WO2000062597A1

WO2000062597A1 - Plastic sheet with shaped pockets along its sides for weight insertion

Info

Publication number: WO2000062597A1
Application number: PCT/GR1999/000016
Authority: WO
Inventors: Asterios D. Daios
Original assignee: Daios Asterios D
Priority date: 1999-04-19
Filing date: 1999-04-19
Publication date: 2000-10-26
Also published as: SK2792002A3; GR990100128A; HUP0202507A2; GR1003766B; CZ2002677A3

Abstract

The invention refers to a plastic sheet for agricultural use (ground covering of any linear cultivation or any linear cultivation under low tunnels). For the firm fixing of plastic sheet (1) on a cultivation line, complex shaped pockets (9, 10) exist in which weight is inserted during its use on the field. The complex shaped pockets (9, 10) are formed by a complex shaped welding of two superimposed parts of the plastic sheet (1) along its sides. The complex shaped pockets (9, 10) along the two sides of the sheet (1) comprise two series of pockets of which one (10) can facilitate water or and the other (9) can facilitate soil. The advantage of this pattern is that the farmer can fix the plastic sheet (1) on the low tunnel or on the characteristic dyke of the asparagus cultivation, by either using soil or water or even both of the above.

Description

PLASTIC SHEET WITH SHAPED POCKETS ALONG ITS SIDES FOR WEIGHT INSERTION

The invention refers to a plastic sheet for agricultural use (ground covering of any linear cultivation or any linear cultivation under low tunnels). For the firm fixing of plastic sheet on a cultivation line, complex shaped pockets exist in which weight is inserted during its use on the field. The complex shaped pockets are formed by a complex shaped welding of two superimposed parts of the plastic sheet along its sides. The complex shaped pockets along the two sides of the sheet comprise two series of pockets of which one can facilitate water or and the other can facilitate soil. The advantage of this pattern is that the farmer can fix the plastic sheet on the low tunnel or on the characteristic dyke of the asparagus cultivation, by either using soil or water or even both of the above.

The plastic sheets, which are used in ground covering or in any cultivation under low tunnels, can be divided in two categories depending on their application and their use: a) The conventional plastic sheets, which during their application on the cultivation line are fixed by setting soil, manually or by a mechanized process, on the surface of the sheet along the two sides. The production process of these sheets is fairly simple and so is their application on the field. The main drawback of this type of plastic sheets is the hindrance on performing the required cultivation procedures on the cultivation line and as a result their application is unsuitable for any linear cultivation (e.g. for asparagus).

b) The sheets that allow access to the cultivation line, which are more complex and have pockets for weight insertion along the two sides, are able to fix the sheet on the cultivation line. The only category which has been widely adopted is the one in which, soil is used as weight (abounds in the field and does not add any further cost). There are other categories for example the one which utilizes water (which also abounds in the field and does not add any further cost). However farmers are cautious about using water due to the fact that any damage inflicted on the pockets leads to water leakage and therefore these sheets are characterized as unsuitable.

Several other solutions have been applied like the insertion of ropes along tubes formed on the sides of the sheet or tying the plastic sheet (several ways can be adopted) at regular distances in order to achieve its firm fixing. These solutions have only been employed to an experimental level.

The existing solutions although they allow access to the linear cultivation (e.g. asparagus which is linearly cultivated in artificial dykes) they have several disadvantages. Some of them can be briefly discussed:

a) They are not easily reused. This is an important disadvantage considering the relatively high cost of these sheets and the environmental issues which arise (recycling). b) The actual application cost when soil is used. c) The insecurity that the use of water is bind to. d) The fact that the above solutions are not widely accepted. This leads the plastic sheet producers to the necessity of having two products on their disposal. e) The designing of the volume of the pockets is based upon the maximum wind velocity which is not necessary in most cases.

From the description of the above it is clear that both solutions which contain either the use of soil or the use of water have some advantages but they are simultaneously disadvantageous when considered on their own.

The complex problems of the usual access allowing plastic sheets and ground covering methods are solved by the present invention of the complex shaped weight insertion pocket plastic sheet with an innovative solution:

The plastic sheet has on both sides two series of different pockets instead of one. One of them is filled with soil whereas the other is filled with water.

This solution combines the advantages of both the water and soil pockets. Furthermore it is a solution which combines the simplicity of the use of water, the readily distributed weight due to its fluidity, and the assurance to the user of an alternative solution in case the water pockets are damaged.

It is apparent that this invention automatically solves all the above mentioned problems.

The end user can have a plastic sheet which can be used in four different ways:

a) By filling with soil only the pockets designed to be filled by soil (the water pockets remain empty). This solution involves a low cost material but has high labour cost and demands careful filling of the pocket along the whole length. b) By filling with water only the pockets designed to be filled with water (the soil pockets remain empty). This solution drastically reduces the labour cost but requires the usage of special equipment for feeding the water pockets. c) By filling both the water and soil pockets. This solution is recommended in areas where windy conditions prevail. d) By filling some parts of the length of the sheet with water and some others with soil. This solution is mainly applied when the plastic sheet is used for more than one year, when several pockets have been damaged.

Several combinations can be adopted to meet the end users requirements and in addition it simplifies the production of the plastic sheet since only one type of plastic sheet is produced for all possible uses.

A different possibility arises when the plastic sheet has two series of weight insertion pockets of the same type (e.g. two series of soil pockets on its side). This solution is most suitable for users who support one of the solutions (either only soil or only water) and they intent to use the sheet for more than one year. Hence if two series of consecutive pockets exist one of them can be used in the first year and it can be deliberately destroyed to empty the content of the pockets when collected from the field. In the second year the remaining series of pockets can be used. The same applies to the solution of water pockets.

The durability of the plastic sheet is assured by using raw materials which exhibit exceptional tear and puncture resistance. Thus a polyolefin or a combination of polyolefins could be used as raw material (LLDPE, LDPE, mLLDPE, EVA, PP).

Moreover additives could be blended with the raw material to attain the required properties (colour, resistance to degradation, thermal properties etc). The combination of the durability of the plastic sheet and the existence of two different types of pockets along the sides of the sheet provide the ability of lasting for more than one year. The farmer can select to use the water pockets in the first year and the soil pockets in the next year. Moreover there is the possibility to use the water pockets -since they can be easily emptied when this is required (due to their formed shape)- for more than one year and thus to prolong the service life of the sheet.

In addition both solutions can be used simultaneously in areas where windy conditions prevail, by actually doubling the inserted weight. This provides indirectly the opportunity for designing the plastic sheet in such a way as to withstand the most extreme wind conditions and at the same time each pocket can be designed so that its volume is sufficient for milder weather conditions.

The invention is described by referring to the following figures: Figure 1 A way of producing the plastic sheet with complex shaped pockets for weight insertion along its sides (Produced from a flattened tube). Figure 2 A second way of producing the plastic sheet with complex shaped pockets for weight insertion along its sides (Produced from a flattened tube). Figure 3 A third way of producing the plastic sheet with complex shaped pockets for weight insertion along its sides (Produced from a single sheet which has folded parts along its sides) Figure 4 Detail of the way of forming the complex shaped weight insertion pockets. Figure 5 Detail of a second way of forming the complex shaped pockets of the plastic sheet. Figure 6 Detail of a way of filling a series of water pockets (10). On the feeding tube(l 1) there are openings (14) - transverse or inclined - allowing the water pockets to be filled. Figure 7 Detail of a way of filling a series of water pockets ( 10) by having non- welded parts at the bottom of each soil pocket (15) trough which a feeding pipe is inserted (16) Figure 8 Detail of a way of filling a series of water pockets (10) having a self closing valve or a manually adjusted valve (17). Figure 9 The plastic sheet with complex shaped weight insertion pockets along its sides (2) applied on a cultivation under low tunnels (18). Figure 10 The plastic sheet with complex shaped weight insertion pockets along its sides (2) applied on a dyke (20) in the cultivation of asparagus. A way of producing the complex shaped weight insertion pocket sheet is described below:

The plastic sheet produced by the method of extrusion or coextrusion from a circular or flat mould and it has a width A up to 4m and preferably 1 to 2m and thickness up to 200μm.

The plastic sheet can have: a) The form of a flattened tube (1) (Figures 1 and 2) of layflat A and circumference 2A. b) The form of a single sheet (2) (Figures 3 to 10) which has folded parts along the two sides (3) of width up to 25cm and preferably 17cm

On the two sides along the full length of the sheet the two superimposed parts are welded (which exist either as folding or as flattened tube) by a combination of welds in such a manner that a complex shaped weight insertion pocket is formed. This pocket includes: a) A series of successive weight insertion pockets for use with soil b) A series of successive weight insertion pockets for use with water.

Such a combination of welding could originate from :

a) a linear, continuous welding parallel to the length of the plastic sheet and at a distance (bl) of up to 15cm -preferably 7cm from the edge (4). b) a linear, sectional welding (5) of length L3 , having a step of LI, parallel to the length of the plastic sheet and at a distance of (b2) up to 20cm -preferably 15cm from the edge (4). c) a repeated, formed welding (7) of step L2 and of any geometrical shape (e.g. part of a curve) which originates from the edge (4) and ends at a minimum distance of 3cm from the linear welding (6). d) a repeated transverse or inclined welding (8) with a step of LI which originates from the continuous welding (6) and preferably ends at the centre of every sectional welding (5).

In this way the volume created between a sectional welding (5) a linear welding (6) and two successive transverse or inclined welds (8) is the weight insertion pocket (9) for use with soil. Weight is inserted through the non-welded part between two parts (12a) of the sectional linear welding (5) and its length is d = L1-L3.

Each water pocket (10) is formed between the edge (4) and the formed welding

(7) of step L2. The distance between two successive formed welds (9) is the passage (13) through which water flows to each pocket through a parallel tubular pipeline of variable cross sectional area.

This pipeline is formed between the continuous welding (6) and the repeated formed welding (7) having a diameter of at least 2cm (in full circular section).

In this way two series of pockets are created. On the inner part (considering as reference the central axis along the plastic sheet) successive pockets of step LI (preferably more than lm) are formed and their aim is to facilitate soil (9). On the outer part (considering as reference the central axis along the plastic sheet) successive pockets of step L2 are formed and their aim is to facilitate water (10). The tubular pipeline (11) is located between the two series of pockets. To simplify the structure steps LI and L2 could be equal.

The complex pattern of the weight insertion pockets is preferably the same on both sides along the sheet. Another way of producing this sheet (Figure 5 - Detail) is by forming on the inner part of the single sheet or the flattened tube water pockets (10) and on the outer the soil pockets (considering as reference the central axis along the plastic sheet). In this case the formed welding (7) is between two linear (6a,6b), continuous and parallel welds. Hence: a) One continuous and linear welding (6a) could be at a distance (b2) up to 20cm preferably of 15cm from the edge (4). b) The second continuous and linear welding could be at a distance up to 15cm and preferably 8cm from the edge (4). c) Each repeated formed welding (7) should originate from the second continuous welding (6b) ending at a distance not smaller than 3 cm from the first continuous welding, and it should have a step of L2 d) The successive transverse welding should have a step of LI and originate from the edge (4) ending at the second continuous welding (6b).

It is clear that in the case of the soil pockets (9) (which are formed between the second continuous welding (6b), the edge (4) and two transverse welds (8)) an opening for weight insertion should be formed (12b). This opening is formed during the production of the sheet by slitting the sheet at a regular distance of L2 . The slits should be on the folding and should have length d - preferably they should be located at half length of each soil pocket, very close to the second linear welding (6b).

It is clear that each of the above ways of producing the invention could be formed by only one complex welding which would have a step of LI and it would include parts of a linear and parallel welding (6), the formed welding (7) and the transverse welding(8).

It is apparent that the present invention provides several possibilities of combined welding so as pockets of any shape and use could be formed along the plastic sheet. In this way the soil pockets and the water pockets could have any geometrical or natural shape (e.g inclined parallelepiped, oval, formed shape etc)

Some combinations are as follows: a) Soil / Soil pockets. A linear continuous welding is combined with a sectional welding, a repeated transverse welding of step LI and repeated slits of step LI of length (d). b) Water / Water pockets. This is the most complex case which would require two continuous welds parallel to the length of the sheet, and two series of formed welds. One of the formed welds would be located between the edge and one linear welding and the other between the linear welds.

It is clear that the applied length of these plastic sheet poses restrictions to feeding water to the whole length of the sheet (1 or 2).

It is common that the length of the cultivation line surpasses 300m whereas the tubular pipeline (l l),of 0.05 - 0.2mm thickness, would not withstand the water pressure required to fill 100m of the plastic sheet. For this reason water should be fed through special openings regularly arrayed for feeding water to the tubular pipeline. These openings could be: a) a transverse or inclined slit (14) along the tubular pipeline. A weld also exists in such a way that the weld prohibits any water leakage from the adjacent pocket while the slit provides the required opening for filling the next pocket (Figure 9). b) a small non- welded part in a soil pocket such as that it allows access to the tubular pipeline (Figure 7) c) a self-closing or manually adjusted valve which is placed at the bottom of the soil pocket, allowing access to the tubular pipeline (Figure 8).

For the protection of the soil pockets (9) from excessive rain water a small hole should exist just under the weight insertion opening (12a, 12b) in order to allow any trapped water to escape.

The plastic sheet with complex shaped pockets along its sides (1) is wind in rolls preferably up to 1000m during its production and it could be absolutely symmetrical considering the central axis as reference.

In the application of the plastic sheet on the field the farmer could use it in three ways: a) By filling the soil pockets (9). Each pocket is filled individually. The water pockets remain empty (10) b) By filling the water pockets (10). The plastic sheet having complex shaped weight insertion pockets along its sides (1 or 2) is filled with water from one of the two ends or from the feeding openings (14 or 15 or 16). The soil pockets (9) remain empty. c) By filling both the water and soil pockets. In this case a combination of a) and b) is adopted. This is recommended for areas where windy conditions prevail

For the end user the plastic sheet with complex shaped weight insertion pockets along its sides (1 or 2) is a confident step towards the assured use of water due to the fact that the alternative of using soil is at the disposal of the farmer

Claims

CLAIMS l)Plastic sheet with complex shaped pockets for weight insertion along its sides

(Figures 1,2,3) of width (A) up to 4m - preferably 1 to 2 m and of thickness up to

200 μm. It could be either in the form of a flattened tube (1) or in the form of a single sheet (2) having folded parts along its sides (3) of width (b3) up to 25cm - preferably

17cm. It is characterized by the fact that it has on both sides (3):

a) a parallel to its length series of successive pockets for inserting weight(9), soil in this case, of any shape and of step LI preferably less than lm, b) a parallel to its length series of successive pockets for inserting weight (10), water in this case, of any shape and of step L2 preferably less than lm, c) a feeding tube (11) for the water pockets parallel to its length,

all formed on the plastic sheet by complex welding of the two superimposed parts along the sides of the sheet.

2)Plastic sheet with complex shaped pockets for weight insertion along its sides (Figure

4) according to claim 1 characterized by the fact that the complex welding of the two superimposed parts on its sides is a combination of:

a) a continuous linear welding (6) parallel to its length at a distance (bl) up to 15cm and preferably 8cm from the edge (4), b) repeated sectional welding (5) of step LI parallel to its length at a distance (b2) up to 20cm and preferably 15 cm from the edge (4), c) a repeated formed welding (7) of step L2 and of any geometrical and natural shape which originates from the edge (4) and ends at a minimum distance of 3 cm from the continuous linear welding (6), d) a repeated transverse or inclined welding (8) of step LI which originates from the continuous linear welding and preferably ends at the mid-point of each non- continuous welding (5).

3)Plastic sheet with complex shaped pockets for weight insertion along its sides (Figure

5) according to claim 1 characterized by the fact that the complex welding of the two superimposed parts is a combination of :

a) a linear, continuous welding (6a), parallel to its length at a distance (b2) up to 20cm and preferably 15cm from the edge (4), b) a linear, continuous welding (6b) parallel to its length at a distance (bl) up to 15cm and preferably 8cm from the edge (4), c) a repeated formed welding (7) of step L2, of any geometrical or natural shape, which originate from the second continuous, linear welding (6b) and ends at a minimum distance of 3 cm from the first continuous linear welding (6a), d) a repeated transverse or inclined welding (8) of step LI which originate from the edge (4) and ends at the second linear, continuous welding (6b),

and it has successive slits (12 b) of step LI and of length d parallel to the plastic sheet and very close to the continuous, linear welding (6b) and preferably at the mid-point between two successive transverse or inclined welds (8). 4)Plastic sheet with complex shaped pockets for weight insertion along its sides (Figure 1) according to claim 1, characterized by the fact that the complex welding, of the two superimposed parts along its sides, is a combination of:

a) a continuous, linear welding (6a), parallel to its length at a distance (b2) up to 20cm and preferably 15cm from the edge (4), b) a linear continuous welding (6b) parallel to its length at a distance (bl) up to 15cm and preferably 8cm from the edge (4), c) a repeated formed welding (7) of step L2, of any geometrical or natural shape, which originate from the edge (4) and end at a minimum distance of 3cm from the first continuous linear welding (6a), d) a repeated transverse or inclined welding (8) each of which originates from the second continuous linear welding (6b) and ends to the first linear continuous welding (6a),

and it has successive slits (12 b) of step LI and of length d parallel to the plastic sheet and very close to continuous linear welding (6b) and preferably at the mid-point between two transverse or inclined welds (8).

5)Plastic sheet with complex shaped pockets for weight insertion along its sides according to claims 1 to 4, characterized by the fact that step LI is equal to step L2.

6)Plastic sheet with complex shaped pockets for weight insertion along its sides according to claim 1, characterized by the fact that the complex welding of the two superimposed parts on its side, is formed from a successive welding by a complex shaped welding mould. Its welding forms one or more soil pockets (9) of any shape, one or more water pockets (10) of any shape and a part of the feeding tube (11).

7)Plastic sheet with complex shaped pockets for weight insertion along its sides according to claims 1 to 6, which is characterized by the fact that the opening of the feeding tube is formed at regular distances up to 100m, in several ways such as: a) by having slits (14) which are vertical or inclined on the feeding tube (Figure 6) b) by letting the soil pocket communicate with the feeding tube through a non- welded ρart(15) (Figure 7) c) by inserting a self closing or manually adjusted valve in a soil pocket in such a way that it communicates with the feeding tube (Figure 8). or by having any combination of openings.