Patent Application
20070252023
The invention relates to a tube system for supplying a fluid, that is, for supplying liquids or gases, in particular water, preferably for subsoil irrigation of the type cited in the preamble to claim 1.
In such tube systems it is important that small defined fluid quantities are supplied in order to assure a continuous or semi-continuous supply over extended intervals of time without complex regulating mechanisms and to be able to use the smallest possible quantities of fluid.
Preferred areas of application are subsoil irrigation of large areas of vegetation, aeration of waste water channels or contaminated waters, and the regeneration of contaminated soil, whereby the tube systems can also be employed above the surface of the soil.
A significant disadvantage of most of the previously known tube systems is that they do not assure a uniform supply of the fluid over extended distances and/or in hilly terrain without controls that are quite complex.
Known from CH 321 765 is a spray irrigation tube that comprises at least two conduits, and the fluid flows out through the spray apertures in the wall thereof. However, the spray pressure exerted on the spray apertures disadvantageously drops as the distance from the feed site increases.
This is also true for the system known from DE 202 11 742 U1, in which however a plurality of parallel membrane tubes are filled with fluid via controlled valves.
For a uniform fluid supply, tube systems having large fluid outflow quantities per length interval and time interval, e.g. several liters per hour and meter, require a pump technology with a high peak performance, even for short operating intervals, which is complicated and expensive and is furthermore susceptible to problems. It is only with such a technology that, first of all, the small quantity of fluid outflow per length interval and unit of time that is desired in the current means is possible, and secondly, an approximately uniform supply of the fluid through long lengths of tube is possible. The major drop in pressure per unit of length with high outflow quantities that occurs when not enough fluid is delivered is responsible for the uneven supply.
In any case, the maximum length for a tube system having only a single feed site for the fluid itself when employing high performance pump technology during the use of most conventional tube types is limited by the pressure of the fluid quantity supplied, since the drop in pressure that occurs over long tube lengths automatically leads to a reduction in this quantity and thus to uneven fluid output, and thus in particular leads to uneven irrigation.
Therefore a reduction in the outflow quantity due to the fluid pressure in the tube has only very limited efficacy, since it automatically leads to short tube lengths with which a somewhat uniform fluid supply can still be attained.
In agriculture and gardening, types of tubes with very small individual holes for direct transfer of the fluid to the adjacent soil can be used to supply small fluid quantities over longer lengths. However, over time these types of tubes are extremely susceptible to problems because the holes become clogged with impurities, in particular when there is an extended interruption in the irrigation, e.g. outside of the growing season, or even extremely fine hair-like roots growing into the tubes.
Some remedy for this is provided by the pressure-independent tube system known from EP 0 824 306 B1, in which an elastic inner tube that has outlet apertures is disposed inside an outer tube that acts as a protective cover and that has a slit-like aperture running along a cover line. In this system, pressure-independent provision of the fluid is to be attained using the pressure-dependent deformation of the inner tube cross-section. However, in many applications, e.g. in subsoil irrigation, this system has the disadvantage that during extended periods without pressure, that is e.g. during periods of maintenance work or non-irrigation periods outside of the growing seasons, there is irreversible deformation of the tube cross-section, e.g. due to the pressure of the soil, so that the properties of the tube have been disadvantageously changed when operations begin.
Apart from this, the system known from EP 0 824 306 B1 is complex and fraught with problems during production and handling, having an outer intake conduit with high tensile strength and with a non-closed cross-section and having where necessary a filter material inserted between the actual elastic inner tube that supplies or takes up the fluid and the slitted outer tube, and having an elastic reinforcement for stabilizing the system.
Finally, with this system there is the risk that roots will penetrate through the relatively wide gap in the outer tube into the system and damage it over time.
FR 2 713 044 A1 describes a system comprising an inner tube and an outer tube in which the outer tube comprises porous material. The dimensioning of the tubes should be such that for attaining a uniform water output the pressure is reduced in two stages, for which purpose the pores of the outer tube must have a relatively large cross-section compared to the portioning apertures of the inner tube.
This tube system has the profound disadvantage that the quantity of water output is largely a factor of differences in elevation in the terrain to be irrigated.
This disadvantage is avoided in the system known from U.S. Pat. No. 3,874,598 in that the buffer volume between outer tube and inner tube is divided into individual provision chambers. However, in this solution the outer tube does not comprise a porous material with fine pores. On the contrary, in this solution the apertures of the outer tube are significantly larger than the apertures of the inner tube. In addition, with this tube it is not possible to assure uniform water supply on inclined terrain when segment lengths are in the meter range.
The underlying object of the invention, proceeding from the tube system in accordance with FR 2 713 044 A1 with the features cited in the preamble to claim 1 is to fashion this system such that the aforesaid disadvantages are avoided, while also providing in the inventive system an outer stable protective cover in which is arranged a more flexible inner tube that supplies the fluid.
The object is attained with the features provided in claim 1.
According to the basic idea of the invention, the buffer chamber between the outer tube and the inner tube is divided into individual provision chambers, as in the solution in accordance with U.S. Pat. No. 3,874,598, into each of which chambers a portioning hole of said inner tube opens, the cross-section of the apertures of the outer tube being significantly smaller however than the cross-section of the apertures of the inner tube.
Together with the dimensioning of the apertures, the effect of this segmentation is that when the tube system is not placed horizontally, the tube surroundings in more elevated and in lower areas is uniformly supplied with adequate pressure and with an adequate quantity of fluid.
The result of the dimensioning of the pores and portioning holes, which preferably correspond to the suggestion in accordance with claim 14, is that the fluid fed via the inner tube into the intermediate space between inner tube and outer tube does not flow out into the tube surroundings through the apertures of the outer tube that are smaller in cross-section until there is a certain pressure.
As in the known system, in this case as well the outer tube assures resistance against environmental factors. Suitable for instance are porous tubes with high stability, e.g. membrane tubes with a wall thickness of dA=5 mm and an inner diameter of DA=1.5 inches.
Such tubes are resistant to ground pressure, soiling, and the growth of very small roots, which is due in particular to the large number of small fluid outflow apertures, that is pores e.g.
Due to the dimensioning of the cross-sectional apertures, a buffer volume builds up in the intermediate area between inner tube and outer tube, and it acts as a fluid reservoir and therefore ensures that fluid provided via the inner tube travels via the portioning holes into the intermediate area between inner tube and outer tube at a higher pressure, e.g. a pressure of several bars, and that the fluid is supplied to the tube surroundings from this intermediate area through the fine apertures of the outer tube, e.g. a porous fabric.
The portioning holes of the inner tube can also possess complex functions and properties, e.g. they can be pressure-compensating or self-cleaning.
Options for self-cleaning holes are e.g. the subject-matter of claims 19 and 20.
In accordance with claim 2, the segmentation suggested with the invention can be attained in a simple manner in that the outer tube is provided with constrictions that are preferably positioned equidistant against the outer side of the inner tube.
In accordance with another variant provided in claim 3, for forming the provision chambers the inner tube preferably has equidistant annular convexities that are positioned against the inner surface of the outer tube.
This variant offers a number of important configuration options when, as provided in claim 4, the wall thickness of the inner tube, which comprises elastic material, is thinner in the area of the annular convexities compared to the adjacent inner tube walls so that when the fluid pressure is increased in the interior of the inner tube the annular convexities are positioned against the adjacent inner tube walls.
Thus according to the suggestion in accordance with claim 5, it is possible to have self-segmentation of the buffer chamber by means of the annular convexities by adjusting the pressure in the inner tube.
This configuration possibility opens up a number of new options when, as suggested in claim 6, the inner tube and the buffer chamber can each be connected via controllable valves to a discrete fluid source, preferably to a water connection and/or a compressed air source.
Thus for instance according to the suggestion in accordance with claim 7, if a fluid, preferably water, is fed directly into the buffer chamber, for the purpose of rapid irrigation, it is possible to eliminate the segmentation, specifically with a reduction in the pressure in the inner tube. In this case the tube system has a water outflow rate that is the same as the simple membrane tube.
Another advantage is that when the segmentation is deactivated, that is, when the pressure in the inner tube is reduced, the entire tube system can be cleaned very effectively. For this purpose, according to the suggestion in accordance with claim 8, a fluid, preferably water or compressed air, is to be fed under high pressure into the inner tube and/or the into the buffer chamber while reducing the pressure in the inner tube. Using this measure the particles clogging the portioning holes or pores can be effectively removed.
In this, the pressure can be varied, as is suggested in claim 9, or in accordance with claim 10 the pressure can be generated in brief pressure shocks at time intervals.
In accordance with another variant that is provided in claim 11, the inner tube can comprise elastic material such that it is positioned across its entire length on the inner wall of the outer tube when the fluid pressure increases, which eliminates the entire buffer chamber for a period so that the fluid flows out of the inner tube directly through the porous outer tube in the vicinity of the portioning holes of the inner tube.
If there is no self-segmenting of the buffer chamber, in accordance with claim 12 the constrictions of the outer tube or the convexities of the inner tube can be joined fluid-tight, preferably welded, to the inner tube.
If the tubes comprise thermoplastic material, the result is simple production using a tool to be employed from outside that effects heat deformation when in accordance with claim 13 the material of the outer tube possesses a lower melting point than the material of the inner tube. Materials suitable for the outer and inner tube are fundamentally polymer materials, and in accordance with claim 14 in the context of task distribution the inner tube should have a higher elasticity than the outer tube.
With the measures described in the foregoing it is possible to rinse and clean the inventive tube system in order to clean the holes or pores of the tube that have clogged with calcium particles, rust particles, or the like. According to the suggestions in accordance with claims 19 and 20, this cleaning can be further supported by the design of the portioning holes or the inner tube.
With these measures, using the elasticity of the inner tube, the design of the portioning holes provides that intentional variation of the difference in pressure between inner tube and buffer volume leads to an effective “kneading” process in the immediate environment of the portioning holes. In accordance with claim 19, the portioning holes of the inner tube can be funnel-shaped. In accordance with claim 20, the wall of the inner tube is somewhat indented in the area of the portioning holes and has a thinner wall thickness in this area.
Using the aforesaid “kneading” process, even stubborn layers and encrustations in the hole area can be loosened and rinsed out. In this manner the use of the tube system is assured for a very long period of time.
In the inventive embodiment of the tube system, the fluid outflow quantity is practically not affected by the elastic properties of the inner tube and outer tube, it does not depend on the e-modulus of the materials used, and there is therefore also no relationship to the temperature at which the tube system is used.
The additional filter shell suggested e.g. in EP 0 824 306 B1 is not necessary per se with the inventive solution. However, as suggested in claim 24, it can be advantageous to insert upstream of the tube system an input filter that filters out impurities such as e.g. suspended organic and inorganic particles.
Nor is there any need for additional reinforcement of the tube system when the material of the outer tube has the required stability. Likewise, the chemical composition of the outer tube can be selected such that the tube has adequate protection against destruction by environmental factors, e.g. even by rodents.
In the context of the invention explained in the foregoing, in accordance with claim 15 the outer tube comprising porous material can be embodied e.g. as a soaker tube, floating tube, or membrane tube.
In order to attain its flexibility with the required resistivity, in accordance with claim 16 a mixture of rubber and polymer substances is suggested for the material.
For ensuring that the fluid flows out uniformly over great distances it is particularly important to match the position of the provision chambers and the number of portioning holes of the inner tube that open into said provision chambers such that the loss in pressure in the inner tube that is a factor of the tube length and the reduction in the quantity of the fluid flowing out through the portioning holes of the inner tube that is caused thereby is compensated for attaining a constant fluid outflow quantity per unit of length of the tube system, as is provided in claim 21.
The effect sought with the invention is significantly enhanced in that according to the inventive suggestion the material of the outer tube is selected and its apertures are dimensioned such that they do not open unless a pre-specified pressure threshold is exceeded, preferably 0.3 bar. The result of this is that below a certain pressure the outer tube does not permit the fluid to pass, that is, it is sealed, and above this pressure the pressure threshold increases the fluid outflow quantity supplied proportional to the increase in pressure after a certain non-linear transition area.
This results in the properties, explained in the following, that make the inventive tube system practically universal for a wide variety of irrigation tasks.
1. When the tube is placed horizontally, e.g. for irrigating grassy surfaces in sports stadiums, first the buffer volume between the two tubes fills completely with fluid flowing out due to the water pressure in the inner tube, which must be greater than the threshold for the pressure in the outer tube. Since the gravitational pressure of the fluid in the normal tube diameters, which are in the centimeter range, is imperceptibly small, no fluid flows out until the pressure in the filled buffer volume exceeds the threshold for the outer tube. The following pronounced advantages result from this:
2. The pressure threshold suggested in claim 18 for the outer tube has a particularly advantageous effect when placing the tube system in hilly terrain.
With elevation differences Ah that correspond to gravitational pressure PG for the fluid, which is small compared to the threshold pS, as described the buffer volume and in particular the buffer volume segmented into provision chambers fills with fluid such that the fluid flows out largely uniformly across the length of the tube system, preferably the entire segment area. In this case the lengths of the provision chambers should be dimensioned such that the tube parameters, specifically the fluid pressure in the inner tube, the portioning hole diameter, and the threshold, are matched to one another in an optimum manner in terms of a uniform fluid supply.
In this case it should in particular be avoided that the lengths of the provision chambers are so large and the flow-through quantities through the portioning holes of the inner tube are so small that, due to the effect of the gravitational pressure in provision chambers that are placed lower on the whole with the inner pressure building up in the buffer volume, a significantly higher outflow quantity of fluid through the outer tube results than in the provision chamber placed higher. In this case an optimum must be found for the terrain, and it is possible to use relatively short provision chambers, into which naturally a required number of portioning holes must open, to attain a largely uniform supply of the fluid across the tube length.
With the inventive tube system, it is possible to supply a fluid, preferably water, across long lengths up to several kilometers. The surface of the outer tube is fashioned such that its function is not negatively impacted by long-term effects such as soiling the fluid outlet apertures or roots growing into these apertures. In this case the material can be selected such that the tube system is flexible and stable, such that it can be placed with no problem using conventional technology, but such that on the other hand it is protected against deformations by the pressure of the ground or vehicles that can limit functions.
There are two further options for the tube system, and these are the subject-matter for claims 22 and 23.
In accordance with claim 22, it is possible to add completely soluble fertilizers via the tube system, e.g. during irrigation of vegetation, this permitting extremely effective and inexpensive fertilization.
According to another suggestion in accordance with claim 23, the system is also suitable for subsoil heating, e.g. of grassy surfaces in sports stadiums. In this case it is merely necessary to supply adequate heating capacity via the fluid. In this application it is possible to use the self-segmentation to attain high-performance heating in that the heated fluid is added to the surrounding ground via the puffer chamber.
The subject-matter of the invention is explained in detail in the following using the exemplary embodiments, which are schematically depicted in the drawings.
This tube system comprises a porous mechanically and chemically stable material.
Arranged inside the outer tube 2 is an inner tube 2, the exterior diameter D1 of which is smaller than the interior diameter DA of the outer tube 1. Thus an annular space forms between the outer tube 1 and the inner tube 2; hereinafter it is called the buffer volume or buffer chamber 5.
The inner tube 2, which preferably comprises a fluid-tight material, has apertures distributed across its length, hereinafter called portioning holes 4.
Flowing through the inner tube 2 that is connected to a fluid source is a fluid 3, preferably water, under a pressure pF that ranges from 1 to 8 bar, depending on the length of the tube system.
The fluid 3 travels via the portioning holes 4 into the annular buffer chamber that forms a buffer volume 5 and that fills with fluid until the fluid pressure pV prevailing therein is greater than the pressure threshold pS determined by the material of the outer tube 1. Then the fluid flows out into the tube surroundings 9.
The choking effect of the outer tube 1 can be attained with a tube comprising porous material, e.g. a soaker tube, floating tube, or membrane tube.
Since the quantity of the fluid 6 flowing through the outer tube 1 in general is greater than the quantity supplied through the portioning holes 4 into the buffer volume 5, after a certain period of time the pressure in the buffer volume pV collapses, so that the outflow of fluid 6 is interrupted until a pressure pV that is greater than the threshold pressure pS has built up again in the buffer volume.
Thus, using this buffer volume the outflowing fluid 6 is automatically regulated corresponding to the rate of the fluid flowing out through the portioning holes 4.
When the material selected for the outer tube 1 is suitable, the distance between portioning holes 4 and the pressure pF of the fluid in the inner tube 2 can be matched to one another such that the quantity of the outflowing fluid 6 is largely constant across long lengths of the tube system.
Materials that are suitable for inner and outer tubes 1 and 2 are polymer materials, whereby the inner tube 2 should comprise a flexible, fluid-tight polymer material, while the outer tube can comprise a more stable, but still flexible, porous polymer material. Mixtures of rubber and polymers have proved themselves for materials. This material selection attains sufficient flexibility with good robustness and high resistivity to external factors.
Differences in elevation in the terrain in which the hose system is to be placed have a negative impact on the outflow quantity due to the gravitational pressure pG that acts on the fluid and that is a factor of the elevation difference Δh, so that a uniform fluid outflow cannot be attained with the system in accordance with
For such cases, the inventive design of the tube system depicted in
A largely constant fluid supply is made possible, even when there are major inclines in the terrain, by appropriately adapting the length 1 of the provision chambers 8 and the number of portioning holes 4 that open into each chamber 8.
This property is promoted in that that porous material of the outer tube 1′ is selected such that it possesses a pressure threshold pS that must be overcome for the fluid to flow out.
In this case the outflow characteristics that result are those illustrated graphically in
If the pressure pV in the provision chamber 8 is less than the pressure threshold pVS, no fluid flows out.
V/L=0
If the pressure pV exceeds the threshold value pVS, the fluid volume V/L related to the length unit initially quickly increases in a non-linear manner, and then at higher pressures ultimately runs approximately proportional to the pressure p.
Despite these advantageous properties, however, porous outer tubes can also be used whose material does not cause a pressure threshold pS.
In this case the fluid flows out into the surroundings the portioning holes of the inner tube directly through the wall of the outer tube so that the fluid does not flow out uniformly in the tube surroundings. However, this can be tolerated e.g. for subsoil irrigation because the soil ensures uniform distribution of the fluid due to diffusion.
Even when the tube system is placed on an incline, outer tubes without a pressure threshold can be used if the tube system is segmented as
If the entire length of the inner tube 2 comprises highly elastic material, as
If, as is also possible, the material of the outer tube 1′ possesses a pressure threshold, a small buffer volume (not shown) forms in the vicinity of each portioning hole 4, from which the fluid flows outward when its pressure exceeds the threshold pressure.
If this working pressure pF in the inner tube is reduced to a value that is less than or equal to the inner pressure pV in the buffer chamber, that is, in the provision chambers 8, the bulges 7′ move back so that the segmentation is eliminated, as depicted in
This design enables a number of working options.
The most water-saving supply of water results when the inner pressure pF in the inner tube 2 is greater than the inner pressure pV in the provision chambers 8 so that the result is the setting in
In contrast, if more water supply is desired, the working pressure pF in the inner tube 2 must be reduced until the setting in accordance with
This setting moreover enables rinsing and thus cleaning of the tube system, as is explained in detail in the following using
In order to enable this cleaning, inner tube 2 and outer tube 3 are each provided with controllable valves 23 and 24 or 25 and 26 at the input and output, as illustrated in
If the inner tube 2 is to be cleaned, valves 23 and 24 are opened so that fluid can flow through under pressure.
In like manner, for cleaning the buffer chamber 5, the valves 25 and 26 are opened in order to enable unimpeded flow of the fluid. The cleaning of the buffer chamber 5 naturally requires that the segmentation according to the depiction in
If it is intended that the pores of the outer tube 1 are to be cleaned, the valve 26 must be closed so that the fluid is pressed through the pores.
If water is used for cleaning, in some cases this can lead to silting of the ground due to the amount of water supplied during the cleaning procedure. To avoid this, a compressed gas, preferably air, can be added to the buffer chamber 5 instead of water, and it enters the tube surroundings, that is the ground, through the pores of the outer tube 1.
In the irrigation mode, all of the valves 24, 25, and 26 should be closed except for the valve 23.
The circuit depicted schematically in
In the other switch position, the three-way valve 15 connects the inner tube 2 via lines 20 to a reservoir 21 for a cleaning agent. This cleaning agent is circulated by means of circulation pump 19 and is added to the inner tube 2 via a three-way valve switched between the cleaning valve 22 and the input for the inner tube 2.
The tube system can be cleaned very well e.g. when placed in the ground by means of such an arrangement. A cleaning cycle could proceed e.g. as follows:
This circuit, together with the inventive self-segmentation of the tube, makes possible various applications for controlled irrigation, cleaning, adding of fluid and gaseous fluids, and heating.
This arrangement is primarily for basic cleaning of the entire tube system, whereby it is possible to clean the most sensitive sites in the system in a controlled manner, specifically the portioning holes in the inner tube, and to protect them against soiling, without great complexity. Such basic cleaning does not have to be performed except after long intervals of time, e.g. non-irrigation seasons.
Other options for self-cleaning of the portioning holes are illustrated in
This “kneading” process in the immediate vicinity of the portioning holes can be attained using the designs for the hole cross-sections illustrated in
The portioning hole 12 depicted in
Modifications to this funnel-shaped cross-section of the hole are illustrated in
Another variant of the portioning hole that promotes self-cleaning by “kneading” is illustrated in
As soon as the working pressure pF in the inner tube 2 is increased, the indentation 13 bulges out of the position illustrated in
Legend
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 058 858.9 | Dec 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/12815 | 12/1/2005 | WO | 6/5/2007 |
