State of the Art Systems known at present are mainly static systems, i. e. systems without mobile parts that use as a principal element a surface that is covered by a grid with openings, or a column of successive circular disks made of a hard material with small channels engraved onto their surfaces. The openings of the grid or the cross sections of the small channels in the disks characterise the maximum dimension of the grains of foreign solid particles that may pass through the filter and, hence, the quality of filtering.

The disadvantages of existing systems concern their difficulty of cleaning. The grid or the disks must be removed from the main body and washed out in a strong water stream so that foreign matter that remains trapped in the openings of the grid or into the small channels of the hard disks are removed.

As modern technology applications of filters require the ability of automatic cleaning, the problems associated with the existing systems are multiplied.

A usual manner for automatic cleaning of existing systems requires the diagnosis of the need for cleaning first.

For this reason, sensors are available that measure and calculate the pressure difference in the spaces before cleaning and after cleaning of the liquid. If the pressure difference is found to exceed a predetermined magnitude, then the command for cleaning to start is automatically generated by a computer.

These phases consist of : a) the interruption of the operation of the filter

b) The inversion of the flow of water c) The gradual selective direction of all the quantity of water to all sectors of the surface of the grid or the disks until this inverse flow leads to the removal of all foreign bodies trapped in it. d) The simultaneous removal of all the quantity of wash water along with the trapped foreign matter particles It is obvious that the automatic system for diagnosing the need for washing and cleaning a filter, as required by the new conditions, requires expensive additional arrangements that lead to the four-fold or five-fold increase of the filter cost.

Brief Description of the Invention This invention relates to the construction of a new filter which has the ability of self-cleaning of its elements from trapped foreign material. The removal of the foreign material is effected by mechanical scrubbing, the principal element of the filter consists of a column of successive hard and soft rings.

The hard rings are placed in a column, one on top of the other, leaving void spaces between them at a steady distance.

These void spaces are covered by an equal number of flexible elastic rings of an open Y shaped cross section that alternate between two discrete positions, that of compression and that of decompression.

The alternation of these positions is effected at each intensive pressure change of water in the network before the filter, and hence when operation starts or is interrupted. The elastic rings bear small shallow channels engraved at their convex surface, radially arranged for filtering the water.

When the supply network is under no pressure or when the filter does not operate, the elastic rings are at the decompression position. When pressure is increased above some predetermined level, the operation of the filter starts and the elastic rings return to the second discrete position, the compression position.

Water is filtered during the compulsory passage between the void spaces formed between the successive rigid fixed rings and the elastic rings and in particular between the flat surface of the fixed ring and the convex surface of the elastic ring.

During this passage, the water is subject to a pressure drop resulting in a continuous difference of pressure between the concave and the convex surface of the elastic circumferential ring of the disk.

Thus, the elastic ring enters deep into the inner part of the void space of the fixed disks and is also pressed with its convex parts onto the flat surfaces of the fixed disks forming thin filtering surfaces.

Scrubbing of foreign material is effected with the relative movement of the fixed and elastic successive rings. Relative movement exists, and hence scrubbing.

Both when the system passes from the compression to the decompression stage and vice versa.

The difference lies in : A. In the first case, the small harmless particles of foreign material that have penetrated the small channels of the elastic rings are scrubbed and transferred to the clean water network, whereas with the same movement, the larger and hence more dangerous foreign matter particles that coagulate at the filter inlet are removed in the opposite direction, in the region of unclean water.

B. In the second case, when decompression is followed by compression, the small harmless particles of foreign material that have penetrated the small channels of the elastic rings and that have not been removed to the clean water region as in the previous case, are scrubbed again in the opposite direction and are thrown to the region of water that has not been cleaned.

In other variations, the solid particles of foreign mater, both in the first as well as in the second case, are scrubbed and transferred only to the region of water that has not been cleaned yet.

Description of the Drawings Dr. 1 Cross section of a flexible elastic ring Dr. 2 Part of the plan view of the elastic ring of Drawing 1 Dr. 3 Cross section of a rigid flat ring Dr. 4 Part of the plan view of the rigid ring of Drawing 3.

Dr. 5 Cross section of a basic assembled filter element consisting of the successive fixed and elastic rings during the decompression phase Dr. 6 Detail of the concave part of the elastic ring of Drawing 1, during the decompression phase Dr. 7 The same detail of the concave part of Drawing 6 during the compression phase Dr. 7a Detail of the convex part of the elastic ring of Drawing 6 during the compression phase Dr. 8, 9, 10 Different forms and arrangements of small channels for water passage and filtering at the circumference of the elastic rings Dr. 11 Detail of the cross section of the basic elastic element and the small channels of Drawing 10 during the decompression phase Dr. 12 The same detail of the cross section of drawing 11 during the compression phase Dr. 13 Part of the plan view of a rigid flat ring with wave-like interrupted terminal reception Dr. 14 Part of the plan view of a flexible ring with small filtering channels but without small channels for contraction Dr. 15 Plan view of the elastic ring and part of the rigid ring of the variation with the wavelike interrupted reception during the compression phase Dr. 16, 17 Variations where no intensive relative movement exists Dr 18 Variation with two flexible rings in series Dr 19, 20 Variation where instead of compression, drawing (pull-out tension) is exerted Dr. 21 Variation in the decompression phase where open flexible linear channels -elements exist, inserted into the flexible rings Dr. 22 Detail of Drawings 24, 25 where the system for rotation of the case slightly lifts the case, short-circuiting the spaces of clean and unclean water Dr. 23 Variation of a complete filter with wave-like rigid rings Dr. 24 Cross section of a complete filter of the present invention with a rotating case Dr. 25 Plan view of the filter of Drawing 24 Dr. 26 Variation of an elastic ring in the decompression position with ability of relative rotation of the two parts that constitute its open circumferential channel Dr. 27 Start-up of operation of the filter of Drawing 26 with the rotation of the two parts of the channel of the ring Dr. 28 Compression phase of the elastic ring of Drawing 26 Dr. 29 Plan view of the rigid ring of Drawing 26 Dr. 30, 31 Variation where both the elastic as well as the fixed channels are connected together into integral units that slide into each other Dr. 32 Variation with vertical fixed and continuous elastic channels of a wavelike form Dr. 33 Details of drawing 32 Dr. 34, 35 Variation with perforated rigid rings and open rings of almost a semi- circular cross section Dr. 36, 37 Variation of Dr. 5 where the elastic ring bears two additional circumferential rims Dr. 38, 39 Variation where instead of the thin rims of Drawings 36, 37, holes exist with thin protruding craters Dr. 40, 41 Variation of Dr. 36, 37 where between the rims, a fixed disk interferes Dr. 42, 43 Variation of Drawing 5 where the spacer cylinders are elastic and located on top of the elastic ring Dr. 44, 45 Details of the behaviour of the elastic channels of drawing 24 and 25 during the washing process Dr. 46 Detail of the telescopic cleaning channel of Drawing 24, 25 with the elastic high-speed slot with automatic adaptation.

Dr. 47 Cross section of the part of the filter where instead of the case, the cleaning channel is rotated with the slot for high speed water outlet Dr. 47a Cross section of Drawing 47 Dr. 48 Cross section of the case with simple cups in three positions of the operation cycle (a, b, c) Dr. 49 Views of space A, of the end of the circumferential case of the cup of Drawing 48 with the edges in the three positions a, b, c.

Dr. 50 Plan view of two successive cups of Dr. 48 Dr. 51 Plan view of a cup with triangular incisions at positions (a) and (b)

Detailed description of the drawings Drawings 1, 2, 6, 7, 7a illustrate the elastic ring 1, the principal element of the filter. It is a closed Y shaped ring that bears at its upper and lower convex surface of the open channel 15, a large number of radial small channels 2, inside which the water is filtered.

Apart form the small channels 2 for filtering water, it also bears a smaller number of deeper channels 3 and 3a on the convex and the concave surface of the Y shape, respectively. Channels 3 and 3a will be used for the contraction of the circumference of the ring, as will be seen in the sequel.

Drawing 8, 9, 10 illustrate various forms and arrangements of small channels for the passage, distribution and filtering of water on the convex surface of the elastic ring 1.

Drawings 3 and 4 illustrate the second element of the filter, the rigid flat closed fixed ring 4. The ring 4 bears two edges 5 at its upper and lower external surfaces, whereas it bears the flat surfaces 17 and the terminal concave interrupted surfaces 6 towards its inner part, that correspond to the convex surfaces 7 of the elastic ring 1. In its inner part, the ring 4 bears the spacer cylinders 8 with the respective protrusions 10 and the support receptions 9 that are used for the assembly of the fixed rings 4 to the cylindrical body (case) of successive rings with a fixed void space. The ring 4 also bears at the upper and lower part of its flat surfaces a small number of protrusions 11 the height of which does not exceed the overall height of the ring, defined by the flat surfaces of the spacer cylinders 8.

Drawing 5 illustrates a fully assembled element of the filter during the decompression stage (filter off operation). During the start up of the operation, water from space A of unclean water tends to enter initially into the space B between the rigid rings and then into space C of clean water, passing through the void spaces formed between the successive fixed 4 and elastic 1 rings.

In particular, water in its effort passes initially between the peripheral edges 5 and the convex surfaces of the elastic rings 1. The pressure difference developed between the spaces A and B causes a displacement of all the elastic ring 1 into space B and in particular until it reaches the terminal concave interrupted surfaces 6 of the disk 4 with a simultaneous contraction of the flat ring-like surface 19a of the ring 1.

This contraction of the circumference of the channel of the ring is absorbed by the coiling of the small channels 3 and 3a, whereas at the same time, the flat surface 19a of ring 1 is also radially coiled.

The broken line illustrates the new position of the ring 1 which corresponds to the operating position of the filter. In this operating position, the convex surface 7 of the ring 1 is intensively compressed, both relative to the flat (17), as well as to the convex 6 surface of the ring 4, resulting in the deformation of the height of the edges 12 of the small filtering channels 2 with simultaneous reduction of the free cross section for the passage of water inside the small channels 2, Drawing 11 and Drawing 12.

The broken line in Drawing 12 illustrates the small channels 2 in a non- compressed form.

This, during the decompression (non-operating) phase results in the automatic detachment of the suspended foreign materials from the walls of the small channel 2 ; they remain suspended into the small channel and are easily removed during the phase of self-cleaning and scrubbing. When the operation of the filter is interrupted, the pressure drop falls below a predetermined level, the elastic rings 1 return to their initial position pushed by the tension for decompression of the small channels 3, 3a and the flat surfaces 19a of the rings 1.

During this return phase, there is an intensive relative movement and friction between the flat surface 17 and the edge 5 of the rigid disk 4 on one hand, and the convex surface 7 with the small channels 2, on the other hand. Drawing 11 and Drawing 12 illustrate the relative positions of the rings 1 and 4 in the compression

and decompression positions. The small channels 2 are in this case circumferential and correspond to the arrangement of drawings 9 and 10.

It is evident that during their return to the decompression position, the relatively large sized foreign bodies 13a that coagulate in the circumference of the channel 15 of the flexible ring 1, without-due to their size-being able to penetrate inside the small channels 2, are scrubbed and fall into space A (unclean water), whereas part of the very small and harmless bodies 13 located into the small channels 2 are transported to the spaces B and C of clean water. As long as these small and harmless foreign material 13 of the small channels 2 are not transferred to the clean water network, they remain suspended and detached inside the small channels 2. These foreign bodies will be again scrubbed and will fall into the unclean water space A during the next start-up of operation of the filter, as the increase of the water pressure in space A will bring the ring 1 back to the compression position.

The removal and fall-off of the remaining foreign bodies will occur due to the relative movement again of the convex surface 7 with the edge 5, through in the reverse direction.

The part of the harmless small foreign material 13 transported to the spaces B and C is passed without a problem to the clean water network. Their other part falls- off again along with the relatively large foreign material into the space of unclean water A, is removed to the drain with the periodic automatic or semi-automatic opening for a small time period of a cleaning tap located at the body of the filter at the bottom of space A.

The filter should also be additionally cleaned with the known method, i. e. the interruption of its operation and by passing water in the reverse direction, i. e. from spaces B and C towards space A with a simultaneous opening of the cleaning tap. In the sequel, we will examine a variation where the circumference and all the open channel with the concave surface 15 of the elastic ring 1 is not contracted but takes a wavelike form of a similar length during the compression.

Drawing 13 illustrates a rigid ring of this variation where the terminal concave and broken reception surface 6a for the concave part 7 of the elastic ring 1 is not created by the simple rotation of a curved line but is a wave-like surface that has the same length with the convex part 7.

Drawing 14 illustrates a plan view of a part of the respective elastic ring 1 of the same variation as drawing 13. It is evident that the convex surface only bears small filtering channels 2 without the respective small channels 3 and 3a that receive the contractions of the channel 15.

The principal operation described in Drawing 5 also holds for this variation, with the difference that the filter during operation start-up is tight. Thus, there is no communication between the spaces A and B, C, as the intense small contraction channels 3a do not exist and the small filtering channels 2 are initially located inside the space A, outside the rings 4 and away from the edge 5. During operation start-up and as water is passed to the space A, the elastic ring 1 is radially compressed by the pressure exerted unilaterally onto the concave surface of the open channel 15 and is displaced towards the edge 5.

The inlet of water into spaces B and C and the start-up of the operation occurs when a predetermined pressure is achieved in space A, the flat surface 19a is radially compressed and the internal ends of the small radial filtering channels 2 exceed the edge 5.

With the further increase of the pressure of water into the space A, the same phenomena already described are repeated, with the difference in comparison to Drawing 15, being that the circumference of the ring 1 that consists of the open circumferential channel with the convex surface 15, instead of being contracted reducing its length, maintains the same length but follows a wavelike deformation corresponding to the new narrow terminal wave-like interrupted reception 6a of the rigid ring 4 of Drawing 13.

Thus, the lengths of the circumferences of the open channel 15 of the elastic ring remain almost equal both during the compression phase as well as the decompression phase.

In this manner, internal tensions of the elastic ring 1 during compression are minimised and easier passing to the decompression phase and vice versa is achieved.

In another variation, the edge 5 of the ring 4 may be absent. In another variation, small filtering channels 2 may exist only in the flat surfaces of the rigid ring 4, in which case scrubbing occurs by the flexible ring or small channels may exist both in the elastic rings 1 as well as the rigid rings 4.

Drawing 16 illustrates a cross section of a variation in the operating position where no relative movement exists, nor a difference between the compression and decompression positions. The elastic rings 77 are continuously in touch with each other, filtering is performed at points 76 between the rigid and the elastic ring, as weil as the contact points 75 between the two elastic rings. Washing out and cleaning is effected with the reverse movement of the water.

Drawing 17 illustrates a variation similar to that of Drawing 15 where again no relative movement exists, the elastic rings 78 do not touch each other and are promoted inside the void spaces of the rigid disks and washing is again effected with the reverse movement of water. Relative movement can be caused here during the washing, in which case the elastic rings due to the pressure differences created are slightly removed towards space A.

Drawing 18 illustrates another variation where two flexible rings exist in series (la, lb) with two corresponding terminal interrupted concave surfaces, as receptions, into the rigid disk. The holes 18 in the rigid disk are used for the removal of foreign bodies. Full relative movement exists, as in the principal invention. In another variation, the same elastic disk could bear the two concave and the two convex circumferential parts la and lb (not drawn).

Drawing 19 and 20 illustrate a variation where instead of compression, pulling occurs. The difference from the principal variation of drawing 5 is caused by the fact that during this operation, the external radial elastic protrusions 19 of the elastic ring ic are pulled, which during the interruption of the operation contract and return the ring to its initial position.

It is self-evident that all variations can perform equally effectively if the roles of the spaces A and C are reverted and the supply with water and normal operation of the filter is effected from inside the element-cage, i. e. from space C towards space A in the direction where reverse washing was performed. In this case, the convex open channel 15 should be reverted and turned towards the inner part of the cylindrical case-element (not drawn).

In another variation, instead of successive independent elastic and rigid disks, two continuous helical coils could exist, one with the rigid and one for the elastic rings, assembled one inside the other (not drawn).

Drawing 21 illustrates a variation where instead of the elastic rings 1, open elastic rectilinear channels 20 exist, fitted along the generation line of the cylindrical case of the filter and instead of flat rings 4, the flat surfaces 21 exist along the length of the cylindrical case. Despite of the different arrangement and the different shape of the channels, the operation of the filter is similar to that already described. No contraction occurs.

Drawing 23 illustrates a variation of a filter case where the elastic rings 1 are flat, whereas the rigid disks 79 are somehow wavelike, along their height.. During the operation of the filter, the elastic rings are adapted and follow the wavelike surface of the rigid ones, in a manner so that despite their compression, the external circumference of the open channel 15 has the same length, both at the interruption as well as the operation phase.

Drawings 22, 24, 25 and drawings 44-46 illustrate a complete filter of the present invention with a schematic representation of the system for automatic rotation of the case 22, during the washing process.

The case, apart from the known elastic and rigid rings, also bears its rotation axis 23, to which it is solidly connected.

The main body 65 bears the water inlet and outlet ducts 67 and 35, as well as the cylinder 68 with the edge 69 that supports the case 22. The outlet duct 35 is promoted to the cylinder 68. The cleaning channel 71 bears a vertical slot 72 located almost into contact along its length with the rotating case 22. The water turbine 37 with the guiding blades 74 and the cover 73 is located onto the body 65. Between the covers 36 and 73, the tight diaphragm 81 interferes with the holes 82 for the passage of the shaft 23 and 80 for the inlet of water into the space D of the water turbine 37.

The space D is separated from the outlet space E with the diaphragm 83. The system, of water swirl-case is pressed by the spring 70 so that the latter remains onto the edge 69 of the cylinder 68 of the body 65 and so that it separates and tightness the spaces A and C.

In the operation phase water enters trough the duct 67 and comes off the duct 35. The cleaning duct 14 remains closed.

During the cleaning phase, the outlet duct 35 closes and the duct 14 opens. As the only communication of the duct 14 with the inner part of the filter is the thin slot 72, the water develops high speed in this region and through the hole 80 of the tight diaphragm 81 enters into the space D of the water swirl 37. From there, passing through the guide blades 74 and the water swirl 37, it enters into the outlet space E and the escape duct 14. In parallel to the rotation of the water swirl-case-shaft system, the pressure differences in the spaces D and E lift the rotating system and form the void space xl2, drawing 22, between the case and the edge 69, that short- circuits and connects the spaces A and C together. This permits washing out of the case with two currents simultaneously. Both directly from space A and indirectly from

space C (reverse flow). Simultaneously, intense pressure difference develops in the region of the slot 72, i. e. the spaces A and C between the internal and the external part of the case 22, with a result that the circumferential channels of the elastic rings 1 to be bent and elongated and leave locally a larger void space between the circumferential channel and the fixed ring 4 (x7 > x5 and x10 > x9), drawing 44 and drawing 45. Drawing 44 illustrates the operation phase and drawing 45 illustrates the cleaning phase. Thus, foreign materials are further freed and under an intensive water current, they flow through the slot 72, as known, towards the outlet channel 14.

Drawing 46 illustrates a detail of the slot 72 of the channel 71. The slot 72 bears rims from elastic material, bent towards the inner part of the channel 71, with a void space between them and almost in contact to each other. The pre-tension of the elastic material does not leave the rims to open extensively so that the void space of the slot 72 increases and the water speeds to be reduced, but presses them together so that their opening is proportional to the reduced pressure developed.

Thus, we can use a minimum water supply for cleaning, without reducing the water speed in the slot 72. A foreign body, though that may due to its size fail to pass through the thin and very narrow slot 72, opens locally and momentarily the slot, due to the pressure difference that develops locally, due to its presence in the region and is removed through the duct 14 by the filter. With the removal of the body, the slot returns to its prior dimension.

Apart from all the above, the filter is also cleaned continuously externally from foreign bodies due to the intensive relative movement caused during the rotation of the case 22 into the water. The rotation of the case, for the continuous as well as the interrupted (during the washing phase) is valid not only for the case of the present invention, but for any type of filter. Simultaneously to the rotation, the detachment of foreign bodies could be assisted by the continuous contact with a specially shaped fixed brush attached inside the cover 36 of the filter (not drawn). Drawings 47, 47av illustrate a variation similar to that of drawings 24, 25 with the only difference that

instead of the case 22, the channel 84 with the slot 85 rotates along with the water turbine 37. The new system of rotation again raises without rotating the case 22. Of course, in this variation the positions of the spaces A and C are reverted. The space of the unclean water, space A is now inside the case 22. It is understood that the elastic rings 1 are inverted with the concave part 15 towards the inner part of the case. Both in the variations of drawings 24, 25 as well as of drawings 47, 47a, the short-circuiting of the spaces A and C and the achievement of inversion of flow during cleaning, is achieved by the automatic opening of some valve or hole (not drawn).

Drawings 26, 27, 28 and 29 illustrate a new variation where the elastic ring 1 consists of three discrete parts : The flat part 30 that is subject to the principal radial contraction and the two symmetrical parts above and below the flat part 30 that constitute the open circumferential channel 15.

In each of these two symmetrical parts, the part 28 is distinguished with the filtering channels and the part 27 for the rotation and exertion of large vertical forces onto the rigid filtering surface of the ring 4. The two symmetrical parts 27, 28 are connected together with a thin stripe which permits their rotation. Respectively, the part 27 is connected to the flat part 30 via an also thin articulation 26 that permits the partial rotation of the part 27 relative to the part 30.

In the position of complete decompression, drawing 26, the convex surfaces of successive rings 1 are adjacent to each other along the external narrow circumferential stripe 29 of the convex surface.

The filter is initially tight as no small channels 2 exist in the narrow stripe 29.

As soon as the water pressure in space A reaches a predetermined level, the rotation of part 27 starts around the articulation 26. Simultaneously, the part 28 is bent relative to part 27 and touches the flat surface 32 of the rigid ring 4, whereas

the terminal surface 31 of the part 27 touches the flat surface 30 and all the part 27 assumes a position vertical to the flat surfaces of the rings 1 and 4.

In this position the part 27 is subject to a slight contraction and its surface becomes convex.

In this phase of simple rotation, Drawing 27, scrubbing by the edge 5 is also effected along with a fall-off of foreign materials that may exist onto the convex surface of the part 28, into the space A.

Water now passes through the convex surface of part 28 and the flat surface 32 of the rigid ring 4. The reduced pressure developed between the spaces A and C pushes all the system of the elastic ring 1 towards space C, contracting radially the flat part 30 of the same ring, until the part 27 meets the broken terminal reception 33 of the fixed ring 4. The operation of the filter has already started. It is known that in this position, with the part 27 almost vertical onto surface 32, disproportionately large forces are exerted vertically onto the filtering surface 32, ensuring a fixed void space for water to pass, independent of the pressure differences in the network and the pressure difference in spaces A and B, C. The circumferential ring with the void spaces 18, facilitates along with the edge 15 the scrubbing of foreign bodies.

However, as soon as the operation of the filter is interrupted, the reverse movement starts, in the following sequence : a. complete decompression and return of the flat part 30 of the ring 1, until the convex surface of the part 28 passes into the space A, further than the edge 5 of the rigid ring. In this phase, scrubbing and removal of foreign bodies occurs due to the intense friction both with surface 32 as well as the edge 5. These bodies fall off into the space A. b. Free reverse rotation around the articulation 26 and return of the part 27 to its initial position

c. Contact between the elastic rings 1 along the narrow stripe 29 and tightening of the filter, drawing 26.

As throughout the duration of the return to the decompression position, the part 27 remains almost vertical to the filtering surface 32, the friction and foreign matter scrubbing forces are disproportionately high compared to the weak radial forces that cause them. In parallel, these forces are constant and independent of the variations of the pressure of water or the pressure differences in the spaces A, B and C.

For all these, it is evident that the last variation would be equally effective if the small channels only existed in surface 32 of the rigid ring 4 or even in both the rigid and the elastic ring.

Drawings 30 and 31 illustrate a relative variation to that of drawing 21, where the elastic channels 20a are connected together to the common box 38.

Correspondingly, the fixed channels 21a are also rigidly connected together and constitute the integral unit 39.

The box 38 reciprocates into the box 39 during the filtering operation, compressing the springs 40. Water is filtered as exactly in drawings 5 and 21 and passes finally through the void openings 18 located to the bottom 39 and consequently of the case of the filter. During the interruption of the operation, the springs 40 return the box 38 and along with it the elastic channels 20 to its initial position. With this variation we ensure longer paths, necessary for the development of a long length small channel and more intensive relative movement between the fixed and the mobile parts of the filter.

The box 38 of the flexible channels and the integral unit of the fixed channels 39, along with the compression springs 40, constitute an element of the case of the filter. Several such similar elements placed along a circumference so that the vertical side 41 of each element is part of the circumference of the

Circle, whereas one element touches the other almost along the length of the vertical sides 42, constitute a cylindrical case (not drawn).

In another variation, the fixed rings could be absent altogether and filtering could be performed between the convex surfaces of the elastic rings. In this case, washing of the case will be performed with reverse flow of water, as both relative movement and scrubbing are absent.

Drawings 32, 33 illustrate another variation with vertical fixed channels 47 and continuous elastic channels 48, all in a wave-like form. The fixed channels 47 are perforated for the free passing of water, whereas the continuous elastic channels 48 bear a large number of parallel and vertical broken slots. 49.

The broken lines of the drawings illustrate the elastic channels 48 during the cleaning phase or at the start-up of the operation of the filter. It is characteristic that the convex surfaces of the elastic channels 48 are turned towards the direction of water inlet to the case, i. e. towards space A.

Drawing 33 illustrates the details of the vertical interrupted slots 49 with their two rims 45 and 46-internal and external, onto the surfaces 43 and 44, internal and external, respectively.

During the operation phase, the external rim 45 is more narrow than the internal rim 46, something that benefits filtering and maintenance of the slot 49 internally clean. With the interruption of the flow of water, the elastic channels 48 return due to the internal tensions of the material to the cleaning phase and the complete reversal (broken lines), indeed ejecting the foreign bodies form the case.

During the cleaning phase, with respect to the openings of the slots 49, the opposite occurs : The rim 46 is almost closed, whereas the rim 45 is totally open, something that facilitates washing and removal of foreign bodies. For this reason, during operation start-up and as water pressure is exerted, a large pressure drop occurs between the external and the internal side of the

channels 48, so that complete reversal of the curvature of the elastic channels is achieved.

In another variation the elastic channels 48 could be independent, rather than continuous. Their connection with the fixed channels could be effected with an articulation (not drawn) in order that their reversal could be easily achieved.

In all variations of drawings 32 and 33, the reverse movement of water during the cleaning assists the internal elastic tensions for the reversal of the curvature of the elastic channels.

In another variation of drawings 32-22, instead of the vertical slots, simple holes or parallel horizontal circumferential slots vertical to the axis of rotation of the case could exist (not drawn).

Drawing 34 illustrates another variation of drawings 32, 33 where the fixed vertical channels 47 are the fixed rings 50, perforated and placed one on top of the other in a vertical column, with their concave part in the direction of water inlet, whereas the elastic bodies 48 are the continuous respective elastic rings 51 with a cross section which is almost semi-circular and with the convex part in the cleaning or operation start-up phase, towards the unclean water space A. The elastic rings bear circumferential interrupted parallel slots 52, through which water is filtered. Drawing 35 illustrates a detail of the slots 52 of the filter. Complete correspondence exists with respect to operational matters with the variations of drawings 32 and 33, whereas the broken lines of the drawings exhibit the form of the elastic rings and the slots during the start-up or washing-out phase. Of course, during the washing-out phase, the elastic rings 51 return to their original position with complete reversal of their curvature. The return is due to the internal tensions of the elastic body and is assisted by the pressure differences of water. In another variation, the interrupted slots are vertical and parallel to the axis of the case, or simultaneously, both vertical and circumferential slots may exist.

Furthermore, elastic rings 51 should be independent of each other and not constitute an integral body.

It is self-evident that all slots mentioned here are interrupted, in order not to interrupt the continuity of the elastic ring.

Drawings 36, 37 illustrate a variation of the ring of drawing 5. The elastic ring 53 bears at its centre two additional thin circumferential rims 54. In the off- operation phase, drawing 36, the rims 54 are protruding into the external part of the case and the ring 53, into space A, whereas they simuitaneously leave between them a very thin circumferential slot 55.

During operation start-up, the known pressure differences exist internally and externally of the case, resulting in the thin rims 54 being reverted first, forming the slot 55a, followed by the known compression of the principal circumferential ring 57 onto the fixed rings 58, and the radial contracting of the elastic disk 59.

Filtering of the water is also effected inside the slot 55a of the thin rims as well as through the holes 56. It is evident that this variation also holds for the radial arrangement of drawings 21 and 30.

During the interruption of the operation and the start-up of the cleaning phase, all the ring 57 is ejected outwards, as known, whereas the thin circumferential rims 54 are fully reverted, ejecting the foreign bodies into the space A outside the case.

Thin rims 55 can be fitted respectively, apart from the inner part of the elastic vertical channels of drawing 21 and 30, into the slots of the elastic bodies (drawing 31-35 ; not drawn).

In another variation, instead of thin and protruding rims, thin protruding craters-small tubes 60 may be prevised, inside the holes 60a of the elastic

rings. Drawings 38 and 39 illustrate their washing out and operation, respectively.

Drawings 40 and 41 illustrates another variation of drawings 36 and 37, where between the rims 55, the additional fixed ring-like disk 61 interferes. Drawing 40 illustrates the operation phase where apart from the phenomenon of inversion of the rims 55, relative movement between the rims and the additional perforated fixed disk 61 exists. In another variation, the reversal of the rims 55 is not necessary, but the fixed ring-like disk 61 is simply promoted further into space A, so that it is at all phases in continuous contact with the rims 55. Washing out is effected then only by reverse flow of water (not drawn).

Drawings 42, 43 illustrate a variation of the principal filter of drawing 5, where the spacer cylinders 8 that existed in the fixed ring 4 are now simply transferred to the elastic ring 64 and replaced with the elastic cylinders 63 which constitute, however, part of the ring 64. The same elastic cylinder 64 also bears the elastic open channel formed by the circumferential rims 65. As a pressure difference develops between the spaces A and C of the case, the elastic rings 64 are compressed onto the flat rigid disk 62, with a result that the heights of the elastic spacer cylinders 63 are compressed and are different in the operation phase x3 and washing-out x4. It is evident that x3 < x4.

Initially, the rims 65 are reverted and then the rings are compressed together in order to maintain the void space between the rigid ring 62 and the thin rims 55 constant at a specific size.

During the operation interruption period, Drawing 42, the pressure difference stops existing, the rings regain their initial size, the void space between the rigid 62 and elastic disks 64 increases, x3 becomes equal to x4 and the rims 55 are released and reverted.

In another variation, the rims 65 may not be reverted but operate as known and described in drawing 5.

Drawings 48-50 illustrate a variation where the elastic ring 1 does not bear the usual circumferential open channel 15 but has the form of a simple cup 86 with a perforated bottom. The cups are placed one into the other in a column, supported to the spacer cylinders 63. The elastic cups 86 bear at their circumferential case, both at the convex and concave part, engraved small filtering channels 88 with a progressively decreasing cross section and the same number of edges 87 at the edge of the case. The inclination angle of the small channels 88 between two successive cups 86 has an opposite sign, (+) S, (-) drawing 50 so that the small channels 88 of the successive cups touch each other, being crossed together. Thus, there is no case that the inclination angle of the small channels of two successive cups coincides, so that the cross section for water passage is locally doubled and the quality of filtering changed. Water enters from the circumference of the cup, space A and is directed towards the perforated bottom to the space C.

Drawing 48 illustrates the three discrete positions of the cups for understanding the operation cycle. In position (a), off-operation, the cups 86 that form the case are at a distance of each other in the region of the perforated bottoms, equal to Da and their circumferential cover forms an angle Pa with the horizontal level. Water enters between the circumferential covers of the cups 86 via the edges 87 and the small channels 88 that at this position has the width x14, drawing 49. The pressure differences formed bend the circumferential covers of the cups that are now adjacent and are pressed together. Passage of water is now only effected between the small channels 88 that are alternated which are now compressed and have a width x13, drawing 49. The cases of the cups form the angle Pb with the horizontal level and the relationships 00>0o, X14 >X13, Da > Db and Za>Zb, hold, where Z are the thickness of the case of the cups X the width of the small channels 88

and D is the distance of the bottoms of the cups. The filter enters into position (ß), the operation position.

With the interruption of the operation or with the start-up of the cleaning phase, the filter returns in position (a). With the start-up of the cleaning phase and the reverse movement of water between the cups, the circumferential covers of the cups are expanded as a fan, are further displaced apart, the void space between two successive covers expands and the width x of the small channels increases. The foreign bodies that have been trapped in the small channels 88 during the operation phase are released and easily removed with the cleaning water. We are at position c and the following relations hold : Bp > pa > oc, xl5 > xl4 > xl3, Za > Zo > Zc and Da = Dc > Do Drawing 51 illustrates another variation similar to those of drawings 48-50 with the difference that the circumferential case of the cup 89 is separated with deep triangular incisions 90, to a great extent by independent blades 91. In the position (a), off-operation, the cups are open and have a circumference of dl. In position (ß) the circumferential cover is contracted and bent, the triangular incisions 90 converge to a straight line and the circumference of the Circle in this phase of the operation (ß) becomes d2, which is smaller than dl. In these variations of drawings 48-51 the small channels should not necessarily be similar in their concave and their convex part, nor the cover to have the form of a fan, nor is the opening and closure of the circumferential cover be affected in the form of a fan. It is self-evident that between the elastic surfaces of the variations of Drawings 48 to 51, fixed or elastic separating surfaces could be added in order to have a constant distance between the bottoms of the cups at all phases. Furthermore, in other variations, the separating surfaces and the edges 97, or the cup itself could be shaped so that the case (a) when off- operation is tight, as it happens in Drawing 5 with the assistance of the edge 5-not drawn. A large number of similar variations can be mentioned where the elastic elements of the case are compressed during the operation, due to the pressure

difference, reducing the filtering void spaces, while they return to their prior position, with larger void spaces, in order to facilitate the cleaning phase.

Furthermore, it could be possible that in other variations the whole ring is not elastic, but only a part of it or the release and the opening of the rings in the off- operation phase is performed with springs, etc. Furthermore, it could be possible that the cups of Drawings 48 to 51 were horizontal (ßß = 0) in the positions (a) and (c). It is self-evident that the two edges of the closed elastic ring of an open cross section 1 of drawing 5, may also have the shape of the wavelike fan of drawings 48-50, with the same engraved small channels in the circumference of the edges. In this case, the angle of inclination of the small channels in the two edges of the same ring is opposite.

All the reversals of rims or other elements mentioned in the present invention during the cleaning phase, may be caused not only by the internal tensions of the elastic material they are made of but also form the pressure differences developed during the cleaning with the method of the reverse movement of water.

It is self-evident that the filters mentioned in the present invention concern all liquids and that the movements of the case or channels effected under the energy of water, can be effected by independent electric motors.