The present invention relates to a mould for casting a concrete element.

More specifically the invention relates to a mould used in a production line of the carousel type, in which a number of moulds circulate between different stations, including a station for casting concrete in the moulds, a station for allowing the concrete to set, a station for removing the cast elements from the mould and a station for cleaning the empty moulds .

After these stations have been passed, the empty moulds are again guided along the aforementioned first station for casting the concrete. The concrete elements obtained are further treated or processed and stored for further hardening of the concrete via a branch of the production line.

Such a type of production line is, for example, typically used for manufacturing concrete railway sleepers or other elements that are removed from the mould by turning over the mould.

Moulds are thereby used with a negative shape of the element to be obtained, that have a base and upright walls that define the circumference of the object to be cast, and which have an open top through which the concrete is poured into the mould and through which the cast element is also removed after sufficiently hardening, without the mould having to be opened.

When casting the concrete the mould is used with its open side upwards.

In order to remove the cast elements from the mould after hardening sufficiently, the moulds are turned over with their open side turned downwards.

In . some cases, the turning over of the mould alone is insufficient to let the cast element fall from the mould. In such a case, after being turned over the cast element is vibrated loose, for example, by a vibrating installation or similar.

A disadvantage of known moulds and their use in a carousel system is that the turning over of the moulds is time consuming and also takes up extra space in the production line, and also requires a relatively powerful hydraulic or other system to turn over the filled moulds, especially when a number of moulds are connected to cast a number of elements simultaneously.

Another disadvantage is that there is little control over the releasing and falling of the cast element from the mould, such that it sometimes falls out of the mould obliquely and first comes down on a point or edge or such, which can give rise to rejections due to parts breaking off.

The purpose of the present invention is to provide a solution to at least one of the . aforementioned disadvantages or other disadvantages.

To this end the invention concerns a mould of the type used in a production line of the carousel type for casting concrete elements, and this mould has a base and upright walls that define the closed profile of the element to be cast, and which has an open side through which the concrete can be poured into the mould and through which the cast element can be removed from the mould, whereby the mould also has one or more push-out elements that belong to the mould and which are at least partially movable or deformable in the direction of the open side of the mould between a retracted position, in which the push-out elements also determine the shape of the mould, in other words the shape of the concrete element to be obtained, and a pushed-out position away from the retracted position.

With such a mould it is no longer necessary to turn the mould over, as the cast element can be pushed away from the base in the direction of the open side, after which the cast element can be picked up and moved, for example by means of a vacuum gripper.

Thus a powerful installation is not needed for turning over the mould. Moreover, no extra space is needed for turning over the mould.

Another advantage is that the release of the cast element from the mould is more controlled than with the known systems, and consequently there are no, or in any respects fewer, rejections on account of parts breaking off.

This is especially the case when the push-out elements (7) form means (6) for moving the cast element (15) upwards in the mould (1) against the force of gravity, as the cast elements do not fall out of the mould.

By activating the push-out elements, either by moving them or by deforming them, the cast element -is pushed out of the mould and pushed upwards over a sufficient distance in order to be able to hold the cast element and remove it from the mould, and to move it for further treatment or storage .

According to a practical embodiment, the base of the mould is a fixed and rigid base in which the push-out element or push-out elements are integrated, for example in openings in the base that are sealed by the push-out elements when they are retracted or pulled back.

According to an embodiment, one or more push-out elements are constructed in the form of a membrane or another elastically deformable element that seals an opening in the base of the mould, and which is deformable upwards by means of a plunger or pressure under the membrane or elastically deformable element.

The invention also relates to a production line of the carousel type for manufacturing concrete elements, whereby one or more moulds according to the invention circulate past a station for filling the mould with liquid concrete and a station for removing the cast element from its mould, and whereby the production line contains no means for turning over the moulds.

In this way a more compact and simpler production line is obtained with greater operational reliability and a smaller risk of rejections with respect to production lines where the moulds have to be turned over to remove the cast elements from them.

The invention also relates to a method for casting a concrete element in a mould with a base, walls that define the profile of the element to be cast and an open side oriented upwards, such that liquid concrete is poured into the mould and the cast element, after setting, is removed from the mould via the open side by pushing the cast element out of the mould from the base, without turning the mould over.

With the intention of better showing the characteristics of the invention, a few preferred embodiments of a. mould according to the invention are described hereinafter by way of an example without any limiting nature, with reference to the accompanying drawings, wherein: figure 1 schematically shows in perspective an empty mould according to the invention for casting a railway sleeper .

figure 2 shows a cross-section according to line II-II of figure 1.

figure 3 shows the mould of figure 2 filled with concrete .

figure 4 shows the mould of figure 2 upon removal of the cast element from the mould.

figure 5 shows a cross-section as in figure 4, however for an alternative embodiment of a mould according to the invention.

figures 6 and 7 shows a cross-section, as in figures 3 and 4 respectively, for another embodiment of a mould according to the invention.

The mould 1 shown in figures 1 and 2 primarily consists of a base 2, upright walls 3 and an open side 4.

The base 2 and the walls 3 are constructed as a single unit, in which the base and walls are fastened together and define a space 5 whose shape is the negative shape of the element to be cast, and whereby the walls define the closed circumference of the element to be cast.

The mould 1 is of the type that is intended for casting concrete elements without undercuts, and for removing them out of the mould 1 via the open side 4 without it being necessary to take the mould 1 apart to this end, and which enables the cast element to be removed from the mould 1 by turning over this mould 1.

The mould 1 according to the invention has means 6 to move the cast element in the mould 1 upwards with respect to the mould 1.

In the example of figures 1 and 2, these means 6 are formed by two push-out elements 7, each in the form of a disk- shaped valve with conical edges 9 that each close off an opening 10 in the base 2 of the mould 1, whereby, as shown in figure 2, the valves 8 in this case are countersunk in the base 2 and thus are completely sunk into the opening 10.

These openings 10 are constructed as a valve seat with an edge 11 that . is conically narrower downwards, and with a conicity corresponding to that of the valve seat.

As a result, the valves 8 pass into the openings 10 in such a manner that they form a seal that prevents concrete poured into the mould from leaking away via the openings 10.

In this case the tops of the valves 8 are flush with the surface of the base 2, and in this position as it were form an integrated whole with the base 2 of the mould 1, and as it were form a movable part of the base.

The push-out elements 7 in the form of the valves 8 in the situation of figure 2 can be moved upwards over a distance in the vertical direction X-X' towards the open side 4 of the mould 1, between a sealed retracted position, as shown in figure 2, and a protruded pushed-out position away from the base 2, as shown in figure 4.

To this end the valves 8 are, for example, affixed to a vertically movable rod 13 that can be moved in a vertical guide, not shown in the drawings, whereby the valve for example is held in the retracted position by a spring or similar .

The method for casting a concrete element, in this case a concrete sleeper, and removing it from its mould is simple and is illustrated on the basis of figures 2 to 4.

Starting with an empty mould 1, as shown in figure 2, with retracted valves 8 to close off the openings 10, liquid concrete 14 is poured into the mould 1 via the open side 4 up to a desired level 15, as illustrated in figure 3.

Then after a sufficient setting period for the concrete 14, the rods 13 with the valves 8 affixed to them are moved upwards, as illustrated in figure 4, the hardened cast element 16 in the form of a sleeper is pushed off the base 2 and pushed upwards in the mould 1 with respect to the mould 1 until it is sufficiently clear to be picked up and further removed from the mould 1 or moved for further treatment or storage for further hardening. The cast elements 16 can be picked up by all suitable lifting and transport means known in the sector, for example by means of a vacuum gripper or similar.

As the cast elements 16 are pushed from the base 2 from underneath, the vacuum between the cast elements 16 and the base 2 and walls 3 is easily broken, so that it is not necessary to vibrate the element 16 loose from the mould 1, as is often required with known moulds.

When the cast element 16 has been removed from the mould, the valves 8 are retracted to close off the openings 10 again, after which the mould is again ready for the next element to be cast.

It is clear that during the entire process of casting the concrete 14, the setting and the removal of the cast element 16 from the mould 1, the mould 1 can spend the entire time with its open side 4 directed upwards and it is thus not necessary to turn the mould 1 over as is usually done .

A consequence of this is that no means for turning them over is required and that the moulds 1 have their open side 4 oriented upwards over the entire course of the production line .

Figure 5 shows a variant of a mould 1 according to the invention, which differs from the mould described above in figures 1 to 4 in the fact that the push-out elements 7 are in this case formed for each opening 10 by a membrane 17 that closes off the opening 10 concerned..

Each membrane 17 is elastically deformable upwards in the direction of the open side 14, in order to, for example by moving a rod 13, partially push the membrane 17 upwards, as shown in the dotted line in figure 5, and thus to push the cast element 16 out of the mould 1. Figure 6 shows another mould 1 according to the invention, whereby in this case the base 2 is a double base with a fixed rigid part 18 that is covered by a deformable push- out element 17 in the form of a foil or elastically deformable membrane that is secured along its edges 20 to the inside of the mould 1, and which together with the fixed base 18 of the mould defines an airtight chamber 21 that can be connected by means of a link 22 to a hydraulic or pneumatic pressure source. The use of this embodiment of the mould 1 is analogous to the embodiments described above.

When pouring the liquid concrete, the aforementioned chamber 21 is connected to the atmosphere via the link 22.

As a result of the weight of the concrete 14, the element 19 is pressed against the fixed base 18.

After sufficient hardening, the chamber 21 is placed under pressure, such that the deformable element 19 is inflated as it were in the direction of the open side 14 and the cast element 16 is pushed upwards.

Other forms of push-out elements 7 or 19 are not excluded.

Thus for example at least one push-out element can be constructed in the form of a plunger that is guided in an opening in the base of the mould where it forms a seal and can move in a direction perpendicular to the base, or the entire base 2 can move upwards as a separate part in a guide that is formed by a fixed part formed by the upright walls 3.

It is for example not excluded to provide rotatable push- out elements or other movable push-out elements.

The present invention is by no means limited to the embodiments described as an example and shown in the drawings, but a mould according to the invention can be realised in all kinds of variants, without departing from the scope of the invention.