Description

Our invention refers to a thermally welded plastic sheet destined for covering cultivations of vegetable or animal productions. These constructions consist of the framework and covering material, which in this particular category are sheets of plastic. These plastic sheets are fixed on the framework by: a) special clips ( there are several inventions ) b) wires c) the weight of the ground after the edges of the sheets have been covered in ditches d) several systems that combine two or more of the above cases

In cases a, c, d and for parts of the constructions of case b a large amount of capital is necessary in order to construct the framework and to buy the clips that hold the plastic. Furthermore, a satisfying solution regarding the lengthening of the plastic sheets caused by expansions in temperature differences cannot be found. Regarding the remaining simplistic and cheap constructions of case b it is difficult to create water drains that remove the rain water. In addition there is no moisture proofing for the protected area.

The goal of our invention is to create a product with such a low investment cost that makes it worth covering products of very low value. According to our invention the above can be realized by the creation of cylindrical water storage tubes of the same plastic material that are thermally welded on the plastic sheets that cover the cultivations.

These tubes are thermally welded near the folded edges of the plastic sheets that in turn are placed on the framework of the construction, with the water storage tubes on both sides of the ridge. The weight of the water always keeps the plastic sheets stretched, in spite of wind and temperature changes, while the portion of the plastic sheets that has been left in excess, after their folding on both sides, is used to connect one sheet to the next. In the middle of the plastic sheet an extra sheet is thermally welded underneath in order to

protect the main sheet from damages caused by the contact with the ridge. The connection points between the plastic sheets serve as water drains.

Our invention renders indispensable expensive greenhouse frameworks, metal water drains and all types of clips that hold the sheets on the roof. Its advantages are:

1) The very low investment cost per square meter of covered surface

2) That different materials for covering an area are not necessary, since the plastic sheets can be used in many different ways:

A) As covering material B) As pipes-reservoirs that store water

C) As connection means (unnecessary use of clips)

3) The weight of the water always keeps the plastic sheets stretched, in spite of any expansions

4) The water works as a means of storing energy, by collecting the heat of the sun and maintaining the temperatures during the night.

The production of our invention is described below, with references made to the attached figures:

Step 1 : Fold the left and right sides of a plastic sheet (1) that has the appropriate dimensions. ( fig. 1 ) Step 2: Thermally weld the water storage tubes (2) on the folded edges of the plastic sheet, leaving on both sides a portion of the plastic sheet in excess (3)(fig. 2)

Step 3: Cut into strips the portion of the plastic sheet that is left in excess (4) and form webbings (5) in order to avoid further tearing, (fig. 2 and 3) Step 4: In the middle and underneath the main plastic sheet thermally weld an extra sheet (6) with the edges also formed by strips (7) and webbings (8). ( fig. 4)

Another way of producing could be the following:

Step 1 : Fold the left and right side of the plastic sheet (1) with the appropriate dimensions leaving a larger part of the sheet in excess in comparison to the first way of production described above. Form the storage tubes (2) by thermally welding the excess sheets(9) ( fig. 5 )

Step 2: Cut into strips of 50 centimetres the portion of the plastic sheet that is left in excess after the tubes are formed (4) and make

webbings at their ends (5) in order to avoid any further tearing, (fig. 5) Step 3: Thermally weld in the middle of the main sheet an extra plastic sheet (6) that is also cut into strips (7) and has webbings (8) (fig. 6) Below find an application of our invention. Covering two successive cultivation areas:

Step 1 : Fix three lines of stakes on the ground, (fig. 7)

Step 2: Form ridge by placing steel wires on the stakes, (fig. 8)

Step 3: Place the thermally welded plastic sheet on the steel wires in the middle of the sheet where the extra sheet has been additionally welded. Tie the strips of the extra plastic sheet to the ridge. ( fig. 9)

Step 4: Tie together the plastic strips on each side of the consecutive sheets, (fig. 9). The cavity that is made at each connection point is used as a water drain. (10) Step 5: Fill the tubes with water. With the above a roof of a green house construction is made.

In figures 10 -14 variations of the construction are shown, in which the number of water storage tubes differ.

The number of the water storage tubes depends on the width of the basic construction unit. The more water storage tubes the better the weight of the water can confront the sub-pressure that is created by the highest winds in the area of the installation.

Figure 10: Plastic sheet with 1 tube on one side Figure 11 : Plastic sheet with 2 tubes on one side Figure 12: Plastic sheet with 3 tubes on one side Figure 13: Plastic sheet with 2 tubes on both sides Figure 14: Plastic sheet with 3 tubes on both sides