WO2005115634A1

WO2005115634A1 - Drip irrigation hose and method for making same

Info

Publication number: WO2005115634A1
Application number: PCT/IL2005/000516
Authority: WO
Inventors: Amir Cohen
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-05-24
Filing date: 2005-05-19
Publication date: 2005-12-08
Anticipated expiration: 2006-11-24

Abstract

A drip irrigation hose includes a plurality of emitter elements secured to a tube at longitudinally-spaced locations to define, with an inner surface of the tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube, and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate. The labyrinths are defined by a continuous strip bonded to the inner surface of the tube, and including a relatively elastic material shaped to define at least the tips of a group of teeth for each of the emitter elements, and a rib extending transversely across a part of the flow path from the respective emitter inlet to the respective tube outlet. Each of the latter ribs is formed with a slit which automatically opens when the water pressure within the tube at the respective emitter unit reaches a predetermined minimum to permit flow from the respective emitter inlet to the respective tube outlet.

Description

DRIP IRRIGATION HOSE AND METHOD FOR MAKING SAME

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to improvements in or modifications to drip irrigation hoses, and to methods for making such hoses, as described in my prior International Application PCT IL02/00953, filed November 26, 2002, published June 5, 2003 as International Publication No. WO03/045577. Drip irrigation hoses are increasingly being used for irrigating various types of plants since they supply the water directly to the root regions of the plants, and therefore are highly conservative of water resources. One type of irrigation hose is constructed by simultaneously extruding a plastic hose and bonding to its inner surface a plurality of emitter elements, or a strip of emitters, spaced longitudinally of the hose for discharging the water at a slow rate via discharge openings formed in the hose. Another type includes a sheet of flexible plastic material formed into a seamed hose, with the emitter elements bonded within the seam, or to another part of the hose, for discharging the water at a slow rate through discharge openings in the hose. The present invention is applicable to both types of drip irrigation hoses. Examples of drip irrigation hoses of these types are described in US Patent Nos. 4,196,853; 5,163,622; 5,183,208; 5,203,503; 5,246,171; 5,333,793; 5,522,551; 5,620,143; 5,695,127; 5,785,785 and 6,027,048. One problem in using drip irrigation hoses is the difficulty in ensuring relatively uniform discharge rates along the length of the hose. This problem is particularly acute where extremely long lengths of the hose are used since the hose itself produces a pressure drop along its length tending to decrease the discharge rate of the emitters at the end of the hose. This sensitivity of the discharge rate to the water pressure is also a problem where the land being irrigated is not flat and even. Another problem with such drip irrigation hoses is sensitivity to clogging and the difficulty in dislodging clogging particles. Both of the above problems are addressed by the drip irrigation hoses described in the above-cited patents. Generally, one or both problems is dealt with by providing each emitter element of the hose with a deformable member, such as a deformable membrane, which deforms in response to pressure to provide pressure-compensation. One known drip irrigation hose includes a continuous strip of relatively elastic material bonded to the inner surface of the tube to define a plurality of labyrinths each having an inlet communicating with the interior of the tube and an outlet communicating with an opening through the tube serving as the discharged outlet. However, drip irrigation hoses are frequently used for only a single season, or for relatively few seasons. Accordingly, the cost involved in producing such drip irrigation hoses is a significant factor in their use. The known drip irrigation hoses addressed to one or both of the above problems are generally relatively costly to manufacture and/or use relative costly materials. The known drip irrigation hoses also exhibit a tendency to leak water when the hose is not at its normally-operative pressure, e.g., when initially filling the hose or emptying the hose. Such leakage can result in considerable water wastage particularly where the irrigation system is intermittently operated as commonly done today. The above-cited U.S. Patent 6,371,390, discloses a drip irrigation hose comprising a tube for conducting pressurized water through its interior and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to the tube at longitudinally-spaced locations along its length to define, with an inner surface of the tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet communication with a tube outlet for discharging water from the tube outlet at a slow rate. The labyrinths are defined by a continuous strip of a relatively inelastic material bonded to the inner surface of the tube, and a formation of a relatively elastic material shaped to define a group of teeth for each of the emitter elements producing, with the inner surface of the tube, turbulent flow passageways at each of the longitudinally spaced locations along the length of the continuous strip. That application described a number of constructions of such drip irrigation hoses, as well as methods and apparatus for making such hoses. The above-cited International Application PCT IL02/00953 described a number of further constructions of such drip irrigation hoses and methods of making. The present invention involves still further constructions of such drip irrigation hoses and methods of making such hoses. For the sake of brevity, the complete descriptions in the above-cited U.S. Patent 6,371,390 and International Application PCT IL02/00953 are not reproduced herein but rather are incorporated herein by reference. OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION

An object of the present invention is to provide further constructions of drip irrigation hoses, and methods of making such hoses, having a number of important advantages as will be described more particularly below. According to one aspect of the present invention, there is provided a drip irrigation hose, comprising: a tube for conducting pressurized water through the interior of the tube and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to the tube at longitudinally-spaced locations along its length to define, with an inner surface of the tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate; the emitter elements including a continuous strip bonded to the inner surface of the tube and formed with teeth along the length of the continuous strip defining the plurality of labyrinths with the inner surface of the tube; at least the tips of the teeth of the continuous strip being of a relatively elastic material; the continuous strip being further formed with a rib of the relatively elastic material for each labyrinth extending transversely across a part of the flow path from the respective emitter inlet to the respective tube outlet; each of the ribs being formed with a slit which automatically opens when the water pressure within the tube at the respective labyrinth reaches a predetermined minimum to permit flow from the respective emitter inlet to the respective tube outlet. Such a construction enables water wastage due to leakage to be substantially reduced, particularly where the irrigation system is intermittently operated for relatively short periods, rather than continuously operated for relatively long periods. In addition, the irrigation line tends to remain full during periods of non-operation, so as to decrease the time of pressure build-up for proper operation. While it is preferred that, in the normal non-pressurized condition of the tube, the slit be completely closed to prevent any water wastage, complete closure is not essential as some water wastage can usually be tolerated. According to another aspect of the present invention, there is provided a method of making a drip irrigation hose including a tube for conducting pressurized water through the interior of the tube and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to said tube at longitudinally-spaced locations along its length to define, with an inner surface of said tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate; said method comprising: forming a continuous strip with a plurality of groups of teeth to define said plurality of labyrinths with the inner surface of said tube, when secured thereto, and also to define a rib extending transversely across a part of the flow path of each labyrinth from the respective labyrinth inlet to the respective tube outlet; forming a slit in each of said ribs configured so as to automatically open with an increase in water pressure therein at the respective labyrinth; and bonding said continuous strip to the inner surface of said tube. Further features and advantages of the invention will be apparent from the description below. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 illustrates a continuous emitter strip for use in constructing drop irrigation hoses in accordance with the present invention; Fig. 2 is an enlarged fragmentary view illustrating the outlet end of one of the emitter elements in the continuous strip of Fig. 1; Figs. 3, 4 and 5 are fragmentary views illustrating modifications in the construction of the emitter strip at the outlet end of the emitter element; Fig. 6 is an end view illustrating the shape of the slit in the rib of Fig. 5 at the outlet end of the respective emitter element; Figs. 7 and 8 are views similar to that of Fig. 6 but illustrating modifications in the shape of the slit formed in the rib; Fig 9 illustrates a continuous strip constructed in accordance with the present invention, similar to that of Fig. 1 but constituted of only relatively elastic material; Fig. 10 is an enlarged fragmentary view of the outlet end of the strip of Fig. 9; Fig. 10a is a sectional view along line a a of the emitter strip of Fig. 10 when bonded to the inner face of the tube; Fig. 11 illustrates one method of making the continuous strip defining emitter elements, and particularly for producing the slit in the rib at the outlet end of each emitter element; Fig. 12 illustrates the emitter strip of Fig. 11 being applied to the inner face of a tube; Figs. 13 and 14 illustrate a further variation in the construction of the continuous strip defining the emitter elements; and Fig. 15 illustrates a drip irrigation hose constructed in accordance with the present invention but including a seamed tube, rather than a seamless, extruded tube. It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and various possible embodiments thereof, including what is presently considered to be preferred embodiments. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.

DESCRIPTION OF PREFERRED EMBODIMENTS As indicated earlier, the present application relates to a number of improvements in or modifications to the drip irrigation hoses, and to methods for making such hoses, as described in International Application PCT IL02/00953, the contents of which are incorporated herein by reference. Figs. 1 and 2 illustrate an emitter strip, generally designated 3300, constituted of two co-extruded inelastic strips 3311, 3312, on opposite sides of an elastic strip 3320. Non-elastic strip 3312 is formed with the inlet slits 3312 to the respective labyrinth. The elastic strip 3320 is formed with the teeth 3321 defining the respective labyrinth, and with a rib 3324 to define, on one side thereof, an outlet chamber 3325a communicating with the outlet end of the labyrinth, and on the opposite side, an outlet chamber 3325b communicating with an outlet chamber 3312f of the inelastic material, which communicates with the outlet slit through the tube (e.g., slit 2304 of tube 2302, Fig. 19d, in the above-cited International Application PCT IL02/00953). In the emitter structure illustrated in Figs. 1 and 2, rib 3324 is formed with an elongated slit 3324a, corresponding to slit 2324a in Fig. 19d in International Application PCT IL02/00953, serving as a one-way valve normally closing the outlet end of the respective emitter element until the pressure within the drip irrigation hose is at a minimum positive pressure. In the illustrated construction, slit 3324a extends substantially perpendicularly to the inner surface of the tube. It will thus be seen that the construction illustrated in Figs. 1 and 2 operates in the same manner as described (e.g., with respect to Figs. 19a- 19e in International Application PCT IL02/00953) in that slit 3324a is normally closed, to thereby close the passage from the outlet end of the labyrinth defined by teeth 3321 to the outlet chamber 3325b, communicating with the outlet chamber 3312f of the inelastic strip 3312, which in turn communicates with the outlet opening through the tube. However, when the pressure within the drip irrigation hose reaches a minimum positive pressure, slit 3324a opens and thereby permits the passage of the water from the labyrinth to the outlet opening 2304 via chambers 3325b and 3312f. As noted above, in the closed condition of slit 3324a, it is not necessary that it completely block any flow therethrough, since some leakage can usually be tolerated. Fig. 3 illustrates a similar construction as in Figs. 1 and 2, but in this case each of the openings through wall 3324 of the elastic material is in the form of an elongated slit 3324b extending substantially parallel to the inner surface of the outer tube. The emitter illustrated in Fig. 3 is otherwise constructed and operates in the same manner as the emitter element illustrated in Figs. 1 and 2. Fig. 4 illustrates another modification in the construction of the emitter elements, particularly in each of the openings through rib 3324 of elastic material to produce the one-way valve action described above. In the construction illustrated in Fig. 4, each of the openings through rib 3324 is in the form of an elongated slit of L-shaped configuration, having a section 3324c extending substantially parallel to the inner surface of the outer tube, joined at one end by another section 3324d extending substantially perpendicularly to the inner surface of the outer tube. The slit through the blocking rib (3324) may take other configurations. Examples of various non-linear configurations that can be used are illustrated by slit 3324e in Figs. 5 and 6, by slit 3324f in Fig. 7, and by slit 3324g in Fig. 8. While it is preferable to form the blocking rib 3324, together with its slit (e.g., 3324b), at the outlet end of its respective labyrinth, actually it may be formed anywhere between the inlet end of its respective labyrinth and the tube outlet (e.g., 2304, Fig. 19b of PCT IL02/00953) for the respective labyrinth. Figs. 9, 10 and 10a illustrate another construction of emitter strip, therein generally designated 4300, wherein the complete strip is of elastic material; that is, the emitter strip 4300 illustrated does not include a portion of inelastic material, as in the previously-described constructions. In this case, the rib 4324 formed with the slit 4324e is also at the outlet end of the respective labyrinth, dividing the labyrinth outlet chamber into to sections 4325a, 4325b; but the tube outlet 4304 of the tube 4302 directly communicates with chamber section 4325b of elastic material. As shown in Fig. 10a, slit 4324e is preferably inclined with respect to the inner surface of tube 4302. An advantage of this construction is that it simplifies the extrusion of the emitter strip, since only one material, namely the elastic material, needs to be extruded; however, a disadvantage of that construction is that the cost of the emitter strip is increased because of the greater amount of the more expensive elastic material used in the emitter strip. Fig. 11 illustrates one manner of producing the emitter strip 4300 of Figs. 9, 10 and 10a. Thus, as shown in Fig. 11, a strip 4301 of relatively elastic material is extruded by extruder 4350 and formed into the emitter elements by an embossing wheel 4360, which also forms the blocking rib 4324 at the outlet end of each emitter element. The slit through the blocking rib 4324 (e.g., of any one of the configurations illustrated above at 3324a — 3324g) is produced by any suitable means downstream of the embossing wheel 4360, e.g., by a knife 4370, laser, or the like. After the strip 4300 is thus, formed, it is then bonded to the inner surface of the tube, as shown at 4302 in Fig. 12, after which the tube is formed with the outlet slits 4304. Figs. 13 and 14 illustrate a further construction of emitter strip, therein designated 5300, constituted of three co-extruded strips, namely inelastic strips 5311 and 5312 co- extruded with, and on opposite sides of, elastic strip 5320. In this case, however, only the tips of the teeth 5321 are made of elastic material; the remainder of the emitter strip 5300 is constituted of the two inelastic strips 5311, 5312, co-extruded on opposite sides of the elastic strip 5320. An advantage of this construction is the reduced cost since the more expensive elastomeric material is used only with respect to the tips of the teeth 5321 of the labyrinths. Fig. 15 illustrates a further variation, wherein the emitter strip, therein designated 6300, is applied to the inner surface of a tube 6302 in the form of a seamed tube, rather than an extruder tube. As shown in Fig. 15, the outlet 6304 through the tube for each of the emitter elements is in the form an elongated slit, and is preferably located on the side of the tube opposite to its seam 6305. While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made.

Claims

WHAT IS CLAIMED IS: 1. A drip irrigation hose, comprising: a tube for conducting pressurized water through the interior of the tube and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to said tube at longitudinally-spaced locations along its length to define, with an inner surface of said tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate; said emitter elements including a continuous strip bonded to the inner surface of said tube and formed with teeth along the length of said continuous strip defining said plurality of labyrinths with the inner surface of said tube; at least the tips of the teeth of said continuous strip being of a relatively elastic material; said continuous strip being further formed with a rib of said relatively elastic material for each labyrinth extending transversely across a part of the flow path from the respective emitter inlet to the respective tube outlet; each of said ribs being formed with a slit which automatically opens when the water pressure within the tube at the respective labyrinth reaches a predetermined minimum to permit flow from the respective emitter inlet to the respective tube outlet.

2. The drip irrigation hose according to Claim 1, wherein said continuous strip is completely made of said relatively elastic material.

3. The drip irrigation hose according to Claim 1, wherein said continuous strip is made of relatively inelastic material except for said teeth and ribs which are made of said relatively elastic material.

4. The drip irrigation hose according to Claim 1, wherein at least a part of each of said slits extends substantially perpendicularly to the inner surface of said tube.

5. The drip irrigation hose according to Claim 1, wherein at least a part of each of said slits extends at an incline to the inner surface of said tube.

6. The drip irrigation hose according to Claim 1, wherein each of said slits is of a non-linear shaped configuration.

7. The drip irrigation hose according to Claim 1, wherein each of said ribs is located between the outlet end of the respective labyrinth and the tube outlet for the respective labyrinth.

8. The drip irrigation hose according to Claim 1, wherein said tube is an extruded tube.

9. The drip irrigation hose according to Claim 1, wherein said tube is a seamed tube.

10. A drip irrigation hose, comprising: a tube for conducting pressurized water through the interior of the tube and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to said tube at longitudinally-spaced locations along its length to define, with an inner surface of said tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate; said emitter elements including a continuous strip bonded to the inner surface of said tube and formed with teeth along the length of said continuous strip defining said plurality of labyrinths with the inner surface of said tube; said continuous strip being of a relatively elastic material and being further formed with a rib for each labyrinth in the flow path from the respective emitter inlet to the respective tube outlet; each of said ribs being formed with a slit which automatically opens when the water pressure within the tube at the respective labyrinth reaches a predetermined minimum to permit flow from the respective emitter inlet to the respective tube outlet.

11. The drip irrigation hose according to Claim 10, wherein each of said ribs is formed to extend horizontally across a part of the flow path from the respective emitter inlet to the respective tube outlet.

12. The drip irrigation hose according to Claim 10, wherein at least a part of each of said slits extends substantially perpendicularly to the inner surface of said tube.

13. The drip irrigation hose according to Claim 10, wherein at least a part of each of said slits extends at an incline to the inner surface of said tube.

14. The drip irrigation hose according to Claim 10, wherein each of said slits is of a non-linear shaped configuration.

15. The drip irrigation hose according to Claim 10, wherein each of said ribs is located between the outlet end of the respective labyrinth and the tube outlet for the respective labyrinth.

16. The drip irrigation hose according to Claim 10, wherein said tube is an extruded tube.

17. The drip irrigation hose according to Claim 10, wherein said tube is a seamed tube.

18. A method of making a drip irrigation hose including a tube: a tube for conducting pressurized water through the interior of the tube and formed with a plurality of tube outlets for discharging the water at longitudinally-spaced locations along the length of the tube; and a plurality of emitter elements secured to said tube at longitudinally-spaced locations along its length to define, with an inner surface of said tube, a plurality of labyrinths each having an inlet in communication with the interior of the tube and an outlet in communication with a tube outlet for discharging water from the tube outlet at a slow rate; said method comprising: forming a continuous strip with a plurality of groups of teeth to define said plurality of labyrinths with the inner surface of said tube, when secured thereto, and also to define a rib extending transversely across a part of the flow path of each labyrinth from the respective emitter inlet to the respective tube outlet; forming a slit in each of said ribs configured so as to automatically open with an increase in water pressure at the respective labyrinth; and bonding said continuous strip to the inner surface of said tube.

19. The method according to Claim 18, wherein each of said ribs is formed to extend transversely across the flow path between the outlet end of the respective labyrinth and the tube outlet for the respective labyrinth.

20. The method according to Claim 18, wherein said slits are cut by a knife.

21. The method according to Claim 18, wherein said slits are cut by a laser beam.

22. The method according to Claim 18, wherein said tube is extruded around said continuous strip, and the continuous strip is bonded to the inner surface of the extruded tube.

23. The method according to Claim 18, wherein said continuous strip is bonded to a plastic sheet, which sheet is then formed into a tube having overlapping edges, which edges are seamed.