EP2547498A1

EP2547498A1 - Device and method for producing concrete elements provided with reinforcement, and concrete element produced by that device or method

Info

Publication number: EP2547498A1
Application number: EP11712045A
Authority: EP
Inventors: Sytze Arnold Kuipers
Original assignee: Novatec BV
Current assignee: Novatec BV
Priority date: 2010-03-19
Filing date: 2011-03-21
Publication date: 2013-01-23
Also published as: WO2011115493A1; NL2004438C2

Abstract

The invention relates to a device for producing concrete elements provided with prestressed reinforcement, such as a prestressed wide-slab floor, a solid or hollow pile, but also concrete elements containing cavities, such as a hollow pillar or hollow core slab floor, comprising a mould provided with a mould bottom, an end wall, first reinforcement holders for holding a series of reinforcement parts at one end thereof beyond a mould surface of the end wall, a head plate situated opposite the end wall and second reinforcement holders for holding the reinforcement parts at their opposite end beyond a mould surface of the head plate, wherein the mutual distance between the head plate and the end wall is adjustable from a first mutual distance to a second mutual distance by means of a displacement means and the device is furthermore provided with a setting means for fixing the mutual distance of the head plate and the end wall at intermediate distances, and the device is furthermore provided with a stressing means for prestressing the reinforcement.

Description

DEVICE AND METHOD FOR PRODUCING CONCRETE ELEMENTS PROVIDED WITH REINFORCEMENT, AND CONCRETE ELEMENT PRODUCED BY THAT DEVICE OR METHOD

Background of the invention

The invention relates to a device for producing concrete elements provided with prestressed reinforcement, comprising a mould. The invention also relates to a method for producing concrete elements provided with prestressed reinforcement.

A device of this type is already known, inter alia, from NL8402276. One of the

problems which is discussed in this document is how to prevent concrete pieces from

splintering off a top surface of slabs produced in the mould due to the position of a

pressure where several slabs may touch one another. The document describes a mould provided with a mould bottom and side walls. Such a mould may be several tens of

metres long and several metres wide. A sliding formwork installation for pouring

concrete slurry into the mould runs on rails next to the mould. In the mould,

reinforcement wires which have been arranged with prestressing in the longitudinal

direction of the mould before the concrete slurry is poured. In addition, partition

profiles can be fitted in the mould when it is desired to produce several slabs at once in the mould. Such a mould may lead to large reinforcement losses due to non-optimum

filling of the mould.

EP-493,140 and the earlier US 4,738,605, to which the abovementioned

document refers, describe a device for producing prestressed concrete slabs. In this

device, a mould is used which has a mould bottom and an end wall and a head plate. In order to simultaneously produce several slabs with mutually different dimensions in the mould, partitions are fitted in the mould.

GB 743,708 from 1952 describes a mould and a method for producing prestressed concrete elements. The mould comprises a carriage which can be displaced in the

longitudinal direction of the mould on rails which run parallel to the mould. At one end of the mould, a reinforcement can be connected to the carriage, after which the carriage is displaced to an opposite end of the mould, taking with it the reinforcement. At that end of the mould, there is a recess in the rails and a toothing so that the carriage can be locked there by means of a pin in a toothing. Thereafter, the reinforcement is prestressed by moving the carriage slightly backwards. The length of the mould is substantially fixed. This offers a device by means of which a reinforcement can quickly be produced in one, but usually several concrete moulds. The document does not give any further indication of where the mould walls are located.

Furthermore, the document describes a clamping of the ends which results in an effective use of the reinforcement rods of up to 90 %, which effectively represents a loss of more than 10%. In the case of a mould of several tens of metres, that is more than a couple of metres. In addition, high tensile forces are mentioned, whereas the structure only seems suitable for mild steel.

US 3,223,379 from 1962 describes a device for producing prestressed concrete articles, mainly piles provided with a single reinforcing rod. In this case, mould parts are supplied in the lateral direction. The device relates to a complex installation for displacing complete mould parts and is limited to using a single reinforcing rod.

A problem with known devices and methods is inter alia the loss in production capacity and material which occurs when fitting different mouldings in an available mould surface.

Summary of the invention It is an object of the invention to provide an improved device for producing concrete elements provided with prestressed reinforcement.

It is a further or additional object of the invention to provide such a device by means of which such concrete elements can be produced in a more flexible manner and more cost-efficiently.

To this end, the invention provides a device for producing concrete elements provided with prestressed reinforcement, such as a prestressed wide-slab floor, a solid or hollow pile, but also concrete elements containing cavities, such as a hollow pillar or hollow core slab floor, comprising a mould provided with a mould bottom, an end wall, first reinforcement holders for holding a series of reinforcement parts at one end thereof beyond a mould surface of the end wall, a head plate situated opposite the end wall and second reinforcement holders for holding the reinforcement parts at their opposite end beyond a mould surface of the head plate, wherein the mutual distance between the head plate and the end wall is adjustable from a first mutual distance to a second mutual distance by means of a displacement means and the device is furthermore provided with a setting means for fixing the mutual distance of the head plate and the end wall at intermediate distances, and the device is furthermore provided with a stressing means for prestressing the reinforcement.

The invention furthermore relates to an assembly comprising a set of moulds provided with a prestressed reinforcement for producing concrete elements, such as a prestressed wide-slab floor, a solid or hollow pile, but also concrete elements containing cavities, such as a hollow pillar or hollow core slab floor, wherein the moulds are provided with a mould bottom, an end wall, first reinforcement holders for holding a series of reinforcement parts at one end thereof beyond a mould surface of the end wall, a head plate situated opposite the end wall and second reinforcement holders for holding the reinforcement parts at their opposite end beyond a mould surface of the head plate, wherein the mutual distance between the head plate and the end wall is adjustable from a first mutual distance to a second mutual distance by means of a displacement means and the device is furthermore provided with a setting means for fixing the mutual distance of the head plate and the end wall at intermediate distances, and the assembly is furthermore provided with at least one stressing means for prestressing the reinforcement.

The assembly may for example form part of a so-called carrousel arrangement of moulds which move past the various production stations.

As the distance between the head plate and the end wall is mutually adjustable, the mould can be used in a more flexible manner. This is due to the fact that it is possible to better fit the desired elements which are being produced simultaneously into the mould with minimal waste or loss of reinforcement material. In addition, the reinforcement can be positioned more quickly.

It has, inter alia, been found that the current manufacturing systems which use moulds generally lead to loss of reinforcement which will be referred to below as mould loss and elongation loss.

Mould loss

For the production of concrete elements, a mould is usually used which is provided with a prestressed reinforcement which extends from one mould wall to an opposite mould wall. Usually, a number of concrete elements are produced in such a mould in one production run, which are often fitted into the mould by means of optimum fit, so that the surface of the mould is used in an optimum manner. In this case, end parts are placed in the mould between the various concrete elements. After a concrete composition which has been introduced into the mould has hardened or set, these end parts can be removed and the various concrete elements in the mould can be separated from one another by severing the reinforcement between the concrete elements. Inevitably, this will obviously result in loss. It has additionally been found that the total length of the fitted concrete elements is usually (significantly) shorter than the mould length. However, in the known moulds, the reinforcement extends along the entire mould length. This problem can be solved by means of known end parts, but it leads to significant reinforcement losses, in many cases amounting to several metres per reinforcement part. This loss is referred to in this text as mould loss. In addition, so- called elongation loss also occurs. Elongation loss

Reinforcement extends from wall to wall. This reinforcement has to be incorporated in the concrete composition under prestress. One problem which the inventors have found is the loss of reinforcement which occurs. This loss appears to be significant. Usually, a mould for concrete elements with reinforcement under prestress has a fixed mould length and the reinforcement extends along the length of the mould. Ends of the mould are delimited or set by an end wall and a head plate which is situated opposite thereof. The end wall and the head plate thus delimit the ends of the mould. The reinforcement then has to extend beyond a mould surface of the end wall or the head plate, respectively, as the reinforcement otherwise does not extend as far as the end of the concrete element to be produced. In practical terms, the reinforcement will extend through the end wall or the head plate, respectively, and will be held on the other side. Next, prestress has to be applied to the reinforcement, which will cause the reinforcement to extend. If the moulds which are used in the production of concrete elements can have lengths from several tens of metres to more than one hundred metres, and a prestress of 500 - 1500 Newton/mm² is applied, the reinforcement will extend approximately 5 - 100 cm. In an embodiment, the mould is up to 20 metres long, and the reinforcement will extend 5 - 100 mm. The reinforcement can then extend at least across that additional length beyond the mould surface of the end wall or head plate, respectively. After a concrete composition has been poured into the mould and has hardened, and the prestress is cancelled, the reinforcement will extend at least for that extended length outside a concrete element. This protruding part of the

reinforcement will then usually be removed and has to be regarded as loss. This quickly adds up to at least one metre of reinforcement per production run. It has therefore been found to be desirable to place and keep the mould surface of the end wall and the head plate as close as possible to the end of the reinforcement.

In an embodiment of the device, the head plate is displaceable by means of the displacement means from a first position to an end position at a greater distance from the end wall than the first position and the setting means is configured to fix the head plate at intermediate positions. Thus, reinforcement parts can be readily fitted. In addition, mould loss and reinforcement loss can be reduced. In an embodiment, the head plate is placed against the displacement means.

In an embodiment, the displacement means is mounted on the concrete mould so as to be displaceable.

In an embodiment, the stressing means engages with the displacement means. In this case, an embodiment is conceivable in which a displaceable device is arranged with respect to the displacement means and the rest of the concrete mould. This stressing means may be provided with tensioning cylinders which are provided on the portal or otherwise a frame. One end of the tensioning cylinders can then be fastened to parts of the displacement means and the displacement means can be displaced by means of the tensioning cylinders, thus prestressing the reinforcement. In an embodiment, the bottom part, the end wall, the head plate and side walls substantially delimit a rectangular mould shape.

In an embodiment, the stressing means is placed on the displacement means.

Thus, for example, tensioning cylinders can be mounted on the displacement means. One end of the tensioning cylinders can then be attached to the rest, the static part, of the concrete mould once the displacement means has been brought into a position, after which the reinforcement can be prestressed.

In an embodiment, the head plate is connected to the displacement means by means of an adjusting means for continuously adjusting the position of the head plate with respect to the displacement means. After the prestress has been applied, the head plate can be adjusted with respect to the displacement means and with respect to reinforcement holders. As a result thereof, a distance can be created between the reinforcement holders and the head plate, through which the reinforcement can be passed after the concrete mass has hardened or the ends of the reinforcement can be detached from the reinforcement holders.

In an embodiment, the second reinforcement holders are fixedly connected to the displacement means.

In an embodiment, the head plate is displaceable along a head plate displacement line. In many cases, said displacement line will coincide with the longitudinal axis of the concrete mould.

In an embodiment, the displacement means comprises a rail extending along the mould and parallel to the head plate displacement line, and a frame with running parts which run over the rail, wherein the head plate is connected to the frame. A rail makes smooth displacement of the displacement means possible.

In an embodiment, the device is furthermore provided with a drive for driving the frame for displacing the head plate. This makes automatic adjustment possible.

In an embodiment, the head plate can be displaced parallel to and between side walls.

In an embodiment, the second reinforcement holder and the head plate are displaceable with respect to one another along the head plate displacement line. Thus, once the concrete mass has hardened, a space can be created as a result of which the reinforcement can be detached from the reinforcement holders. In an embodiment, the second reinforcement holders are displaceable with respect to the head plate.

In an embodiment, the setting means comprises a gear rack track along at least a part of the mould along the rail and the gear rack track is provided with a first toothing, and the setting means furthermore comprises a locking part on the carriage, which locking part is provided with a second toothing and the second toothing can be brought into engagement with the first toothing. This makes it possible to fix the position of the displacement means with respect to the rest of the concrete mould, in particular once the prestress has been applied to the reinforcement. The adjustment and with respect to the length of the concrete mould substantially continuous. By means of fine adjustment during which the head plate can be continuously displaced and adjusted with respect to the displacement means, a continuous adjustment of the distance between head plate and end wall is possible. Alternatively, the end wall could also be continuously adjustable in order to make continuous adjustment of the distance possible. An advantage of the adjustment of the head plate is that the ends of the reinforcement can be readily detached after hardening. In other words a displaceable wall on and with respect to the displacement means in this case is advantageous.

In an embodiment, the setting means comprises a pawl which is rotatable about an axis of rotation on the carriage and is provided with the second toothing, and a wedge which is movable towards the axis of rotation and is connected to a power unit so that, when the power unit is activated, the wedge is displaced towards the axis of rotation and exerts an upward force on the pawl so that the second toothing engages with the first toothing for fixing the position of the head plate. This makes it possible to produce a setting which can withstand the large prestressing forces.

In an embodiment, the setting means comprises a clamping part which engages with a stationary part of the concrete mould in a clamping or frictional manner, thus making continuous fine adjustment possible. In an embodiment thereof, the displacement means may be provided with clamping parts which can be brought into engagement with, for example, the rail over which the displacement means runs if such a rail is being used. Alternatively, the clamping part can be brought into engagement with another part of the static part of the concrete mould.

In an embodiment, the device is furthermore provided with stressing parts for displacing the second reinforcement holder.

In an embodiment, the stressing parts are placed on the displacement means and the second reinforcement holder is coupled to the stressing parts so as to be displaceable on the displacement means.

In an embodiment, the second reinforcement holder is movably provided on the displacement means for independently stressing the reinforcement and displacing the head plate.

In an embodiment, the reinforcement parts are selected from the group comprising reinforcement rods, reinforcement cables, reinforcement wires, and a combination thereof. In an embodiment, these reinforcement parts are made of steel or plastic.

In an embodiment, the mould is elongate and the side walls are longitudinal walls. In an embodiment, the head plate can be moved away from the end wall to a head plate end position.

In the embodiment of the assembly, a stressing means is displaceable between the moulds, or the moulds are provided with a displacement device in order to move past the stressing means.

Due to relatively expensive tensioning cylinders or screws and the relatively short period of use during the entire production process, the stressing means is only used for a short time. A single stressing means may then be used for different moulds, which may result in a significant reduction in costs.

In an embodiment of the assembly, the stressing means comprises a fixing means for fixing the stressing means in a position on the mould, in an embodiment the fixing means comprises a clamping part which engages with a stationary part of the concrete mould in a clamping or frictional manner, as a result of which a continuous fine adjustment of the stressing means on a mould can take place.

Thus, the stressing means can be used in a flexible manner, and also

independently from the mould. The second reinforcement holders with head plate are displaced further by the stressing means which fixes itself to the mould so that the reinforcement is prestressed. Once the reinforcement is prestressed, the fixing means can fix the ultimate position of the head plate with the second reinforcement holders on the mould. The stressing means can then be detached from the mould and the head plate and second reinforcement holders and can, for example, be used to prestress the reinforcement in a subsequent mould.

The invention furthermore relates to a method for producing a concrete element provided with prestressed reinforcement parts by means of the described device, comprising the following steps:

- displacing the head plate to a setting position at a distance from the end wall;

- fixing the head plate at the setting position, and

- exerting a tensile force on the reinforcement parts in order to produce a mechanical tensile stress on the reinforcement parts.

The invention furthermore relates to a method for producing at least one concrete element provided with prestressed reinforcement, comprising positioning reinforcement elements in a mould, prestressing the reinforcement elements and introducing a concrete composition into the mould, wherein a desired mould length is determined before introducing the concrete composition, the mould length being the distance between an end wall and a head plate between which the prestressed reinforcement elements extend, wherein the mutual distance of the end wall and the head plate is set to a first distance equal to the desired mould length minus the extension of the reinforcement elements at a set prestress, after which the reinforcement elements are prestressed to the set prestress.

In an embodiment of this method, the distance between the end wall and the head plate is set after the prestress has been applied, following which the mutual distance between the end wall and the head plate is adjusted by means of a fine adjustment of the head plate.

In an embodiment of the method, before the prestress is applied, the mutual distance is the first distance plus a detachment distance, following which the reinforcement elements are prestressed to the set prestress, and then the head plate is displaced in the direction of the end wail up to the desired mould length. It has been found that displacing the head plate over a limited distance, for example the detachment distance, makes it simpler to detach the concrete elements from the mould by simply removing the prestress.

The invention furthermore relates to a concrete element comprising prestressed reinforcement parts which extend in at least one direction in the concrete element, wherein the concrete element has been produced by means of the device according to the invention or by means of the method according to the invention.

In an embodiment, the device is furthermore provided with a controller device into which the desired mould length, the type of reinforcement and the prestress can be input. The device may then furthermore be provided with a sensor for sensing the mutual distance between the head plate and the end wall. This sensor is connected to the controller device. The controller device is operationally connected to a drive for the displacement means for successively displacing the displacement means and applying a set prestress, so that, once the prestress has been applied, the distance from the head plate to the end wall corresponds to the set mould length. In a further embodiment, the head plate is displaceable with respect to the displacement means by means of the setting means. The controller device is furthermore operationally connected to the setting means in order to activate the setting means after the prestress has been applied until the distance between the end wall and the head plate corresponds to the desired mould length.

The invention furthermore relates to a device provided with one or more of the characterizing features described in the attached description and/or illustrated in the attached drawings.

It will be clear that the various aspects mentioned in the present patent application can be combined and may each be considered individually for a divisional patent application. Brief description of the figures

The attached figures illustrate an embodiment of a device according to the invention, in which:

Fig. 1 shows a top view of an embodiment of the device;

Fig. 2 shows a cut-away side view or longitudinal view of the device from Fig. 1 in more detail;

Fig. 3 shows a side view of Fig. 1;

Fig. 4 shows a cross-sectional view of Fig. 3;

Fig. 5 shows a perspective view of Fig. 3;

Fig. 6 shows a perspective view of Fig. 3 during fitting of the reinforcement cables in the mould;

Fig. 7 shows a detail of an embodiment of the setting means,

Fig. 8 shows a perspective view of an alternative supporting frame;

Figs. 9 and 9a show details of Fig. 8;

Fig. 10 shows a side view of an embodiment of the device in which the setting means is provided with a braking system;

Fig. 11 shows an alternative embodiment provided with the supporting frame from Figs. 8-10;

Fig. 12 shows the stressing means from Fig. 11 in perspective view, and Fig. 13 shows the embodiment from Fig. 11 in front view.

Description of embodiments Fig. 1 shows a top view of an embodiment of a concrete mould 1. In such a concrete mould 1, reinforcement parts can be prestressed and by pouring in concrete slurry or concrete mortar and allowing it to harden, concrete elements can be produced. It is known to produce concrete slabs comprising prestressed reinforcement in such a way. These concrete slabs are often used as floorboards. It is also possible to produce other concrete elements, for example foundation piles, sleepers for rails and the like.

Such a concrete mould 1 has a mould bottom 2. In this embodiment, the mould is rectangular and has an end wall 3, parallel side walls 8 and 8' and a head plate 5 opposite the end wall 3 and parallel thereto. Alternatively, the concrete mould may be non-rectangular. For example, the side walls may not be mutually parallel. The end wall 3 has a mould surface 18 which is in contact with the concrete mortar when concrete mortar is present in the mould. Head plate 5 also has a mould surface 17 which comes into contact with the concrete mortar.

The concrete mould 1 furthermore has first reinforcement holders 4 near the end wall 3 in order to hold reinforcement elements. Furthermore, the concrete mould 1 has second reinforcement holders 6 near the head plate 5. In order to prevent the reinforcement holders from becoming stuck in the hardened mass of concrete, the reinforcement holders 4, 6 are usually provided beyond the end wall 3 and head plate 5, respectively. Often, the ends of the reinforcement are provided with sleeves attached thereto and the sleeves are secured in a facility behind the mould surface of the wall in order to prevent the sleeves from being stuck in the concrete. Alternatively, the reinforcement parts are provided or may be provided with an upset end. In that case, it is conceivable for the upset head to be held in the respective mould wall. After installation and hardening of the concrete slurry, only the upset head will protrude from the concrete element and, if desired, have to be removed therefrom.

In this embodiment, both the head plate 5 and the second reinforcement holders 6 are furthermore mounted on a displacement means 7.

Figs. 2-6 show the displacement means in more detail. Fig. 2 shows a partial section in the longitudinal direction of displacement means 7. Fig. 3 illustrates a side view and Fig. 4 shows a cross section of a part of the displacement means 7 including a part of the further concrete mould 1. Figs. 5 and 6 show perspective views of a part of the displacement means 7. Fig. 2 shows how the displacement means 7 of the concrete mould 1 is provided with a rail 10 which extends in the longitudinal direction along the mould. Such a rail 10 may be provided on both sides of the concrete mould 1. The displacement means 7 furthermore comprises a frame 19 provided with wheels; here, one wheel 11 is shown. By means of a drive device, the displacement means 7 can be displaced from a first position to a second position along the longitudinal direction of the concrete mould 1. The embodiment described here is a mechanical solution which enables adjustments to be made without requiring great force and which is sufficiently strong for a working environment in which concrete mortar is used.

The concrete mould 1 is furthermore provided with a setting means provided with various components for fixing the displacement means 7 in a desired position. This makes it possible to adjust the position of the head plate 5. For this purpose, the concrete mould 1 in the illustrated embodiment is provided with a gear rack track 12 which extends along the concrete mould 1 in the longitudinal direction above the rails 10. If desired, such a gear rack track 12 may extend on both sides of the concrete mould 1. The setting means furthermore has a locking part 9. In this embodiment, the locking part 9 comprises a pawl 13 which is rotatable about an axis of rotation R. On the side turned towards the gear rack track 12, pawl 13 is provided with a toothing having the same pitch as the toothing of the gear rack track 12. The locking part 9 furthermore comprises a roller 14 which can be displaced by means of a drive 15, in this case a hydraulic cylinder 15, and which can push the toothing of pawl 13 against the toothing of the gear rack track 12 in a blocking manner. Here, drive 15 can displace the roller 14 along the rail 10. The roller 14 is arranged in such a manner with respect to the axis of rotation R and the bottom side of the pawl 13 that, upon displacement, the roller 14 brings the pawl 3 into engagement with the gear rack track 12.

Alternatively, the setting means may comprise parts which, by means of friction, engage with one another and thus fix the position of the displacement means 7. In this case, one part may be connected to the displacement means 7 and may be displaced with the displacement means when the latter is displaced. An example of such a setting means is a braking device which is connected, in particular mounted on, the displacement means 7. This braking device can engage with a brake surface at another part of the concrete mould 1, for example a brake surface which extends along the displacement direction of displacement means 7. In an embodiment, the brake surface may, for example, be fitted instead of the gear rack track of the illustrated embodiment. It is even conceivable for a part of a structural beam to be configured as a brake surface. Another example of a suitable setting means is a clamping part which is connected to the displacement means and can be brought into clamping engagement with a stationary part of the concrete mould 1. In an embodiment, this may be a leg of the H beam which extends as a supporting beam along the mould in the embodiment. This embodiment is shown in side view in more detail in Fig. 10. Compared to the embodiment illustrated above, it has been found that further simplification is possible here. The H beam 30 (see also Fig. 4) has an upper leg 31 and a lower leg 32. A rail 10 for the wheels 11 is fitted to the lower leg 32. A brake calliper comprising an upper brake calliper part 33 and a lower brake calliper 34 extends around the upper leg 31 in the longitudinal direction of the H beam 30. The brake calliper parts 33, 34 are provided with brake linings 35 and 36, respectively, which can be brought into engagement with the surface of the two sides of the upper leg. By means of

accumulators, for example hydraulic cylinders 37, the brake linings 35 and 36 can be moved towards one another in order to clamp upper leg 31 in between. In this case, the wheels 11 are lifted off the rail 10. An advantage of the brake callipers is that any pressure can be reduced slowly, in particular in combination with hydraulic cylinders as actuators. Thus, the concrete element is not subjected to significant shocks if the tensile force on the reinforcement has to be reduced in order to release it from the mould. In addition, such an arrangement can be clamped for a long time in order to give the concrete the opportunity to harden. By means of an accumulator, it is possible to, for example, apply an initial pressure of 200 bar, while an activation pressure for an adequate brake action is 80 bar. This makes it possible to exert a braking force for more than 24 hours. In addition, this also makes continuous adjustment along the entire track of the mould possible. The tensile force can also be regulated more accurately. If desired, the brake calliper may extend for several metres in order to generate sufficient braking force. In addition, such a clamping part is usually provided on both

longitudinal sides of the mould.

Fig. 3 shows in side view that displacement means 7 is provided with a frame 19 and a supporting frame 23 thereon which can be tilted about axis of rotation R2. By means of a drive 16, in this case again a hydraulic cylinder, supporting frame 23 can be tilted with respect to frame 19 and the concrete mould 1. Fig. 4 shows a detail of displacement means 7 in cross section and illustrates how wheel 11 can run on rail 10.

Figs. 5 and 6 show a detailed perspective view of displacement means 7. Fig. 6 illustrates supporting frame 23 in a tilted position, and also shows the abovementioned reinforcement elements 22. In this case, the reinforcement elements 22 are steel cables, but other reinforcement elements are also possible, such as for example metal or plastic rods and plastic cables. The ends of the reinforcement cables 22 are provided with sleeves 20. The reinforcement cables 22 run through a holding beam 26. Furthermore, the reinforcement cables 22 also pass through holes in head plate 5. The sleeves 20 rest in apertures in the holding plate 24. In addition, the holding beam 26 is fixedly connected to supporting frame 23 via holding plate 26. By means of shafts 21, the head plate 5 is connected to one or more actuators, in this case hydraulic cylinders, as a result of which the head plate 5 can be moved from the position illustrated in Fig. 6 with respect to holding beam 26.

As the supporting frame 23 can be tilted, as has been described above, it is possible to ensure that reinforcement elements 22 stay clear of the mould bottom 2 when the displacement means 7 are being displaced. The flap 27 ensures that the reinforcement holders and holding beam 26 remain free from concrete.

Fig. 7 shows in detail how the toothing on pawl 13 can be brought into engagement with the toothing of gear rack track 12.

The device furthermore comprises a stressing means which, in this embodiment, is configured as follows. Displacement means 7 is provided with lugs 25 on both sides of the displacement means. The stressing means is displaceable with respect to the mould. In the embodiment, the stressing means comprises a portal. Here, the portal is provided with tensioning cylinders. The portal is put in position with respect to displacement means 7 and the rest of the concrete mould 1. Then, the stressing means is bolted to the rest of the concrete mould 1 and a part of the tensioning cylinders which is displaceable with respect to the rest of the stressing means engages with a respective lug 25. By means of the tensioning cylinders, displacement means 7 can now be displaced over a relatively short distance, as a result of which the reinforcement elements 22 are prestressed. In an alternative embodiment, tensioning cylinders can be attached to displacement means 7. In order to be able to apply the prestress, one end of the tensioning cylinders is then connected to the remaining, static part of the concrete mould 1.

In use, the concrete mould 1 may operate as follows. Displacement means 7 is taken to the end wall 3 in the first position. There, reinforcement elements 22 are fixed in the reinforcement holders 6 of displacement means 7. If necessary, the supporting frame 19 is tilted as far as the position illustrated in Fig. 6. Subsequently, the displacement means is displaced along the longitudinal direction of the concrete mould 1 to a first adjustment position. Once it has arrived there, the supporting frame 1 is tilted until it has reached the position which is, for example, illustrated in Fig. 3.

Thereafter, the reinforcement elements 22 are fixed in the reinforcement holders 4 of the end wall 3. Then, the reinforcement elements 22 are prestressed by means of the stressing means which engages with lugs 25 on the displacement means. In this case, in the embodiment, the displacement means moves further away from the end wall to a second adjustment position. The setting means is activated and the position of the displacement means 7 is fixed. Subsequently, using a head plate displacer situated on displacement means 7 and coupled to rods 21 of Fig. 6, the head plate 5 is moved a few centimetres in the direction of the end wall 3 for the purpose of fine adjustment to the concrete element end to be poured. The head plate 5 thus reaches its end position. The mould is then filled with concrete in a conventional manner. After hardening, the prestress is released from the reinforcement elements. To this end, the setting means is unlocked. Thereafter, head plate 5 is displaced in the direction away from the end wall, towards the second reinforcement holders 6 by means of the head plate displacer. As a result thereof, a space is created between the head plate 5 and the concrete element through which the reinforcement elements can be passed.

In the concrete mould 1 according to the invention, it is furthermore possible to simultaneously produce several concrete elements simultaneously in the known manner. To this end, various partitions can be placed in the mould in a manner known per se, as a result of which several moulded pieces can be produced simultaneously. By adjusting the head plate, it is thus possible to set the outer dimensions of the concrete mould in such a manner that the various concrete elements are fitted in an optimum manner and with minimal loss of mould surface. In other words, the effective mould dimensions can be set in such a manner that the desired concrete elements can be fitted into the concrete mould in an optimum manner and with minimal reinforcement loss and loss of lost concrete mould surface.

Figs. 8, 9 and 9a show an alternative device of supporting frame 23 which can be combined with the above-described device. In this embodiment, the ends of reinforcement elements 22 can be upset first in a manner known per se for upsetting rods or cables. Partly as a result thereof, reinforcement loss can be limited to a minimum. Supporting frame 23 is provided with a comb 40, in this case provided with tapered slots in which reinforcement elements can be placed. In an embodiment, for example, iron or steel reinforcement elements are lifted using a magnetic beam and are subsequently placed in the slots 43 of the comb 40. Displacement means 7 is then usually situated near end wall 3. With a different reinforcement density, another toothing can be used. By means of actuator 42, the beam which forms head plate 5 is tilted from the starting position in Fig. 9a to the locking position in Fig. 9. Head plate 5 is in this case provided with slots 41 in register with the comb 40. Now, displacement means 7 can be moved in its entirety to a position just in front of the end position, that is the extension of the reinforcement closer to the end wall 3. Just behind end wall 3, the clamping of the opposite ends of the reinforcement elements 20 can now be activated. If the reinforcement is then tensioned, head plate 5 comes to lie exactly on the desired mould length. Now, for example, the brake callipers can be activated, as a result of which the stress can then be taken off the stressing means. A mass of concrete can be poured into the mould. After hardening, the stress on the reinforcement can slowly be released by slowly deactivating the brake callipers, thus avoiding a shock to the concrete. Head plate 5 can be returned to the position in Fig. 9a and when the workpiece is lifted from the mould, the reinforcement elements come out of the slots of the combs. The pieces of reinforcement protruding from the workpiece, usually only a few centimetres, can then be sawn off.

With this embodiment, the total loss of reinforcement can be limited to approximately 8-20 cm, which is negligible, in particular in the light of a mould length of 10-20 metres or more.

Figs. 11-13 show an alternative embodiment in which the supporting frame from

Figs. 8-10 is used. In this case, a separate stressing means 50 is provided which can be coupled to the supporting frame 27. Here, the stressing means 50 is provided with a separate setting means. In an embodiment, this setting means cooperates with the setting means of the displacement means 7. The setting means of the stressing means may be a gear rack described above, or a very simple tenon-mortise joint in which, for example, the mould is provided with a series of holes in the longitudinal direction. The stressing means may, for example, be provided with a pin which is displaceable in a hole of the series of holes, so that the stressing means can be fixed in a set position. In the embodiment illustrated in the figures, the stressing means is provided with a clamping device 51 by means of which the stressing means 50 can be fixed in any desired position. The clamping device 51 of the stressing means comprises a brake calliper on both sides which, in this case, grips around the upper leg 32 of H beam 30 and is provided with a lower brake lining 52 and an upper brake lining 53, as is illustrated more clearly in Fig. 12. Stressing means 50 is furthermore provided with a coupling part 56, 56% which cooperates with coupling part 57, 57' on supporting frame 27 in order to be able to couple the stressing means 50 to supporting frame 27. Here, stressing means 50 is provided on both sides with a set of hydraulic cylinders 54, 54' and 55, 55'. These can displace coupling parts 56, 56' with respect to the rest of the stressing means 50.

This embodiment operates as follows. When the head plate 5 has reached a position in which the reinforcement has a relaxed length which is such that it fits between the end wall 3 and head plate 5, clamping device 51 is activated. Usually, the coupling parts have also already been activated. Stressing means 50 is activated by pressurizing the hydraulic cylinders. As a result thereof, supporting frame 23 is moved away from stressing means 50 and from end wall 3. The brake calliper of supporting frame 23 is not active. The reinforcement is prestressed to a set value and the distance between the end wall 3 and the head plate 5 is also brought to a desired, set distance. At that point in time, the brake callipers of supporting frame 23 are activated. These brake callipers remain activated, while the clamping device 1 of the stressing means 50 is deactivated and the pressure on the hydraulic cylinders 54, 55, 54' and 55' can be released. The stressing means 50 now moves in the direction of the end wall 3, away from the mould. Now, the concrete can be poured into the mould. The mould length can be set to the millimetre and the prestress on the reinforcement can also be accurately set and maintained.

Alternatively, in an embodiment, the reinforcement can be provided cut to length, for example by means of a feed belt. The ends of the reinforcement may be upset or may be provided with end sleeves 20, as is the case in Fig. 6. In an embodiment, the mutual distance between the reinforcement elements is fixed, for example due to the fact that the reinforcement is supplied in a holder. Head plate 5 is taken to a first position so that the mutual distance between end wall 3 and head plate 5 is suitable to accommodate the reinforcement elements in the combs 40. Similar to head plate 5, end wall 3 may be provided with the comb 40 and a tiltable wall. In order to arrange the reinforcement in the mould, for example, a set of magnetizable beams may be provided transversely to the longitudinal direction of the reinforcement. The tiltable walls 5 with slots 4 fix the reinforcement and the mould 1 can furthermore be activated as described above .

It will be clear that the above description has been given in order to illustrate the operation of preferred embodiments of the invention, and not in order to limit the scope of the invention. On the basis of the above explanation, many variations which fall within the spirit and the scope of the present invention will be obvious to a person skilled in the art.

Claims

1. Device for producing concrete elements provided with prestressed

reinforcement, such as a prestressed wide-slab floor, a solid or hollow pile, but also concrete elements containing cavities, such as a hollow pillar or hollow core slab floor, comprising a mould provided with a mould bottom, an end wall, first reinforcement holders for holding a series of reinforcement parts at one end thereof beyond a mould surface of the end wall, a head plate situated opposite the end wall and second reinforcement holders for holding the reinforcement parts at their opposite end beyond a mould surface of the head plate, wherein the mutual distance between the head plate and the end wall is adjustable from a first mutual distance to a second mutual distance by means of a displacement means and the device is furthermore provided with a setting means for fixing the mutual distance of the head plate and the end wall at intermediate distances, and the device is furthermore provided with a stressing means for prestressing the reinforcement.

2. Device according to Claim 1, wherein the setting means comprises a clamping part which engages with a stationary part of the concrete mould in a clamping or frictional manner, thus making continuous fine adjustment possible.

3. Device according to one of Claim 1 or 2, wherein the device is furthermore provided with stressing parts for displacing the second reinforcement holder.

4. Device according to Claim 3, wherein the stressing parts are placed on the displacement means and the second reinforcement holder is coupled to the stressing parts so as to be displaceable on the displacement means.

5. Device according to the preceding claim, wherein the second reinforcement holder is movably provided on the displacement means for independently stressing the reinforcement and displacing the head plate.

6. Device according to one of the preceding claims, wherein the setting means comprises first and second fixing parts, in the longitudinal direction of the mould and at a distance apart, in an embodiment, first fixing parts are configured to fix the head plate and second fixing parts are configured to fix the stressing means, in a further embodiment, at least the second fixing parts are clamping parts configured to clamp a stationary mould part, in a further embodiment, the first clamping parts are configured to clamp a stationary mould part.

7. Device according to one of the preceding claims, wherein the fixing means comprises the clamping parts which are configured to clamp a stationary mould part, wherein the stationary mould part comprises a rail on either side which extends in the longitudinal direction of the mould, and the clamping parts comprise brake shoes which are configured to engage with the rail in a clamping manner.

8. Device according to one of the preceding claims, wherein the head plate is displaceable by means of the displacement means from a first position to an end position at a greater distance from the end wall than the first position and the setting means is configured to fix the head plate at intermediate positions.

9. Device according to one of the preceding claims, wherein the displacement means is mounted on the concrete mould so as to be displaceable.

10. Device according to wherein the stressing means engages with the displacement means.

11. Device according to one of the preceding claims, wherein the bottom part, the end wall, the head plate and side walls substantially delimit a rectangular mould shape.

12. Device according to one of the preceding claims, wherein the stressing means is placed on the displacement means.

13. Device according to one of the preceding claims, wherein the head plate is connected to the displacement means by means of an adjusting means for continuously adjusting the position of the head plate with respect to the displacement means.

14. Device according to one of the preceding claims, wherein the second reinforcement holders are fixedly connected to the displacement means.

15. Device according to one of the preceding claims, wherein the head plate is displaceable along a head plate displacement line.

16. Device according to Claim 15, wherein the displacement means comprises a rail extending along the mould and parallel to the head plate displacement line, and a frame with running parts which run over the rail, wherein the head plate is connected to the frame.

17. Device according to Claim 16, furthermore provided with a drive for driving the frame for displacing the head plate.

18. Device according to one of the preceding claims, wherein the head plate can be displaced parallel to and between side walls.

19. Device according to one of the preceding claims, wherein the second reinforcement holder is displaceable with respect to the head plate.

20. Device according to the preceding claim, wherein the setting means comprises a gear rack track along at least a part of the mould along the rail and the gear rack track is provided with a first toothing, and the setting means furthermore comprises a locking part on the carriage, which locking part is provided with a second toothing, and wherein the second toothing can be brought into engagement with the first toothing.

21. Device according to Claim 20, wherein the setting means comprises a pawl which is rotatable about an axis of rotation on the carriage and is provided with the second toothing, and a wedge which is movable towards the axis of rotation and is connected to a power unit so that, when the power unit is activated, the wedge is displaced towards the axis of rotation and exerts an upward force on the pawl so that the second toothing engages with the first toothing for fixing the position of the head plate.

22. Device according to one of the preceding claims, wherein the reinforcement parts are selected from the group comprising reinforcement rods, reinforcement cables, reinforcement wires, and a combination thereof, in an embodiment, these reinforcement parts are made of steel or plastic.

23. Device according to one of the preceding claims, wherein the mould is elongate and the side walls are longitudinal walls.

24. Device according to one of the preceding claims, wherein the head plate can be moved from the end wall to a head plate end position.

25. Assembly comprising a set of moulds provided with prestressed

reinforcement for producing concrete elements, such as a prestressed wide-slab floor, a solid or hollow pile, but also concrete elements containing cavities, such as a hollow pillar or hollow core slab floor, wherein the moulds are provided with a mould bottom, an end wall, first reinforcement holders for holding a series of reinforcement parts at one end thereof beyond a mould surface of the end wall, a head plate situated opposite the end wall and second reinforcement holders for holding the reinforcement parts at their opposite end beyond a mould surface of the head plate, wherein the mutual distance between the head plate and the end wall is adjustable from a first mutual distance to a second mutual distance by means of a displacement means and the device is furthermore provided with a setting means for fixing the mutual distance of the head plate and the end wall at intermediate distances, and the assembly is furthermore provided with at least one stressing means for prestressing the reinforcement.

26. Assembly according to Claim 25, wherem a stressing means is displaceable between the moulds, or the moulds are provided with a displacement device in order to move past the stressing means.

27. Assembly according to Claim 25 or 26, wherein the stressing means comprises a fixing means for fixing the stressing means in a position on the mould, in an embodiment the fixing means comprises a clamping part which engages with a stationary part of the concrete mould in a clamping or fnctional manner, as a result of which a continuous fine adjustment of the stressing means on a mould can take place.

28. Method for producing a concrete element provided with prestressed reinforcement parts by means of a device according to one of the preceding claims, comprising the following steps:

- fixing the head plate at the setting position, and

29. Method for producing at least one concrete element provided with prestressed reinforcement, in particular according to Claim 28, comprising positioning

reinforcement elements in a mould, prestressing the reinforcement elements and introducing a concrete composition into the mould, wherein a desired mould length is determined before introducing the concrete composition, wherein the mould length is the distance between an end wall and a head plate between which the prestressed reinforcement elements extend, wherein the mutual distance of the end wall and the head plate is set to a first distance equal to the desired mould length minus the extension of the reinforcement elements at a set prestress, after which the reinforcement elements are prestressed to the set prestress with the end wall and the head plate reaching the desired mould length as a result of the extension of the reinforcement elements.

30. Method according to Claim 29, wherein, before the prestress is applied, the mutual distance is the first distance plus a detachment distance, following which the reinforcement elements are prestressed to the set prestress, and then the head plate is displaced in the direction of the end wall up to the desired mould length.

31. Concrete element comprising prestressed reinforcement parts which extend in at least one direction in the concrete element, wherein the concrete element has been produced by means of the device according to one of the preceding claims or by means of the method according to one of the preceding claims.