Abstract:
A self-cleaning system for use with a filter having a fluid inlet station, including (a) a manifold mountable at least for reciprocation along an axis with respect to said filter and comprising at least one suction opening adapted to be in proximity to said station and connectable to a suitable suction source for enabling foreign material to be removed from said filter when said system is installed and in operation with respect to said filter; (b) fluid powered motive means for propelling said manifold along said axis; and (c) a reciprocating mechanism for alternately changing the direction of motion of said manifold along said axis.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to continuous flow filter devices, specially such devices that incorporate automatic self-cleaning systems. The invention is particularly concerned with filter self-cleaning systems that are powered by a fluid, and more particularly by the operating fluid that is being filtered. 
       BACKGROUND OF THE INVENTION 
       [0002]    Filtering systems are widely used for removing particles from liquids. Some such system have a pre-filtering unit equipped with a coarse filter for removing rough particles from the liquid, and a fine filtering unit with a multi-layer sintered filtering element for removing particles, which according to the specific filtering application, may be of a size ranging between  2  and  500  microns, for example. 
         [0003]    A problem encountered with such systems is the accumulation of particles and sediments on the filtering element during filtration, which block the filtering apertures or pores of the element. While in some cases, the filtering efficiency is initially increased, such sedimentation leads to a lowering of the flow throughput of the system, and, if untreated, to a full blockage thereof. Such filtration systems thus need to be serviced from time to time, in order to clean or replace the at least partially blocked filter element. In some systems, this would require temporary system shutdown, to enable this work to be carried out. 
         [0004]    Self-cleaning filter systems have been developed to enable the filter element to be cleaned in situ without the need for dismantling the system, which is otherwise required for accessing the filter element. In U.S. Pat. No. 6,267,879, an improved continuous filtering apparatus is disclosed, having a preliminary filtering chamber having a liquid inlet and a coarse filtering screen, and a final filtering chamber having a cylindrical multi-layer sintered filtering element in liquid communication with the preliminary filtering chamber across the coarse filtering screen. A filtered liquid chamber is in liquid communication with the final filtering chamber across the sintered filtering element, and has a liquid outlet. An electromechanical cleaning system is provided, adapted to remove sediments from the sintered filtering element, and controlling means enable activation of the cleaning system during the filtration process, for limited periods or continuously, according to the operational mode. The self-cleaning system is based on a back and forth helical motion of a dirt collector having dirt suction members equipped with spraying nozzles. The spraying nozzles use the filtered liquid after being pressurized by a booster pump for vibrating and rinsing the sediments accumulated on the sintered filtering element. The pressure-difference between the liquid within the apparatus and the atmosphere outside of the apparatus is utilized to provide a suction force for the operation of the dirt suction members. The electrical motor is geared to the collector unit through a worm gear for obtaining the helical movement of the collector. 
         [0005]    In U.S. Pat. No. 5,228,993, a filter system uses a self-cleaning system comprising a plurality of nozzles that direct a plurality of nozzles sprays onto the clogged filter discs, following a helical path. Both linear and rotational motion to the nozzles may be provided by a single apparatus, which may be powered by hand or by an electric motor, or by separate independent apparatus, such as for example a hand operated or fluid operated piston for the linear motion, and a water powered rotating nozzle for the rotation. 
         [0006]    Of general background interest, in U.S. Pat. No. 4,157,251, a spraying system attached to a reciprocating traveler is used for cleaning banks of filters. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention relates to, but is limited to, filtration of liquids, irrigation water, recycling of sewage and industrial waste water, recycling of cooling towers water, filtration and purification of drinking water etc. 
         [0008]    The present invention provides a high efficiency continuous liquid filtering apparatus having self-cleaning mechanism allowing the continuous filtering operation, i.e. without interrupting the supply of filtered liquid. 
         [0009]    In the context of the present invention the term “multi-layer sintered filtering element” relates to any type of metallic body constructed from a plurality of metal screens of different densities or patterns, or of a plurality of metal wires, sintered together for being one integral metallic body useful for the filtration of particles from a substance flowing across its multi layers. 
         [0010]    The term “foreign material” refers to any material that is filtered out by the filter and which it is desired to remove therefrom by the self-cleaning action according to the invention. 
         [0011]    The present invention relates to a self-cleaning system for use with a filter having a fluid inlet station, comprising:— 
         [0012]    a manifold mountable at least for reciprocation along an axis with respect to said filter and comprising at least one suction opening adapted to be in proximity to said station and connectable to a suitable suction source for enabling foreign material to be removed from said filter when said system is installed and in operation with respect to said filter; 
         [0013]    fluid powered motive means for propelling said manifold along said axis; 
         [0014]    a reciprocating mechanism for alternately changing the direction of motion of said manifold along said axis. 
         [0015]    In particular embodiments, the manifold is also adapted for rotation about said axis, and said motive means comprises a rotational motor coupled to said reciprocating mechanism such as to provide a helical motion to said at least one suction opening. The rotational motor comprises at least one arm radiating from said manifold and having a nozzle outlet in communication with said at least one suction opening, said nozzle outlet being tangentially disposed with a direction of rotation of said motor. The rotational motor is coupled to said reciprocating mechanism to provide an endless helical motion to said at least one suction opening. The system may comprise a sliding bearing arrangement for mounting the system with respect to a housing comprising a said filter. 
         [0016]    In one embodiment, the rotational motor and said reciprocating mechanism comprise a follower coupled to a cylindrical cam arrangement, and wherein said cam comprises an endless track adapted for enabling the follower to reciprocate along said axis in response to a relative rotation between said cam and said follower about said axis. The endless track typically comprises twin parallel helical tracks wound in opposite directions one with respect to another, and joined together at longitudinal ends via corner portions. The cylindrical cam may be fixedly mountable to a housing comprising said filter and said follower is mounted to said manifold for rotation therewith, when the system is installed with respect to said filter. Alternatively, the follower is fixedly mountable to a housing comprising said filter and said cylindrical cam is mounted to said manifold for rotation therewith, when the system is installed with respect to said filter. 
         [0017]    In another embodiment, the rotational motor and said reciprocating mechanism comprise a follower coupled to an end cam arrangement, and wherein said end cam comprises an endless track adapted for enabling the follower to reciprocate along said axis in response to a relative rotation between said cam and said follower about said axis. The endless track typically comprises an endless undulating contour comprising a plurality of peaks smoothly joined with a number of intercalated troughs, arranged in an annular manner. The peaks and troughs may merge into one another in a substantially sinusoidal manner in a circumferential direction. The follower may be mounted to a gear arrangement coupled to said rotational motor. The gear arrangement typically comprises a planetary gear arrangement, wherein said rotational motor is mounted for rotation with a sun gear and said follower is mounted for rotation with an orbital gear of said planetary gear arrangement. The end cam may be fixedly mountable to a housing comprising said filter and said follower is mounted to said manifold for rotation therewith, when the system is installed with respect to said filter. Alternatively, the follower is fixedly mountable to a housing comprising said filter and said end cam is mounted to said manifold for rotation therewith, when the system is installed with respect to said filter. 
         [0018]    In another embodiment, the rotational motor and said reciprocating mechanism comprise a shuttle arrangement mounted on an axial rail support for axial translation with respect thereto, said rail being fixedly mountable to a housing comprising said filter when the system is installed with respect to said filter, said shuttle being coupled to said rotational motor such that a rotation of said motor about said axis provides a translation of said shuttle along said rail. The shuttle may comprise:
       a frame axially displaceable with respect to said rail and comprising a pivoting plate having two end pivot positions, said plate comprising a first gear means mounted for rotation at the pivot thereof and coupled to said rotational motor, said pivoting plate further comprising second and third gear means in mesh engagement with the other, wherein said second gear means is in mesh engagement with said first gear means via a fourth gear means carried on said pivoting plate;   first moving means coupled to a fifth gear means and second moving means coupled to a sixth gear means, each one of said second and third gear means being in alternate mesh engagement with one or the other of said fifth gear means and said sixth gear means in respective said end pivot positions of said plate;   toggle means for pivoting said plate at each said end pivot position for reversing a direction of motion of said shuttle along said rail.       
 
         [0022]    The second and third gear means typically comprise substantially the same pitch diameter. The toggle means typically comprises an arm joined to said plate and extending radially from said plate, and adapted for interacting with one or another of fixed stops for pivoting said plate at each said end pivot position. This embodiment typically further comprises a pin joined to said frame and extending through a slot in the plate. The slot defines the end pivot positions of said plate. The first gear may be coupled to said rotational motor via a worm gear arrangement. 
         [0023]    In another embodiment, the motive means comprises a fluid powered linear motor coupled to said reciprocating mechanism such as to provide at least axial reciprocating motion to said at least one suction opening. The linear motor may comprise at least one nozzle arrangement having a nozzle head comprising first and second fluid passages alternately in communication with a fluid source, said first and second fluid passages comprising fluid outlets at angles A and B, respectively to a tangential direction, said tangential direction being substantially parallel to said station when said system is installed and in operation with respect to said filter. The nozzle head may be slidingly mounted with respect to an arm between two end positions, said arm in communication with said fluid source, and comprising toggle means for sliding said nozzle head at each said end position for reversing a direction of motion of said at least one suction opening along said axis. These toggle means may comprise a tab joined to said nozzle head and extending away from a direction of said arm, and adapted for interacting with one or another of fixed stops for pivoting said plate at each said end pivot position. Angle A may be about +90° and angle B may be about −90°. The manifold is typically also adapted for rotation about said axis, and the motive means further comprises a rotational motor coupled to said reciprocating mechanism such as to provide a helical motion to said at least one suction opening. The system comprises a sliding bearing arrangement for mounting the system with respect to a housing comprising a said filter. The manifold is also adapted for rotation about said axis, and wherein said motive means further rotational motion to said manifold, such as to provide a net helical motion to said at least one suction opening. In this embodiment, angle A may be set at +α and angle B at −α, wherein the magnitude of α is substantially greater than 0° and less than about 90°. For example, the magnitude of α is about 45°. The system comprises a sliding bearing arrangement for mounting the system with respect to a housing comprising a said filter. 
         [0024]    Optionally, and for all embodiments, the manifold may comprise a plurality of arms radiating from a conduit coaxial with said axis, and comprising a said suction outlet at the extremity of each said arm. The arms may be located singly or in groups at axial locations uniformly distributed at a pitch P. Preferably, the axial travel of said system in one or another direction along said axis is correlated to said pitch P. Typically, the number of revolutions of said manifold about said axis, the number of arms at each axial location, and the axial width of said suction openings are correlated to said pitch P. Preferably, the system further comprises a spray nozzle at each said arm adapted for spraying a fluid towards said station when the system is installed in a housing comprising said filter. 
         [0025]    The present invention also relates to a self-cleaning filter assembly adapted for connection to a fluid source, comprising: 
         [0000]    a housing comprising a filter accommodated therein, said filter having a fluid inlet station, said housing having at least one fluid inlet in communication with fluid inlet station, and at least one fluid outlet in communication with a fluid outlet station of said filter; 
         [0026]    the self-cleaning system of the invention. 
         [0027]    The filter is typically substantially tubular and said filter fluid inlet station is substantially cylindrical. The manifold typically comprises an outlet providing fluid communication between said at least one suction opening and a drain chamber. The drain chamber typically comprises at least one valve open to the atmosphere during operation of said self-cleaning system. The filter typically comprises a sintered filtering element. The assembly may further comprise a preliminary coarse filtering element upstream of said sintered filtering element. The assembly may further comprise at least one differential pressure detector coupled to said system and adapted for activating said system when the differential pressure detected between said filter inlet and said filter outlet is lower than a predetermined threshold. The assembly may further comprise at least one timer coupled to said system and adapted for activating said system at predetermined times. The assembly may further comprise a by-pass switch coupled to said system and adapted for selectively activating said system on user demand. 
         [0028]    The motive means are typically powered by the operating fluid that it is desired to be filtered by said filter, the operating fluid typically being water. 
         [0029]    The present invention is also directed to a method for cleaning a filter having a fluid inlet station, comprising:— 
         [0030]    reciprocating a manifold along an axis with respect to said filter, said manifold comprising at least one suction opening adapted to be in proximity to said station and connectable to a suitable suction source for enabling foreign material to be removed from said filter when said system is installed and in operation with respect to said filter, wherein a fluid powered motive means propels said manifold along said axis, and a reciprocating mechanism for alternately changing the direction of motion of said manifold along said axis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0032]      FIG. 1  illustrates in longitudinal cross-sectional view a filter apparatus which incorporates a self-cleaning system according to the present invention; 
           [0033]      FIG. 2  illustrates, in fragmented longitudinal cross-sectional view, a first embodiment of a reciprocating mechanism used in the self-cleaning system of the invention; 
           [0034]      FIGS. 3   a  to  3   e  illustrates in greater detail the cylindrical cam used in the embodiment of  FIG. 2 :  FIG. 3   a —the cam in plan view;  FIG. 3   b —the cam in side view;  FIG. 3   d —the follower engaged in a groove in one direction;  FIG. 3   e —the follower engaged in a groove in an opposed direction to that of  FIG. 3   d ;  FIG. 3   e —the follower changing direction with respect to the cam; 
           [0035]      FIG. 4  illustrates, in fragmented longitudinal cross-sectional view, a second embodiment of a reciprocating mechanism used in the self-cleaning system of the invention; 
           [0036]      FIG. 5  illustrates, in fragmented longitudinal cross-sectional view, a third embodiment of a reciprocating mechanism used in the self-cleaning system of the invention; 
           [0037]      FIG. 6  illustrates in isometric view the edge cam used in the embodiment of  FIG. 5 ; 
           [0038]      FIG. 7  illustrates, in fragmented longitudinal cross-sectional view, a fourth embodiment of a reciprocating mechanism used in the self-cleaning system of the invention; 
           [0039]      FIG. 8  illustrates, in fragmented longitudinal cross-sectional view, a fifth embodiment of a reciprocating mechanism used in the self-cleaning system of the invention, wherein the mechanism is translating in one axial direction; 
           [0040]      FIG. 9  illustrates, in fragmented longitudinal cross-sectional view, the embodiment of  FIG. 8 , wherein the mechanism is translating in an axial direction opposed to that of  FIG. 8 ; 
           [0041]      FIG. 10  illustrates, in a view taken along the longitudinal axis, the embodiment of  FIGS. 8 and 9 ; 
           [0042]      FIG. 11  illustrates, in fragmented longitudinal cross-sectional view, a sixth embodiment of a reciprocating mechanism used in the self-cleaning system of the invention, wherein the mechanism is translating in one axial direction; 
           [0043]      FIG. 12  illustrates, in fragmented longitudinal cross-sectional view, the embodiment of  FIG. 11 , wherein the mechanism is translating in an axial direction opposed to that of  FIG. 11 ; 
           [0044]      FIG. 13  illustrates, in fragmented longitudinal cross-sectional view, the nozzle mechanism of the embodiment of  FIGS. 11 and 12 ; 
           [0045]      FIG. 14  illustrates, in cross-sectional view, the embodiment of  FIG. 13  taken along A-A; 
           [0046]      FIG. 15  illustrates, in fragmented longitudinal cross-sectional view, a nozzle mechanism of a seventh embodiment of a reciprocating mechanism used in the self-cleaning system of the invention; and 
           [0047]      FIG. 16  illustrates, in cross-sectional view, the embodiment of  FIG. 15  taken along B-B. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]      FIG. 1  illustrates a typical continuous filter apparatus which may incorporate a self-cleaning system according to the present invention. Such an apparatus may be similar to that described in U.S. Pat. No. 6,267,879, the contents of which are incorporated herein in their entirety. Of course, the self cleaning system of the present invention may be incorporated in any suitable filtering apparatus or system, in a similar way to that described herein, mut ats mutandis. 
         [0049]    The continuous filter apparatus, generally designated with the numeral  10 , comprises an elongated tubular casing  17  having liquid inlet  1  for a connection with a liquid source that provides liquid to be filtered during filtering operation of the apparatus  10 . The liquid inlet  1  feeds liquid from the liquid source to an annular first filtering chamber  9  that is in fluid communication with a second filtering chamber  3  via a cylindrical coarse screen  2 , which is adapted for removing rough particles from the liquid. Pre-filtered liquid obtained downstream of the coarse screen  2  flows through a cylindrical sintered filtering element  4  to the filtered liquid chamber  12 , and from there to the liquid outlet  6 , which is adapted for a connection to a filtered liquid duct or reservoir (not illustrated). Advantageously, the first filtering chamber  9  and the filtered liquid chamber  12  are formed as two co-axial annular compartments within a single tubular envelope, separated one from the other by an annular bulkhead  15 , which is located between the sintered filtering element  4  and the inner cylindrical surface of the tubular body  17 . 
         [0050]    A collector manifold assembly  20  comprises an elongated collection tubing  16  substantially co-axial with the sintered filtering element  4 , and further comprises a plurality of suction arms  5  radiating from tubing  16 . Typically, four to six arms may be provided, though less than four or more than six arms may also be provided. The arms  5  are located at stations on the tubing  16  that are axially spaced with respect to axis  30  in a typically uniform manner, at a pitch P. At each station, one or more arms  5  may be provided, and in any case, care is taken to distribute the arms  5  circumferentially about axis  30 , and axially on axis  30 , to provide static as well as dynamic balance with respect to axis  30 . 
         [0051]    Each suction arm  5  comprises a suction aperture  21  that faces and is in close proximity to the inner cylindrical surface of the filter  4 , which can become clogged with filtered-out particles, and further comprises an adjacent spray nozzle  11  attached to the arm  5 . The suction apertures are in fluid communication with a suction source, via the hollow arms  5  and hollow tubing  16 , as will be further described herein. The manifold  20  is mounted for axial and rotational motion within the filter body  17  by means of suitable sliding bearing arrangements  18 ,  19 , provided at the axial ends of the manifold  20 . 
         [0052]    As will be described in greater detail hereinbelow, when the self-cleaning system is in operation, the manifold  20  is rotated and simultaneously reciprocated with respect to the axis  30 . In so doing, each of the suction apertures  21 , and their corresponding spray nozzles  11 , travel along a predetermined helical path in one axial direction and then along a reversed helical path back again to their original axial position with respect to the axis  30 . The total axial displacement of the manifold  20  in any direction along axis  30  is typically similar to or greater than the pitch P, and the axial displacement for every full revolution of the manifold  20  is related to the number of arms  5  at each station, and the effective width of the suction nozzles  21 . 
         [0053]    The axial sliding movement in one direction is thus restricted between a minimum point at which the right-most pair of the suction apertures  21  and spraying nozzles  11  ( FIG. 1 ) is brought to the right end of the sintered filter  4 , and a maximum point at which the left-most pair of the suction members and spraying nozzles is brought to the left end of the sintered filter  4 . 
         [0054]    In this manner, during operation of the self-cleaning system, as the manifold  20  is rotated and displaced along axis  30  in one direction, the nozzles  21  are brought in close proximity to every part of the inside cylindrical surface of filter element  4 , which is thus fully scanned, and a second time again as the manifold is returned in the opposite direction to its original axial position. Thus, the arrangement enables each part of the filter element  4  to be cleaned of sediment in one to and fro scan of the cleaning system. 
         [0055]    Simultaneously with the helical movement of the suction manifold  20 , a booster-pump  13 , fed with liquid taken from the filtered liquid chamber  12 , is adapted for generating a relatively high liquid pressure at the spraying nozzles  11  during operation of the cleaning system. Thus, a liquid stream is sprayed from each of the nozzles  11  toward the inner surface of the sintered filter  4 , vibrating the dirt sediment and particles that may be trapped within the porous filter  4 . At the same time, liquid is sucked into the suction apertures  21  of the manifold  20 , back-washing and sweeping away the dirt from the filter  4 . Material sucked from the chamber  3  into the apertures  21  flow under pressure to a collection chamber  8  via drain apertures  25  that are provided at one end of the tubing  16 . The suction operation is generated automatically by the pressure difference that exists between the relatively high pressure liquid upstream of the filter  4 , i.e., in the second filtering chamber  3 , and free atmospheric pressure, via openings  25  the draining valves  7 ,  14 , which are in open position to the atmosphere during the cleaning operation. 
         [0056]    A cleaning operation for the cleaning system may be activated by means of a differential pressure sensor or gauge (not illustrated) adapted for identifying a predetermined differential pressure between the final filtering chamber  3  and the filtered liquid chamber  12 , indicating that a certain amount of sediments blocks the sintered filter, thus a cleaning operation is required. A programmable logic controller (not illustrated) may be utilized for controlling the operation of the cleaning system for limited periods and/or according to a timer. The timer (not illustrated) may be adapted for activating the cleaning system periodically for preventing sedimentation in case of the filtration of a relatively clean liquid which enables the differential pressure sensor to activate the cleaning system only infrequently. Both, the differential pressure sensor operating mode and the timer operating mode, may be by-passed by a continuous-operation-switch (not illustrated) which enables a user to selectively activate the cleaning system whenever desired, independently of the actual conditions of the filter, or the time elapsed from the previous cleaning cycle. 
         [0057]    The drain apertures  25  are configured as reaction nozzles provided at the radial end of an additional pair of arms  22  that are diametrically joined to an axial portion of the tubing  16  that is within the draining chamber  8 . The apertures  25  are arranged in the same angular direction with respect to axis  30 . Thus, during operation of the cleaning system, dirt and liquid are sucked through the apertures  21  and are ejected out of the drain nozzles  25 , which provide a reaction couple causing rotation of the manifold  20  about the axis  30 . Thus, the arrangement of drain nozzles  25  and arms  22  comprises a hydraulic motor, herein designated with the numeral  50 . 
         [0058]    Suitable liquid-driven axial reciprocation motive means according to the present invention, schematically illustrated in  FIG. 1  by a dotted box  101 , provide reciprocating axial motion to the manifold  20 , typically during rotation of thereof. 
         [0059]    Referring to  FIGS. 2 and 3   a  to  3   e , a first embodiment of the cleaning system of the present invention, generally designated with the numeral  100 , comprises a manifold  20  including hydraulic motor  50  as described above, and a reciprocating mechanism  150 . The reciprocating mechanism is coupled to the motor  50  and adapted for converting rotational motion provided by the motor  50  into reciprocating linear motion along axis  30 . Thus, the helical motion that may be provided to the suction apertures  21  and spray nozzles  11  are powered by the hydraulic motor  50 . 
         [0060]    The reciprocating mechanism  150  comprises a cylindrical cam  160  axially and rigidly cantilevered at one end  162  thereof to the longitudinal end plate  35  of the drain chamber  8 . Referring in particular to  FIGS. 3   a  and  3   b , the cylindrical cam  160  comprises a single, endless groove  170  that comprises a clockwise helical section  172 , and a parallel but anticlockwise helical section  174 , which cross at periodic intersections  175 , and joined at their axial ends thereof by respective connecting corner intersections  178 ,  179 . 
         [0061]    The end  32  of the conduit  16  of manifold  20  comprising the motor  50  further comprises an axial opening  36  adapted for reciprocably and rotatingly receiving the free end  164  of the cylindrical cam  160  by means of said sliding bearing arrangement  19 . The sliding bearing arrangement  19  comprises a suitable collar  180  mounted to said axial opening  36 . The inner cylindrical surface of the collar is adapted for rotation over the roller cam  160 , and further comprises a follower  182  radially projecting towards said axis  30  and engaged with respect to said grove  170 . 
         [0062]    As the manifold  20  is rotated about axis  30  under the action of the liquid motor  50 , the end  32  rotates about the static cylindrical cam  160 , and the follower  182 , together with the manifold  20 , is constrained to follow a path defined by the endless groove  170 , as follows. Starting at free end  164 , the follower  182  translates along groove  174  in an axial direction towards end  162 , as the follower  182  also revolves around the cam  160 , as illustrated in  FIG. 3   c . At end  178 , the follower  182  changes axial direction ( FIG. 3   e ) and enters groove  172 , translating the follower  182  towards free end  164 , as illustrated in  FIG. 3   d , where at the end  179 , the follower  182  again changes axial direction as it enters groove  172  once again. The number of revolutions required for the follower  182  to travel from end  179  to end  178  is related to the relative width of the suction apertures  21  with respect to the pitch P. 
         [0063]    Referring to  FIG. 4 , a second embodiment of the cleaning system of the present invention, generally designated with the numeral  200 , is similar to the arrangement described above for the first embodiment, mutatis mutandis, with the main difference that in the second embodiment the cylindrical cam, herein designated with the numeral  260 , oscillates with the manifold  20 , and the follower  282  is statically mounted to the chamber  8 . Thus, the cleaning system  200  comprises a manifold  20  a reciprocating mechanism  250  that is coupled to the motor  50  and adapted for converting rotational motion provided thereby into reciprocating linear motion along axis  30 . 
         [0064]    The reciprocating mechanism  250  comprises said cylindrical cam  260 , axially and rigidly cantilevered at one end  264  thereof to end  32  of the conduit  16  of manifold  20  comprising the motor  50 , the cam  260  comprising an endless groove  170 , as described for the first embodiment, mutatis mutandis. 
         [0065]    The end  35  of the chamber  8  further comprises a tubular sleeve  38  adapted for reciprocably and rotatingly receiving the free end  262  of the cylindrical cam  260  by means of said sliding bearing arrangement  19 . The sliding bearing arrangement  19  in this embodiment comprises a bearing  220 , the inner rotating shell of which is mounted at the end  262 , and the outer static shell being statically mounted to a sliding ring  222 , which is adapted for sliding within said sleeve  38 . 
         [0066]    The draining chamber  8  further comprises a suitable collar  280  statically mounted to the chamber via strut  285 . The inner cylindrical surface of the collar is adapted for rotation over the roller cam  260 , and further comprises a follower  282  radially projecting towards said axis  30  and engaged with respect to said grove  170 . Alternatively, the collar  280  may be mounted in the sleeve  38 . Alternatively, the collar  280  may be incorporated in the bearing arrangement  19 , similar to that described for the first embodiment, mutatis mutandis. 
         [0067]    Thus, as the manifold  20  is rotated about axis  30  under the action of the liquid motor  50 , the end  32  rotates together with cylindrical cam  260 , and the follower  282  causes the cam  260 , together with the manifold  20 , to follow a path defined by the endless groove  170 , as follows. Thus, while rotating about axis  30 , the cam  260  translates along groove  174  in an axial direction towards end  178  with respect to follower  282 , and changes direction thereat to present groove  172  to the follower  282 , translating the cam  260  back so that free end  164  approaches follower  220 , in a cyclic manner, to oscillate the cam  260  with respect to the follower  282 . In a similar manner to that described for the first embodiment, the number of revolutions required for the cam  260  to travel with respect to the follower  182 , from end  179  to end  178 , is related to the relative width of the suction apertures  21  with respect to the pitch P. 
         [0068]    Referring to  FIG. 5 , a third embodiment of the cleaning system of the present invention, generally designated with the numeral  300 , comprises a manifold  20  including hydraulic motor  50  as described above, and a reciprocating mechanism  350 . The reciprocating mechanism  350  is coupled to the motor  50  and adapted for converting rotational motion provided by the motor  50  into reciprocating linear motion along axis  30 . Thus, the helical motion that may be provided to the suction apertures  21  and spray nozzles  11  are powered by the hydraulic motor  50 . 
         [0069]    The reciprocating mechanism  350  comprises an end cam  360  axially and rigidly mounted to end plate  35  of the drain chamber  8 . Referring in particular to  FIG. 6 , the end cam  360  comprises a single, endless undulating contour  370  that a number of peaks  372  smoothly joined with a number of intercalated troughs  374 , arranged in an annular manner. In the illustrated example of  FIGS. 4 and 5 , four identical troughs  374  and four identical peaks  372  are provided, and the peaks and troughs merge into one another in a substantially sinusoidal manner in the circumferential direction. The end cam  360  is coaxially aligned with axis  30 . 
         [0070]    The end  32  of the conduit  16  of manifold  20  comprising the motor  50  further comprises a shaft  340  axially mounted thereto. The draining chamber  8  comprises a tubular sleeve  338  statically mounted to the chamber via strut  385 . the sleeve  338  is adapted for reciprocably and rotatingly receiving the shaft  340  by means of said sliding bearing arrangement  19 . The sliding bearing arrangement  19  in this embodiment comprises a bearing  320 , the inner rotating shell of which is mounted to shaft  340 , and the outer static shell being statically mounted to a sliding ring  322 , which is adapted for sliding within said sleeve  338 . 
         [0071]    At the free end  362  of the shaft  340  is mounted a sun gear  382  of a planetary gear arrangement  380 , which comprises a number of planetary gears  384  mounted for rotation on planetary carrier  386 . The planetary carrier  386  comprises one or a number of followers  373  axially projecting therefrom towards the cam  370 . A spring  390 , mounted to the center of the cam  360  and to the opposed center of the planetary carrier  386 , forces axial contact between the follower  373  and the cam  370 . The spring  390  is mounted in such a way, and/or is configured, such as not to become tangled or overwound as the planetary gear  386  revolves with respect to the cam  370 . Alternatively, the spring may be replaced by a rail arrangement that constrains the follower  373  to follow the cam  370  as it rotates about the same. 
         [0072]    As the manifold  20  is rotated about axis  30  under the action of the liquid motor  50 , the end  32  rotates about the static end cam  360 , and the follower  373 , together with the gear arrangement  380  and manifold  20 , is constrained to follow a path defined by the endless contour  370 , as follows. Starting at one trough  374 , the follower  373  translates in an axial direction away from end  35  as the follower  373  also revolves partially around the cam  360  until it reaches the adjacent peak  372 . Then, the follower  373  changes axial direction and towards end  35  as it approaches the next trough  374 . The number of revolutions required for the follower  373  to travel between adjacent troughs  374 , and the gear ratios of gear arrangement  380 , are related to the relative width of the suction apertures  21  with respect to the pitch P. 
         [0073]    Referring to  FIG. 7 , a fourth embodiment of the cleaning system of the present invention, generally designated with the numeral  400 , is similar to the arrangement described above for the third embodiment, mutatis mutandis, with the main difference that in the fourth embodiment the end cam, herein designated with the numeral  460 , oscillates together with the gear arrangement  380 , and thus with the manifold  20 , and the follower  482  is statically mounted to the end wall  35  of chamber  8 . In the illustrated embodiment, the cam  460  comprises a rail arrangement  461  that constrains the follower  482  to follow the contour  480  as it revolves with respect to axis  30 . Operation of this embodiment is similar to that of the third embodiment, mutatis mutandis. 
         [0074]    Referring to  FIGS. 8 to 10 , a fifth embodiment of the cleaning system of the present invention, generally designated with the numeral  500 , comprises a manifold  20  including hydraulic motor  50  as described above, and a reciprocating mechanism  550 . The reciprocating mechanism is coupled to the motor  50  and adapted for converting rotational motion provided by the motor  50  into reciprocating linear motion along axis  30 . Thus, the helical motion that may be provided to the suction apertures  21  and spray nozzles  11  are powered by the hydraulic motor  50 . 
         [0075]    The reciprocating mechanism comprises a rail  560  of substantially rectangular cross-section axially and rigidly cantilevered at one end  562  thereof to end plate  35  of the drain chamber  8 . 
         [0076]    The end  32  of the conduit  16  of manifold  20  comprising motor  50  further comprises an axial opening  36  adapted for reciprocably and rotatingly receiving the free end  564  of the rail  560  by means of sliding bearing arrangement  19 . In this embodiment, the sliding bearing arrangement comprises a suitable collar  580  mounted to said axial opening via bearing  585 . The collar  580  comprises an inner rectangular opening and sliding guides  586  for sliding the collar axially along the said rail  560 , and an outer typically cylindrical surface for connection to the inner race of the bearing  585  which remains static when the outer race of the bearing rotates with the manifold  20 . Thus the outer race of the bearing  585  is fixed to the axial opening  36 . 
         [0077]    Referring particularly to  FIG. 10 , the reciprocating mechanism  550  further comprises a shuttle mechanism  570 , in the form of a frame  575  comprising two drive rollers  572 ,  573  rotatingly mounted thereto, and used alternately for driving the shuttle in one direction or the other along the rail  560 . Each of the drive rollers  572 ,  573  is axially mounted to a gear wheel  582 ,  583 , respectively. The frame  575  is connected to the collar  580 . 
         [0078]    Alternatively, the upper surface of the rail  560  may comprise a rack, and the drive rollers  572 ,  573  replaced with drive pinions for better traction of the shuttle  570  with respect to the rail  560 . 
         [0079]    Alternatively, the rail may be of circular section, for example, and the rollers are appropriately shaped to enable rolling over a convex cylindrical surface. 
         [0080]    As illustrated in  FIG. 10 , the shuttle  570  may further comprise additional loose guide rollers  564  mounted on the frame  575  for free rotation with respect to the lower and vertical surfaces of the rail. 
         [0081]    A plate  585  is pivotably mounted to the frame  575  at pivot  589 . The plate  585  can pivot about pivot  589  about a pivot arc between two end positions, defined by a stop pin  576  mounted to plate  585  and sliding in an arcuate guide slot  577  in frame  575 . A first gear wheel  581  is rotatingly mounted to the plate at pivot  589 , and is in mesh with a gear wheel  586  via intermediate gear wheels  587  and  588 , all of which are carried by the plate  585 . Wheels  586  and  587  are centered on an arch of constant radius about pivot  589 , and wheels  581 ,  588  and  587  have their centers rectilinearly aligned. Wheels  586  and  587  have the same pitch diameter, and the said pivot arc of the plate  585  is such that in either of the end positions, one or the other of wheels  586  and  587  meshes with one or the other of gear wheels  582 ,  583 , respectively. 
         [0082]    Alternatively, wheels  581  and  587  could be engaged one with the other by means of a belt, rather than wheel  588 , mutatis mutandis. 
         [0083]    Thus, referring to  FIG. 8 , when the plate  585  is at the end position such that wheel  586  is engaged with wheel  582 , counterclockwise rotation of wheel  581  produces counterclockwise rotation of wheel  582 , which causes the shuttle  570  to travel away from end plate  35 . Conversely, and referring to  FIG. 9 , when the plate  585  is at the end position such that wheel  587  is engaged with wheel  583 , counterclockwise rotation of wheel  581  produces clockwise rotation of wheel  583 , which causes the shuttle  570  to travel towards the end plate  35 . 
         [0084]    The end  32  further comprises an internal gear  590  which meshes with gear wheel  592  carried on frame  575 . A worm gear  594  axially connected to wheel  592  meshes with wheel  581 . 
         [0085]    The shuttle  570  further comprises a toggle mechanism  595  for changing direction thereof between two axially distanced stops  578 ,  579  mounted in the drain chamber  8 . The toggle mechanism  595  comprises an arm  596  fixed to plate  585  and radially extending from pivot  589  such as to engage with one or another of stops  578 ,  579  when the shuttle  570  reaches one or another of the axial end positions thereof. 
         [0086]    Thus, as the manifold  20  is rotated about axis  30  under the action of the liquid motor  50 , the end  32  rotates about the rail  560 , and the shuttle  570 , together with the collar  580  and manifold  20 , is constrained to follow a reciprocating path with respect to the rail  560  as follows. Starting at or near free end  564 , the arm  596  is pressed against stop  578  such as to pivot the plate  585  to the position illustrated in  FIG. 9 , so that wheel  587  is meshed with wheel  583 , and wheel  586  is disengaged from wheel  582 . The rotation of the manifold  20  causes wheel  581  to turn in a counterclockwise direction by virtue of internal gear  590 , wheel  592  and worm gear  594 . In turn, wheel  581  turns wheel  583  in a clockwise direction, via wheels  588  and  587 , which rotates drive roller  573 , translating the shuttle  570  towards the end plate  35 . When the shuttle  570  nears the end plate  35 , arm  596  presses against the stop  579 , and the momentum of the shuttle  570  carries the same a little further such as to pivot the arm  579  to the position illustrated in  FIG. 8 . Now, wheel  586  is meshed with wheel  582 , and wheel  587  is disengaged from wheel  583 . Thus, while the manifold  20  continues to rotate in the same direction, counterclockwise rotation of wheel  581  results in counterclockwise rotation of wheel  582 , which rotates drive roller  572 , translating the shuttle  570  away from the end plate  35 . When the shuttle  570  nears the free end  564 , arm  596  now presses against the stop  578 , and the momentum of the shuttle  570  carries the same a little further such as to pivot the arm  579  back to the position illustrated in  FIG. 9 . So long as the motor  50  is rotating, the shuttle  570  will be translating the manifold  20  in one or the other axial directions. The full axial travel in either direction for the shuttle  570  is typically correlated to the dimension of pitch P, and in some embodiments may be set at about equal to the dimension of P. 
         [0087]    The number of revolutions required for the shuttle  570  to travel between stops  578 ,  579 , and the gear ratios provided by gears  590 ,  592 ,  594 ,  581 ,  588 ,  587 ,  588 ,  582   583 , are related to the relative width of the suction apertures  21  with respect to the pitch P. 
         [0088]    In yet other embodiments, rotation power may be provided by non-liquid based power sources, for example an electric motor, and the rotational power used for providing reciprocating axial motion in a similar manner to that described above, mutatis mutandis. 
         [0089]    Referring to  FIGS. 11 to 14 , a sixth embodiment of the cleaning system of the present invention, generally designated with the numeral  600 , comprises a manifold  20  including hydraulic motor  50  as described above, and a reciprocating mechanism  650 . 
         [0090]    In this embodiment, the reciprocating mechanism  650  may operate independently of the motor  50 , and in fact the system may actually operate without the need for the rotational motor  50 . In such a case, the arms  5  are connected at their radial ends to an annular collector (not shown) and the suction openings  21  may be in the form of a circumferential slit opposite to the inner cylindrical surface of the filter, or in the form of circumferentially-located closely-spaced discrete openings. In this case, it is only necessary to provide a reciprocal axial motion to the manifold  20  so that the full filter is scanned during the self-cleaning process, since the full inner circumferential periphery of the filter is covered by the annular collector at any axial position thereof. Accordingly, such an embodiment does not require the filter  4  to be cylindrical, and in fact the filter can have any cross-sectional shape, for example square, so long as the aforementioned “annular” collector comprises a complementary shape such that the suction openings, now in the form of a peripheral slit, are opposite to the inner surface of the filter. 
         [0091]    Nevertheless, the reciprocating mechanism is advantageously coupled with the motor  50 , and the combination is thus adapted for providing rotational motion and concurrent reciprocating linear motion along axis  30 . Thus, the helical motion that may be provided to the suction apertures  21  and spray nozzles  11  are powered by the hydraulic motor  50  and reciprocating mechanism  650 . 
         [0092]    A cylindrical shaft  660  is axially and rigidly cantilevered at one end  664  thereof to end  32  of the conduit  16  of manifold  20  comprising the motor  50 . The end  35  of the chamber  8  further comprises a tubular sleeve  38  adapted for reciprocably and rotatingly receiving the free end  662  of the shaft  660  by means of said sliding bearing arrangement  19 . The sliding bearing arrangement  19  in this embodiment comprises a bearing  620 , the inner rotating shell of which is mounted at the end  662 , and the outer static shell being statically mounted to a sliding ring  622 , which is adapted for sliding within said sleeve  38 . 
         [0093]    The reciprocation mechanism  650  comprises a linear dual-direction fluid motor  660 , in the form of a plurality of arms  665  radially projecting from the end  32  of the conduit  16  of manifold  20 . At the tip of each arm  660  a bi-directional nozzle  670  is provided, having two separate fluid passages  672 ,  677 , each of which has an inlet,  673 ,  678 , respectively, and an outlet,  674 ,  679 , respectively. The inlets  673 ,  678  are coplanar, and each can be alternately aligned with the mouth  667  at the free end of the arm  665  by sliding the nozzle  670  axially along rail  680  in one direction or the other. The rail  680  comprises blanks  684 ,  685  for blocking the one or other of the inlets  673 ,  678 , respectively, when the other inlet is aligned with the mouth  667 . The outlets  674 ,  679  are aligned parallel to axis  30 , but in axially opposed directions. The nozzle  670  further comprises a tab arrangement  690  that alternately cooperates with one or another of a pair of spaced annular stop rings  610 ,  620  in chamber  8  to axially displace the nozzle  670  to a position in which one or another of the inlets  673 ,  678  is aligned with mouth  667 . The tab arrangement  690  preferably comprises a free rolling wheel  695  that is mounted to the radial end of nozzle  670 , with the axis of rotation radially aligned with respect to axis  30 . The wheel  695  comprises a tread surface  696  adapted for alternate contact with one or the other of said rings  610 ,  620 . 
         [0094]    Thus, as the manifold  20  is rotated about axis  30  under the action of the liquid motor  50 , the end  32  rotates together with shaft  660 , and the linear motor  660 , together with the manifold  20 , is constrained to follow a reciprocating path as follows. Starting at or near end plate  35 , the tab wheel  695  is pressed against stop  620  such as to slide the nozzle  670  to the position illustrated in  FIG. 11 , where inlet  677  is aligned with mouth  667 , and inlet  673  is blocked. As liquid is ejected from outlet  679  in an axial direction towards end  35 , a reaction force propels the manifold  20  in an axial direction away from end  35 , at the same time as the manifold is rotating by virtue of the action of motor  50 . Accordingly, the mass flow of liquid must be sufficient to provide motive power to motor  50  and liner motor  660 . 
         [0095]    When the manifold  20  has nears its maximum displacement away from the end plate  35 , wheel  695  presses against the stop  610 , and the momentum of the manifold  20  may carry the same a little further, such as to slide the nozzle  670  to the position illustrated in  FIG. 12 . This operation is particularly facilitated by the rotation of wheel  695  along the annular ring  610  as the nozzle  670  is revolving about axis  30  under the action of motor  50 . Now, inlet  673  is aligned with mouth  667 , and inlet  677  is blocked. As liquid is ejected from outlet  674  in an axial direction away from end  35 , a reaction force propels the manifold  20  in an axial direction towards end  35 , at the same time as the manifold is rotating by virtue of the action of motor  50 . When the manifold  20  has nears its minimum displacement with respect to the end plate  35 , wheel  695  presses against the stop  620 , and the momentum of the manifold  20  may carry the same a little further, such as to slide the nozzle  670  back to the position illustrated in  FIG. 11 . 
         [0096]    So long as the linear motor  660  is operating, it will be translating the manifold  20  in one or the other axial directions. The full axial travel in either direction for the manifold  20 , slightly more than the axial displacement between stops  610 ,  620 , is typically correlated to the dimension of pitch P, and in some embodiments may be set similar to the dimension of P. 
         [0097]    Optionally, the linear motor  660  may be adapted to operate such that the outlets  674 ,  679 , or another part of the nozzle  670  alternately cooperates with the ring stops  610 ,  620 , and in such a case the tab arrangement  690  is not required and may be dispensed with. 
         [0098]    Clearly, if the motor  50  is disabled, for example by blocking apertures  25 , it is still possible for the linear motor  660  to provide reciprocating movement to the manifold. 
         [0099]    Alternatively, it is possible to slidingly mount the nozzles  670  to the arms  22  of the motor  50 , by modifying the radial ends of the arms in a similar manner to that described for the radial ends of arms  665 , mutatis mutandis. Such a modification to the sixth embodiment requires less parts overall, and shortens the axial dimension of the self-cleaning system. Optionally, the tangential nozzles  25  may be incorporated in the nozzle  670 , and in fact each one of the said passages  672 ,  677  may comprise a said tangential nozzle  25  aligned in the same direction. 
         [0100]    Alternatively, and referring to  FIGS. 15 and 16 , a seventh embodiment of the cleaning system of the present invention, generally designated with the numeral  700 , is similar to the arrangement described above for the sixth embodiment, mutatis mutandis, with the following differences. In the seventh embodiment the rotational motor  50  and the linear motor  660  may be further combined such that arms  22 ′ of the combined motor  630  each comprise a vectored nozzle arrangement  670 ′ that provides a jet of liquid providing a reaction force component in the tangential direction T for providing rotation, and reaction force component in the axial direction A for providing axial displacement. Thus, the nozzle  670 ′ comprises two separate fluid passages  672 ′,  677 ′, each of which has an inlet,  673 ′,  678 ′, similar in construction and operation with respect to rail  680  as described with respect to the embodiment illustrated in  FIGS. 13 and 14 , mutatis mutandis. The respective outlets  674 ′,  679 ′, however, are aligned with their axes  615  at angles +α and −α to the tangential direction T, so that each nozzle may provide (in turn) a tangential reaction force component in the same tangential direction T, and an axial reaction force component parallel to axis  30 , but in axially opposed directions. The nozzle  670 ′ further comprises a tab arrangement  690 ′ similar to that described in connection with tab  690  of the sixth embodiment, mutatis mutandis. Thus, in a similar manner to that described for the embodiment illustrated in  FIGS. 11 to 14 , mutatis mutandis, when the tab  690 ′ presses against ring stop  610 , the nozzle  670 ′ is displaced so that inlet  677 ′ is blocked, and inlet  673 ′ is aligned with mouth  667 ′ of arm  22 ′. The action of the liquid exiting passage  672 ′ provides a reaction force that continues to turn the manifold  20  about axis  30 , and that propels the same towards the end  35 . When the tab  690 ′ eventually presses against the second stop ring  320 , the nozzle  670 ′ slides with respect to rail  680 ′ to the position illustrated in  FIGS. 15 and 16 , so that inlet  673 ′ is blocked, and inlet  677 ′ is aligned with mouth  667 ′ of arm  22 ′. The action of the liquid exiting passage  672 ′ provides a reaction force that still continues to turn the manifold  20  about axis  30 , but that now propels the same away from the end  35 . 
         [0101]    In other embodiments, rotational motion may be provided by a liquid turbine arrangement, for example, and the rotational power coupled to a reciprocating axial motion in a similar manner to that described above, mutatis mutandis. 
         [0102]    It should be noted that the word “comprising” as used throughout the appended claims is to be interpreted to mean “including but not limited to”. 
         [0103]    While there has been shown and disclosed exemplary embodiments in accordance with the invention, it will be appreciated that many changes may be made therein without departing from the spirit of the invention.