Furthermore, the invention relates to a waterproof coating thus obtained.

In particular, the invention relates to a system for shielding surfaces of buildings from electromagnetic radiation by means of said waterproof coating, such as for example those generated by radio, TV, radar or cellular telephonic antennas, high voltage lines, etc.

Even if not exclusively, the invention relates to a waterproof coating for waterproofing substantially horizontal surfaces, or sub-horizontal surfaces of buildings such as foundations, roofs, terraces, etc. and shielding them from electromagnetic waves.

Always in particular, but not exclusively, the invention relates to a system for shielding by means of said coating metallic structures, ducts, etc. from stray currents, which cause serious damages for corrosion.

Furthermore, always not exclusively, the invention relates to a system for providing magnetic guides by means of said coating, in the industrial and road fields.

Background of the invention The problem is felt of shielding houses and offices from electromagnetic waves, whose negative effects on health and on well-being, notwithstanding not yet completely understood, are feared by people.

In particular, houses and offices are the places where people spend most of time, and then where the exposition is the largest.

New buildings have always thin walls, even if rugged enough, and are substantially permeable to electromagnetic waves.

In particular, roofs of buildings often support repeaters or other antennas that emit electromagnetic waves, whereby inhabitants are more exposed to this type of radiation. Near buildings there are sometimes high voltage lines, that create intense and variable electric and magnetic fields.

Another problem is that of the stray currents, which cause corrosion and then breakage of metal structures, ducts, etc. Such currents are produced by devices linked to the structure or they circulate in the ground surrounding the structure owing to adjacent electric plants. Corrosion of the metal appears in the points where the currents are transferred.

Concentrated corrosion can cause damages and perforation or initiation of fracture in tubes. Steel structures surrounded by ground are subject to this phenomenon as well, that causes damages thus requiring expensive maintenance and prevention systems.

A further problem is to provide magnetic guides on roads or on industrial paths. Usually, they are formed by electric cables laid underground or under road surfaces, for example under the centre or the side lines of roads.

Such magnetic guides have the function of guiding a vehicle without driver, for example inside industrial plants, or alerting a driver of a car that is suitably equipped with appropriate electronic apparatus of the passage beyond the centre line or the side line of a road or of the presence of a bend. However, the roadwork for laying underground cables are expensive, they weaken the road surface and obstruct traffic.

The bituminous membranes are bituminous substrates customarily used for waterproofing and insulating surfaces. They are normally made in the form of sheets or

rolls. The membranes are heated by fire at the moment of their application, and the coating obtained lasts a long time. Their composition can be varied according to their application, depending if, for example, they are used to cover roofs of buildings, walkways or roadways, structures to be waterproofed. Other bituminous substrates are obtained by lining directly surfaces with layers in turn of bitumen and of stiffening material. The latter membranes are made directly on place.

More generally, bituminous substrates are known as "geo-membranes", among which there are also, always for waterproofing purposes, polymeric elastomeric and plastomeric membranes, polyolefin based membranes, geo- synthetic membranes.

The waterproof bituminous membranes are normally made with addition of reinforcement material, for example glass fibre or polyester fibre, embedded between two layers of waterproof material made of elastomeric or plastomeric mix having bituminous or equivalent nature.

The membrane has a lower face, i. e. that in use is arranged below, suitable for sticking to the surface to be waterproofed after flame heating on place. More precisely, the laying of the waterproof membrane is carried out starting from rolls of membrane unwound after flame heating of the lower face, with propane heating torch, operating substantially on a generatrix of the roll being unwound. The heating step is carried out at a temperature of about 300°C and has the object of melting the bituminous lower face so that the mix after cooling forms a continuous bonding with the surface same.

It is known moreover that bituminous membranes are permeable to magnetic fields and are good electric insulators.

Summary of the invention It is therefore object of the present invention to provide a method for making a waterproof coating that,

besides having waterproofing properties and good mechanical resistance against external agents, has a magnetic effect, capable of solving the above problems and other problems of electrical, electromagnetic, magnetic type.

It is a first particular object of the present invention to provide a method for making a waterproof coating that is capable of shielding surfaces of buildings from electromagnetic radiation and that can be easily applicable both to new and existing buildings.

It is another object of the present invention to provide a waterproof coating applicable to surfaces of buildings for shielding the internal room from electromagnetic radiation without additional expensive works with respect to the known waterproofing techniques.

It is a first particular object of the present invention to provide a method for making a waterproof coating for shielding metallic structures, ducts, etc. from stray currents, which is easy to carry out and provides a permanent protection, as well as to provide a waterproof coating applicable to such metallic structures that carries out this method.

It is a further object of the present invention to provide a method for making a waterproof coating that is used as magnetic guide, in industrial and road surfaces.

These and other objects are achieved by the method according to the invention whose characteristic is to provide a waterproof coating in the form of bituminous membranes or other equivalent material having for its all extension at least an embedded layer of conductor material.

The production steps of the membranes comprise: -unwinding at least a roll of a web reinforcing material; -rolling said layer of reinforcing material through a storage stand of bituminous material or other

equivalent resin material, whereby on both the faces of said reinforcing material are thus deposited layers of bituminous material or the like, its characteristic being that the reinforcing material is a conductor material.

In particular, said reinforcing material is a conductor web such as a net obtained from knitting or weaving lead wire, or it is a thin perforated and stretched metal sheet, or it is a non woven fabric.

According to a general aspect of the invention, a waterproof membrane, such as in particular a bituminous membrane, made directly on place, or prefabricated flat or wound in a roll, for waterproofing and insulating horizontal surfaces of buildings, or for shielding structures from stray currents, or for making magnetic guides or for other uses with electrical and/or magnetic effect, is formed by a first face that sticks to the surface to coat and a second face facing towards the exterior, the membrane having the characteristic of being associated to at least a layer of conductor material that extends for all its surface.

The layer of conductor material is embedded in the matrix of the coating, advantageously about at the middle of its thickness.

The layer of conductor material embedded in the waterproof coating is preferably a metal web. The web can be made of knitted or woven metal lead wire or of thin perforated and stretched metal sheet, or of non woven metal fabric made of conductor fibres. For the metal web fibres can be used plated with highly conductor metals, for example inoxidizable precious metals.

The wire of the web may also be either made of or plated with metals chosen among: copper, aluminium, brass, iron, nickel, steel, carbon, titanium, other metals or conductor metal alloys, such as ferromagnetic alloys with high rate of nickel also called"mu-metal"..

The maximum distance between two conductor wires of the web is set between 50 and 3mm. The web can be formed by either all conductor wires or by conductor wires alternated to one or several not conductor wires.

In a first embodiment of the invention, all the web is embedded in the membrane. Longitudinally to the membrane and at or near the edges thereof the web is covered along both sides by a web in flexible material so that the web is insulated from the bituminous material.

Furthermore, the membrane has advantageously transversal strips of flexible material, for example fabric impermeable to bitumen, which coats the web along transversal lines. By pulling with suitable shear movement the transversal and/or longitudinal flexible material it is possible, in use, to uncover strips of web at or near the longitudinal sides of the membranes and/or transversal strips of net, thus tearing the bituminous material that coats it and allowing an electrical connection with the adjacent partially overlapping membranes or with a grounding.

In a second embodiment, not all the web is embedded in the membrane, and precisely a central portion of web is embedded in the membrane whereas a first and a second lateral edge of web protrudes from opposite sides not embedded in the membrane. Also a head or tail edge of the membranes can be uncovered.

The web edges not embedded in the membrane are electrically not insulated. When preparing the membrane before or after the laying step, the first edge of web is bent on the first face and the second edge on the second face. This way, laying a roll of membrane partially overlapping another membrane already stuck, it is possible to match the two web edges on one another, thus electrically connecting the webs or nets of the two membranes.

In both embodiments, by laying on a same surface

different coating membranes adjacent to one another and partially overlapping, a single membrane and a single web electrically connected is substantially obtained.

According to a first particular aspect of the invention, for shielding buildings from electromagnetic waves the application to the surfaces of said buildings is provided of coating elements formed by said bituminous membranes. The conductor material embedded in the coating or membrane is grounded for completing the shielding.

Furthermore, the conductor materials belonging to different coating elements are electrically connected to one another in order to form a single conductor to be grounded.

Another physical particular aspect of the invention is shielding metallic structures from stray currents, by applying to the surfaces of said structures waterproof coating elements formed by said bituminous membranes. The conductor material embedded in the coating or membrane is grounded for completing the shielding. Furthermore, the conductor materials belonging to different coating elements are electrically connected to one another in order to form a single conductor to be grounded. If the surfaces to coat are tubular surfaces, for example for shielding ducts from stray currents, the bituminous membrane according to the invention has two uncovered web edges at opposite sides. The membrane, made of a strip of appropriate width, is wound helically, so that the two uncovered web edges match with each other.

The laying step on plane surfaces can be carried out in a normal way for bituminous membranes, by flame heating the face that sticks to the surface to shield. The longitudinal or transversal edges of the membranes are overlapping each other so that uncovered web edges of adjacent membranes selectively match with one another forming an electrical contact.

Advantageously, the uncovered web edges can be coated with conductor paste, for example based on powder of

graphite, copper, silver, aluminium embedded in a suitable pasty matrix that with heat produces a conductor linkage for the matching web edges, in order to assure a contact even where gaps are present.

In a different embodiment of the method of coupling the membranes, after the laying step of a first membrane that has a first edge of web uncovered, a second membrane is completely overlapped that has also an edge of web uncovered, so that the two edges match with each other.

Then, the first and second membrane are linked to each other by a side seam applied on place that crosses the two edges. Finally, the second membrane is overturned about the seam with respect to the first membrane already stuck to the surface.

The membrane can be supplied in rolls unwound progressively and flame applied on the surfaces to be shielded. After cooling the first edge of web of a first membrane matches the second edge of web of a second membrane and the electrical contact is obtained. The addition of said conductor paste completes, when necessary, the contact between the uncovered portions of web. The overlapping step of the membranes is carried out similarly to the prior art membrane without conductor web.

Then, the heating of the bonding line between the two membranes is carried out by means of penetration of the molten bitumen also through the two overlapped web edges.

This penetration does not affect the electrical contact that is already obtained between the two membranes.

In particular cases, the bituminous membrane can also be mounted on vertical surfaces.

According to a third physical aspect of the invention, magnetic guides can be made by means of direct application on a road surface of a waterproof coating with magnetic effect. The coating, in the form of a membrane, is provided in rolls of a not too much wide strip and having an embedded conductor material, in particular metal fabric

net. The ends of the strip have uncovered web edges that overlap each other thus giving continuity to the conductor web, for example with the aid of bonding by heating or with chemical pastes. Voltage is applied to portions of predetermined length of strip that form a current path and then a magnetic guide. The method of use of the coating according to the invention is particularly effective since the laying step of the web can be done very quickly and also with an appropriate equipment, thus rapidly providing magnetic guides for long distances. The strength of the reinforced bitumen is like that known and used in bituminous membranes for road works and allows to the magnetic guide to bear even high compressive and shear stress.

Brief description of the drawings Further characteristics and the advantages of the method for making a waterproof coating with electrical and/or magnetic effect, of the waterproof coating thus obtained and of its use according to the invention will be made clearer with the following description of an embodiment thereof, exemplifying but not limitative, with reference to the attached drawings, wherein: -figure 1 shows a diagrammatical simplified view of the production of a bituminous membrane according to the present invention; -figure 2 shows a top plan view of a web made of fabric formed with lead wire and used for the production of the bituminous membrane of figure 1 ; -figure 3 shows a cross sectional view of a membrane obtained with the process of figure 1 ; -figure 4 shows a cross sectional view of a different embodiment of a bituminous membrane obtained with the process of figure 1 suitably modified; -figure 5 shows a step of tearing away a side portion from the bituminous membrane of figure 4 to uncover edges of conductor metal net; -figures 6A and 6B show a perspective view of an

unwinding step of a bituminous membrane with the uncovering steps of longitudinal and transversal strips of conductor net; -figure 7A and 7B show a step of mechanical and electrical coupling of two bituminous membranes according to Figures 6A and 6B with the electrical coupling to each other and relative grounding; -figures 8 and 9 show a perspective view of a different embodiment of a bituminous membrane according to the invention; -figures 10 and 11 show the bituminous membrane of figures 8 and 9 with the side edges of conductor web bent laterally towards opposite sides; -figure 12 shows a step of coupling two bituminous membranes like those of figures from 8 to 11 ; -figures from 13 to 15 show a third different embodiment of the step of mechanical and electrical coupling of two bituminous adjacent membranes, with the overlapping, seaming and overturning steps of the upper membrane with respect to the lower; -figure 16 shows a step of coating a roof of a building with a membrane according to the invention; -figure 17 shows a step of coating a metal tube with a bituminous membrane according to the invention; -figure 18 shows the method of making a magnetic guide by means of a membrane according to the invention.

Description of a preferred embodiment With reference to figure 1, a waterproof coating 1, in the form of a bituminous membrane, is produced in a plant 2 of known type.

More precisely, the production steps of membrane 1 provide the unwinding of at least a roll 5 of two- dimensional material 3 that is rolled through stands 4 and sunk in bituminous material. This way, on both faces of the two-dimensional material 3 layers of bituminous material are thus deposited. Membrane 1 is then wound forming a roll

Normally, the two-dimensional material 3 has the function of a reinforcing material for membrane 1, and is completely embedded in the bituminous matrix.

According to the invention, the two-dimensional material 3 is a conductor material. It can be made of a net or web 13 obtained by knitting or weaving, like that shown in figure 2, with wires of weft 14 and warp 15. Wires 14 and 15 can be wires of conductor metal chosen among: copper, aluminium, brass, iron, nickel, steel, carbon, titanium, other metals or conductor metal alloys, such as "mu-metal". The latter is a ferromagnetic alloy having the following general composition: Ni 70-80% ; Cu 0-5% ; Fe 14- 15% ; Mo 4-5k and other elements such as Chromium and Cobalt. Alternatively can be used textile thread, plastic or metal wire with not high conductivity (for example steel) plated exteriorly with highly conductor metals, for example copper or inoxidizable precious metals, or the above"mu-metal"same.

The web, before being embedded in the membrane according to the invention, is degreased in hot water or vapour for cleaning it from any insulating oily film.

The thickness of the wire, according to different uses, can be varied from 30 to 2mm. The maximum distance 6 between conductor wires of a mesh of the web is preferably set between 50p and 3mm. It is possible also to alternate conductor wires of weft 14 or of warp 15 to not conductor wires.

Alternatively to the web of metal woven wire, the two-dimensional material 3 can be made of knitted net, always in lead wire, or of thin perforated and stretched sheet, or by non woven fabric made of conductor fibres "agugliate"or carded.

A result of the production of a waterproof membrane, in particular a bituminous membrane according to the invention is shown in the cross sectional view of figure 3,

wherein with the numeral 11 the bituminous matrix has been indicated in which web 13 with wires of weft 14 and wires of warp 15 is embedded. Web 13 is embedded in matrix 11 of membrane 1 about at the middle of its thickness.

Membrane 1 thus obtained, besides having waterproof properties completely equal to the normal bituminous membranes, is also reinforced by the mechanical resistance of the conductor material 3, in particular web 13, and owing to the conductive properties of web 13 same it has also electromagnetic, magnetic and electric properties, that the normal waterproof bituminous membranes do not have.

The use of membrane 1 according to the invention can be done in many ways described hereinafter, exploiting the characteristics of electromagnetic induction of the conductor metal of the net, both in passive way, such as for shielding electromagnetic waves or neutralising stray currents, and in an active way, such as to provide magnetic guides.

With reference to figures from 4 to 7, in a first embodiment of the invention all web 13 is embedded in matrix 11 of membrane 1. In order to carry out the electric connection, such as grounding, electrical connection to adjacent membranes, or the connection to voltage sources, it is necessary to uncover portions of web so that they are not electrically insulated.

As shown in figure 4, at the edges of membrane 1 web 13 is covered at both sides by a strip 20 in flexible material, which insulates them enough from the bituminous material 11. Strip 20 can be for example waterproof fabric, for example cloth. Or can be a extruded resin, or also an insulated linen finished strip. Strip 20, having enough mechanical resistance, can be torn away on place by the operator so that side edges 13a and 13b of web 13 are uncovered, thus removing corresponding portions of bituminous matrix lla and llb.

With reference again to figure 1, strip 20 may be fed

from a reel 20a and rolled through the stand along with web 3. Alternatively, strip 20 may be fixed to the web of reel 5 in a previous step.

Also transversally, in the direction of the weft of web 13, transversal strips of fabric 21 can be provided which, when torn away, remove portions lie of bituminous matrix, thus uncovering a portion of web 13c (figures 6A, 7A). The portions of uncovered web 13c, at a single or even at both the ends of membrane 1, allow the operator to cut the membrane and join it for creating an electrical connection with a previous or following membrane.

Both for the longitudinal uncovered portions of web 13a and 13b, and for the transversal portions of uncovered web 13c of figure 6A, it is possible to form a bonding line as shown in figure 7A. More precisely, it is sufficient to couple the membrane by matching an uncovered edge of web 13a at a side of membrane la, with an edge of uncovered web 13b at the opposite side of membrane lb. The corresponding removed portions of bituminous matrix lla and llb (figure 5) allow that the overall thickness along the longitudinal bonding line is not increased. A similar step can be done for the head or tail junctions, provided that transversal web edges 13c are uncovered by removing portions llc at the opposite longitudinal ends of membrane la and lb.

Alternatively, as shown in figures 6B and 7B, the longitudinal strips are located at several centimetres from the edge. This way, the overlapping portion is enough to assure a correct waterproof, for example about 10cm.

Preferably, on uncovered web edges 13a, 13b or 13c a conductor substance is applied, such as a mixture or gel for example based on powder of graphite, copper, silver, aluminium embedded in a suitable pasty or gelatinous matrix. The conductor paste may be for example an epossidic resin with graphite > 50.

This way, by flame heating membrane 1 according to arrows 18 of figure 6 during the application step to

surface 19 to coat, the conductor substance forms after heating a conductor link at the matching web edges 13a, 13b or 13c, so that a contact is assured even where physical gaps are present. Obviously, a correct pressing step of membrane la and lb on surface 19 improves contact between metal and metal of the two uncovered web edges or portions and, with the aid of the conductor substance, a steady contact for all the length of web edges 13a, 13b or 13c is obtained. A successive penetration of the bituminous material does not affect the continuous electric contact between web edges 13a, 13b or 13c. Along with, or instead of, the conductor paste, also a lead element may be inserted between the two uncovered web edges or portions, for example a metal cable, that has a thickness enough to fill the gap between them.

With reference to figures from 8 to 12, in a different embodiment of the invention web 13, instead of being all embedded in bituminous matrix 11, has edges 13a and 13b already free from bitumen at the end of the production step of figure 1. This can be obtained by masking the web during the sinking step in the bitumen within stands 2, or by the application of templates then removed before or after winding in roll, as well as by hot washing and degreasing the web edges. In every case, it is important that the uncovered web edges 13a, 13b are eventually electrically not insulated. Also a transversal portion of head and/or tail edge of membrane 1 can be uncovered.

The roll 7 of membrane can be formed directly as shown in figures 10 and 11, with a first edge of web 13a bent onto the first face and a second edge 13b bent onto the second face membrane 1. This way, as shown in figure 12, laying a membrane la partially overlapping to another membrane lb already stuck, it is possible to match the two edges of conductor web 13a and 13b on one another, thus electrically connecting the nets 13 of the two membranes la

and lb. In figure 12, as also in some of previous figures, membrane la and lb are shown with the omission of a central part, for graphic reasons. Furthermore, the thickness of membranes has been increased with respect to the actual one. Normally a bituminous membrane has a thickness set between 2 mm to 1 cm.

With reference to figures from 13 to 15, a different embodiment of the method of coupling the membranes provides that, after the laying step of a first membrane la, with a first uncovered web edge 13a, a second membrane lb is completely overlapped having also a second uncovered web edge 13b, so that the two edges 13a and 13b are parallel to each other (figure 13). Then, the first and second membrane are jointed with a lateral seaming or welding 22, carried out on place, that crosses the two edges 13a and 13b (figure 14). Finally, second membrane lb is overturned about line 22 about the already stuck first membrane la, as shown in figure 15.

In all the examples of figures 7,12 and 15, laying a plurality of membranes 1 on a same surface to coat a substantially single membrane and then a single electrically connected web are eventually obtained.

With reference to figure 16, for shielding the roof 31 of a building 30 from electromagnetic waves it is possible the application in the way above described of a plurality of membranes 1 all electrically connected at the side and end edges, so that a single membrane 100 is formed. The conductor material of nets 13 associated to membranes 1 that is located along the perimeter of membrane 100 is grounded, for example to a gutter 32, for completing the shielding. Through the electrical connections between adjacent membranes like that shown in figures 7,12 and 15, also the web 13 belonging to different adjacent membranes 1 is linked electrically in order to form a single conductor in turn grounded.

To shield high frequency electromagnetic waves, for

example about 800MHz-2GHz like those of cellular telephones, it is preferential that web 13 has a diameter 6 (fig. 2) of about 150-600. This can be obtained using a woven web of conductor wire with the diameter of 100-300.

For shielding from lower frequency fields it is possible to use a woven net or web having meshes with wider width. For these frequencies it is advantageous to use web made of Mu-metal or net made of wire plated with Mu-Metal.

The application of prefabricated membranes can be substituted by making the membranes on place, by applying bituminous layers directly with the interposition of web 13, suitably linked to adjacent nets and grounded.

According to another particular aspect of the invention, shown in figure 17, a duct in steel 40 can be shielded from stray currents. More precisely, a bituminous membrane 1 large for example 10-30 cm can be applied helically, with side edges 13a and 13b uncovered in the same way shown in figures from 4 to 7. A single membrane tubular 41 is thus formed and, internally to it, a single metal tubular web completely insulated from tube 40 is provided. Advantageously, tube 40 can be rotated while progressively unwinding membrane 1.

The metal tubular web within membrane 41 is then grounded for completing the shielding without touching in any place the metal of tube 40 same. The variations of current in tube 40 by magnetic induction are picked up by the tubular web conductor of web 13 and, in the form of current they are discharged far from tube 40 same.

With reference to a third aspect of the invention, shown diagrammatically in figure 18, it is possible to provide a magnetic guide 50 for driving a self-propelled vehicle along a direction 51 on a surface of movement 52.

More precisely, this can be achieved by applying directly to surface 52, for example a road surface or a path in an industrial plant, a strip of membrane 1 like that shown in figure 3. Membrane 1 is provided in rolls of web for

example of 5-10 cm wide and having a conductor web 13 embedded.

One of the ends of the magnetic guide 50, i. e. the head or tail edges of the web, is connected to a voltage supply 53 for generating driving currents that generate magnetic field lines that allow to determine direction 51.

For obtaining appropriate length a plurality of portions of web can be connected in succession in the way shown for example in figure 7. Strip 50 can be applied easily to surface 52, such as a normal bituminous membrane.

The foregoing description of a specific embodiment will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.