Method of producing a drip irrigation pipe and a drip irrigation pipe

Abstract: This invention concerns a drip irrigation pipe having means for pressure strangulation, means for self regulation of the flow and method of producing same. The drip irrigation pipe has a main pipe (31) whose outer surface is shaped in such a way that the pressure reduction conduit (30) is formed, the last having water inlet openings (33). The pipe is covered with mantle (32) which has outlet openings (34) for irrigation.

Description: The invention concerns a production method for a drip irrigation pipe as defined in claim 1 and a drip irrigation pipe as defined in claim 5. The problem of drip irrigation has been faced either by inserting independent drippers in the water supply pipe or by attaching independent pressure reduction conduit to the main pipe. One of the problems in drip irrigation is that the water flow of the drippers along the pipe depends on the water pressure in the area of the dripper. The above pressure is not constant-either due to pressure drop or due to inclined installation (of the pipe), so water flow will vary along the pipe. On the other hand for uniform irrigation the water flow of the drippers should be constant. A drip irrigation pipe is known from WO-A-8909539 comprises a pressure reduction channel being formed by using so-called print heads. These print heads are not able to fabricate continuous pressure reduction channels. They can only to emboss or impress the channel into the wall of the main pipe. Therefore, it is only possible to fabricate relatively short pressure-reduction conduits or channels, and thus short drip irrigation pipes. As for the characteristics of the pressure reduction element itself they are the same as those described in EP-A-0 470 081 & WO-A-9011681. It is the object of the present invention to provide a method for producing a drip irrigation pipe, which is for the fabrication of a continuous drip irrigation pipe including a continuous pressure reduction conduit. Furthermore, it is the object of the present invention to provide an improved drip irrigation pipe. The first object is solved by the method according to claim 1 and the latter object is solved by the subject-matter of the independent product claim 5. As the drip irrigation pipe of the invention includes a strangulation conduit having variable cross-sectional areas the size of which changes depending on the pressure difference between the interior of the strangulation conduit and the interior of the main pipe, it has larger cross-sectional area at the points with small pressure in the main pipe, and smaller cross-sectional area at the points with large pressure in the main pipe. As a result the water supply in the strangulation channel remains approximately constant and virtually independent from the pressure variations in the main pipe. In order to achieve this variable cross-sectional area, an opening has to be made at a sub-section between two successive diaphragms of the strangulation conduit. This sub-section of the conduit where the opening has to be made, can be in any position between water inlet and outlet openings. After the opening has been made, a membrane has to be installed against the opening, which is sealed and supported in such a way that the water in the main pipe is prevented from entering the conduit through the opening. The one side of this membrane is pressed by the pressure of the main pipe while the other side by the pressure of the interior of the conduit. Hence the membrane is deformed in a way proportional to the difference between the two pressures. This deformation of the membrane changes the cross-sectional area inside the strangulation conduit at the point where the membrane is installed, varying the water supply and achieving regulation. The method and the drip irrigation pipe according to the present invention will be better understood with reference to preferred embodiments which will now be described with the assistance of the enclosed drawings in which: figure 1 shows a drip irrigation pipe in a lengthwise crosssectional view; figure 2 shows a perspective view of a drip irrigation pipe which is partially covered; figure 3 shows the main pipe according to figure 2 with a cover; figure 4 shows a perspectiv, partially cut-out view of a further embodiment according to the present invention; figure 5 shows a further embodiment according to the present invention; and figure 6 shows a variation of the method according to the present invention to produce a drip irrigation pipe. The above is explained better with respect to the accompanying drawings. In fig. 2 the main supply pipe 11 is shown whose outer surface has been shaped in such a way that the pressure reduction conduit 10 is uncovered while the drip irrigation pipe being fabricated. During production, the water inlet openings 13 are opened. Afterwards a plastic stripe 12 is welded over the open part of the conduit 10 forming its cover, and the water outlet openings 14 are opened. In fig. 3 a pipe 31 similar to the one shown in fig. 2 is shown, where again the pressure reduction conduit 30 - in the following called "special conduit" - without cover has been formed, and the water inlet openings 33 have been opened. In this case the whole pipe has been covered using a sheathing 32 which forms the cover of the conduit. Afterwards the water outlet openings 34 are opened. In fig. 4 a corrugated pipe 41 is shown, in which the special conduit 40 has been formed. The special conduit is covered using a sheathing 42, in the same way the plane pipe of fig 3 has been covered. In fig. 5 a corrugated pipe 51 is shown in which a special conduit 54, 55 has been formed in such a way that it extends along the total outer surface of the corrugated pipe 51. The conduit consists of rings 52, 53 each of which has a slit 54, 55. The slits 54, 55 of successive rings 52, 53 are placed opposite or in any case they are not on a line parallel to the axis of the pipe. The pipe is again covered with sheathing 56. This way, the strangulation channel is formed, which has narrowings formed by the slits 54, 55 and widenings formed by the points between rings 57, 58. Prefered dimensions for this form of the pipe are of the order of 2 mm for the distances 57, 58 between the rings and of the order of 1.2 mm for the slits 54, 55 while the height of the ring is of the order of 2 mm. In fig. 1 a main water supply pipe 7 is shown where a continuous pressure reduction conduit 1 is installed. The figure shows only a small portion of the conduit 1 between two diaphragms 2, 3. As shown an opening 4 has been made at the bottom of the conduit portion 1 between diaphragms 2 and 3. Then a flexible membrane 5 is placed which covers the part of the conduit where the hole 4 has been opened, in such a way that one side of the membrane is pressed by the pressure in the special conduit, while its other side is pressed by the pressure inside the main pipe. This way the membrane is deformed in a way proportional to the difference among these two pressures. A part, having the form of a chamber 6 is placed on the membrane, achieving the sealing of the membrane circumferentially, on one hand, and, on the other hand, this chamber has a suitable shape in order to allow for the deformation of the membrane to influence drastically the water flow in the conduit. In addition the chamber has openings 8 and 9 on its sides at suitable points in order to allow the water flow through the conduit. As far as the construction is concerned, it is mentioned that the membrane exists on the market, while the chamber will be manufactured using an injection machine, while both will be installed in the conduit using special equipment. Concerning the production method: During the production of the main pipe using a special corrugator, its outer surface is shaped in such a way that one or more special conduits are formed. The other surface of the main pipe can be either plane or corrugated. Then, the forming of the drip irrigation pipe is completed either by covering the part where the special conduit(s) have been formed using a stripe, or by covering the whole pipe using a sheathing. In addition the water inlet and outlet openings can be at any point on the circumference of the pipe at the points defined by the beginning and the end of the section of the special conduit(s). In addition, according to a new prefered embodiment, the special conduit can virtually extend along the whole external surface of the main pipe. This shape is consisted of rings each of which has a slit. The slits of successive rings are placed opposite its other or in such a way that they are not placed on a line parallel to the axis of the pipe. In fig. 6 a prefered arrangement of the production line of the pipe according to the present invention is shown. The line includes an extruder 61 which feeds a corrugator 62. In the corrugator a plane or a corrugated pipe 65 is produced on the surface of which one or more special conduits 66 are formed. During production the water inlet openings are opened either using a mechanism 67 or inside the corrugator 62. Then this pipe enters a die head 63 in the other inlet of which an extruder (64) is connected. In this die head the special conduit 66 is covered by a sheathing. In addition, the water outlet openings are opened using a special mechanism 68 in order for the complete drip irrigation pipe to be formed. Then the pipe is cooled in a water bath 69 while a haul-off unit 70 and a coiler 71 follow like in ordinary pipe production lines. With this method the production process of the drip irrigation pipe with embodied continuous conduit is simplified.

Claims: A production method for a drip irrigation pipe comprising the steps: a) a pipe (65) is produced by means of an extruder (61); b) after said pipe (65) is moved out of said extruder (61), it is supplied to a corrugator (62) which forms at least on a part of the outer surface of said pipe (65) one or more pressure reduction conduits (66); c) the water inlet openings to a pressure reduction conduit are formed; d) the pipe (65) enters a die head (63) to be at least partially covered with a cover (12; 32) over the pressure reduction conduit and said head (63) is hermetically connected to said extruder (64); e) the water outlet openings being formed; f) the pipe is directed to a cooling bath (69), a caterpillar haul-off (70) and a coiling device (71). A production method according to claim 1, characterized by forming the water inlet openings inside the corrugator (62) by means of a special corrugator design. A production method according to one of claims 1 and 2, characterized by covering only the special conduit inside the head (63). A production method according to one of claims 1 to 3, characterized in that a flexible membran is placed in the pressure reduction conduit, said membrane being deformed in relation to the difference between the pressure inside the main pipe and the pressure inside the conduit ensuring constant water flow. A drip irrigation pipe comprising a) a main pipe (11; 31; 41; 51) for supplying water; a1) a pressure reduction conduit (10; 30) including changes of the direction of the flow to achieve a pressure reduction; a2) the main pipe (11; 31; 41; 51) has its surface shaped so that corrugations form one or more of said pressure reduction conduits (10; 30), which conduits have water inlet openings (13; 33; 59); a3) said pressure reduction conduit includes in addition to or alternatively to the changes of the direction of the flow successive narrowings (8, 9) and widenings (6); b) at least the surface of the main pipe including reduction conduits (13; 33) is covered by means of a cover (12; 32; 56) which has water outlet openings (14; 34; 60) connected to the pressure reduction conduits. A drip irrigation pipe according to claim 5, characterized in that the cover is limited to a stripe of plastic (12) which covers only the pressure reduction conduits. A pipe irrigation pipe according to claim 6, characterized in that said conduit (1) has an opening between two diaphragms (2, 3). A drip irrigation pipe according to one of claims 5 to 7, characterized in that the opening (4) of the conduit (1) is covered by a flexible membrane (5) attached to an especially designed champer, which on the one hand makes the membrane (5) tight and on the other hand forms an appropriate cross-section to the water flow channel. A drip irrigation pipe according to one of claims 5 and 6, characterized in that said pressure reduction conduit (1) is an independent element attached to the water supply pipe (7). A drip irrigation pipe according to one of claims 5 to 8, characterized in that said main pipe (41) is corrugated. A drip irrigation pipe according to one of claims 5 to 10 comprising the following features: a) rings (52, 53) are provided in the main pipe (51), the rings having slits (54, 55); b) said slits (54, 55) of successive rings (52, 53) are arranged opposite to each other. A drip irrigation pipe according to claim 11, characterized in that said rings (52, 53) are equidistant or not equidistant. A drip irrigation pipe according to one of claims 11 and 12, characterized in that said slits (54, 55) of successive rings (52, 53) are arranged in such a way that they are in a line not parallel to the axis of the pipe.

Inventors: LEBIDAKIS IOANNIS, LEBIDAKIS, IOANNIS
Applicants: KRITIS PLASTIKA, PLASTIKA KRITIS S.A.
Application year: 1991
Main classification: A01G25
IPC codes: B29C47, A01G25