US20020070297A1 - Self-cleaning, pressure compensating, irrigation drip emitter - Google Patents

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

• This application is a divisional of application Ser. No. 09/544,847, filed Apr. 6, 2000, which is currently pending. The contents of application Ser. No. 09/544,847 are incorporated herein by reference.[0001]
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.[0002]
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.[0003]
• 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.[0004]
• 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.[0005]
• 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.[0006]
• 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.[0007]
• 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.[0008]
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.[0009]
• 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.[0010]
• 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.[0011]
• 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.[0012]
• 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.[0013]
• 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.[0014]
• 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.[0015]
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:[0016]
• FIG. 1 is a cross-sectional view of an emitter having features of the present invention mounted in the lumen of an irrigation line;[0017]
• 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;[0018]
• FIG. 2A is an enlarged view of a portion of the emitter as indicated by[0019]line2A 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;[0020]
• 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;[0021]
• FIG. 4 is a perspective view of a portion of an outlet for the present invention showing the valve seat, aperture and slot;[0022]
• FIG. 5 is a plan view of a portion of an outlet for the present invention showing the valve seat, aperture, and slot;[0023]
• 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;[0024]
• 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;[0025]
• 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[0026]
• 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.[0027]
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[0028]10. As seen in FIG. 1, theemitter10 is shown installed in thelumen12 of anirrigation line14. Further, portions of theemitter10 are in contact with theirrigation line14 thereby creating sealed fluid passageways such asexemplary passageway13. To create the contact between theemitter10 and theirrigation line14, 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 theemitter10 includes aflexible membrane16 having aside18 and anopposed side20. Theflexible membrane16 is positioned inside theirrigation line14 at a distance from theinner wall22 of theirrigation line14 to create afluid chamber24 between theflexible membrane16 and theinner wall22. For purposes of the present invention, theflexible membrane16 can be made of any elastic material known in the pertinent art such as metal, rubber or plastic, and may include a protective coating. Asidewall26 partially surrounds thefluid chamber24, extending from theinner wall22 of theirrigation line14 tocovers28a, bof theemitter10. Thesidewall26 and the other portions of the emitter10 (except theflexible membrane16 described above) are preferably made of molded plastic. Thesidewall26 is further formed with aledge30 between thecovers28a, band thefluid chamber24. Anantechamber31 surrounded by thesidewall26 is created between thecovers28a, band theledge30. As shown in FIG. 2A, theedge32 between thesidewall26 and theledge30, is preferably beveled. Alternatively, as shown in FIG. 2B, alip34 can be formed between thesidewall26″ and theledge30″. As shown in FIGS. 1 and 2, theflexible membrane16 is positioned between theledge30 and thecovers28a,b,with theside18 of theflexible membrane16 in fluid communication with thefluid chamber24. By cross-referencing FIGS. 2 and 3, it can be appreciated that thecovers28a,bcontain one ormore holes36a, bto allow for fluid communication between thelumen12 of theirrigation line14 and theside20 of themembrane16.
• By cross-referencing FIGS. 1 and 2, it can be seen that an[0029]outlet38 is provided for thefluid chamber24 to allow fluid to pass from thefluid chamber24 to the outside40 of theirrigation line14. As shown, theoutlet38 includes anaperture42 where fluid can enter theoutlet38 from thefluid chamber24. Theoutlet38 is further formed with avalve seat44 surrounding theaperture42. As shown in FIG. 2, thevalve seat44 is a surface, and preferably has a conical shape. In the preferred embodiment, the surface of thevalve seat44 is formed with aslot46. As shown in FIGS. 4 and 5, theslot46 is recessed from the surface of thevalve seat44 and may extend from theaperture42 of theoutlet38 to theperiphery49 of thevalve seat44. As further shown in FIGS. 4 and 5, theslot46 may have a rectangular cross-section and may have a bottom45 that slopes towards theoutlet38. Preferably, the bottom45 includes twosegments47a,b,each segment47 varying in slope from the slope of the other segment47. Further, a conical shapedvalve48 may be mounted to theside18 of theflexible membrane16 for cooperation with thevalve seat44 to form a seal, and for cooperation with theslot46 to partially restrict flow through theslot46. Thevalve48 may be made from plastic, rubber or metal and may have a protective coating.
• Two passageways allow fluid from the[0030]lumen12 of theirrigation line14 to enter thefluid chamber24 for subsequent exit from theirrigation line14 through theoutlet38. The first passageway or flushingpassageway50, is a direct passageway from thelumen12 of theirrigation line14 to thefluid chamber24. Importantly, the flushingpassageway50 enters thefluid chamber24 from anentrance52 located in thesidewall26 between theledge30 and thecovers28. By cross-referencing FIGS. 1, 2 and3, it can be appreciated the second passageway, oroperational passageway54, is formed as a labyrinth between thelumen12 of theirrigation line14 and thefluid chamber24. Importantly, theoperational passageway54 enters thefluid chamber24 fromopenings56a, bin thesidewall26 located between theledge30 and theaperture42 of theoutlet38. As shown in FIG. 2, twoopenings56a,binto thefluid chamber24 from theoperational passageway54 may be provided. Also important for the present invention, theoperational passageway54 is formed to provide a greater total pressure reduction for fluid flowing through it than the flushingpassageway50. Any design features known in the pertinent art such as passageway length, cross section, obstacles or turns can be used to ensure that theoperational passageway54 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, theemitter10 is formed with afilter58 having afilter inlet60 and afilter outlet62. Thefilter inlet60 is in fluid communication with thelumen12 of theirrigation line14 and thefilter outlet62 is in fluid communication with theoperational passageway54.
• An alternate embodiment for the present invention is shown in FIGS.[0031]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, theemitter10′ includes aflexible membrane16′. Also, asidewall26′ partially surrounds thefluid chamber24′ and is further formed with aledge30′ between thecover28′ and thefluid chamber24′. Also similar to the FIG. 1 embodiment, theflexible membrane16′ is positioned between theledge30′ and thecovers28′. Still further, anoutlet38′ is provided for thefluid chamber24′, and theoutlet38′ is formed with anaperture42′ where fluid can enter theoutlet38′ from thefluid chamber24′. Additionally, theoutlet38′ is further formed with avalve seat44′ surrounding theaperture42′, and thevalve seat44′ preferably has a conical shape and is formed with aslot46′.
• Unlike the embodiment shown in FIG. 1, the alternative embodiment does not include a conical shaped valve, but rather, the[0032]flexible membrane16′ is used to create a seal with thevalve seat44′, and to partially restrict the flow through theslot46′. Further, in the alternate embodiment, achannel64′ is formed behind theledge30′ to interpose theledge30′ between thechannel64′ and thefluid chamber24′.
• The alternate embodiment also includes a flushing[0033]passageway50′ which is formed as a direct passageway, and anoperational passageway54′ which is formed as a labyrinth. In the alternate embodiment, theoperational passageway54′ enters thefluid chamber24′ from anopening56′ in thesidewall26′ located between theledge30′ and theaperture42′ of theoutlet38′. Further, the flushingpassageway50′ enters thefluid chamber24′ from anentrance52′ located in thesidewall26′ between theledge30′ and thecover28′. As shown in FIGS. 6 and 7, the flushingpassageway50′ is in fluid communication with thechannel64′.
• Referring now to FIG. 1, during operation fluid is fed into the[0034]lumen12 of theirrigation line14 from a fluid source (not shown). Initially, the pressure within thelumen12 of theirrigation line14 is low as the fluid from the source flows into theirrigation line14 displacing trapped air. Gradually, the pressure will increase until a steady-state pressure is established in thelumen12 of theirrigation line14. During the initial pressurization of theirrigation line14, the pressure on both sides of theflexible membrane16 is low and theflexible membrane16 does not deform or seal against any surfaces in thefluid chamber24. This low pressure state is shown in FIG. 2, and in FIG. 8 for the alternate embodiment. Further, at low initial pressures, theflexible membrane16 does not block either of thepassageways50,54 into thefluid chamber24. Consequently, fluid is able to travel through the flushingpassageway50 with little pressure reduction, and into thefluid chamber24 where it effectively flushes any particulates from thefluid chamber24,ledge30,valve seat44,aperture42,slot46 andoutlet38 to the outside40 of theirrigation line14. Specifically, fluid from the flushingpassageway50 is able to flow in the direction ofarrow63, between theledge30 and theflexible membrane24 and into thefluid chamber24. In the alternate embodiment shown in FIG. 8, fluid from the flushingpassageway50′ first flows in the direction ofarrow65 into thechannel64′, where the fluid subsequently flows from thechannel64′ along a path between theledge30′ and theflexible membrane24′ and into thefluid chamber24′.
• As the pressure within the[0035]irrigation line14 gradually increases, the differential pressure between the line pressure onside20 of theflexible membrane16 and the reduced pressure in thefluid chamber24 acting on theopposed side18 of theflexible membrane16 becomes significant. As this differential pressure begins to increase, several events take place. First, under small differential pressures, theflexible membrane16 is forced against theledge30 of thefluid chamber24 creating a seal that prevents fluid flowing through the flushingpassageway50 from entering thefluid chamber24.
• Next, as shown in FIG. 1, further increases in pressure differential will cause the[0036]flexible membrane16 to deform and collapse into thefluid chamber24, causing thevalve48 to come in contact with thevalve seat44. This partial blocking of thefluid chamber24 andaperture42 will reduce the flow of fluid from theoperational passageway54 through thefluid chamber24 and into theoutlet38. Subsequent increases in pressure differential will cause theflexible membrane16 to further deform resulting in thevalve48 forming a seal with thevalve seat44. At these pressure differentials, flow to the outside40 of theirrigation line14 is limited to fluid from theoperational passageway54. Specifically, fluid from theoperational passageway54 will flow in the direction ofarrow66 into thefluid chamber24. Then, the fluid will flow from thefluid chamber24 to theoutlet38 through theslot46 of thevalve seat44. Finally, the fluid will flow through theoutlet38 in the direction ofarrow68 to the outside40 of theirrigation tube14. Additional increases in pressure differential will force thevalve48 into a portion of theslot46, thereby partially restricting the flow of fluid through theslot46. In the alternate embodiment shown in FIG. 9, theflexible membrane16′ forms a seal with thevalve seat44′ and may penetrate into theslot46′ in response to large pressure differentials.
• Pressure compensation is achieved as follows in the[0037]emitter10 of the present invention. First, it is to be appreciated that as the pressure in thelumen12 of theirrigation line14 increases, the differential pressure across theflexible membrane16 will increase. Also, as described above, as the differential pressure across theflexible membrane16 increases, theflexible membrane16 andvalve48 will cause the series of restrictions within thefluid chamber24, with each restriction causing a further reduction of fluid flow through theoutlet38. At the same time, the increases in line pressure will cause the pressure of the fluid entering thefluid chamber24 from theoperational passageway54 to increase. However, constant flow through theoutlet38 is achieved in spite of the varying line pressure because the increased pressure in theoperational passageway54 is offset by the restrictive effects of theflexible membrane16 andvalve48.
• 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.[0038]

Claims (20)

What is claimed is:

1. An emitter for controlling fluid flow from an irrigation line through a hole in the irrigation line, said emitter comprising:

an enclosing sidewall surrounding a fluid chamber, said sidewall having a first end and a second end;

an outlet for fluid communication with the hole in the irrigation line, said outlet extending into said fluid chamber at said second end of said sidewall;

a membrane having a first surface and an opposed second surface, said membrane being positionable at said first end of said sidewall with said first surface facing said fluid chamber and said second surface exposed to fluid in said irrigation line;

at least one fluid passageway formed as a labyrinth for producing reduced-pressure fluid from fluid in the irrigation line; and

a plurality of inlets substantially equally spaced from each other around said outlet for delivering said reduced-pressure fluid to said fluid chamber to apply a substantially uniform pressure on said first surface of said membrane for deforming said membrane into engagement with said outlet to control flow through the hole of the irrigation line during operational irrigation.

2. An emitter as recited inclaim 1 wherein said outlet is formed with a valve seat having a slot, said valve seat and slot for engaging said membrane during operational irrigation to compensate for pressure variations in the irrigation line and maintain a substantially constant flow through said outlet.

3. An emitter as recited inclaim 1 wherein said at least one fluid passageway is one fluid passageway.

4. An emitter as recited in claim I wherein said plurality of inlets is two inlets.

5. An emitter as recited inclaim 1 wherein each said inlet is configured to deliver said reduced pressure fluid along a path that is substantially normal to said first surface of said membrane.

6. An emitter as recited inclaim 1 wherein said first surface of said membrane is formed with a substantially conical surface.

7. An emitter as recited inclaim 1 wherein said first surface of said membrane is formed with a substantially conical surface surrounded by a surface that is formed as a partial toroid.

8. A irrigation system comprising:

an irrigation line for holding fluid at a line pressure, said irrigation line formed with at least one hole;

an enclosing sidewall positioned in said irrigation line, said sidewall surrounding a fluid chamber and having a first end and a second end;

an outlet in fluid communication with said hole in said irrigation line, said outlet extending into said fluid chamber at said second end of said sidewall;

a membrane having a first surface and an opposed second surface, said membrane being positioned at said first end of said sidewall with said first surface facing said fluid chamber and said second surface exposed to fluid at said line pressure in said irrigation line;

at least one fluid passageway formed as a labyrinth for producing reduced-pressure fluid from fluid at said line pressure in the irrigation line; and

a plurality of inlets substantially equally spaced from each other around said outlet for delivering said reduced-pressure fluid to said fluid chamber to apply a substantially uniform pressure on said first surface of said membrane for deforming said membrane into engagement with said outlet to control flow through the hole of the irrigation line during operational irrigation.

9. A system as recited inclaim 8 wherein said outlet is formed with a valve seat having a slot, said valve seat and slot for engaging said membrane during operational irrigation to compensate for pressure variations in the irrigation line and maintain a substantially constant flow through said outlet.

10. A system as recited inclaim 8 wherein said at least one fluid passageway is one fluid passageway.

11. A system as recited inclaim 8 wherein said plurality of inlets is two inlets.

12. A system as recited inclaim 8 wherein each said inlet is configured to deliver said reduced pressure fluid along a path that is substantially normal to said first surface of said membrane.

13. A system as recited inclaim 8 wherein said first surface of said membrane is formed with a substantially conical surface.

14. A system as recited inclaim 8 wherein said first surface of said membrane is formed with a substantially conical surface surrounded by a surface that is formed as a partial toroid.

15. A method of irrigation, said method comprising the steps of:

providing an irrigation line for holding fluid at a line pressure, said irrigation line formed with at least one hole;

disposing an emitter in said irrigation line, said emitter having an enclosing sidewall that surrounds a fluid chamber and is formed with a first end and a second end, said emitter having an outlet in fluid communication with said hole, said outlet extending into said fluid chamber at said second end of said sidewall, said emitter having a membrane formed with a first surface and an opposed second surface, said membrane being positioned at said first end of said sidewall with said first surface facing said fluid chamber and said second surface exposed to fluid at said line pressure in said irrigation line, said emitter having at least one fluid passageway formed as a labyrinth for producing reduced-pressure fluid from said fluid at said line pressure in said irrigation line, said emitter having a plurality of inlets substantially equally spaced from each other around said outlet for delivering said reduced-pressure fluid to said fluid chamber to apply a substantially uniform pressure on said first surface of said membrane for deforming said membrane into engagement with said outlet to control flow through the hole of the irrigation line during operational irrigation; and

filling said irrigation line with fluid until said fluid in said irrigation line is at said line pressure.

16. A method as recited inclaim 15 wherein said outlet is formed with a valve seat having a slot, said valve seat and slot for engaging said membrane during operational irrigation to compensate for pressure variations in the irrigation line and maintain a substantially constant flow through said outlet.

17. A method as recited inclaim 15 wherein said at least one fluid passageway is one fluid passageway.

18. A method as recited inclaim 15 wherein said plurality of inlets is two inlets.

19. A method as recited inclaim 15 wherein said first surface of said membrane is formed with a substantially conical surface.

20. A method as recited inclaim 15 wherein said first surface of said membrane is formed with a substantially conical surface surrounded by a surface that is formed as a partial toroid.

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