This invention relates to a device for water treatment, more particularly a device of the type whereby the water during treatment is brought into contact with a treatment medium, such as an ion exchange resin, whereby this treatment medium is provided with a tank with two liquid- permeable holders between which the treatment medium is held.

Devices of the aforementioned type are known, amongst others, from the international patent application WO 98/04349. In the case of an embodiment as a water softener, in normal use the water in this device is directed through a quantity of resin, in such a manner that the calcium and magnesium salts are replaced by sodium salts. Hereby, the water flows from above downward through the resin and is supplied back again upwards by means of a central upward conduit. The resin is regenerated regularly by supplying brine therethrough in countercurrent.

It is known that, by pressing the treatment medium, more particularly, the resin, which mostly consists of small granules, a better efficiency is obtained, in particular in respect to an efficient utilization of the brine during regeneration, as well as in respect to water softening. Due to the pressing of the resin, it is then achieved that the liquid, either water or brine, is forced to make a better contact with the resin granules.

During sending the brine upward through the resin, the resin particles moreover can not float freely, which results in that the brine uniformly displaces the calcium and magnesium and improves the"chromatographic course".

Hereby, the pressing of the resin must be performed in such a manner that the resin can expand, shrink respecti- vely. It is well known that the volume of the resin changes depending whether it is exhausted to a major or minor degree.

It is known to realize such pressing by applying a radially expandable conduit or, for example, a rubber bellows as the central conduit, in such a manner that the surrounding resin is pressed by the liquid pressure. This technique has the disadvantage that it is rather complex and that it only fulfils its purpose when a pressure can be created in the central conduit which is higher than in the resin, thus, when supplying the brine.

The invention aims at a device which does not show the aforementioned and other disadvantages.

To this aim, the invention relates to a device of the above-mentioned type, with the characteristic that at least one of both holders is movable and that the device is provided with elastic means with which the holders are forced mutually towards each other, in such a manner that the treatment medium is pressed. By pressing the treatment medium, more particularly the resin, by means of liquid-permeable holders, a constructively simple pressing structure is obtained. By providing in a pressing by means of elastic means, a permanent pressing can be guaranteed.

It is noted that the aforementioned pressing does not have to be large. Above all, it is important to prevent that the resin granules, in particular during the countercurrent, namely, the regeneration, will float completely free and the resin bed becomes"liquid".

Preferably, one holder is mounted at a fixed location, whereas the other holder is movable and is pressed by the elastic means against the mass of resin, or possibly another treatment medium, which is held between the liquid-permeable holders.

In a preferred form of embodiment, the elastic means consist of a sealing of an elastic material which is applied between the respective holder and an adjacent constructive part, whereby this sealing is realized in such a manner that it is elastically extended in mounted position and presses the holder onto the resin or such.

More particularly, it is preferred that the elastic means consist of a membrane.

In the most preferred form of embodiment, the afore- mentioned elastic means are realized in the form of a sliding membrane. Such sliding membrane has the advantage that the direct distance between the fixation at the holder and the one to the adjacent constructive part may be small, whereas, anyhow, a good stretching is possible.

Hereby, the sliding membrane substantially is cylindrical and is fixed at one extremity at the aforementioned holder, whereas, at its other extremity, it is fixed at the aforementioned constructive part. This constructive part is preferably formed by a central guidance and/or conduit passing through the holder concerned, more particularly the conduit which, as well known, serves as a return conduit.

The tensioning of the sliding membrane preferably is performed by means of a pressing part, more particularly a cylindrical pressing part, which is slid between the constructive part concerned and the aforementioned

holder.

Preferably, the sliding membrane provides for a sealing between the holder and the aforementioned constructive part, which is realized such that this sealing extends continuously over the entire or almost the entire length of the sliding membrane, and/or at least such that no spaces are formed in which, with a flow in one or the other direction, liquid may come to a standstill which shall only be rinsed away when the flow direction is reversed. As a result thereof, it is obtained that no brine remainders can form in the sealing, with the important additional advantage that all brine is utilized for the regeneration and that after regeneration and taking the device into service again, no brine remainders will get into the water taken by the user.

With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, several preferred forms of embodi- ment are described, with reference to the accompanying drawings, wherein : figure 1 partially in cross-section represents a device according to the invention ; figure 2 at a larger scale represents the part represented by F2 in figure 1 ; figure 3 at a still larger scale represents the part represented by F3 in figure 2 ; figure 4 represents a cross-section according to line IV-IV in figure 3 ; figures 5 and 6 schematically represent two variants of the part illustrated in figure 2.

As represented in figure 1, the invention relates to a device 1 for water treatment, of the type whereby the

water during treatment is brought into contact with a treatment medium 2, in this case a quantity of resin.

As known, during treatment, the water hereby is directed throught the treatment medium 2, as indicated by arrow A, whereby, due to the contact with the treatment medium 2, the calcium and the magnesium present in the water are replaced by sodium, whereas the calcium and the magnesium remain at the treatment medium 2.

The treatment medium 2 is regenerated regularly by directing a regeneration medium, such as brine, in countercurrent, such as indicated by arrow B, through the treatment medium 2, mostly followed by a a slow rinsing.

This brine is supplied in a known manner from a not- represented brine barrel, and the product discharged during regeneration is drained by means of a connection to the sewage system or the like.

Hereby, the regeneration is controlled automatically by means of a regulator 3 which is provided with the necessary valves. In consideration of the fact that, on one hand, the control of the device 1, as well as the construction of such regulators is sufficiently known from the state of the art, amongst others, from the aforementioned international patent application WO 98/04349, and, on the other hand, the invention relates to the pressing of the treatment medium 2, the aforementioned control by means of the regulator 3 will not be discussed in further detail.

The treatment medium 2 is provided in a tank 4 and is held between two liquid-permeable holders 5 and 6 situated one above the other. The lowermost holder 5 hereby is supported on a collar 7, in such a manner that a space 8 is formed thereunder which is free of treatment

medium 2.

Centrally in the tank 4, a conduit 9 standing upright is provided which functions as a return conduit and which at the bottom gives out to the space 8. At the top, the conduit 9 communicates with a passage 10 through which the water to be treated is discharged, the brine or such is supplied, respectively.

Above the uppermost holder 6, also a free space 11 is present which is connected to the regulator 3 by means of one or more passages 12.

The particularity of the invention consists in that, as represented in the figures 1 to 4, at least one of both holders, in this case the uppermost holder 6, is movable and that the device 1 is provided with elastic means, in this case a sliding membrane 13, with which the holders mutually are forced towards each other, more particular- ly, the holder 6 is forced downward, in such a manner that the treatment medium 2 is pressed.

Hereby, the holder 6 is realized in the form of a disk which can be moved up and down around the circuit 9, and substantially consists of a frame 14 in which a liquid- permeable mebrane 15 or such is provided. At the exterior edge, the holder 6 is provided with a sealing 16 made of a relatively soft synthetic material or similar, with which the holder 6 can be shifted alongside the interior edge 17 of the tank 4.

The aforementioned sliding membrane 13 is provided between the interior edge of the frame 14 and the conduit 9 and in this manner fulfils a double function, namely, on one hand, the provision of the aforementioned pressing force and, on the other hand, the provision of the

sealing around the conduit 9.

The sliding membrane 13 is expanded by means of a cylindrical pressing part 18 provided between the conduit 9 and the holder 6. This pressing part 18 is held at its place against the force of the sliding membrane 13, in that it is mounted against the underside of the cover 19 of the tank 4.

At the same time, the pressing part 18 fulfils the function of connection piece between the upper extremity of the conduit 9 and the passage 10. Thus, it is composed of a conical part 20 forming a partition between the passage 10 and the space 11, and a cylindrical part 21 which takes place concentrically around a pipe-shaped part 22 forming part of the conduit 9.

In order to keep the sliding membrane 13 at its place, it is, at both extremities, provided with a fixation collar, 23 and 24, respectively, of which the fixation collar 23 engages behind the edge 25 of the pipe-shaped part 22, whereas the fixation collar 24 engages behind the interior edge 26 of the holder 6.

In mounted position, the sliding membrane 13 extends around the cylindrical part 21 of the pressing part 18 and preferably provides for a sealing between the adjacent parts. The sliding membrane 13 extends downward between its free extremities, and the closure preferably is realized at the location of the extremities, thus, situated on top. As a result thereof, it is obtained that between these parts, there is no space present into which brine remainders or such from above may penetrate and remain there. As indicated by arrows C in figure 3, the brine obviously can not penetrate between the pipe-shaped part 22 and the cylindrical part 21.

It is noted that the sealing preferably is improved by directing the edges of the sliding membrane 13 at the locations X and Y somewhat towards the inside. Moreover, then a pressure force is realized exclusively locally, whereas the sliding membrane 13 is clamped little or not between X and Y, as a result of which it easily can be stretched.

It is obvious that liquid which possibly enters from below between, on one hand, the sliding membrane 13 and, on the other hand, the conduit 9 and/or the holder 6, from below, can drain off downward.

The functioning of the device 1 can simply be deduced from the figures.

During assembling, first the holder 5, together with the pipe-shaped part 22 is mounted in the tank. Subsequently, the treatment medium 2 is brought into the space around the pipe-shaped part 22, after which the holder 6, together with the sliding membrane 13, is mounted. In not-expanded condition, the sliding membrane 13, for example, takes up a position as indicated by dashed line 27 in figure 3. By subsequently sliding the pressing part 18 between the sliding membrane 13 and pressing it by mounting the cover 19 onto the tank 4, the condition illustrated in figure 3 is obtained, whereby the holder 6, due to the tension force in the sliding membrane 13, is pressed with a certain force F onto the treatment medium 2.

The elasticity of the sliding membrane 13 provides for that a pressing of the treatment medium 2 takes place permanently, even if during the use, the regeneration, respectively, of the device 1, the volume of the treatment medium 2 changes and the holder 6 moves

somewhat up or down. When the sliding membrane 13 is stretched more or less, it slides around the lower edge of the pressing part 18, as a result of which the latter performs a stretching and sliding movement. It is obvious that the lower edge of the pressing part 18 preferably is rounded.

It is obvious that different variants are possible. So, for example, the pressure part 18 must not necessarily be realized as a connection part. Also, this pressing part not necessarily has to come into contact with the cover 19 and can be fixed at its place in another manner.

According to another possibility, use can be made of a large sliding membrane which is not situated in the proximity of the interior edge of the frame 14, but is provided along the exterior periphery of the frame 14.

As represented schematically in figure 5, it is also possible to use elastic sealings 28-29, at the interior periphery as well as at the exterior periphery of the frame 14 of the holder 6.

According to still another possibility, as represented schematically in figure 6, use can be made of a classical spring, more particularly a compression spring 30 for pressing the holder 6 onto the treatment medium 2.

Although in the given examples only one of the holders is movable and is pressed by means of elastic means, it is obvious that according to a variant, also both of the holders 5-6 might be movable.

The lowermost holder 5 does not necessarily have to be realized in the shape of a disk and may consist of any element which prevents the treatment medium 2 from

getting into the conduit 9.

In a deviating form of embodiment, the sliding membrane 13 will not provide any pressing force for the treatment medium 2, but will exclusively provide for a sealing between the pipe-shaped part 22 and the cylindrical part 21, and possibly between the cylindrical part 21 and the frame 14. In this form of embodiment, the sliding membrane 13, for example, can be provided with a collar 31 instead of the aforementioned fixation collar 24, as schematically indicated in figure 3, which collar 31 engages in a recess in the exterior periphery of the cylindrical part 21. In such case, the pressing force can be provided by other elastic means.

It is noted that the closure by means of such sliding membrane 13 is also advantageous in forms of embodiment whereby no pressing of the treatment medium 2 is perfor- med, as then the advantage still is maintained that between the pressing part 18 functioning as a connection part and the conduit 9 no spaces are formed in which brine remainders can accumulate. It is obvious that the present invention also relates to such forms of embodiment.

The present invention is in no way limited to the forms of embodiment described as an example and represented in the figures, on the contrary may such device for water treatment be manufactured in different forms and dimen- sions and can also be applied in other treatment devices than water softeners, whereby the treatment medium not necessarily is a resin. The invention also can be applied in devices where the regeneration takes place with a product other than brine, or whereby even no regeneration at all takes place.