit "II"; "B" should primarily be trickle charged via the energy source "III"; "s1" and secondary be trickle charged or charged via the energy source "I", "G".

The energy or power from the energy sources "I" and "III" can be selected to be 5-30 % of the energy or power assigned to the energy source "II"; "B", such as about 25 %.

The supply voltage to the motor 5 can be selected to be +400 V DC and -400 V DC, i.e., the voltage value 800 V DC.

The proposed system "S" should then primarily comprise one or more, via each an electric motor 5 or motors, electrically drivable vehicles 1 , 1 b, and where the respective vehicle has a power-distributing and/or power-regulating control loop "R1" within the control circuit 100, for the provision of a requisite power and/or a speed regulation via the actuation circuit "R2" and the accelerator pedal 100a.

The requisite output power should be provided primarily by the vehicle's internal energy source "II"; "B" and that secondary should be under trickle charging from the third energy source "III"; "s1". The stretch of road 2 is shown divisible into road sections (2a1 , 2a2, 2a3; 2a1', 2a2', 2a3'), where each one advantageously should be assigned an external source of energy "III", here illustrated as a number of electrical stations "s1".

One or both of the vehicle's external third energy source "III"; "s1" and/or the vehicle-associated first energy source "I"; "G" can be utilized, in order to thereby supplementary charge the battery kit "II"; "B" of the vehicle, during an adapted sequence of time of power output from this battery kit.

In addition to a driving of the vehicle 1 via the battery kits "II"; "B" and during a supplementing charging of the battery kit "N"; "B" along the road sections and the stationary electrical stations "s1" or the third energy source "III", for the conveyance of the vehicle 1 across the road section 2a1 , a requisite additional power and energy may be supplied via the vehicle-associated energy source "I"; "G". Figure 2 shows principally an electrical/mechanical connection arrangement "K" related to a vehicle 1 , (1b) with a schematically shown vehicle-related arrangement in the form of a control equipment 10, in order to direct a vehicle-associated connector or current collector shoe 4 against and to an electrical contact with paired energi- zable lines, in the form of rails 4a, 4b, for a possible common parallel operation of an electric motor 5, from the battery kit "II"; "B" and/or from the stationary station "III"; "s1", and/or from the diesel generator "I"; "G".

Here, the current collector shoe 4 is related to a support 6, which vertically is movably arranged up and down via a first electric auxiliary motor 7 and laterally is movably arranged to and fro via a second electric auxiliary motor 8.

The means and the control of the auxiliary motors 7, 8 that are required for this movement by means of sensors are not shown in detail but are, however, in principle previously known and obvious to a person skilled in the art.

The auxiliary motor 7 and the auxiliary motor 8 are both actuatable in a recipro- eating movement, where a first movement is activated via a first signal on a first conductor 7a and a first signal on a first conductor 8a, respectively, whereas a second (opposite) movement is activated via a second signal on the conductor 7a and 8a, respectively, while the instantaneous setting positions of the motors 7, 8 and carrier 6 are evaluated by one or more sensors (not shown) and indicated via a produced sig- nal on a second line or conductor 7b and 8b, respectively.

These signals on the first conductors 7a, 8a are generated in a central processing unit or control circuit 100 by a control equipment 10, and signals on the second conductors 7b and 8b are produced within the same central processing unit 100, while utilizing position sensors (not shown).

The central unit 100 including the control equipment 10 is a complex unit, which, among other things, via a sensor 16 should be able to detect the presence of and the orientation of the conductors 4a, 4b, and after that lower the current collector shoe 4, via the auxiliary motor 7, to an electrical contact with said conductors 4a, 4b, which here are illustrated as energized or vice versa.

Via a connection 10a to the central unit 100 and the actuation circuit "R2" thereof, the power and energy, which via the circuit "R1" distributing the energy sources is fed to the motor 5, are regulated. For this purpose, it is required that the circuit "R1" is directly controlled by an accelerator pedal 00a (Figure 1C) in order to, via the actuation circuit "R2", supply requisite power to the motor 5. In the shown state, the current collector shoes 4 conduct current and voltage from the energy source "s1";"IH" to the power and energy-distributing circuit "R1". This one or an actuation circuit "R2" detects, via the central unit 100, the power requirement of the motor 5 and primarily feeds the motor 5 with the power it needs ac- cording to the input signal on the connection or line 10a and generated output signal on the connection or line 10b, and thereby the stationary system "s1", "III" should be loaded and supplement the power and energy requirements via the battery kit "M", "B".

A parallel connection of the vehicle's externally tapped-off power "III", "s1" and the vehicle's internally generated power "I", "G" and/or "II", "B" may here be realised via the control loops "R1" and "R2" and by means of the control circuit 100.

Via the line 10a, pieces of information about a desired speed and thereby associated power for the vehicle 1 are fed to the central unit 100, and via internal circuits (not shown) and the function "R2", "10", the circuit "R1" is activated via the line 0b.

Figure 3 shows, in an end view, a vehicle 1 (1 b) with its downwardly directed current collector shoes 4 in a mechanical and electrical co-operation with the two live conductors or rails 4a, 4b assigned to the road section 2a1', as well as an earth connection 4c.

Figure 4 shows an electrical connection arrangement "ΚΓ, wherein road sec- tions after road sections 2a1 , 2a2 and 2a3 and 2a1', 2a2' and 2a3', respectively, which are electrically separated, with their station after station "s1", "s2", "s3" and "s1 ^' ", "s2"' and "s3"', respectively, can be activated and made live from one and the same parent charging source "III", 42, via connection means and switches 43a, 44a, and 45a for one road section 2a, and 43a', 44a" and 45a' for the counter-directed road section 2b, as a vehicle 1 will pass along the road sections 2a, 2b separated electrically but co-ordinated with longitudinal tracks.

For this, a number of switches or connection means are required for a connection and disconnection of the stations "s1", "s2" ... where this connection and disconnection can be effected via stationary sensors (not shown) related to the road sec- tion.

The present invention is based on the presumptions mentioned above and provides, according to Figure 5, a road section 2a1 having two assigned elongate tracks or gaps 51 , 52. The road section 2a1 is electrically separated from adjacent road sections 2a2 by means of electrically insulating road sections 201. In the tracks 51 , 52, current-feedable and energizable electrical conductors 4a, 4b are embedded. When a vehicle passes the road section 2a1, the voltage is switched in, whereupon a transfer of current can be provided between the electrical conductors 4a, 4b and the vehicle-associated current collector shoe 4.

The electrical conductors 4a, 4b are divided into a plurality of rail sections 4a1 ,

4a2, 4a3; 4b1 , 4b2, 4b3 that are adapted to be interconnectable or joinable in such a way they are in close contact, i.e. flush, with each other end-to-end for electrical and mechanical co-operation. Together, the interconnected rail sections 4a1 , 4a2, 4a3 constitute the electrical conductor 4a in the track 51 within the road section 2a1.

Likewise, the interconnected rail sections 4b1 , 4b2, 4b3 constitute the electrical conductor 4b in the track 52 within the road section 2a .

Figure 6 shows a schematic cross-section of the track 51. In the track, the rail section 4a1 is arranged embedded.

Depending on the season, the road section 2a1 including its assigned tracks 51 , 52 and electrical conductors 4a, 4b will be subjected to great temperature variations. This means that the rail sections 4a1 , 4a2, 4a3 will be expanded in the longitudinal direction. The rail sections 4a1 , 4a2, 4a3 are adapted to conduct an electric current and may consist of one or more electrically conducting materials. Different materials have different coefficients of linear expansion, which has the result that the rail sec- tions 4a1 , 4a2, 4a3 may come to expand to different extents and cause mutual relative movements in the longitudinal direction in the joint between the rail sections 4a1 , 4a2, 4a3. Also in those cases the rail sections 4a1 , 4a2, 4a3 comprise one and the same material, relative movements may arise because of temperature expansion. It is utmost important that these relative movements do not cause the contact between two consecutive rail sections 4a1 , 4a2 to be broken, since this gives rise to voltage losses across the electrical conductor 4a and decreases the available power for passing vehicles.

Figures 7-11 show a preferred embodiment of the arrangement according to the present invention, with two rail sections 4a1 , 4a2 that are adapted to be intercon- nected or joined to each other. In its one end portion 401 , the first rail section 4a1 comprises a first contact structure 403. Likewise, in its one end portion 402, which faces one end portion 401 of the first rail section 4a1 , the second rail section 4a2 comprises a second contact structure 404 that corresponds to the first contact structure 403. The contact structures 403, 404 comprise complementary geometrical shapes, for instance a projecting part that is adapted to be entirely or partly received in a cavity.

Upon interconnection of the two rail sections 4a1 , 4a2 with each other, at least a part of the first contact structure 403 will be received in and co-operate with the second contact structure 404 and form a movable sliding contact or joint. The sliding contact allows relative movement between the rail sections 4a1 , 4a2 in the longitudinal direction at the same time as an electrical and mechanical co-operation between the rail sections 4a1 , 4a2 is guaranteed. An applied electric voltage and current will thus be transferred across the sliding contact between the rail sections 4a1 , 4a2 without greater losses.

The contact structures 403, 404 may be formed on the end portions 401 , 402 of the rail sections 4a1 , 4a2 by milling or a similar machining. Alternatively, the contact structures 403, 404 may be formed separately and then be attached to the respective end portion 401 , 402, for instance by means of soldering, welding or another method suited therefor. The important thing is that the electrical and mechanical contact between the two rail sections 4a1, 4a2 is maintained across the end portions 401 , 402 and the contact structures 403, 404.

The first contact structure 403 may comprise a projecting tongue 407, which extends along the whole width of the rail section 4a1. The tongue 407 may be formed by, for instance, milling of the rail section 4a 1. The thickness of the tongue in the vertical direction may be smaller, or generally smaller, than the thickness of the rail section 4a1.

The tongue 407 is adapted to be received in the second contact structure 404 that comprises a cavity or hollow, when the two rail sections 4a1 , 4a2 with their ends 40 , 402 are brought against each other.

The second contact structure 404 may comprise a horizontal, longitudinal cavity or slit 408 that extends along the whole width of the rail section 4a2. The cavity 408 may be formed by milling of the rail section 4a2 and is adapted to receive the first contact structure 403, when the two rail sections 4a1 , 4a2 with their ends 401 , 402 are brought against each other.

The tolerance in the vertical direction between the two contact structures 403, 404 when the first contact structure 403 is received in the second contact structure 404 is selected so that the surfaces of the contact structures 403, 404 are flush with each other, i.e., that the play between the surfaces of the contact structures 403, 404 is as small as possible, preferably equal to zero. Thereby, a good mechanical and electrical contact between the contact structures 403, 404 is achieved and transfer of current without greater losses is guaranteed. If the tolerance is too great, a gap between the contact structures 403, 404 arises, which causes current losses. Prefera- bly, the cavity 408 is formed so that a compressing force is exerted on the tongue 407 when the tongue 407 is received in the cavity 408, for instance by the thickness of the tongue 407 being greater or as great as the vertical extent of the cavity between the upper and lower surface. The extension of the cavity 408 in the longitudinal direction of the rail sections 4a 1 , 4a2 may be essentially greater than the exten- sion of the tongue 407 in the longitudinal direction.

The underside of the tongue 407, facing the track 5 , may be formed with a projection 409, which projection 409 extends in the longitudinal direction of the rail section 4a 1. The projection 409 may extend the whole extension of the tongue 407 in the longitudinal direction, as illustrated in Figure 8. It is also feasible to allow the projec- tion 409 to extend only a part of the extension of the tongue 407 in the longitudinal direction from the end portion 401 of the rail section 4a1. Accordingly, the tongue 407 and the projection 409 form a T-shaped cross-section, which is illustrated in Figure 9.

The lower surface of the cavity 408, closest to the track 51 , may be formed with a slot or chute 410 in the longitudinal direction of the rail section 4a2. The slot 410 is adapted to receive and direct the projection of the tongue 407 409, when the tongue is received in the cavity 408 upon interconnection of the rail sections 4a1 , 4a2. By this co-operation between the projection 409 and the slot 4 0, it is guaranteed that the rail sections 4a1 , 4a2 are allowed to move in relation to each other in the longitudinal direction, but is prevented from moving in relation to each other laterally.

The top side of the tongue 407, facing away from the track 51 , may be formed with a projecting shoulder or step 41 1 , which shoulder 411 extends in the longitudinal direction of the rail section 4a1. The shoulder 411 may partly extend in the extension of the tongue in the longitudinal direction, as illustrated in Figure 7. It is also feasible to allow the shoulder 411 to extend the whole extension of the tongue 407 in the lon- gitudinal direction. The front surface 413 of the shoulder, facing the second rail section 4a2, may be formed with an upwardly directed chamfer or bevel cut.

The upper surface of the cavity 408, farthest away from the track 51 , may be formed with a through-going longitudinal slit 412. The slit 412 opens in one of its end portions toward the first rail section 4a1 and is delimited by two side surfaces, run- ning in the longitudinal direction of the rail section 4a2, as well as a transverse inner surface 414, oriented opposed to the opening. The inner surface 414 may be formed with an upwardly directed chamfer or bevel cut.

The chamfered surfaces 413, 414 are directed upward to be able to press away possible dirt, stones or other objects that may be accumulated in the track, when the rail sections 4a1 , 4a2 are brought together. In such a way, it is avoided that accumulated dirt prevents the relative movement in the longitudinal direction between the interconnected rail sections 4a1 , 4a2.

Figure 1 shows the two rail sections 4a1 , 4a2 in an interconnected or joined state. The two contact structures 403, 404 in the form of the tongue 407 and the cavity 408 co-operate electrically and mechanically for creating a (sliding) contact, which is movable in the longitudinal direction, which guarantees a transfer of current between the rail sections 4a1 , 4a2 also when the rail sections slide apart because of thermal expansion or contraction.

In a preferred embodiment, the contact formed by the contact structures 403,

404 is adapted to remain intact in a relative movement between the rail sections 4a1 , 4a2 in the longitudinal direction up to 2 %o of the length of the rail sections 4a1 , 4a2. This is achieved by the extension of the tongue 407 and cavity 408 in the longitudinal direction being selected so that the created contact always has at least half the tongue 407/cavity 408 as support.

For instance, the total length of the road section 2a1 may amount to 50 m. In the normal case, the electrical conductor 4a consists of five or six rail sections 4a1 , 4a2 ... etc. The length of the rail sections 4a1 , 4a2 ... then falls within the range of 8- 10 m, 2 %o of which corresponds to 16-20 mm.

The coefficient of linear expansion of feasible materials such as iron, steel, copper and aluminium at 20 °C is within the range of 1-2.5 mm/m/100 K or .10- 25x10 ^"6 /°C. This means that a rail section 4a1 consisting of any of the above materials with a length of 10 m would be expanded or contracted 1-2.5 mm at a temperature difference of 10 °C.

In order to meet the requirement that the contact always should have at least half the tongue 407/cavity 408 as support, assuming that the greatest experienced temperature variation amounts to 80 °C, therefore, the size of the cavity 408 and/or tongue 407 has to be 40 mm. The tongue 407 and the cavity 408 may also be assigned different extension in the longitudinal direction. Then, a space 415 arises between the rail sections 4a1 , 4a2. In a preferred embodiment, said space 4 5 is filled with a soft elastic material, such as rubber or a polymer, in order to protect the contact structures 403, 404 from dirt and other objects. The elastic material is adapted to follow the thermal movements in expansion and contraction and to encapsulate the contact structures.

The relative movement between the rail sections 4a1 , 4a2, etc. within a road section 2a1 is not necessarily uniformly distributed, but depends on temperature variations along the road section 2a1 and the nature of the surrounding terrain.

Therefore, a situation may arise where a disproportionate great part of the expansion, and thereby the relative movement, in the longitudinal direction occurs in the joint between two rail sections 4a1 , 4a2. If the relative movement is sufficiently great, the rail sections 4a1 , 4a2 may slide apart, whereupon the electrical and mechanical contact is broken and the power supply and the connection to voltage of the electrical conductor 4a are disconnected.

To prevent this, the contact structures 403, 404 may be equipped with cooperating means that form a mechanical stop and prevents the rail sections 4a1 , 4a2 from sliding apart. The contact structures 403, 404 are allowed to move in relation to each other in the longitudinal direction within a predetermined interval. The co- operating means are preferably formed monolithically, i.e., in one piece, with at least one of the contact structures.

Figures 12-14 illustrate an example of such a monolithic embodiment, wherein the projection 409 of the tongue 407 is equipped with a ratchet 417 having a for- wardly directed chamfered surface 419 and a rearwardly directed surface 421. The ratchet 417 allows movement in one direction, namely directed toward the adjacent rail section 4a2 including its end portion 402 and the associated contact structure 404, but counteracts movement in the opposite direction, from the rail section 4a2.

The track 4 0 in the cavity 408 is correspondingly equipped with a depression or indentation 416 oriented to the innermost part of the track 410, farthest away from the opening that faces the rail section 4a1 including its end portion 401 and the associated contact structure 403. The depression 416 is adapted to receive the ratchet 417 when the rail sections 4a1 , 4a2 are interconnected by means of the contact structures 403, 404. The rear surface 421 is adapted to abut against the edge of the depression 416 and guarantees that the contact that is formed between the contact structures 403, 404 remains intact, also when the relative movement between the rail sections 4a1 , 4a2 exceeds the overlapping range of extension of the contact structures 403, 404 in the longitudinal direction.

Of course, the co-operating means may be formed in another way, for instance by a screw or bolt attached to one of the contact structures that co-operates with an elongate hollow or cavity in the other contact structure, or in another way. The invention should not be considered limited to the embodiment described above as an example.