Abstract:
A self-cleaning pressure compensating drip emitter for controlling fluid flow through a hole in an irrigation line includes an enclosing sidewall having two ends, and formed with a ledge between the ends. A cover extends from the sidewall to establish an antechamber between the ledge and the cover. An entrance allows fluid from the irrigation line to enter the antechamber with little pressure reduction. An outlet extends into a fluid chamber established between the ledge and the second end of the sidewall. An opening allows pressure reduced fluid from the irrigation line to enter the fluid chamber. A membrane is positioned on the ledge for movement between a flushing configuration at low line pressures and an operational configuration at higher line pressures. In the flushing configuration, the membrane allows fluid to flow from the antechamber to the fluid chamber and through the outlet for flushing the emitter. In the operational configuration the membrane seals against the ledge preventing flow from the antechamber to the fluid chamber, and interacts with the outlet to partially restrict flow from the fluid chamber though the outlet to provide a drip flow through the hole in the irrigation line.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to devices for use as drip irrigation emitters. More particularly, the present invention pertains to drip irrigation emitters that provide a substantially constant drip flow-rate over a wide range of line pressures. The present invention is particularly, but not exclusively, useful as a self-cleaning, pressure-compensating, irrigation drip emitter. 
     BACKGROUND OF THE INVENTION 
     Many plants require sub-surface irrigation for effective growth and function. In particular, for large commercial operations, localized irrigation that is characterized by the administration of water in the vicinity of each plant can effectively conserve water and help prevent soil erosion due to runoff. Further, localized, low-flow irrigation over a relatively long irrigation cycle can result in deep subsurface water penetration which is beneficial for plants. 
     For many years, drip emitters have been used for delivering localized, low flow irrigation to the roots of plants. Generally, in use, drip emitters are placed in fluid contact with a water feed line such as a half-inch diameter irrigation line. To accomplish localized delivery of water, some drip emitters rely on the use of one or more small orifices to create a drip flow. When used, such an orifice or restriction emitter reduces the water pressure and flow rate in the irrigation line to a lower pressure and lower flow rate for the water as it passes through the orifice. Specifically, the reduced pressure and flow rate is suitable for creating a drip flow. 
     Unfortunately, simple orifice or restriction emitters often become clogged due to particulates in the feed line or debris that enters the emitter from outside the irrigation line. Further, simple orifice or restriction emitters are not pressure compensating, and consequently, the flow of drips through the simple emitter varies as the pressure in the irrigation line varies. The pressure within an irrigation line may, however, vary for several reasons. For example, the supply pressure may vary over time due to changes in water demand. Also, when long irrigation lines are used, a pressure drop along the length of the irrigation line may occur due to the frictional forces presented by the irrigation line. Further, when irrigation lines are used on hilly terrain, the pressure within the line may fluctuate due to variations in hydrostatic pressure. Consequently, emitters that lack the ability to compensate for pressure variations may cause uneven watering and cause the irrigation system to be hard to control. 
     Heretofore, drip emitters containing a pressure compensating flexible membrane have been disclosed. In these emitters, one side of the membrane is exposed to irrigation line pressure, while the opposite side of the membrane is exposed to a reduced pressure. For example, the reduced pressure can be created by forcing a portion of the water from the irrigation line through a restrictor or labyrinth. This pressure differential on opposite sides of the membrane causes the flexible membrane to deform. In particular, the higher line pressure can be used to force the flexible membrane into a slot where reduced pressure water is flowing. As the line pressure increases, the membrane will be pressed further into the slot, decreasing the effective cross-section of the slot and thus restricting flow through the slot. As described further below, the result is a constant flow through the emitter over a range of line pressures. Unfortunately, the slot is subject to clogging in the same fashion as the simple orifice emitter. Further, the membrane is required to form a seal with the edge of the slot confining flow to the slot. Unfortunately, particulate buildup may also interfere with the membrane seal causing non-uniform flow. 
     One attempt to solve the problems associated with particulate buildup in a pressure compensating emitter uses the reduced-pressure water from the labyrinth to clean the slot and sealing surfaces during initial pressurization of the irrigation line. In particular, such an emitter is disclosed by Miller in U.S. Pat. No. 5,628,462 which issued May 13, 1997, entitled “Drip Irrigation Emitter,” in which a chamber is created between the slot and the membrane. For the emitter disclosed by Miller, during initial pressurization of the irrigation line, while the membrane is only slightly deformed, the chamber is flushed with reduced-pressure water delivered from the restrictor or labyrinth. As the line pressure increases, the membrane deforms, sealing off the chamber from reduced pressure water, and restricting flow through the slot. Unfortunately, the reduced pressure water may be ineffective in adequately cleaning the slot and membrane. 
     In light of the above it is an object of the present invention to provide devices suitable for the purposes of providing a constant drip flow in response to a varying line pressure without becoming clogged. It is another object of the present invention to provide a self-cleaning drip emitter that uses water that is not pressure reduced to self-clean the membrane and slot. Yet another object of the present invention is to provide an irrigation dripper which is easy to use, relatively simple to manufacture, and comparatively cost effective. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     The present invention is directed to a self-cleaning, pressure compensating drip emitter that is bonded to the inside wall of an irrigation line. The emitter includes an enclosing sidewall that extends from the inner wall of the irrigation line to a cover. The sidewall is formed with a ledge that is located between the cover and the inner wall of the irrigation line. A flat, flexible membrane having two opposed sides is positioned between the ledge and the cover. A fluid chamber surrounded by the sidewall is thus created between one side of the membrane and the inner wall of the irrigation line. Further, an antechamber surrounded by the sidewall is thus created between the ledge and the cover. The cover contains one or more holes to allow fluid communication between the lumen of the irrigation line and the antechamber. Consequently, one side of the membrane is in fluid communication with the fluid chamber and the other side of the membrane is in fluid communication with the lumen of the irrigation line. 
     Further, an outlet is provide for the fluid chamber to allow fluid to pass from the fluid chamber to the outside of the irrigation line. Within the fluid chamber, the outlet has an aperture where fluid can enter the outlet from the fluid chamber. The outlet is further formed with a valve seat surrounding the aperture, and the valve seat is formed with a slot. A valve may be mounted on the flexible membrane for cooperation with the valve seat to form a seal, and for cooperation with the slot to restrict a portion of flow within the slot. 
     Two passageways allow fluid from the lumen of the irrigation line to enter the fluid chamber for subsequent exit from the irrigation line through the outlet. The first passageway, or flushing passageway, is a direct passageway from the lumen of the irrigation line to the fluid chamber. Importantly, the flushing passageway first enters the antechamber from an entrance located in the sidewall between the ledge and the cover. The second passageway, or operational passageway, is formed as a labyrinth between the lumen of the irrigation line and the fluid chamber. Importantly, the operational passageway enters the chamber from an opening in the sidewall that is located between the ledge and the aperture of the outlet. The operational passageway reduces the pressure of the fluid from the irrigation line to create a drip flow during steady-state operational flow conditions. 
     During operation, fluid is supplied to the irrigation line from a fluid source. Initially, the pressure within the irrigation line is low as the fluid from the source flows into the irrigation line, displacing trapped air. Gradually the pressure in the line increases until a steady-state pressure is established in the irrigation line. During the initial pressurization of the irrigation line, the pressure on both sides of the flexible membrane is low and the flexible membrane does not deform or block either of the passageways. Consequently, fluid from the direct flushing passageway passes into the antechamber through the sidewall at the entrance. From the antechamber, the fluid passes between the ledge and the membrane and enters the fluid chamber where it effectively flushes any particulates from the chamber, valve seat, aperture, slot and outlet to the outside of the irrigation line. 
     As the pressure within the irrigation line increases, the differential pressure between the line pressure on one side of the membrane and the reduced fluid chamber pressure on the opposite side of the membrane becomes significant. As this differential pressure begins to increase, several events take place. First, under relatively small differential pressures, the membrane is forced against the ledge of the chamber creating a seal which prevents the fluid from flowing through the flushing passageway and entering the fluid chamber. 
     Next, further increases in pressure differential will cause the membrane to deform and collapse into the chamber, causing the valve to contact the valve seat. This partial blocking of the chamber and aperture will reduce the flow of fluid from the operational passageway through the chamber and into the outlet. Subsequent increases in pressure differential will cause the membrane to further deform resulting in the valve forming a seal with the valve seat. At these pressure differentials, flow is limited to fluid from the operational passageway flowing into the chamber and entering the outlet through the slot in the valve seat. Additional increases in pressure differential will force the valve into a portion of the slot, thereby partially restricting the flow of fluid through the slot. 
     In summary, as the pressure in the irrigation line increases, the differential pressure across the membrane will increase. As the differential pressure across the membrane increases, the membrane and valve will cause a series of restrictions within the chamber, with each restriction causing a further reduction of flow through the outlet. At the same time, the increases in line pressure will cause the pressure of the fluid entering the chamber from the operational passageway to increase. However, constant flow through the outlet is achieved in spite of the varying line pressure because the increased pressure in the operational passageway is offset by the restrictive effects of the membrane and valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
     FIG. 1 is a cross-sectional view of an emitter having features of the present invention mounted in the lumen of an irrigation line; 
     FIG. 2 is a perspective view in partial cross-section of a portion of an emitter having features of the present invention showing the fluid chamber, membrane and outlet; 
     FIG. 2A is an enlarged view of a portion of the emitter as indicated by line  2 A in FIG. 2, showing the beveled edge between the sidewall and the ledge; 
     FIG. 2B is an enlarged view as in FIG. 2A showing an alternate embodiment in which a lip is formed on the edge between the sidewall and the ledge; 
     FIG. 3 is a plan view of an emitter having features of the present invention showing the filter, a portion of the labyrinth, and the covers of the fluid chamber; 
     FIG. 4 is a perspective view of a portion of an outlet for the present invention showing the valve seat, aperture and slot; 
     FIG. 5 is a plan view of a portion of an outlet for the present invention showing the valve seat, aperture, and slot; 
     FIG. 6 is a perspective view in partial cross-section of a portion of an alternate embodiment of the present invention, corresponding to the side cross-sectional view of the device shown in FIG. 1, with the membrane removed to more clearly show the features of the fluid chamber; 
     FIG. 7 is a perspective view in partial cross-section of a portion of an alternate embodiment as shown in FIG. 6, with a membrane positioned on the ledge; 
     FIG. 8 is a cross-sectional view of the alternate embodiment shown in FIG. 7, showing the membrane as it is positioned during initial pressurization of the irrigation line; and 
     FIG. 9 is a cross-sectional view of the alternate embodiment as shown in FIG. 8, showing the membrane deformation that occurs in response to a large pressure differential between the lumen of the irrigation line and the fluid chamber. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, a self-cleaning, pressure compensating irrigation drip emitter in accordance with the present invention is shown and designated  10 . As seen in FIG. 1, the emitter  10  is shown installed in the lumen  12  of an irrigation line  14 . Further, portions of the emitter  10  are in contact with the irrigation line  14  thereby creating sealed fluid passageways such as exemplary passageway  13 . To create the contact between the emitter  10  and the irrigation line  14 , any method known in the pertinent art such as adhesive or thermal bonding may be employed. By cross-referencing FIGS. 1 and 2, it can be seen that the emitter  10  includes a flexible membrane  16  having a side  18  and an opposed side  20 . The flexible membrane  16  is positioned inside the irrigation line  14  at a distance from the inner wall  22  of the irrigation line  14  to create a fluid chamber  24  between the flexible membrane  16  and the inner wall  22 . For purposes of the present invention, the flexible membrane  16  can be made of any elastic material known in the pertinent art such as metal, rubber or plastic, and may include a protective coating. A sidewall  26  partially surrounds the fluid chamber  24 , extending from the inner wall  22  of the irrigation line  14  to covers  28   a,b  of the emitter  10 . The sidewall  26  and the other portions of the emitter  10  (except the flexible membrane  16  described above) are preferably made of molded plastic. The sidewall  26  is further formed with a ledge  30  between the covers  28   a,b  and the fluid chamber  24 . An antechamber  31  surrounded by the sidewall  26  is created between the covers  28   a,b  and the ledge  30 . As shown in FIG. 2A, the edge  32  between the sidewall  26  and the ledge  30 , is preferably beveled. Alternatively, as shown in FIG. 2B, a lip  34  can be formed between the sidewall  26 ″ and the ledge  30 ″. As shown in FIGS. 1 and 2, the flexible membrane  16  is positioned between the ledge  30  and the covers  28   a,b,  with the side  18  of the flexible membrane  16  in fluid communication with the fluid chamber  24 . By cross-referencing FIGS. 2 and 3, it can be appreciated that the covers  28   a,b  contain one or more holes  36   a,b  to allow for fluid communication between the lumen  12  of the irrigation line  14  and the side  20  of the membrane  16 . 
     By cross-referencing FIGS. 1 and 2, it can be seen that an outlet  38  is provided for the fluid chamber  24  to allow fluid to pass from the fluid chamber  24  to the outside  40  of the irrigation line  14 . As shown, the outlet  38  includes an aperture  42  where fluid can enter the outlet  38  from the fluid chamber  24 . The outlet  38  is further formed with a valve seat  44  surrounding the aperture  42 . As shown in FIG. 2, the valve seat  44  is a surface, and preferably has a conical shape. In the preferred embodiment, the surface of the valve seat  44  is formed with a slot  46 . As shown in FIGS. 4 and 5, the slot  46  is recessed from the surface of the valve seat  44  and may extend from the aperture  42  of the outlet  38  to the periphery  49  of the valve seat  44 . As further shown in FIGS. 4 and 5, the slot  46  may have a rectangular cross-section and may have a bottom  45  that slopes towards the outlet  38 . Preferably, the bottom  45  includes two segments  47   a,b,  each segment  47  varying in slope from the slope of the other segment  47 . Further, a conical shaped valve  48  may be mounted to the side  18  of the flexible membrane  16  for cooperation with the valve seat  44  to form a seal, and for cooperation with the slot  46  to partially restrict flow through the slot  46 . The valve  48  may be made from plastic, rubber or metal and may have a protective coating. 
     Two passageways allow fluid from the lumen  12  of the irrigation line  14  to enter the fluid chamber  24  for subsequent exit from the irrigation line  14  through the outlet  38 . The first passageway or flushing passageway  50 , is a direct passageway from the lumen  12  of the irrigation line  14  to the fluid chamber  24 . Importantly, the flushing passageway  50  enters the fluid chamber  24  from an entrance  52  located in the sidewall  26  between the ledge  30  and the covers  28 . By cross-referencing FIGS. 1,  2  and  3 , it can be appreciated the second passageway, or operational passageway  54 , is formed as a labyrinth between the lumen  12  of the irrigation line  14  and the fluid chamber  24 . Importantly, the operational passageway  54  enters the fluid chamber  24  from openings  56   a,b  in the sidewall  26  located between the ledge  30  and the aperture  42  of the outlet  38 . As shown in FIG. 2, two openings  56   a,b  into the fluid chamber  24  from the operational passageway  54  may be provided. Also important for the present invention, the operational passageway  54  is formed to provide a greater total pressure reduction for fluid flowing through it than the flushing passageway  50 . Any design features known in the pertinent art such as passageway length, cross section, obstacles or turns can be used to ensure that the operational passageway  54  reduces the fluid pressure in an amount greater than the corresponding pressure reduction in the flushing passageway. Further, as shown in FIGS. 1 and 3, the emitter  10  is formed with a filter  58  having a filter inlet  60  and a filter outlet  62 . The filter inlet  60  is in fluid communication with the lumen  12  of the irrigation line  14  and the filter outlet  62  is in fluid communication with the operational passageway  54 . 
     An alternate embodiment for the present invention is shown in FIGS. 6-9. It is to be appreciated that many of the structural features of the alternate embodiment are similar to features of the embodiment shown in FIG.  1 . For example, in the alternate embodiment, the emitter  10 ′ includes a flexible membrane  16 ′. Also, a sidewall  26 ′ that extends from a first end  63 ′ to a second end  64 ′ partially surrounds the fluid chamber  24 ′ and is further formed with a ledge  30 ′ between the cover  28 ′ and the fluid chamber  24 ′. Also shown, the ledge  30 ′ is formed with a first portion  65 ′ that extends into the fluid chamber  24 ′ from the sidewall  26 ′ and a second portion  66 ′ that extends from the first portion  65 ′. Also similar to the FIG. 1 embodiment, the flexible membrane  16 ′ is positioned between the ledge  30 ′ and the covers  28 ′. Still further, an outlet  38 ′ is provided for the fluid chamber  24 ′, and the outlet  38 ′ is formed with an aperture  42 ′ where fluid can enter the outlet  38 ′ from the fluid chamber  24 ′. Additionally, the outlet  38 ′ is further formed with a valve seat  44 ′ surrounding the aperture  42 ′, and the valve seat  44 ′ preferably has a conical shape and is formed with a slot  46 ′. 
     Unlike the embodiment shown in FIG. 1, the alternative embodiment does not include a conical shaped valve, but rather, the flexible membrane  16 ′ is used to create a seal with the valve seat  44 ′, and to partially restrict the flow through the slot  46 ′. Further, in the alternate embodiment, a channel  67 ′ is formed behind the ledge  30 ′ to interpose the ledge  30 ′ between the channel  67 ′ and the fluid chamber  24 ′. 
     The alternate embodiment also includes a flushing passageway  50 ′ which is formed as a direct passageway, and an operational passageway  54 ′ which is formed as a labyrinth. In the alternate embodiment, the operational passageway  54 ′ enters the fluid chamber  24 ′ from an opening  56 ′ in the sidewall  26 ′ located between the ledge  30 ′ and the aperture  42 ′ of the outlet  38 ′. Further, the flushing passageway  50 ′ enters the fluid chamber  24 ′ from an entrance  52 ′ located in the sidewall  26 ′ between the ledge  30 ′ and the cover  28 ′. As shown in FIGS. 6 and 7, the flushing passageway  50 ′ is in fluid communication with the channel  67 ′. 
     Referring now to FIG. 1, during operation fluid is fed into the lumen  12  of the irrigation line  14  from a fluid source (not shown). Initially, the pressure within the lumen  12  of the irrigation line  14  is low as the fluid from the source flows into the irrigation line  14  displacing trapped air. Gradually, the pressure will increase until a steady-state pressure is established in the lumen  12  of the irrigation line  14 . During the initial pressurization of the irrigation line  14 , the pressure on both sides of the flexible membrane  16  is low and the flexible membrane  16  does not deform or seal against any surfaces in the fluid chamber  24 . This low pressure state is shown in FIG. 2, and in FIG. 8 for the alternate embodiment. Further, at low initial pressures, the flexible membrane  16  does not block either of the passageways  50 ,  54  into the fluid chamber  24 . Consequently, fluid is able to travel through the flushing passageway  50  with little pressure reduction, and into the fluid chamber  24  where it effectively flushes any particulates from the fluid chamber  24 , ledge  30 , valve seat  44 , aperture  42 , slot  46  and outlet  38  to the outside  40  of the irrigation line  14 . Specifically, fluid from the flushing passageway  50  is able to flow in the direction of arrow  68 , between the ledge  30  and the flexible membrane  24  and into the fluid chamber  24 . In the alternate embodiment shown in FIG. 8, fluid from the flushing passageway  50 ′ first flows in the direction of arrow  70  into the channel  67 ′, where the fluid subsequently flows from the channel  64 ′ along a path between the ledge  30 ′ and the flexible membrane  24 ′ and into the fluid chamber  24 ′. 
     As the pressure within the irrigation line  14  gradually increases, the differential pressure between the line pressure on side  20  of the flexible membrane  16  and the reduced pressure in the fluid chamber  24  acting on the opposed side  18  of the flexible membrane  16  becomes significant. As this differential pressure begins to increase, several events take place. First, under small differential pressures, the flexible membrane  16  is forced against the ledge  30  of the fluid chamber  24  creating a seal that prevents fluid flowing through the flushing passageway  50  from entering the fluid chamber  24 . 
     Next, as shown in FIG. 1, further increases in pressure differential will cause the flexible membrane  16  to deform and collapse into the fluid chamber  24 , causing the valve  48  to come in contact with the valve seat  44 . This partial blocking of the fluid chamber  24  and aperture  42  will reduce the flow of fluid from the operational passageway  54  through the fluid chamber  24  and into the outlet  38 . Subsequent increases in pressure differential will cause the flexible membrane  16  to further deform resulting in the valve  48  forming a seal with the valve seat  44 . At these pressure differentials, flow to the outside  40  of the irrigation line  14  is limited to fluid from the operational passageway  54 . Specifically, fluid from the operational passageway  54  will flow in the direction of arrow  72  into the fluid chamber  24 . Then, the fluid will flow from the fluid chamber  24  to the outlet  38  through the slot  46  of the valve seat  44 . Finally, the fluid will flow through the outlet  38  in the direction of arrow  74  to the outside  40  of the irrigation tube  14 . Additional increases in pressure differential will force the valve  48  into a portion of the slot  46 , thereby partially restricting the flow of fluid through the slot  46 . In the alternate embodiment shown in FIG. 9, the flexible membrane  16 ′ forms a seal with the valve seat  44 ′ and may penetrate into the slot  46 ′ in response to large pressure differentials. 
     Pressure compensation is achieved as follows in the emitter  10  of the present invention. First, it is to be appreciated that as the pressure in the lumen  12  of the irrigation line  14  increases, the differential pressure across the flexible membrane  16  will increase. Also, as described above, as the differential pressure across the flexible membrane  16  increases, the flexible membrane  16  and valve  48  will cause the series of restrictions within the fluid chamber  24 , with each restriction causing a further reduction of fluid flow through the outlet  38 . At the same time, the increases in line pressure will cause the pressure of the fluid entering the fluid chamber  24  from the operational passageway  54  to increase. However, constant flow through the outlet  38  is achieved in spite of the varying line pressure because the increased pressure in the operational passageway  54  is offset by the restrictive effects of the flexible membrane  16  and valve  48 . 
     While the particular self-cleaning, pressure compensating, irrigation drip emitter as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.