Lighting device for a vehicle comprising a ventilation device disposed between two heat dissipation devices

A lighting module for a vehicle, the lighting module including a cooling circuit including a first chamber delimited by a first heat dissipation device, and designed for the cooling of at least one first lighting element of the lighting module, a second chamber delimited by a second heat dissipation device, and designed for the cooling of at least one second lighting element of the lighting module, and a third chamber delimited by a ventilation device. The third chamber separates the first chamber and the second chamber from one another.

The invention relates to the field of vehicle headlights. More particularly, it concerns the field of cooling of lighting modules which are designed to be fitted in such headlights.

Document DE 10 2014 10 2870 describes a lighting module comprising a cooling body comprising a base with, firstly, a first face on which means for emission of light are received, and secondly, a second face on which a cooling structure is formed. The lighting module also comprises a ventilation unit which is designed to generate forced convection of the cooling structure.

An objective sought in the aforementioned document is to improve the cooling capacity of the means for emission of light of the lighting module, whilst maintaining its compactness. For this purpose, according to the document, a deflection channel is designed such that it generates deflection of the air between a direction of flow of the flow of air at the output of the ventilation unit, and a direction of flow of the flow of air which passes through the cooling structure.

However, the document cited does not have an application in lighting modules comprising distinctly first means for emission of light and second means for emission of light, wherein these first and second means for emission of light are designed to provide a first lighting function and a second lighting function. In such modules, the first lighting function permits the formation of a first light beam, known as the high beam, whereas the second lighting function permits the formation of a second light beam, known as the low beam.

In this application, the first means for emission of light can be disposed on a first cooling body, whereas the second means for emission of light can be disposed on a second cooling body, distinct from the first body. The solution which is presented in the aforementioned document is not suitable for such a structure, and therefore is not responsible for forced cooling of each of the first and second cooling bodies of the lighting module.

In addition, such a solution applied to these lighting models requires significant structural modifications which contribute towards increasing the production cost of such a lighting module.

The objective of the present invention is to eliminate at least one of the aforementioned disadvantages, and to propose a particular arrangement of a lighting module making it possible to improve the cooling of each of these lighting elements, whilst maintaining its compactness and production cost.

For this purpose, the invention relates to a lighting module for a vehicle, the lighting module comprising a cooling circuit comprising:a first chamber delimited by a first heat dissipation device, and designed for the cooling of at least one first lighting element of the lighting module;a second chamber delimited by a second heat dissipation device, and designed for the cooling of at least one second lighting element of the lighting module; anda third chamber delimited by a ventilation device.

According to the invention, the third chamber separates the first chamber and the second chamber from one another.

The cooling circuit then makes possible cooling by forced convection of each of the first and second heat dissipation devices by means of the ventilation device. In fact, the ventilation device permits the formation of an air draft passing through the first chamber, and thus permitting forced cooling of the first heat dissipation device. The air which circulates in the ventilation device is then accelerated, and directed towards the second chamber, in order to permit the forced cooling of the second heat dissipation device. The solution according to the invention permits the cooling by forced convection of each of the heat dissipation devices by a single ventilation device which is interposed between the first chamber and the second chamber, thus making it possible to maintain the compactness of the lighting module.

Such positioning of the ventilation device clears valuable space at the input or the output of the cooling circuit, which makes it possible to accommodate more easily an actuator of the lighting module which is the subject of the invention.

The cooling circuit is advantageously formed in order to permit the circulation of a flow of air from the first chamber to the second chamber by passing via the third chamber.

According to a particular feature of the invention, the first chamber, the second chamber and the third chamber of the cooling circuit form together the cooling circuit of the lighting module. In other words, the cooling circuit is formed exclusively by the first chamber, the second chamber and the third chamber.

According to an embodiment of the invention, the first heat dissipation device comprises a mouth, and the second heat dissipation device comprises an opening, the mouth forming an input of the first chamber of the cooling circuit, and the opening forming an output of the first chamber of the cooling circuit.

Since the output of the first chamber is an input of the third chamber, it should be noted that the opening of the second heat dissipation device advantageously makes it possible to connect the first chamber to the third chamber fluidly.

According to another embodiment of the invention, the first heat dissipation device comprises a housing and a first heat dissipater, with the housing accommodating the first heat dissipater, and with the mouth, known as the first mouth, and a second mouth, being formed on the housing, such that the second mouth is facing the opening of the second heat dissipation device.

When the second mouth is disposed facing the opening, the second mouth and the opening both form an output of the first chamber.

The opening can comprise a securing bearing surface which cooperates with the second mouth. Such a securing bearing surface advantageously makes it possible to fit the housing of the first heat dissipation device on the second heat dissipation device. This fitting thus contributes towards limiting the losses of load of the flow of air circulating between the first chamber and the third chamber.

Advantageously, the housing comprises a receptacle which is designed to receive the first heat dissipater. The first heat dissipation device thus comprises the first heat dissipater and the housing. The housing delimited by these mouths and its receptacle makes it possible to form the first chamber according to the invention, when the first heat dissipater is received in this receptacle.

More particularly, the first heat dissipater comprises a base comprising a front face and a rear face opposite one another, the front face being designed to receive the at least one first lighting element, and the rear face comprising a cooling structure which extends from the latter. Such a cooling structure serves the purpose of increasing the exchange surface between the heat dissipated by the first heat dissipater and a flow of air which passes through it. When the first heat dissipater comprises such a base, it is possible to use the rear face of the base in order to close the receptacle of the housing.

The housing is thus preferably formed in order to surround the first heat dissipater, such as to channel the flow of air on the first dissipater and force the exchange of heat between the air and the first dissipater.

Advantageously, the cooling structure of the first heat dissipater is formed by fins. Alternatively, the cooling structure of the first heat dissipater is formed by rods.

According to a particular embodiment of the invention, the second heat dissipation device accommodates the ventilation device. Thanks to this particular feature, it is possible to optimise further the compactness of the lighting module.

According to a characteristic of the invention, the ventilation device comprises an air input and an air output forming respectively an input of the third chamber of the cooling circuit and an output of the third chamber of the cooling circuit.

According to a variant embodiment of the invention, the air input of the ventilation device is facing the opening of the second heat dissipation device.

According to another characteristic of the invention, the second heat dissipation device comprises an aperture, and the air output of the ventilation device forms an input of the second chamber of the cooling circuit, and the aperture forms an output of the second chamber of the cooling circuit.

It should be noted that the air output of the ventilation device thus forms firstly an output of the third chamber, and secondly an input of the second chamber.

According to a variant of the invention, the second heat dissipation device comprises a cover and a heat dissipater, known as the second heat dissipater, with the cover covering at least partly the heat dissipater of the second heat dissipation device, and the opening of the second heat dissipation device being delimited at least partly by the cover.

The cover and the second heat dissipater make it possible to delimit the second chamber. Thus, the cover is preferably assembled on the second heat dissipater in order to allow a flow of air at the input of the second chamber to be distributed in the second chamber.

More particularly, the second heat dissipater comprises a plate comprising a front surface and a rear surface opposite one another, the front surface being designed to receive the at least one second lighting element, and the rear surface comprising a cooling structure which extends from the latter. Such a cooling surface serves the purpose of increasing the exchange surface between the heat dissipated by the second heat dissipater and a flow of air which passes through it.

Advantageously, the cooling structure is formed by rods. Alternatively, the cooling structure is formed by fins.

Advantageously, the cover covers the rear surface of the plate of the second heat dissipater.

According to an embodiment of the invention, the rear surface of the plate and the cover delimit together a volume, the ventilation device being contained in this volume.

In order to preserve this volume, the rear surface of the plate advantageously comprises a flat area against which the ventilation device is rendered integral. By this means, it is possible to incorporate the ventilation device in this volume without increasing the volume.

The ventilation device is advantageously surrounded by the cooling structure of the second heat dissipater. More particularly, the ventilation device is surrounded by the rods of the second heat dissipater.

Advantageously, the at least one first lighting element makes it possible to provide a first lighting function of the lighting module. The first lighting module permits formation of a first light beam, known as the high beam.

Advantageously, the at least one second lighting element makes it possible to provide a second lighting function of the lighting module. The second lighting module permits formation of a second light beam, known as the low beam.

The first lighting function of the lighting module can advantageously be provided by a combination of the at least one first lighting element and the at least one second lighting element.

It should be noted that the first lighting element and the second lighting element are distinct from one another.

According to an advantageous embodiment of the invention, the air output of the ventilation device and the aperture of the second heat dissipation device are designed to channel a flow of air in opposite directions. This particular configuration has the advantage of optimising the forced convection in the second chamber, by forcing the flow of air to follow an undulating circulation path which assists the heat exchanges.

According to another embodiment of the invention, the air output of the ventilation device is designed to orient a flow of air in a first direction perpendicular to a second direction, along which this flow of air passes the air input.

Advantageously, the ventilation device comprises a centrifugal fan. Such a centrifugal fan is of the squirrel cage type, i.e. it comprises a centrifugal wheel.

According to another characteristic of the invention, the lighting module comprises a lens support which covers at least the first heat dissipation device, with the lens support comprising a recess facing the mouth, known as the first mouth. The recess advantageously permits the formation of the air draft when the ventilation device is actuated.

The invention also relates to a headlight for a vehicle, in particular a motor vehicle, comprising a lighting module as described according to the invention of the present document.

An advantageous technical combination concerns a housing as described in the present document, and designed to equip a lighting module.

Advantageously, the housing comprises a lower wall, and upper wall, and a base wall which confines two lateral walls to one another.

Advantageously, the walls of the housing delimit between one another a receptacle in which the first heat dissipater is received.

Advantageously, the upper wall of the housing participates in the formation of a cut-off edge of at least a first lighting element. Such a cut-off edge forms an area without light.

The cut-off edge is advantageously delimited by a front outer border of the upper wall which forms a cut-off line separating a light beam and the area without light.

Advantageously, a mouth, known as the first mouth, is formed in the lower wall of the housing.

Advantageously, a second mouth is formed in the base wall of the housing.

Advantageously, the lateral walls of the housing each comprise a cut-out which is designed for positioning of a heat dissipater, known as the first heat dissipater, as described in the present document, in the receptacle of the housing.

Another subject of this advantageous technical combination concerns a heat dissipation device, known as the first heat dissipation device, as described in the present document, comprising the housing and a heat dissipater, known as the first heat dissipater, as described in the present document.

As illustrated inFIGS. 1 and 2, the lighting module1according to the invention is represented in a low view of the front of the lighting module1inFIG. 1, and a low view from the rear of the lighting module1inFIG. 2. The lighting module1is designed to equip a vehicle headlight (not represented). The lighting module1is formed by the assembly of a lens support4and a cover31, each disposed on a single heat dissipater30. In order to permit the projection of light beams emitted by lighting elements received in the lighting module1, the lighting module1comprises a projection lens5. According to this embodiment, the projection lens5is supported by the lens support4of the lighting module1. The lens support4is more particularly formed by a lower part41and by an upper part42. The lower part41and the upper part42of the lens support4together accept the projection lens5. The lower part41of the lens support4comprises a frame40in order to allow it to be secured on the heat dissipater30.

In the example illustrated in theseFIGS. 1 and 2, the lens support4of the lighting module1, more particularly its lower part41, comprises a recess4A, and the cover31delimits at least partly an aperture3B. The recess4A and the aperture3B form respectively an input of a cooling circuit of the lighting module1, and an output of this same cooling circuit of the lighting module1. Such a cooling circuit, which is designed for circulation of a flow of air F, serves the purpose of permitting cooling of the lighting module1. More particularly, it serves the purpose of permitting cooling of the heat dissipation devices which it comprises.

With reference toFIG. 3, the lighting module1is represented in exploded view. Thus, there is representation of the lower part41of the lens support4, the upper part42of the lens support4, the projection lens5, a first heat dissipation device2, a second heat dissipation device3, and a ventilation device6.

The lens support4of the lighting module1is assembled by the frame40of its lower part41, from a front surface32′ of the heat dissipater30, whereas the cover31is assembled from a rear surface32″ of the heat dissipater30.

In greater detail, the first heat dissipation device2comprises a first heat dissipater20and a housing21, and the second heat dissipation device3comprises a second heat dissipater30and the cover31, as previously described. The ventilation device6for its part comprises a centrifugal fan. It should be noted that the second heat dissipater30corresponds to the dissipater described inFIGS. 1 and 2.

The first and second heat dissipation devices2,3and the ventilation device6are assembled in the lighting module1for the purpose of forming the cooling circuit.

With reference toFIG. 3, the lighting module1represented makes it possible to provide a first lighting function and a second lighting function. The first lighting function permits the formation of a first light beam, known as the high beam, whereas the second lighting function permits the formation of a second light beam, known as the low beam.

In order to provide these lighting functions, the lighting module1comprises first lighting elements7, and second lighting elements8, which are distinct from the first lighting elements7. Advantageously, the first lighting elements7and the second lighting elements8comprise light-emitting diodes. At least one of the lighting functions can be provided by the combination of the first and second lighting elements7,8. Preferably, the first lighting function is provided by the combination of the first lighting elements7and the second lighting elements8, and the second lighting function is provided by the second lighting elements8.

A description will now be provided in greater detail of each of the first and second heat dissipation devices2,3.

With reference toFIG. 3, the first heat dissipation device2comprises the first heat dissipater20and the housing21. The first heat dissipater20comprises a base22comprising a front face22′ and a rear face22″ which are opposite one another. The rear face22″ of the base22comprises a cooling structure23formed for example by fins23extending from this base22. The fins23of the first heat dissipater20extend more particularly from the rear face22″ of the base22, and perpendicularly to it. The front face22′ of the base22supports the first lighting elements7previously described, which are situated at a high border22A of the front face22′ of the base22. The first lighting elements7can be aligned horizontally along a single straight line.

Two arms24of the first heat dissipater20extend laterally from the base22of the first heat dissipater20. Each of these arms24comprises a first portion24A which is designed to position the first heat dissipater20in the housing21, and a second portion24B which is designed for securing of the first heat dissipater20on the lower part41of the lens support4of the housing21.

The first portion24A of each arm24extends laterally from the base22, parallel to the rear face22″ of the base22, whereas the second portion24B of each arm24extends from the first portion24A in a direction of orientation of the fins23. More particularly, each portion24A,24B of the arms24extends from the base22perpendicularly to the fins23.

The housing21of the heat dissipation device is represented in greater detail inFIG. 4. The housing21comprises a lower wall21A, an upper wall21B and a base wall21C which confine between them two lateral walls21D. The walls21A-21D of the housing21delimit between them a receptacle25in which the first heat dissipater20is received. A mouth2A, known as the first mouth2A, is formed in the lower wall21A of the housing21, and a second mouth2B is formed in the base wall21C of the housing21. The lateral walls21D of the housing21each comprise a cut-out21D1which is designed to authorise the passage of the arms24, and to permit the positioning of the first heat dissipater20in the receptacle25of the housing21. It will be understood that the first mouth2A and the second mouth2B are contained in the first heat dissipation device2.

As represented inFIG. 5, when the first heat dissipater20is accommodated in the receptacle25of the housing21, the first portions24A of the arms24abut the cut-outs21D1of the housing21. In this position of the first portions24A of the arms24, the base22of the first heat dissipater20closes by means of its front face22′ the receptacle25of the housing21, such that a chamber C1, known as the first chamber C1, of the cooling circuit is delimited by each of the walls21A-21D of the housing21, and by the base22of the first heat dissipater20, more particularly by the rear face22″ of the base22. The first mouth2A and the second mouth2B of the housing21then form respectively an input and an output of the first chamber C1The cooling structure23of the first heat dissipater20extends in this first chamber C1.

Optionally, a hole21E for passage of air can be provided at the intersection of the base wall21C of the lower wall21A with each of the lateral walls21D, as represented inFIG. 4. Such a hole21E for passage of air has the advantage of eliminating any risk of mechanical interference between the first dissipater20and the housing21, such as to guarantee the position of the first lighting elements7.

An air blade L can be formed between the base22and the upper wall21B of the housing21. This air blade L advantageously makes it possible to direct the heat released by the first lighting elements7to the inside of the first chamber C1.

In order to assemble the first heat dissipation device2represented inFIG. 5on the lower part41of the lens support4, represented inFIG. 6, the arms24of the first heat dissipater20are received in cavities41B of the lower part41of the lens support4. The first portion24A of the arms24is then supported against the base of each cavity41B, whereas the second portion24B of the arms24is supported against a stud41C of the lower part41of the lens support4. A hole24B1formed in each second portion24B of the arms24corresponds with a bore41C1formed in the corresponding stud41C. In the assembled position of the first heat dissipation device2on the lower part41of the lens support4, the lower wall21A of the housing21is placed against a low wall41D of the lower part41of the lens support4comprising the recess4A previously described, in order to make it possible to position the first mouth2A of the housing21opposite the recess4A of the lens support4, and channel the air at the input of the recess4A of the lens support4to the input of the first chamber C1. The first mouth2A of the housing21and the recess4A of the lens support4advantageously have an identical form.

As represented inFIG. 5, the first lighting elements7are advantageously recessed relative to a front outer border21B1of the upper wall21B of the housing21.

With reference once more toFIG. 3, the second heat dissipation device3comprises the second heat dissipater30and the cover31. The second heat dissipater30comprises a plate32comprising a front surface32′ and a rear surface32″ which are opposite one another. The rear surface32″ of the plate32comprises a cooling structure33formed for example by the rods33extending from this plate32, as represented inFIG. 7.

The front surface32′ of the plate32supports the second lighting elements8previously described.

The second heat dissipater30comprises an opening34formed in its plate32, in order to pass through each of the front and rear surfaces32′,32″ of the plate32. The opening34extends in particular by means of a securing bearing surface34A, in order to project from the front surface32′ of the plate32. It will thus be understood that the opening34is contained in the second heat dissipation device3.

As represented inFIG. 7, the rear surface32″ of the plate32comprises a flat area35which is designed to receive the ventilation device6. The flat area35is without a cooling structure33, thus delimiting a space which is designed to be occupied by the ventilation device6.

The opening34is advantageously formed in order to open onto this flat area35of the rear surface32″ of the plate32.

With reference toFIG. 3, the cover31is designed to be fitted against the rear surface32″ of the plate32, such that the cooling structure33of the second heat dissipater30is covered by the cover31. When the cover31and the rear surface are assembled to one another, an edge of the cover31and an edge of the rear surface32″ of the plate32delimit the opening3B previously described. It will thus be understood that the opening3B is contained in the second heat dissipation device3.

In order to allow the cover31to be secured on the rear surface32″ of the plate32, first bores can be provided on the rear surface32″ of the plate32, in order to correspond with holes formed in the cover31, such that securing screws can pass through the holes in the cover31, in order to be accommodated in the first bores, and permit securing of the cover31on the rear surface32″ of the plate32.

The cover31and the rear surface32″ of the second heat dissipater30delimit together a second chamber C2of the cooling circuit, an output of which is formed by the opening3B of the second heat dissipation device3.

In order to permit the securing of the lower part41of the lens support4on the front surface32′ of the plate32, second bores32A can be provided on the front surface32′ of the plate32, in order to correspond with holes40A formed in the frame40of the lower part41, such that securing screws can pass through the holes40A of the frame40, in order to be accommodated in the second bores32A, and permit securing of the frame40of the lower part41of the lens support4on the front surface32′ of the plate32.

When the lower part41of the lens support4, previously equipped with the first heat dissipation device2, is fitted on the plate32of the second heat dissipater30, the opening34of the second heat dissipater30is then facing the second mouth2B of the first heat dissipation device2previously described. Preferably, the securing bearing surface34A of the opening34is designed to fit together with the second mouth2B. The securing bearing surface34A and the second mouth2B preferably have forms which are complementary with one another in order to make possible this arrangement.

With reference toFIG. 3, the ventilation device6is accommodated in the second heat dissipation device3. More particularly, the rear surface32″ of the plate32and the cover31delimit together a volume V in which the ventilation device6is contained.

As illustrated inFIG. 7, the ventilation device6is disposed against the flat area35of the rear surface32″ of the plate32of the second heat dissipater30. In this arrangement of the ventilation device6, an air input6A, shown inFIG. 3, of the ventilation device6, opens onto the opening34of the plate32of the second heat dissipater30. Also, in this arrangement, an air output6B, shown inFIGS. 3 and 7, of the ventilation device6, opens into the second chamber C2of the cooling circuit. The air input6A and the air output6B of the ventilation device6form respectively an input and an output of a third chamber C3of the cooling circuit. The opening34of the plate32of the second heat dissipater30forms both an output of the first chamber C1and an input of the third chamber C3. The ventilation device6can be fitted by being screwed on the flat area35of the rear surface32″ of the second heat dissipater30.

The air output6B of the ventilation device6forms an input of the second chamber C2. The air output6B of the ventilation device6and the opening3B of the second heat dissipation device3are each designed to channel a flow of air in opposite directions. According to the example illustrated here, the air output6B and the opening3B extend on planes which are parallel, or substantially parallel.

The ventilation device6advantageously comprises a centrifugal fan which is configured to allow the air output6B of the ventilation device6to orient a flow of air perpendicularly to its air input6A.

An electrical supply plug60is designed to supply the ventilation device6electrically. An electrical supply cable can be provided to pass via the opening3B of the second heat dissipation device3, and be connected to the electrical supply plug60of the ventilation device6.

With reference toFIG. 8, the cooling circuit of the lighting module1is formed in succession by the first chamber C1, the third chamber C3and the second chamber C2, delimited respectively by the first heat dissipation device2, the ventilation device6, and the second heat dissipation device3. A flow of air F is represented passing through the first heat dissipation device and the second heat dissipation device, via the ventilation device.

It can be noted from the foregoing information that the third chamber C3separates the first chamber C1and the second chamber C2from the cooling circuit.

In greater detail, it should be noted that:the input2A of the first chamber C1forms an input of the cooling circuit;the output2B of the first chamber C1forms an input of the third chamber C3;the output6B of the third chamber C3forms an input3A of the second chamber C2;the output3B of the second chamber C2forms an output of the cooling circuit.

A description will now be provided of the operation of the cooling circuit with reference toFIG. 8, where the lighting module1is represented by a view in vertical cross-section.

The view in cross-section inFIG. 8represents the lighting module1comprising:the first mouth2A of the first heat dissipation device2forming the input2A of the first chamber C1, and having a form identical to the recess4A of the lower part41of the lens support4;the second mouth2B of the first heat dissipation device2forming the output2B of the first chamber C1;the air input6A of the ventilation device6forming the input6A of the third chamber C3;the opening34of the second heat dissipation device3connecting the output2A of the first chamber C1and the input6A of the third chamber C3fluidly;the air output6B of the ventilation device6forming the output6B of the third chamber C3and the input3A of the second chamber C2;the opening3B of the second heat dissipation device3forming the output3B of the second chamber C2.

When the ventilation device6is controlled electrically, it generates at its air input6A and air draft making it possible to direct a flow of air F from the input2A of the first chamber C1to the output2B of the first chamber C1. This air draft advantageously makes it possible to force the cooling of the fins23of the first heat dissipater20which are contained in the first chamber C1. Subsequently, the flow of air F is directed to the input6A of the third chamber C3via the opening34, in order to be accelerated by the centrifugal fan, before being discharged into the second chamber C2from the output6B of the third chamber C3, also forming an input3A of the second chamber C2. The flow of air F is then directed from the input3A of the second chamber C2to a first wall31A of the cover31opposite a second wall31B of the cover31, delimiting partly the opening3B of the second heat dissipation device3. The air output6B is oriented such that the flow of air F is directed towards, and comes up against, the first wall31A of the cover31. This therefore optimises the forced convection in the second chamber C2by forcing the flow of air F to change direction through the cooling structure33of the second heat dissipater30, thus increasing the exchange of heat between the dissipater32and the flow of air.

With reference toFIG. 9, the lighting module1is represented without the upper part42of the lens support4, but with the lower part41of the lens support4. The first heat dissipation device2and the second heat dissipation device3are disposed relative to one another in order to provide the first and second lighting functions of the lighting module1. More particularly, in this arrangement, the first lighting elements7supported by the first heat dissipater20, and the second lighting elements8supported by the second heat dissipater30are disposed on their respective heat dissipater20,30such as to be separated by a cut-off edge.

The cut-off edge is advantageously formed by the upper wall21B of the housing21. more particularly, the cut-off edge is formed by the front outer border21B1. The cut-off edge makes it possible to prevent the emission of light by the first lighting elements7above the cut-off edge. This advantageously makes it possible to provide the first lighting function, i.e. the formation of a first light beam, known as the high beam, which can be projected from the projection lens5. It will be understood that, when the first lighting function is provided, the first and second lighting elements7,8are used.

When the second lighting function of the lighting module1is required, the emission of light by the second lighting elements8is advantageously projected by the projection lens5in order to form the second light beam, known as the low beam. It will be understood that, when the second lighting function is provided, the first lighting elements7are not used.

It will be appreciated that the characteristics, variants and different embodiments of the invention can be associated with one another according to different combinations, provided that these are not incompatible or mutually exclusive. It is possible in particular to conceive of variants of the invention which comprise only a selection of characteristics described hereinafter in a manner isolated from the other characteristics described, if this selection of characteristics is sufficient to provide a technical advantage, or to differentiate the invention from the prior art.