Abstract:
An automatic valve includes a housing having an inlet passage and a passage to outlet, a linearly movable shaft disposed in the housing having two stops separated by a predetermined distance, a hydraulic unit connected to the housing and to the linearly movable shaft, and a sealing flange having at least one aperture accommodating the linearly movable shaft. The sealing flange being movable on the linearly movable shaft to close and open the passage to outlet through force of one of the stops on the sealing flange, the linearly movable shaft being biased to urge the sealing flange toward the passage to outlet by contact with one of the stops wherein the sealing flange in position to close the passage to outlet from the inlet passage despite limited movement of the linearly movable shaft.

Description:
FIELD OF THE INVENTION 
     The present invention relates to valves and particularly to automatic valves and the method for using same with filters operating with filter aid material, such as diatomaceous earth, in order to prevent such filters from transferring fine particles to the filtered fluid area at the beginning of the filtering operation when the cake is not yet uniformly disposed around the filter element and to assist the distribution and the uniformity of the filter aid material on the filter element surface area and in many other applications. 
     BACKGROUND OF THE INVENTION 
     Automatic valves have many industrial uses and are common in all kinds of assemblies. Most of the valves are manually operated. In order to operate the valves automatically, an electric or hydraulic motor, or an actuator, must be mounted on the valves to shift the interconnection and communication between the valve passages. Actuators and electric motors are both unwieldy, expensive and complex. There are automatic valves with timing mechanism for the use in a system with a Diatomaceous Earth filter, e.g. U.S. Pat. No. 5,899,231 to Drori which discloses an automatic three way valve with timing mechanism for delaying the opening of the flow. U.S. Pat. No. 6,171,495 to Drori also discloses an automatic three way valve with a time delay mechanism. The problem regarding the distribution of filter aid material on the filter element surface in an homogeneous layer is known in the field. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide an improved automatic valve constructed to transfer for a pre-determined time low flow at the beginning of operation to assist the build-up of a uniform layer of the filter aid material porous material on the filter element surface in order to receive fine filtration and to prevent fine particles to penetrate through the filter element. After such a predetermined time, the valve is open automatically to full flow. 
     In accordance with a broad aspect of a preferred embodiments of the present invention, there is provided a method and apparatus incorporating an automatic valve, preferably a three-way valve constructed of a housing having inlet, outlet and drain passages and including an internal close-open timing mechanism. The timing mechanism is adjusted to a predetermined period of time in order to close the drain passage and open the outlet passage or to close the outlet passage and open the drain passage. The opening and closing of passages occurs automatically after a predetermined period of time in response to the starting or stopping of an external source of pressurized fluid such as a pump which provides pressurized fluid to the three way valve. 
     The automatic three way valve, in accordance with the present invention, comprises a housing having inlet, outlet and drain passages and an hydraulic unit connected to the housing and to an internal movable shaft moving with two stops set apart a predetermined distance and between drain passage and outlet passage. A sealing flange is located around the movable shaft and disposed between the two stops. The stops are adjusted with respect to each other so that the sealing flange moves into sealing relationship with either the outlet or the drain passages. The movable shaft is adjusted to move linearly and freely through a central aperture located on the central area of the sealing flange. The movement of the shaft is limited to the distance traveled until one of the two stops pushes against the sealing flange in order to open either one of the outlet or drain passages and closing the other one of the passages. Controlling the period of time between the entering of pressurized fluid to the inlet passage of the three way valve from a source of pressurized fluid which flows through the inlet passage to the drain passage until the opening of the outlet passage and the closing of the drain passage is an important aspect of the present invention. This period of time is controlled by adjusting the distance between the two stops located on the movable shaft and the size of the passage of pressurized fluid located on the hydraulic unit. A control valve, preferably of a relatively small size, is connected to the pressurized fluid passage located on the hydraulic unit. The control valve is provided in order to control the size of the opening of the pressurized fluid passage and the period of time between the opening or closing of the pressurized fluid flow to the valve and the time of the opening or closing of the outlet or the drain passages. 
     The method and apparatus of the automatic three way valve described and claimed in the present invention are preferably for the use with filters using filter aid material, such as diatomaceous earth (DE), to prevent penetration of fine particles, usually sediments, to the filtered fluid area which would result in the filtered fluid being contaminated with the fine particles during the first stages of filtration when the cake of filter aid material has still not yet or not completely built itself up around the filter element. The present invention provides features allowing the fine particles to drain separately from the filtered fluid for a predetermined time. After the predetermined period of time has passed, the drain passage automatically closes and the flow of filtered fluid from the filter is directed through the outlet passage to a filtered fluid collection area, such as a pool. 
     In accordance with a broad aspect of the preferred embodiment of the present invention, there is provided a method and apparatus incorporating an automatic valve adapted to reduce the flow for a pre-determined time in order to assist the filter aid material in the filter to be distributed uniformly on the filter element surface area and automatically open the full flow after said filter aid material is uniformly distributed on the filter element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view illustrating an automatic three way valve constructed in accordance with the preferred embodiment of the present invention; 
     FIG. 2 is a sectional view taken along line  2 - 2  of the automatic three way valve illustrated in FIG. 1; 
     FIG. 2A is a schematic view an automatic three way valve constructed in accordance with the principles of the present invention connected to a pump and a filter; 
     FIG. 3 is a sectional view along the center of the automatic three way valve constructed in accordance with the preferred embodiment of the present invention; 
     FIG. 4 is a sectional view of an automatic three way valve constructed and illustrated in accordance with another preferred embodiment of the present invention; and 
     FIG. 5 is a sectional view of another embodiment of an automatic three way valve similar to the one illustrated in FIG. 4 but with a few distinctions. 
     FIG. 6 is a schematic view of an automatic valve constructed in accordance with the principles of the present invention connected to a pump and a filter. 
     FIG. 7 is a cross-sectional view illustrating an automatic valve constructed in accordance with the preferred embodiment of the present invention. 
     FIG. 8 is a cross-sectional view of an automatic valve constructed and illustrated in accordance with another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is now made to FIG. 1, FIG.  2  and FIG. 2A which illustrate an automatic three-way valve  2  constructed and operative as a preferred embodiment of the present invention. Automatic 3-way valve  2  is connected by a pressure line  3  to a pump  5  and by a line  7  to the outlet of a filter  9 , as shown in FIG.  2 A. Automatic 3-way valve  2  comprises housing  4  having inlet passage  6 , internal passage  8 , outlet passage  10  and drain passage  12 . Fluid entering inlet passage  6  of 3-way valve  2  from a line  7  connected to an external source, such as a filter outlet  11  of a filter  9 , can flow out from the 3-way valve through drain passage  12 . Drain passage  12  is constructed from a drain sleeve  14  forming a through passage  16  and a conically shaped flange  18  extending outwardly from drain sleeve  14 . Drain passage  12  is connected to housing  4  by compression ring  20  being threadably secured to the housing shoulder  26  by the threaded interconnection portion  22 . The conically shaped flange  18  is sealed between the compression ring  20  and the housing shoulder  26  by O-Ring  24  located between the conic flange  18  and housing shoulder  26 . A sealing flange  28  is typically provided with a sealing surface  29 , such as a rubber ring  30 . The rubber ring  30  is preferably constructed with a U shaped cross-section adapted to fit over the outer circumferential surface of sealing flange  28 . It is also within the scope of the invention to shape the rubber ring  30  with some other cross sectional configuration or to construct the ring of some other material. Sealing flange  28  is also provided with aperture  32  located generally at the center thereof. Sealing flange  28  is adapted to move linearly between internal passage  8  and drain passage  16  in order to open one passage while moving to close the other passage and vice versa. Linear movable shaft  34 , having first and second ends is located within the central area of 3-way valve  2  and extends through aperture  32 . Stops  36  and  38  are fixedly connected to linear movable shaft  34  and are disposed on either side of sealing flange  28 . The stops  36  and  38  are disposed a predetermined distance between each other and between themselves and the closest respective side of sealing flange  28 . The stops  36  and  38  are adapted to push flange  28  as shaft  34  moves in a linear direction to open either one of the two passages, internal passage  8  or drain passage  16  and to close the other of the passages. First end  40  of linear movable shaft  34  extends through and is supported by support bearing  42  connected to sleeve drain  14  by ribs  44 . Second end  46  of movable shaft  34  is connected to a support plate  48  located within hydraulic unit  50  which is connected to housing  4 . A compression ring  52  secures a first cap  54 , a diaphragm  56  and second cap  58  of hydraulic unit  50  by means such as with a threadable interconnection portion  60  to housing  4 . Diaphragm  56 , located between first cap  54  and second cap  58 , divides hydraulic unit  50  into first and second compartments  62  and  66 . First compartment  62 , located between diaphragm  56  and first cap  54 , is in flow communication with pressure passage  64 . The pressure passage  64  is adapted to take in pressurized fluid flowing from external source of pressurized fluid such as pump to compartment  62  in order to effect the movement of linear movable shaft  34  and to relief such pressure. Second compartment  66  provided with support plate  48  and bias spring  68  is located between diaphragm  56  and second cap  58 . Bias spring  68  compress support plate  48  in order to effect the movement of movable shaft to one direction. Compartment  66  communicate with relief passage  70  through elongated holes  72  located on shoulder  73 . Shoulder  73  located on one end of housing  4  and second cap  58  are sealed by O-Rings  74  disposed between said second cap and said shoulder. O-Rings  74  also seals between holes  72 . Linear movable shaft  34  moves back and forth through aperture  76  and O-Ring  78  both disposed generally at the center of second cap  58 . 
     Description of operation of the three way valve in accordance with the Embodiment of FIGS. 1,  2  and  2 A. 
     Fluid from external source such as outlet of a filter enters 3-way valve  2  through inlet passage  6  and exits the valve through drain  12  passage. Simultaneously pressurized fluid from a source such as a pump enters through passage  64  to compartment  62  and presses diaphragm  56 , support plate  48 , and movable shaft  34  against bias spring  68  in order to move movable shaft  34  through aperture  32  and stop  36  toward sealing flange  28 . Such movement continues until stop  36  pushes sealing flange  28  to open passage  8  and close passage  16  in order to allow the flow from inlet passage  6  to flow through passage  8  and then to outlet passage  10 . Such flow continues until the pressurized fluid to passage  64  is shut-off as a result of the shut-off of its source such as a pump. Then bias spring  68  pushes support plate  48  and moves movable shaft  34  to exhaust the pressurized fluid from compartment  62  out through passage  64  and to draw in air from the atmosphere to compartment  66  through passage  70 . Movable shaft  34  moves freely through aperture  32  and stop  38  moves toward flange  28  until the stop pushes sealing flange  28  to open passage  16  and close passage B. A person with technical skills will understand that the predetermined distance between sealing flange  28  and one of the stops  36  or  38  acts as a timer indicating the time of occurrence of either opening or closing of passages  8  or  16  after the beginning or the shut-off of flow entering 3-way valve  2 . The distance between the two stops  36  and  38  and the size of passage  64  establish the time period passing from the time of the opening or closing of an external source, such as the opening or shutting-off of the pump from the time of the opening or closing of one of passages  8  or  16 . 
     Reference is now made to FIG. 3 which illustrates another preferred embodiment of an automatic 3-way valve  302 , constructed and operative in accordance with the present invention, and similar to the embodiment of FIGS. 1,  2 , and  2 A. The portions of structural elements, of this second embodiment and the remaining embodiments, which are substantially identical to corresponding structure in the embodiment of FIGS. 1,  2 , and  2 A, as to the description of their function, their operation and their design is the same throughout the present specification. Automatic 3-way valve  302  includes a housing  304  having three passages. Fluid flows to 3-way valve  302  from an external source, such as the outlet of a filter, passes through inlet passage  306 , through passage  308  and finally out from 3-way valve  302  through drain passage  310 . Drain passage  310  is adapted to output fluid mixed with sediments, when necessary, from valve  302 . Outlet sleeve  314  has an outlet passage  312  at one end and an inlet passage  316  at the other opposite end. A conically shaped flange  318 , extending outward from outlet sleeve  314 , is disposed in abutting relation to housing shoulder  326  of housing  304  and is secured thereto by compression ring  320 . The compression ring  320  is secured, by conventional means such as threaded section  322 , in such a manner that O-Ring  324  seals between the housing shoulder  326  and conically-shaped flange  318 . 
     Sealing flange  328  is typically provided with a sealing surface, such as a rubber ring  330 . The rubber ring  330  is preferably constructed with a generally U shaped cross-section adapted to fit over the outer circumferential surface of sealing flange  328 . It is also within the scope of the invention to shape the rubber ring  330  with some other cross sectional configuration or to construct the ring of some other material. Sealing flange  328  is also provided with aperture  332  located generally at the center thereof. A sealing flange  328  is adapted to move linearly between passage  308  and passage  316  in order to open one passage and close the other passage and vice versa. Shaft  334 , having first and second ends  340  and  346 , is located in the central area of 3-way valve  302  and extends through aperture  332  located on flange  328 . Stops  336  and  338  are connected to movable shaft  334  and are located at a predetermined distance between each other and between themselves and from the closest side of flange  328 . Stops  336  and  338  are preferably positioned to press against flange  328  in order to move and open either passage  308  or  316  while beginning to move and close the other one. First end  340  of movable shaft  334  extends through support bearing  342  connected to drain sleeve  314  by ribs  344 . Second end  346  of movable shaft  334  is connected to support plate  348  located in a hydraulic unit  350  which is secured to housing  304 . Compression ring  352  secures first cap  354  of hydraulic unit  350 , diaphragm  356  and second cap  358  of hydraulic unit  350  to housing  304  by means such as threadable section  360 . Diaphragm  356 , located between first cap  354  and second cap  358 , divides hydraulic unit  350  into first and second compartments  362  and  366 . First compartment  362 , located between diaphragm  356  and first cap  354 , is in flow communication with a relief passage  364  extending through cap  354 . Relief passage  364  is adapted to pass fill and exhaust air between the compartment  362  and the atmosphere about the valve  302  during the movement of movable shaft  334 . First compartment  362  comprises also a support base  348  connected to movable shaft  334 . The support base  348  supports bias spring  368  and is adapted to press against support plate  348  in order to effect the movement of movable shaft  334  in one direction. Second compartment  366  is located between diaphragm  356  and second cap  358 . Second compartment  366  communicates with pressure passage  370  through elongated holes  372  located between second cap  358  and shoulder  373  located on housing  304 . A pair of O-rings  374 , located between second cap  358  and shoulder  373 , seal the second cap  358  to shoulder  373  and also to seal fluid in holes  372 . Second cap  358 , having an aperture  376  and O-Ring  378  located generally at the center thereof, is constructed to permit movable shaft  334  to move back and forth therethrough while still having a seal between the shaft  334  and the second cap  358  to prevent leakage therebetween. It is also in the scope of the present invention that passage  376  will be constructed without O-Ring  378 . 
     Description of operation of 3-way valve  304  with reference to FIG.  3 . 
     Fluid flow enters three way valve  304 , from a source such as an outlet of a filter, through inlet passage  306 , then flows through passage  308  and finally exits the valve through drain  310 . Simultaneously, fluid from a source of pressurized fluid, such as pump, enters through passage  370 , longitudinal holes  372  and into compartment  366 . The fluid in compartment  366  presses diaphragm  356 , support plate  348 , and movable shaft  334  against bias spring  368 . Linear movable shaft  334  moves freely through aperture  332  until stop  338  pushes flange  328  to open passage  316 . Further movement of shaft  334  causes flange  328  to close against passage  308  with seal  330  so that the fluid from inlet passage  306  would flow to outlet passage  312 . When pressurized fluid stops flowing as a result of shut-off of the source of pressurized fluid, such as a pump shown in FIG. 2A, bias spring  368  presses against support plate  348 , diaphragm  356  and movable shaft  334  to move stop  336  towards flange  328 . By this movement, air from the atmosphere surrounding valve  302  is drawn into compartment  362  through passage  364  and pressurized fluid is exhausted from compartment  366  through passage  370 . Movable shaft  334  moves freely through aperture  332  until stop  336  pushes flange  328  to open passage  308  and close passage  316 . The shaft  334  moves in this direction, in order to open drain passage  310  so that it can receive flow coming from inlet passage  306 , when the flow starts flowing from the external source. 
     Reference is now made to FIG. 4 which illustrates an automatic three-way valve  402  constructed and operative in accordance with another preferred embodiment of the present invention. Three-way valve  402  comprises a housing  404  assembled from first and second main parts  406  and  410 . First main part  406  has a flange  408  provided on its end and second main part  410  has a flange  412  provided on its end. First and second main parts  406  and  410  are connected to each other by conventional means, such as for example screws  414  which extend through flange  408  and flange  412 . Conically shaped flange  416 , having a passage  418  disposed substantially in its center, is secured at its circumference area between flange  408  and flange  412 . Inlet passage  420  of 3-way valve  402 , located in the second main part  410 , is adapted to receive fluid flow from an external source of pressurized fluid such as the outlet of a filter. Drain passage  422 , located in the first main part  406 , is adapted to output the flow of fluid, generally mixed with sediments, flowing from inlet  420 , and through passage  418  to a location outside of the 3-way valve. Outlet passage  424  and inlet passage  426  of outlet sleeve  428  are located at the end of second main part  410  of 3-way valve  402  and adapted to outlet fluid flow therefrom. Flange  430 , located between passage  418  and passage  426 , has a sealing ring  432  (preferably in U shape but can be shaped in other configurations) secured to its circumference surface and a throughbore or aperture  434  located substantially at the center of flange  430 . Flange  430  is adapted to move back and forth between passage  418  and passage  426  in order to open one passage and close the second one. Movable shaft  436 , having first and second ends, is located substantially at the center of 3-way valve  402  and extends through aperture  434  of flange  430  to transfer linear movement to the flange  430 . Movable shaft  436  is provided with two stops  438  and  440  connected thereon and located on both sides of flange  430  at a predetermined distance set so that when shaft  436  moves in one direction, stop  440  moves flange  430  away from inlet passage  426  and towards passage  418 , and when shaft  436  moves in the other direction stop  438  moves flange  430  to open passage  418  and close inlet passage  426 . Bearing  442  connected to outlet sleeve  428  by ribs  444  is adapted to support movable shaft  436  which extends through bearing  442  by its first end. Movable shaft  436  is adjusted to move freely through aperture  434  and transfer linear movement to flange  430  in such manner that the linear movement of shaft  436  only effects the movement of flange  430  when one of stops  440  or  438  pushes flange  430  in the direction that it is free to move. Piston  446 , with O-Ring  448  provided in its circumference area, is connected to second end (typically threaded) of movable shaft  436  by conventional means such as threaded nuts  450  and reciprocates in a cylinder  452 . Cylinder  452 , located in first main part  406 , is open at one end and is enclosed with a cap  454  having a relief passage  456 . The cap  454  is secured to the end of cylinder  452  by conventional means such as a threaded section  458 . Piston  446  is adjusted to move back and forth inside cylinder  452  and to divide the cylinder into two compartments  460  and  462 . Compartment  460 , located on one side of piston  446 , is in communication with relief passage  456 . The relief passage  456  is adjusted to ventilate air in or out from compartment  460  during the linear movement of piston  446 . Bias spring  461 , located within compartment  460 , is adapted to bias the linear movement of piston  446  in a first direction. Second compartment  462 , located at the other end of piston  446 , communicates with pressure passage  464  through longitudinal hole  466  located on ribs  468 . Pressure passage  464  is adapted to intake and exhaust pressurized fluid or gas to and from compartment  462 . The flow of pressurized fluid or air to compartment  462  is controlled by an external source of pressurized gas or fluid, such as pump, in order to provide linear movement of piston  446  in the second direction. On the opposite side of cap  454  is provided aperture  470  located on cylinder  452  adapted to allow for the intake and exhaust of gas or fluid through pressure passage  464  so that movable shaft  436  moves linearly back and forth through aperture  470 . 
     Description of the operation of alternative embodiment of a 3-way valve as illustrated in FIG.  4 . 
     Fluid flow from an external source such as the outlet of a filter enters valve  402  through inlet passage  420  and flows through passage  418  to exit through drain passage  422 . Simultaneously, pressurized fluid from a source of pressurized fluid, such as a pump (See FIG.  2 A), enters passage  464 , holes  466  and compartment  462  in order to drive piston  446  and movable shaft  436  against bias spring  461 . Movable shaft  436  moves freely through aperture  434  until stop  440  pushes against flange  430  to open passage  426  and close passage  418  so that the flow of pressurized fluid from inlet  420  is directed to flow through outlet passage  424 . Valve  402  remains in the same position until pressurized fluid to compartment  462  is shut-off as a result of a shut off of the external pressure source, i.e. the pump. Then, bias spring  461  presses piston  446  and linear movable shaft  436  to effect a movement of linear shaft  436  through aperture  434 . During the movement of shaft  436  and stop  438  toward flange  430 , pressure from compartment  462  is exhausted to the outside atmosphere through passage  464  while air is drawn into compartment  460  from the atmosphere through passage  456 . Movable shaft  436  continues to move freely through aperture  434  until stop  438  pushes against flange  430  to open passage  418  and close inlet passage  426 . This movement enables valve  402  to receive the coming flow from an external source such as the outlet of a filter through inlet passage  420  and then to direct the flow through passage  418  to drain  422 . 
     Reference is now made to FIG. 5 which illustrates an automatic three-way valve  502  constructed and operative in a manner similar to the preferred embodiment of the present invention, as shown and described with respect to the configuration shown in FIG. 4 with some small variations. Three way valve  502  has a housing  504  assembled from first and second main parts  506  and  510 , respectively. First main part  506  has a flange  508  provided on the end thereof and second main part  510  has a flange  512  provided on the end thereof. First and second main parts  506  and  510  are connected by means such as bolts  514  which interconnect flange  508  and flange  512 . Conically shaped flange  516 , having a passage  518  disposed substantially in its center, is secured by a section of its circumference between flange  508  and flange  512 . Inlet passage  520 , located in second main part  510 , is adapted to receive fluid flow from an external source of pressurized fluid such as an outlet of a filter into valve  502  so that the fluid flows and exhausts through drain outlet passage  524  located on the second main part  510 . Drain outlet passage  524  and drain inlet passage  526  of drain sleeve  528  are located in the end of second main part  510  and are adapted to drain fluid generally mixed with sediments from valve  502  when necessary. Sealing flange  530 , located between passage  518  and inlet drain passage  526  is provided with a sealing ring  532 , preferably with a U shaped cross section (but within the scope of the invention, to be shaped in other configurations, secured to the circumferential area of the sealing flange  530 . Flange  530  has an aperture  534  located substantially in the center thereof. Flange  530  is adapted to move back and forth between passage  518  and drain passage  526  in order to close one of passages  518  or  526  and open the other. Movable shaft  536 , having first and second ends, is located substantially at the center of valve  502  and extends with its first end through aperture  534  located on sealing flange  530 . Stops  538  and  540  are connected to the first end portion of movable shaft  536  on both sides of sealing flange  530  in such manner that when shaft  536  moves in one direction, stop  538  presses against and moves sealing flange  530  to open passage  518 . Further movement of the shaft  536  in the same direction causes sealing flange  530  to abut against and sealingly close passage  526 . When shaft  536  moves in the other opposite direction, stop  540  pushes sealing flange  530  to open drain inlet passage  526  and eventually sealingly close against passage  518 . Piston  546 , having a seal  548  provided on its circumference, is connected to a second end of movable shaft  536  by conventional means such as threaded nuts  550  which are threadably attached to movable shaft  536  so as to secure piston  546  thereto. Cap  554 , having a relief passage  556 , is connected to the end of cylinder  552  by means such as a threaded section  558 . Piston  546  is adjusted to move linearly back and forth inside cylinder  552  so as to divide cylinder  552  into two compartments  560  and  562 . Compartment  560 , located on one side of piston  546 , is in communication with a pressure passage  556  that is adjusted to receive or exhaust pressurized fluid to and from compartment  560  during the linear movement of piston  546 . The pressure is supplied to compartment  560  from an external source of pressurized fluid such as pump in order to effect the linear movement of piston  546 . Second compartment  562  is provided with a bias spring  563  abutted against the other, opposite side of piston  546  and is in flow communication with relief passage  564  through longitudinal hole  566  located on ribs  568 . Relief passage  564  is adapted to provide air flow to and from compartment  562  from the surrounding atmosphere. Aperture  570  with O-Ring  572  located on cylinder  552  is provided on the opposite side of cap  554  and adapted to allow movable shaft  536  to move linearly back and forth through aperture  570  and O-Ring  572 . Control valve  574 , located on cap  554 , is connected to passage  556  in order to reduce or increase the size of passage  556 . 
     Description of operation in accordance with FIG.  5 . 
     Fluid flowing from an external source, such as the outlet of a filter enters through inlet passage  520  of valve  502  and flows generally mixed with sediments outside the valve through drain passage  524 . Simultaneously, pressurized fluid enters passage  556 , flows through control valve  574  and into compartment  560  to press piston  546  and movable shaft  536  against bias spring  563 . Air from compartment  562  is exhausted to the atmosphere through relief passage  564 . Movable shaft  536  moves freely through aperture  534  until stop  538  pushes flange  530  to open passage  518  and move towards passage  526  and ultimately to close passage  526  in order to permit flow flowing from the inlet  520  through passage  518  to flow to outlet  522 . Such position of valve  502  remains until pressurized fluid coming to valve  502  stops as a result of shut-off of the source of pressurized fluid such as pump. When pressurized fluid stops flowing to the valve, bias spring  563  moves piston  546  and the movable shaft  536 . This in turn causes stop  540  to push flange  530  in order to first open drain inlet passage  526  and then subsequently, to close passage  518 . Fluid is relieved from compartment  560  through relief passage  556  and air is drawn into compartment  562  from the atmosphere through relief passage  564 . 
     Reference is now made to FIG. 6, illustrating a system  601  similar to the one illustrated in FIG. 2A but comprising an automatic two-way valve constructed and operative with another preferred embodiment of the present invention. System  601  comprises a two-way automatic valve  602 , filter  609 , and a reservoir such as a swimming pool (not shown). The valve  602  is in flow communication with filter  609 . Pressure passage  664  is adapted to receive pressure from filter outlet  611 , or valve inlet  606 , or pump  605  or other pressurized source in order to operate valve  602 . 
     It will be appreciated that the valve  602  may be located at the outlet  611  or the inlet  608  of the filter  609 . If the valve  602  is located at the filter outlet  611  (as shown in FIG.  6 ), then during operation of the system  601 , when pump  605  is in on position, the fluid flows to valve outlet  610 , via filter inlet  608 , filter  609 , filter outlet  611 , valve inlet  606 , through automatic two-way valve  602 , and transfers said fluid to reservoir such as swimming pool (not shown) via valve outlet  610 . If the valve  602  is located at the filter inlet  608 , then the valve outlet  610  is connected to the filter inlet  608  and fluid flows to filter outlet  611 , via valve inlet  606 , valve  602 , valve outlet  610 , filter inlet  608 , and filter  609 . It is noted that a check valve (or non-return valve) (not shown) may be installed in the valve outlet  610  so that once fluid has passed the check valve it is prevented from returning into the valve  602 . The structure and operation of valve  602  will be described in more detail with reference to valve  702  shown in FIG.  7 . 
     Reference is now made to FIG. 7, which illustrates a automatic valve  702  similar to the one described in FIG. 1 with the exception that valve  702  described in FIG. 7 is a two-way valve with other changes constructed and operative with a preferred embodiment of the present invention. Automatic two-way valve  702  comprises a housing  704 , inlet passage  706 , coupled usually to the outlet of the filter (for example, the filter  609  of FIG. 6) but can be coupled to other installations, internal passage  708 , and outlet passage  710 . Flange housing  718 , having stop support  712 , is located on one side of housing  704 , and secured to the housing shoulder  726 , by compression ring  720 , with screw  722 . Sealing flange  728 , having sealing such as a rubber  729 , and defining relatively small passages  727 , is located between inlet passage  706 , and internal passage  708 . Small passages  727 , defined in sealing flange  728 , are adapted to transfer for a pre-determined amount of time, such as 30 seconds, from the time at which the pump is opened or fluid is otherwise introduced into the filter, a relatively small amount of the fluid flowing from inlet  706 , through passages  727 , to outlet  710 , in order to minimize the flow through the filter. This enables the filter aid material (i.e., porous materials) such as diatomaceous earth in the filter to uniformly distribute on the filter element surface. This uniform layer of filter aid material increases the efficiency of filtration. Shaft  734  is coupled to support  748  by screw  746  and comprises first stop  736 , located on one side of seal flange  728 , and second stop  738 , located on the other side of flange  728 . Hydraulic unit  750  comprises first cap  754 , second cap  758 , and diaphragm  756 , located between said first and second caps all secured to housing  704 , by compression ring  752 , by means of screw  760 . First compartment  762  is located between first cap  754  and diaphragm  756 , and second compartment  766  is located between diaphragm  756  and second cap  758 . Passage  767 , located either on inlet passage  706 , or on any other place between the pump (not shown) and inlet  706 , is adapted to transfer pressurized fluid to first compartment  762  via control tube  765 A, flow reducer means  765 , and passage  764 , located on cap  754  of hydraulic unit  750 , and vice versa, in order to operate the automatic two-way valve  702 . Relief valve  769 , located on cap  754 , or on any other place in communication with compartment  762 , in order to rapidly relieve fluid from compartment  762  to rapidly close passage  708  by sealing flange  728 , before regeneration of the filter aid material. For further details relating to a regeneration operation, see U.S. Pat. No. 5,013,461, which is hereby incorporated herein by reference. 
     Description of operation in accordance with FIG.  7 . In FIG. 7, passage  708  is shown closed by sealing flange  728 . Fluid from a source such as pump (not shown) or filter (not shown) flows to valve inlet  706 , through passages  727 , and to valve outlet  710 . Simultaneously, fluid from inlet  706  flows to compartment  762  via control passage  767 , control tube  765 A, flow reducer means  765 , and passage  764 . Said pressurized fluid pushes against diaphragm  756  and support  748  which, in turn, pushes against bias spring  768 , inducing a linear movement forward (i.e., downward in FIG. 7) of diaphragm  756 , support  748 , shaft  734 , first stop  736 , and second stop  738 . Said movement continues until stop  736  pushes sealing flange  728  away from internal passage  708  to open passage  708  to enable full flow. When shut-off of the flow is necessary, the pump is shut off, causing the bias spring  768  to push rearward (i.e., upward in FIG. 7) support  748 , diaphragm  756 , shaft  734 , with first stop  736 , and second stop  738 . Simultaneously, fluid from first compartment  762  flows to valve inlet passage  706  via passage  764 , flow reducer means  765 , control tube  765 A, and control passage  767 , and air from the atmosphere enters second compartment  766  through relief passage  772 . Shaft  734 , with second stop  738 , continue their rearward movement and stop  738  pushes rearward sealing flange  728 , in order to close passage  708 . Relief valve  769  is adapted to quickly transfer pressurized fluid from compartment  762  to the atmosphere in order to expedite the closing of passage  708  by sealing flange  728  before regeneration of the filter aid material. 
     Referring now to FIG. 8, there is illustrated a sectional view of an automatic two-way valve  802  similar to the automatic two-way valve  702  of FIG. 7, with few changes constructed and operative with another preferred embodiment of the present invention. Automatic two-way valve  802  comprises hydraulic unit  804 , and housing  806 , coupled together by means such as screw  808 . Housing  806  defines an inlet passage  810  for incoming fluid, outlet passage  812  for outgoing fluid, and an internal passage  814  for transferring the fluid from inlet  810  to outlet  812 . Cap  818 , located on one side of housing  806 , and including shaft support  820 , is coupled to the housing  806  by screw  822 . Sealing flange  824  is shown adjacent passage  814 . Sealing flange  824  is adapted to open and close passage  814 . It will be appreciated that passage  814  may be located anywhere so long as it may be opened and closed and allow a relatively small flow between the inlet and outlet. Sleeve support  826 , provided on sealing flange  824 , is adapted to support and provide linear movement to sealing flange  824  by linear movement of the sleeve support  826  on shaft support  820 . Small passages  828 , defined in sealing flange  824 , reduce fluid flow from inlet  810  to outlet  812  for a pre-determined amount of time, such as 30 seconds, from the time at which the pump is opened or fluid is otherwise introduced into the filter, in order to minimize the flow through the filter. This enables the filter aid material to uniformly distribute on the filter element surface. Sealing flange  824  then opens passage  814  to permit full flow. Bias spring  830 , located between sealing flange  824  and cap  818 , is adapted to push sealing flange  824  in order to close passage  814 . 
     Hydraulic unit  804  includes diaphragm  836 , first cap  832  and second cap  834 . The diaphragm  836  is disposed between first cap  832  and second cap  834  and the diaphragm  836 , first cap  832  and second cap  834  are coupled together by screws  837 . Hydraulic unit  804  has first compartment  838 , located between first cap  832  and diaphragm  836 , and second compartment  840 , located between second cap  834  and diaphragm  836 . Plate support  842 , and bias spring  844 , located in second compartment  840 , are adapted to push diaphragm  836  (i.e., upward in FIG. 8) in order to drain the fluid from first compartment  838 . Shaft  846 , which penetrates through second cap  834 , has first and second ends  846   a  and  846   b , respectively. First end  846   a  is located in second compartment  840  and coupled to support plate  842 . Second end  846   b  is adapted to push sealing flange  824  in order to open passage  814  to enable full flow therethrough. O-Ring  848 , located on second cap  834 , around shaft  846 , is adapted to seal between shaft  846  and second cap  834 . Relief hole  850 , located in second cap  834 , is adapted to transfer air from the second compartment  840  to the atmosphere and vice versa. Control valve  852 , located on first cap  832 , is adapted to transfer pressurized fluid to and from first compartment  838  and inlet  810  via passage  854  and control pipe  855 . Handle  856 , located on control valve  852 , is movable between two positions, position A and position B. In position A, a relatively small orifice (not shown) communicates between first compartment  838  and passage  854  to transfer a relatively small amount of pressurized fluid from passage  854  to first compartment  838  in order to slow the movement of shaft  846 , and consequently, to delay the opening of passage  814 . When handle  856  is in position B, a relatively large orifice (not shown) communicates between first compartment  838  and passage  854 , or with the atmosphere, in order to quickly close passage  814  by sealing flange  824  before a regeneration operation of the filter aid material. 
     Description of operation in accordance with the preferred embodiment of FIG.  8 . 
     In FIG. 8, passage  814  is shown closed by sealing flange  824 . Handle  856  is in position A and, accordingly, pressurized fluid from an external source such as pump or filter (not shown) enters through inlet passage  810  and flows to outlet passage  812  via small passages  828 . This reduces the flow of fluid through the filter at the beginning of the filtration operation. Simultaneously, controlled pressurized fluid flows from inlet passage  810  to first compartment  838 , via passage  854 , control pipe  855 , and control valve  852 . Said controlled pressurized fluid pushes forward diaphragm  836 , support  842 , and shaft  846 , against bias spring  844 . This relatively slow movement continues until end  846   b  of shaft  846  pushes sealing flange  824  against bias spring  830 . This movement continues until passage  814  is fully opened to enable full filter capacity flow. When a regeneration operation is necessary in order to regenerate the filter aid material and renew the layer of porous particles of filter aid material on the surface of the filter element, the source of pressurized fluid such as pump is shut-off. Handle  856  is moved to position B in order to quickly drain second compartment  838 . Simultaneously, bias spring  830  pushes sealing flange  824  (i.e., upward in FIG. 8) to close passage  814 . A regeneration operation may then be performed in the filter. After the regeneration operation is finished handle  856  is moved to position A to minimize the control passage orifice and filtration operation resumes. 
     The automatic two-way valve in accordance with the present invention is constructed to uniformly distribute a layer of filter aid material on the filter element surface in order to increase the efficiency of the filtration. This is done by supplying a limited amount of fluid at the beginning of a filtration operation to enable the filter aid material to be distributed homogeneously on the surface of the filter element. After a pre-determined amount of time, such as 30 seconds, when a sufficient amount of filter aid material is uniformly distributed on the filter element, the valve automatically opens to enable full flow and resume full capacity of filtration. An additional benefit of the present invention is to minimize the penetration of fine particles through the filter element and into the reservoir such as a swimming pool at the beginning of a filtration operation (which may occur if the filter aid material is not yet, or inadequately, distributed on the filter element) by generating a relatively slower fluid flow in the filter at the beginning of filtration. The construction and operation of the two functions of the present invention increases the efficiency of filtration and saves money.