Abstract:
Provided is a filtration system including a filter housing having an inlet port and an outlet port. A plurality of filtration units are disposed within the filter housing. The system can further include at least one cleaning system configured for cleaning at least one filtration unit of the plurality of filtration units and at least one drive unit. The at least one drive unit can be configured for displacing one or both of said at least one filtration unit of the filtration units and the at least one cleaning system with respect to the other of said at least one filtration unit of the filtration units and said at least one cleaning system.

Description:
TECHNOLOGICAL FIELD 
       [0001]    This disclosed subject matter relates to fluid filtration systems. More particularly the disclosure is concerned with back-flush filter systems configured with a plurality of filtration units. The term back-flush filter is also referred to as backwash filter. 
         [0002]    The disclosed subject matter further relates to a transmission mechanism for such filtration systems. 
       PRIOR ART 
       [0003]    References considered to be relevant as background to the presently disclosed subject matter are listed below:
       U.S. Pat. No. 4,642,188   U.S. Pat. No. 4,906,373   U.S. Pat. No. 5,855,799       
 
         [0007]    Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter. 
       BACKGROUND 
       [0008]    U.S. Pat. No. 4,642,188 discloses a multi-element filter unit which includes backwash apparatus and comprises a filter casing with provision for alternative, oppositely directed process liquid and backwash liquid flows therethrough. A plurality of filter tubes are closely spaced within the filter casing. A flange engages the filter tubes and divides the filter casing into first and second chambers. Apparatus for sequentially backwashing the filter tubes during a backwash interval removes collected solids from between the filter tubes by flow of backwash liquid from one filter tube outward toward the exterior of adjacent filter tubes. The backwash apparatus includes poppet units aligned with open ends of the filter tubes and selectively actuable to close the opposed ends of one of the filter tubes while leaving another open to backwash flow thereinto, such that each filter tube is backwashed in sequence while the others are closed against backwashing liquid flow thereinto, and diffuser structure which apportions, lengthwise of the filter tube, the rate of backwash liquid flow radially out through the wall of each filter tube. 
         [0009]    U.S. Pat. No. 4,906,373 discloses a multiple element filter system comprising a filter housing defining a water inlet for water to be filtered, a filtered water outlet, a plurality of cylindrical filter elements, each defining upstream and downstream surfaces, disposed in the filter housing such that the upstream surfaces communicate with the water inlet and the downstream surfaces communicate with the filtered water outlet, and a flushing assembly which includes a movable flushing communication member arranged for selectable flushing communication with the upstream surfaces of each of the plurality of filter elements and apparatus for selectable coupling of the communication member to a flush drain at atmospheric or relatively low pressure. 
         [0010]    U.S. Pat. No. 5,855,799 discloses a high capacity filter apparatus for removing solids from fluids and includes an opposing filter element defining an internal volume. Fluid to be filtered passes through the filter elements into the internal volume and through an outlet. The filter element is continuously cleaned by backwashing along the outer surface of the elements. 
       GENERAL DESCRIPTION 
       [0011]    The disclosed subject matter is concerned, according to a first of its aspects, with a filtration system comprising a plurality of filtration units and a cleaning system, wherein one or both of said filtration units and cleaning system is displaceable with respect to the other of said filtration units and cleaning system. 
         [0012]    According to a second aspect of the disclosed subject matter there is provided a transmission mechanism configured for converting motion from one or more drive units to the plurality of filtration units and cleaning system. 
         [0013]    According to yet an aspect of the disclosed subject matter there is provided a filtration system comprising a plurality of filtration units, wherein the plurality of filtration units are configured as one or more sub-assemblies comprising a plurality of parallely disposed filtration units. The system further comprises at least one cleaning system configured for cleaning at least one filtration unit of the plurality of filtration units in the one or more sub-assemblies. Also provided is at least one drive unit associated with each of the one or more sub-assemblies, the at least one drive unit being configured with a transmission mechanism. The at least one drive unit being configured for displacing the one or both of said filtration units and the at least one cleaning system with respect to the other of said filtration units and said at least one cleaning system within each of the one or more sub-assemblies. 
         [0014]    Filtration systems according to the disclosed subject matter can comprise a housing having an inlet port and an outlet port. The housing can be further configured with a drain port adapted to be closed during a filtration process and to be opened during the cleaning process. 
         [0015]    The plurality of filtration units can be parallely disposed within the housing. The cleaning system in accordance with an embodiment can be received within each of the plurality of the filtration units. The cleaning system is configured for cleaning at least one filtration unit. The filtration system can further comprise at least one drive unit and a transmission mechanism in conjunction with the at least one drive unit, and configured for displacing one or both of said filtration units and the at least one cleaning system with respect to the other of said filtration units and the at least one cleaning system. 
         [0016]    A filtration system in accordance with an aspect of the disclosed subject matter comprises: 
         [0017]    a filter housing comprising an inlet port and an outlet port; 
         [0018]    a plurality of filtration units disposed within the filter housing; 
         [0019]    at least one cleaning system configured for cleaning at least one filtration unit of the plurality of filtration units; and 
         [0020]    at least one drive unit, wherein the at least one drive unit is configured for displacing one or both of said at least one filtration unit of the filtration units and the at least one cleaning system with respect to the other of said at least one filtration unit of the filtration units and said at least one cleaning system. 
         [0021]    A filtration system in accordance with yet an aspect comprises: 
         [0022]    a filter housing comprising an inlet port and an outlet port; 
         [0023]    a plurality of filtration units, wherein the plurality of filtration units are configured as one or more sub-assemblies comprising a plurality of parallely disposed filtration units; 
         [0024]    at least one cleaning system configured for cleaning at least one filtration unit of the plurality of filtration units in the one or more sub-assemblies; 
         [0025]    at least one drive unit associated with each of the one or more sub-assemblies, the at least one drive unit being configured with a transmission mechanism, and 
         [0026]    wherein the at least one drive unit being configured for displacing the one or both of said filtration units and the at least one cleaning system with respect to the other of said filtration units and said at least one cleaning system within each of the one or more sub-assemblies. 
         [0027]    Any one or more of the following features and designs can be applied to the filtration systems or to any one of the other aspects subject of the present application, independently or in combination:
       the displacement of the at least one filtration unit of said plurality of filtration units and the at least one cleaning system can be either or both rotatable and linear motion, imparted to either one or both of the at least one filtration unit of the plurality of filtration units and the at least one cleaning system, simultaneously or separately;   the filtration system in accordance with the disclosed subject matter further comprising a transmission mechanism;   the transmission mechanism is associated with the at least one drive unit;   the transmission mechanism can be configured for imparting the at least one cleaning system with linear reciprocal motion and/or combined reciprocal rotary motion;   the transmission mechanism can be configured for converting motion from said at least one drive unit to the at least one of the plurality of filtration units and the at least one cleaning system;   the transmission mechanism can be a planetary gear;   the transmission mechanism, can be a planetary gear configured with one or more speed reduction stages;   the transmission mechanism is a planetary (epicyclic) gear system configured with a sun gear mounted on an input shaft articulated to the at least one drive unit, said sun gear being engaged with a plurality of first pinion gears; said pinion gears being each articulated to a rotation shaft of at least one of the plurality of the filtration units or a cleaning system and configured for imparting rotary motion thereto;   each of the plurality of first pinion gears is engaged with a corresponding second pinion gear coaxially extending and each engaged with third stage gear, each articulated to a rotation shaft of a filtration unit or a cleaning system and configured for imparting rotary motion thereto;   the first pinion gears are internally engaged with a first, static ring gear and with a second gear ring which in turn is externally engaged second pinion gears, each articulated to a rotation shaft of the at least one of the plurality of filtration units or the at least one of the cleaning system and configured for imparting rotary motion thereto, said first gear ring being fixed;   the first ring gear constitutes part of a cover member of the transmission mechanism;   the transmission mechanism can be configured for substantially reducing revolving speed imparted by the drive unit in order to obtain substantially high momentum in order to render the system compatible for operating at substantially rough conditions (e.g. dirt in the filtered fluid), whilst on the other hand obtaining a substantially low transmission ratio in order to cut waste water during a cleaning/rinsing procedure;   if required revolution reduction ratio takes place in several stages;   furthermore, gear ratio change can take place manually or automatically;   according to a particular example the first ring gear constitutes part of a cover member of the transmission mechanism.   the at least one cleaning system can be configured as a jet system configured for applying jets of fluid against a surface of the filtration units;   the at least one cleaning system can be configured as a suction system configured for applying suction over a surface of the at least one of the plurality of filtration units;   either one of the plurality of filtration units and the at last one cleaning system can be static whilst the other of said plurality of filtration units and at least one cleaning system can displace in rotatable and/or linear motion, or both of the plurality of filtration units and the at least one cleaning system can displace revolvingly and/or linearly;   at least one of the plurality of filtration units is in the form of a cylindrical cartridge;   at least one of the plurality of filtration units comprises disc filters;   at least one of the plurality of filtration units comprises a thread filter;   at least one of the plurality of filtration units is a screen filter;   the plurality of filtration units is parallely disposed within the housing;   each of the at least one cleaning system is coaxially disposed within each of the plurality of filtration units;   the at least one drive unit is a power motor or a hydraulic turbine or a hydraulic pump;   the plurality of filtration units are configured as one or more sub-assemblies comprising a plurality of parallely disposed filtration units, each sub-assembly being configured with at least one drive unit and a transmission mechanism in conjunction with the at least one drive unit, and being configured for displacement of one or both of said filtration units and cleaning system with respect to the other of said filtration units and cleaning system within each of the one or more sub-assemblies;   displacement of the plurality of filtration units and cleaning system can be either or both rotatable (revolving) and linear motion, imparted to either or both, simultaneously or separately. Accordingly, either or both of the plurality of filtration units and cleaning system can be static whilst the other of said plurality of filtration units and cleaning system can displace in revolvingly and/or linearly, or both of the plurality of filtration units and cleaning system can displace revolvingly and/or linearly;   displacement of the filtration units and cleaning system can be reciprocal (linear and revolvingly) or continuous (revolvingly);   a filtration unit used in conjunction with a filter system according to the disclosed subject matter is of any type e.g. disc filters, thread filters, solid filters, screen filters, etc., and typically is in the form of a cylindrical cartridge;   reciprocal motion can be obtained by alternating direction of rotary motion imparted by the drive unit or by a rotary direction inverting mechanism;   a rotary direction inverting mechanism can be a threaded guide rod configured with several high pitch threads and a stationary nut mounted thereon. Other direction inverting mechanisms are for example a piston or an ascending gear wheel mechanism.   The cleaning system (also referred to as a rinsing system) can be a jet system configured for applying jets of fluid against a surface of the filtration units, or a suction system configured for applying suction (vacuum) over a surface of the filtration units;   according to a particular example, the cleaning system can be configured for applying the rinsing jets and suction force in combination or alternatingly;   the filter system can be configured for substantially reducing overall friction within the system by reducing rotary friction. For that purpose, axial forces on revolving members can be significantly reduced or eliminated, with friction resident substantially in sealing gaskets;   cleaning of the plurality of filtration units requires efficient screening of a surface of the filtration units, i.e. substantially full surface coverage of the jet nozzles and/or suction cups over said surfaces;       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0063]    In order to better understand the subject matter that is disclosed herein and to exemplify how it can be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0064]      FIGS. 1A to 1F  are directed to a filtration system in accordance with an example of the present disclosed subject matter, wherein: 
           [0065]      FIG. 1A  is a top perspective view of the filtration system; 
           [0066]      FIG. 1B  is a horizontal section along line A-A in  FIG. 1A ; 
           [0067]      FIG. 1C  is a longitudinal section along line B-B in  FIG. 1A ; 
           [0068]      FIG. 1D  is a longitudinal section along line C-C in  FIG. 1A ; 
           [0069]      FIG. 1E  is a top view illustrating in further detail a drive unit and transmission mechanism used in the filtration system of  FIG. 1 ; 
           [0070]      FIG. 1F  is a detailed view of a sectioned top portion of the filtration system; 
           [0071]      FIG. 1G  illustrates a sectioned top portion of a filtration system according to a modification, directed to a particular transmission mechanism; 
           [0072]      FIG. 2A  is a top isometric view of a second example of a filtration system in accordance with another example of the present disclosed subject matter being a so-called partial in-line configuration, wherein a body portion is made translucent for visualization; 
           [0073]      FIG. 2B  is a top isometric view of a filtration system being a so-called in-line filtration system, wherein a body portion is made translucent for visualization; 
           [0074]      FIG. 3  is directed to still an example of the filtration system in accordance with the disclosed subject matter, being a top perspective view of which a portion of the housing is made translucent for illustrative purposes; 
           [0075]      FIGS. 4A to 4D  schematically presents a filtration system in accordance with the disclosed subject matter wherein a liquid drive unit is associated with each filtration unit/cleaning system, wherein: 
           [0076]      FIG. 4A  is a perspective view of the filtration system, at its filtering position; 
           [0077]      FIG. 4B  is a longitudinal planner view of  FIG. 4A ; 
           [0078]      FIG. 4C  is a perspective view of the filtration system at its cleaning position; 
           [0079]      FIG. 4D  is a planar sectioned view of  FIG. 4C ; 
           [0080]      FIG. 5  is a perspective view illustrating a filtration system in accordance with yet an example of the disclosed subject matter wherein a central turbine is configured for propelling the filtration unit/cleaning system, wherein the system is illustrated at a filtering position; 
           [0081]      FIG. 6  is a perspective view illustrating a filtration system in accordance with still an example of the disclosed subject matter wherein each filtration system/cleaning system is configured with a hydraulic turbine, the system being illustrated at a filtering position; 
           [0082]      FIGS. 7 to 10  illustrate transmission mechanisms in accordance with examples of the present disclosed subject matter, wherein: 
           [0083]      FIGS. 7A and 7B  are a top and bottom perspective view, respectively, of a first transmission mechanism; 
           [0084]      FIGS. 8A and 8B  are a top and bottom perspective view, respectively, of a second transmission mechanism; 
           [0085]      FIGS. 9A and 9B  are a top view and sectioned view along line A-A in  FIG. 9A , respectively, of yet an example of t a transmission mechanism; and 
           [0086]      FIGS. 10A and 10B  are top and bottom perspective views, respectively of even yet an example of t a transmission mechanism. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0087]    Attention is first directed to  FIGS. 1A to 1E  of the drawings illustrating a filtration system in accordance with a first example of the present disclosed subject matter, generally designated  20 . The filtration system  20  is a so-called ‘partial in-line’ filtration system, comprising a cylindrical housing  22  mounted over support legs  24  and comprising an inlet port  28  extending into a filter inlet space  30  within the housing  22 , and an outlet port  32  extending from a filtration space  34 . The filter inlet space  30  and the filtration space  34  are partitioned by a first partition member  36 , whilst a second partition member  37  partitions between the filter inlet space  30  and a filtrate drain space  38  configured with a drain port  39 . 
         [0088]    The filtration space  34  accommodates a plurality (six in the present example) of stationary (rotatably fixed) filtration units  40 , being hollow cylindrical filtration cartridges, e.g. solid filtration cartridges, disc cartridges, mesh filtration cartridges, etc. it is however appreciated that, throughout the present disclosure, a filtration unit can be of any type. Coaxially received within each of the filtration units  40  there is a cleaning system  42 , as will be discussed hereinafter in further detail. 
         [0089]    Housing  22  is configured with a top cover  48  secured by a plurality of bolts  50  to a flange  52  configured at a top edge of the housing  22 . Mounted over the top cover  48  there is a drive unit generally designated  54  and a transmission mechanism generally designated  56 , to be discussed hereinafter with more detail. 
         [0090]    In the present examples the drive unit  54  is an electric motor (though other motors are possible too, e.g. a hydraulic motor, pneumatic motor, etc.) coupled via a transmission gear  62  and extending over a support bridge  64 . The transmission gear  62  is configured for converting rotary motion of the motor axis into rotary motion at a substantially perpendicular axis. Said perpendicular axis being a central input axis  66  extending coaxially into the housing  22  of the filtration system  20  and articulated with the transmission mechanism  56  for imparting rotary motion to a central gear  70 , the latter engaged with a plurality of pinion gears  72 , each mounted at a top end of a cleaning tube  74  of each of the cleaning systems  42 , as will be discussed hereinafter. The transmission gear  62  is also configured for imparting rotary motion and reciprocal axial motion to the central input axis  66 , and the electric motor is fitted with an electric circuitry for rotating it alternately in opposite directions during the cleaning stage. 
         [0091]    Each cleaning system  42  is configured with a central pipe/tube  80  (also referred to as cleaning pipe/tube) provided with a plurality of jet emitting nozzles  82  spaced along the tube  80  and extending in close proximity to an inside face of the filtration unit, said tube  80  extending through the filter inlet space  30  in a sealed fashion (i.e. the cleaning tubes  80  sealingly extend through said filter inlet space  30 ), wherein the tubes  80  open into the filtrate drain space  38 . The tubes  80  extend out of the filtration unit  40 , through sealed passages within the top cover  48  and are coupled to rinsing fluid supply ducts (not shown) articulated thereto. 
         [0092]    The arrangement is such that at a filtration position of the filtration system  20  raw fluid enters the filter inlet space  30  through inlet port  28  and then enters into the filtration space  33  within each filtration unit  40  whereupon the fluid is filtered and a filtered fluid thus flows into the filtration space  34  from where it is collected through the outlet port  32 . In this position there is no fluid flow through the tubes  80  of the cleaning system and the drain port  39  is sealed. 
         [0093]    At a cleaning/rinsing position a rinsing fluid is propelled through the top of the cleaning system tubes  80  whilst electric motor  54  rotates. Rotation of the electric motor  54  results in corresponding rotation of the cleaning pipe  80 , though at significantly reduced speed, and with corresponding axial displacement of the entire transmission mechanism  56 , owing to reciprocal linear motion imparted thereto via the gear mechanism  62 , wherein a jet of rinsing fluid is applied through each of the jet nozzles  82  and impinges against the inside surface of the filtration units  40 , said rinsing jet screening effectively along the inside surface of the filtration units, i.e., covering substantially the entire inside surface thereof, wherein the rinsing fluid together with the filtrate (waste water together with dirt accumulated over the walls of the filtration unit) drain into the filtrate drain space  38  and are allowed out through the drain port  39 . 
         [0094]    It is however appreciated that according to a modification (not shown) of the disclosure referred to in  FIGS. 1A to 1F , filtration can take place radially into the filtration units (i.e. in direction from the filtration space  34  into the filtration units  40 ), whereupon a cleaning/rinsing procedure takes place by a jet of fluid applied on the inside surface of the filtration unit (i.e. radially outwards). 
         [0095]    It is further appreciated that a cleaning/rinsing procedure can take place by a combined jet rinsing and suction applied over the surface of the filtration unit. 
         [0096]    The illustration of  FIG. 1G  illustrates a transmission mechanism generally designated  81  and fitted externally, on top of the housing  22 . A power input shaft is coupled to a central input gear  82  axially fixed (i.e. non displaceable in an axial direction, but only free to rotate) which in turn is coupled to three pinion gears  72  (similarly to the configuration disclosed in  FIG. 1E ). Each of the pinion gears is rotatably mounted on a threaded axle. However, input gear  82  is significantly thicker (higher) than the pinion gears  72  engaged therewith, and wherein rotation of the pinion gears  72  over the input gear  82  generates a combined axial reciprocal motion of the pinion gears  72  about their axes, as represented by arrows  83 , and reciprocal (or not) revolving motion as represented by arrows  84 . Axial reciprocal displacement of the pinion gears  72  entails corresponding axial displacement of the cleaning tubes  74  articulated thereto. 
         [0097]    The example illustrated in  FIG. 2A  resembles that illustrated in connection with  FIGS. 1A to 1F  in that it is a so-called partial in-line configuration filter system designated  85 , wherein the inlet port  86  and outlet port  96  are not coaxial. However, in the present example it comprises only three filtration units, each designated  84  and extending within the housing in a symmetrical fashion. 
         [0098]    In a filtration process according to the example of  FIG. 2A  raw fluid flows through the inlet port  86 , into an inlet space  88 , then into the filtration space within each of the filtration units  84 , wherein the fluid is filtered and whereby filtered fluid now flows into the filtration space  94  and out through the outlet port  96 . 
         [0099]    During a rinsing process the electric motor  100  revolves and imparts alternatingly rotational motion to the gear system  102  which on the one hand converts rotary motion of the motor  100  into rotary motion about a central axis perpendicular to that of the motor, and on the other hand imparts reciprocal axial motion to the threaded rod  104  which serves as an input shaft for the transmission mechanism generally designated  110 . 
         [0100]    Thus, during a rinsing/cleaning procedure, a rinsing fluid is introduced into the cleaning tubes (parallely disposed within the filtration units  84 ; not seen) resulting in fluid jets immersing through jet nozzles of the cleaning tubes extending in close proximity with an inside surface of the filtration units  84 , whereby cleaning fluid and dirt drains down to the bottom chamber  88  (now disconnected from a raw fluid supply line and serving as a drain port). 
         [0101]    As can be seen in  FIG. 2A , the transmission mechanism  110  is configured for imparting the rinsing tube with linear reciprocal motion as indicated by arrowed line  126 , and combined reciprocal rotary motion, as illustrated by arrowed lines  128 , thereby reaching optimal rinsing of the filtration units  84  by the fluid jets reaching substantially the entire inside surface of the filtration units  84 . As mentioned hereinabove, rinsing jets can be replaced, or accompanied by suction cleaning force applied over the surface of the filtration units. 
         [0102]    It is appreciated that each of the rinsing tubes (not seen) is received within a support tube  130  extending into the filter inlet space  88  thus isolating the cleaning tube  120  from the filter inlet space  88  and for supporting said cleaning tube whilst facilitating its reciprocal linear and reciprocal motion about a longitudinal axis thereof. 
         [0103]    The example illustrated in  FIG. 2B  is substantially similar to that disclosed in connection with  FIG. 2A , however being a so-called ‘in-line’ back-flush filtration system  140  wherein the inlet port  142  extends substantially coaxial with the outlet port  144 . Thus, the configuration of  FIG. 2B  requires suitable fluid flow diverting means received within the bottom housing compartment  146 , to facilitate fluid flow between the inlet port  142  and outlet port  144 , during the filtration/rinsing procedures. Apart for this difference, the example of  FIG. 2B  is similar in construction and principle operation to that disclosed in connection with that of  FIG. 2A . 
         [0104]    The filtration system  149  illustrated in  FIG. 3  is based on the principles discussed hereinabove in connection with the previous examples, however where the filtration units are grouped into sub-assemblies each designated  150  and each composed of a cluster holding three filtration units  152  disposed in a triangular configuration and extending parallel to one another. Furthermore, each sub-assembly  150  is configured with an independent drive unit, namely motor  156 , each associated with a motion converting gear unit  158  mounted over a domed bridge  160  and articulated to a transmission mechanism  164  as discussed hereinbefore in connection with the previous examples. 
         [0105]    Operation of the large scale filtration system of  FIG. 3  takes place similarly to the disclosure hereinbefore, however in larger volumetric scale. 
         [0106]    Turning now to  FIGS. 4A to 4D  there is illustrated a filtration system in accordance with yet a modification of the present disclosed subject matter, generally designated  200 , wherein the housing  202  is configured with an inlet port  204  and an outlet port  206  and a plurality of filtration units (five in the present example, though only three of which are seen in the sectioned view) and designated  210 , symmetrically disposed within the housing  202  with their longitudinal axis parallelly disposed within the housing  202 . 
         [0107]    The housing  202  is configured with a filtration space  214  accommodating said filtration units  210 , a filter inlet space  216  extending below said filtration space  214 , and a top chamber  220  configured with a drain fluid outlet port  222  and accommodating a drive unit  226 , each associated with a filtration unit  210 . The drive units  226  are so-called hydraulic motors configured for generating rotary motion and further fitted with a central piston assembly  230  reciprocally linearly displaceable within a vented piston support housing  236  with a venting port  238 . 
         [0108]    The piston  230  is for example a hydraulic piston configured with one or two side controls (i.e. retract and/or expand activators). 
         [0109]    Extending from the top chamber  220  there are a plurality of cleaning/rinsing units in the form of tubes  240 , each associated with a filtration unit  210 , said cleaning tubes extending from the top chamber  220  through each of the filtration units  210  and down into the inlet space  216 . Each of the tubes  240  is configured with a plurality of suction cups/nozzles  244  radially extending in close proximity with the inside surface of the filtration units  210 . 
         [0110]    The arrangement being such that the cleaning tubes  240  are linearly and rotatably reciprocal, in a combined motion, within the space of the filtration units  210 , and thus configured for effective and efficient screening and suction of the entire inside surface of the filtration units  210 . 
         [0111]    During a filtration mode of the filtration system  200  ( FIGS. 4A and 4B ), raw fluid enters through the inlet port  204  and enters the inside surface of the filtration units  210  where it is filtered and then exits through the filtration space  214  and then exits through the outlet port  206  as illustrated in these drawings by arrowed lines  245 . 
         [0112]    During a filtration process the drain fluid outlet port  222  is closed and during the rinsing process drain fluid outlet port  222  opens. 
         [0113]    In a rinsing/cleaning mode,  FIGS. 4C and 4D , suction is applied through the inlet port  204  and then into the rinsing tubes  240  resulting in rinsing jets applied through the jet applying nozzles  244  against the inside surface of the filtration units  210 , wherein the dirty waste fluid (filtration fluid with dirt) exits through the top openings  241  of the tubes  240 , into the top chamber  220  and then egresses through the drain fluid outlet port  222 . 
         [0114]    Whilst in the example illustrated with reference to  FIGS. 4A to 4D  the drive unit articulated with the cleaning assembly is a liquid-operated motor (“hydraulic motor”), in the example illustrated in  FIG. 5  the drive unit is a central turbine designated at  280  configured for generating rotary motion and distribution of said rotary motion to each of the rinsing tubes  282  by virtue of a gear system comprising a peripheral geared ring  284  engaged with a plurality of gearings  286  each associated with a cleaning tube  282 . The geared ring  284  extends along a significant portion of the top chamber  290  whereby the turbine  280  and the articulated gear  286  are free to axially displace therein between a downward position and an uppermost position during the rinsing position. 
         [0115]    Apart for this difference, the examples of  FIGS. 4 and 5  operate in the same manner during a filtering stage and a rinsing/cleaning stage and reference is made to  FIG. 4  above for understanding how these stages take place. 
         [0116]    Likewise,  FIG. 6  illustrates yet an example of a filtration system in accordance with the disclosed subject matter generally designated  300  the difference residing in that rather than a central turbine as disclosed in connection with  FIG. 5  there is provided a separate turbine unit  302  articulated with each filtration unit  304  and serving as an independent drive unit therefor. 
         [0117]    Other than this difference, operation of the filtration system  300  is similar to that disclosed in connection with the examples of  FIGS. 4 and 5  during their filtration stage and rinsing/cleaning stage and reference is made thereto. 
         [0118]      FIGS. 7 to 10  are directed to different examples of transmission mechanism that are useful in connection with filtration systems in accordance with the present example. Turning first to  FIGS. 7A and 7B  there is illustrated a gear transmission configured with an input gear  350  configured for coupling to an input shaft of a drive unit by cogged shank portion  352 . The input gear  350  is engaged with a plurality of first pinion gears  356  (five in the present example) each integral with and coaxially extending with a second level of gears  358  which in turn are engaged with second pinion gears  362 . The arrangement is such that input gear  350  has a smaller diameter than that of first pinion gears  356  which have a larger diameter than the engaged gears  358  which in turn are significantly smaller than the second pinion gears  372 , thereby obtaining significant speed reduction throughout the transmission assembly. Second pinion gears  362  are engaged with the tubular rinsing members (not shown) by virtue of internally geared portion  366 . 
         [0119]    In the example of  FIGS. 8A and 8B  there is illustrated a different example wherein a sun gear  380  is configured for coupling to an input shaft of a drive unit (not shown) which in turn said sun gear  380  is engaged with three first pinioned gears  382 , mounted over a carrying triangular plate  383  at a fixed planetary configuration, engaged for rotation with a geared ring  386  constituting part of a cover portion  390  for said transmission mechanism, i.e. being fixedly articulated and non-rotatable. In turn, the gears  382  are engaged with an internally and externally geared ring  388  which is engaged, through its external geared portion with second pinion gears  394 , each of which being coupled to a rinsing tube (through an internally cogged portion  396 ) for imparting said tube (not shown) rotary motion during a rinsing/cleaning process. 
         [0120]    Turning now to  FIGS. 9A and 9B  there is provided a pinion gear  400  configured for coupling to an input shaft of a drive unit (not shown) and engaged with three first pinions  402  each of which pivotally mounted on an axel  406  projecting from a carrying plate  408 . First pinions  402  are engaged with an inner geared ring  410  which is static, i.e. fixedly secured to a housing component of the filtration unit, with a second gear  412  coaxially extending below each first pinion  402  and engaged in turn with an internally and externally geared ring  416  which in turn is engaged with a plurality of second planetary gears  420  ( 5  in the present example) each of said second pinion gears  420  being coupled to a rinsing tube (not shown) for imparting thereto rotary motion. 
         [0121]    The example illustrated in connection with  FIGS. 10A and 10B  resembles that of the example of  FIGS. 9A and 9B  and comprises an input sun gear  440  configured for coupling to an input shaft of a drive unit (not shown) and which in turn is engaged with three first planetary gears  442 , each of which being internally engaged with an internally geared static ring  446  (being part of a cover assembly  448  of the transmission mechanism). Second planetary gears  452  are engaged in turn with a central geared disc  552  carrying the first pinions  452  in a planetary motion. 
         [0122]    Whilst several particular examples of gear transmissions have been exemplified, it is to be realized that different configurations and combinations can be designed, without departing from the scope of the disclosed subject matter. For example, revolution reduction ratio can take place in several stages and furthermore, gear ratio change can take place manually or automatically.