CH719602A1 - Device for heating bituminous soil. - Google Patents

Abstract

The present invention relates to a device for thawing a roadway and the use of a flexible, substantially planar electrothermal structure (100) for heating a bituminous ground, the structure (100) having a front face intended to allow rays to pass through. infrared. The structure (100) comprises at least one electrical input terminal (131), at least one electrical output terminal (132), a substrate for receiving a plurality of layers of the structure, the substrate comprising at least one polymeric layer of substrate, at least one electrothermal layer comprising a resistive element (149) having an input and an output, the resistive element (149) having a substantially rectangular shape with a width substantially equal to the width of the structure (100). The structure (100) also comprises at least one conductive layer for connecting the input terminal (131) of the structure to the input of the resistive element, and the output terminal (132) of the structure to the output of the resistive element, the structure (100) is covered with a passivation comprising at least one polymeric passivation layer.

Description

TECHNICAL AREA

[0001] The present invention relates to techniques for clearing snow-covered roads or de-icing frozen roads. More particularly, the invention relates to a device and a method for de-icing frozen roads.

STATE OF THE TECHNIQUE

[0002] It is known to spread salt and other deicing products on frozen roads to thaw them. However, these products are often harmful to the environment. Snow plows are also known to clear roads that have become snow-covered, but before the deployment of these machines, the roads can remain impassable for a significant period of time.

SUMMARY OF THE INVENTION

[0003] An aim of the present invention is to propose a method and a device for thawing frozen or snowy roads which is effective and less harmful to the environment. Another aim of the present invention is to preserve the physical integrity of the coating and thus preserve it over time.

[0004] According to a first aspect, a process for drying plants is presented. The method includes arranging the plants on a heating sheet adapted to emit infrared rays. Preferably, the infrared rays are long infrared rays, having wavelengths of between 25um and 350um.

[0005] According to another aspect, the use of a multilayer, flexible, substantially planar electrothermal structure is proposed for drying plants.

[0006] The electrothermal structure proposed in the invention has a front face intended to allow infrared rays to pass through and a rear face opposite the front face, the structure having a width and a length, i.e. a surface, the structure comprising: minus one electrical input terminal; at least one electrical output terminal; a substrate for receiving a plurality of layers of the structure, the substrate comprising at least one polymeric substrate layer; at least one electrothermal layer comprising a resistive element having an input and an output, the resistive element having a substantially rectangular shape with a width substantially equal to the width of the structure; and at least one conductive layer for connecting: the input terminal of the structure to the input of the resistive element; and the output terminal of the structure at the output of the resistive element; the structure being covered with a passivation comprising at least one polymeric passivation layer; the resistive element comprising graphene.

SUMMARY DESCRIPTION OF THE DRAWINGS

[0007] The characteristics of the invention will appear more clearly on reading the description of several embodiments given solely by way of example, in no way limiting with reference to the schematic figures, in which: – Figure 1 shows the different layers present in an electrothermal structure according to an embodiment described in this document; – Figure 2 illustrates an equivalent electrical diagram representing an electrothermal layer which can be deployed in one embodiment of the electrothermal structure; – Figure 3 shows the layers present in an electrothermal structure according to another embodiment; and – Figure 4 shows the layers present in an electrothermal structure according to yet another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the heating of bituminous soils to prevent the formation of frost. A device is proposed in the form of a flexible multilayer electrothermal structure which is laid under the bitumen.

[0009] According to one embodiment, the multilayer electrothermal structure is a flexible sheet, which includes a Joule effect heating element. The heating element includes an electrothermal material, which heats when it conducts an electric current. According to one embodiment, the electrothermal material has a positive temperature coefficient (PTC). According to one embodiment, the material has an emissivity such that when heated, it begins to emit infrared radiation, preferably far infrared. Thus, the electrothermal structure of the present invention heats by the effect of infrared radiation rather than by convection. The choice of far infrared radiation is made to promote the sensation of heat felt by a human being, because the human body favors the absorption of radiation in this spectrum. By far infrared, we understand infrared rays having wavelengths between 25um and 350um

Preferably, the electrothermal structure of the present invention is substantially planar, extending in two dimensions. The structure is preferably elongated, having a length several times greater than its width. According to one embodiment, the electrothermal structure has a certain flexibility such that it is sufficiently flexible to be rolled up on itself. The structures of the present invention are therefore easy to handle and transport.

[0011] The materials chosen for the encapsulation of the structure, namely the substrate and the passivation, are chosen to allow infrared rays to pass through. Preferably, at least one of the two surfaces allows infrared rays to pass through. In one embodiment, a reflective layer is used to promote the passage of infrared rays through a single side of the structure, i.e. the side called the front side, rather than through the rear side. In other embodiments, the infrared rays can pass through the front face and the rear face of the structure.

[0012] FIG. 1 shows the layers which may be present in an electrothermal structure 100 according to one embodiment of the invention. The structure is built on a base, namely the substrate 110. According to one embodiment, the substrate is made of a layer of flexible polymer material, for example polyethylene terephthalate (PET). A conductive layer 130 comes next. According to one embodiment of the invention, the conductive layer is a conductive ink, deposited by a “slot dies” process then dried by infrared radiation, which promotes rapid drying. Optionally, to facilitate adhesion of the ink to the polymeric layer of the substrate, the substrate undergoes plasma treatment. In another embodiment, a primer layer can be applied to the substrate instead of using plasma treatment to ensure adhesion of the conductive layer to the substrate.

[0013] On the conductive layer is drawn, in conductive ink, a certain number of current conductors to bring a current which arrives at a pair of terminals 131 132, input/output, preferably located towards one edge of the structure, at least towards the heating element of the structure. FIG. 2 shows an electrical diagram which represents the heating element 149 of the structure 100, with its input 131 and output 132 terminals. The heating element is represented by a resistor 149.

[0014] According to the embodiment described above, the heating element is located in the electrothermal layer, which is denoted 140 in FIG. 1. The heating element can have any shape as long as it has sufficient resistance to produce the desired Joule effect. Thanks to the emissivity properties of the electrothermal material chosen as the heating element, its dimensions will dictate the temperature, depending on the current, and the quantity of infrared radiation produced. The electrothermal material of the heating element can be deposited by a screen printing process, like the conductive layer, preferably by a slot die process. Contacts between the electrothermal material of the electrothermal layer and the conductive material of the conductive layer are made at the places where the two materials touch, thus creating the resistance, shown schematically in FIG. 2. The resistance at an input and an output. In one embodiment, the input of the resistor is connected to the input terminal of the structure and the output of the resistor is connected to the output terminal of the structure.

[0015] As indicated in FIG. 1, the last layer is a passivation layer 120. The passivation layer can be made of the same material as the substrate layer, i.e. a flexible polymer, preferably allowing infrared rays to pass through. According to one embodiment, the passivation layer is made of polyethylene terephthalate (PET). According to one embodiment, a layer of glue is used to fix the passivation layer on the electrothermal layer. Thus a structure called a “sarcophagus” ensures airtightness and watertightness to protect the heating element and the electrical conductors.

[0016] According to one embodiment, the glue is a heat-treated polyurethane glue. Polyurethane glue can be deposited in the liquid phase. According to another embodiment, the glue is solid, for example a “PSA” glue (pressure sensitive adhesive), the adhesion functioning by applying mechanical pressure.

[0017] FIG. 1 shows the order of layers starting from bottom to top with the substrate layer 110, the conductive layer 130, the electrothermal layer 140 and the passivation layer 120. In other embodiments, it is possible to change the order, for example: substrate 110, electrothermal 140, conductive 130, passivation 120; or passivation 120, conductive 130, electrothermal 140, substrate 110; or even passivation 120, electrothermal 140, conductive 130, substrate 110.

[0018] According to one embodiment, the radiation passes through one face of the structure, either through passivation or through the substrate. In this embodiment, the structure includes a reflective layer to reflect far infrared rays towards one of the two surfaces, i.e. the front face. The other side is the back side. The reflective layer is made of aluminum according to a preferred embodiment and is placed towards the rear face.

[0019] According to a preferred embodiment, the substrate comprises two polymeric layers of substrate, glued together. The passivation can also include two polymeric passivation layers glued together. Thus, the structure provides good electrical insulation as well as mechanical protection against scratches or other surface damage. Having two layers glued together provides better mechanical protection than a single layer having double the thickness, because the glue layer provides a barrier to stop the propagation of a possible cut or tear in a polymeric layer. FIG. 3 and FIG. 4 show examples of structures having double polymeric layers of substrate and passivation.

The polymeric layers (substrate or passivation) can be made of PET according to a preferred embodiment but can also be made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), flexible PVC ( PVC-P), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), polyoxymethylene (POM), polyethylene terephthalate (PET), polyester, co-polyester, polyetheretherketone (PEEK), polyamide, in particular polyamide 6 (PA6), polyamide 12 (PA12), polyamide 10, polyamide 610, polyamide 66, polyamide based on aliphatic and cycloaliphatic constituents such as in particular MACM12 or amorphous co-polyamide, preferably based on PA12, or copolymers or mixtures thereof.

The resistive element may contain carbon, preferably graphene. Graphene can be a form of graphene called graphene microparticles, preferably in a form of nanoparticles (for example 1nm - 100nm) of graphene, either nanotubes, or nano-spheres, or graphene nano-wires. This form of graphene is preferred for screen printing processes, in particular slot dies so as not to block the ink outlet nozzles. Sintering can be done at temperatures low enough not to damage the polymer layers. The conductors can be made of metal, for example silver or copper.

According to a particular embodiment of the invention, the conductive layer comprises hybrid graphene, which has advantageous conductive properties.

Claims (4)

1. Device for thawing a roadway, the device comprising an electrothermal structure (100), flexible, substantially planar, having a front face intended to allow infrared rays to pass through and a rear face opposite the front face, the structure having a width and a length, i.e. a surface, the structure (100) comprising: at least one electrical input terminal (131); at least one electrical output terminal (132); a substrate for receiving a plurality of layers of the structure, the substrate comprising at least one polymeric substrate layer (110); at least one electrothermal layer (140) comprising a resistive element (149) having an input and an output, the resistive element having a substantially rectangular shape with a width substantially equal to the width of the structure; And at least one conductive layer (130) to connect: the input terminal (131) of the structure at the input of the resistive element (149); And the output terminal (132) of the structure at the output of the resistive element (149); the structure (100) being covered with a passivation comprising at least one polymeric passivation layer (120). 2. System for thawing a roadway comprising the device according to claim 1, the system further comprising a power supply configured to supply electricity to the two electrical terminals of the electrothermal structure (100) of the device. 3. Method of constructing a roadway having a plurality of layers including a roadway covering, the method comprising: installation of a thawing device according to claim 1 under the roadway covering. 4. Use of a structure for heating a bituminous ground, the structure being an electrothermal structure (100), flexible, substantially planar, having a front face intended to allow infrared rays to pass through and a rear face opposite the front face, the structure having a width and a length, i.e. a surface, the structure (100) comprising: at least one electrical input terminal (131); at least one electrical output terminal (132); a substrate for receiving a plurality of layers of the structure, the substrate comprising at least one polymeric substrate layer (110); at least one electrothermal layer (140) comprising a resistive element (149) having an input and an output, the resistive element having a substantially rectangular shape with a width substantially equal to the width of the structure; And at least one conductive layer (130) to connect: the input terminal (131) of the structure at the input of the resistive element (149); And the output terminal (132) of the structure at the output of the resistive element (149); the structure (100) being covered with a passivation comprising at least one polymeric passivation layer (120).