Methods and systems for irrigation at stabilized pressure

A method of irrigation comprises supplying water to an inclined irrigation pipe provided with a plurality of drippers such that a pressure at a highest level of the inclined irrigation pipe is at most 200 cm H2O.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to irrigation and, more particularly, but not exclusively, to method and system for irrigation at stabilized water pressure.

Drip irrigation is a watering method that utilizes pressurized water sources and drips water along a distribution pipe in a controlled manner.

Drip irrigation systems are considered to be more efficient than surface irrigation systems that typically convey water to fields in open canals. Surface irrigation systems require smaller investment and lower energy costs, and these systems typically employ high discharge at the inlet in order to irrigate efficiently and uniformly across a field so that water will reach the end of the field.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a method of irrigation. The method comprises supplying water to an inclined irrigation pipe provided with a plurality of drippers such that a pressure at a highest level of the inclined irrigation pipe is at most 200 cm H2O. According to some embodiments of present invention the method comprises stabilizing water pressure within the inclined irrigation pipe by at least one water pressure stabilizer such that the water pressure varies along a length of the inclined irrigation pipe by no more than 50%.

According to some embodiments of the invention the water pressure is from about 5 cm H2O to about 150 cm H2O at a highest level of the inclined irrigation pipe.

According to some embodiments of the invention the water is supplied a water distribution conduit.

According to some embodiments of the invention the water pressure stabilizer is connected to the water distribution conduit.

According to some embodiments of the invention the water pressure stabilizer comprises a tank having an entry port, a water shutter controlling water entry through the port, and a float element operatively associated with the water shutter in a manner that a change in a vertical position of the float element effects a rotation of the water shutter.

According to some embodiments of the invention the at least one water pressure stabilizer comprise a container, a water inlet, a water outlet and a float element disposed within the container below the water inlet to block the water inlet when a height of water within the container reaches a predetermined level.

According to some embodiments of the invention at least a portion of the float element floats above a surface of the water within the container.

According to some embodiments of the invention the float element is submerged under a surface of the water within the container.

According to some embodiments of the invention the method comprises at least one pressure reducing device mounted on the inclined irrigation pipe.

According to some embodiments of the invention there is a plurality of pressure reducing devices mounted on the inclined irrigation pipe, wherein a number of the pressure reducing devices is less than a number of the drippers.

According to an aspect of some embodiments of the present invention there is provided a method of irrigation. The method comprises supplying water to an inclined irrigation pipe provided with a plurality of drippers such that a pressure at a highest level of the inclined irrigation pipe is at most 90 cm H2O, wherein the water contains at least 70 mg per liter of total suspended solids when entering the drippers.

According to some embodiments of the invention the irrigation pipe has a length of at least 100 meters and diameter of at least 40 mm.

According to an aspect of some embodiments of the present invention there is provided a method of irrigation. The method comprises supplying water to an inclined irrigation pipe provided with a plurality of drippers such that a pressure at a highest level of the inclined irrigation pipe is at most 90 cm H2O, wherein the irrigation pipe has a length of at least 100 meters and diameter of at least 40 mm.

According to some embodiments of the invention at least one of the drippers comprises a water pathway that is peripheral with respect to a body of the dripper, and that allows water to flow at a plurality of directions at any point along a length of the dripper.

According to some embodiments of the invention the water pathway has an annular cross section.

According to some embodiments of the invention the water pathway has a polygonal cross-section.

According to some embodiments of the invention the supplying the water is directly from a water source opened to an environment and is devoid of filtration.

According to some embodiments of the invention at least one of the plurality of drippers is characterized by a pressure-discharge dependence which comprises a linear relation between a discharge rate at an outlet of the dripper and an inlet pressure at an inlet of the dripper, for inlet pressure of from about 10 am H2O to about cm 200 H2O.

According to some embodiments of the invention the linear relation is characterized by a coefficient of the inlet pressure which is from about 7 cubic centimeters per hour per cm H2O to about 40 cubic centimeters per hour per cm H2O.

According to some embodiments of the invention the coefficient is from about 7 cubic centimeters per hour per cm H2O to about 20 cubic centimeters per hour per cm H2O.

According to some embodiments of the invention the coefficient is from about 9 cubic centimeters per hour per cm H2O to about 12 cubic centimeters per hour per cm H2O.

According to some embodiments of the invention the linear relation is characterized by an offset parameter from about 0 to about 50 cubic centimeters per hour.

According to some embodiments of the invention the offset parameter first coefficient is from about 10 cubic centimeters per hour to about 40 cubic centimeters per hour.

According to some embodiments of the invention the offset parameter is from about 20 cubic centimeters per hour to about 30 cubic centimeters per hour.

According to some embodiments of the invention the outlet is non-circular.

According to some embodiments of the invention the outlet comprises two or more laterally displaced round shapes connected to each other to form a figure-of-eight shape.

According to some embodiments of the invention the outlet has an area of from about 0.3 square millimeters to about 65 square millimeters.

According to some embodiments of the invention the outlet has an area of from about 0.3 square millimeters to about 70 square millimeters.

According to some embodiments of the invention the dripper comprises a niche formed in an external surface thereof, and wherein the outlet is formed within the niche.

According to some embodiments of the invention the niche is non-circular.

According to some embodiments of the invention the niche has an area that is at least 10 times larger than an area of the outlet.

According to some embodiments of the invention the number of drippers per meter length of the inclined irrigation pipe of from about 1 to about 5.

According to some embodiments of the invention the irrigation pipe is inclined at a slope that varies by no more than 20% along a length of the irrigation pipe.

According to some embodiments of the invention the irrigation pipe is inclined at a varying slope selected such that a discharge rate along a length of the inclined irrigation pipe varies by more than 20% but no more than 50%.

According to some embodiments of the invention for at least one pair of drippers in the pipe, a ratio between a value of the slope at a location of a first dripper of the pair and a value of the slope at a location of a second dripper of the pair, is equal or approximately equal to an nth power of a ratio between distances of a lowermost point of the pipe from the first and the second drippers of the pair, wherein the n is from about 1.5 to about 4.5.

According to some embodiments of the invention the irrigation pipe is placed on a ground inclined along a direction, and wherein at least a portion of the irrigation pipe is at an acute angle to the direction, such that a slope of the portion is less than a slope of the ground.

According to some embodiments of the invention at least one of the drippers is located at a periphery of the irrigation tube, within an upper half of a traverse cross-section of the periphery, but away from a topmost location of the periphery.

According to some embodiments of the invention at least one of the drippers is located at a periphery of the irrigation tube, within an upper half of a traverse cross-section of the periphery, but away from a topmost location of the periphery.

According to an aspect of some embodiments of the present invention there is provided an irrigation system, comprises: an inclined irrigation pipe having a plurality of drippers configured to discharge water; a water pressure stabilizer configured for stabilizing water pressure within the inclined irrigation pipe such that the water pressure varies along a length of the inclined irrigation pipe by no more than 50%; and a water supply system configured to deliver water to the inclined irrigation pipe at a highest level of the inclined irrigation pipe at a pressure of at most about 200 cm H2O.

According to an aspect of some embodiments of the present invention there is provided an irrigation system, comprises: an inclined irrigation pipe having a plurality of drippers configured to discharge water; a water supply system configured to deliver water to the inclined irrigation pipe at a highest level of the inclined irrigation pipe at a pressure of at most about 90 cm H2O; and a water pressure stabilizer configured for ensuring that water pressure within the inclined irrigation pipe is 50 cm H2O or less at any location along the inclined irrigation pipe.

According to some embodiments of the invention the water pressure stabilizer comprise a container, a water inlet, a water outlet and a float element disposed within the container below the water inlet to block the water inlet when a height of water within the container reaches a predetermined level.

According to some embodiments of the invention the system comprises a pressure reducing device mounted on the inclined irrigation pipe and configured to reduce water pressure in the inclined irrigation pipe.

According to some embodiments of the invention the pressure reducing device comprises a water pathway that is peripheral with respect to a body of the pressure reducing device, and that allows water to flow at a plurality of directions at any point along a length of the dripper.

According to some embodiments of the invention the water pathway has a transverse cross-section selected from the group consisting of an annulus and a polygon.

According to some embodiments of the invention the system comprises a water distribution conduit.

According to some embodiments of the invention the water supply system comprises at least one of: a water reservoir, a water tank and a pump.

According to some embodiments of the invention at least one of the drippers is located at a periphery of the irrigation tube, within an upper half of a traverse cross-section of the periphery, but away from a topmost location of the periphery.

According to an aspect of some embodiments of the present invention there is provided a water irrigation dripper. The water irrigation dripper comprises a single unitary element having an external structure enclosing an internal structure to form a generally straight water pathway surrounding the internal structure in a space between the structures, the water irrigation dripper having at least one water inlet for providing water to the pathway, and at least one water outlet on the external structure.

According to some embodiments of the invention dripper is characterized by a volumetric flow rate that varies non-linearly as a power of a pressure P at the inlet. According to some embodiments of the invention the power is less than 1. According to some embodiments of the invention the power is more than 0.8.

According to some embodiments of the invention a coefficient of the variation is between 0.1 and 90, when the volumetric flow rate is expressed in cubic cm per hour, and the pressure P is expressed in cm H2O.

According to some embodiments of the invention the dripper comprises at least one additional water inlet, at an acute angle to the water pathway, to affect turbulence in the pathway.

According to some embodiments of the invention a length of the water pathway is from about 0.5 cm to about 10 cm.

According to some embodiments of the invention the length of the water pathway is from about 2 cm to about 5 cm.

According to some embodiments of the invention the length of the water pathway is from about 2 cm to about 4 cm.

According to an aspect of some embodiments of the present invention there is provided a water irrigation pipe system, comprises water irrigation pipe, and a plurality of drippers distributed along the water irrigation pipe and being configured to discharge water, wherein at least one of the drippers is located at a periphery of the irrigation tube, within an upper half of a traverse cross-section of the periphery, but away from a topmost location of the periphery.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to irrigation and, more particularly, but not exclusively, to method and system for irrigation at stabilized water pressure.

The inventors found that traditional drippers may clog when particles accumulate therein, and that this requires constant supervision and inspection of the irrigation field and may increase the operating expenditure. For example, drippers having a generally zigzag shaped water pathway decrease the velocity of the water passing therethrough. The zigzag-shaped pathway may create turbulence, which, in turn, causes energy loss.

The inventors further found that reducing the operating pressure can reduce or eliminate the need for a pump, which, in turn, can reduce energy costs.

The inventors of the present invention have therefore devised a system that is capable of providing drip irrigation at relatively low pressure, and that can, in some embodiments of the invention, use natural water for the irrigation, optionally and preferably without using any filtration. This is advantageous over commercially available drip irrigation systems that mandate use of filters and further mandate use of very high pressure (at least 300 cm H2O and oftentimes much higher pressures), in order to prevent clogging of the drippers. Drip irrigation using natural water and without filtration is advantageous since drip irrigation uses less water than surface irrigation, since natural water, unlike processed water, are oftentimes readily available close to the field, and since use of filters is cumbersome and increases the maintenance load on the operator (e.g., the need to repeatedly replace or clean the filter).

As demonstrated in the Examples section that follows (seeFIGS.23A and23B), the system of the present embodiments can provide drip irrigation without clogging even for water that contains large amount of suspended solids and that is considered water of very low quality.

FIGS.1A and1Bare schematic illustrations of an irrigation system300, in accordance with some embodiments of the present invention. In various exemplary embodiments of the invention irrigation system300operates at a low water pressure, e.g., less than 0.1 bar, more preferably from about 5 mbar to about 90 mbar, more preferably from about 5 mbar to about 80 mbar, more preferably from about 5 mbar to about 70 mbar, more preferably from about 5 mbar to about 60 mbar, more preferably from about 5 mbar to about 50 mbar, more preferably from about 5 mbar to about 40 mbar e.g., 30 mbar. Irrigation system300optionally and preferably comprises a water supply system302, which preferably supplies water at low pressure. Irrigation system300can also comprise an irrigation pipe304and one or more drippers306.

WhileFIGS.1A and1Bshow irrigation pipe304in a generally horizontal orientation, this need not necessarily be the case, since, in some preferred embodiments of the present invention, irrigation pipe304is inclined. System302can optionally and preferably be connected through a connector and/or valve360, optionally and preferably to one or more of water distribution conduits305. Alternatively or additionally, system302can be connected to one or more of a water reservoir, a water tank, a water container or a well.

In some embodiments of the present invention system300comprises a water pump362that delivers water to system302or water distribution conduits305or irrigation pipe304, as desired. System300optionally and preferably comprises one or more pressure sensors364that measure water pressure in irrigation pipe304. System300can further comprise a control system366for controlling the flow rate of the water supplied to irrigation pipe304. Control system366can include a circuit that is configured to transmit control signals to pump362or connector and/or valve360thereby to control the flow rate in pipe304. Optionally and preferably control system366receives sensing signals from sensors364and transmits the controls responsively to these sensing signals, so as to maintain the aforementioned water pressure in irrigation pipe304.

Drippers306can be attached to, integrated in, or located in the interior of, irrigation pipe304. In operation, drippers306discharge water through at least one water outlet314, to provide a flow of water, for example, to soil, ground, or furrow. Outlet314of dripper306can optionally and preferably be adjacent to a hole336in pipe304.

Two spatial relations between the drippers306and the irrigation pipe304are illustrated inFIGS.18A and18B, which are schematic illustrations of a transverse cross-sectional view of irrigation pipe304(at a plane that is perpendicularly to the longitudinal axis and the general direction of the flow of water within irrigation pipe304). The transverse cross-section includes an upper half307and a lower half309, where the terms “upper” and “lower” are with respect to the direction of the gravity, which is shown at341. The drippers306are typically located at the periphery of pipe304at the upper half307thereof. In the schematic illustration ofFIG.18A, the dripper306is located at the topmost region of the periphery of pipe304. A more preferred embodiment is illustrated inFIG.18B. In this embodiment, the dripper306is still located at the upper half307, however away from the topmost region at the periphery of pipe304, at an acute angle θ to the vertical direction341. Preferred value for the angle θ is from about 10° to about 70°, more preferably from about 20° to about 60°, more preferably from about 30° to about 50°.

Irrigation pipe304can be made of any suitable material known in the art to operate normally to withstand pressure of at least 1 bars, to withstand accidental pressures as a result of loads generated, for example, by overridden wheels of a vehicle, and/or to withstand weather conditions, such as rain, or high temperatures typically caused from heat generated by the sun. For example, suitable materials may be polyethylene, polypropylene, polyvinylchloride and other thermoplastic materials. Typically, irrigation pipe304has a diameter of from about 12 mm and to about 60 mm, and length of from about 5 to about 800 m.

In use of system300, water is supplied to the inclined irrigation pipe304to flow within pipe304and drip via drippers306. Optionally, the water is a natural water that contains at least M mg per liter of total suspended solids. In some embodiments of the present invention the water is not filtered prior to entering irrigation pipe304so that it still contains M mg per liter of total suspended solids within pipe304and within drippers306. Typical values of M include, without limitation, at least 70, or more preferably at least 80, or more preferably at least 90, or more preferably at least 100, or more preferably at least 110, or more preferably at least 120, or more preferably at least 130. Alternatively, M can be less than 50.

Drippers306are disposed along irrigation pipe304. A typical distance between two adjacent drippers along pipe304is, without limitation, from about 20 to about 100 cm.

Drippers306can be embodied in more than one way. In the representative example shown inFIG.1B, which is not to be considered as limiting, one or more, preferably each of, drippers306can be fixed on the inner wall of irrigation pipe304, and may comprise one or more water inlet312through which the water enters the dripper306, one water outlet314through which the water exits the dripper306, and a water pathway310through which the water flows from the inlet312to the outlet314. For example, a typical dripper306may include from about 1 to about 100 dripper inlets, and 1 dripper outlet.

Water pathway310is optionally and preferably peripheral with respect to a body of dripper306, and that allows water to flow at a plurality of directions at any point along a length of dripper306. Preferably water pathway310forms at least one two-dimensional surface within dripper306. In some embodiments of the present invention water pathway has an annular transverse cross-section (perpendicular to a longitudinal axis of dripper306), and in some embodiments of the present invention water pathway has a polygonal transverse cross-section.

The term “annulus” as used herein refers to any round shape that at least partially enclose an area, and that include the periphery of the area but does not include the center of the area and a region surrounding said center. The term “annular” describes an object (e.g., a cross-section) having a shape of an annulus.

Other geometrical shapes for the transverse cross-section of pathway310are also contemplated.

FIG.11illustrates dripper306according to another embodiment of the invention. In this embodiment, dripper306comprises a compact housing212made of a sturdy and non-corrosive material. The top surface214of dripper306defines two sets of inlets, each including one or more openings extending through the top surface214. The inlets are exposed to the irrigation water flowing through the inside of the irrigation tube.

The first inlet216preferably includes three openings. Water flowing into the first inlet216proceeds through the body of dripper306to an outlet (not shown). In traveling through dripper306to the outlet, water pressure is reduced and water flow is reduced to a trickle or drip flow rate. The three openings are preferably sufficiently small in diameter to perform a filter function for water flowing through the first inlet216, for example, to filter out debris or grit that might otherwise clog the interior of dripper306. The openings making up the first inlet216are optionally and preferably spaced in a triangular pattern to allow water to uniformly impact interior surfaces of dripper306. Although three equally spaced openings are shown in the preferred embodiment, other numbers and arrangements of openings may be utilized to form the first inlet216.

The second inlet218preferably including two openings spaced along a center axis bisecting the length of dripper306. Water flowing into the second inlet218optionally and preferably does not proceed through the body of dripper306but, instead, serves a pressure compensation function. Water flowing into the second inlet218accumulates in a chamber in the interior of dripper306, applying pressure to the chamber in an amount substantially equivalent to the pressure in the irrigation tube. Because water flowing through the second inlet218does not flow through dripper306, the openings of the second inlet218need not filter the inflowing water and the openings need not be small in diameter. Although two openings are shown in the preferred embodiment, as seen inFIG.11, other numbers and arrangements of openings may be utilized to form the second inlet218.

FIGS.12A and12Billustrate dripper306according to another embodiment of the invention. In this embodiment, dripper306comprises a compact housing which can be conveniently and economically formed from assembled plastic molded housing components. The housing includes a generally cup-shaped base20adapted for assembly with a cap22to form a substantially enclosed housing interior. In general terms, the flow channel14is defined by a channel pattern26formed in the base20, in cooperative relation with a resilient and flexible elastomeric valve member28. Water is supplied to the flow channel14via a water inlet30formed by the cap22, and water is discharged from the flow channel through the discharge outlet16formed in the base20. The geometry of the channel pattern26cooperates with the valve member28to define the three dimensional flow channel14for improved pressure drop between the inlet30and the outlet16.

Housing base20has an upwardly open, generally cup-shaped construction including a circular bottom or floor surface32joined at the perimeter thereof to a cylindrical upstanding outer wall34. The channel pattern26is formed on the floor32with a generally circular configuration arranged about the outlet16which may include a short downwardly projecting hollow stem36for press-fit attachment to discharge tubing (not shown), if desired. A plurality of spacer posts38are also formed on the base20to project upwardly from the floor32at the floor perimeter and terminate with upper ends disposed above the channel pattern26, but below the upper edge of the outer wall32.

The valve member28comprises a resilient disk having a size and shape to fit into the housing base20, with an outer margin of the valve member28fitting within the spacer posts38. The housing cap22is then assembled with the base20by press-fit mounting of the disk-shaped cap into the open end of the base, to seat the cap22against the upper ends of the spacer posts38. The cap22can be securely connected to the base20in a sealed manner by use of a suitable adhesive, or by ultrasonic welding or the like. When assembled, the housing base20and cap22defined an inlet chamber40(FIG.12A) within which the valve member28is retained with at least some floating movement in a position aligned over the channel pattern26. The water inlet30is formed in the cap22and is typically associated with an inlet stem42which may include a barbed construction for press-on puncture type attachment to the water supply hose12.

From flow channel14, the water enters the centrally located discharge chamber having a raised circular boss52projecting upwardly from the floor32of the housing base20to engage the valve member28. The boss52has an upwardly open discharge regulating groove54formed therein, for discharge flow of the water from the outlet chamber to the water outlet16.

FIGS.13A and13Billustrate dripper306according to another embodiment of the invention. The dripper306may be a molded plastic body that may be inserted into thin walled drip tape102, or any other type of water conduit such as an extruded hose, at regularly spaced intervals during or immediately following extrusion of the drip tape. Each dripper306may have a single outlet that may be positioned at an opening104that is cut or pre-formed in the wall of the drip tape during production. Water in thin walled drip tape102may enter the dripper306by passing through a filter at the dripper's sides or perimeter106. Because the filter area is in the dripper's sides or perimeter, the dripper306can provide a filter of large area relative to the size or thickness of the dripper306. For example, the dripper306in a preferred embodiment may have a thickness of about 3.5 mm, and a filter area of at least about 12 mm2.

In one embodiment, filtered water then passes through labyrinth108where water pressure is reduced. For example, water pressure may be reduced from the line pressure in the drip tape (e.g., 12 psi) to a substantially lower pressure. Water at the reduced pressure then may flow through outlet hole110near the dripper's first or outer face111welded or adhered to the drip tape wall.

In one embodiment, the dripper306is pressure regulated using diaphragm112at or adjacent the dripper's second or inner face114. Water pressure in the drip tape acts against the diaphragm to regulate the dripper's flow rate as water pressure changes within the water conduit.

Dripper306may include three parts, two body members122and124, and elastomeric diaphragm112. The dripper's first or outer face111may have one or more walls or surfaces that are welded, adhered to or otherwise bonded to the drip tape inner wall. The dripper306has a second or inner face114that may project inwardly toward the interior of the drip tape. The thickness of the dripper306between the first or outer face and the second or inner face is preferably less than about 5 mm, and most preferably less than about 3.5 mm. The filter area of the dripper306is entirely on the sides106or periphery of the dripper306, between the dripper's outer face111and inner face114.

In one embodiment, the filter area may be configured as a plurality of slots116through the sides of the dripper306which provide filtering inlets or passages for water in the drip tape to enter into the dripper306. Each slot116through the dripper's side walls may have dimensions that are small enough to block particles or debris from passing through the slot to the interior of the dripper306, while allowing a desired flow rate of water from the drip line into the interior of the dripper306.

For example, in one embodiment, the dripper306may be generally disc shaped, and each slot116may extend radially through the dripper's cylindrical side walls106, from the perimeter or outer surface to the interior of the dripper306. Dripper306may have 24 radial slots, each slot having a width of less than about 0.5 mm, and most preferably having a width of less than about 0.3 mm. The radial thickness of the dripper's side walls may be between about 0.5 mm and about 1.0 mm. The dripper's radius may be between about 3.5 mm and about 6.5 mm, and the dripper's outer circumference may be between about 10 mm and about 30 mm.

In one embodiment, the second or inner face114of the dripper306may have an opening118. Diaphragm112may be an elastic bladder that is positioned between body members122and124, while the diaphragm is directly exposed on one side to the water pressure within the drip tape or other water conduit where the dripper306is mounted. For example, the diaphragm may have a thickness of about 0.5 mm to about 0.75 mm, and a surface which is large enough to cover both pressure regulating chamber144and labyrinth108which is formed in second body member124on surface132.

In one embodiment, the diaphragm may be exposed to line pressure in the drip tape which may enter through opening118and directly act against the diaphragm, causing the diaphragm to flex as the water pressure at the diaphragm on the other side is decreased. If water pressure in the drip tape increases, the diaphragm may flex radially toward outlet110and away from the dripper's second or inner face, reducing the outlet flow from the dripper306.

In one embodiment, water acting against the diaphragm while passing through opening118does not also pass through a filter. Instead, the filter may be an array of slots116in the dripper's cylindrical side walls106, and are dedicated only for water entering the dripper's pressure reducing area, or labyrinth108.

In one embodiment, diaphragm112may be held in place by sandwiching outer portions of the diaphragm between first body member122and second body member124of the dripper306. The first and second body members may be engaged together with a snap or press fit. For example, the second member may be inserted into the first member, and may be held in place by shoulders126that extend inwardly from the dripper's side walls106. The inwardly facing shoulders may capture and hold the second member in place because the dimensions of the second member's outer rim or perimeter128may be slightly larger than the dimensions of shoulders126. Diaphragm112may be held between surface130of the first member and one or more walls132,134of the second member. Optionally, the shoulders and outer rim or perimeter may be tapered to facilitate ease of assembly. Additionally, portions of the diaphragm that are radially outside of opening118may be compressed axially by a tight or sealing interfit between the first and second body members.

In one embodiment, water entering the dripper306through the filter area in the dripper's sides may be collected in manifold flow channel136inside the filter area. For example, the manifold flow channel may be a passage radially within the filter area on the dripper's side walls106, and may be enclosed by the drip tape wall, surface138, and wall140that circumscribe exit pool146.

In various exemplary embodiments of the invention irrigation pipe304is arranged to compensate pressure losses in the drippers along the irrigation pipe. In operation, water supply system302delivers water to pipe304, optionally and preferably at a highest level of pipe304.

It was found by the Inventors that this results in a generally high water flow rate, and also maintains a generally uniform flow rate in all drippers306.

In some embodiments of the present invention control system366(e.g., shown inFIG.1A) ensures that water supply system302delivers the water to pipe304at a pressure of at most about 200 cm H2O (e.g., from about 5 cm to about 200 cm H2O), or at most about 150 cm H2O (e.g., from about 5 cm to about 150 cm H2O), or at most about 120 cm H2O (e.g., from about 5 cm to about 150 cm H2O), or at most about 90 cm H2O (e.g., from about 5 cm to about 90 cm H2O), or at most 80 cm H2O (e.g., from about 5 cm to about 80 cm H2O), or at most 70 cm H2O (e.g., from about 5 cm to about 70 cm H2O), or at most 60 cm H2O (e.g., from about 5 cm to about 60 cm H2O), or at most 50 cm H2O (e.g., from about 5 cm to about 50 cm H2O), and further or at most 40 cm H2O (e.g., from about 5 cm to about 40 cm H2O). For example, when supply system302is a pump and/or comprises a controllable valve (not shown), control system366can control the pump or valve to deliver the preferred pressure. Alternatively, water supply system302can be configured to the deliver the water at the aforementioned pressure without a control system (e.g., by a judicious selection of the outlet diameter and/or pressure within the water supply system302).

Drip irrigation systems involve investment costs and power consumption in high pressure (energy) and filtration systems to work efficiently. Surface irrigation systems typically employ high discharge at a water inlet in order to irrigate efficiently and uniformly using surface irrigation so that water will reach an end of the field. It was found by the inventors of the present invention that reduction of water amount by a steeper slope field may cause runoff, erosion and soil degradation.

Drip irrigation systems provide higher water uniformity across a field than surface irrigation due to reduced runoff and leaching, however, it was realized by the inventors of the present invention that the high pressure requirement causes high energy costs and high investment costs in filters, pumps, pressure regulators, and materials of irrigation pipe that can withstand high pressure. It was realized by the inventors of the present invention that drip irrigation systems that work at pressures between 0.05 to 0.1 bar cannot be applied in large commercial fields because without proper filtration the drippers tends to clog. A criterion for discharge variation in an irrigated field is typically 10% or less.

The inventors found that an irrigation system comprising an inclined irrigation pipe that is configured such that a water discharge along a length of the inclined irrigation pipe varies by or no more than about 50%, or no more than about 40%, or no more than about 30%, or no more than about 35%, or no more than about 20%, or no more than 18%, or no more than 16%, or no more than 15%, or no more than 13%, or no more than 12%, or no more than 10%.

As used herein, “water discharge” refers to a volume of water that exits the dripper per unit time.

The low variation of the water discharge may be achieved in more than one way. In some embodiments of the present invention the irrigation pipe is inclined at a varying slope, in some embodiments of the present invention the irrigation pipe is inclined at a fixed slope but one or more water pressure stabilizers are provided to stabilize the pressure along the irrigation pipe, and in some embodiments of the present invention the irrigation pipe is inclined at a varying slope and one or more water pressure stabilizers are further provided to stabilize the pressure along the irrigation pipe. The pressure stabilizer can be mounted on the irrigation pipe itself or, more preferably, it can be mounted on water distribution conduits305.

The present embodiments contemplate deployment of an irrigation pipe on the ground that is inclined, wherein the slope of the inclination of the irrigation pipe on the ground vary by no more than 50%, more preferably no more than 40%, more preferably no more than 35%, more preferably no more than 30%, more preferably no more than 20%, along the length of the pipe.

The present embodiments also contemplate configurations with large variations (e.g., variations of more than 60% or more than 70% or more than 80%) in the value of the slope. These embodiments are particularly advantageous when the pressure at the highest level of the irrigation pipe304is low (e.g., less than 100 cm H2O, for example, 90 cm H2O or less. For example, in experiments performed by the Inventors, successful irrigation was achieved with pressure of about 50 cmH2O at the highest level of the irrigation pipe304for a slope that varied from 0.15% at the highest level of the irrigation pipe304to 0.02% at the lowest level of the irrigation pipe304.

In some embodiments of the present invention irrigation pipe304is inclined at a gradually varying slope, and in some embodiments of the present invention irrigation pipe304is inclined at a slope that varies non-continuously.

Inclined irrigation pipe304can have any length. Preferably, but not necessarily, the inclined irrigation pipe has a length of at least 100 meters, more preferably at least 200 meters, more preferably at least 200 meters, more preferably at least 300 meters, more preferably at least 400 meters, more preferably at least 500 meters, more preferably at least 600 meters, more preferably at least 700 meters, e.g., 800 meters or more. In these embodiments, the inner diameter of irrigation pipe304is preferably at least 30 mm, more preferably at least 35 mm, more preferably at least 40 mm, more preferably at least 45 mm, more preferably at least 50 mm, more preferably at least 55 mm, e.g., 60 mm or more, so as to reduce or minimize variations in water discharge and consequent head losses along the length of irrigation pipe304.FIGS.16A-Cshow hydraulic head losses along 400 meter irrigation pipes inclined at a slope of 0.05%, for irrigation pipe inner diameter of 22 mm (FIG.16A), 45 mm (FIG.16B), and 35 mm (FIG.16C). In all cases, the hydraulic head at the highest point of the inclined irrigation pipe is 50 cm H2O (0.05 bars). As shown, higher inner diameter (FIGS.16B and16C) ensures a reduction in the hydraulic head loss along the length of the pipe.

FIG.2is a schematic illustration of irrigation system300, in embodiments of the invention in which a varying slope is employed. Irrigation system300can comprise water supply system302, one or more inclined irrigation pipe304and a plurality of drippers306(not shown, see, e.g.,FIGS.1A and1B). In the representative illustration ofFIG.2, which is not to be considered as limiting, the irrigation system300comprises a distribution conduit305into which water is discharged from system302. Conduit305is provided with holes344to which irrigation pipes304are connected with suitable connectors (not shown). The irrigation pipes304are optionally and preferably placed between furrows311that are typically used for flooding and are arranged in a slope330for compensating in losses in flow along the irrigation pipes304. Slope330can vary (gradually or non-continuously) along the irrigation pipes304.

For example, irrigation pipe304may be inclined at a gradually varying slope with a higher slope (in absolute value) at the beginning of the irrigation pipe304and a lower slope (in absolute value) at one or more location downstream pipe304. It was found by the Inventors that this can increase the water flow rate, and can maintain a generally uniform pressure (e.g., with tolerance of ±50% or ±40% or ±35% or ±30% or ±20% or less) in all drippers306. In some embodiments of the present invention irrigation pipe304is inclined at a gradually varying slope that is selected such that a water discharge along a length of pipe304varies by no more than about 50%, or no more than about 40%, or no more than about 35%, or no more than about 30%, or no more than about 20%, or no more than 18%, or no more than 16%, or no more than 15%, or no more than 13%, or no more than 12%, or no more than 10%.

It was realized by the inventors of the present invention that as water flows in inclined irrigation pipe304provided with a plurality of drippers306, there can be a pressure increase along a length of irrigation pipe304, which can cause water discharge in the drippers306to increase.

FIGS.3A-3Bare graphs of dripper pressure as a function of pipe length in a 200 m pipe with 25 mm diameter and a slope of 0.5% (FIG.3A), and the corresponding height of the pipe from its highest level (FIG.3B), as obtained in experiments performed according to some embodiments of the present invention. The pressure increased from about 0.5 m at the beginning of the pipe to about 0.8 m at its end.

To irrigate a field efficiently and uniformly, the pressure in the irrigation pipe is optionally and preferably decreased and/or stabilized so as to reduce the variation in water discharge along the pipe.

The inventors found that in an irrigation system comprising an inclined irrigation pipe provided with a plurality of drippers, the water pressure may be reduced and/or stabilized using one or more water pressure stabilizer distributed along the irrigation pipe304and/or the distribution conduit305.

It was found by the Inventors that this results in maintaining a generally uniform (e.g., with tolerance of ±50%, more preferably ±40%, more preferably ±35%, more preferably ±30%, more preferably ±20% or less) water flow rate in all drippers306.

In some embodiments of the present invention, a water pressure stabilizer ensures that water delivered by the water supply system to the inclined pipe at a predetermined water pressure (e.g., of at most about 200 cm H2O) at a highest level of the inclined pipe, is delivered along a length of the irrigation pipe, such that the water pressure along the pipe varies by no more than about 50%, or no more than about 40%, or no more than about 35%, or no more than about 30%, or no more than 20%, or no more than 18%, or no more than 16%, or no more than 15%, or no more than 13%, or no more than 12%, or no more than 10%.

The water pressure stabilizer can be of any type known in the art, including, without limitation, an electrically driven water pressure stabilizer, a mechanically driven water pressure stabilizer, etc. A representative example of a driven water pressure stabilizer400suitable for the present embodiments will now be described with reference toFIGS.4A-4C.

Each water pressure stabilizer receives water at a first pressure from the inclined pipe and/or distribution conduit of system300, and provides water at a stabilized pressure, that is typically less than the first pressure. Preferably, the water pressure stabilizer ensures that the stabilized pressure is within the working pressure range of the drippers. In a representative example, the water pressure stabilizer provides a stabilized pressure that does not vary by more than about 50%, or more than about 40%, or more than about 35%, or more than about 30%, or more than 20%, or more than 18%, or more than 16%, or more than 15%, or more than 13%, or more than 12%, or more than 10%, from a pressure within the range of from about 20 cm H2O to about 80 cm H2O or from about 20 cm H2O to about 70 cm H2O, or from about 20 cm H2O to about 60 cm H2O or from about 20 cm H2O to about 50 cm H2O, or from about 30 cm H2O to about 50 cm H2O.

FIGS.4A-4Care schematic illustrations of a water pressure stabilizer400for an irrigation system (e.g., inclined irrigation system300shown inFIG.2), in accordance with some embodiments of the present invention. Water pressure stabilizer400can comprise a container413(e.g., a tube, a tank, a conduit, etc.) having a float element415disposed therewithin. In use, container413is preferably positioned generally vertically (e.g., with tolerance of ±10°). Float element415can have any shape. Optionally and preferably has a shape that fits the internal wall of container413. For example, when the internal wall of container413is cylindrical, float element415can be shaped as a disk or a ball. Container413has a top end418, a bottom end419and at least one or more openings414for ventilation. Water pressure stabilizer400also comprises an inlet411for receiving water at the first pressure, and an outlet416providing water at the stabilized pressure.

Inlet411and outlet416of pressure stabilizer400can be connected to an inclined irrigation pipe, such as, but not limited to, inclined irrigation pipe304of system300, or a distribution conduit, such as, but not limited to, distribution conduit305of system300, for stabilizing the pressure in the respective pipe or conduit.

Inlet411is optionally and preferably connected to container413through an angular pipeline connector, e.g., as shown inFIGS.4A and4C.FIGS.4A and4Cillustrate embodiments in which inlet411is connected to the top 418 of the container413, andFIG.4Billustrates an embodiment in which inlet411is connected away from the top 418 of the container413, for example, at the side wall thereof. Inlet411may have a pipe and/or conduit having a diameter that may, optionally and preferably, be equal and/or smaller than the diameter of the irrigation pipe304(e.g., 25 mm), and corresponds to the flow rate through the stabilizer400.

The float element415can optionally and preferably be characterized by having a buoyance for generating upwards movement of the element415along the container413when at least one partially submerged in water in the container413, e.g., the float element415having a mass density that is lower than the mass density.

Water enters the container through inlet411at the first pressure, which is expressed by an equivalent water column height and is designated herein, hin. The pressure at the outlet416is also expressed by an equivalent water column height and is designated herein, hout.

When the float element415is in equilibrium, the sum of forces on the element415is zero (F=0). When the buoyance force is greater than the sum of the gravitational force and the force applied by the pressure above element415, float element415rises upwards as water is filled until equilibrium is reached. The dimensions of container413and the location of inlet411above float element415are preferably selected such that when the pressure at the outlet416reaches a predetermined pressure, float element415are blocks inlet411from intaking water to the container.

This can be expressed by the following mathematical equations:

The ventilation openings414are optionally and preferably located above the maximum level of the water surface, so that the pressure at the water surface level is atmospheric. Thus, the pressure at outlet416, hout, corresponds to the pressure at water level, H (e.g., hout=H).

The top of the container413can be positioned above ground level in a range of between 30 and 100 cm (e.g., between 30 and 50 cm).

FIG.4Bdisplays an additional embodiment of the water pressure stabilizer400, according to some embodiments of the invention, in which the float element415has a higher density than in the float element415in the example displayed inFIG.4A, however, still lower than water density. As the water level rises in the container413, additional force that can push the float element415upwards may be generated. In equilibrium, the water level in the pipe is the pressure houtat the container outlet416. The outlet416can be located at the bottom of the container413or at a certain height in the bottom portion of the container413, but below the inlet411.

This can be expressed by the following mathematical equations:

If the float element415does not touch the upper cone area in steady state (e.g., as shown in420inFIG.4B), all of the float element's415volume can be submerged according to the following mathematical equations:

FIG.4Cdisplays yet an additional embodiment of the water pressure stabilizer400, according to some embodiments of the invention, in which inlet411comprises a flexible tube417. As water fills the container413through the flexible tube417, the float element415rises upwards, causing the flexible tube417to fold and thus reduces flow through the flexible tube417. When the water level in the container413reaches a certain height, the float element415causes the flexible tube417to kink, so that the water flow into the container413is approximately zero.

An additional type of water pressure stabilizer400suitable for the present embodiments is illustrated inFIGS.22A-C, whereFIG.22Ais a horizontal cross-sectional view,FIG.22Bis a vertical cross-sectional view along the line A---A inFIG.22A, andFIG.22Cis a detailed view of the section marked “B” inFIG.22B. The pressure stabilizer400shown inFIGS.22A-Cis designed for maintaining a generally stable hydraulic head, and is particularly suitable for deployment at the water distribution conduit305, to stabilize the pressure of the water before entering the inclined irrigation pipes. In these embodiments, pressure stabilizer400comprises a water tank620, an entry port622through which water enters tank620and an outlet630through which water exit tank620into water distribution conduit305(not shown inFIGS.22A-C). In the illustration ofFIGS.22A-C, which is not to be considered as limiting, port622is provided as a conduit. A water shutter624is mounted on entry port622, by an axis626that allows shutter624to rotate. Optionally, pressure stabilizer400comprises a stopper element628, such as a pin or a screw that limits the rotation range of shutter624to less than 360°.

In some embodiments of the present invention axis626is at the center of shutter624, so that the pressure of water flowing through port622applies forces both on the upper surface and on the lower surface of shutter624, which forces cancel each other.

Pressure stabilizer400also comprises float element415that is positioned in association with shutter624, such that when the water level in tank620is raised, float element415applies force to shutter624to rotate and assume a more upright orientation, and when the water level in tank620is lowered, float element415releases the force from shutter624so that shutter624rotates to assume a less upright orientation. The amount of water entering tank620through port622is thus controlled by shutter624, wherein when the water level in tank620is raised shutter partially closes port622, and when the water level in tank620is lowered shutter reopen port622. This maintains a generally constant water height in tank620. It is not necessary for shutter624to hermetically seals port622since it is typically desired to maintain a generally constant water height only during irrigation. Thus, in some embodiments of the present invention water can enter tank620through port622even when shutter assumes an upright orientation.

The present embodiments also contemplate a configuration in which a pressure reducing device is used to decrease the pressure at one or more locations along the irrigation pipe without attempting to stabilize the pressure. Such configurations are typically realized when the pressure within the irrigation pipe tends to buildup downstream the inclined pipe. Preferably, the type and/or location of decrease the pressure along the irrigation pipe are selected to ensure that the pressure in the irrigation pipe is maintained at 50 cm H2O or less at any location along said inclined irrigation pipe.

FIGS.20A-Fand21A-B are schematic illustrations of water pressure reducing device600, which can be deployed according to some embodiments of the present invention within the irrigation pipe304for reducing the pressure within irrigation pipe304. Pressure reducing device600can comprise a tubular structure602and an elongated flow restriction element604formed in, or introduced into, the interior of tubular structure602. Element604serves for reducing the water pathway within tubular structure602, thereby to restrict the flow.

In the configuration illustrated inFIGS.20A-F, element604comprises an elongated rod606and a plurality of spacers608connected to rod606to ensure that rod606is spaced apart from the inner wall of tubular structure602. Spacers608can extend longitudinally and continuously along the entire length of rod606as illustrated inFIGS.20Band E. However, this need not necessarily be the case, since, for some applications, it may be desired to make the spacers non-continuous (e.g., one or more sets of discrete spacers distributed along the length of the rod606). The advantage of this embodiment is that it allows the flow vector to also have an azimuthal component in addition to the axial component.

In operation, water flows in a direction generally parallel to a longitudinal axis610of element604(or, when spacers608are discrete, with a component also in the azimuthal direction) within a water pathway612formed between element604and the inner wall of tubular structure602.FIGS.20A and20Dillustrate a transverse cross-sectional view of device600(perpendicularly to the longitudinal axis610and the general direction of the flow),FIGS.20B and20Eillustrate an isometric view of flow restriction element604, andFIGS.20C and20Fillustrate a longitudinal cross-section of device600(parallel to the longitudinal axis610and the general direction of the flow). The configuration inFIGS.20A-Cis suitable for lower pressures than the configuration inFIGS.20D-F, since it provides larger flow space612.

In the configuration illustrated inFIGS.21A-B, flow restriction element604is tapered away from the ends of tubular structure602towards the middle section of structure602. For example, flow restriction element604can have an hourglass shape or the like.FIGS.21A and21Billustrate an isometric view and a longitudinal cross-section of device600.

Other shapes for the flow restriction element604are also contemplated.

In some embodiments of the present invention there is a plurality of pressure reducing devices600mounted on inclined irrigation pipe304. Preferably, the number of pressure reducing devices600is less than the number of drippers on pipe304.

In embodiments of the invention in which a varying slope is employed, the varying slope is optionally and preferably selected such that for at least one pair of drippers in pipe304, more preferably for at least two pairs of drippers in pipe304, more preferably for at least three pairs of drippers in pipe304, more preferably for any pair of drippers in pipe304, the ratio between the slope S1at a location of one of drippers of the pair and the slope S2at a location of another one of the drippers of the pair, is equal or approximately equal to the nth power of the ratio between the distances of the drippers from the lowermost point of pipe304(e.g., the farthest point of pipe304from conduit305). Mathematically, this can be expressed as S1/S2∝[(L−l1)/(L−l2)]″, where L is the length of pipe304, l1is the distance between the highest point along pipe304and one of drippers of the pair, and l2is the distance between the highest point along pipe304and the other dripper of the pair. The value of the exponent n is preferably from about 1.5 to about 4.5, e.g., about 2 or about 3.

In embodiments of the invention in which a varying slope is employed, the varying slope is optionally and preferably provided by deploying an irrigation pipe along a direction different than the slope in the ground (e.g., unparallel to the slope of the ground). The varying slope can be provided by placing the irrigation pipe on a ground inclined along a direction, in which at least a portion of the irrigation pipe is at an acute angle to the direction, such that a slope of the portion is less than a slope of the ground.

Reference is made toFIGS.5A-Cwhich are schematic illustrations of a dripper306, according to some embodiments of the present invention. Dripper306optionally and preferably comprises a plurality of holes functioning as water inlets312. However, this need necessarily be the case, since, for some applications, the end of the dripper can serve as an inlet. Dripper306can be useful in irrigation systems such as, but not limited to, the irrigation systems illustrated above with reference toFIGS.3A,3BandFIGS.4A-C. Dripper306can be attached to, or located in, one or more irrigation pipes304. Dripper306can be integrated into irrigation pipes304during pipe manufacturing process.

In the representative illustration ofFIG.5A, dripper306is assembled from an external hollow element301, e.g., in a shape of a hollow tube; and having one or more water inlets312for intaking water into dripper306, and one or more water outlets314for discharging water from the dripper306. Water outlet314can have any shape, including, without limitation, a circular shape, an oval shape, etc. A preferred shape for outlet314is illustrated inFIG.19. In these embodiments outlet314comprises two laterally displaced round shapes connected to each other to form a figure-of-eight shape. The present embodiments also contemplate more than two laterally displaced round shapes wherein each round shape is connected to two more other round shapes, preferable to form a continuous opening. The distance between the centers of the round shape is preferably, but not necessarily, from about 0.1 mm to about 40 mm.

Dripper306also comprises an internal element303having a diameter that is smaller than the diameter of the external hollow element301, such that when the internal element303is inserted inside external hollow element301, a water pathway310is formed in a space therebetween. Pathway310can extend from one end321of dripper306to another end331of dripper306. End331is optionally and preferably closed. In various exemplary embodiments of the invention water pathway310is formed such that there is at least one inlet-outlet pair that is connected by a straight line that is within water pathway310. This allows at least a portion of the water to flow along a straight line from one or more of the inlet(s)312to one or more of the outlet(s) outlet314, and is unlike drippers having, for example, zig-zag or labyrinth pathways.

Herein “an inlet-outlet pair” is a pair that includes one of inlet(s)312and one of outlet(s)314.

Water inlets312can be in the form of a plurality of small cavities having a diameter from about 0.05 mm to about 1 cm and inter-inlet intervals of from about 0.01 mm to about 1 cm. Water outlets314are preferably configured to discharge water from the dripper to provide a desired discharge flow rate of water out from the dripper to the soil or ground. The hole diameter of the water outlets314is typically from about 0.5 mm to about 2 mm. Water outlets314of dripper306can optionally and preferably be in communication with a hole336located in the inclined irrigation pipe304(shown inFIG.1B).

According to some embodiments of the invention dripper306is characterized by a pressure-discharge dependence which comprises a linear relation between a discharge rate Q (water volume per unit time) at outlet314and an inlet pressure P at inlet312P, wherein P is in the range of from about 10 cm H2O to about 200 am H2O. This relation can be expressed mathematically as Q=a1P+a0, where a1is an inlet pressure coefficient and a0is an offset parameter. A typical value for a1is from about 7 cubic centimeters per hour per cm H2O to about 40 cubic centimeters per hour per cm H2O or from about 7 cubic centimeters per hour per cm H2O to about 20 cubic centimeters per hour per cm H2O or from about 9 cubic centimeters per hour per cm H2O to about 12 cubic centimeters per hour per cm H2O. A typical value for a0is from about 0 to about 50 cubic centimeters per hour, or from about 10 cubic centimeters per hour to about 40 centimeters per hour, or from about 20 cubic centimeters per hour to about 30 cubic centimeters per hour.

FIG.5Billustrates a longitudinal cross-sectional illustration of dripper306, according to some embodiments of the present invention, andFIG.5Cillustrates an exploded side view of external hollow element301(right side) and internal element303(left side), according to some embodiments of the present invention.

The dripper306may comprise an external hollow element301having a first end331, which may be closed. Internal element318, with a head328, may be inserted into the external hollow element301. Head328of internal element303preferably closes one end321of external hollow element301after these elements are assembled together. External hollow element301can have a plurality of water inlets312at one end317and one or more water outlets314at the other end319.

With reference toFIG.5A, an internal diameter dintis typically defined between the two farthest antipodal points on an outer wall318of internal element303. An external diameter dextis typically defined between the two farthest antipodal points on an inner wall322of external hollow element301. When the internal element303is introduced into the external hollow element301, a water pathway310is created having a width W. The width W is optionally and preferably set to provide a sufficiently narrow water pathway310and to provide a small hydraulic diameter (DH) for reducing flow within the dripper306.

The hydraulic diameter (DH) is a parameter that is defined as four times the ratio between a flow area A and a wetted perimeter of a conduit, P, as defined in Equation I:
DH=4A/P(EQ. I)

In EQ. I A can be the cross-sectional area of the water pathway310in dripper306and P can be the wetted perimeter of the cross-section, in which case DHis referred to as the hydraulic diameter of pathway310.

For example, when water pathway310has a circular shape, the hydraulic diameter according to EQ. I above is reduced to the diameter of the circle forming the pathway.

A typical hydraulic diameter of pathway310, suitable for the present embodiments is from about 50 μm to about 500 μm. Other values for hydraulic diameter are also contemplated, provided that clogging within the water pathway310is reduced or inhibited, as further discussed hereinbelow with reference toFIG.6.

When water pathway310has an annulus shape, the hydraulic diameter is defined as the width W of the pathway, which can be calculated as the difference between the internal diameter d501of external hollow element301, and the external diameter d508of internal element303, according to EQ. II:
DH=W=d301−d303(EQ. II)

It is appreciated that the water flow rate decreases in a channel as its hydraulic diameter decreases.

The Inventors of the present invention found that by utilizing a narrow hydraulic diameter dripper according to preferred embodiments of the present invention, particular at a low operating pressure, may provide a low discharge flow rate when exiting from dripper306. Small hydraulic diameter may be achieved by providing a sufficiently large relative surface area of the narrow water pathway310, and/or by reducing the energy of water flowing in the water pathway310, for example, by increasing friction for water flow of the narrow water pathway310of the dripper306. An enlarged relative surface area of water pathway310can be achieved, for example, by making shaped pathway. For example, the pathway can be shaped as a polygon (e.g., a triangle, a square, etc.). An enlarged relative surface area of water pathway310can alternatively or additionally be achieved by providing a sufficiently long pathway between the inlet312and outlet314.

Particle accumulation at the dripper entrance can cause clogging and reduced flow discharge, thus resulting in flow discharge decrease or no flow.

The advantage of having a pathway as described above can be better understood with reference toFIG.6which illustrates a perspective side view of dripper306according to some embodiments of the present invention. Shown is an obstacle350, such as a particle or an air bubble, in its water pathway310, which, in the illustrated embodiment, has an annulus shape. Obstacle350can be in contact with inner wall322of external hollow element301and outer wall318of internal element303of dripper306, thereby partially or even completely clogging a region pathway310. However, since pathway310is not one-dimensional, there are other alternative paths within pathway310allowing bypass routes331,332and333around any obstacle that may be inside dripper306. Moreover, the amount of particles entering the dripper may be reduced by providing dripper306with a narrow entrance. Water inlets304may be of a size of from about 50 μm to about 500 μm. Thus, pathway310is not completely blocked by obstacle350.

In some embodiments of the present invention there are multiple capillary water inlets312. Typically, but not necessarily, for example, between 1 and 100 capillary water inlets are employed. The advantage of having a multiplicity of capillary water inlets is that the capillary water inlets can serve as a filter for dripper306, and reduce the risk of dripper clogging.

According to some embodiments of the present invention, the hydraulic diameter DHis from about 0.01 to about 1 mm. According to some embodiments of the present invention the external hollow element301has an inner diameter of from about 0.5 mm to about 5 mm.

Cross-sectional area of the dripper suitable for the present embodiments can be from about 3 mm2to about 300 mm2, depending on the width of water pathway310. The water flow rate of water flowing through dripper306, is typically from about 100 ml/h to about 10,000 ml/h at a hydraulic pressure of from about 0.1 m H2O to about 2 m H2O. For example, a dripper of about 3 cm in length and an annulus about 100 μm in width can produce a flow rate of about 1400 ml/h at a pressure of 1.5 m H2O.

The outer surfaces of external301and internal 303 elements may be parallel to each other up to a tolerance of about 10%. The distance between water inlets312can be from about 0.5 to about 2 mm. The distance between water inlets312and water outlets314can be from about 1 to about 6 cm.

As may further be appreciated, irrigation system300, by employing the drippers of the present embodiments, and operating them at a low pressure may eliminate a need for pump12of the kind displayed inFIGS.1A-B, and as a result, irrigation pipes304of the present embodiments may be made of fewer and cheaper raw materials.

In addition, the Inventors found the dripper of the present embodiments allows particles to be washed out by water flowing inside. Even if particles are partially clogged within the dripper of the present embodiments, the partial clogging may unclog when clean water is provided to the dripper, by washing the particle away. As a result, the dripper of the present embodiments has natural, built-in, self-cleaning capabilities.

With reference now toFIGS.7A and7B, the plurality of drippers306in any one of the embodiments of the irrigation system described above can be positioned either horizontally or vertically relative to the position of the irrigation pipe304, as illustrated inFIG.7AandFIG.7B, respectively.

FIGS.8A and8Bare cross-sectional illustrations of partial water pathway inside a dripper306, according to some embodiments of the present invention.

As described hereinabove inFIGS.5A-5C, water pathway310is created by assembling the internal element303with the external hollow element301. Internal element303may have alternative cross-sections such by utilizing the water pathway310in a shape of a partial ring, namely, by partially utilizing at least a portion of the annulus310. Any of the components of dripper306may comprise molded plastic. Internal element303may be inserted into external hollow element301.

In some embodiments of the present invention one or more covers may be put on one or more sides of external hollow element301, thereby closing one or more of its ends.

FIGS.9A-Lare schematic illustrations showing cross-sectional views of dripper306, according to several embodiments of the present invention.FIGS.9A and9Billustrate a side view (FIG.9A) and a sectional view along the A---A line (FIG.9B) of dripper306in embodiments in which dripper306comprises diagonal holes in the sides and exit holes under a dressed head (the left side is not shown in the drawing).FIGS.9C and9Dillustrate a side view (FIG.9C) and a sectional view along the B---B line (FIG.9D) of dripper306in embodiments in which dripper306comprises elliptically shaped water inlet (see alsoFIG.10A, below) with a filter313.FIGS.9E and9Fillustrate a side view (FIG.9E) and a sectional view along the C---C line (FIG.9F) of dripper306in embodiments in which dripper306comprises an elliptically shaped water inlet without a filter (see alsoFIG.10B, below).FIGS.9G and9Hillustrate a side view (FIG.9G) and a sectional view along the D---D line (FIG.9H) of dripper306in embodiments which are similar to those shown inFIGS.9A and9B, except for a shorter distance between the dripper's end and the exit holes.FIGS.9I and9Jillustrate a side view (FIG.9I) and a sectional view along the E---E line (FIG.9J) of dripper306in embodiments in which are similar to those shown inFIGS.9C and9D, except that dripper306comprises diagonal holes under a cover.FIGS.9K and9Lillustrate a side view (FIG.9K) and a sectional view along the F---F line (FIG.9L) of dripper306in embodiments in which are similar to those shown inFIGS.9C and9D, except that the outer shape is tapered to reduce friction.

In some embodiments of the present invention the dripper comprises a niche346formed in the external surface of the dripper, for example, at the external hollow element301of dripper306, wherein the outlet314is formed within niche346. Preferably, but not necessarily, niche346is non-circular. The area of niche346is preferably at least 10 times larger than an area of outlet314.

The length of external hollow element301and internal element303may be between about 20 and 50 mm. The diameter of external hollow element301may be between about 1 and 10 mm, and the diameter of internal element303may be between about 0.5 and 9.7 mm. The size of inlet312and outlet314may be between about 0.5 and 5 mm. The height of “baths”346may be between about 100 and 500 micron larger than narrow space310and the width of narrow space310may be between about 50 and 400 micron.

It will be appreciated that although some of the drippers according to some embodiments of the invention, and their components that were described above are assembled from more than one element (e.g., two or three parts) and the water pathway310is created by assembling the elements, the drippers306according to some embodiments of the invention may also be manufactured in other configurations in which a dripper body is formed as a single unitary, preferably monolithic, element having an external structure301enclosing an internal structure303to form a water pathway in a space310therebetween (e.g., as shown inFIGS.10H-10K).

The dripper306has one or more water inlet312for intaking water into the dripper306, and one or more water outlets314, to provide a flow of water. Water outlet314can have any of the aforementioned shapes (including, without limitation, circular, oval, figure-of-eight shape, etc.). In some embodiments, the dripper has more than one water inlet312for intaking water into the dripper306, wherein one or more of the additional water inlets3121are at an acute angle to the water pathway310. The advantage of these embodiments is that the additional water inlets3121facilitate turbulence within the dripper306and therefore improve the discharge efficiency. For example, the turbulence can prevent particles from accumulating in water entry area of the dripper306. The additional inlets3121may be positioned on an outer surface of the external structure301of the dripper306. In some embodiments, dripper306does not include any inlet in an outer surface of the external structure301(e.g., as shown inFIGS.10I-10J). In some embodiments, dripper306includes one inlet3121in an outer surface of its external structure301(e.g., as shown inFIGS.10G-10H), or two inlets3121in an outer surface of its external structure301(e.g., as shown inFIGS.10K-10L).

According to some embodiments of the invention dripper306is characterized by a pressure-discharge dependence of bthpower of inlet pressure P at an inlet of the dripper and discharge rate Q (water volume per unit time) at outlet of the dripper. This relation can be expressed mathematically as Q=aPb, where a is an inlet pressure coefficient. When Q is expressed in cubic cm per hour, and P is expressed in cm H2O, the value of b is optionally and preferably from about 0.2 but less than 1, or from about 0.3 to about 0.95, or from about 0.4 to about 0.95, or from about 0.5 to about 0.95, or from about 0.5 to about 0.9, and the value of a is optionally and preferably from about 5 to about 100, or from about 6 to about 99, or from about 7 to about 98, or from about 8 to about 97, or from about 9 to about 96, or from about 5 to about 95, or from about 10 to about 90. The values of a and b can be selected by judicial design of the number of inlets and its or their angle relative to the flow direction within water pathway310.

It will be appreciated that although the drippers and their components that were described herein have a cylindrical shape, they may also be manufactured in other shapes such that the external hollow element and the internal element described herein may be in any shape or form, such as, ellipse, square, rectangular, triangular, hexagonal, octagonal, etc.

Alternatively or additionally, the dripper according to the present embodiments may have an elliptically shaped water inlet, or a plurality of such shaped inlets.

Alternatively or additionally, the dripper according to the present embodiments may have a water inlet having any geometric shape, such as square, rectangle, triangle and circle.

With reference toFIG.10A, there is illustrated a perspective side view of an assembled dripper306having an elliptically shaped water inlet3121according to some embodiments of the present embodiments. As shown, the water inlet is positioned perpendicular to the drip.

Reference is now made toFIG.10B, which displays a perspective side view of an assembled dripper306having an elliptically shaped water inlet3121and comprising a filter according to some embodiments of the present embodiments. The elliptical water inlet3121(or a plurality of such inlets) comprises a filter340in various possible shapes (grid, cross-sectional or longitudinal grooves). As shown, the water inlets3121are positioned perpendicular to the drip306.

In addition to the vertical elliptical inlet3121as displayed inFIGS.10A and10B, there are additional inlets, which are not vertical to the drip306, through which water enters when their flow direction is generally at an obtuse angle θ to the flow of water in the drip. Typical values of θ include, without limitation, from about 110° to about 155°, or from about 120° to about 145°, or from about 130° to about 145°, e.g., about 135°.FIGS.10C and10Dillustrate a cross sectional view (FIG.10C) and a perspective side view (FIG.10D) of an assembled dripper having an elliptically shaped water inlet3121and an additional water inlet3122oriented diagonally with respect to a normal to an outer surface of an external hollow element301according to some embodiments of the present embodiments.

The inlets reach a level where water enters the drip and creates turbulence that prevents particles from accumulating in the water entry area. The drip water entry area is the area where particles may accumulate and may cause a partial or complete blockage of the drip, such that if particles have been introduced into the drip306, then the particles may not accumulate and may exit through the outlet as a result of the dripper's three-dimensional shape and smoothness. The water inlets3122may be oriented in a diagonal position with respect to a normal to an outer surface of the external hollow element301, which may produce turbulent flow of water in entry to the dripper inlet.

FIGS.10E and10Fare schematic illustrations showing a perspective view (FIG.10E) and a cross sectional view (FIG.10F) of the assembled dripper in embodiments of the invention in which the internal element is held only from one side.

As described herein above, it was realized by the inventors of the present invention that drip irrigation systems work at pressures between 0.5 to 4 bar and cannot be applied in large commercial fields using a work pressure lower than 0.1 bar. The inventors devised an irrigation system having an irrigation pipe inclined at a slope that can be selected such that a water discharge along a length of the pipe varies by no more than about 50%, or no more than about 40%, or no more than about 35%, or no more than about 30%, or no more than 20%, or no more than 18%, or no more than 16%, or no more than 15%, or no more than 13%, or no more than 12%, or no more than 10%.

FIG.15is a graph plotting a difference in percentage between a dripper with high discharge to a dripper with low discharge as a function of a field slope for inlet heads about 20, 30, 50, 100 and 150 cm, with 4 drippers per meter, pipe length of about 150 m and diameter of about 25 mm, as obtained in experiments performed according to some embodiments of the present invention and listed in Table 1.

TABLE 1Dripper discharge variation coefficient along the pipeas a function of field slope and size of inlet headInlet head (cm)Slope (%)2030405006.156.016.7714.790.053.952.753.5313.200.110.227.164.7211.810.219.8415.499.879.750.534.5629.2721.519.550.7539.9335.0427.6512.32143.4739.1232.2415.511.548.4144.8438.8521.62

Pressure at the last dripper was set to an estimated value and the dripper discharge was calculated. The head loss to the next dripper was calculated and the head change due to the slope to determine the pressure at the inlet of that dripper. The discharge of the two drippers was summed and so forth to the beginning of the pipe. Microsoft Excel “goal seek” function was used to change the pressure at the last dripper to set the target inlet head according to Table I above. The field slope was varied to evaluate slopes for efficiently operating the irrigation system of the present invention given maximum discharge difference of 10%

The pipe slope can cause higher pressure at the end (depending on the slope), and thus, higher dripper discharge. The increased discharge towards the pipe end can cause lower discharge variability along the pipe and acceptable uniformity in yields.

The irrigation system according to the present invention can be designed to connect to existing agricultural water supply systems, which can be used for flood irrigation.

Field slope can be used as a design variable to directly influence the pipe pressure, and thus, the drippers' flow discharge along its length. The slope along the pipe can vary depending on the pipe length, the density of the drippers (number per tube length), and the water head at the inlet. As water flows in the pipe, there can be a pressure drop along the flow pathway due to friction, and therefore, there can be variations in drip flow.

FIGS.17A-17Care graphs of the inlet pressure as a function of the conduit length for a slope of 0° (FIG.17A), varying slope (FIG.17B), and slope selected to ensure a uniform flow rate (FIG.17C), as obtained in experiments performed according to some embodiments of the present invention.

As shown inFIG.17A, in a 200 m pipe without a slope (slope of 0°), the pressure decreased from 0.5 m at the beginning of the pipe to 0.16 m at its end. This pressure difference exhibits a difference of 67% in the flow rates. Head loss in the flow along the dripper can be calculated by the Darcy-Weisbach equation as described above.

Fields that are typically irrigated by flooding can have small slopes of between about 0.02% and about 1%. Therefore, in conventional dripping systems, where the working pressures are high of about 10-14 m, the slope has no significant effect, as the height differences are negligible relative to working pressures.

According to the system of the present invention, in which the working pressure can be close to zero, small height differences along the pipe length can have a substantial effect on the pipe pressure and the drippers flow rate. The slope330, S(l), can vary along the pipe to compensate for the pressure loss.

The slope at any point l along pipe304can be expressed mathematically as a slope function S(l). The slope function can be input to a controller of a shoveling tool, such as, but not limited to, a laser guided land-leveling system, to form a varying slope in a soil, and inclined irrigation pipe304with drippers306can be deploying, generally along the varying slope.

A representative slope function suitable for the present embodiments is:

where K is a dimensionless constant. Typically, K is from about 0.1 to about 0.5 or from about 0.1 to about 0.3, where L is the length of the irrigation pipe304, fdis a friction factor, q is a flow rate in irrigation pipe304per unit length, g is the gravitational acceleration, DHis a hydraulic diameter of said irrigation pipe304, and l is a distance along irrigation pipe304from the highest level thereof.

Another representative slope function suitable for the present embodiments is:

S⁡(l)=G⁢qαCγ⁢DHδ⁢(L-l)β(EQ.V)
where c is a smoothness coefficient of the pipe's material, and G, α, β, γ and δ and ε are constant parameters. A typical value for G is from about 9 to about 11, a typical value for any of α, β and γ is from about 1.2 to about 2.2, and a typical value for δ is from about 4 to about 5.5. In some embodiments of the present invention at least two, more preferably all, of α, β and γ have the same value.

Since the pressure loss is greater at the beginning of the pipe and gradually decreases along the pipe, there can be a steeper slope at the beginning of the pipe and can be more moderate along the pipe length. In some embodiments of the present invention the slope S is selected also based on the distance between drippers306. The flow rate can also be affected by the distance between drippers, since each dripper can reduce the volume of water flowing through the pipe.

At the beginning of the pipe, the water flows at a maximum flow rate, and when water reaches the first dripper after a distance x, the flow rate gradually decreases in accordance with the flow rate in the dripper and so on. In the last portion of the pipe (up to the last dripper) the flow rate in the pipe equals the flow rate in the last dripper.

In some embodiments, the variation of the slope of the irrigation pipe can be ensured, at least partially, by orienting at least a portion of the irrigation pipe at an acute angle with respect to a direction of the slope of the ground on which the pipe is placed, such that the slope of the portion is less than the slope of the ground. Mathematically, these embodiments can be described by the following slope function suitable:
S(α)=SXsin α+SYcos α  (EQ. VI)
where S(α) is the slope at a certain angle α, Syis the slope in the direction of water distribution conduits305, Sxis the slope in the direction perpendicular to the direction of water distribution conduits305, and a is measured in the plane of the field.

InFIGS.17B and17C, the slope can be determined so that the drip flow along the pipe is generally uniform (e.g., with tolerance of ±50%, more preferably ±40%, more preferably ±35%, more preferably ±30%, more preferably ±20% or less).FIG.17Bshows that uniform flow can be achieved by the slope shown inFIG.17C.

As used herein the term “about” or “approximately” refers to ±10%.

The term “consisting of” means “including and limited to”.

EXAMPLES

Dripper Flow Rate Stability and Resistance to Clogging

Experiments were conducted to test the discharge and resistance to clogging of the drippers of the present embodiments. The experiments were performed over a period of 4 months.

A first experiment was conducted with water containing 300 ppm of suspended particle concentration. Half of this amount was from sandy soil where 35% of the particles had a diameter larger than 150 μm. The other half was from loamy soil where 100% of the particles had a diameter smaller than 150 μm.

The soils were added to a first water tank and stirred with a submersible pump. From the first water tank, the water was transferred to a second water tank using a peristaltic pump operated to achieve a constant 300 ppm of suspended particle concentration.

The water in the second tank were stirred using a submersible pump to avoid precipitation of the particles in the tank. The hydraulic head at the exit from the second tank was about 46 cm. Drip irrigation using drippers that contained a pathway with an annular transverse cross-section in accordance with some embodiments of the present invention the present embodiments was applied once a day on workdays for about 8 hours.

The effect of irrigation with 300 ppm water on dripper discharge is presented in inFIG.23A, showing the dripper discharge as a function of the accumulated particle weight. Each point inFIG.23Arepresents the average of 32 drippers. After a month of daily irrigations, irrigation water with 300 ppm had no effect on dripper discharge.

In a second experiment, the suspended particle concentration was raised to 1000 ppm which corresponds to extremely high peaks in natural surface water. The experimental setup was similar to the setup for the first experiment. In addition to the drippers of the present embodiments that contained a pathway with an annular transverse cross-section (perpendicular to a longitudinal axis of the dripper), commercial labyrinth drippers were also used for comparison.

The results of the second experiment are shown inFIG.23B. A single point representing clean irrigation water is also shown and is the result of two weeks of daily measurements. These measurements are represented by a single point since the abscissa is the accumulated particle amount.

The higher particle concentration in the irrigation water caused a slight decrease in the discharge of the dripper of the present embodiments (from about 950 ml/h to about 750 ml/h). A particle that is temporarily static within the pathway of the dripper of the present embodiments blocks only a part of the flow path causing the water to bypass it until its release. This process of partial blocking and bypass is causing the slight discharge decrease. Total particle amount passing through a single dripper during the experiment was 170 gr. Stopping the water flow from the first tank to the second tank (hence reducing particle concentration in the irrigation water) caused an increase in dripper discharge to the original value of 950 ml/h without an increase in variability.

It is appreciated that irrigation water with suspended particle concentration of 300 and 1000 ppm are considered of very low quality and exist naturally for short periods of time after heavy rains or floods. If one assumes a constant particle concentration of 1000 ppm with an average irrigation of 4 mm per day and no particle precipitation, 170 gr of particles can pass through the drippers of the present embodiments over a period of 87 irrigation days.