Abstract:
Low-pressure drip irrigation system, comprising a distribution pipe made of thin-walled sleeve collapsible when empty and designed to operate under hydraulic head up to 3 m H 2 O, having a plurality of holes in the walls thereof, a plurality of branch tubes equipped with low-pressure drip emitters; and a plurality of connectors connecting the branch tubes to the holes of the distribution pipe. The sleeve material is opaque and reflecting the solar radiation so that the natural growth of microorganisms and algae in the irrigation water is suppressed, and the pipe is not heated more than 35° C. above the ambient air temperature. The irrigation system is assembled in the field from components of a kit by deploying the distribution pipe, filling it with water, cutting the holes by means of a special hand-held tool, inserting the connectors into the holes, and assembling the branch tubes with the connectors.

Description:
[0001]     This is a division of co-pending parent application Ser. No. 10/431,575, filed May 8, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to drip irrigation systems, more particularly to low-pressure irrigation systems.  
       BACKGROUND OF THE INVENTION  
       [0003]     Known types of drip-irrigation systems use pressurized water sources of about 2 ata and more. Distribution pipes, fittings and valves in such systems are made of strong and relatively thick plastic materials. These systems are essentially independent on the field topography. However, pressure losses along their branching tubes with drip emitters are large. In order to achieve uniform dripping, special pressure-compensated emitters are used. These systems involve substantial investment costs and power consumption in operation.  
         [0004]     On the other hand, systems for flood furrow irrigation are traditionally applied on large areas. They include open distribution channels and branching furrows made in the fields. Since water in such system flows only due to the gravitation force, all channels and furrows are maintained with proper weak inclination. The flood irrigation requires less investment costs but the spending of water is huge. Moreover, the freely flowing water causes surface erosion and salinization of soils. Since recently, distribution channels are replaced by soft distribution pipes of large diameter with a plurality of openings which help to deliver irrigation water to the furrows without losses, pouring the water at the beginning of the furrow through the openings in the distribution pipe. These pipes are quite cheap and easily deployed; they may be used for one season and disposed of. However, water expenses still remain high.  
       SUMMARY OF THE INVENTION  
       [0005]     According to the present invention, there is provided a low-pressure drip irrigation system, comprising:  
         [0006]     a distribution pipe made of thin-walled sleeve collapsible when empty and designed to operate under hydraulic head up to 3 m H 2 O, having a plurality of holes in the walls thereof, and having an upstream end connectable to a source of water;  
         [0007]     a plurality of branch tubes equipped with low-pressure drip emitters; and  
         [0008]     a plurality of connectors, connecting the branch tubes to the holes of the distribution pipe.  
         [0009]     The irrigation system further comprises a gravity filtering tank connectable to a source of water, the tank being connected to the upstream end of the distribution pipe.  
         [0010]     The irrigation system is preferably controlled by an automated system for the regulation of the hydraulic head of the irrigation water in the gravity filtering tank. This automated system includes a pressure sensor disposed at the distal end of one of the branch tubes, and the hydraulic head is regulated in dependence on readings obtained from the sensor.  
         [0011]     The connectors used for assembling the above irrigation system have a nipple part for connecting to the branch tubes and a base part for connecting to the holes in the distribution pipe. The base part has a first and a second protruding collar and a narrow neck therebetween, the holes in the distribution pipe have diameters less than diameters of the respective necks. The connectors are each mounted in one of the holes with the first collar inside the distribution pipe so that the edge of the hole tightly embraces the neck of the connector, thereby securing the connector to the distribution pipe.  
         [0012]     As an alternative embodiment, the neck of the connector may comprise a threaded portion while the second collar is formed as a separate member with internal thread matching the threaded portion so that the second collar can seal the edge of the hole to the first collar by tightening up.  
         [0013]     According to a second aspect of the present invention, there is provided a thin-walled sleeve for use as distribution pipe, e.g. in the above irrigation system. The flow through the distribution pipe, under relatively low pressure and limited discharge through the drip emitters, is rather slow, typically between 0.02 and 0.8 m/s. Under such conditions, with conventional distribution pipes used in flood furrow irrigation, solar radiation in the field, penetrating through the pipe walls, promotes intensive growth of microorganisms and algae that are naturally present in the irrigation water. Such growth would soon lead to clogging of the drip emitters which usually have narrow water-passage labyrinths and small discharge openings. However, the distribution pipe of the present invention is made of opaque material that prevents light from entering into the pipe, thereby suppressing the growth of algae. Good results have been obtained with materials effectively stopping the visible and UV radiation and transmitting less than 5% of the IR radiation.  
         [0014]     Another problem related to the slow water flow in the distribution pipe is heating by the sun radiation. High temperature of the water in the pipe reduces the strength of the sleeve material and accelerates aging. For this reason, the sleeve material of the present invention is not only opaque but also is designed to reflect a major part of the sun radiation, about 20% and more. Thus, the distribution pipe, even with the small flow velocity mentioned above, is not heated to more than 30-35° C. above the ambient air temperature. Notably, this problem does not exist with higher pressure pipes and with the furrow irrigation pipes where flow velocity is much higher and the running water cools the pipes.  
         [0015]     The pipe material is extendable in the area of the holes about 1.6 times of their initial diameter, but should not be over-extendable, in order to hold the connectors up to internal pressure at least twice the operation pressure. The pipe material is also strong and deformable enough to endure overriding by wheeled vehicles with rubber tires when collapsed empty on non-rocky soil. Thus, it was found that material with total (elastic plus plastic) elongation before breaking of about 7.5 times would serve for more than one season of irrigation. Another feature of the material is that, when cut to obtain the holes, it provides accurate smooth edges of the hole.  
         [0016]     The distribution pipe is preferably made of plastic material, such as polyolefin blend comprising polypropylene or polyethylene, about 0.2 to 2 mm thick. The plastic material is stabilized for long-term solar heating and UV protection. The reflectivity and opaqueness to light in the visible, UV and IR range are achieved by suitable additives, such as dispersed silver micro-particles. The plastic pipe wall may comprise an outer reflective layer and an inner opaque layer.  
         [0017]     The distribution pipe may be manufactured with markings indicating places where the holes are to be made. The markings may comprise recesses providing stable positioning of a cutting tool, by which the holes are to be made.  
         [0018]     In an alternative embodiment, the distribution pipe may be manufactured with prefabricated holes for connecting the branch tubes. In such case, the holes may be equipped with annular rims made of rigid material, with thread or with bayonet locks for assembling to the connectors in the field. The annular rims may have an integral cover adapted for easy removal in the field, e.g. a notch around the rim.  
         [0019]     In yet another embodiment, the distribution pipe further comprises an internal filter membrane extending along the whole length of the pipe and dividing its cross-section into two chambers. The internal membrane filters the irrigation water passing between the two chambers.  
         [0020]     According to a third aspect of the present invention, a kit is provided for assembling an irrigation system in the field, comprising:  
         [0021]     a distribution pipe made of thin-walled collapsible sleeve with holes, or adapted for cutting therein holes, when filled with water,  
         [0022]     a plurality of connectors, adapted to connect the branch tubes to the holes cut in said distribution pipe; and optionally,  
         [0023]     a plurality of branch tubes equipped with low-pressure drip emitters.  
         [0024]     According to a next aspect of the present invention, there is provided a hand-held tool for cutting holes in the distribution tube of the above irrigation system, comprising a tubular cutter with thin annular cutting edge formed with plurality of teeth, and a handle. The tool cuts holes by urging the cutter to the distribution tube which is filled with water, and rotating the tool. The tool may be powered by means of an electric drive with accumulator battery.  
         [0025]     According to a still further aspect of the present invention, there is provided a method for assembly of a low-pressure drip irrigation system from the components of the above-described kit, in an irrigation field, the method comprising: 
        providing a source of water ensuring about 2 m H 2 O hydraulic head with respect to the field level;     deploying the distribution pipe in the field and connecting it to the source of water;     filling the distribution pipe with water;     assembling one branch tube with one connector;     if necessary, cutting a hole in the distribution pipe by means of the hand-held tool;     inserting the connector into the hole of the distribution pipe thereby attaching the branch tube to the pipe; and     repeating the three last steps for the next branch tubes.        
 
         [0033]     Thus, the present invention presents an irrigation system combining the economy, controllability and environmental friendliness of known drip-irrigation systems working at higher pressure, and the low investment costs of furrow irrigation systems. The system of the present invention is especially appealing by its simple method of assembly and the possibility to use the existing sources of water used in flood irrigation like artesian wells, surface run-off waters and others. Moreover, the irrigation system of the present invention can be directly assembled on existing fields to replace flood and furrow irrigation, with no additional earth-moving works.  
         [0034]     With the new system any flood furrow irrigation field can be upgraded for increasing irrigation uniformity from around 60% to over 80% (the 20-30% difference means saving of water and energy) in the new system, allowing to benefit from potentially higher and better yields. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]     In order to understand the invention and to see how it may be carried out in practice, preferred embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:  
         [0036]      FIG. 1  is a schematic plan of the low-pressure drip irrigation system of the present invention.  
         [0037]      FIG. 2  is a schematic side view of the drip irrigation system of  FIG. 1 .  
         [0038]      FIG. 3A  is a cross-sectional view of the distribution pipe filled with water, with fitted connector and branch tube  FIG. 3B  is a cross-sectional view of an alternative distribution pipe with internal filtering membrane.  
         [0039]      FIG. 4  is a perspective view of the connector used in the irrigation system of  FIG. 1 .  
         [0040]      FIG. 5  is a cross-sectional elevation of the filtering tank used in the irrigation system of  FIG. 1 .  
         [0041]      FIG. 6  is a perspective view, assembled and exploded, of a hand punch for cutting holes in the distribution pipe of  FIG. 3A .  
         [0042]      FIG. 7  is a series of sectional views of the distribution pipe of the present invention illustrating the process of cutting a hole and assembling a connector.  
         [0043]      FIG. 8  is a sectional elevation of an alternative connector with threaded collar.  
         [0044]      FIG. 9  is an axial sectional view of a hole in the distribution pipe, equipped with a rigid annular rim.  
         [0045]      FIG. 10  is a perspective view of a rim with a suitable connector, for alternative use in the distribution pipe shown in  FIG. 9 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0046]     With reference to  FIGS. 1 and 2 , there is shown a low-pressure drip irrigation system  10 , comprising a source of irrigation water  12 , gravitation filter tank  14 , outlet pipes  16 , distribution pipes  20 , connectors  21 , branch tubes  22 , and control system  24 .  
         [0047]     The source of irrigation water  12  in  FIG. 1  is an artesian well  26  with a pump  28  and an electric drive  30 , but may be any other suitable source. It is connected to the filter tank  14  which will be described in detail below. The filter tank  14  is connected to the pipes  20  by means of the outlet pipes  16 .  
         [0048]     With reference also to  FIG. 3A , the distribution pipe  20  has a plurality of holes  40  with edges  41  which are tightly fixed to base parts  42  of the connectors  21 . The pipes  20  are used in generally horizontal state, while the branch tubes  22  may be slightly inclined, so as to maintain approximately uniform head in all drip emitters.  
         [0049]     The distribution pipe  20  is made of thin-walled plastic collapsible sleeve designed to operate normally under hydraulic head H not exceeding 3 m H 2 O and to withstand accidental pressures up to about 6 m H 2 O. Typically, the distribution pipe  20  has diameter between 75 and 500 mm when full of water, while the wall thickness of the collapsible sleeve is between 0.2 and 2 mm.  
         [0050]     The plastic materials used for manufacturing of the sleeve of the distribution pipe are polyolefin blends stabilized for long-term solar heat and UV protection, comprising for example, polypropylene or polyethylene. The plastic material is largely opaque to most of the light in the visible, UV and IR range and has good reflectivity. The reflectivity is provided by using color additives, such as dispersed silver micro-particles. Also, the sleeve material may comprise an external light-colored reflective layer and an internal dark opaque layer.  
         [0051]     The material of which the thin-walled sleeve of the distribution pipe  20  is made is further capable of elastic expansion so as to allow penetration of the connector  21  when the latter is manually urged into the hole  40 . The necessary elastic expansion is about 1.6 times the initial diameter of the hole  40  which is provided by elastic (Young) modulus of the sleeve material about 0.9-1.2 N/mm 2 . However, the material should not be over-extendable, in order to hold the connectors at accidental deviations of the internal pressure. For example, a suitable pipe of 10 inch diameter, 0.8 mm wall thickness would hold connectors with neck diameter 18 mm at least up to pressure of 6 m H 2 O.  
         [0052]     The sleeve material endures overriding by wheeled vehicles with rubber tires when collapsed empty on sand, clay, mud or other non-rocky soil. It was found that a suitable sleeve material allowing about 250% elastic and 500% plastic elongation before breaking would serve for more than one season of irrigation. Furthermore, the material of the sleeve allows mechanical cutting of the holes  40  and obtaining accurate smooth edges  41  particularly when cut in the field, with the wall of the pipe  20  supported only by the water in the pipe.  
         [0053]     With reference to  FIG. 4 , the connector  21  has an axial bore  43 , a base part  42 , a nipple part  44 , and a locking ring  46 . The base part  42  comprises a frustum section  48  starting with an annular edge  49  at a front end of the axial bore  43  and smoothly flaring into a first collar  50 , a neck section  52  behind the first collar  50 , and a second collar section  54  behind the neck section  52 .  
         [0054]     The frustum part  48  is formed so as to expand gradually the edge  41  of the hole  40  when the connector  21  is urged by hand in to the hole (see also  FIGS. 7   e - h ). The neck section  52  is narrower than the first collar  50 , whereby it can accommodate the edge  41 , when the frustum part  48  is inside the distribution pipe. The neck  52  is however wider than the hole  40  in non-expanded state and provides a tight fit to the edge  41 . The second collar  54  is wider than the first collar  50  so as to prevent further penetration of the connector  21  into the distribution pipe  20 .  
         [0055]     The diameter D of the bore  43  is most often between 10 and 45 mm. The hole  40  and the elements of the connector are then preferably sized as follows: the hole  40  has diameter between 0.8 and 1.0D, the first collar  50  has diameter between 1.4 and 1.7D, the neck  52  has diameter between 1.1 and 1.3D, and the second collar  54  has diameter greater than 1.9D.  
         [0056]     The nipple part  44  is formed with a few steps  56  and slight flare towards the rear end of the bore  43  so as to hold tightly an inlet end of the branching tube  22  when forced over the nipple part.  
         [0057]     The locking ring  46  has diameter D 2  allowing passage over the widest step of the nipple part  44  but not allowing passage with the tube  22  on the nipple. Before assembling the tube  22  to the connector  21 , the ring  46  is placed on the nipple part  44  close to the second collar  54 . After the tube  22  is urged over the nipple part  44 , the locking ring  46  is moved back to the rear end of the bore where, due to the flare of the nipple, it locks on the tube  22  and secures it to the nipple.  
         [0058]     The branch tubes  22  are equipped with drip emitters  58  capable to work at low pressure, for example NETAFIM emitters “HyperTyphoon” or “Turbonet”.  
         [0059]     The branch tubes  22  are prefabricated in pieces of suitable length, possibly with connectors  21  pre-assembled at one end of the piece. The connectors may be bonded, welded or even integral with the tube.  
         [0060]     With reference to  FIGS. 5 and 2 , the gravity filter tank  14  is raised on a support with adjustable height, within a range of 1-2 m. The tank is of the type Self Cleaning Gravity Screen Filtration System, manufactured by Fresno Valves &amp; Castings, Inc., USA. The filter tank  14  comprises an inlet tank  62  with an inlet  64  connected to the source of water  12  ( FIG. 1 ), a catch tank  66  connected to the outlet pipe  16 , a filtering screen  68  with rotating jets  69  above the catch tank, and a trash tank  70  with discharge valve  72 . The pump  28  feeds contaminated water from the source  12  to the inlet tank  62 . The water falls on the filtering screen  68  which retains the contaminants  74  while filtered water  76  passes into the catch tank  66 . Contaminants are forced to move towards the trash tank  70  by the horizontal flow of water over the screen, and by the rotating jets  69  that spray water through the screen from below. Contaminants accumulate in the trash tank  70  where they are periodically removed through the discharge valve  72 . Clean water is directed through the piping  16  to the upstream end of the distribution pipe  20 .  
         [0061]     With reference to  FIGS. 1, 2  and  5 , the control system  24  of the irrigation system comprises an automated control block  74 , pressure sensors (head indicators)  76  and  78 , tank water level meter  79 , pump control block  82 , and communication lines. The pressure sensor  76  measures hydraulic head H 2  at the distal end of the branch tube  22 , while the sensor  78  measures head H 1  in the distribution pipe  20 . The head H 2  is usually the lowest pressure in the irrigation system  10 , due to all hydraulic losses along the water flowpath and especially along the branch tubes  22 .  
         [0062]     The control system  24 , as known in the practice of irrigation, is adapted to maintain a predetermined total operating head H in the system, which means a predetermined level of water in the catch tank  66 , by operating the pump  30  in dependence of the readings of water level meter  79 . In the low-pressure irrigation system of the present invention, the control system also maintains the minimal head H 2  in predetermined limits by regulating the water level in the catch tank  66 . That is, the total operating head H is raised or lowered in dependence of the readings of the pressure sensor  76  at the distal end of the branching tube  22 .  
         [0063]     The low-pressure irrigation system of the present invention will be better understood and its advantages will be made clearer if we describe a method of its assembly and a special tool used with the method.  
         [0064]     With reference to  FIG. 6 , an example is provided of a hand-held punch  80  for cutting holes in the distribution tube  20 . The punch  80  comprises a tubular cutter  82  with thin annular cutting edge  84  formed with plurality of teeth, a handle  86 , and a plunger  88 . The handle  86  has a through axial bore  90  communicating with the inside of the tubular cutter  82 . The handle  86  is firmly fixed to the tubular cutter  82  by a threaded sleeve  92 . The plunger  88  is connected to a tail rod  94 . The plunger  88  is movably accommodated inside the tubular cutter, with the tail rod obtained through the axial bore  90  and protruding out of the handle  86 .  
         [0065]     In order to cut the holes  40  (see also  FIG. 3A ), the distribution pipe  20  is first filled with water to assume more or less stable form of a round cylinder. The punch  80  is slightly urged to the pipe  20  with the cutting edge  84  at the place of the desired hole. Then the punch  80  is rotated by hand to cut a portion of the pipe wall and to obtain the hole  40 . The cut-out portions of material from the pipe wall accumulate in the tubular cutter  82 , and can be expelled therefrom by pressing said tail rod  94  and moving the plunger  88 .  
         [0066]     The punch  80  is a uniquely specialized tool with a major role in the overall efficiency of the assembly process of the irrigation system of the present invention. Its uniqueness is in the fact that the cutting edge  84  is so sharp and thin (though strong enough) that the punch  80  is able to cut holes with very light pressure on the material of the pipe wall which is supported from inside by the water pressure which does not exceed 3 m H 2 O in the moment of cutting. Thus, the punch  80  allows the holes  40  to be cut by hand, in a collapsible pipe that has no rigidity of its own and which is deployed in the field.  
         [0067]     It will be understood that the punch tool  80  may be designed and manufactured with powered drive for rotation, for example electric with accumulator battery, pneumatic and so on.  
         [0068]     The components of the irrigation system described above may constitute a kit comprising at least two of the following components: the distribution pipe  20 , the branch tubes  22  equipped with low-pressure drip emitters, the connectors  21  and the hand-held punch  80  provided for cutting the holes in the distribution pipe.  
         [0069]     With reference to  FIGS. 2, 3A  and  7 , the method for assembly of the low-pressure drip irrigation system from the components of the kit comprises: 
        deploying the distribution pipe  20  in the field and connecting it to a source of water ensuring 2-3 m H 2 O hydraulic head with respect to the field level, for example the filter tank  14  of  FIG. 2 ;     filling the distribution pipe  20  with water;     assembling one of the branch tubes  22  with the nipple part  42  of the connector  21 , as described above;     cutting a hole  40  in the distribution pipe  20  by means of the hand-held punch  80 ;     inserting the connector  21  into the hole  40 , thereby attaching the branch tube  22  to the pipe  20 ; and     repeating the last three steps for the rest branch tubes.        
 
         [0076]     It should be understood that in the time interval between cutting the hole  40  and inserting the connector  21  into the hole, the water is flowing through the hole  40  as a free jet. However, due to the low working pressure, the spilled quantity of water is insignificant, and the jet cannot prevent the manual insertion of the connector, nor the connector may be forced out after the insertion. Also, the above steps may be performed in a different order, for example the branch tube  22  may be assembled to the nipple part of the connector  21  after the latter is inserted into the hole  40 .  
         [0077]     The assembly of the branching tubes to the distribution pipe may be provided in other alternative ways. With reference to  FIG. 8 , there is shown a connector  110  comprising a body  112  with a first collar  114 , a separate second collar  115  and a sealing ring  116 . The connector body  112  is formed with external thread  118  matching respective internal thread in the collar  115 . Thus, the second collar  115  can seal the edge of the hole  40  against the first collar  114  by tightening up the thread  118 .  
         [0078]     The distribution pipe may be prefabricated with holes punched therein or with holes marked thereon. The holes may be disposed at predetermined intervals along the distribution pipe where the intervals may be defined in terms of practical range of distances between crop rows in the field or just in meters (feet).  
         [0079]     With reference to  FIG. 9 , there is shown the wall of a distribution pipe  120  with a prefabricated hole, which is equipped with an annular rim  122  made of rigid material and having an axis A. The rim has an inner portion  123  axially protruding into the pipe&#39;s interior, an outer portion  125  protruding outwardly from the pipe, and an intermediate portion  127  therebetween the axial extension of which corresponds to the thickness of the pipe. The outer portion  125  has an axial extension shorter than total axial extension of the inner and intermediate portions  123  and  127 , and the inner portion  123  of the rim has an axial extension shorter than the total axial extension of the intermediate and outer portions  127  and  125 . The rim  122  has a threaded portion  124  for assembling to a connector in the field. As shown in  FIG. 10 , instead of threading, bayonet lock  140  may be used, for assembling to a connector  142 , in which case base part  144  of the connector is formed accordingly.  
         [0080]     The annular rims  122  have an integral cover  126  preventing water flow through the hole before assembly. The integral cover  126  is surrounded by a tearable peripheral notch  128  for easy removal. A simple tool may be used to cut along the notch  128 . The recess  130  provides support for a rotating tool tip.  
         [0081]     The rims  122  are tightly fitting the edges of the holes and are installed therein before deploying the irrigation system in the field, e.g. fitted in the process of pipe extrusion. The rims are sufficiently thin so as to allow rolling the collapsed pipe into a tight reel.  
         [0082]     With reference to  FIG. 3B , the distribution pipe  20 A may be provided with an internal filtering membrane  32  extending along the whole length of the pipe. The pipe cross-section is thus divided into a supply chamber  34  and exit chamber  36 . The internal membrane  32  is made of micro-holed polyethylene sheet or of non-woven material. The whole pipe is assembled by welding along seams  33  by bead or heat welding. In operation, muddy irrigation water is fed into the supply chamber  34 , then passes gradually through the internal membrane  32  along the whole length of the pipe  20 A, enters into the exit chamber  36  and then into the connectors  21 . Mud particles are retained by the membrane and can settle as silt  38  in the lower part of the pipe due to the low flow velocity. Since the distribution pipe is several hundred meters long, the filtering area is huge and the pipe normally does not need flushing throughout the irrigation season. At the end of the season, the pipe  20 A can be flushed by feeding water in reverse direction (into the exit chamber  36 ) and opening the distal end of the supply chamber  34 .  
         [0083]     Although a description of specific embodiments has been presented, it is contemplated that various changes could be made without deviating from the scope of the present invention as defined in the following Claims.