FR2698283A1 - Lost wet cloth belt filter - in which the cloth passes over a series of rollers, some immersed in tanks of clean water or the liq. to be filtered, but only one roller is driven - Google Patents

Abstract

Belt filter (12) with lost wet cloth (17), consisting of a tank (2) to receive the filtered liq., rollers around part of which the mesh belt is driven, on which the filter cloth is placed, and means for driving the rollers and to move the belt. The cloth issues from a roller mounted for free rotation and is driven at the same time as the belt on the filter trajectory. After use it is collected outside the tank for disposal. The part (12a) of the belt where the cloth is overlaid runs partly round a reversing roller (3) mounted inside the tank and above the part (2b) of the tank which receives the filtered liq. The liq. to be filtered is introduced into the tank above this part of the belt and is contained, awaiting filtration, in the volume (2a) described by the cloth on the belt and the side walls of the tank in which the reversing roller is immersed. This roller is perforated to allow the passage of the liq. across the filter cloth at the lowest point of the volume (2a). USE/ADVANTAGE - Filtration of liquids using the lost wet band technique. This technique depends on the belt being wetted, but spraying has been shown to be unsatisfactory.

Description

 Carrier belt and wet lost cloth filter.

DESCRIPTION
The present invention relates to a carrier belt filter and wet lost fabric.

 The technical sector of the invention is that of filtration devices.

 There are known filters with a carrier band and a lost filter cloth, on which the liquid to be filtered is poured onto the cloth above a tank at the bottom of which the filtered liquid is collected dripping below the cloth.

 We also know that such fabrics must, depending on their texture, be moistened to make them efficient and obtain optimal filtering power.

 Until now the humidification of the filter cloths was done by spraying but the result obtained was not very satisfactory.

 The present invention aims to remedy the drawbacks of known devices.

 The objective of the present invention is to optimize the filtration process by implementing and perfecting a filter equipped with a wet lost filter cloth.

 This objective is achieved by the filter according to the invention, comprising a tank for collecting the filtered liquid, rollers around which the mesh carrier strip is partially wound, on which the filter cloth is placed, means for driving said rollers in rotation and for scrolling the strip, which fabric comes from a roller mounted with free rotation and is driven at the same time as the said carrying strip on the filtration path, and is then received after use outside the bin in view of its discharge, characterized in that the carrying strand of said strip on which said canvas is pressed, is partially wound around a deflection roller mounted inside the tank and above the part of said tank in which the filtered liquid is collected and in that the charging liquid to be filtered is introduced into said tank above said carrying strand and the filter cloth and is contained, awaiting its filtrate ion, in the volume delimited by said fabric bearing on said carrier strip and the side walls of the tank in which said deflection roller is immersed, which is perforated to allow the passage of liquid through the filter cloth at the lowest point of said volume .

 Said carrier strip is partially wound from above around two rollers located at the top of the tank and above the perforated return roller around which it is wound from below and it is wound from below around at least a roller located below said tank. The filter cloth pressed against said carrier strip is partially wrapped around said upper and deflection rollers.

 One of said upper rollers has drive means, which drive roller is located at the end of said tank opposite that where said perforated idler roller is, so that the strand carrying the strip on which the filter cloth and extending between said rollers is inclined from bottom to top in the direction of travel of the strip and the cloth.

 Said supporting strand is supported on at least one intermediate roller disposed between said drive roller and said perforated deflection roller.

 One of the upper rollers is mounted to rotate freely and is brought closer to said perforated return roller and the part of the strip and fabric which extends between said rollers is inclined up and down towards the rear of the filter with respect to the direction. scrolling of the strip and the fabric to promote the humidification of the fabric upstream of the perforated return roller.

 Said strip and canvas part form with the horizontal an angle a less than 900 and between 60 and 800.

 The bottom and end walls of said tank are located in the space delimited by the go-and-go and return strands of the carrier strip.

 To further improve the performance of the filter cloth, said filter comprises, upstream of said tank and on the path of the filter cloth, a tank of clear water in which is mounted an at least partially submerged return roller, around which is wound from below the filter cloth from the cloth roll and in which the tank takes place the first wetting of the cloth.

 According to the invention, the rotation of the drive roller of the carrier strip and the filter cloth is carried out by means of alternating operation, the movable actuator member of which comprises a pawl which cooperates with thrust receiving members exerted by said movable member and regularly distributed at the periphery and equidistant from the center of a wheel associated with said roller.

 In a particular embodiment, said wheel consists of two coaxial flanges connected by spacers parallel to the axis of rotation of the wheel and which constitute said receiving members.

 Said means for driving said roller in rotation consist of a double-acting cylinder whose movable rod comprises at its free end an actuating member on which is mounted said pawl which cooperates with said spacers of said wheel of the drive roller.

 More particularly, said cylinder is a membrane cylinder to which the movable rod of the cylinder is coupled and which, under the deformation of the membrane, is actuated in one direction to apply, by said pawl, a tangential force on said receiving organs of the wheel, which rod is subjected to the action of an opposing return spring to bring it back in the opposite direction to its initial position and return the actuator to a new thrust cycle.

 The admission of the fluid into the chamber of the jack and its expulsion are obtained by a distributor with drawer with three orifices and with two positions, of which said drawer is actuated by said actuating member by means of a two-position rocker arranged on the path of said organ.

 Said rocker is mounted on an axis transverse to the rod of the jack and situated on the side of the control of the drawer of said distributor, which rocker comprises two arms extending on either side of said axis to cooperate alternately each with one or the other of two locks, in that said rocker is equipped with a spiral spring to cooperate with said actuator member and be tilted to exert a force on said control of the drawer. Locking in one or other position of the rocker is obtained by means which tend to put locks in contact with the end of the arms of the rocker. Unlocking is obtained by displacement of said actuating member during a cycle of operation of the jack, alternatively, by action on one and the other lock, so that each locked position of one arm of the rocker corresponds to an unlocked position of the other arm and correspondingly the reversal of the opening or closing the distributor circuits.

 According to a particular embodiment, said latches are pivotally mounted and are subjected to the action of a spiral spring.

 In an embodiment where the jack is hydraulically operated, said jack comprises a valve regulating the supply water to the jack as a function of the level of the liquid to be filtered, which valve is connected to said distributor and comprises a float in flotation. on the surface of said liquid, which tap regulates the water flow until closing when the level of the liquid to be filtered drops and reaches a minimum level and correspondingly stops the supply of the jack and the rotation of said drive roller.

 The result of the invention is an improved carrier belt filter and wet lost filter cloth, the cloth is embedded in the liquid to be filtered to improve performance. The path of the filter cloth in the medium to be filtered and the position of the return immersion roller, in the lower part of the tank, creates a "low point" where residues or other impurities are deposited, allowing the liquid to pass through said roller and to cross the sedimentation layer and the supporting fabric over a greater distance. The fact that said roller is perforated further improves the filtration capacity.

 The clear water tank in which the fabric is immersed upstream of the tank of the liquid to be filtered, further improves the performance of the filter fabric.

 Finally, the use of a hydraulic motor makes it possible to install such a filter in places not equipped to supply other energy, such as electricity or compressed air. It is understood that the drive of the carrier strip and the filter cloth could just as easily be obtained from motors operating with such energies. But the use of hydraulic energy is particularly interesting and practical, since the filter requires, if only for the humidification of the fabric, to be supplied with water from existing networks or with the filtered water from the filter and raised in pressure by a hydraulic multiplier according to known techniques.

 Another advantage of the filter according to this design lies in the fact that the entrainment of the filter cloth stops automatically as soon as the liquid to be filtered reaches a minimum level in the filtration tank.

The applications of such a filter are the most diverse
- Filtration of effluents from areas used by self-propelled vehicles (motorway rest areas, parking lots, parking lots, etc.) loaded with hydrocarbons and various types of pollution
- filtration of road or motorway effluents loaded with hydrocarbons and brines due to the salting of roads in winter
- filtration of loaded water for reuse in irrigation, for example localized irrigation in agriculture.

 Finally, it will be understood that such a filter can find many other industrial applications, such as for example the filtration processes used in the manufacture of food products.

Other advantages and characteristics of the invention will become apparent on reading the following description given by way of nonlimiting example and with reference to the appended drawings in which
- Figure 1 is an overall perspective view of the filter according to the invention
- Figure 2 is a longitudinal sectional view of the filter of the previous figure
- Figure 3 is an overall diagram of the filter cloth driving device
- Figure 4 is a sectional view of the motor for driving the filter cloth
FIG. 5 is an elevation view on a larger scale of the actuator means of the slide device fitted to the motor of FIG. 4.

 Reference is first made to FIGS. 1 and 2 which show a carrier band filter and a wet lost fabric according to the invention in one embodiment.

 Such a filter 1 is made up of a metallic structure of a generally parallelepipedal shape comprising two lateral walls, for example of heavy sheet metal 1a / 1b, which walls are connected together and kept at a distance by several spacers lc. Between these walls la / lb is mounted a strong folded sheet ld comprising two bottom walls ldi / 1d2 inclined and converging downwards, to meet on a fold line ld3 constituting a low point, and are extended upwards respectively by a wall part ld4 inclined towards the left in FIG. 2 and a substantially vertical part 1d5. Said parts are delimited by fold lines, so that said folded sheet id constitutes with said walls la / lb, a tray 2 which , taking into account the design of the filter and as will be explained below, is suitable for receiving the liquid to be filtered at its upper part 2a and the filtered liquid at its lower part 2b. The wall 1d can be welded to the side walls 1a / 1b or be fixed by any other means with possibly interpositions of side seals.

 Said tank comprises in the lower part, a deflection roller 3 mounted for free rotation about an axis 4 fixed to said side walls 1a / 1b of the filter. Said roller 3 is perforated and consists of two flanges 3a connected to each other by rods 3b equidistant and parallel to the axis 4, which rods 3b are regularly distributed around the periphery of said roller 3. Said roller 3 is said deflection roller and "squirrel cage", taking into account this design.

 The filter further comprises other rollers: a roller 5 located above the roller 3, and mounted in free rotation at its upper part around an axis 6 fixed to said side walls la / lb; a roller 7 located below the roller 3 and the bottom plate id of the tank 2, which is mounted in the same way as said rollers 3 and 5 around an axis 8 and, finally, a roller 9 located at the upper part of the filter and opposite the rollers 3, 5, 7, which is carried by a shaft 10 mounted, in a conventional manner, in bearings fixed to said walls la / lb, which shaft extends from a walls, for example 1b, to receive a wheel 11 for driving the roller in rotation, wedged on said shaft 10 by any conventional means such as keying.

 Around said rollers 3, 5, 7, 9 is partially wound an endless carrier strip 12. This strip 12 is thus partially wound from above around rollers 5 and 9 and from below around rollers 3 and 7.

 The supporting strand 12a which extends between the rollers 3 and 9 and the strand which extends between the deflection rollers 3 and 5, define with said walls la / lb, a volume at the upper part 2a of the tank 2, intended to receive the liquid to be filtered.

Said carrier strip 12 has large meshes to allow the filtration liquid to pass and comprises along its lateral edges seals, for example with lip, to ensure the tightness of said volume 2a. The carrying strand 12a is supported by two rollers 13/14 of smaller diameter, the return strand is guided by two other rollers 15/16 similar to said carrying rollers 13/14. The roll 16 has the function of tensioning the carrier strip. The filter cloth 17 is wound around a roller 18 mounted for free rotation at the upper part of the filter, behind the carrier strip 12 / rollers 3, 5, 7, 9, relative to the direction of travel of the strand. carrier 12a given by the arrow F. said non-woven type fabric, for example known in the industry under the names INTISSEL or
LOHMAN, is wound from below around another roller 19 located substantially at the level of said deflection roller 3 and is wound from above around roller 5 while being applied to the carrier strip 12. Said fabric travels from roller 5 up to roller 9 resting on said strip 12, being wound from below around the roller 3 and from above around the drive roller 9 and is finally received loaded, on the ground passing through a corridor 20 for its evacuation. The carrying strands 12a associated with the filter cloth 17 and return of the strip 12, are located and pass on either side of the walls ldl to 1d4 of the tank 2.

 To further increase the performance of the fabric 17, the roller 19 is partly immersed in a tank 21 containing clear water This tank has at its lower part a drain valve 22 to empty it in the event that it is not no need to do a first wetting of the canvas 17.

 The liquid to be filtered 23 is introduced through a pipe 24 which opens at the upper part of the volume 2a. By sedimentation, the impurities are deposited on the fabric 17 by passing through the deflection roller 3 at the lowest point of said volume 2a. The relative position of the rollers 3 and 5 means that the strip and cloth part 12b / 17a which extends between the said rollers is inclined up and down in the front direction towards the rear of the filter, with respect to the direction of scrolling F of the fabric and of the strip, so that the portion of the strip and of canvas forms with the horizontal XX1 an angle a of between 60 and 80, in any case less than 900.

 This inclination has the effect of increasing the concentration of impurities between the fabric and the roller 3 and improves the filtration process, which continues to occur during the path of the fabric until approximately between said support rollers 13/14. The liquid is filtered and collected in part 2b which constitutes the bottom of the tank 2, which comprises at the lowest point and just above the fold ld3 an evacuation pipe 25 which opens into said part 2b.

 The drive roller 9 is set in rotation by said wheel 11 actuated by motor means, an example of which is given in FIG. 4.

 Said wheel 11 consists of two flanges of the same diameter, coaxial and parallel to each other 11a, joined to one another by spacers llb regularly distributed at their periphery, parallel to the axis of rotation of the wheel and equidistant from their center. The wheel 11 is rotated by fraction of a turn by an alternating motor 26 which, according to the example shown in the drawing, is a hydraulic cylinder supplied with water supplied on the site on which the filter is installed.

 Said cylinder 26 consists of a chamber 27 constituted by two hemispherical bells 27a / 27b joined to each other by bolts 28 and between which is inserted in their junction plane a membrane 29. At the center of this membrane is fixed a rod 30, one end 30a of which is threaded and passed through the membrane. The rod is fixed to the membrane 29 by a clamping nut 31. Two washers 32/33 are supported on the opposite faces of the membrane, the nut being tightened against the washer 33. Said rod 30 passes through said bell 27a and a base 34 which may include a wear ring through which the rod slides. Said base 34 is rigidly connected to the bell 27a by a body, for example cylindrical 35, fixed to the base and to said bell by any known means.

 The rod 30 comprises a stop ring 36 mounted for example between two elastic rods engaged in two grooves reserved at the periphery of the rod, which ring stop is located in the space delimited between the base 34, the bell 27a and said cylindrical body 35. A helical counter compression spring 37 is disposed between said base 34 and said stop ring, which spring has the function of exerting a push on the rod to move it, as well as the membrane 29 on the side of the bell 27b, as shown in dotted lines in FIG. 4.

 At its end opposite to that which is fixed to the membrane 29, the rod 30 has a threaded constriction 30b, which is screwed into a thread 38a reserved in an actuator member 38 of a generally cubic shape.

 Said actuator member 38 comprises a pawl 39 mounted in a known manner around an axis 40 and returned by a spiral spring 41 in a housing 38b reserved for the upper part of said member 38. The jack 26 is fixed by its base 34 to a support perpendicular to the wall 1b of the filter, so that the pawl 39 exerts, periodically at each movement of the actuator member 38 and of the rod 30 in the direction of the arrow Fl, a tangential thrust on the spacers llb of the wheel he. The displacement is obtained by the pressure of the water admitted into the chamber 27 through the orifice 27bl and deformation of the membrane 29, as shown in solid lines in FIG. 4. Thanks to the inertia of the drive roller 9 carrying the filter cloth 17 charged with impurities and also with the tension of the carrying strip 12, the roller remains in position at the end of each fraction of a turn.

On the return of the rod 30, under the effect of the spring 37 in the direction of the arrow F21 the pawl 39 tilts and passes under the spacers to recover under the effect of said spring 41, in the deployed position and cooperate again with an llb spacer.

 The cycle is resumed alternately under the pressure of the water and the deformation of the membrane 29.

 The periodic admission of water into the chamber 27 of the jack and its expulsion are obtained by a drawer distributor 42 with three orifices 42a / 42b / 42c and two positions, for example of the type marketed by the firm CPOAC, including the drawer (not shown) is actuated by said actuator member 38 acting on a rocker mechanism 43, cooperating with two pivoting latches 44 and 45 and shown on a larger scale in FIG. 5. Said rocker 43 is mounted on an axis 46 transverse to the rod 30 of the cylinder 26 and located on the side of the push-button control 42d of the distributor 42. It comprises two arms 43a / 43b in the extension of one another and extending on either side of the axis 46. The arm 43a is mounted immediately below the actuator member 38 and is beveled so that it can be tilted when said member 38 passes and above said distributor 42, as shown in dotted lines in FIG. 5. It features around its axis 46 a spiral spring 47 which comes into contact with the actuator member 38 when the latter moves in the direction of arrow F1.

 The lock 44 is pivotally mounted around an axis 48 and tends to pivot towards the end of the arm 43a in the direction of the arrow F3 under the effect of a spiral spring 49 bearing on a stop 50. Said lock 44 has a notch 44a in which the end 43a of the arm 43 is placed in the locked position.

The latch 45 is also pivotally mounted about an axis 51 and tends to pivot towards the end of the arm 43b in the direction of the arrow
F4, under the effect of a spiral spring 52 bearing on the stop 53.

 Said lock 45 includes a notch 45a in which the end of the arm 43b is placed in the locked position of the rocker 43. The upper part 44b / 45b of the locks 44/45 is located on the path of the actuator member 38 to alternately rotate said latches by action of said member 38.

 According to the invention, the water supply to the actuator 26 is done through a float valve-regulator 54, the float 55 of which is floated on the surface of the liquid to be filtered 23. The diagram in FIG. 3 gives the hydraulic supply circuits to the cylinder 26.

Water, coming from the public network for example, at a relaxed pressure of 1 bar, is admitted into the tap 54 by a pipe 56 connected to the inlet orifice 54a of said tap. The float 55 is fixed to a rod 57 articulated to a lever 58 itself articulated to a tab 54b of the valve 54. To this lever is further articulated a rod 59 at the end of which is fixed a shutter 60 which cooperates with a seat 54c reserved in a partition wall 54d of said valve. In the open position of the shutter 60, the water admitted through the inlet orifice 54a passes through the orifice delimited by the seat 54c and leaves said tap through the adjustable outlet orifice 54e which is connected by a line 61 to the orifice 42a of the slide valve distributor 42. The orifice 42c of the distributor is connected to the orifice 27bi of the chamber 27 of the cylinder 26 by a line 62. The orifice 42b of the distributor is connected to a line of leakage of lost water 63, this water possibly being able to be recovered with a view to its reuse, for example for filling the tank 21.

 According to the concept of the regulating valve 54, the shutter 60 closes on its seat 54c when the level of the liquid to be filtered 23 reaches a minimum level. The regulator slows down the cylinder operating cycles until it is completely closed. The power supply to the actuator 26 being interrupted, the movement of the filter cloth 17 and of the support strip 12 is automatically stopped to be taken up gradually thereafter as soon as the level of said liquid 23 rises.

The operation of the actuator supply device 26 is as follows
In the "retracted" position of the rod 30 in the direction of the arrow F2 and as shown in dotted lines in FIGS. 4 and 5, the rocker 43 is in the locked position, the end of its arm 43a being in the notch 44a of the latch 44. The actuating member 38 acting on the latch 45 has made it pivot in the opposite direction to the arrow
F4.

 In this position, the orifice 42a of the dispenser is open, the chamber 27 is filled with inert water, the return water from the orifice 27bl in the direction of the arrow F5 to the dispenser 45, is expelled by the leakage orifice 42b.

 Starting occurs by supplying circuits 61/62 through distributor 42 in the direction of arrow F7. The actuator member 38 moves in the direction of arrow F1 until it first meets, by the pawl 39, the spacers llb of the wheel 11, and then by its base, the latch 44 and the rotate in the opposite direction to arrow F3. Simultaneously, the spring 47 brought into contact with said member 38 exerts a force on the rocker 43 by torsion and makes it pivot in the direction of arrow F6.

 The lock 45, released from the action of the member 38, pivots under the effect of the spring 52 in the opposite direction to the arrow F4, against the arm 43b of the rocker, which arm 43b is placed in the notch 45a of said lock to be momentarily immobilized in the position shown in solid lines.

 In this position, the rocker 43 by action on the push-button 42d of the distributor 42, closes the water circuit between the orifices 42a and 42c of said distributor 42 and opens the leak orifice 42b. The pressure dropping in the chamber 27, the rod 30 and the actuating member 38 move in the direction of the arrow F2 under the effect of the opposing spring 37, until reaching the retracted position of the rod 30 shown in dotted lines. Figure 4. During this movement, the water is expelled from the chamber 27 and returns in the direction of the arrow F5 to pass through the leakage orifice 42b of the dispenser. Simultaneously with the end of the return stroke of the rod 30 in the direction of the arrow F2, the actuator member encounters the latch 45 on its path and drives it by pivoting in the opposite direction to the arrow F4.

 The latch 44, released from the thrust exerted by the member 38, returns under the effect of the spring 49 bearing on the end of the arm 43a. As soon as the latch 45 is unlocked, the rocker 43 no longer subjected to the action of the spring 47 bearing on the member 38, is pushed from bottom to top in the opposite direction to the arrow F6, by the push-button 42d of the distributor 42. Simultaneously the arm 43a is placed in the locked position in the notch 44a of the latch 44. During the return of the rod 30 and of the member 38 in the direction of the arrow F2, the pawl 39 escapes the spacer llb of the wheel there and is placed at the end of the "retracted" stroke of the rod 30 in the deployed position to exert a new thrust. The water admitted again into the chamber 27 of the jack deforms the membrane 29 which moves in the direction of arrow F1 the rod 30 and its actuating member 38, driving during this new cycle, the wheel 11 according to a fraction of a turn, and the cycle is continued until the water coming from the pipe 56 is voluntarily stopped or by closing the supply circuit by the regulating valve 54 when the level of the liquid to be filtered 23 reaches a minimum level in said volume 2a of the filter.

 Of course, without departing from the scope of the invention, the parts which have just been described by way of example, may be replaced by a person skilled in the art by equivalent parts fulfilling the same function.

Claims (16)

 i. Carrier belt (12) and wet lost cloth (17) filter, comprising a tank (2) for collecting the filtered liquid, rollers around which the mesh carrier belt (12) is partially wound, on which the filter cloth (17), means for driving said rollers in rotation and for moving the strip (12), which cloth (17) comes from a roller mounted with free rotation and is driven at the same time as said carrier strip on the filtration path, and is then received after use outside the tank for its evacuation, characterized in that the carrying strand (12a) of said strip (12) on which is pressed said fabric (17), s '' partially wrapped around a deflection roller (3) mounted inside the tank (2) and above the part (2b) of said tank in which the filtered liquid is collected and in that the liquid charged to filter, is introduced into said tank (2) above said carrying strand (1 2a) and the filter cloth (17) and is contained, awaiting its filtration, in the volume (2a) delimited by said cloth (17) bearing on said carrier strip (12) and the side walls of the tank (2 ) where said deflection roller (3) is immersed, which is perforated to allow the passage of liquid through the filter cloth (17) at the lowest point of said volume (2a).  2. Filter according to claim 1, characterized in that said carrier strip (12) is partially wound from above around two rollers (5/9) located at the upper part of the tank (2) and above the roller openwork return (3) around which it is wound from below and that it is wound from below around at least one roller (7) located below said tank (2) and in that the fabric filter (17) pressed against said carrier strip (12) is partially wrapped around said upper rollers (5/9) and return (3).  3. Filter according to any one of claims i and 2, characterized in that one of the upper rollers (9) comprises drive means (11/26), which drive roller (9) is located at the 'end of said tank (2) opposite to that where is said perforated deflection roller (3), so that the carrying strand (12a) of the band (12) on which is disposed the filter cloth (17) and s' extending between said rollers (3/9) is inclined from bottom to top in the direction of travel (F) of the strip and the fabric.  4. Filter according to any one of claims 1 to 3, characterized in that said carrying strand (12a) is supported on at least one intermediate roller (13/14) disposed between said drive roller (9) and said perforated idler roller (3).  5. Filter according to any one of claims i to 4, characterized in that one of the upper rollers (5) is mounted to rotate freely and is brought closer to said perforated return roller (3) and that the strip part ( 12) and canvas (17) which extends between said rollers (3/5) is inclined up and down towards the rear of the filter with respect to the direction of travel (F) of the strip (12) and of the fabric (17) to promote the humidification of the fabric upstream of the perforated deflection roller (3).  6. Filter according to claim 5, characterized in that said strip portion (12) and fabric (17) form with the horizontal (xxi) an angle (a) less than 900 and between 60 and 800.  7. Filter according to any one of claims i to 6, characterized in that the bottom (ldl / ld2) and end (ld4 / ld5) walls of said tank (2) are located in the space delimited by the carrier strands and return of the carrier strip (12).  8. Filter according to any one of claims 1 to 7, characterized in that it comprises upstream of said tank (2) and on the path of the filter cloth (17) a tank of clear water (21) in which is mounted an idler roller (19) at least partially immersed around which is wound from below the filter cloth (17) from the cloth roller and in which tank takes place the first wetting of the cloth.  9. Filter according to any one of claims 1 to 8, characterized in that the rotation of the roller (9) for driving the carrier strip (12) and the filter cloth (17) is carried out by means (26) operating alternately, the movable actuator member (38) of which comprises a pawl (39) which cooperates with members (nib) receiving the thrust exerted by said movable member (38) and regularly distributed at the periphery and equidistant from the center of a wheel (11) associated with said roller (9).  10. Filter according to claim 9, characterized in that said wheel (it) consists of two coaxial flanges (lia) connected by spacers (nib) parallel to the axis of rotation of the wheel and which constitute said receiving members.  11. Filter according to any one of claims 9 and 10, characterized in that said means (11/26) for rotating said roller (9) consist of a double-acting cylinder (26) whose rod mobile (30) comprises at its free end an actuating member (38) on which is mounted said pawl (39) which cooperates with said spacers (nib) of said wheel (11) of the drive roller (9).  12. Filter according to any one of claims 9 to 11. characterized in that said cylinder (26) is a membrane cylinder (27) to which the movable rod (30) of the cylinder is coupled and which, under the deformation of the membrane, is actuated in one direction (Fi) to apply, by said pawl (39), a tangential force on said receiving members (llb) of the wheel (11), which rod (30) is subjected to the action of an opposing return spring (37) to bring it back into the opposite direction (F2) in its initial position and return the cylinder (26) to a new thrust cycle.  13. Filter according to any one of claims 9 to 12, characterized in that the admission of the fluid into the chamber (27) of the jack (26) and its expulsion are obtained by a drawer distributor (42) with three orifices (42a / 42b / 42c) / and with two positions, of which said drawer is actuated by said actuating member (38) by means of a rocker (43) with two positions arranged on the path of said member (38).  14. Filter according to any one of claims 9 to 13, characterized in that said rocker (43) is mounted on an axis (46) transverse to the cylinder rod (30) and located on the side of the control (42d ) of the drawer of said distributor (42), which rocker (43) comprises two arms (43a / 43b) extending on either side of said axis (46) to cooperate each alternately with one or the other of two latches (44/45), in that said rocker (43) is equipped with a spiral spring (47) to cooperate with said actuator member (38) and be tilted to exert a force on said control (42d) of the drawer (42), in that the locking in one or the other position of the rocker (43) is obtained by means (49/52) which tend to put latches (44/45) in contact with the end arms (43a / 43b) of the rocker (43) and that the unlocking is obtained by displacement of said actuator member (38), during an operating cycle of the jack, alternatively by action on one and the other lock (44/45), so that each locked position of one arm (43a) of the rocker (43) corresponds to an unlocked position of the other arm (43b) and correspondingly the reversal of the opening or closing of the distributor circuits (42).  15. Filter according to claim 14, characterized in that said latches (44/45) are pivotally mounted and are subjected to the action of a spiral spring (49/52).  16. Filter according to any one of claims 9 to 15, of which said cylinder (26) is hydraulically operated, characterized in that it comprises a regulating valve (54) for the supply water to the cylinder (26) depending on the level of the liquid to be filtered (23), which valve (54) is connected to said distributor (42) and comprises a float (57) floating on the surface of said liquid (23), which valve (54) regulates the flow of water until closing when the level of the liquid to be filtered (23) drops and reaches a minimum level and correspondingly stops the supply to the jack (26) and the rotation of said drive roller (9).