EP0033570A1

EP0033570A1 - Plastics corrugated pipe

Info

Publication number: EP0033570A1
Application number: EP81200094A
Authority: EP
Inventors: Bernardus Hendrikus Kok
Original assignee: Wavin BV
Current assignee: Wavin BV
Priority date: 1980-01-25
Filing date: 1981-01-26
Publication date: 1981-08-12
Also published as: NL8000496A

Abstract

A plastics corrugated pipe (1) provided with wave crests (3) and wave valleys (2) comprising apertures (4).

A water permeable surrounding covering (13) engaging the tops of the wave crests (3) is heat-shrunk onto the plastics pipe (1), said surrounding covering (13) consisting of a foil layer 5 supporting air filled cushions (6). An outer foil layer (7) engages the tops (14) of the cushions.

Two layers of air filled cushions (6, 6a) may be connected with each other.

The outer foil layer (7) and the inner foil layer (5) are provided with perforations (8, 9).

Perforations (11, 17) may also be present in the top (14) and bottom of the cushions (6).

Description

The invention relates to a plastics corrugated pipe provided with apertures in its valleys, said pipe being surrounded by a water permeable covering.
Plastics corrugated pipes having apertures in their valleys are used on a large scale for draining purposes.
In order to prevent a blockage of the apertures by means of small soil particles, which involves a considerable decrease of the supply of water, to plastics corrugated draining pipes of this type, it is known in the art to surround the plastics corrugated pipe with glass fibre mats, or with strips of fibrous material, like for instance cocos fibres. The plastics corrugated pipe may even be surrounded with a rockwool fibre wrapping in accordance with an unpublished recent proposal.
All developments as described hereinbefore present, however, the disadvantage that they can only be difficultly applied according to a continuous method and these covered pipes are very liable to damages on conveying them or give rise to skin irritations to persons installing these covered plastics pipes in the soil.
An additional disadvantage of a surrounded plastics corrugated pipe is that the properties of the surrounding covering will not remain constant in the time, as water permeable surrounding coverings consisting of such fibres are sensitive to biological attack and/or deposits of iron oxide from soil water.
The selectivity of water permeable surrounding coverings consisting of the abovementioned materials also leaves much to be desired. Actually, a water permeable surrounding covering of a good quality has to prevent the penetration of coarse soil parts, whilst suspended very fine soil particles should be allowed to pass the surrounding covering as otherwise the water permeable covering may get blocked in the-time.
Particularly the great vulnerability of known water permeable coverings is disadvantageous.
Moreover, the water permeable surrounding covering is in most cases in contact with the respective apertures, thus causing these apertures to be partially closed.
The present invention aims to provide a plastics corrugated pipe of the abovementioned type, alleviating the aforementioned disadvantages, whereby particularly the surrounding covering is only little in weight, is not vulnerable during transport and can be applied by means of known machines for installing plastics corrugated pipes, whilst, furthermore, said pipe with surrounding covering can be supplied from a supply reel.
This object is attained in accordance with the present invention in that the plastics corrugated pipe is surrounded by a gas cushion foil layer covering, comprising one or more water permeable zones being on the one hand connected with the respective apertures and on the other hand with the surroundings of the covering.
When using such a gas cushion foil layer covering, more particularly a plastics cushion foil layer covering, the advantages are obtained that the apertures in the wave valleys are not in contact with the respective foil layer covering so-that said apertures in the plastics corrugated pipe permit an optimum water passage towards the inner side of the plastics corrugated pipe.
On the other hand the benefit is obtained that by using a gas cushion foil layer of the aforementioned type, a considerable decrease of the entering resistance is obtained, as well as a low radial water velocity and a storing ability for deposits in the channels in between the various different gas cushion;of a cushion foil layer.
An additional important advantage is that the beneficial properties of the pipe thus obtained, will remain constant in the time, as the respective filtering material is insensitive to biological attack and deposits of iron oxides.
Moreover, a plastics corrugated pipe is obtained, having a permeable surrounding covering which will not tend to get damaged during its transport and will only give rise to a slight increase in weight of the assembly, whilst on the other hand, the gas cushion foil layer may be supplied from a reel and worked up by means of a known plastics corrugated pipe surrounding apparatus.
It should be finally noted that said surrounding covering in accordance with the invention filtrate selectively, in other words, their constructions prevents a penetration of soil particles of a certain size and permits a passage of very fine soil particles which remain suspended.
According to a very preferred embodiment the surrounding covering consists of plastics cushion foil layers of small width, wrapped cross-wise around the pipe. A covering of this type will permit the respective water stream to sidewise enter below the foil whereupon said liquid will be discharged through the channel system between the cushions towards the apertures in the plastics corrugated pipe.
In another embodiment said plastics pipe is surrounded by plastics cushion foil layers, which overlap each other and which remain gathered by means of a fixation member, such as for instance a wrapped wire.
In the latter case the water likewise flows sidewise towards the overlapping regions and is subsequently displaced through the channel system between the cushions.
Said strips may advantageously be heatsealed to a mat, thus providing a covering which is easily to be installed.
In a very convenient embodiment the corrugated pipe is wrapped by a plastics gas cushion foil layer, consisting of at least three layers, whereby the outer and inner layer between the gas cushions are perforated.
A surrounding covering of this type presents the disadvantage that the apertures in the outer layer, which are smaller than the pores in the inner layer, permit the receipt of aqueous liquid comprising soil particles, whereupon the flow velocity of the aqueous liquid in the spaces between the inner and the outer foil layer is decreased in such a manner that coarse particles are deposited so that only liquid comprising very fine particles, flows through the apertures in the plastics corrugated pipe. Obviously, the outer layer may consist of a separate plastics foil which is not integral with the plastics gas cushion foil layer.
A very benificial embodiment of the present invention comprises the presence of filter material in between the gas cushions, e.g. in the form of polystyrene grains.
In another very advantageous embodiment the pipe is surrounded by a plastio₅gas cushion foil layer, comprising an inner and an outer foil layer, whereinbetween two interconnected gas cushion layers are accommodated, which are effectively interconnected in a staggered manner, under an angle of 90⁰.
In the latter case the gas cushions of such a layer are preferably sealed to each other.
So as to obtain a covering of optimum quality, it is recommended to tightly seal or the adhere by means of an adhesive the gas cushion foil layer to the plastics corrugated tube, although said gas cushion foil layer may also very advantageously be heatshrunk around said plastics corrugated tube, whereby the cushions should always be accommodated upon the outer surface of the inner layer being in contact with the pipe, as said gas cushions have a very slight wall thickness which is in any case smaller than that of the outer and inner foil layers, so that said gas cushions might easily be damaged, thus causing the desired action of the gas cushion foil layer covering to get lost.
A very good surrounding covering can appropriately be obtained by using a plastics gas cushion foil layer covering, the gas cushions of which comprise on the one hand a perforation in the layer, supporting the gas cushions and, on the other hand, in the gas cushions circumference.
The present invention will be illustrated with respect to an embodiment in the drawing, wherein:

Fig. 1 shows a first preferred embodiment of a plastics corrugated pipe, comprising a surrounding covering in accordance with the invention;
Fig. 2 shows a section through a pipe of fig. 1, according to the line II-II;
Fig. 3 shows a modified embodiment of a plastics corrugated pipe comprising a surrounding covering according to the present invention;
Fig. 4 shows another embodiment of a plastics corrugated pipe comprising a surrounding covering in accordance with the invention and
Fig. 5 still shows another embodiment of a plastics corrugated pipe comprising a surrounding covering in accordance with the present invention.

Fig. 1 shows a plastics corrugated pipe 1, comprising wave crests 3 and wave valleys 2, the wave valleys 2 comprising apertures 4, allowing entrance of water, flowing towards the inside of the plastics corrugated pipe, thus enabling said plastics corrugated pipe to be used for draining operations.
The plastics corrugated pipe 1 is surrounded by a water permeable covering 13 being heat shrunk around the outer side of the plastics corrugated pipe. The inner foil layer 5 of the surrounding covering 13 adjoins the wave crests 3 of the plastics corrugated pipe. Due to the shrinkage of the tubular covering 13 around the plastics corrugated pipe, a very good connection with the wave crests 3 is obtained, but on the other hand the wave valleys comprising the apertures 4, will remain free from said water permeable covering 13.
Air filled cushions 6 are disposed upon the foil layer 5, the tops 14 of said cushions being connected with an outer foil layer 7. Although a welding connection or glue connection 15 may be present at the location of contact between the top 14 of the cushions 6 and the outer foil layer 7, said presence is not essential, as also a foil layer 7 can be used which is disposed undetached with respect to the gas cushion foil-layer comprising the foil layer 5 with the air-filled gas cushions 6. In the latter case the outer foil layer 7 and the gas cushion foil layer 5, 6 are both heatshrunk around the plastics corrugated pipe 1.
For the supply of water to be discharged from the environment of such a plastics corrugated pipe comprising a water permeable surrounding covering 13, the outer foil layer 7 comprises perforations 8, which debouch into spaces 16 inbetween the air-filled gas cushions 6. On the other hand the inner foil layer of the surrounding covering 13, to wit the foil layer 5, is also provided with perforations 9 via which liquid entering through apertures or perforations 8 in the outer foil layer 7, flows into the spaces 16 and from that location into the wave valleys 2 of the plastics corrugated pipe 1, via perforations or apertures 9. The outer foil layer may also consist of a tubular fine gauze net of plastics and such a tubular net may also be accommodated around the outer circumference of the corrugated pipe between the foil layer 5 and the wave crests 3. This net also acts as a filtering layer.
It is recommended that the apertures or perforations 8 in the outer foil layer 7, are smaller than the apertures or perforations 9 in the inner foil layer 5, as in that way water entering through said apertures or perforations is unable to entrain coarse particles and deposit them in the spaces 16, so that said spaces 16 only receive water comprising finely dispersed particles being deposited in said spaces, due to the very decreased flow velocity prevailing in said spaces 16, prior to the water removal through the apertures or perforations 9. However, the size of the perforations 9 may be also equal to or smaller than that of the perforations 8, dependent on the surrounding soil.
In order to surround a plastics corrugated pipe 1, a water- permeable covering is reeled from a storage reel, said water permeable covering consisting of an inner foil layer 5 and an outer foil layer 7, whereinbetween air cushions 6 are situated, which covering has a width being slightly larger than the circumference of the plastics corrugated pipe at the location of the wave-crests. Parts of the covering overlapping each other are subsequently sealed together and the covering thus obtained is heat shrunk around the plastics corrugated pipe 1, due to a heat treatment. It will be obvious that, dependent upon the amount of performed shrinkage, the used gas cushion foil layer can be subjected to greater or smaller deformations, thus permitting the cross-section of the flow channels formed by the spaces 16 between the air cushions 6 to be varied, so that a so-called coarse or fine filter can be obtained from one and the same gas cushion foil layer.
It will be clear that the perforations or apertures 8 and 9 are preferably not facing each other, as under those conditions an optimum decrease of the flow velocity of the liquid in the flow channels 16 can be obtained.
Fig. 3 shows a modified embodiment of the present invention wherein the plastics corrugated pipe is surrounded by a water permeable covering 13, consisting of two gas cushion foil layers, one gas cushion foil layer consisting of an inner foil layer 5 being provided with perforations 9 debouching into the spaces 16 between adjacent gas cushions 6, whilst a second gas cushion foil layer comprises an outer foil layer 5a, and gas cushions 6a, which are separated from each other by spaces 16a. As the gas cushions 6 and 6a present a staggered pattern with respect to each other, spaces are formed by the flow channels 16, 16a, so that liquid, entering through the apertures or perforations 8 in the outer foil layer 5a, is able to flow towards the apertures or perforations 9 in the inner foil layer 5.
The gas cushions 6 and 6a which preferably present a staggered pattern with respect to each other, may either be interconnected by means of an adhering layer 12, or by a sealed connection 12.
Fig. 4 still shows another embodiment in which a water permeable tubular covering 13 is used, which has also been heat- shrunk around the plastics corrugated pipe-I. In order to admit liquid to the apertures 4 of the corrugated pipe certain cushions 6 comprise a perforation 17 in their tops 14 and a perforation 11 in their bottom part. The liquid to be discharged flows into cushions 6 via perforations 17 and subsequently through perforations 11 into the wave valleys 2 from which said liquid arrives in the plastics corrugated pipe 1 via apertures 4.
Care should be taken that a number of gas cushions 6' remain unperforated, in order to ensure an optimum surrounding of the plastics corrugated pipe.
Manufacturing a foil layer as described in the latter embodiment, is simpler than that as described in the preceding embodiments.
Fig. 5 still shows another embodiment in which the surrounding covering consists of strips of plastics gas cushion foil which are applied in an overlapping way and being kept together by a wire 18. At the location of the overlappings 19, ambient water will flow into the pipe via said overlapping parts 19; Consequently the supply of water occurs in region 20.
Instead of oblong strips of gas cushion foil layer, crosswisely wrapped gas cushion foil layers can also be used as a surrounding covering as the advantages in accordance with the present invention are also obtained by means of the latter solution.
In order to obtain an optimum surrounding covering preferably an initial gas cushion foil on reels is used, the length of which equals the length of a plastics corrugated pipe, which length generally amounts to maximally 200 m. By sealing together the overlapping parts of the gas cusion foil, the desired covering is obtained. Said covering is subsequently very conveniently subjected to a heat-shrinkage, which results in an optimum surrounding of the outer circumference of the plastics corrugated pipe.
When a plastics corrugated pipe is used, comprising a gas cushion foil, of which certain cushions are perforated, a small diameter of the gas cushions of for instance 6 mm is preferably used.
The spaces 16 and 16a of the cushion foil layer of fig. 3 may advantageously be filled up with filtering means e.g. with polystyrene grains. Said grains may also be applied in the spaces 16 of the gas cushion foil layer as used in fig. 4.
It will be obvious that a suitable choice of the diameter, height, distance and perforation dimensions of the respective cushions will permit obtaining a gas cushion foil layer, the texture of which is coarse or less coarse, so that the covering to be applied can be adapted to the type of soil where the plastics corrugated tube has to be installed.
It goes without saying that a biochemical attack will not occur in the plastics foils used as a surrounding covering, whilst furthermore a blockage of apertures by iron oxide will not be exhibited. The mechanical strength of the respective assembly should be thus, that it is able to endure any applied load of soil. On the other hand a breakage or tearing of some cushions will not impair the filtering action aimed at.
The plastics air cushion foil layer advantageously consists of a polyethylene plastics cushion foil layer, although a polypropylene cushion foil layer is very suitable as well. Particularly when longitudinally wrapping a plastics corrugated pipe with a plastics gas cushion foil layer an axial inlet is obtained, through which ground water may flow towards the corrugated pipe.
If desired, the gas cushion foil layer may also be attached by means of a clamping member.
In another embodiment the gas cushion foil layer is provided with an adhesive at its inner side, so that the surrounding covering can be directly adhered to the corrugated pipe by means of the adhesive.
In case of surrounding the corrugated pipe by longitudinally applying the gas cushion foil layer, the overlapping edge parts of the gas cushion foil layer may also be fixed to each other by means of an adhesive which has previously been spplied onto the first foil layer.

Claims

1. Plastics corrugated pipe 1 being provided with apertures in its wave valleys 2, said pipe being surrounded by a water permeable covering 13, characterized in that
the plastics corrugated pipe (1) is surrounded by a gas cushion foil layer covering (13) comprising one or more
water permeable zones (8, 9) being on the one hand connected with the respective apertures (4) in the plastics corrugated pipe 1 and on the other hand with the surroundings of the covering.

2. Plastics corrugated pipe according to claim 1, in which gas cushion foil layers (13) of small width are wrapped cross-wise around the plastics corrugated pipe (1).

3. Plastics corrugated pipe according to claim 1, in which the plastics pipe (1) is surrounded by gas cushion foil layers (5, 7) which overlap each other and which are kept together by a fixation member (18).

4. Plastics corrugated pipe according to claim 1, in which the plastics pipe is wrapped with a mat comprising two layers of plastics gas cushion foil with gas cushions (6p 6a).

5. Plastics corrugated pipe according to claim 1, in which the two foil layers are so positioned with respect to each other that linear water supply channels (16, 16a) are formed.

6. Plastics corrugated pipe according to claim 5, in which the two foil layers (13') extend into the same direction or in a staggered pattern with respect to each other, preferably under an angle of 90°.

7. Plastics corrugated pipe, according to claim 1, in which the gas cushions (6, 6a) of the plastics gas cushion foil layer (5, 5a) are perforated by perforations (17,11).

8. Plastics corrugated pipe according to claim 1, in which the corrugated plastics pipe (1) is surrounded by a plastics gas-cushion foil layer (13) at least consisting of three layers, the outer layer (7) and the inner layer (5) between the gas cushions (6) being provided with perforations (8, 9), the diameter of the perforations (8) in the or smaller outer foil layer (7) being equal to or greater/than that of the perforations (9) in the inner foil layer (5).

9. Plastics corrugated pipe according to claim 1, in which the pipe is surrounded by a plastics gas cushion foil layer, comprising an outer and an inner foil layer (5a,5) whereinbetween two interconnected gas cushion layers are accommodated (6, 6a), preferably the gas cushion layers (6, 6a) being interconnected in a staggered manner and/or the gas cushions (6, 6a) are sealed to each other.

10. Plastics corrugated pipe according to any one or more of the preceding claims, in which the plastics pipe comprises one or more of the following measures:

a) a tubular gas cushion foil layer (13) has been heat shrunk around the plastics corrugated pipe (1);

b) gas cushions (5, 6) are always accommodated upon the outer surface of the inner layer (5) being in contact.with the wave crests (3) of the corrugated plastics pipe (1);

_c) the covering (13) forms an axially extending water inlet;

d) a filter material is present in the spaces (16, 16a) between adjacent gas cushions;

_e) the covering (13) is fixed to the crests by means of an adhesive or by heatsealing;

f) overlapping edge parts of the covering (13) are con- _nected with each other by means of heatsealing or an adhesive;

g) the outer foil layer (7) consists of a net of fine gauze, preferably a tubular net of plastics;

h) a net of fine gauze, preferably a tubular net of plastics is accommodated between the outer side of the top (3) of the wave crests and the gas cushions (6).