JP7496374B2 - Electric air heating device having a clamping device including an integral fuse, engine and vehicle including an electric air heating device - Google Patents

Description

The invention relates to an electric air heating device for diesel engines with a clamping device, in particular a screw connection, including an integrated protective fuse. The invention also relates to a diesel engine with an electric air heating device having at least one clamping device including an integrated protective fuse, and to a vehicle including an electric air heating device.

In this context, the expressions "fuse" and "thermal fuse" mean and intend an element of an electrical circuit that is designed to interrupt electrical current in an electrical circuit including said "fuse" element upon overheating of said "fuse" element, said "fuse" element comprising a piece of heat-fusible solid material that closes the electrical circuit in a first solid conductive form in which electrical current can flow in the electrical circuit, and that opens the electrical circuit in a second solid non-conductive form in which no electrical current can flow in the electrical circuit caused by overheating of the first solid conductive form.

To facilitate starting of a diesel engine, it is desirable to heat the air flow entering the diesel engine. For this purpose, an electric air heating device may be accommodated in the intake manifold of the diesel engine. In general, such an electric air heating device includes a housing adapted to pass the air flow to be heated within the interior volume of the housing, and also includes at least one resistive ribbon arranged within the interior volume of the housing, which is capable of heating the air flow to be heated within the interior volume of the housing that accommodates the resistive ribbon. When an electric current flows through the resistive ribbon, the temperature of the resistive ribbon increases by the Joule effect, and heat is transferred from the resistive ribbon to the air of the air flow in contact with the resistive ribbon, providing a hot air flow to the engine. However, if the resistive ribbon is heated and no air flows within the interior volume of the housing, the temperature of the resistive ribbon increases and the corresponding heat is transferred to the housing and the air heating device. As a result, the housing of the electric air heating device is overheated by the electric current that operates the electric air heating device fixed to the intake manifold of the diesel engine. There is a risk that some components of the engine extending near the housing of the electric air heating device will melt or catch fire due to the heating of the housing. This is the case if the engine cannot run, if air does not flow through the internal volume of the housing of the electric heater, and if the control system of the air heating device malfunctions and the air heating device remains in the operating mode. The control system allows the heater to function normally even before the engine starts, and the air heating device to function even after the engine has stopped running due to a malfunction of the control system. Then, the components of the air heating device, including the housing, heat up due to insufficient heat dissipation from the heating element of the air heating device. When the housing reaches an excessive temperature due to some improper operation, the components of the air heating device, including the housing, start to burn or melt. Components near the air heating device, the vehicle or the machine, catch fire and/or melt. This problem becomes more important when the vehicle or machine is in an enclosed space in a garage or on a ship.

A solution is needed to prevent overheating of the air heating device and the housing of the air heating device, especially above 200°C.

The document 1 discloses an air heating device including a housing containing two resistance ribbons fixed to the housing by clamping screws, one of which is a clamping screw incorporating a fuse. The shaft of the clamping screw incorporating the fuse has a longitudinal portion that communicates with a bore formed in the housing's outer casing, said longitudinal portion being electrically insulated from the housing's outer casing. The fuse has a longitudinally extending coaxial tube having the same longitudinal axis as the shaft of the clamping screw, one end of which is electrically connected to the housing and one end of which is electrically connected to a conductive washer that contacts the shaft. The clamping screw incorporating the fuse also has a tube of electrically insulating material (forming an insulating spacer) radially sandwiched between the shaft of the clamping screw and the fuse, said tube of electrically insulating material being free to move in the axial direction of the screw shaft. The fuse is thus electrically insulated radially from the shaft of the clamping screw, and a closed electrical circuit is established between the resistance ribbons and the housing, said electrical circuit including the shaft of the clamping screw, the conductive washer and the fuse, electrically connected in series.

However, the tightening screw incorporating the fuse of Patent Document 1 has several drawbacks. When the temperature of the housing rises and the temperature of the fuse fixed to the housing reaches a value higher than the melting temperature of the fuse material, the fuse melts. As a result, the pretension force applied between the housing and the nut of the tightening screw becomes zero, and the air heating device may fall. Parts of the air heating device may fall into the combustion chamber of the engine, causing serious damage to the engine.

US Patent Application Publication No. 2014/159855

The present invention aims to overcome these shortcomings.

The present invention aims to provide a robust solution that overcomes these shortcomings.

The present invention aims to provide a fixed electric air heating device having a clamping device that includes an integral fuse.

The present invention aims to provide an electric air heating device having a clamping device that includes an integral fuse that clearly maintains its clamping strength after the fuse material melts.

The present invention aims to provide a stationary electric air heating device having a clamping device with an integral fuse that is simple to manufacture, and the clamping device with an integral fuse is easily installed within the electric air heater.

The present invention aims to provide an electric air heating device that can be assembled from a small number of components and is simple to manufacture.

The present invention aims to provide a stationary electric air heating device having a clamping device including an integral fuse that has low manufacturing costs.

The present invention aims to provide a fixed screw connection with an integral fuse that limits the time required to assemble an electric air heating device.

The present invention aims to provide a fixed electric air heating device having a clamping device including an integral fuse that can maintain the assembly of the electric air heating device even after the fixed clamping device fuse melts.

The present invention aims to provide a fixed fastening device that includes an integrated fuse that can be precisely manufactured.

The present invention aims to provide a diesel machine and an electric air heating device having a fixed clamping device including an integral fuse located in the engine compartment of the machine, particularly the diesel machine, that is inexpensive, robust and able to withstand harsh vibration profiles.

The present invention aims to provide an electric air heating device that solves the problem of the decrease in clamping strength after the fuse melts, as described in Patent Document 1.

The present invention aims to provide an electric air heating device that solves the problem of decomposition of solid elements of the electric air heating device after melting of the fuse of Patent Document 1.

The present invention aims to provide an electric air heating device that maintains its clamping strength after the fuse melts.

The present invention aims to provide an electric air heating device that limits, if not avoids, the risk of dispersion of the elements of the electric air heating device within the vehicle engine.

The present invention aims to provide an electric air heating device that limits, if not avoids, the risk of damaging a vehicle's engine.

The present invention aims to provide an electric air heating device that can control the temperature of the electric air heating device and protect the electric air heating device and the environment surrounding the electric air heating device from the risk of overheating and fire.

The present invention relates to
a housing defined by a wall having an inner surface and an outer surface;
at least one resistive ribbon disposed within the housing interior space adapted to heat air in an airflow passing through the housing to form a heated airflow;
a fastening device engaging the inner and outer surfaces of the wall to secure the resistance ribbon to the wall,
a clamping shaft extending across the wall;
a clamping device including at least a clamping washer of the clamping device facing the outer surface of the wall and in conductive contact with the clamping shaft;
a cut-off for opening an electrical circuit supplying current to the at least one resistive ribbon and ceasing heating of the at least one resistive ribbon in a condition of the electric air heating device where the temperature of the wall exceeds a predetermined temperature (referred to as an overheating condition);
11. An electric air heating apparatus of the type in which the cutoff includes a fuse disposed in conductive contact with the clamp washer and the wall,
The fastening device comprises:
clamped longitudinally between the clamp washer and the wall;
clamping said resistive ribbon and said wall together at least in said heated state;
The electrical air heating device comprises at least one clamping spacer which does not provide electrical contact between the clamping washer and the wall.

The invention relates to an electric air heating device comprising at least one electric resistance ribbon for heating the air of an air flow, which is protected against overheating, in particular when the air flow is interrupted and when the temperature of the wall of the housing rises dangerously. In that case, the electrical supply of the resistance ribbon is interrupted by melting the fuse. The resistance ribbon remains securely fixed to the wall of the housing in the inner space of the housing. There is no risk of parts of the electric air heating device coming apart and falling into the engine compartment and/or into the combustion chamber of the engine, causing damage to the engine. Moreover, to repair an electric air heating device according to the invention, it is sufficient to replace the fuse without replacing the entire electric air heating device.

The electric air heating device according to the invention includes a cut-off (called the first clamping device) integrated into the clamping device. The first clamping device is arranged to fix the at least one resistive ribbon to the wall of the housing and to electrically connect the at least one resistive ribbon to the negative (-) terminal of the accumulator battery. In a preferred embodiment of the electric air heating device according to the invention, the first clamping device is connected to the negative (-) terminal of the accumulator battery through the wall of the housing.

The clamping spacer is selected and adapted to enable the at least one resistive ribbon to be clamped to the wall of the housing both in an operating condition of the electric air heating device in which the fuse is in electrical contact with both the clamping washer and the wall of the housing, and in an overheated condition of the electric air heating device in which the material forming the fuse melts and interrupts the electrical circuit between the clamping washer and the housing.

The cut-off of the electric air heating device is adapted to open the electrical circuit in the overheated condition and to keep the electrical circuit open when the temperature of the wall of the housing falls below a predetermined temperature.

The fuse of the electric air heating device extends outside the housing and is mounted in series within the electrical circuit.

In some preferred embodiments of the electric air heating device according to the invention, the fuse is a tubular fuse that extends coaxially with the clamping shaft.

The electric air heating device according to the present invention includes a second clamping device, separate from the first clamping device, for fixing the at least one resistive ribbon to the housing and electrically connecting the at least one resistive ribbon to the positive (+) terminal of the storage battery so that a closed electrical circuit is formed, and current flows from the storage battery through the second clamping device, then through the at least one resistive ribbon, then through the first clamping device, then through the housing and back to the storage battery.

Advantageously, according to the invention, the current flows through the clamping shaft of the clamping device, from the inner end of the clamping shaft where the clamping device secures the resistance ribbon, to the outer end of the clamping shaft, the outer end associated with the cutoff, and to the clamping nut.

In some preferred embodiments of the electric air heating device according to the invention, the resistive ribbons are connected in series in the electrical circuit.

The clamping spacer of the electric air heating device according to the invention is selected and arranged so that the current flows from the resistive ribbon fixed to the first clamping device, through the clamping shaft of the first clamping device, then through the clamping washer, then through the fuse and back to the wall of the housing. The clamping spacer of the electric air heating device according to the invention is selected and arranged so as to avoid direct electrical contact between the clamping shaft and the wall of the housing. The clamping spacer of the electric air heating device is selected and arranged so as to keep the resistive ribbons clamped to each other against the wall of the housing even in the overheated state. Advantageously, the clamping spacer is a tube extending coaxially with respect to the clamping shaft.

In some preferred embodiments of the electric air heating device according to the invention, the clamping spacer is made of at least one non-melting material. The melting temperature of the material of the clamping spacer is higher than the melting temperature of the material of the fuse. Advantageously, the clamping spacer may be made of at least one metal selected from the group consisting of copper, aluminum, titanium, iron, zinc, beryllium, magnesium, silver, gold, lead. Advantageously, the clamping spacer may be made of at least one material selected from the group consisting of metal alloys, silicon bronze, inconel, brass, amalgam and aluminum alloys. The clamping spacer may be made of a ceramic material or a rigid rubber material or other plastic. The clamping spacer may be made of a metallic material wrapped with a surface layer of at least one insulating material. The clamping spacer of the electric air heating device according to the invention is selected and arranged to mechanically withstand the longitudinal compressive strength provided by the first clamping device.

In some embodiments of the electric air heating device according to the present invention, the clamping spacer is a tubular clamping spacer that extends coaxially with the clamping shaft and is in close contact with the clamping shaft.

In some embodiments of the electric air heating device according to the invention, the at least one clamping spacer comprises at least one tube made of a non-melting metallic material adapted to clamp the at least one resistive ribbon on the wall in the overheated state of the electric air heating device;
The fuse includes, and is formed, among other things, from a tube made of a non-molten metallic material extending radially between the fuse and the clamping shaft, and at least one insulator (called an L-shaped or U-shaped insulator (longitudinal section)) formed to extend longitudinally between the clamping washer and at least one of the walls of the housing, radially insulating the at least one tube made of a non-molten metallic material from the wall of the housing.

In some embodiments of the electric air heating device according to the invention, the at least one tube made of a non-molten metallic material and the at least one tubular insulator extend coaxially about the clamping shaft.

In some preferred embodiments of the electric air heating device according to the invention, the clamping spacer comprises:
at least one metal tube made of a non-melting material adapted to clamp said at least one resistive ribbon to said wall in said overheated state of said electric air heating device;
at least one tubular insulator made of a non-meltable material and electrically insulating said at least one metal tube from said fuse in a radial direction;
a ring extending longitudinally between said wall and said at least one metal tube made of a non-melting material and electrically insulating said at least one metal tube made of said non-melting material longitudinally from said wall, and

The melting temperature of the material forming the fuse is lower than the melting temperature of the material forming the clamping spacer. The melting temperature of the material forming the fuse is lower than the melting temperature of the non-melting material of the metal tube.

The material forming the fuse may be selected from the group consisting of metal alloys, brass, aluminum/zinc alloys, magnesium/zinc alloys, magnesium/aluminum alloys, silicon/magnesium alloys, tin/zinc alloys, and lead/zinc alloys. Other materials are possible. The material forming the fuse is selected to suit the desired predetermined temperature.

The material forming the metal tube may be selected from the group consisting of metals and metal alloys. The material forming the metal tube may be selected from the group consisting of copper, aluminum, titanium, iron, zinc, beryllium, magnesium, silver, gold, lead, and alloys thereof in acceptable proportions (such as, for example, silicon bronze, inconel, brass, and amalgams). Thus, the melting temperature of the fuse can be adapted to various air heating devices.

In some preferred embodiments of the electric air heating device according to the invention, the clamping washer, the fuse, the at least one metal tube made of a non-melting material, and the at least one tubular insulator extend coaxially about the clamping shaft.

In some preferred embodiments of the electric air heating device according to the invention, the cut-off comprises a ring made of an electrically insulating material having high compressive strength and extending longitudinally between the wall of the housing and the clamping spacer, in particular between the wall of the housing and at least one of the at least one metal tube and the at least one tubular insulator made of a non-melting material.

In some preferred embodiments of the electric air heating device according to the invention, the ring is made of a material having sufficient compressibility, high heat resistance and low electrical conductivity. In some preferred embodiments of the electric air heating device according to the invention, the ring is made of at least one material selected from the group consisting of ceramics, polymeric materials having high compressive strength, high heat resistance and low electrical conductivity, and mica.

In some preferred embodiments and in accordance with the present invention, the electric air heating device includes a cover that encases the exterior of the clamping device to collect the molten material of the fuse wherever the clamping device is located so that the molten material of the fuse is captured within the protective cover.

In some preferred embodiments of the electric air heating device according to the invention, the clamping washer is selected from the group consisting of a flat washer and a spring washer. However, the clamping device may also include at least one additional washer selected from the group consisting of a flat washer, a fender washer, a Belleville washer, a curved washer and a spring washer.

In some preferred embodiments of the electric air heating device according to the invention, the clamping washer may be a washer made of steel or a washer made of stainless steel.

In some preferred embodiments of the electric air heating device according to the invention, the clamping device includes a screw and at least one nut that cooperates with a threaded portion of the conductive shaft of the screw to secure the resistive ribbon to the wall of the housing. The threaded shaft of the screw and at least one nut may be arranged to apply a clamping force to a head end of the screw that extends to the inner surface of the wall of the housing.

In some other embodiments of the electric air heating device according to the invention, the fastening device includes a rivet that fastens the resistive ribbon to the wall of the housing.

In some preferred embodiments of the electric air heating device according to the invention, the clamping shaft of the clamping device is arranged to extend across a bore formed in the wall of the housing. The clamping shaft is arranged to be coaxially arranged in the bore and electrically insulated from the inner wall of the bore. The clamping device is arranged to electrically insulate the resistive ribbon from the inner surface of the wall of the housing and to connect the resistive ribbon to the positive pole of a remote external battery. The clamping shaft crosses the wall of the housing, is electrically insulated with respect to the bore, is fixed without contact with the bore and the wall of the housing, one longitudinal (inner) end of the clamping shaft is electrically connected to one of the resistive ribbons, and the other longitudinal (outer) end of the clamping shaft includes the cut-off.

The invention also extends to an engine, particularly a diesel engine, comprising at least one electric air heating device according to the invention. The invention also extends to an engine, particularly a diesel engine, in which at least one electric air heating device according to the invention is sandwiched within the air intake manifold of the engine.

The invention also extends to a machine (particularly a vehicle) comprising an engine (particularly a diesel engine) according to the invention. The invention also extends to a machine (particularly a vehicle) provided with an electric air heating device fixed in the engine compartment of the machine. The invention also extends to a machine (particularly a vehicle) comprising an electric air heating device fixed in the engine compartment of the machine (particularly the vehicle).

The present invention further relates to an electric air heating device, a diesel engine equipped with said electric air heating device, and a vehicle including said electric air heating device, characterized by all or some of the features specified above or below, in combination or individually. Regardless of the formal expression provided, unless otherwise specified, the features specified above or below should not be considered to be closely or inseparably related to each other, and the present invention can relate to only one of these structural or functional features, or only some of these structural or functional features, or only a part of one of these structural or functional features, or even to any group, combination, or juxtaposition of all or some of these structural or functional features.

Further objects, features and advantages of the present invention will become apparent from the following description, given by way of non-limiting examples of some of its possible embodiments, taken in conjunction with the accompanying drawings.

1 is a cross-sectional view of a clamping device having an integral thermal cutoff of an air heating device according to a first particular embodiment of the present invention; FIG. 13 is a cross-sectional view of a clamping device having an integral thermal cutoff of an air heating device according to a second particular embodiment of the present invention. 3 is a cross-sectional view of a clamping device including an integral thermal cutoff of an air heating device according to the embodiment shown in FIG. 2, showing an overheating condition of the air heating device. 4 is a perspective view of a detail of a clamping device fixed to the housing of the air heating device according to the invention; FIG. FIG. 2 is an exploded cross-sectional view of a detail of an electric air heating device having a clamping device with an integrated thermal cutoff according to a first particular embodiment of the present invention; 1 is an overall perspective view of an air heating device according to an embodiment of the present invention; FIG. 2 is a perspective view of a detail of an air heating device according to an embodiment of the present invention;

The object of the present invention is to provide a simple, inexpensive and robust solution to prevent overheating of air heating devices.

1 and 2 respectively show cross-sectional views of details of a clamping device 5 with an integrated cut-off 6 including a fuse 10 of a first and second specific embodiment of an electric air heating device 1 according to the invention. In FIGS. 1 and 2, the fuse 10 has not yet been exposed to a temperature higher than the melting temperature of the material forming said fuse 10, the electric circuit is closed and the electric air heating device is in an operating state. The clamping device 5 with an integrated electric cut-off 6 is fixed to the housing 2 and has an axis 9 extending longitudinally in a bore 21 made in the housing 2 and transverse to the housing 2. The clamping device 5 fixed to the housing 2 has a screw 22 with a threaded axis 23 which is associated with a nut 24 for fixing the heating ribbon 3 to the housing 2. The headed longitudinal end of the screw 22 forms an electrically conductive contact with the longitudinal end of the heating ribbon 3 extending into the inner space 4 of the housing 2, said longitudinal end of the heating ribbon 3 forming a washer having a central hole which is associated with the head of the screw 22. The conductive washer 18 is sandwiched between the washer-shaped longitudinal end of the heating ribbon 3 and a washer 19 made of an electrically insulating material (for example made of mica), said mica washer 19 being in contact with the housing 2 and electrically insulating the heating ribbon 3, the conductive washer 18 and the screw 22 from the housing 2. The thickness of the conductive washer 18 is selected to improve the electrical conductivity between the heating ribbon 3 and the shaft 9. The clamping device 5 has an O-ring seal 20 arranged in a countersink 43 formed in the inner end of the bore 21 and adapted to prevent air leakage from the bore 21. The O-ring seal 20 is also adapted to maintain the screw 22 in the proper position, and the shaft 9, 23 are axially centered in the bore 21 to prevent conductive contact with the walls of the bore 21. The clamping device 5 is arranged so that an electrical circuit is necessarily established through the cutoff 6.

However, according to the present invention, the fastening device 5 may be a rivet that secures the heater ribbon 3 to the housing 2.

The cutoff 6 incorporated in the clamping device 5 is a cutoff that opens an electrical circuit when the temperature of the electric air heating device and/or the housing 2 exceeds the melting temperature of the material that constitutes the fuse 10.

In the first and second specific embodiments depicted in Figures 1 and 2, the fuse 10 is a tubular fuse. However, the fuse 10 may be formed differently. The fuse 10 may be made of various materials. Advantageously, the material of the fuse 10 is selected to adjust the melting temperature so that the thermal cutoff is adaptable to various electric air heating devices 1. The fuse 10 is made of an alloy material having a melting temperature adapted to the operating conditions of the electric air heating device 1.

In the particular first and second embodiments represented in Figures 1 and 2, the clamping device 5 also includes a cover 15 fixed to the shaft 23 of the screw 22. The cover 15 may be made of a plastic material. The cover 15 cooperates with the outer surface 7 of the housing 2 to prevent the clamping device 5 from receiving dirt from the engine and also to catch the fuse material on the cover 15 so as not to disperse it in the engine compartment. The cover 15 comprises means for fixing said cover 15 to the shaft 23 of the clamping device 5 and to the air heating device 1, and
a first wedge washer 26 sandwiched between the nut 24 and the cover and sized to accommodate the position of the cover 15 relative to the housing 2;
A spring washer 28 and a second washer 27 which cooperates with a nut 42 to secure the cover 15 to the air heating device 1 .

The cut-off 6 of the first particular embodiment of the electric air heating device 1 according to the invention shown in FIG. 1 comprises as a clamping element:
a screw 22 which cooperates with a nut 24 to secure the heating ribbon 3 to the inner surface 13 of the housing 2;
a clamping spacer 46 forming a tube extending coaxially with the axes 9, 23 and disposed in abutment with the bottom 25 of the counterbore 17 formed in the bore 21;
a clamp washer 8 adapted to transmit the compressive strength provided by a nut 24 associated with the threaded shaft 23 to a clamp spacer 46;
a spring washer 16 arranged to resiliently press the clamping washer 8 against the clamping tube 11 and prevent automatic unwinding of the nut 24;
including.
The clamping spacer 46 is made of a material having high compressive strength and high electrical insulating properties, preferably a ceramic material. The clamping spacer 46 is selected to withstand high clamping torques. The clamping spacer 46 extends radially inward adjacent the shafts 9, 23 and outward adjacent the fuse 10, and is longitudinally dimensioned to transmit the compressive strength provided by the nut 24 in communication with the threaded shaft 23 of the screw 22 to the heating ribbon 3 and secure the heating ribbon 3 to the outer surface 13 of the housing 2.

The fuse 10 and clamping spacer 46 are selected and dimensioned such that when the clamping device 5 is clamped to the housing 2, the fuse 10 is first compressed between the clamping washer 8 and the housing 2 to form an electrical contact for electrical current, and the clamping spacer 46 is then compressed between the clamping washer 8 and the bottom 25 of the countersunk 17 formed in the bore 21 of the housing 2.

The cutoff 6 is a conductive/insulating element having
A conductive shaft 9, 23 of the screw 22;
an electrically conductive clamp washer 8 dimensioned to be in electrical contact with the shaft 9, 23 of the clamping device 5;
a fuse 10 extending longitudinally between the clamp washer 8 and the outer surface 7 of the housing 2 and facing radially toward the outer surface of the clamp spacer 46;
A clamping spacer 46 is provided radially sandwiched between the conductive shaft 9, 23 of the screw 22 and the conductive fuse 10.

The clamping spacer 46 is selected, sized and positioned to prevent any direct conductive contact between the shafts 9, 23 of the screws 22 and the housing 2. The clamping spacer 46 is selected and positioned so that the current flowing through the heating ribbon 3 must necessarily flow through the fuse 10 to reach the grounded housing 2.

However, according to the invention, the integrated clamping spacer 46 may also be made up of several elements. Figure 2 shows a cross-sectional view of a detail of a clamping device 5 with an integrated cut-off 6 including a fuse 10 of a second particular embodiment of an electric air heating device 1 according to the invention.

The cut-off 6 of the second particular embodiment of the electric air heating device 1 according to the invention shown in FIG. 2 comprises as a clamping element:
a screw 22 which cooperates with a nut 24 to secure the heating ribbon 3 to the inner surface 13 of the housing 2;
a ring 14 forming a thick washer extending coaxially with the shaft 9, 23 and arranged to abut against the bottom 25 of a counterbore 17 formed in the bore 21;
a clamping tube 11 extending radially adjacent to and coaxial with the axis 9, 23;
a tubular insulator 12 extending longitudinally between the ring 14 and the clamping washer 8 and capable of associating with the clamping tube 11 in the transmission of compressive strength;
a clamping washer 8 adapted to transmit to the clamping tube 11 the compressive strength provided by a nut 24 associated with the threaded shaft 23;
and a spring washer 16 arranged to elastically press the clamping washer 8 against the clamping tube 11 and prevent the nut 24 from automatically unwinding.
The ring 14 is made of a material having high compressive strength and high electrical insulating properties, preferably a ceramic material, with the ring 14 made of a material having high compressive strength adapted to withstand high tightening torques.
The clamping tube 11 is dimensioned to transfer compressive strength provided by a nut 24 that interfaces with the threaded shaft 23 of the screw 22 to the heating ribbon 3 and secure the heating ribbon 3 to the outer surface 13 of the housing 2, and in a preferred embodiment, the clamping tube 11 is made of a metallic material, and the clamping tube 11 may also be made of a metal or metal alloy.
In a preferred embodiment, the tubular insulation 12 is made from at least one polymeric insulating material.

The fuse 10 and clamping tube 11 are selected and dimensioned so that when the clamping device 5 is clamped to the housing 2, the fuse 10 is first compressed between the clamping washer 8 and the housing 2 to form an electrical contact for electrical current, and further clamps and compresses the clamping tube 11.

The cutoff 6 is a conductive/insulating element having
A conductive shaft 9, 23 of the screw 22;
an electrically conductive clamp washer 8 dimensioned to be in electrical contact with the shaft 9, 23 of the clamping device 5;
a fuse 10 extending longitudinally between the clamp washer 8 and the outer surface 7 of the housing 2 and radially facing the outer surface of a tubular insulator 12;
An electrical insulating ring 14;
The conductive fuse 10 has a clamping tube 11 and a tubular insulator 12 sandwiched between the clamping tube 11 and the conductive fuse 10 and extending radially therefrom.

However, the tubular insulator 12 and the electrical insulation ring 14 may be formed from the same material. Also, the tubular insulator 12 and the electrical insulation ring 14 may be integrally formed from a single material.

The electrical insulating ring 14 and the tubular insulator 12 are selected and positioned to prevent any direct conductive contact between the shafts 9, 23 of the screws 22 and the housing 2. The electrical insulating ring 14 and the tubular insulator 12 are selected and positioned so that any current flowing through the heating ribbon 3 must necessarily flow through the fuse 10 to the grounded housing 2.

Figure 3 shows a cross-sectional view of a detail of the clamping device 5 with an integral cut-off 6 of a particular embodiment of an electric air heating device 1 according to the invention. In Figure 3, due to overheating of the electric air heating device and the housing 2, the fuse 10 is exposed to a temperature higher than the melting temperature of the material forming the fuse, resulting in the fuse 10 melting. When melting, the hot molten material that constitutes the fuse flows out, eliminating the contact between the clamping washer 8 and the housing 2, and then solidifies. Most of the material that constitutes the fuse, especially most of the alloy, remains trapped within the cover 15.

Since the material constituting the fuse 10 does not form an electrical contact between the clamping washer 8 and the outer surface 7 of the housing 2, the electrical circuit including the heating ribbon 3 is opened and the electric air heating device is switched in the inoperative state. However, even when the electric air heating device 1 is in the inoperative state, the compressive strength provided by the screw 22 in conjunction with the spring washer 16 is retained after melting by the clamping tube 11 extending longitudinally between the clamping washer 8 and the ring 14. The clamping device 5 continues to withstand the vibrations provided by the engine during operation and no part of the electric air heating device disintegrates and falls in the engine compartment. Furthermore, the fuse material remains trapped in the cover 15 in any orientation of the electric air heating device 1. Replacement of the fuse 10 is possible by removing the cover 15, loosening the nut 15, taking out the spring washer 16, the clamping washer 8 and the deformed fuse material and replacing it with a new fuse. This replacement avoids replacing the entire electric air heating device.

In the detail of the electric air heating device according to the invention shown in FIG. 4, the cover is not shown and the housing 2 shows a bore 21 adapted to receive a clamping device 5 (called clamping device (+)) that crosses the housing 2 and is connected to the positive (+) terminal of an accumulator (not shown). The electric air heating device shown in FIG. 4 has a clamping device 5 including an integral cut-off 6. In the electric air heating device shown in FIG. 4, the cover 15 has been removed. The clamping device 5 includes a screw with a threaded shaft 23 that crosses a bore formed in the housing 2. The heating ribbon 3 is fixed in the inner space 4 of the housing 2 in such a way that the heating ribbon 3 is electrically connected to the shaft 9 of the screw and electrically insulated from the housing 2. For this purpose, the clamping device 5 includes an electrically conductive washer 18 sandwiched between the washer-shaped longitudinal end of the heating ribbon 3 (which increases the electrical contact surface between the heating ribbon 3 and the shaft of the screw and improves the electrical conductivity between the heating ribbon 3 and the shaft) and a washer 19 made of an electrically insulating material (for example made of mica), which is in contact with the housing 2 and electrically insulates the heating ribbon 3 from the inner surface 13 of the housing 2.

The clamping device 5 shown in FIG. 4 shows a fuse 10 of conductive material in contact with the housing 2 at one longitudinal end and in contact with and extending between the clamping washer 8 at its opposite longitudinal end and maintained in longitudinal compression by a screw that interfaces with a nut 24 and a spring washer 16.

The electric air heating device shown in longitudinal section in FIG. 5 represents a clamping device 5 with an integral cut-off 6 containing a fuse 10. The clamping device 5 is fixed to the housing 2 and communicates with a bore 21 formed in the housing 2. The bore 21 has a counterbore 17 at its outer end and a countersink 43 at its inner end. The counterbore 17 forms an abutment that receives the shaft 9 of the screw 22, the fuse 10, the clamping washer 8, the clamping tube 11, and the ring 14 extending axially with the tubular insulator 12. In the clamping device 5, the clamping tube 11 and the shaft 9 of the screw 22 are electrically insulated radially by the insulator 12 and longitudinally by the ring 14, so that the current necessarily passes from the heating ribbon 3 through the shaft 9, the clamping washer 8, the fuse 10 to the outer surface 7 of the housing 2.

Figure 6 shows an electric air heating device 1 with a clamping device 5 according to a particular embodiment of the present invention having an integral thermal cutoff 6 including a fuse tube 10.

Typically, the electric air heating device 1 is sandwiched within an air intake manifold that is fixed within the engine compartment of the diesel machine. As a result, if the electric air heating device overheats, and in particular if the housing of the electric air heating device overheats, it is necessary to discontinue the electrical supply to the electric air heating device 1 before the electric air heating device or the components surrounding the electric air heating device (e.g. air filters, hoses...) begin to deteriorate.

The present invention therefore relates to an electric air heating device in which power to the heating ribbon is cut off if the housing overheats, limiting the risk that vibrations provided by a running engine could cause components of the air heating device to break off and fall into the engine's combustion chamber, causing damage to the engine.

One of the main advantages is that the longitudinal clamping force applied by the clamping device 5 is maintained, including after melting of the constituent material of the fuse tube 10 following overheating of the housing 2 causing melting. In this case, the operation of the electric air heating device 1 is interrupted by opening the electrical supply circuit of the heating ribbon 3 of the electric air heating device 1. However, the clamping device 5 and the components of the electric air heating device 1 are held together by the clamping force applied by the clamping device 5, and there is no risk of the motor being damaged, despite the vibrations provided by the operating motor and possibly the air flow.

In the embodiment shown in FIG. 6, the electric air heating device 1 comprises four clamping devices 5 which cross the housing 2 through a bore 21 made in the housing and fix the heating ribbon 3 to the housing 2. One of the clamping devices 5 is called clamping device (+) 30 and is connected to the positive (+) terminal of a storage battery (not shown) constituting the vehicle's power source. The clamping device (+) 30, which includes an integrated cut-off 6, is attached to the top of the electric air heating device 1. The clamping device (+) 30 crosses the housing 2 through a transverse bore made in the housing 2 of the electric air heating device 1. The clamping device (+) 30 is electrically insulated from the inner wall of the bore through the housing 2 and is connected to one longitudinal end of a first heating ribbon 31 extending into the inner space 4 of the housing 2, so that an electric current flows through the first heating ribbon 31 to the second longitudinal end 32 of the first heating ribbon 31. The second longitudinal end 32 of the first heating ribbon 31 is fixed to the housing 2 by a second clamping device 33 that crosses the housing 2 and is electrically insulated from the housing 2. The electric air heating device 1 shown in Fig. 6 comprises a second heating ribbon 34 having a first longitudinal end 36 fixed to the housing 2 by a third clamping device 35. The second clamping device 33 and the third clamping device 35 comprise a plate 37 of electrically insulating material that insulates the second clamping device 33, the second longitudinal end 32 of the first heating ribbon 31, the first longitudinal end 36 of the second heating ribbon 34 and the third clamping device 35 from the housing 2. The second clamping device 33 and the third clamping device 35 also comprise a bridge 38 made of an electrically conductive material 36 and electrically connecting the first heating ribbon 31 and the second heating ribbon 34. The second longitudinal end 39 of the second heating ribbon 34 is fixed to the housing 2 by a fourth clamping device 5 having an integral thermal cut-off 6 including a tube 10 made of a conductive fuse material. The fourth clamping device 5 crosses the housing 2 through a bore made in the housing 2 and is electrically insulated from the bore of the housing 2, so that the current supplied by a power source (a storage battery (not shown)) connected to the clamping device (+) 30 circulates in the heating ribbons 31, 34 to the fourth clamping device 5 according to the invention and necessarily flows along the axis of the fourth clamping device 5, and reaches the housing 2 by a conductive connection including the fuse tube 10, so that the current flows through the fuse tube 10 that contacts and extends into the housing 2. The housing 2 is grounded (negative terminal) by a connection that engages with a hole 29 (-) made in the housing 2.

The embodiment of the electric air heating device 1 according to the invention shown in FIG. 6 comprises a housing 2 which defines an inner space 4 for passing an air flow to be heated. Two serpentine heating ribbons 31, 34 extend transversely in the inner space 4 into the air flow to be heated. The serpentine heating ribbons 31, 34 show a number of linear sections 40 separated longitudinally from one another by bends 41 (or bends, folds). The electric air heating device 1 has two holders 44 for insulation fixed to the opposite inner surfaces of the housing 2. The holders 44 each accommodate a solid piece 45 of insulating material. The at least two insulations 45 show aligned recesses, each of which is adapted to receive and accommodate a bend 41 of one serpentine heating ribbon 31, 34.

Detail of the electric air heater 1 shown in FIG. 7 shows a clamping device 5 (called clamping device (+) 30) adapted to be connected to the positive (+) terminal of a storage battery (not shown). Said clamping device (+) 30 has an inner end that crosses the bore of the housing 2 and is electrically connected to a heating ribbon 31 fixed in the inner space 4 of the electric air heater 1. The electric air heater also has a heating ribbon 34 fixed in the inner space 4 of the electric air heater 1 and electrically connected to a clamping device 5 (-) that is arranged in electrical contact with the housing 2 only via the fuse 10. The clamping device (+) 30 adapted to be connected to the negative (-) terminal of a storage battery (not shown), the heating ribbons 31, 34, the clamping device 5 (-), the housing 2 and the hole 29 (-) form part of an electric circuit that allows heating of the heating ribbon 3 by the Joule effect.

The present invention may be directed to numerous variations and applications other than those described above. In particular, unless otherwise specified, it is clear that the various structural and functional features of each of the embodiments described above should not be considered as combined and/or intimately and/or inseparably connected to one another, but rather as simple juxtapositions. Moreover, the structural and/or functional features of the various embodiments described above may be directed to any different juxtapositions or any different combinations, in whole or in part.

Claims (13)

a housing defined by a wall (2) having an inner surface (13) and an outer surface (7);
at least one resistive ribbon (3) arranged in the interior space (4) of the housing adapted to heat air of an air flow passing through the housing to form a heated air flow;
a fastening device (5) for cooperating with the inner surface (13) and the outer surface (7) of the wall (2) to fasten the resistance ribbon (3) to the wall (2),
a clamping shaft (9) extending across said wall (2);
a clamping device (5) including at least a clamping washer (8) of the clamping device (5) facing the outer surface (7) of the wall (2) and in conductive contact with the clamping shaft (9);
a cut-off (6) for opening an electric circuit supplying current to said at least one resistive ribbon (3) and for ceasing heating of said at least one resistive ribbon (3) in a condition of the electric air heating device (1) in which the temperature of said wall (2) exceeds a predetermined temperature (called an overheating condition),
An electric air heating device (1) of the type in which the cut-off (6) comprises a fuse (10) arranged in conductive contact with the clamp washer (8) and with the wall (2),
The tightening device (5)
Clamped longitudinally between said clamping washer (8) and said wall (2),
clamping said resistive ribbon (3) and said wall (2) together at least in said overheated state;
1. An electric air heating device (1), comprising at least one clamping spacer that does not provide an electrically conductive contact between said clamping washer (8) and said wall (2). The fastening spacer is
at least one metal tube (11) made of a non-melting material adapted to clamp said at least one resistance ribbon (3) to said wall (2) in said overheated state of said electric air heating device (1);
at least one tubular insulator (12) made of a non-melting material for radially electrically insulating said at least one metal tube (11) from said fuse (10);
2. The electric air heating device (1) according to claim 1, characterized in that it comprises a ring (14) extending longitudinally between the wall (2) and the at least one metal tube (11) made of a non-molten material and electrically insulating the at least one metal tube (11) made of a non-molten material from the wall (2) in the longitudinal direction. The electric air heating device (1) according to claim 2, characterized in that the clamping washer (8), the fuse (10), the at least one metal tube (11) made of a non-melting material, and the at least one tubular insulator (12) extend coaxially to the clamping shaft (9). Electric air heating device (1) according to claim 1 or 3, characterized in that the cut-off (6) is made of an electrically insulating material with high compressive strength and has a ring (14) extending longitudinally between the wall (2) and the clamping spacer. An electric air heating device (1) according to any one of claims 2 to 4, characterized in that the ring (14) is made of at least one ceramic material. An electric air heating device (1) as claimed in any one of claims 1 to 5, characterized in that it has a cover (15) that wraps around the outside of the clamping device (5) to collect the molten material of the fuse (10), such that the molten material of the fuse (10) is captured within the cover (15) no matter what position the clamping device (5) is in. An electric air heating device (1) according to any one of claims 1 to 6, characterized in that the clamping washer (8) is selected from the group consisting of a flat washer and a spring washer. An electric air heating device (1) according to any one of claims 1 to 7, characterized in that the fastening device (5) comprises a screw (22) and at least one nut (24) which cooperates with a threaded portion (23) of the fastening shaft (9) of the screw (22) to fix the resistance ribbon (3) to the wall (2) of the housing. An electric air heating device (1) according to any one of claims 1 to 7, characterized in that the fastening device (5) comprises a rivet. An electric air heating device (1) according to any one of claims 1 to 9, characterized in that the clamping shaft (9) of the clamping device is arranged to extend across a bore (21) formed in the wall (2) of the housing. An engine comprising at least one electric air heating device (1) according to any one of claims 1 to 10. A vehicle including the engine according to claim 11. A vehicle according to claim 12, comprising at least one electric air heating device (1) according to any one of claims 1 to 10.

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