Abstract: An electrical connection element to be brazed on a conductive layer placed on a glazing consists of a segment of flexible metal braid, a plug mounted on one of its ends and a connection piece to be brazed mounted on the other end. The connection piece to be brazed is a piece of rigid sheet metal.

Abstract: Main electrodes 3, 4 are formed on the inner surface of a flexible insulating sheet 2 along opposed edges thereof, and junction electrode sections 3a, 4a are formed on the main electrodes at their central portions. Comb-toothed sub-electrodes 7, 8 extend from the main electrodes 3, 4 into interdigitated relation, and a layer of electrically resistive material 9 is formed over the main and sub-electrodes. Electrically conductive paths 5, 6 are formed on the inner surface of a terminal mounting substrate to which terminals are attached, and one ends of the conductive paths 5, 6 are connected with the corresponding junction electrode sections 3a, 4a while the other ends thereof are connected with the terminals to be connected to a power supply. The terminal mounting substrate with the terminals is bonded to the insulating sheet.

Abstract: A heated windshield wiper with a detachable brush assembly. An enclosed metal housing contains the heating element supplied with electrical energy from the engine's battery to heat the attached wiper. The brush is slidably mounted within an external housing channel and retained therein by two spring tab members extending through openings in the housing. Fluid from the automobile's windshield washer reservoir may be supplied heat from a second heating element before sprayed on the windshield.

Abstract: In a wetness sensor for a window of a motor vehicle, a heating resistor arranged in the window and powered by DC current can be connected to a measuring device for measuring an AC impedance of the heating resistor, in particular the capacitive portion thereof. The impedance varies with the amount of wetness and, thereby, serves as a measure of the wetness. A capacitor is used to bring the sensor near resonance for improved sensitivity.

Abstract: A system for automatically defogging both the windshield and rear window of an automobile. The system includes moisture and dew detection sensors positioned on the interior surfaces of the windshield and the rear window of the automobile. The sensors transmit an electrical current signal to a program control module. If the current received by the program control module from either of the windshield sensors exceeds a predetermined response threshold, it will energize a relay to activate the windshield blower. On the other hand, should the program control module receive a signal from one of the sensors on the rear window, it will energize another relay to activate a resistance heating grid on the rear window. When the condensation on either the windshield or rear window has been evaporated, the program control module will deactivate the associated defogging device.

Abstract: The wiper rest area of an automotive windshield is heated by a heatable member optionally mounted on a polyester substrate or heating element. The windshield includes outer and inner glass sheets secured together by an interlayer. The heating element is positioned on inner surface of the outer glass sheet and held in position by the interlayer securing the inner and outer sheets together. The heating element or heatable member has extensions extending beyond the edge of the windshield to provide external electrical access to the heatable member to power the heating element to heat the wiper rest area or position.

Abstract: A laminated window includes at least one rigid external substrate (5) and a sheet made of flexible plastic material (6) which is adjacent to the substrate (5). The window is equipped with an electrostatic protection circuit which is capable of dissipating the charges which have accumulated on the external sheet (7). This circuit includes conducting elements (2) which cross through at least the substrate and at least one part of the sheet made of plastic material (6). The conducting elements (2) are connected to a collector element (3) which is connected to the ground (4) and embedded in the sheet made of flexible plastic material (6).

Abstract: An electric heating attachment adds heating elements to the interior of the windshield to prevent the buildup of ice under the rest zone of the windshield wipers. The accessory plugs into the vehicle cigarette lighter socket. A heat imparting strip is positioned in the vicinity of the vehicle's windshield wipers to prevent ice accumulation. The heating elements concentrate a predetermined limited amount of electric heating on the rest area of the windshield wipers, to prevent the accumulation of ice thereto.

Abstract: Use of PTC circuit protection devices in motor vehicle wiring systems. The devices can replace some or all of the fuses conventionally used. Preferred devices contain PTC conductive polymers. Because the PTC devices can be reset without physical access to them, the wiring system can be arranged more efficiently and more economically. For example, the size of at least some of the wires of the harness can in many cases be reduced.

Abstract: A glazing panel includes at least one sheet of vitreous material; a conductive transparent coating which is provided on at least one face of at least one sheet of the at least one sheet of vitreous material and which constitutes a heating element for the glazing panel when connected to an electrical power source; and a control circuit for controlling heating power output of the glazing panel, the control circuit including adjustable means for controlling the heating power output to a preselected level as a function of voltage of the electrical power source and electrical resistance of the heating element.

Abstract: The invention relates to a method for fabricating laminated glazing comprising at least one enamel layer, wherein is deposited an enamelled composition comprising an anti-adhesive frit, a medium and, optionally, a low melt point frit on a portion of the internal face of a glass sheet; the enamelled glass sheet is subjected to heat treatment at a temperature between 150.degree. C. and the glass deformation temperature, and a second glass sheet is placed on the enamelled side of the first glass sheet before simultaneous bending of the two glass sheets, final firing of the enamel taking place during bending.

Abstract: A windshield wiper is provided with an electrical heater that extends along a face of secondary pressure frames used to carry a squeegee and forms a flexible support on a primary pressure frame. A shroud is wrapped about a primary pressure frame and is formed with a reversely bent portion to allow a bead portion of the squeegee to form its usual mounting function using a metal strip that can slide into grooves separating the bead portion from the flexible wiping edge. The shroud encloses an electrically heated chamber to prevent ice and snow deposits on the shroud.

Abstract: A multiple terminal assembly includes a plurality of connectors secured within a housing in close proximity to and electrically insulated from each other. The terminals include an electroconductive strip extending outwardly from one side of the housing and an electroconductive tab extending outwardly from an opposite side of the housing. The terminals are spaced apart a fixed, predetermined distance along the housing so that when the assembly is used to supply electrical power to a structure having current carrying members extending to a connection area along an edge portion of the structure, each of the terminal strips is aligned with one of the current carrying members at the connection area and each of the tabs is aligned with a corresponding connector of a multiple connector harness assembly.

Abstract: A transparent panel heater which can be used for heating a window portion of liquid crystal displays, refrigerated showcases, freezed showcases, defrosters of windshields, and the like. The panel heater has a transparent substrate, a transparent conductive film formed on the substrate, a substantially light-transmittable metallic electrode-underling-layer formed on the transparent conductive film and a pair of metallic electrodes which are provided for electrifying the conductive film and formed on the electrode-underlying-layer. The transparent conductive film is a laminate of at least one transparent thin layer made of a nitride and/or a carbide and at least one substantially light-transmittable metallic layer. The transparent conductive film and electrode-underlying-layer are preferably formed by a dry process, and the electrodes are preferably formed by a wet plating method.

Abstract: A method for the preparation of glass sheets with a view to laminating them consists of curving the glass sheets by causing them to pass one after another along a curved trajectory, then cooling them by passage between blowing chests, and of dispatching them by batches to the assembling station, and a laminated pane, the sheets of which have, in the central zone, a core compressive stress of from 1 to 50 MPa.

Abstract: A recessed conductive grid formed in the exterior surface of an infra-red transmitting window provides shielding against electromagnetic interference and/or low observability. The recessed conductive grid, with its top surface flush with the exterior surface of the IR-transmitting window, is more resistant to erosion by rain and sand than prior art structures, in which the grid is formed on top of the exterior surface.

Abstract: Safety glass, known to consist of glass panels having an interposed plastic ply to minimize shattering, is converted by the within method into an auto windshield having a wiper deicing function by the application of resistive conductive coatings forming a circuit along the glass panel bottom edges insulated by the plastic ply, which circuit is heat-generating when connected to the auto battery and thus effective to deice the wiper which in an at-rest position is near enough to the heat source to benefit therefrom for the purposes intended.

Abstract: An electrically heated window assembly and method for heating a movable front door window (side lite) of a motor vehicle defrosts and deices the front window by producing a concentration of heat at the portion of the front window through which an operator or passenger of the vehicle views an exterior rear view mirror. To heat the window, a current flows between a first bus bar, positioned along the front edge of the window, and a second bus bar, positioned along the rear edge of the window. A conductive film provides the current path between the respective bus bars. A nonconductive break is formed in the conductive film substantially along the nominal door line of the window to prohibit heating of the window below the nominal door line. The first bus bar may preferably be arcuately-shaped to provide a uniform heating pattern on the window. Various control devices, such as temperature sensors and position sensors, are used to control the heating process.

Abstract: A transparent panel heater which can be used for heating a window portion of liquid crystal displays, refrigerated showcases, freezer showcases, defrosters of windshields, and the like. The panel heater has a transparent substrate, a transparent conductive film formed on the substrate, a substantially light-transmittable metallic thin layer formed on the conductive film and a pair of electrodes for electrifying the conductive film. The metallic thin layer is preferably deposited by a dry process such as a sputtering process, an ion plating method, various CVD methods, and the like. The electrodes are preferably formed on the metallic thin layer by a wet plating method.

Abstract: A window glass comprising at least one sheet of glass coated with an electroconductive ITO layer, pyrolyzed from powdered components, combined with a flexible plastic material of the PVB, PU, PVC type, with an index approaching more the index of the ITO layer than the index of air, with which the said layer is coated, and a sheet of glass dyed in the mass, with the same color as the ITO layer, and with properties of reduced energy transmission also entering advantageously into the composition of the window glass is provided. The invention particularly applies to the production of heated windshields for automobiles.

Abstract: An electrically heatable windshield with a hidden bus bar configuration. A border of opaque ceramic material, preferably a lead borosilicate enamel, is bonded to an interior surface of the transparency about its periphery. Opposing electroconductive bus bars, preferably a low frit content silver-containing ceramic material, are bonded to the ceramic material so that the entire inner edge of the bus bar overlays a portion of the ceramic material and is spaced from the inner edge of the border, providing an intermediate portion of the border between the bus bars and transparency surface that is not covered by the bus bars. An electro-conductive coating is applied to the transparency to interconnect the bus bars and covers to the inner surface of the transparency, the bus bars and the intermediate portion of the ceramic material border so that electric current flowing between the bus bars must flow through the portion of the coating that covers the intermediate portion of the border.

Abstract: An electrically heated cover for wiper blade assemblies includes a cover body having front, rear, right-hand and left-hand end walls and a top wall having a longitudinal access opening for allowing ready connection of the wiper blade assembly to a wiper arm. Electrical resistance heating elements are attached to the inner surface of the cover body and are electrically connected to the vehicle electrical system to provide heat that prevents formation of ice on the wiper blade assembly, the wiper blades and the windshield during severely cold snowy weather. The cover is held in place by a plurality of thumb or set screws through the cover that bear against the wiper blade assembly and are kept from slipping by rubber bushings that contact the wiper blade assembly. The cover can be easily removed and installed and allows completely normal operation of the windshield wipers, and requires no alteration of pre-existing equipment.

Abstract: A method for the preparation of glass sheets with a view to laminating them consists of curving the glass sheets by causing them to pass one after another along a curved trajectory, then cooling them by passage between blowing chests, and of dispatching them by batches to the assembling station, and a laminated pane, the sheets of which have, in the central zone, a core compressive stress of from 1 to 50 MPa.

Abstract: A printing screen, a process of making such a printing screen, and a method of screen printing on hard non-absorbent materials, such as glass, are provided to form a pattern with selected areas of variable thickness. A pattern is formed in the screen utilizing an emulsion coating which has been hardened in the usual manner. A second pattern is formed in a second emulsion coating on a surface of the screen in at least one area of the first pattern. The second emulsion coating is substantially thinner than the first coat and includes a specific dot size and arrangement to achieve additional support, which results in a thinner layer of ceramic ink being deposited when the screen is in use.

Abstract: An arrangement for heating upper and lower windshield wiper blades parked proximate the lower edge of a windshield utilizes an electric heating grid placed against the inside surface of the windshield, substantially in alignment with the parked wiper blades. The electric heating grid is comprised of a first wire in alignment with the lower blade, an intermediate wire and an upper wire in alignment with the upper blade. The wires have opposite ends which are connected to busses that are disposed at the lower edge of the windshield, the busses having leads for connection to power circuitry. The power circuitry includes a climate control system having a switch which is rotatable to a defrost position. When the switch is rotated to the defrost position so that the climate control system defrosts the windshield, current flows through the grid. As long as the switch is in the defrost position, the current continues to flow.

Abstract: Apparatus (10, 50) for removing frozen water from vehicle glass includes a cured, microwave-heatable layer (14, 64). The microwave-heatable layer (14, 64) may be formed from at least one elastomeric gum, a curing catalyst adaptable to cure the gum, and microwave-heatable particulate matter dispersed in the gum. In one embodiment, the apparatus (10) is a mitt including an insulative layer (42) which is positioned to be interposed between an inner surface (27) of the elastomeric pad (14) and the hand, such that the hand does not undergo temperature stress. The mitt (10) also preferably includes a visual marker (30) to indicate the temperature of the elastomeric pad (14).

Abstract: A window defogging system that comprises a power supply and an optically clear overlay includes a sheet of heat-stabilized polyester (13) having a hard coat layer (15) on one surface and an indium tin oxide (ITO) layer (17) on the other surface. The ITO layer (17) is scored around its periphery (19) to create a groove that electrically isolates the edge of the ITO layer from an interior heating zone (23). Additional grooves create electrically isolated regions (26a, 26b, 28a and 28b). Multiple layers of silver are printed atop the ITO layer (17), along opposing edges of the interior (heater) zone (23), to create bus bars (25a, 25b). The bus bars end at terminal regions (29a, 29b) that are connected directly to the power supply. The housing (61) of the power supply is supported by connectors mounted in the optically clear overlay. In some versions of the invention, a dielectric layer (33a, 33b) is located along a portion of the bus bars, between the multiple layers of silver.

Abstract: A glazing unit having incorporated therewith a solar control filter, comprising combinations of layers of transparent films adhered to the surface of a transparent glass sheet. A protective covering is provided over the coating stack. The coating stack includes at least three layers of zinc oxide and at least two layers of silver deposited alternately one upon another, with each layer of silver between two layers of zinc oxide. The glazing unit exhibits color compatibility in environments, where normally employed. The electrically conducting silver layers enable the coating stack to optionally be utilized as a defogging and deicing system for the unit.

Abstract: An air conditioning system suitable for use in an electric vehicle. In the system, an air conditioning mechanism for air-conditioning the driver and passenger room of the vehicle is disposed in the vehicle. A sensor is attached to at least one window or disposed in the vicinity of the window. The sensor outputs a signal for making a decision as to whether or not the window is in a clear state. A glass heating device is used to heat each such window. When it is determined based on the output signal of the sensor that a window is unclear, either iced or foggy, a control device is activated to energize the glass heating device and to output a signal for controlling the power used by the air conditioning mechanism. Thus, water or moisture condensed on the surface of each window or ice formed on the surface thereof can be quickly removed. Further, the total amount of energy to be used by the air conditioning system can be reduced.

Abstract: A laminated glazing is prepared by a providing an electroconductive layer on side 3, the sides of such a glazing being conventionally numbered from 1-4 starting from the outside of the glazing when mounted on a vehicle, towards the inside. The electroconductive layer is formed by powder deposition and pyrolysis to form a ITO layer on a glass pane, which is subsequently bent such that the surface bearing the ITO layer is convex. This glass is laminated with a glass of the same curvature, between which panes is sandwiched a plastic interlayer. On the side of the interlayer facing the electroconductive layer, current lead strips, in the form of metal tinsel, are provided, such that upon lamination, the metal lead strips are in electrical contact with the electroconductive layer and lead to a source of electricity. The resulting window is produced more simply, more reliably, and exhibits improved defogging.

Abstract: The subject of this invention is a method of making a curved glass pane of laminated glass, such as an automobile windshield, in which one of the two single glass sheets is provided, on the surface bearing against an intermediate layer, with a film of a baking finish. The baking finish is applied onto the inner face of the single glass sheet intended for the outside. The glass sheet, provided with the dried baking finish (i.e., a colored film), is laid, with the film upwards, onto the single glass sheet intended for the inside. The pair of glass sheets, in this arrangement, is prebent on a bending frame with simultaneous baking-in of the colored film. Subsequently, the two glass sheets are transposed and, in this transposed arrangement with the colored film on the inside, are finally bent in a second bending operation on a bending frame corresponding to the final shape of the outer sheet.

Abstract: Formed bodies of glass, especially glass panes, are disclosed provided with electrically conductive circuits and with a colored appearance of the circuits upon looking through the glass and a method of their production. A layer of essentially pigments based on inorganic compounds is located between the optionally enamelled formed body of glass and the circuit which layer is connected via adhesive bridges of a vitrifying material to the formed body and to the circuits. The method of production is carried out by the application of a coating material which contains pigments and is free of vitrifying materials onto a formed body and (ii) the application of a conductive paste thereover containing a vitrifying material and (iii) a heat treatment.

Abstract: The conventional sun visor of a vehicle is provided with a fan system including a heater for defrosting and defogging the vehicle windshield. The fan system includes a fan subassembly body mounted in an opening in the sun visor by a retainer subassembly including first and second retainer frames having flanges insertable into the fan subassembly body for securing it in the visor opening. First and second grills are mounted over the faces of the subassembly body by mechanical fasteners which extend through the body and retainer frames. An electric heating element is mounted on at least one of the grills for heating the airstream geneated by the fan of the fan subassembly. The fan and heating element are selectively powered by the vehicle electrical system through an on-off switch.

Abstract: An automobile antenna including a defogging heater wire and a conductor combined into a simple structure to accomplish a good FM reception. A capacitor which effects high-frequency grounding of the terminals of a defogging heater wire is installed between the terminals and a vehicle body; alternately, FM choke coils can be installed which prevents the heater wire from receiving high-frequency signals from a power source of the heater wire. The heater wire which resonates in the FM frequency band but not in the AM frequency band is inductively and capacitively coupled to the conductor which is installed on the surface of the window glass and resonates in the FM frequency band but not in the AM frequency band. The heater wire and conductor are installed in such a positional relationship that a double resonance is created.

Abstract: This invention relates to a laminated glazing pane which may be used as an aircraft windshield. The pane comprises at least two glass sheets connected together by an intermediate layer of polyvinyl butyral and, in its marginal zone, between at least one glass sheet and the intermediate layer, at least one adhesive ring comprising a plastic material which absorbs at least a portion of the stresses to which the pane is subjected during operation.

Abstract: A method for fabricating an electrically heatable coated transparency, particularly useful as a vehicle windshield, is disclosed. The method involves sputtering on a substrate surface layers of metal oxide, metal-containing primer, infrared reflective metal, metal-containing primer and metal oxide to produce an electroconductive coating, and applying first and second bus bars to the substrate in contact with the coating.

Abstract: An laminated article heater terminal assembly and connector for electrically uniting a source of electricity with a conductive polymer film laminated between two nonconductive materials. The terminal assembly includes a conductive metal foil tab and a terminal body further including dimples and first and second foldable shoulders which act in unison to mechanically grasp the conductive metal foil tab. A plurality of terminal assemblies are then captivated in a connector.

Abstract: A method of producing a screen for printing a heating line pattern which comprises the steps of: depositing a first photosensitive emulsion layer on a screen, masking a predetermined portion of the first photosensitive emulsion layer corresponding to a heating line pattern comprising bus bars and heating lines, exposing the first photosensitive emulsion layer except the masked portion to form the first cured emulsion layer, removing the unexposed portion of the first photosensitive emulsion layer to form the permeable portion in the first cured emulsion layer, depositing a second photosensitive emulsion layer at least on the first cured emulsion layer adjacent to the permeable portions corresponding to the bus bars, masking predetermined portions of the second photosensitive emulsion layer on the first cured emulsion layer, exposing the second photosensitive emulsion layer except the masked portions to form a second cured emulsion layer comprised of unmasked exposed portions, and removing the unexposed portio

Abstract: The electrical connections for an electrically heatable windshield are sealed prior to the laminating operation to prevent gas from entering the interior of the windshield through the bus bar leads when the windshield is subjected to the elevated temperatures and pressures of the laminating operation.

Abstract: A method is disclosed for producing superior optically clear laminates having a sheet of semi-rigid material encapsulated in a thermoplastic interlayer between layers of rigid material such as glass. Pre-cooled laminate elements are assembled at reduced temperature, allowing positioning of the sheet of semi-rigid material in the interlayer of the assembly with minimal wrinkling, formation of air bubbles or entrapment of moisture. Thereafter, the laminate assembly is maintained under vacuum for an extended period of time, substantially eliminating wrinkling, air bubbles and moisture from between the laminate elements as well as pre-forming the semi-rigid sheet. Bonding heat and pressure is then applied, first heating the assembly to "tack" the laminate elements together, and next applying heat and pressure for bonding the laminate elements.

Abstract: A terminal connector for a heated window, a heated window provided with a plurality of terminal connectors constructed and arranged for simultaneous engagement to corresponding terminals of a multiple terminal housing and a method of assembling a heated window provided with at least two of said terminal connectors in a terminal connection area along a side edge of said heated window.

Abstract: A glazing unit comprises a substrate ply and a laminating ply laminated to a surface of the substrate ply. A coating on a laminated surface of the substrate ply is a film stack comprising a film of electrically conductive material covered by a film of dielectric material. The film of dielectric material immediately adjacent the laminating ply comprises a layer of silicon dioxide immediately adjacent the laminating ply and a layer of dielectric material of refractive index greater than 1.5 between the silicon dioxide and the conductive material. Applications include, for example, glazing units for solar load reduction and electrically heated glazing units.

Abstract: An external window for infrared radiation is protected from hostile environments by forming a bulk window of gallium arsenide and depositing a protective layer of silicon on the external surface. A grid-like pattern of conductive lines is formed in the silicon layer to provide a heated de-icer and to act as a shield against longer wavelength electromagnetic radiation.

Abstract: An ice melting system for a motor vehicle supplies a heater incorporated in a windshield with electric energy which is generated by a generator that is drivable by an engine on the motor vehicle. A voltage which is obtained by dividing an output voltage from the generator is applied as a control input voltage to a voltage regulator which controls the output voltage of the generator. When the voltage regulator is supplied with a control input voltage which is lower than when a battery on the motor vehicle is charged, the voltage regulator increases a current supplied to a field coil of the generator, thus enabling the generator to increase the output voltage thereof. Therefore, the heater is supplied with a larger amount of electric energy to melt ice on the windshield efficiently.

Abstract: A system for heating the passenger compartment of an automotive vehicle has a hot water heater receiving heat from a vehicle engine arranged in series with a self-regulating electrical resistance heater of positive temperature coefficient of resistivity, has a power source for energizing the electrical resistance heater, and has a fan for directing air in heat-transfer relation to the hot water heater and to the electrical resistance heater in sequence to provide a heated air output to the passenger compartment. Fan speed is controlled to regulate the volume of air directed in heat-transfer relation to the heaters so that the electrical resistance heater is promptly and consistently capable of heating that volume of air to at least a selected minimum temperature such as 100.degree. F. as the heated air output is furnished to the passenger compartment, thereby to give a vehicle passenger an immediate and continuing sensation of comfort beginning very promptly after engine start-up even on a very cold day.

Abstract: A circuit arrangement for a motor vehicle headlight including a reflector and/or a lens, a light source coupled to a voltage providing device (W), at least one electrically conductive heating element (H) mounted on or in an enclosing light-transmissive shield coupled to the voltage source, and a switching-on apparatus (E) for the heating element will, in addition to avoiding a coating and ice build-up, in an uncomplicated and cost effective manner provide a dependable, security-increasing, crack monitoring of the light transmissive shield in that the heating element is electrically coupled with an analyzing apparatus (A) which includes a light-transmissive-shield, crack-monitoring device formed as a current or voltage measuring device.

Abstract: An electrical resistance heated window having at least three heatable zones and at least one of the heatable zones is generally centrally located on the window and can be heated faster to a higher temperature than the other of the zones for faster defogging and deicing of that particular zone.

Abstract: An electrical control system for an electrically heated window in a motor vehicle has a voltage source including a generator, a voltage regulator for regulating a generator output voltage, a transformer switched between the generator and a heating window, the generator output voltage being increased before supplying to the heatable window, and a unit for measuring a temperature of the transformer and interrupting a communication between the transformer and the voltage source in the event of exceeding an adjustable limiting temperature.

Abstract: An electric heating device for heating and deicing the wiper rest zone of a vehicle windshield includes a resistance heating wire of either circular or rectangular cross-section attached to the exterior surface of the windshield along the lower edge thereof and outside the normal range of vision therethrough by means of an electrically non-conductive tape extending lengthwise of the wire. An arcuate or trapezoidal cross-section layer of electrically non-conductive sealant completely covers the tap and wire to provide water tight encapsulation thereof. The adhesive tape may be 4 provided with holes to allow the sealant to penetrate therethrough and form a mechanical interlock between the tape and windshield. The wiper blade is adapted to contact the sealant layer. The device may also be applied to the lower edge of the rear or side windows of a vehicle to melt ice or snow which may accumulate thereat.

Abstract: The device for energizing a heating element of a window pane from a direct current network of a motor vehicle includes a converting device for converting the d.c. voltage of the direct current network into an alternating current voltage of a predetermined frequency and a resonant circuit connected to the output of the converting device having a Q-factor high enough to produce a low number of harmonics in operation. The resonant circuit has a resonant frequency corresponding to that of the alternating current voltage. The heating element is a part of a resistance of the resonant circuit. The converting device can include a control circuit for producing alternating control signals, a base driving circuit controlled by the control signals and having two outputs connected respectively to a base of a switching transistor. The device can also include a protecting circuit for picking up energy during opening of the respective switching transistors and returning the picked-up energy to the d.c. network.