Heating elements for DIN rails

Abstract

The present disclosure relates to a heating element (5) for heating an electrical device mounted on a DIN rail (1). The heating element (5) comprises an elongated flexible sheet (11) made of an electrically insulating material and a layer containing a positive temperature coefficient paint (12) disposed on the upper surface (11a) of the flexible sheet (11). A method for mounting the heating element (5) to a DIN rail is provided. The method includes bending the flexible sheet (11) so that an inverted U-shape is formed along the length of the flexible sheet, and inserting the heating element (5) into a groove in the DIN rail (1) so that the bent flexible sheet remains in place due to the spring force of the bending. Use of the heating element for heating a DIN rail is also provided.

Description

[Technical field]

[0001] The present invention relates to a heating element for heating a DIN rail, to a method for mounting said heating element and to the use of a heating element with a DIN rail. [Background technology]

[0002] DIN rails are used to mount circuit breakers and control devices in racks. They are generally made from cold rolled carbon steel and may have a bright zinc plated or chromated finish. The DIN rail is for the mechanical support of the circuit breakers and control devices.

[0003] There are three main types of DIN rail: top hat rail, C-rail, and G-rail. Within these types, there are many variations, some of which are: -Top hat rail IEC / EN60715-35x7.5. In the US this is known as TS35 rail. -Top hat rail IEC / EN60715-35x15, also known in the US as TS35 rail. -5mm x 7.5mm top hat rail (EN50022, BS5584, DIN46277-3) -Miniature top hat rail, 15mm x 5.5mm (EN50045, BS6273, DIN46277-2) -75mm wide top hat rail (EN50023, BS5585) -C20 (The last number corresponds to the vertical height of the rail. For example, AS2756.1997(C3)) -C30 -C40 -C50 -EN50035 (G32 in the US), BS5825, DIN46277-1

[0004] DIN rails are entirely elongated rails with an elongated flat back portion to be fixed to a suitable surface. They also have two protrusions on the upper and lower sides of the elongated flat back portion for mounting electrical devices. These protrusions have different shapes and sizes for different types. Different cross sections of DIN rails are illustrated in Figures 1 to 3. Figure 1 shows a top hat rail, Figure 2 shows a C-shaped rail, and Figure 3 shows a G-shaped rail.

[0005] A challenge with rack cabinets, especially those located outdoors, is the temperature change of the cabinet. Circuit breakers are designed to interrupt current to a circuit when it exceeds a certain amperage. If the cabinet temperature drops too low, the circuit breaker will trip and interrupt the current at a higher load, i.e., higher amperage, than specified.

[0006] Another challenge is that systems located in cold environments often accumulate condensation, which can damage electronic components.

[0007] A solution to the above is to place an electric heater with a temperature controller inside the cabinet so that the desired temperature can be maintained inside the cabinet. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to at least partially overcome the above problems and to provide an improved method for maintaining good operating temperatures of electrical equipment and avoiding condensation around electrical equipment in a cabinet, as well as to save energy.

[0009] The present disclosure aims to provide a heating element for heating a DIN rail, a method for mounting the heating element to a DIN rail, and the use of the heating element with a DIN rail. [Means for solving the problem]

[0010] This object is achieved by a heating element as defined in claim 1, by a mounting method as defined in claim 10 and by a use of the heating element as defined in claim 11.

[0011] According to some aspects of the present disclosure, a heating element is provided for heating an electrical device mounted on a DIN rail. The heating element comprises an elongated flexible sheet made of an electrically insulating material and a positive temperature coefficient or PTC paint disposed on the upper surface of the flexible sheet. The heating element is used to heat the electrical device mounted on the DIN rail, which also heats the DIN rail itself. By heating the electrical device and having the heating element close to the electrical device, it is not necessary to heat the entire rack cabinet to avoid condensation and circuit breaker malfunction. In other words, since the circuit breaker is heated by the heating element, there is no need to heat the cabinet and energy is saved. Because a positive temperature coefficient paint is used, no additional circuitry is required to control the temperature due to the self-limiting nature of the PTC paint.

[0012] It should be noted that the feature of a layer with PTC paint disposed on the top surface of a flexible sheet includes a PTC paint layer disposed directly on the top surface as well as a PTC paint layer disposed on the top surface with one or more layers of other materials between them, such as adhesive or insulating material, etc. In other words, the PTC paint layer disposed on the top surface can be disposed directly on the top surface or with one or more layers between them.

[0013] According to some embodiments, the positive temperature coefficient paint is disposed along substantially the entire length of the flexible sheet, such that the flexible sheet is capable of heating the electrical device along its entire length.

[0014] According to some embodiments, the positive temperature coefficient paint is disposed across at least 2 mm of the flexible sheet and in the central portion of the flexible sheet. The heating element will be positioned with its top surface facing the electrical device. The positive temperature coefficient paint disposed in the central portion of the flexible sheet and along its extension will provide good heating to the electrical device that will be mounted on the DIN rail.

[0015] According to some embodiments, the positive temperature coefficient paint is disposed across at least 75% of the width of the flexible sheet and in the central portion of the flexible sheet. How much of the top surface is covered by the paint depends on how much heat you want to achieve, which can vary for different types of users and regions.

[0016] According to some embodiments, the positive temperature coefficient paint is placed in multiple discrete locations on the top surface of the flexible sheet. This can have the advantage of a more uniform temperature across the heating element because it is easier to heat a few smaller spots of positive temperature coefficient paint than a large spot. Small dots of positive temperature coefficient paint are easier to achieve a uniform current flow than large areas of paint.

[0017] According to some embodiments, the electrically insulating material is comprised of a dielectric material such as polyester or plastic, both of which are inexpensive materials and easy to handle and shape.

[0018] According to some embodiments, the flexible sheet has an edge along each side thereof. The two elongated side edges are curved at the sides of the top surface. The curved edges allow the heating element to better fit a DIN rail that is curved between the protrusion and the flat back portion.

[0019] According to some embodiments, the length and width of the flexible sheet are adapted such that when the flexible sheet is bent into an inverted U-shape along its length, the flexible sheet fits within the groove of the DIN rail.

[0020] According to some aspects, the heating element includes wiring disposed in connection with the positive temperature coefficient paint for providing power to the positive temperature coefficient paint.

[0021] According to some aspects of the present disclosure, there is provided a method for mounting the above heating element to a DIN rail, the method including bending a flexible sheet such that an inverted U-shape is formed along the length of the flexible sheet, and inserting the heating element into a groove in the DIN rail such that the bent flexible sheet remains in place due to the spring force of the bend.

[0022] According to some aspects of the present disclosure, there is provided a use of a heating element according to the above for heating a DIN rail, where the heating element is attached to a DIN rail by bending a flexible sheet into an inverted U-shape along its length and placing the bent sheet into a groove in the DIN rail such that the bent sheet remains in place due to the spring force of the bend.

[0023] According to an alternative embodiment of the present disclosure, a DIN rail for mounting electrical devices is provided. The DIN rail includes an elongated support section with a back side and a front side. The front side includes two elongated mounting flanges along both sides thereof and an elongated groove therebetween for mounting electrical devices. The DIN rail includes at least one heating element disposed in direct contact with the support section, the at least one heating element including at least one positive temperature coefficient or PTC heater. Electrical devices mounted on the DIN rail will be heated by both thermal radiation of the heater and the DIN rail, and by thermal conduction through the DIN rail. By heating the DIN rail and having the heating element close to the electrical devices, it is not necessary to heat the entire rack cabinet to avoid condensation and malfunction of circuit breakers. In other words, since the circuit breakers are heated by the heated DIN rail, there is no need to heat the cabinet, thus saving energy. Because a PTC heater is used, no additional circuitry is required to control the temperature due to the self-limiting nature of the PTC heater.

[0024] Different aspects of the alternative embodiments are described below.

[0025] According to some embodiments, at least one heating element is disposed in the groove. When positioned in the groove, the heating element is physically protected by the mounting flange and the support section.

[0026] According to some embodiments, the at least one heating element comprises a material surrounding the at least one positive temperature coefficient heater. The material is made of silicone and has a contour to fit into the groove and be held there by a mounting flange. Silicone is a flexible material, which allows the heating element to be seated in the groove by pressing it. The silicone will deform slightly at the edges to hold the heating element in place. This is very efficient for anchoring the heating element.

[0027] According to some embodiments, the at least one heating element is secured to the support section of the groove by at least one elastic element, which is clamped between two opposing flanges, thereby holding the at least one heating element in place in the groove. By using the elastic element, the heating element can be instantly attached to the groove. This is also a cheap and quick way to secure the heating element.

[0028] According to some embodiments, the at least one heating element is fixed to the support section by adhesive. Very strong adhesives exist. Adhesives are a quick and cheap way to adhere the heating element to the support section. The use of both adhesive and elastic elements for fixing the heating element can be efficiently used in mass production of DIN rails.

[0029] According to some embodiments, at least one heating element includes wiring for powering at least one positive temperature coefficient heater, the wiring being disposed in the groove. An advantage of this is that the wiring is physically protected in the groove by the mounting flange. Thus, the wiring is protected from physical damage and from being caught during handling. Another advantage is that it is visually pleasing to hide the wiring in the groove so that it is not visually noticeable.

[0030] According to some embodiments, at least one heating element is mounted on the back side of the support section. To simplify mass production of the DIN rail, the heating element may be mounted on the back side of the support section. This may also be advantageous depending on the type of DIN rail standard used. For some standards, the heating element may get in the way of mounting electrical equipment when placed in the groove. In such cases, it is advantageous to place the heating element on the back side.

[0031] According to some embodiments, at least one heating element is embedded in the material of the support section. This is advantageous, especially in harsh environments where the heating element and / or wiring needs to be protected from the environment. This can also be a very safe alternative, since the user of the DIN rail will not be able to access the heating element or its wiring.

[0032] According to some embodiments, the at least one heating element comprises a plurality of heating elements spaced apart from one another along an elongated support section. DIN rails come in a variety of lengths and they typically have regularly spaced holes in the support section for attachment to a surface, for example with screws, etc. The heating elements may thereby be distributed at a distance between them such that the holes are accessible for attachment of the rail.

[0033] According to some embodiments, the heating elements are evenly distributed along the length of the elongated support section. Evenly distributed heating elements can be advantageous in production because it eliminates re-distances and can be visually pleasing with regular spacing between heating elements.

[0034] According to some embodiments, each of the at least one heating element comprises multiple positive temperature coefficient heaters distributed over the heating element. The PTC elements can be produced in a variety of sizes and shapes, so that each heating element may comprise one or several PTC heaters 6. To simplify production, one PTC heater per heating element may be advantageous, but two or more PTC heaters may provide a more even spread of heat.

[0035] According to some embodiments, the positive temperature coefficient heaters are evenly distributed along the length of the heating element, the advantage of which is an even distribution of heat in the heating element.

[0036] According to some embodiments, the positive temperature coefficient heater is disposed between two steel plates disposed along the length of the heating element, and the positive temperature coefficient heater and the steel plates are embedded in an electrically insulating material.

[0037] According to some embodiments, the at least one heating element has a maximum surface temperature of 30-45°C, preferably a maximum temperature of 40°C. This temperature ensures good operating temperatures for electrical devices mounted on the DIN rail. Electronic devices are typically made to function best at room temperature or slightly above room temperature. A surface temperature of 30-45°C will provide optimal operating conditions for electrical devices.

[0038] According to an embodiment of the present disclosure, there is provided the use of a DIN rail according to any of the above features to heat an attached electrical device.

[0039] According to an embodiment of the present disclosure, there is provided a DIN rail system according to the features of any of the above alternatives. The system includes a circuit breaker mounted on the DIN rail and electrically connected to at least one heating element. With the circuit breaker for the at least one heating element already mounted on the DIN rail, the DIN rail system provides a provision for using the DIN rail resulting in optimal operating conditions for electrical equipment. The DIN rail system is thus easy to mount on a surface and connect electricity to the circuit breaker.

[0040] According to some embodiments, the circuit breaker is a miniature circuit breaker or MCB.

[0041] The present invention will now be explained in more detail by describing various embodiments of the invention with reference to the accompanying drawings. [Brief description of the drawings]

[0042] [Figure 1] FIG. 2 is a cross-sectional view of a top hat rail. [Diagram 2] A cross-sectional view of a C-rail. [Diagram 3] A cross-sectional view of a G-type rail. [Figure 4] FIG. 1 shows a heating element with an elongated sheet. [Diagram 5] FIG. 2 shows a heating element bent into an inverted U shape from the side. [Figure 6] FIG. 1 shows a DIN rail with heating elements disposed in grooves. [Figure 7] FIG. 7 is the same as FIG. 6, but seen from the side. [Figure 7A] FIG. 8 is the same as FIG. 7, but the DIN rail is a G-type rail. [Figure 8] FIG. 2 shows a heating element placed in a groove of a DIN rail with parts of an electrical device mounted on said DIN rail. [Figure 9] FIG. 9 is an exploded view of the arrangement of FIG. 8. [Figure 10] FIG. 1 shows a flexible insulating material with printed wiring and PTC paint. [Figure 11] FIG. 11 is a cross-sectional view of a portion of FIG. 10 showing the PTC paint patch, wiring, and encapsulation. [Figure 12] FIG. 1 shows an example of a DIN rail with heating elements arranged in grooves, viewed from above. [Figure 13] FIG. 11 is a side view of the DIN rail in FIG. 10. [Figure 14] FIG. 6 is a cross-sectional view of the DIN rail of FIG. 4 and FIG. 5. [Figure 15] FIG. 1 is a cross-sectional view of an example DIN rail with a heating element fitted into a groove. [Figure 16] FIG. 7 is a perspective view of the DIN rail of FIGS. 4, 5, and 6. [Figure 17] FIG. 1 is a cross-sectional view of an example DIN rail with an embedded heating element. [Figure 18] 1 is a cross-sectional view of an example heating element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Aspects of the present disclosure are described in more detail below with reference to the accompanying drawings. However, the devices disclosed herein can be embodied in many different forms and should not be construed as being limited to the aspects described herein. Like numbers in the figures refer to like elements throughout.

[0044] The technical terms used herein are for the purpose of describing certain aspects of the present disclosure only and are not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0045] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0046] As explained in the "Background Art" section, different cross sections of DIN rails 1 are illustrated in Figures 1 to 3. Figure 1 illustrates a top hat rail, Figure 2 illustrates a C-shaped rail, and Figure 3 illustrates a G-shaped rail. DIN rails 1 are generally made from cold rolled carbon steel sheet with a bright surface finish that is zinc plated or chromated. Even though they are metal, they are only meant for mechanical support and are not used as busbars to carry electrical current, even though they may provide a ground connection chassis.

[0047] Note that two alternative solutions are presented herein, one associated with Figures 4-9 and one associated with Figures 10-16. Note that many aspects are applicable to both alternatives.

[0048] FIG. 4 shows a heating element 5 with an elongated sheet 11. According to some embodiments of the present disclosure, a heating element 5 is provided for heating an electric device mounted on a DIN rail 1. The heating element 5 includes an elongated flexible sheet 11 made of an electrically insulating material and a positive temperature coefficient paint 12 disposed on a top surface 11a of the flexible sheet 11. The positive temperature coefficient paint 12 includes, for example, silicone or a polymer blended with carbon. PTC paint is available from several manufacturers, the specific contents of which are not disclosed herein. An example of an electric device can be seen in FIG. 8 and FIG. 9, where it is illustrated as a circuit breaker. The electric device is, for example, a circuit breaker, a production control device, etc., and is adapted to be mounted on a DIN rail 1.

[0049] As can be seen in Figures 1-3, the DIN rail 1 comprises an elongated support section 2 with a back side and a front side. The front side comprises two elongated mounting flanges 3 along either side thereof and an elongated groove 4 therebetween for anchoring electrical equipment. In other words, the DIN rail 1 has first and second mounting flanges 3 extending longitudinally along either side of the support section 2. In the examples of various DIN rail standards, these features are common to all standards.

[0050] The elongated flexible sheet may have a slight bend around the centerline along the elongated shape. The heating element 5 is inserted into the groove 4 of the DIN rail. When inserted, the heating element 5 has an inverted U-shape as shown in FIG. 5. The top surface 11a of the heating element 5 faces upward and is located opposite the DIN rail when the heating element is attached to the DIN rail. FIG. 5 shows the heating element from the side bent into an inverted U-shape. It may be slightly pre-bent towards this shape to facilitate insertion of the heating element for the user. The elongated flexible sheet has a shape such that when inserted into the DIN rail, both legs of the U-shape press against the DIN rail and hold the heating element 5 in place on the DIN rail. The elongated flexible sheet is flexible such that when placed on the DIN rail, both legs of the U-shape press against the DIN rail and hold the heating element 5 in place on the DIN rail. Note that the flexible sheet may be pre-bent at an angle sharper than that shown in FIG. 5, so long as both legs of the U are pressed towards each other when pressed into the DIN rail.

[0051] The heating element 5 is used to heat the electrical equipment mounted on the DIN rail 1, which also heats the DIN rail itself. By heating the electrical equipment and having the heating element close to the electrical equipment, it is not necessary to heat the entire rack cabinet to avoid condensation and circuit breaker malfunction. In other words, since the circuit breakers are heated by the heater, there is no need to heat the cabinet and energy is saved. Because a positive temperature coefficient paint is used, there is no need for any additional circuitry to control the temperature due to the self-limiting nature of the PTC paint.

[0052] The advantage of using a positive temperature coefficient paint 12, or PTC paint 12, is that no temperature sensor is needed to turn the heat on and off to maintain the desired heating. The PTC paint 12 is a resistive heater, and when the PTC paint 12 reaches a certain temperature, the resistance increases and no further heating is achieved. In other words, the PTC material is designed to reach a maximum temperature because at a given temperature, any additional temperature increase encounters a greater electrical resistance. Thus, the PTC material is essentially self-limiting in temperature so that there is no danger of the heating element 5 overheating. The PTC material will not get hotter than the temperature at which the resistance of the material increases rapidly. Thus, it is not possible for the PTC material to get hotter than the temperature it was manufactured for.

[0053] The PTC paint 12 is manufactured to have a specified maximum temperature, and therefore is preselected in the design for what the maximum temperature will be.

[0054] According to some embodiments, the positive temperature coefficient paint 12 is disposed over substantially the entire length of the flexible sheet. Thus, the flexible sheet can heat the electrical device over its entire length. It is up to the designer whether the PTC paint 12 is disposed over the entire length or not. The PTC paint is the heating portion of the heating element 5, but it does not matter if there is a portion of the heating element without the PTC paint 12, because then that portion will simply not heat anything. The most efficient heating element, in terms of heating, is a heating element 5 with PTC paint over its entire length.

[0055] According to some embodiments, the positive temperature coefficient paint 12 is placed over at least 2 mm width of the flexible sheet 11 and in the central part of the flexible sheet 11. The PTC paint will be located with its top surface facing the electric device. Placing the PTC paint in the central part of the flexible sheet and along its extension will provide good heating to the electric device that will be mounted on the DIN rail. The central part means the part of the top surface of the flexible sheet, which is in the middle of the flexible sheet in terms of width and extends the entire length of the flexible sheet. In the example described below with respect to FIG. 7A, the PTC paint is slightly offset from the central part so that it is part of the heating element that protrudes between the mounting flanges. There are many alternatives on how the PTC paint 12 can be placed on the flexible sheet 11. A PTC paint with a high maximum temperature, when placed in a narrow part of the top surface, can provide the same amount of heat to the electric device as if the PTC paint was placed in a wider part on the top surface 11a. The thickness of the PTC paint also affects the heat received by the electric device. The width and thickness of the PTC paint can be varied depending on the use, since the required temperature depends on the environment in which the heating element will be used. According to some embodiments, the positive temperature coefficient paint is placed at least 7 mm or 10 mm wide of the flexible sheet 11 and in the central part of the flexible sheet 11. Furthermore, how much of the top surface is covered by the paint depends on how much heat is desired to be achieved, which can vary for different types of use and regions. The width of the PTC paint can also depend on the efficiency of the selected PTC paint. Some PTC paints are more efficient than others. According to some embodiments, the positive temperature coefficient paint 12 is placed at least 50% or 75% of the width of the flexible sheet 11 and in the central part of the flexible sheet 11.

[0056] According to some embodiments, PTC paint 12 is placed in multiple discrete locations on the top surface of flexible sheet 11. This can have the advantage of a more uniform temperature across the heating element because it is easier to heat a smaller spot of PTC paint than one large spot. It is easier to achieve a uniform current flow in a smaller dot of PTC paint than in one larger area of ​​paint.

[0057] It should be noted that the PTC paint does not have to be placed directly on the surface of the flexible sheet 11. For example, a layer of plastic or other flexible, insulating material may be in between. According to some embodiments, the PTC paint is applied, for example by gluing or by tape, onto a flexible insulating material that is mounted on the flexible substrate 11. According to some embodiments, the PTC paint and wiring for the power supply are encapsulated in the flexible insulating material to form a unit that is then attached to the flexible sheet 11.

[0058] According to some embodiments, the thickness of the PTC paint is 0.1 to 2 mm. Preferably, the thickness is 0.1 to 1 mm.

[0059] According to some embodiments, the electrically insulating material is comprised of a dielectric material, such as polyester or plastic. Both polyester and plastic are inexpensive materials and are easy to handle and shape. The electrically insulating material is a non-conductive material.

[0060] Some DIN rails are more curved and have the top side closer to the mounting flange than others. The flexible sheet can have curved edges to accommodate such differences and allow the heating element to be attached to DIN rails of different shapes with a good fit. According to some embodiments, the flexible sheet 11 has one edge 13 along each side thereof. The edges of these two elongated sides are curved at the side of the top surface 11a. According to some embodiments, the curve has a radius that is the same as the diameter of the flexible sheet. This radius may be smaller than the diameter. This radius can be selected differently to better fit different standards of DIN rails.

[0061] FIG. 6 shows a DIN rail with the heating element disposed in the groove. FIG. 7 shows the same as FIG. 6 but from the side. FIG. 7A shows the same as FIG. 7 but with the DIN rail being a G-type rail. As can be seen in FIG. 7A, the heating element can be used with DIN rails of different standards. According to some embodiments, the length and width of the flexible sheet 11 is adapted so that when the flexible sheet is bent into an inverted U-shape along its length, it fits into the groove of the DIN rail 1. Since there are many different DIN rail standards, the width cannot be specified closer than it should be to be able to be positioned according to the above description of the DIN rail. Thus, the width is determined when it is known which DIN rail the user will be using. The length can also be varied depending on the length of the DIN rail used. It should be noted that the heating element can protrude above the mounting flange of the DIN rail. If it protrudes slightly, the PTC paint will be closer to the electrical device it will heat, which can be advantageous. However, the heating element must not interfere with the installation of new electrical equipment on the DIN rail.

[0062] Figure 8 shows a heating element arranged in a groove of a DIN rail with parts of an electric device 14 attached to said DIN rail. Figure 9 is an exploded view of the arrangement of Figure 8. As can be seen in the drawing, the heating element 5 is arranged below the electric device 14, in the groove 4 of the DIN rail 1. In the drawing, the upper side of the flexible sheet abuts the electric device 14, but this is not necessary but is a possibility.

[0063] 5, 6, and 7, examples of wiring 8 for supplying power to the PTC paint 12 are shown. According to some embodiments, the heating element includes wiring 8 for supplying power to the positive temperature coefficient paint 12, which is disposed in connection with the positive temperature coefficient paint 12.

[0064] When the PTC paint 12 is placed at multiple discrete locations on the top surface of the flexible sheet 11, each dot or spot or patch of PTC paint is connected with a wire 8. According to some embodiments, the PTC paint is applied onto a flexible insulating material 15 along with the wires 8, as shown in Figures 10 and 11, and then coated onto the flexible insulating material 15 to provide a flexible insulating housing for the PTC paint and wires. The encapsulated PTC paint and wires are then placed onto a flexible substrate 11. The PTC paint and wires are printed, for example, onto the flexible sheet 11 or the flexible insulating material 15.

[0065] In Figures 10 and 11, a flexible insulating material 15 is shown with printed wiring 8 and PTC paint 12. Figure 10 shows the flexible insulating material 15 with printed wiring 8 and PTC paint 12, and Figure 11 shows a cross section of a portion of Figure 10 showing the PTC paint 12, wiring 8, and encapsulation 15. In these examples, the PTC paint 12 is disposed in multiple discrete locations on the top surface of flexible sheet 11. In the example shown, the PTC paint is disposed in the form of a PTC paint pattern.

[0066] As can be seen in FIG. 10, the wiring 8 has a grid design, such that each PTC paint patch 12 is connected to a positive + on one side and a negative - on the other side, so that the current flows through each PTC paint patch. An example of a terminal 16 that is connected to a power source is also shown. In FIG. 11, the layers are shown in cross section. A flexible insulating material 15 is used here for two layers of silver in the first print, which is the wiring 8, and then a layer of PTC paint 12. One layer of silver or three or more layers of silver are also alternatives. The silver and PTC paint are then encapsulated by two layers of flexible insulating material 15 in this example. The flexible insulating material 15 in the two top layers is, for example, an electrically insulating flexible plastic. The flexible insulating material 15 in the first layer, i.e. the base layer, is, for example, Mylar polyester. The base layer and the top layer of the flexible insulating material can be made of the same material. The encapsulation formed by the flexible insulating material 15 can also ensure that moisture does not come into contact with the wiring. The wiring 8 may be made of a material other than silver.

[0067] The example designs shown in Figures 10 and 11 are placed on a flexible sheet 5 to form the heating element 1. Alternatively, the PTC paint 12 and wiring 8 are printed directly onto the flexible sheet 5 and then encapsulated by a flexible insulating material 15. The examples shown will work with all the described variations of the flexible sheet 5.

[0068] The heating element is powered by, for example, riveted contacts at terminals 16 which can be plugged into a power source. The contacts are, for example, riveted with a plastic housing over the contacts.

[0069] The present disclosure also provides a method for mounting a heating element 5 according to any one of the above aspects to a DIN rail. The method includes bending a flexible sheet 11 such that an inverted U-shape is formed along the length of the flexible sheet, and inserting the heating element 5 into the groove 4 of the DIN rail 1 such that the bent flexible sheet stays in place due to the spring force of the bending. In other words, the heating element 5 is bent along its length, thereby allowing the heating element 5 to be pressed into the groove 4 of the DIN rail 1. Once inserted, the elasticity of the flexible material in the flexible sheet will hold the heating element 5 in place. Thus, the flexible sheet 11 is elastic.

[0070] Bending the flexible sheet 11 so that an inverted U-shape is formed along the length of the flexible sheet is done with PTC paint on the top surface, the underside of the U, so that when the heating element is inserted into the groove 4 of the DIN rail, the PTC paint is located on the side of the heating element facing away from the DIN rail.

[0071] The present disclosure also provides for the use of a heating element according to any one of the above aspects to heat a DIN rail, where the heating element is attached to the DIN rail by bending a flexible sheet 11 into an inverted U-shape along its length and placing the bent flexible sheet 11 into a groove in the DIN rail 1 such that the spring force of the bend keeps the bent flexible sheet 11 in place. Also here the top surface 11a is on the side of the heating element facing away from the DIN rail.

[0072] Note that a layer of PTC paint 12 is shown in Figure 4. In Figures 5-9, the PTC paint 12 is also present but not shown. The PTC paint 12 is always placed on the side of the heating element 5 that faces the electrical device 14 when the electrical device 14 is mounted on a DIN rail.

[0073] To ensure the safe functionality of the heating element 5, the heating element 5 may be connected to a circuit breaker to protect it from overload or short circuit. According to an embodiment of the present disclosure, a DIN rail system is provided with a DIN rail 1 including an elongated support section 2 with a back side and a front side. The front side has two elongated mounting flanges 3 along both sides thereof and an elongated groove 4 between them for anchoring an electric device 14. A heating element 5 according to any one of the above aspects is placed in the groove 4 of the DIN rail in an inverted U shape, with the top surface 11a facing the opposite side of the DIN rail. The DIN rail system comprises a circuit breaker mounted on the DIN rail 1 and electrically connected to the heating element 5. With the circuit breaker for the heating element 5 mounted on the DIN rail 1, the DIN rail system provides a provision for using the DIN rail 1 resulting in optimal operating conditions for the electric device. The DIN rail system is therefore easy to mount on a surface and connect electricity to the circuit breaker. The DIN rail 1 of the DIN rail system can of course follow any of the above aspects. Because all of the above can be combined with a circuit breaker, which is designed to be fixed to a protrusion / mounting flange of the DIN rail 1. According to some embodiments, the circuit breaker is a miniature circuit breaker or MCB, but it can also be an MCCB or molded case circuit breaker. One circuit breaker can also be connected to several heating elements, each arranged on several DIN rails of the same rack.

[0074] It should be noted that a length of DIN rail may be heated using one or more heating elements according to the above.

[0075] In the following, the alternatives shown in Figures 12 to 18 are described.

[0076] A DIN rail 1 for mounting electrical devices is disclosed. The DIN rail 1 comprises an elongated support section 2 with a back side and a front side. The front side comprises two elongated mounting flanges 3 along both sides thereof and an elongated groove 4 between them for anchoring electrical devices. In other words, the DIN rail 1 has first and second mounting flanges 3 extending longitudinally along both sides of the support section 2. In the examples of various DIN rail standards, these features are common to all standards. As can be seen in Figures 1-3 and in Figure 14 described below, the mounting flanges 3 are bent at a point to form a parallel portion with the support section 2. The function of the DIN rail 1, as well as the variations in shape and size, are common to those skilled in the art and are specified in the various standards described in the "Background Art".

[0077] The DIN rail 1 presented in this disclosure comprises at least one heating element 5 arranged in direct contact with the support section 2, the at least one heating element 5 comprising at least one positive temperature coefficient heater 6. In other words, the support section 2 is heated by the heating element 5 with a positive temperature coefficient or PTC heater. In other words, in the alternative shown in Figs. 12-18, the heating element comprises PTC heaters therein, these PTC heaters being preferably in the form of PTC ceramic stones. Another difference with the above mentioned feature is that the heating element is now mounted in direct contact with the support section 2. When an electric device is mounted on the DIN rail 1, the electric device will be heated both by heat radiation from the heater and the DIN rail 1, and by heat conduction through the DIN rail 1. By heating the DIN rail 1 and by having the heating element 5 close to the electric device, it is not necessary to heat the entire rack cabinet to avoid condensation and malfunction of the circuit breakers. In other words, since the circuit breakers are heated by the heated DIN rail 1, there is no need to heat the cabinet, so energy is saved. Because a PTC heater 6 is used, there is no need for any additional circuitry to control the temperature due to the self-limiting nature of the PTC heater 6.

[0078] There are several alternatives as to where to place the heating element 5 in direct contact with the support section 2, which are described further below.

[0079] The advantage of using a positive temperature coefficient heater 6, or PTC heater 6, is that no temperature sensor is needed to turn the heat on and off to maintain the desired heat. The PTC heater 6 is a resistive heater, and when the PTC heater 6 reaches a certain temperature, the resistance increases and no further heating is provided. In other words, the PTC material is designed to reach a maximum temperature because at a given temperature, any additional temperature increase encounters a greater electrical resistance. Thus, the PTC material is inherently self-limiting in temperature so that there is no danger of the heating element 5 overheating. The PTC material will not get hotter than the temperature at which the resistance of the material increases rapidly. Thus, the PTC material cannot get hotter than the temperature at which it will fail.

[0080] The PTC heaters 6 in the form of PTC ceramic stones are manufactured to have a defined maximum temperature. The PTC heaters 6 are therefore selected in advance based on their maximum temperature. The structure of the PTC heaters 6 is known to those skilled in the art and will not be described further here.

[0081] The PTC heater 6 in the form of a PTC ceramic stone can be manufactured in many different sizes, for example about 20x15x2mm. The PTC heater 6 is for example 3-40mm long, 1-25mm wide and 0.1-5mm thick.

[0082] An example of a DIN rail 1 with heating elements 5 is shown in figures 12 to 16. In the example shown, at least one heating element 5 is placed in the groove 4. The electrical device is typically mounted to a mounting flange 3. Thus, there is space in the groove 4 for the heating element 5. When positioned in the groove 4, the heating of the at least one heating element is also physically protected by the mounting flange 3 and the support section 2. In this example, the size and shape of the heating element 5 is made to fit within the groove 4.

[0083] In Figures 12 to 16 an elongated support section 2 and two elongated mounting flanges 3 can be seen.

[0084] In the cross-sectional view of Figure 14, it can be seen that this example of a DIN rail 1 differs slightly from the DIN rail 1 in Figures 1 to 3. The mounting flange 3 is more curved than in the previous example. The features presented in this disclosure are applicable to all DIN rail standards unless expressly stated otherwise.

[0085] In the cross-sectional view of FIG. 15, an example of a method for fixing a heating element 5 in a groove is shown. According to some embodiments, at least one heating element 5 comprises a material surrounding at least one positive temperature coefficient heater 6. This material is made of silicone and has a contour to fit into the groove 4 and is held in the groove 4 by a mounting flange 3. Silicone is a flexible material, which allows the heating element to be pressed into the groove. The silicone will deform slightly at the edges to hold the heating element in place. This is a very efficient method for fixing the heating element. It may be combined with any other method to fix the heating element. To improve the thermal conductivity and rigidity of the silicone, it may be mixed with, for example, silicon. Other materials may be added to improve the thermal conductivity and / or rigidity of the material.

[0086] One way to attach the heating element 5 to the groove 4 is to use an adhesive. Thus, according to some embodiments, the at least one heating element 5 is fixed to the support section 2 of the groove 4 by an adhesive. There are very strong adhesives. An adhesive is a quick and cheap way to attach the heating element 5 to the support section 2. The adhesive may be thermally conductive to help transfer heat from the at least one heating element 5 to the support section 2. The adhesive may be, for example, a glue or a resin.

[0087] There are alternatives to mounting the at least one heating element 5 with adhesive, such as fasteners, cable ties, or screws. According to some embodiments, the at least one heating element 5 is fixed to the support section 2 of the groove 4 by at least one elastic element 7. This at least one elastic element 7 is clamped between two opposing flanges 3, thereby holding the at least one heating element 5 in place in the groove 4. In Figs. 4 to 7, the elastic element 7 is shown as a member of elastic material, which is clamped between the insides of the mounting flanges 3. In the example shown, there are two elastic elements 7 holding each heating element 5, but one or several elastic elements 7 could be used to hold the heating elements 5. The elastic elements 7 are preferably made of a thermally conductive material. The heating elements 5 could also be mounted with both adhesive and elastic elements 7. By using the elastic elements 7, the heating elements 5 can be mounted in the groove 4 instantly. This is also a cheap and quick way to fix the at least one heating element 5. Another term for resilient is restraint. This is because it is the elastic material that restrains the heating element 5 in the groove 4 .

[0088] In the use of the elastic element 7, preferably the mounting flange 3 is used in combination with a curved DIN rail standard, as shown for example in figures 4 to 8. The elastic element 7 is more easily fixed to the curved mounting flange 3. The DIN rail 1 may alternatively be equipped with protrusions for fixing the elastic element 7.

[0089] The use of both adhesive and at least one elastic element 7 for the fixing of the at least one heating element 5 can be efficiently used in mass production of DIN rails 1 .

[0090] At least one heating element 5 may include wiring 8 for powering at least one positive temperature coefficient heater 6. The wiring 8 is disposed, for example, in the groove 4. The wiring 8 is disposed in the bend between the support section 2 and the mounting flange 3, as can be seen, for example, in Figs. 12 and 16. An advantage of disposing the wiring 8 in the groove 4 is that the wiring 8 is physically protected in the groove 4 by the mounting flange 3, thereby protecting the wiring 8 from physical damage and from getting caught during handling. Another advantage is that it is visually pleasing to hide the wiring 8 in the groove so that it is not visually noticeable.

[0091] To simplify mass production of the DIN rail 1, the at least one heating element 5 can be mounted on the back side of the support section 2. Depending on the method for producing the DIN rail 1, it may be advantageous to place the at least one heating element 5 on the back side. According to some embodiments, the at least one heating element is mounted on the back side of the support section 2. This may also be advantageous depending on the type of standard used for the DIN rail 1. For some standards, the at least one heating element 5, when placed in the groove 4, may be in the way of mounting an electric device. In such cases, it is advantageous to place the heating element 5 on the back side. The at least one heating element 5 can be mounted on the back side, for example, by means of adhesive. Furthermore, as an alternative to mounting the at least one heating element 5 by means of adhesive, fasteners, cable ties or screws are used. Since the heating element 5 is then positioned between the support section 2 and the surface on which the DIN rail 1 is mounted, it is preferable that the at least one heating element 5 has structural integrity so that the material of the at least one heating element 5 is not damaged when mounting the DIN rail 1. The at least one heating element may have an outer material of, for example, steel, silicone, or a mixture of silicone and silicon.

[0092] An alternative to arranging the at least one heating element on the back side 2 or in the groove 4 is to arrange it inside the material of the support section 2. An example of this is shown in FIG. 17, where the DIN rail 1 is a C-section DIN rail 1 with an embedded heating element. The feature is, of course, applicable to all DIN rail standards, not only to the C-section. Thus, according to some embodiments, the at least one heating element is embedded in the material of the support section 2. The support section 2 is in this case made of two layers with the at least one heating element 5 between them. This is particularly advantageous in harsh environments where the at least one heating element 5 and / or the wiring 8 need to be protected from the environment. This can also be a very safe alternative, since the user of the DIN rail 1 would not be able to access the at least one heating element 5 or its wiring 8 if the wiring 8 was also embedded in the support section 2. As the at least one heating element 5 is not accessible to the user of the DIN rail 1, the service life of the DIN rail 1 can be increased.

[0093] Both when the at least one heating element 5 is disposed unconcealed in the groove 4 or on the backside, and when it is disposed embedded in the material of the support section 2, the outer surface of the at least one heating element 5 preferably does not conduct electrical current. The PTC heater 6 is therefore electrically insulated from the surface of the heating element 5. This can be done, for example, with an electrically insulating material disposed around the PTC heater 6. The electrically insulating material is preferably thermally conductive, increasing the heat transfer to the surface of the at least one heating element 5.

[0094] There are many ways to realize and arrange the heating elements 5. According to some embodiments, the at least one heating element 5 comprises a plurality of heating elements 5 arranged at a distance from each other along the elongated support section 2. DIN rails 1 are of various lengths and they usually have regularly spaced holes 10 in the support section 2 for fastening to the surface, for example using screws or the like. Thereby the heating elements 5 can be distributed at a distance between the heating elements 5 such that the holes 10 are accessible for fastening the rail. If the DIN rail 1 is short, only one heating element 5 can be provided in the support section 2. According to some embodiments, the plurality of heating elements 5 are distributed evenly along the length of the elongated support section 2. An even distribution of the heating elements 5 can be advantageous in production, since it is not re-distanced and can also be visually pleasing with a regular spacing between the heating elements 5. If the fastening holes 10 in the support section 2 are arranged at regular intervals, the heating elements 5 can be regularly arranged between the holes 10.

[0095] One or more PTC heaters 6 may be present in the heating element 5. According to some embodiments, each of the at least one heating element 5 comprises a plurality of positive temperature coefficient heaters 6 distributed on the heating element 5. The PTC elements can be produced in various sizes and shapes, so that each heating element 5 may comprise one or several PTC heaters 6. To simplify production, one PTC heater per heating element 5 may be advantageous, but two or more PTC heaters may provide a more even heat spread. According to some embodiments, the positive temperature coefficient heaters 6 are evenly distributed along the length of the heating element 5. The advantage of this is an even heat distribution on the heating element 5.

[0096] The heating element 5 can be designed in different ways to achieve the desired properties. According to some embodiments, at least one heating element 5 has a maximum surface temperature of 30-45°C, preferably the maximum temperature is 40°C. This temperature ensures a good operating temperature for the electrical devices mounted on the DIN rail 1. Electronic devices are usually made to function best at room temperature or slightly above room temperature. A surface temperature of 30-45°C will provide optimal operating conditions for the electrical devices.

[0097] To reach a maximum surface temperature of 30-45°C, a small PTC heater with a higher maximum temperature may be used. The temperature decreases as heat is conducted through the material of the heating element 5. For example, a PTC heater with a maximum temperature of 70-100°C may be used. Another way to achieve a maximum surface temperature is to use several PTC heaters 6, or larger PTC heaters with a maximum temperature close to the desired surface temperature. For example, three PTC heaters 6 with a maximum temperature of 50°C may be used to reach a surface temperature of 45°C.

[0098] Since PTC heaters 6 come in many different sizes and maximum temperatures, it is up to the system designer to choose which and how many PTC heaters 6 to use. Depending on which standard DIN rail shape is used, PTC heaters 6 of different sizes and different maximum temperatures may be desirable. For example, it may be advantageous to use a larger PTC heater 6 for a DIN rail 1 with a wider support section and a smaller PTC heater 6 for a narrower DIN rail 1.

[0099] There are various ways to power a PTC heater. One way is shown in FIG. 18, which shows a cross section of an example heating element 5. In the example shown, a positive temperature coefficient heater 6 is placed between two steel plates 9 placed along the length of the heating element 5, and the positive temperature coefficient heater 6 and the steel plates 9 are embedded in an electrically insulating material. In other words, the two steel plates 9 are elongated and extend through the length of the heating element 5, and one or more PTC heaters 6 are placed between the two steel plates 9. Wiring 8, shown in the drawing, is connected to each steel plate to provide power to the PTC heaters 6.

[0100] Another example of how power can be provided to the PTC heater 6 is to shave the wires 8 through the heating element 5 so that they are not insulated where they abut the PTC heater 6. In other words, as can be seen in the drawing, two wires 8 through at least one heating element 5 are placed on either side of the PTC heater 6, whereby the two wires abut the PTC heater 6, and in the contact area the wires 8 are shave to expose the conductive wires.

[0101] In the example shown in FIG. 17, the PTC heaters 6 are surrounded by a thermally conductive material to form the heating element 5. The thermally conductive material is, for example, aluminum or steel. In other words, at least one heating element 5 comprises an aluminum or steel material embedded with one or more PTC heaters 6 with some insulation and wiring 8. According to some embodiments, at least one heating element 5 has an elongated shape with the PTC heaters 6 arranged in rows spaced apart from each other. According to some embodiments, at least one heating element 5 comprises two or more rows of PTC heaters 6.

[0102] The use of a DIN rail 1 with any of the above features provides heating for electrical equipment mounted preferably in a rack cabinet or control cabinet.

[0103] To ensure the safe functionality of the DIN rail 1, the DIN rail 1 may be connected to a circuit breaker to protect against overload or short circuit. According to an embodiment of the present disclosure, a DIN rail system is provided having a DIN rail 1 including an elongated support section 2 with a back side and a front side. The front side comprises two elongated mounting flanges 3 along both sides thereof and an elongated groove 4 between them for anchoring an electric device. The DIN rail 1 comprises at least one heating element 5 arranged in direct contact with the support section 2, the at least one heating element 5 comprising at least one positive temperature coefficient heater 6. The DIN rail system comprises a circuit breaker mounted on the DIN rail 1 and electrically connected to the heating element 5. With the circuit breaker for the at least one heating element 5 already mounted on the DIN rail 1, the DIN rail system provides a preparation for using the DIN rail 1 resulting in optimal operating conditions for the electric device. The DIN rail system is therefore easy to mount on a surface and connect electricity to the circuit breaker. The DIN rail 1 of the DIN rail system can of course follow any of the above-mentioned aspects. 1, since all of the above can be combined with a circuit breaker, which is designed to be fixed to a protrusion of the DIN rail 1. According to some embodiments, the circuit breaker is a miniature circuit breaker or MCB, but it can also be an MCCB or molded case circuit breaker. The circuit breaker is not shown in the drawings, since any standard circuit breaker suitable for use with at least one heating element 5 and mountable on the DIN rail 1 can be used.

[0104] [Aspects] Aspect 1: A DIN rail (1) for mounting electrical equipment, the DIN rail (1) comprising an elongated support section (2) with a front side and a back side, the front side comprising two elongated mounting flanges (3) along either side of the front side and an elongated groove (4) therebetween for anchoring electrical equipment, the DIN rail comprising at least one heating element (5) arranged in direct contact with the support section (2), the at least one heating element (5) comprising at least one positive temperature coefficient heater (6).

[0105] Aspect 2: The DIN rail (1) according to aspect 1, wherein at least one heating element (5) is disposed in the groove (4).

[0106] Aspect 3: A DIN rail (1) as described in aspect 2, wherein at least one heating element (5) comprises a material surrounding at least one positive temperature coefficient heater (6), the material being made of silicone and having an outer shape to fit within the groove (4) and held in the groove by a mounting flange (3).

[0107] Aspect 4: A DIN rail (1) as described in aspect 2, wherein the at least one heating element (5) is fixed to the support section (2) of the groove (4) by at least one elastic element (7), which is clamped between two opposing flanges (3), thereby holding the at least one heating element (5) in a predetermined position in the groove (4).

[0108] Aspect 5: A DIN rail (1) as described in any one of aspects 1 to 4, wherein at least one heating element (5) is fixed to the support section (2) by adhesive.

[0109] Aspect 6: A DIN rail (1) as described in any one of aspects 2 to 5, wherein at least one heating element (5) includes wiring (8) for supplying power to at least one positive temperature coefficient heater (6), the wiring (8) being disposed in the groove (4).

[0110] Aspect 7: A DIN rail (1) as described in aspect 1 or 5, wherein at least one heating element (5) is mounted on the rear side of the support section (2).

[0111] Aspect 8: A DIN rail (1) as described in aspect 1, wherein at least one heating element (5) is embedded in the material of the support section (2).

[0112] Aspect 9: A DIN rail (1) as described in any one of aspects 1 to 8, wherein at least one heating element (5) comprises a plurality of heating elements (5) arranged spaced apart from one another along the elongated support section (2).

[0113] Aspect 10: A DIN rail (1) as described in aspect 9, wherein the multiple heating elements (5) are evenly distributed along the length of the elongated support section (2).

[0114] Aspect 11: A DIN rail (1) as described in any one of aspects 1 to 10, wherein each of the at least one heating element (5) comprises a plurality of positive temperature coefficient heaters (6) distributed across the heating element (5).

[0115] Aspect 12: A DIN rail (1) as described in aspect 11, wherein the positive temperature coefficient heaters (6) are evenly distributed along the length of the heating element (5).

[0116] Aspect 13: A DIN rail (1) as described in aspect 11 or 12, wherein the positive temperature coefficient heater (6) is disposed between two steel plates (9) arranged along the length of the heating element (5), and the positive temperature coefficient heater (6) and the steel plates (9) are embedded in an electrically insulating material.

[0117] Embodiment 14: A DIN rail (1) according to any one of embodiments 1 to 13, wherein the heating element (5) has a maximum surface temperature of 30 to 45°C, preferably a maximum surface temperature of 40°C.

[0118] Aspect 15: Use of a DIN rail (1) according to any one of aspects 1 to 14 for heating an attached electrical device.

[0119] Aspect 16: A DIN rail system comprising a DIN rail (1) according to any one of aspects 1 to 14, the DIN rail (1) being mounted on the DIN rail (1) and including a circuit breaker electrically connected to at least one heating element (5).

[0120] Aspect 17: A DIN rail system as described in aspect 16, wherein the circuit breaker is a miniature circuit breaker or MCB. [Explanation of symbols]

[0121] 1 DIN rail 2 Support Section 3 Mounting flange 4 grooves 5 heating element 6 PTC heater 7 Elastic Elements 8 Wiring 9 steel plate 10 holes 11 Flexible sheet 11a Top side 12 Positive Temperature Coefficient Paint 13 Edge 14 Electrical Equipment 15 Flexible insulating materials 16 Terminals

Claims

1. 1. A heating element (5) for heating an electrical device mounted on a DIN rail (1) and arranged in a groove of the DIN rail (1), characterized in that the heating element (5) comprises an elongated flexible sheet (11) made of an electrically insulating material and a layer including a positive temperature coefficient paint (12) arranged on an upper surface (11a) of the flexible sheet (11).

2. The heating element (5) of claim 1, wherein the positive temperature coefficient paint (12) is disposed over substantially the entire length of the flexible sheet.

3. 2. The heating element (5) of claim 1, wherein the positive temperature coefficient paint (12) is disposed across a width of at least 2 mm of the flexible sheet (11) and in a central portion of the flexible sheet (11).

4. 2. The heating element (5) of claim 1, wherein the positive temperature coefficient paint is disposed across at least 75% of the width of the flexible sheet (11) and in a central portion of the flexible sheet (11).

5. The heating element (5) of claim 1, wherein the positive temperature coefficient paint is disposed at a plurality of distinct locations on the upper surface (11a) of the flexible sheet (11).

6. The heating element (5) according to claim 1, wherein the electrically insulating material is made of a dielectric material such as polyester or plastic.

7. 2. The heating element (5) of claim 1, wherein the flexible sheet (11) has one edge (13) along each side of the flexible sheet (11), the edges of the two elongated sides being curved at the sides of the upper surface (11a).

8. 2. The heating element (5) of claim 1, wherein the length and width of the flexible sheet (11) are adapted so that the flexible sheet fits into a groove of a DIN rail (1) when the flexible sheet is bent into an inverted U-shape along its length.

9. The heating element (5) of claim 1, further comprising wiring (8) arranged in connection with the positive temperature coefficient paint (12) for supplying power to the positive temperature coefficient paint (12).

10. A method for mounting a heating element (5) according to any one of claims 1 to 9 on a DIN rail, comprising the steps of: bending said flexible sheet (11) such that an inverted U-shape is formed along the length of the flexible sheet; and inserting the heating element (5) into a groove in the DIN rail (1) such that the bent flexible sheet stays in place due to the spring force of the bend.

11. Use of a heating element according to any one of claims 1 to 9 for heating a DIN rail, said heating element being attached to a DIN rail by bending a flexible sheet (11) into an inverted U-shape along its length and placing said flexible sheet (11) in a groove in the DIN rail (1) such that the bent flexible sheet (11) stays in place due to the spring force of the bend.

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