IL37425A - Irrigation system and flexible tubing for use therein - Google Patents

Description

tfia*^? n©*»A MJsi n»*pwn na sa Irrigation system and flexible tubing for use therein DONE 0. BOTLE and ROBERT 0. OSBORS trading as BOYLE AND OSBORH C:-35590 The present invention relates generally to subsurface irrigation systems, to flexible tubing inter alia suitable therefore and to a method for producing flexible tubing.

Surface irrigation systems are well known, which include a network of ditches for conveying and distributing water to plants in arid areas. Also known are underground piping systems for conveying water to outlets or sprinkler heads disposed at or above ground level for spraying such water on adjacent vegetation. In open ditch irrigation water wastage from evaporation and deep seepage in porous soils can be extensive. On the other hand, in non-porous soils water tends to collect and stagnate in pools, thereby creating pollution problems and providing breeding areas for mosquitoes and other insects. In the use of spray systems, insecticides are often washed off plants, thereby aborting their purpose and needlessly contaminating the soil, and the resultant wet foliage can promote plant diseases.

Subsurface irrigation systems offer many advantages over surface irrigation system*f but in many instances have been impracticable because of the high coot of providing and laying out suitable piping and the expensive accessory equipment such as high pressure pumps and flow regulating devices. Moreover, their performance has often been unsatisf ctory 3ince the water outlet perforations in these underground pipes become clogged, thu3 reducing efficiency and making it even more difficult to control properly the rate of flow of \ According to one aspect of the present invention we provide a flexible tubing comprising at least two superposed 37425-2 elongate flexible webs heat-bonded and sealed together along their longitudinal edges, at least one of the webs being formed of material of a permeable fibrous structure, e.g. a non-woven fabric preferably of polyolefin. At least two of the webs may be formed of heat weldable thermoplastic material and at least one may be of non-thermoplastic material. This type of tubing may be used in a subsurface irrigation system, according to the invention the flexible tubing being laid beneath the surface of the soil to be irrigated and means for supplying water thereto. Such tubing having at least a portion of the surface thereof composed of a permeable, fibrous material through which water may pass at a slow, controlled rate with a negligible pressure drop through the system, is inexpensive to manufacture and install and is capable of confining the delivered water to the desired areas only.

The invention also provides a method of forming flexible tubing of the invention, such method comprising forming a composite web roll comprising at least two superposed layers of elongate flexible web, at least one of which is formed of permeable fibrous material, at least one of the webs being of weldable thermoplastic material and a parting layer and heating the radially extending end faces of the roll to a temperature sufficient to cause binding together of the longitudinal edges only of at least two of the superposed webs in each convolution of the roll.

In order that the invention nay more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:~ Figure 1 is a perspective view of a roll of one form of tubing of the present invention with a layer of parting material between the convolutions of tubing; Figure 2 is an enlarged section, taken on line 2—2 of Figure 1, of the tubing and parting naterial layer shown in Figure 1; Figure 3 is a perspective end view similar to Figure , with the parting material removed; Figures 4 - 7 are views similar to Figure 3» illustrating various modified forms of tubing according to the present invention; Figure 8 is a plan view of an underground or subsurface irrigation system utilizing the tubing of the present invention; Figure 9 is a scrap section showing how spliced connections may be formed with tubing according to the present invention; Figure 10 is a perspective view showing a composite roll for fonr.ing flexible tubing by the method of the invention; Figure 11 is a perspective diagrammatic view showing the slicing into discs of a composite roll similar to that of Figure lO; Figure 12 is a schematic illustration of one suitable type of apparatus for heat-sealing the edges of the discs shown in Figure 11; Figure 13 is a perspective view of a roll of finished tubing; Figure 14 is an enlarged, fragmentary, perspective view of tubing produced by the nethod of the present invention; and Figures 15 , 16 and 17 are views siailar to Figure It illustrating modified forms of flexible tubing according to the invention.

Referring now to the drawings Figure 1 shows a roll 10 of flattened, flexible tubing 11 having a layer 20 of parting material thereon. Tubing 11 , as shown in detail in Figures 2 and 3 j is a simple ionj of flexible tubing which is particularly useful in subsurface irrigation. The tubing 11 comprises a first strip 12 and a second strip 14 joined together along thoir longitudinal edges 16 and IS, respectively. The strip 12 is composed of flexible, impermeable, preferably thermoplast c material, and the strip 14 is formed of a flexible fibrous material, preferably a non-woven thermoplastic material, such as the spun-bonded, polyethylene, non-woven fabric sold under the trade name "TYVEK", which will perr.iit the slow passage therethrough of a liquid, e.g. water, by seeping. The strips 12 and 14 of tubing 11 are preferably composed of heat-weldable thermoplastic materials to enable the longitudinal edges thereof to be readily heat-sealed together.

The modified form of tubing shown in Figure 4 has an additional strip 36 of heat weldable thermoplastic material which is provided with a plurality of perforations 38. The perforated strip 36 protects the per?neable fibrous strip 14 against damage in handling and provides additional strength tc the tubing. The number, size, and arrangement of the perforations 38 ^iay vary as desired. However, the perforations should be large enough to preclude their becoming clogged by soil and, preferably, should all be arranged between the edges of the layer 36.

The modified form of tubing shown in Figure 5 differs frou that shown in Figure 3 in that the inperneable 3trip 12 of the latter is replaced by a permeable flexible strip l4' of a thermoplastic, fibrous material which may be identical with the strip 14 or nay be of a different material, to allow water to seep through substantially the entire circumferential surface of the tubing.

In Figure 6 both flexible strips 14 and l4' are permeable, and a flexible thermoplastic strip 3^ having perforations 38 therein is arranged on the outer side of each of the strips 14 and l4' . Thus the tubing is given additional strength and resistance to danage. As in the forms previously described, the several superposed strips are bonded together along their edges, preferably by heat-sealing.

The tubing shown in Figure 7 has a second perforated strip 36 interposed on the inner side of the perneable, fibrous strip 14. The perneable strip is thus additionally reinforced and, by suitable choice of the relative size and arrangement of the perforations 38 in the two strips 36 , the rate of flow of liquid through the perneable strip 14 at a given pressure nay be predetermined.

A sinple, inexpensive way to join lengths of the tubing together is illustrated in Figure 9 , in which the ends of tubing sections 40 are placed over the ends of a tubular nipple 41 and held in place thereon by clamps 44, such as a metal or plastic mechanical clanp or a ring of a heat-shrinkable plastic, for example, an irradiated polyolefin or polyvinyl chloride, which when heated shrinks and firnly clanps the tubing on the nipple .

Figure 8 illustrates a subsurface irrigation system comprising a nanifold 26 having a plurality of distribution lines or branches 28 , formed at least in part of tubing such as shown in Figure 3, extending laterally therefrom and disposed beneath the surface of the soil and between rows of plants 30· Tbe manifold 26 and branches 28 are supplied with water through a feed line 32 and a pump >k fron a suitable source (not shown) , and the free end3 of the branches 28 nay be heat-sealed, or closed in any other suitable manner. The particular arrangement of the branches 28 and manifold 26 depicted in Figure 8 is exemplary only and any suitable number of branches arranged in any desired or convenient pattern is contemplated. For exanple, the branches 28 can be of different sizes, nay be disposed at different vertical levels, curved in any desired path, and extend in any desired direction to any desired length, and the flow characteristics of the different branches, or even portions of the sais.c branch, nay be different to provide the optinun water supply to different types of vegetation.

With such an irrigation syste according to the present invention, the water is not forced through orifices punched or drilled in the distribution lines, but is released through a large pervious area, equal to at least nearly half of the inside wall of the tubing. If the distribution lines are merely kept filled, the pervious fibrous side or sides of the tubing will act as v/icks to transfer appreciable water fron the inside to the outside thereof. Since a very low pressure is required, the heavy duty pumps, pressure regulators, and attendant hardware necessary for the usual subsurface irrigation systems are not needed. The slow seepage of the water from the branches 28 at a controllable uniform rate over a large area of the tubing permits the saving of water eince it nay be released at such a rate as to provide water only in desired areas of the soil .

Such a subsurface irrigation 3ysterr. is not only inexpensive to install, since the tubing, itself inexpensive, is merely laid out in covered trenches, but the systen is economical in operation. The seeping action described above is not interfered with by slimes on silt whereas flow through orifices aay be at least partially blocked thereby. The nanifold 26 and feed line 32 nay also be of flexible tubing, if desired, and such tubing may be pervious in whole or in part. Since the permeability of flexible tubing can be varied by the use therein of fibrous material having the desired porosity, it is possible to have different flow characteristics in different portions of an irrigation system even when using tubing of uniform size.

If desired heat-sealing of the edges of the tubing when a thermoplastic strip or strips are employed in forning it nay be acconplished by passing the edges between heated rollers. Also, of course, ad esives may be used or a suitable solvent which softens the edges of the strips to permit bonding then pressure.

Not only is the tubing particularly useful for subsurface irrigation, but it also has utility for surface irrigation.

It may be employed i/ erever it is desired to release fluids, either liquid or gaseous, along the length of a line of conduit. Thus, it is useful in the aeration of soil and water and can also be used to supply treating materials, for exaaple, disinfectants or nutrients, to soil or water. The tubing is particularly useful for such purposes because of its capability of slowly passing fluids into an air.bient environment at a unifom controlled rate, under a minimum of applied pressure. The natcrials should have substantial permeability because a material having a degree of permeability such as to pemit only nolecular diffusion of gases or liquids therethrough would be unsuitable for use in the present process. The seeping action can be aided by initially incorporating in the water (by suitable neans not shown) a small amount of a surface active or wetting agent, such as alkyl aryl sulfonates and lauryl sulfonic acids, employed in amounts as small as 0.1% or less. Only a short initial period of their use is necessary even with hydrophobic materials.

One example of a method of forming tubing according to the invention is shown in Figures 10 to . As shown in Figure Ή a section of finished flexible tubing 50, preferably formed of thermoplastic material, as formed in rolls (see Figure 13) > is flattened but will assume a rounded, substantially cylindrical cross-section when extended by a fluid under pressure therein. The approximate diameter of the tubing in use may be determined from the formula D P being the diameter of the tubing and W the width of the strips. Actually the diameter will in all cases be somewhat less, because of the material in the seams. The tubing 50 comprises two superposed, elongated strips of thermoplastic material 52 joined together along their longitudinal edges and 56 by heat-sealing.

According to a preferred method two webs of flexible thermoplastic material 8 and a flexible web 60 of non-thermoplastic material suitable for a parting layer, for example two-ply tissue paper, are wound together about a core 62 into a composite roll 6 . The winding mechanism (not shown) may be of any desired type and the roll 6k may be of any convenient size. The composite roll 6k is then severed in a direction in radial planes normal to the axis thereof, into discrete, small, composite strip rolls or discs 66 by such means as a rotary cutting blade 68, as shown in Figure 11, supported and driven by any means (not shown) . The discs 66 may be of any desired thickness, the thickness being approximately the width of the desired flattened tube. The longitudinal edges of the superposed thermoplastic strips 8 in the composite discs 66 are then fused together to seal them.

One type of suitable means for the heat-sealing is shown schematically in Figure 12, the composite discs 66 being individually laid flat on a conveyor 70 and passed beneath a radiant heat source, such as infra-red heater 72, which provides sufficient heat to heat-weld the contacting plastic strips 8 along their respective exposed longitudinal edges. The conveyor 70 carries the composite discs 66 to a turn-over mechanism 7^, by which the discs 66 are turned upside down. The discs are then carried on the same conveyor 7 or another one, beneath a radiant heat source, such as another infra-red heater 7 by which the other longitudinal edges of the contacting plastic strips 58 i the discs 66 are heat-welded together. During the heat-sealing procedure only the longitudinal edges of adjacent thermoplastic strips 58 are fused together to form the tubing 50, adhesion between the pair of thermoplastic strips in one convolution with those in adjacent convolutions being prevented by the parting strip 60 of non-thermoplastic material therebetween.

The resulting roll 82 of tubing 50 shown in Figure 13 can be easily and conveniently stored, transported, and used. When it is desired to use the tubing, the desired length is simply unwound from core 8^ and severed. The layer 60 of parting material, which may adhere slightly at its edges to the tubing 50, may be easily peeled off and discarded or may be left in place, since it will gradually be worn or torn away.

The flexible material from which tubing is formed may be impervious or pervious, e.g. fibrous, either in woven or non-woven form, or with perforations. By a heat-weldable thermoplastic material is meant one which when heated will soften sufficiently for moderate pressure to cause adjacent layers to fuse or weld together. Among generally suitable thermoplastic materials are polyolefins, polyvinyl chloride, fluorinated hydrocarbons, polyesters, nylons, polyacrylates, other polymerized vinyl esters and vinyl copolymers, and silicone rubber. However, non-thermoplastic , flexible strips may in some cases be employed. Such material should be bondable by at least one of the thermoplastic strips or webs employed, i.e. the thermoplastic material when heated should adhere or otherwise be secured to the non-thermoplastic strip, and may also be impervious or pervious. Among the numerous materials suitable are metal foils and metallized regenerated cellulose and other films. It will be appreciated, however, that heat-sealing of the edges of tubing including a non-thermoplastic strip will be easier in many cases, particularly in the absence of preheating the entire disc-like composite rolls, if the non-thermoplastic material is fibrous in character as penetration of the thermoplastic material thereinto aids bonding. The thickness of the webs may conveniently vary from about 0.025 nan to about 0.25 ∞m in thickness, but in some instances may be thinner or thicker. If desired, one or more of the webs may contain reinforcing material such as strands of wire or glass fibres.

In Figures '15 - 17, there are shown three of the large number of modified forms of flexible tubing possible according to the present invention. In Figure 15 the tubing 50 is double-walled, each side of the flattened tubing comprising a plurality of strips of thermoplastic material, an inner strip 88 and an outer strip 90. In Figure 16 tubing 50, as shown in Figure 1 t is provided with a continuous, longitudinal mounting strip 9 heat-welded or bonded along one edge to the edge 5^ of the tube. This tube modification is conveniently made by the modified process hereinafter described. Such modified tubing may be mounted on a suitable support (not shown) by nails or other appropriate fastening means (not shown) engaging the mounting strip 92. Figure 1? illustrates still another modification in which a flexible strip 9 *· of suitable, bondable, non-thermoplastic material is positioned between strips 6 of thermoplastic material.

During heat-sealing the edges of such tubing, the softened thermoplastic strips adhere to and bond the edges of the non-thermoplastic strip to give a fluid-tight seal.

The heating of the side faces of the small composite rolls 66 may be carried out in a variety of ways. Other radiant heat sources may be used and, if desired, both side faces may be heated simultaneously. It is also possible to heat-seal the edges of the strips or webs in the discs or rolls 66 by carefully controlled direct heating as, for example, by rapid passage in contact with a flame or by the application of heated tools or surfaces to the side faces of the rolls.

In severing the composite roll 6½ into smaller disc-like rolls, a plurality of cutting blades may be employed, thus providing a plurality of discs or rolls 66 simultaneously. It is also possible to pre-slit the webs 58 and 60 to the desired width before winding them together, the edges of the thermoplastic strips in the thus formed relatively thin composite »olls being sealed in one of the ways described above.

The modified form of tubing illustrated in Figure 16 can be conveniently produced by this process. The mounting strip 92, being narrower than the strips 2 , is wound in the composite roll so that one edge thereof is aligned with the edges ½ of the strips 52. Accordingly, the aligned edge of the strip 92 will be bonded to the tubing strips 52 when the edges 5^ thereof are sealed by heat-welding.

In the foregoing description the use of a paper strip or web as a parting layer between adjacent convolutions of the tubing is set forth, but other materials > . of non-thermoplastic character may be used, e.g. regenerated cellulose and polyimides or a coating of a suitable material, e.g. a starch, gelatin, or methyl cellulose, can be applied by spraying, brushing, or rolling a suitable solution or suspension onto the appropriate surface of one of the webs or strips making up the composite rolls from which the tubing is formed.

Claims (26)

C L A I M S

1. A flexible tubing comprising at least two superposed elongate flexible webs heat-bonded and sealed together along their longitudinal edges, at least one of the webs being formed of material of a permeable fibrous structure.

2. Flexible tubing according to claim 1, in which at least two of said webs are formed of heat weldable thermoplastic material.

3. Flexible tubing according to claim 1 or 2, wherein at least one of the webs are formed of bondable non-thermoplastic material.

4. Flexible tubing according to claim 1, 2 or 3, wherein at least one of the webs is formed of impermeable material .

5. Flexible tubing according to any one of the preceding claims, wherein at least one web of impermeable material having perforations therein is associated with at least one of the webs formed of material of a permeable fibrous structure.

6. Flexible tubing according to any one of the preceding claims, wherein the or each web of material of a permeable fibrous structure is a non-wo en fabric.

7. Flexible tubing according to claim 6, wherein the non-woven fabric is spun-bonded. V. i 37425-2

8. Flexible tubing according to claim 7, wherein the fabric is formed of poiyolefin yarns.

9. Flexible tubing according to claim 8, wherein the non-woven fabric is formed of polyethylene yarn.

10. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 1, 2 and 3 of the accompanying drawings.

11. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 1 and 4 of the accompanying drawings.

12. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 1 and 5, of the accompanying drawings.

13. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 1 and 6 of the accompanying drawings.

14. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 1 and 7 of the accompanying drawings.

15. An irrigation system comprising flexible tubing according to any one of claims 4 to 13, laid beneath the surface of the soil to be irrigated and means for supplying water thereto.

16. An irrigation system according to claim 15, wherein the means for supplying water include a manifold and a plurality of lengths of said flexible tubing in communication therewith.

17. A method 0f forming flexible tubing according to any one of claims 1 to 14, such method comprising forming a composite strip roll comprising at least two superposed layers of elongate flexible strip, at least one of which is formed of a material of a permeable fibrous structure, at least one of the strips being of weldable thermoplastic material and a parting layer and heating the radially extending end faces of the roll to a temperature sufficient to cause bonding together of the longitudinal edges only of at least two of the superposed strips in each convolution of the roll.

18. A method according to claim 17, wherein the strip roll is formed by forming a composite web roll comprising at least two superposed layers of elongate flexible web, at ' least one of which is formed of a material of a permeable fibrous structure, at least one of the webs being of weldable thermoplastic material and a parting layer, and cutting the web roll in a substantially radial plane or planes to provide a plurality of said strip rolls.

19. A method according to claim 17 or 18, wherein the heating is performed with radiant heat.

20. A nethod according to claim 17 » 18 or 1 , wherein the parting layer is a coating on one of the webs or strips.

21. A nethod according to clain 17 , 18 or 1 , wherein the parting layer is a non-thermoplastic web or strip positioned between convolutions of the thermoplastic webs or strips in the roll.

22. An irrigation system substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 9 of the accompanying drawings.

23. A nethod of forming flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figures 10 to 17 of the accompanying drawings.

24. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 14 of the accompanying drawings.

25. » Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 15 of the accompanying drawings.

26. Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 16 of the accompanying drawings . 27· Flexible tubing substantially as hereinbefore described with reference to and as illustrated in Figure 17 of the accompanying drawings;