Title:
MOVABLE FLOOR SUITABLE FOR INSTALLATION ABOVE A STRUCTURE
Kind Code:
A1


Abstract:
A device for forming a walkable floor, for instance above a swimming pool, has elements that may be assembled to be movable between a first position, in which the floor is situated above the swimming pool, and a second position in which the floor is situated adjacently of the swimming pool. The elements are mutually separated by separating surfaces extending substantially transversely of the direction movement, and wherein the elements can be mutually coupled by couplings adapted to transmit pulling and pushing forces in the direction of movement, wherein the couplings are adapted to prevent a relative movement in the direction transversely of the direction of movement.



Inventors:
Van Der, Klooster Johannes Gommert (Hertogenbosch, NL)
Application Number:
12/524022
Publication Date:
03/11/2010
Filing Date:
01/23/2008
Primary Class:
Other Classes:
4/500
International Classes:
E04H4/08
View Patent Images:
Related US Applications:
20050066439Users water storageMarch, 2005Korsinsky et al.
20080066224PUSH BUTTON INCREMENTAL AIR CONTROL VALVEMarch, 2008Wooten
20050086738Stand-alone wash apparatusApril, 2005Gragtmans
20070245473Flushing system for a vacuum toiletOctober, 2007Seibt et al.
20090165201Site-Assembled Pool and Method of AssemblyJuly, 2009Vultaggio
20050144710Toilet seat cover device for automatically laying toilet seat coverJuly, 2005Hattori et al.
20050223484Spa cover systemOctober, 2005Livingston et al.
20080155743Shower apparatus for securing infant and toddlerJuly, 2008Allen
20070245482Curtain for a showerOctober, 2007Jenkins
20050188456Spa cover support and storage unitSeptember, 2005Teitelbaum
20080301865Toilet ventilation system and associated methodDecember, 2008Hand



Foreign References:
BE891983A1982-08-02
Other References:
English Machine translation of WO 02088490 disclosure
English Machine translation of BE 891983A disclosure
Primary Examiner:
SKUBINNA, CHRISTINE J
Attorney, Agent or Firm:
Law Offices of Eric Karich (Eric Karich 20 Crestview, Aliso Viejo, CA, 92656, US)
Claims:
1. Device for forming a removable, walkable floor above a structure to be temporarily covered, wherein the floor is movable between a first position, in which the floor is situated above the structure for covering, and a second position in which the floor is situated adjacently of the structure for covering, wherein the floor is assembled from elements which are mutually separated by separating surfaces extending substantially transversely of the direction movement, and—wherein the elements can be mutually coupled by couplings adapted to transmit pulling and pushing forces in the direction of movement, characterized in that the couplings are adapted to prevent a relative movement of the elements in the direction transversely of the direction of movement.

2. Device as claimed in claim 1, characterized in that the couplings each comprise a magnetic circuit, a first part of which is situated in a first element and a second part of which is situated in an adjacent element, wherein the magnetic circuit comprises at least one magnet.

3. Device as claimed in claim 2, characterized in that the magnet is a permanent magnet.

4. Device as claimed in claim 2, characterized in that an electromagnet is incorporated in the magnetic circuit.

5. Device as claimed in claim 2, characterized in that the magnets are mounted on the elements for tilting at least through a small angle about a horizontal axis on one side of an element.

6. Device as claimed in claim 5, characterized in that the tiltable magnets are encased in a housing of flexible material.

7. Device as claimed in claim 1, characterized in that the couplings are form-locking in the horizontal directions transversely of the direction of movement.

8. Device as claimed in claim 7, characterized in that the couplings are adapted to engage through relative movement in vertical direction of one of the elements relative to the other element.

9. Device as claimed in claim 8, characterized in that the couplings are adapted to block the relative vertical movement between the elements once they have been moved toward each other in horizontal direction.

10. Device as claimed in claim 1, characterized in that the elements are each provided with at least four wheels, and that the wheels are adapted to travel over the edge of the swimming pool.

11. Device as claimed in claim 1, characterized in that the elements are adapted for magnetic levitation.

12. Device as claimed in claim 1, characterized in that the elements are adapted for hydrostatic or pneumatic levitation.

13. Device as claimed in claim 1, characterized in that the elements are wider than the swimming pool and that the cover extends over at least a part of the terrace in the closed position.

14. Device as claimed in claim 15, wherein the elements comprise a concrete construction that is hollow, with side walls, an upper wall and a lower wall extending transversely of the direction of movement.

15. Device as claimed in claim 1, characterized in that the device comprises: a magazine which is placed adjacently of the swimming pool and which is adapted to contain the elements stacked one on top of another in their second position; vertical transport means for moving the elements in vertical direction inside the magazine; and horizontal transport means for moving the elements in horizontal direction between their first position and their position in or above the magazine.

16. Device as claimed in claim 15, characterized in that the horizontal transport means comprise at least one drive element which is movable in the direction of movement and which is adapted to push the elements from their position above the magazine over a distance at least as great as the width of the elements.

17. Device as claimed in claim 16, characterized in that the drive element is adapted to engage on the part of the magnetic circuit of the coupling of an element.

18. Device as claimed in claim 15, characterized in that the vertical transport means comprise a movable carrier which is guided in vertical direction along a frame and which is adapted to carry the elements present in the magazine.

19. Device as claimed in claim 18, characterized in that the frame is provided with two guide tracks which extend at least partly vertically and along each of which a number of links can be moved, that the carrier rests on the upper links and that two drive devices are arranged for driving the links with a stroke corresponding to the effective height of the links, and that the guide tracks extend substantially horizontally under their vertical part

20. Device as claimed in claim 19, characterized in that each of the drive devices comprises an engaging member which is adapted to move between a position in which a link is engaged and a position in which no links are engaged, and to perform a movement in vertical direction; characterized in that the drive devices each comprise an auxiliary frame provided with engaging elements adapted to engage the links, which auxiliary frame is connected rotatably to the frame by at least one first linear drive member extending substantially vertically and which is connected to the frame by at least one second linear drive member extending substantially horizontally; and further comprising a locking device which is movable between a blocking position and a releasing position, wherein the device is adapted to block the movement of the links relative to the frame in its blocking position.

Description:

The present invention relates to a device for forming a removable, walkable floor above a structure to be temporarily covered, wherein the floor is movable between a first position, in which the floor is situated above the structure for covering, and a second position in which the floor is situated adjacently of the structure for covering, wherein the floor is assembled from elements which are mutually separated by separating surfaces extending substantially transversely of the direction movement and wherein the elements can be mutually coupled by couplings adapted to transmit pulling and pushing forces in the direction of movement.

A similar device is known from FR-A-2 843 153. In this known device the elements can be mutually connected by form-locking couplings which engage or release during a relative vertical movement of the elements but which do allow a movement in the transverse direction, i.e. the direction transversely of the direction of movement. This is related to the fact that in this prior art device the elements are moved along rails which extend along the sides of the structure for covering, in this particular case the swimming pool, and which cause relative lateral movements between the elements due to their forced guiding of the elements. This construction further provides the option of absorbing the mutual shear forces between the elements during loading of the floor, whereby a continuous floor is created with a structure which has structurally the mechanical behaviour of a monolithic floor.

The device according to the invention has for its object to provide the option of omitting these rails adversely affecting the appearance of the used structure, such as the swimming pool, which entails that relative lateral movements between the elements cannot always be avoided. For this purpose the invention proposes to provide such a device wherein the couplings are adapted to prevent relative movements in the direction transversely of the direction of movement.

Another advantage of these measures is the fact that the elements need not necessarily extend and move over a straight path; it is also possible for the elements to extend and move along a curved, for instance circular arc-like patn, wiucn can be important in structures having non-rectangular forms.

It is pointed out here that the invention is particularly, though not exclusively, suitable for use on and adjacently of a swimming pool. When the swimming pool is not in use, the swimming pool can hereby be covered so that a safe situation is obtained and contamination or freezing of the swimming pool is prevented. The floor placed on the swimming pool can then be used as terrace, dance floor or sports surface, also depending on the nature of the floor. It is however also possible to apply the floor elsewhere, i.e. not on a swimming pool. It is possible here to envisage tennis courts, so that tennis can be played on a ‘smash court’ in winter and on a classic gravel court in summer. The invention can also be applied indoors, again not only on a swimming pool but also to provide a dance floor or for instance squash courts.

In order to enable play-free coupling of the elements a high degree of accuracy is required both in the manufacture of the elements and in the positioning, shortly before coupling, of the elements for coupling. Play will moreover occur after wear occurs. Not only is this undesirable from a viewpoint of the mechanical operation of the system, but also due to the occurrence of gaps between the elements, which has a very adverse effect on the appearance of the floor positioned above the swimming pool. Gaps are moreover undesirable because outside contamination and/or leakage of cleaning agents from the swimming pool could occur. In order to avoid these drawbacks, a first preferred embodiment proposes that the couplings each comprise a magnetic circuit, a first part of which is situated in a first element and a second part of which is situated in an adjacent element, wherein the magnetic circuit comprises at least one magnet. This is because magnetic couplings allow a play in the lateral and perpendicular direction. They are moreover not subject to wear. It is noted here that the magnetic coupling, in combination with the application of heavy, for instance concrete elements, has the advantage that during stacking the magnetic coupling can be broken without further aids as result of the action of the force of gravity.

According to a subsequent preferred embodiment the magnet is a permanent magnet. The energy consumption can hereby be greatly reduced since no energy is used when the coupling is active. In order to be able to deactivate the attractive force of the magnet for the pushing system so as to enable uncoupling of uie coupling, or in outer words to make the coupling controllable, an electromagnet is preferably incorporated in the magnetic circuit

Although there are numerous possibilities for the configuration of the magnetic circuit between the elements, such as a permanent magnet in a first element and an electromagnet in the second elements, or a combination of the two magnets in a single part, it has been found that a magnetic circuit with one magnet and a metal mating part, each placed in a different element, gives attractive results.

The magnets are preferably mounted on the elements for tilting at least through a small angle about a horizontal axis on one side of an element. When the elements are taken to the position adjacently of the swimming pool the elements must be separated from each other. This separation takes place in the direction known in mechanics as the shear S direction. The force necessary to separate the magnets from each other is already fairly small in this direction. By tiltably placing one of the magnets for separating, the tiltable magnet will tilt during the relative movement of the magnets in vertical direction, whereby the contact surfaces of the magnets are separated from each other and the force required to separate the magnets still further is reduced even more. In this embodiment it is thus not necessary to deactivate the electromagnets. In order to obtain a construction which is as wear-resistant as possible it is recommended that the tiltable magnets are encased in a housing of flexible material.

According to another preferred embodiment, the couplings are form-locking in the horizontal direction transversely of the direction of movement. As alternative to or in addition to the magnetic coupling, a simple method is herein provided for transmitting shear forces in horizontal direction between the elements.

According to an attractive embodiment, the elements are adapted to engage through relative movement in vertical direction of one of the elements relative to an adjacent element. This measure does after all provide the option of directly coupling the elements to each other during unstacking and of uncoupling them during stacking.

This latter embodiment becomes even more attractive when the couplings are adapted to block relative vertical movement between the elements when they are moved toward each other in horizontal direction. The mechanical behaviour of a monolithic floor is hereby approximated best.

It is possible in principle to arrange rails on the sides of the swimming pool. However, these have an adverse effect on the appearance of the swimming pool. A preferred embodiment of the invention therefore provides the option that the elements are each provided with at least four wheels, and that the wheels are adapted to roll over the edge of the swimming pool, whereby rails are no longer necessary. Instead of wheels, it is in principle also possible to make use of magnetic levitation. Magnets are preferably used here which are only active during the movement of the elements, and which can thus be deactivated by being moved from their active position to a passive position.

Instead of magnetic levitation it is also possible to apply hydrostatic or pneumatic levitation, for instance by arranging in the structure bearing the elements small nozzles which are connected to a high-pressure water or gas source.

When applied above a swimming pool the relation to a terrace which is usually arranged around the swimming pool is important. It is possible here to bring the water level of the swimming pool to the same level as the terrace. Because the cover according to the invention has a certain height, the cover will then inevitably protrude above the level of the terrace. It is of course possible that the upper surface of the cover coincides with the level of the terrace, which results in an attractive appearance in the closed position of the cover. It is then however not possible to bring the water level close to that of the terrace.

Particularly in this latter situation it can be attractive when the elements are wider than the swimming pool and when the cover extends over at least a part of the terrace in the closed position. The cover hereby forms as it were a new terrace, which extends at least partially over the fixed terrace. This embodiment is important particularly, though not exclusively, when the swimming pool has for instance a non-rectangular form or when the swimming pool is placed indoors and the space in question is wholly covered by the cover.

This can also be solved by displacing the swimming pool in vertical direction through a distance corresponding to the height of the cover. It is also important here that, in both the open position, in which the elements are arranged adjacently of the structure for covering, and in the closed position in which the elements cover the structure, the pit in which the elements can be stored is covered by an element which lies at the same level as the surrounding surface, so that it does not protrude upward.

In order to obtain a durable and sufficiently rigid construction of the elements, it is recommended that the elements each comprise a self-supporting concrete construction. Due to its great rigidity this embodiment moreover provides the option of covering the element with metals, natural stone, glass, artificial grass, plastics, tiles or another ceramic material which is the same as the material with which the surrounding surface or underlying structure is covered. In order to save weight, it is recommended that the elements are manufactured at least partly from high-strength concrete with a compression strength greater than 65 MPa.

A structurally attractive construction is obtained when the concrete construction comprises a flat part and cheeks extending downward on the sides of the flat part extending parallel to the direction of movement. The construction described thus far can be provided with steel parts which are arranged between the cheeks under the flat part and in which the parts of the magnetic circuit and the wheels are mounted. The structural possibilities of steel are hereby combined with the rigidity of concrete. It is however also possible to make use of a concrete tube construction, of which the above described flat part and the above described cheeks form part The hollow space in this tube construction can be filled with insulating material. The concrete can be formed by reinforced concrete, but also by fibre-reinforced concrete.

It is however likewise possible to make use of materials other than concrete, such as steel, stainless steel, glass, plastic or preserved wood.

In order to place the elements as far as possible out of sight in their position adjacently of the swimming pool, the device according to a preferred embodiment comprises a magazine which is placed adjacently of or at a distance from the swimming pool or the other structure for covering, and which is adapted to contain the elements stacked one on top of another in their second position, vertical transport means for moving the elements in vertical direction inside the magazine, and horizontal transport means for moving the elements in horizontal direction between their first position and their position in or above the magazine. It is noted here that the phrase ‘adjacently of the swimming pool, in addition to meaning adjacently of the swimming pool, is also understood to mean the level above the swimming pool.

In order to simplify the construction of the device the horizontal transport means preferably comprise at least one drive element which is movable in the direction of movement and which is adapted to push the elements from their position above the magazine over a distance at least as great as the width of the elements. The pushing element is preferably adapted to engage on the side of the element for pushing. It is possible in principle to place the horizontal drive element in the projection of the line S from the swimming pool to the magazine. It is then recommended to place the drive element and the magazine below the level of the terrace. It can however also be attractive to arrange the drive element on the sides of the magazine, for instance when insufficient space is available in the projection. The construction for horizontal displacement is placed wholly outside the elements, whereby the displacing mechanism is always accessible without the elements being displaced.

The pushing element is preferably also adapted to re-place the elements at a position above the magazine. The drive element is adapted for this purpose to engage on the part of the magnetic circuit of the coupling of an element.

For transport of the elements in vertical direction inside the magazine, the vertical transport means are preferably provided with a movable carrier which is guided in vertical direction along a frame and which is adapted to carry the elements present in the magazine.

A structurally attractive solution is obtained when the frame is provided with two guide tracks which extend at least partly vertically and along each of which a number of links can be moved, wherein the carrier rests on the upper links and wherein two drive devices are arranged for driving the links with a stroke corresponding to the effective height of the links. Each of the drive devices preferably also comprises an engaging member which is adapted to move between a position in which a link is engaged and a S position in which no links are engaged, and to perform a movement in vertical direction.

A structurally attractive solution is obtained when each of the drive devices comprises an engaging member which is adapted to move between a position in which a link is engaged and a position in which no links are engaged, and to perform a movement in vertical direction.

This construction is preferably implemented when the drive devices each comprise an auxiliary frame provided with engaging elements adapted to engage the links, which auxiliary frame is connected rotatably to the frame by at least one first linear drive S member extending substantially vertically and which is connected to the frame by at least one second linear drive member extending substantially horizontally.

In order to ensure safety a locking device is preferably arranged which is movable between a blocking position and a releasing position, wherein the device is adapted to block the movement of the links relative to the frame in its blocking position.

This locking device is preferably adapted to drive the links situated in the horizontal part of the guide over a short path during the movement from the blocking position to the releasing position.

It is however also possible for the elements to be tilted from their horizontal position to their substantially vertical position when they are stored. Particularly when long structures have to be covered, and there is therefore a large number of elements, the pit in which the elements are stored would become very deep. In order to prevent this, the elements can be successively stored in tilted position. Moisture and dirt are hereby also removed by the force of gravity. Another possibility is to place a pit on both sides of the structure for covering, or to adapt a pit so that it can contain more than one stack of elements.

The invention will now be elucidated with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a device according to the invention;

FIG. 2 is a schematic perspective detail view of the device shown in FIG. 1;

FIG. 3 is a schematic view of an element of the device shown in FIGS. 1 and 2;

FIG. 4 is a schematic detail view of the device shown in FIGS. 1 and 2;

FIG. 5 is a further detailed view of the device shown in FIG. 4;

FIG. 6 show a cross-sectional view of a coupling construction;

FIGS. 7A and 7B show cross-sectional views of a form-locking coupling between two elements in different situations;

FIGS. 8A and 8B are perspective views of the two parts of the coupling shown in FIGS. 7A and 7B; and

FIG. 9 is a cross-sectional view of an alternative embodiment of an element.

DETAILED DESCRIPTION

FIG. 1 shows a cross-section of a swimming pool basin 1 provided with an upper edge 2 over which elements 3 can be moved in order to cover the swimming pool basin.

Elements 3 are movable between their position on edge 2 and a position in a magazine 4 arranged adjacently of swimming pool 2. For vertical movement in the magazine a vertical transport element S is arranged in magazine 4, and for vertical movement from the position above magazine 4 and the position above edge 2 of swimming pool basin 1 there is arranged a horizontal transport element 6 provided with a pushing element 7.

Elements 3 are shown in more detail in FIGS. 2 and 3. Each of the elements comprises a flat part 10 which is preferably manufactured from concrete and which is provided on both its sides with downward extending cheeks 11, preferably also manufactured from concrete. A decorative cover layer, for instance in the form of natural stone tiles 12, is arranged on the upper surface of each of the elements. Other types of covering are however by no means precluded. Arranged under flat part 10 is a steel frame 13 on which coupling elements in the form of magnetic coupling halves 14 are arranged. Also mounted rotatably on frame 13 are wheels 15, with which the elements can travel over the upper edge of the swimming pool. In the drawn embodiment these wheels 15 are set into the concrete cheeks 11, although this does not always have to be the case.

There are two different types of magnetic coupling half 14, i.e. a first type which preferably comprises a permanent magnet. These permanent magnets serve to maintain an attractive force between coupling halves 14 without external energy supply. Magnetic coupling halves 14 of the second type comprise a part of a magnetic circuit for the purpose of forming, together with the permanent magnets, a closed magnetic circuit which serves to urge the two coupling halves 14 toward each other. It is noted here that a permanent magnet can also be incorporated in the coupling halves 14 of the second type. It is however easier and cheaper to use only one part of magnetically conductive material. Also pointed to is the option of incorporating an electromagnet in one or in both coupling halves, the direction of the poles being selected to counteract the action of the permanent magnet. The permanent magnet can hereby be temporarily deactivated for the purpose of uncoupling the elements, for instance during unstacking.

FIG. 6 shows a specific preferred embodiment of magnets 14, wherein one of the magnets is encased in a sleeve 16 a flexible material such as rubber. The magnet 14 encased in rubber 16 will hereby tilt slightly during the separation of elements 3 in the vertical direction, whereby the magnetic forces are reduced during the separating process. Iron parts 17 of the magnetic circuit are arranged in the opposite part of the element. These parts are preferably arranged rigidly in elements 3. As FIG. 6 shows, an element can be engaged by an electromagnet 18 which can be activated and deactivated and which, when activated, exerts a force on the iron part 17 of the adjacent element 3.

In order to move the elements over the upper edge of the swimming pool a preferably hydraulically driven pushing element 6 is arranged, as shown with reference to FIG. 1, which element is not only suitable for pushing the elements from magazine 4 but also for retracting the elements again. For this purpose the pushing elements 6 and elements 3 are themselves provided with magnetic coupling halves 14, these being of the type which is not that of the side of elements 3 directed toward pushing elements 6. Use is however preferably made of electromagnets, since these can be deactivated, whereby, when the elements are moved to the magazine, the pushing element can be separated each time from the elements carried to a position above the magazine. Use cannot after all be made here of the separation between magnets by a movement in the shear direction, which is preferably facilitated by the tiltable mounting of the magnets.

For vertical transport inside magazine 4 a vertical transport element S is arranged which comprises two frames 20 extending substantially vertically in the magazine, in addition to a carrier 21 extending horizontally between frames 20 and guided along frames 20. For vertical movement this carrier is connected to a series of links 22 which are movable in a guide track 23, part of which extends vertically along the frames. The bottom part of this guide track 23 extends horizontally under carrier 21 in order to avoid excessively deep magazines.

hi order to drive the combination of links 22 and carrier 21 along tracks 23 of frames 20, a hydraulic drive mechanism, designated in its entirety with 25, is arranged on each of the frames 20. These drive mechanisms 25 comprise an auxiliary frame 26 which is connected to the associated frame by means of two parallel hydraulic cylinders 27 extending substantially vertically. When these vertical cylinders 27 are activated, auxiliary frame 26 performs a vertical movement relative to frame 20. Auxiliary frame 26 is also connected to frame 20 by two parallel hydraulic cylinders 28 extending substantially horizontally. Auxiliary frame 26 is provided with engaging elements 29 which are adapted to engage links 22 when auxiliary frame 26 is situated in its position close to the frame. Hydraulic cylinders 27 and 28 are here all controlled such that auxiliary frame 26 performs a two-dimensional movement with four paths, wherein engaging elements 29 are in engagement with one of the links 22 during one of these substantially vertical paths, and whereby the associated movement is transmitted to links 22 and thereby to carrier 21. The vertical path of movement in opposite direction, which is performed while engaging elements 29 are not in engagement with links 22, serves for the return movement of the auxiliary frame in order to enable engagement of a subsequent link 22. The movements with a substantially horizontal component serve for moving the engaging elements 29 into and out of engagement with the links.

Further arranged is a blocking frame 30, which is bearing-mounted for rotation on frame 20 and which can be moved between a blocking position and a releasing position by means of a hydraulic cylinder 31. In the releasing position, which is shown in FIG. 5, links 22 can move freely. In the blocking position pins 32 are situated in the path of links 22 so that movement of the links is blocked, hi order to not allow the movement of links 22 to be blocked by the angle in the guide track between the vertical part and the horizontal part thereof during the descending movement of carrier ZU, blocking frame 30 is provided with cheeks 33 which are adapted to exert a force on one of links 22 along the horizontal part of guide rail 23 in the direction corresponding to the descent of carrier 20 during the movement of blocking frame 30 from the blocking position to the releasing position.

Finally, attention is drawn to the fact that the uppermost element remains visible when the swimming pool is opened and all elements are situated in the magazine. It is recommended here that this element is dimensioned to completely fill the opening of the magazine and that the appearance of the upper surface of this element is adapted to that of the surrounding terrace.

FIG. 7A shows two elements 3A, 3B respectively, wherein element 3A is provided with a recess 40, under which is arranged a protruding part 41 on which is placed a nose 42. Element 3B is provided with a complementary coupling part comprising a recess 43, above which is placed a protruding part 44 on the underside of which is placed a toe 45. Toe 45 is here adapted to engage behind nose 42. In the situation shown in FIG. 7A the element 3A is moved from below into the shown position, whereby form-locking between the two elements is automatically obtained. The two elements 3A, 3B will here carry along the other element 3B, 3A respectively in a horizontal movement away from the other element.

In order to also achieve a degree of form-locking in vertical direction, recess 43 is provided with an oblique wall 46 and protruding part 41 is provided with an oblique wall 47. When the elements are moved toward each other into the position shown in FIG. 7B, the oblique walls contact each other so that element 3A is carried along when element 3B is moved upward.

FIGS. 8A and 8B show the two elements 3A, 3B respectively in more perspective view. This shows that a notch 48 is arranged in the protruding part 41 and nose 42, and that element 3B is provided with a protrusion 49. Protrusion 49 fits into notch 48, thereby obtaining a form-locking in the direction transversely of the direction of movement of elements 3. It will otherwise be apparent that form-locking in this direction can also be obtained in other ways.

Finally, FIG. 9 shows a cross-sectional view parallel to the direction of movement of an element 3. Element 3 has a box-like structure SO manufactured from high-strength concrete. Light filling material S1, for instance polystyrene foam, is arranged inside this structure. A cover layer 12 is arranged on the upper side.

This embodiment also shows the presence of two magnets 52, preferably permanent magnets, which are used for magnetic levitation as an alternative to wheels 14 in FIG. 3, for which purpose magnets must also be arranged in the bearing structure. These latter magnets can be formed by electromagnets, though also by permanent magnets, which can for instance be displaced by a change in position between an active and an inactive position.