EP3270401B1 - Temperature-dependent switch with insulating disc - Google Patents

Description

The present invention relates to a temperature-dependent switch having a housing which comprises a cover part with an upper side and a lower part with a peripheral wall, the upper portion of which engages over the cover part, with at least one arranged on the top of the cover part first outer contact surface, at least one on the outside the housing provided second outer contact surface, and at least one arranged at least on the upper side of the cover part protective film, wherein the cover part cross-upper portion of the peripheral wall of the lower part holds the lid part with the interposition of the protective film on the lower part, and arranged with a temperature-dependent in the housing Derailleur, which establishes or opens in dependence on its temperature, an electrically conductive connection between the first and the second outer contact surface.

Such a switch is from the DE 196 23 570 A1 known.

The known temperature-dependent switch is used in a conventional manner to monitor the temperature of a device. For this purpose, for example, it is brought into thermal contact with the device to be protected via one of its outer surfaces, so that the temperature of the device to be protected influences the temperature of the derailleur.

The switch is electrically connected via the soldered to its two outer contact pads leads in series in the supply circuit of the device to be protected, so that below the response temperature of the switch, the supply current of the device to be protected flows through the switch.

The known switch has a deep-drawn lower part, in which an inner circumferential shoulder is provided, on which a lid part rests. The lid part is held firmly on this shoulder by a raised and at its upper portion by about 60 ° inwardly bent circumferential wall of the base.

Since the cover part and lower part are made of electrically conductive material, an insulating film extending around the cover part is provided between them, which extends inwardly in the switch parallel to the cover part and is pulled up laterally, so that its edge region except for the Extends the top of the lid part. The bent upper portion of the peripheral wall of the lower part rests on the edge region of the insulating film, wherein the wall and edge region of the insulating film at an angle of approximately 30 ° to the top of the cover part of this pioneering. The end face of the upper portion of the peripheral wall thus has an angle of 90 ° to the insulating film.

The temperature-dependent switching mechanism here comprises a spring snap-action disk, which carries the movable contact part, as well as a bimetallic disk which is put over the movable contact part. The spring snap-action disc presses the movable contact part against a stationary counter contact on the inside of the cover part.

With its edge, the spring snap-action disc is supported in the lower part of the housing, so that the electric current flows from the lower part through the spring snap-action disc and the movable contact part into the stationary counter-contact and from there into the cover part.

As the first outer terminal is a first outer contact surface, which is arranged centrally on the cover part. As a second outer terminal provided on the flanged edge of the lower part second outer contact surface is used. But it is also possible to arrange the second external connection not on the edge but laterally on the current-carrying housing or on the underside of the lower part.

From the DE 198 27 113 C2 It is known to attach to the spring snap-action disk a so-called contact bridge, which is pressed by the spring snap-action disc against two provided on the cover part stationary mating contacts. In this case, the second outer contact surface is arranged on the upper side of the lid part. The two mating contacts are connected through the lid part with the two outer contact surfaces. The current then flows from an outer contact surface via the associated mating contact through the contact bridge in the other stationary mating contact and from there to the other outer contact surface, so that the spring snap disk itself is not traversed by the operating current.

This design is particularly chosen when very high currents must be switched, which can not be easily passed through the spring washer itself.

In both design variants, a bimetal disc is provided for the temperature-dependent switching function, which rests below its critical temperature without force in the switching mechanism, wherein it is arranged geometrically between the contact part or the contact bridge and the spring snap-action disc.

In the context of the present invention, under a bimetal part, a multi-layer active sheet-metal components made of two, three or four are inseparably connected to one another Components with different coefficients of expansion understood. The connection of the individual layers of metals or metal alloys are cohesively or positively and are achieved for example by rolling.

In their low-temperature position, such bimetallic parts have a first and their high-temperature position have a second stable geometric conformation, between which they change over in a temperature-dependent manner in the manner of a hysteresis. When the temperature changes beyond its response temperature or below its return temperature, the bimetal parts snap over into the other conformation. The bimetal parts are therefore often referred to as snap disks, wherein they can have an elongated, oval or circular shape in plan view.

Increases now the temperature of the bimetallic disc due to a temperature increase in the device to be protected beyond the critical temperature addition, the bimetallic disc changes its configuration and works against the spring snap-action disc, that they are the movable contact part of the stationary mating contact and the current transfer member of the two stationary mating contacts lifts, so that the switch opens and the device to be protected is turned off and can not heat up.

In these constructions, the bimetallic disc is mounted mechanically free of forces below its transition temperature, wherein the bimetallic disc is not used to guide the flow.

It is advantageous that the bimetallic discs have a long mechanical life, and that the switching point, so the critical temperature of the bimetal disc, not changed even after many switching cycles.

If lower requirements are placed on the mechanical reliability or the stability of the transition temperature, the bimetallic snap disk can also take over the function of the spring snap-action disc and possibly even the current transfer member, so that the switching mechanism comprises only one bimetallic disc, which then the carries movable contact part or instead of the current transmitting member has two contact surfaces, so that the bimetallic disc not only provides for the closing pressure of the switch, but also leads the current in the closed state of the switch.

Moreover, it is known to provide such switches with a parallel resistor which is connected in parallel with the external terminals. When the switch is open, this parallel resistor takes over part of the operating current and keeps the switch at a temperature above the transition temperature, so that the switch does not automatically close again after cooling down. Such switches are called self-holding.

It is also known to provide such switches with a series resistor, which is traversed by the operating current flowing through the switch. In this way, an ohmic heat is generated in the series resistor, which is proportional to the square of the flowing current. If the current exceeds a permissible level, the heat of the series resistor causes the rear derailleur to open.

In this way, a device to be protected is already switched off from its supply circuit when too high current flow is recorded, which has not yet led to excessive heating of the device.

Instead of a generally round bimetallic disc and a cantilever clamped on one side can be used, which carries a movable contact part or a contact bridge.

But it can also be used temperature-dependent switch, which have no contact plate as a current transfer member but a spring member which carries the two mating contact or on which the two mating contacts are formed. The spring member may be a Bimetallteil, in particular a bimetallic snap disk, which not only provides the temperature-dependent switching function, but at the same time also provides the contact pressure and the current leads when the switch is closed.

All these different design variants can be realized with the switch according to the invention, in particular, the bimetallic disc can take over the function of the spring snap-action disc.

From the EP 2 654 057 A1 is a temperature-dependent switch with a housing having a cover part and a lower part, and with a temperature-dependent switching mechanism disposed in the housing, which establishes or opens depending on its temperature, an electrically conductive connection between two provided on the housing outer terminals, of which at least one is arranged on an upper side of the switch, and are connected to the connecting leads, wherein a protective cap sits on top of the cover part, which covers the at least one outer terminal on the upper side and from which leads the connected to the at least one outer terminal pigtail laterally.

From the DE 195 17 310 A1 is one to the from the above-mentioned DE 196 23 570 A1 Comparable constructed temperature-dependent switch known in which the cover part, however, is made of a PTC thermistor and can rest without interposition of an insulating film on an inner peripheral shoulder of the lower part to which they by the 90 ° radially inwardly bent upper portion of the peripheral wall of the lower part is pressed.

In this way, the PTC thermistor cover is electrically connected in parallel to the two outer terminals, so that it gives the switch a self-holding function.

Such PTC thermistors are also referred to as PTC resistors. They are made, for example, from semiconductive, polycrystalline ceramics such as BaTiO ₃ .

Also in the case of the above mentioned DE 198 27 113 C2 known, temperature-dependent switch with contact bridge, the cover part made of PTC thermistor material, so that it also has a self-holding function. At the lid part here two rivets are arranged, the outer heads of the two outer terminals form, and interact their internal heads as a stationary mating contacts with the contact bridge.

The cover member may be made of insulating material or metal in a switch of this type also, in the latter case as from the DE 196 23 570 A1 Known switch is provided around the cover part extending around insulating sheet, which extends inside the switch in parallel to the cover part and is pulled up laterally, so that its edge region extends to the top of the cover part. The radially inwardly bent by about 60 ° upper portion of the peripheral wall of the base presses while laying the insulating film flat on the lid part.

In the known switches, the housing is typically protected from the entry of contaminants by a seal which is applied before or even after the connection of terminal lugs or connecting leads to the external terminals.

From the DE 41 43 671 A1 It is known to overmold the outer terminals with a one-component thermosetting plastic. From the DE 10 2009 039 948 It is known to cast terminal lugs with an epoxy resin. It is also known to provide the known switch after soldering of leads or terminal lugs often with a impregnating varnish or protective varnish.

In order to prevent paint from penetrating into the interior of the housing, in the case of the aforementioned DE 196 23 570 A1 known switch, the cover part provided with a bead, with which it penetrates when bending the upper portion of the peripheral wall of the lower part in the insulating film. Although this ensures a better seal, in many cases, however, penetrates paint into the interior of the housing.

In the from the above-mentioned DE 196 23 570 A1 known and comparable switches lying between the lower part and the lid part insulating film is pulled laterally between the wall of the lower part and the lid part and turned over with its edge region on top of the lid part. The rigid insulating film is wavy by turning and forms rosettes, which can not be securely sealed by the flat pressing on them upper portion of the peripheral wall of the base. Furthermore, there is a risk that coating lacquer penetrates through the rosettes into the interior of the switch. The DE 196 23 570 A1 tries to reduce this problem by the already mentioned bead.

The DE 10 2013 102 089 B4 describes a switch, as in principle from the above-mentioned DE 196 23 570 A1 is known. This switch has between the shoulder in the lower part and the cover part on a spacer ring, which allows a larger switching distance between the movable contact part and stationary counter contact.

To that of the in the DE 196 23 570 A1 described known leakage problem, the edge region of the insulating is cut from the outside V-shaped, whereby the ripple is greatly reduced, so that the tightness is improved.

The DE 10 2013 102 006 B4 also describes a switch, as in principle from the above-mentioned DE 196 23 570 A1 is known. This switch is like the one from the DE 195 17 310 A1 Known switch on a cover part of PTC thermistor material. Because of the lack of pressure stability of this PTC cover, can be effected by the approximately 90 ° radially inwardly bent upper portion of the peripheral wall of the base no adequate sealing of the known switch against the entry of impurities, which is why the bent upper portion of the peripheral wall at the time of the DE 195 17 310 A1 known switch must be sealed against the top of the lid part with silicone, which often causes problems.

The DE 10 2013 102 006 B4 solves this problem in that a cover sheet is provided, which rests only on the top of the PTC lid, and in which the bent by about 90 ° and flat on the cover flying up the upper portion of the peripheral wall of the base penetrates. The end face of the upper portion of the peripheral wall faces away from the cover sheet. However, the flat-lying upper portion of the peripheral wall of the base often does not provide the desired seal.

Under a "arranged at least on the top of the lid part protective film" is therefore understood both a flat-lying cover sheet, as they are known from DE 10 2013 102 006 B4 is known, as well as the edge region of an example of the DE196 23 579 A1 or the DE 10 2013 102 089 B4 known, extending around the lid part around insulating film which extends inside the switch between the lower part and the lid part and is pulled laterally between the wall of the lower part and the lid part and turned over with its edge region on top of the lid part.

A protective film in the sense of the present invention can serve for the electrical insulation, the mechanical protection and / or the sealing of the interior of the switch.

At a switch and a cover sheet and an insulating film may be provided, as for example, the DE 10 2013 102 089 B4 shows. On the upper side of the cover part of this switch, an insulating covering film, for example made of Nomex®, is arranged, which extends with its edge radially outwards up to the insulating film, which consists for example of Kapton®. Nomex® and Kapton® consist of aramid paper or aromatic polyimides.

Against this background, the present invention seeks to eliminate in the known switch in a structurally simple and inexpensive way, the above-mentioned problems, at least reduce.

This object is achieved according to the invention in the switch mentioned above, that the upper part of the peripheral wall of the lower part which overlaps the cover part is formed as a continuously curved edge which presses with its end face on the protective film.

According to the invention, the upper portion of the peripheral wall is therefore not bent radially inwardly as in the prior art, but bent in itself so that it forms a continuous curved edge in the manner of a bead, where it can get into contact with the protective film with its end face on which it preferably rests sealingly.

If the protective film is an insulating film extending around the lid part, its edge region is pushed further towards the upper side of the lid part as the upper portion of the peripheral wall is further bent, thereby already providing better sealing of the switch. The front side can also penetrate into the edge region, which further improves the seal, because a self-contained connection between arched edge and insulating film is formed.

If the protective film is a covering film resting on the upper side of the cover part, then the end face of the curved edge penetrates into the covering film, which here too improves the sealing because a self-contained connection arises between the curved edge and cover film

The front side of the upper portion is bent inwardly by at least 90 °, so that a circumferential bead is formed, which is for example U-shaped in cross section, when the portion is bent or curved in itself by about 180 °. However, it is preferred according to the invention, when the end of the upper portion is bent inwards by at least 120 °, because then the front side comes so from above into contact with the protective film that they can press them on the top of the cover part.

If the protective film is an insulating film running around the lid part, whose edge region extends at an angle to the top side of the lid part, an additional sealing of the interior of the switch results, which provides an overall better seal.

Namely, the inventor of the present application has recognized that the problems with the tightness of the known switches are due to the fact that the insulating sheet curls or wrinkles when bent on the top of the lid member, resulting in that the wall of the base is not far enough on the top of the lid part can be bent. Furthermore, this waviness of the insulating foil on the upper side and on the peripheral end side of the lid part causes creepage paths for liquids to form, so that when impregnating the known switch with protective lacquers they can creep into the interior of the switch.

Even with respect to other electrical insulation materials, the bent edge of the lower part does not seal the upper side so well that in any case it is ensured that no liquid can get into the interior of the switch during resin formation.

Even when soldering connecting lines on the top or there provided contact surface is not completely ruled out that get solder or corresponding liquids into the interior of the switch.

The fact that the insulating film is now pressed in its edge region by the end face of the curved edge on the top of the cover part, already results from the better application of the edge region of the insulating film to the top of the lid part a better sealing effect, which rises through the on the edge region or even penetrating end face is further improved because self-contained seal arises.

Another surprising advantage that can be realized with the switch according to the invention lies in the ability to assemble the switch as a Surface Mounted Device (SMD) according to the Reel technology (belt and coil) and with pick and place SMD placement machines on a circuit board apply and mount there and eg to contact in the reflow process. Namely, both the curved edge and the one or both contact surfaces on the top of the cover part can be used as a contact surface for the Surface Mounted Technology (SMT) compound.

For this purpose, the switch with the cover part is placed on the printed circuit board, so that the contact surface or the contact surfaces on the upper side of the cover part and the curved edge are available for SMT contacting. The edge serves the mechanical fixing and the thermal connection of the switch to the circuit board and the electrical contact, if only one contact surface on the top of the cover part is present.

This type of assembly is now possible for the first time for temperature-dependent switch of the type in question here, because on the one hand, the curved edge and the contact surfaces to each other have such a small height difference that this can be compensated by the solder in the reflow process, and because of other the wavy edge region of the insulating film is pressed by the front side of the curved edge so far on the lid part that he no longer bothers with this type of mounting.

If the curved edge is soldered at its entire circumference with the circuit board, also results in a further sealing of the switch, because impurities can not even reach the top of the cover part. This advantage realized by the new switch even if the edge is indeed curved, but not sealingly rests with its front side on the insulating film.

The object underlying the invention is completely solved in this way.

In this case, it is preferred if the curved edge defines a first plane which defines at least one contact surface on the upper side, a second plane parallel to the first plane, and the first and the second plane are at a distance from one another, which is an assembly of the switch on a circuit board with SMT allows, preferably less than 2 mm.

The inventors of the present application have recognized that bending the upper portion of the circumferential wall forms a curved edge which spans a plane approximately at the same level as the plane passing through the one or more contact surfaces the top of the ceiling part is clamped. These two levels are spaced so close together that the top of the switch can first be mounted on a Surface Mounted Technology (SMT) circuit board. The new switch can therefore be processed like an SMD component.

The distance between the two planes is less than 2 mm, in a preferred embodiment even less than 1 mm, these differences in height can be easily compensated by the solder paste in SMT.

Further, it is preferred if the at least one protective film comprises an insulating film, which extends inside the switch between the lower part and the lid part and laterally between the peripheral wall of the lower part and the lid part and is folded over with its edge region on the upper side of the lid part.

Here it is advantageous that the new switch can be formed with electrically conductive lower part and electrically conductive cover part, wherein the insulating film for electrical insulation between the cover part and lower part is used and at the same time prevents the ingress of contaminants into the interior of the switch.

The arched edge according to the invention results in an additional sealing of the switch, namely because the curved edge presses with its end face the insulating film on the top of the cover part and possibly even penetrates into this, so that the curved edge an annular protection against the ingress of contaminants represents.

The insulating film may have compared to the insulating films used in the prior art have a smaller outer diameter, whereby the waves and wrinkles are reduced, which arise when turning over the insulating film. This smaller diameter insulating film can be used because a particularly good seal of the new switch is realized by the curved edge, so that less material of an insulating film is required for the seal.

Of course, this insulating film can also be used when the cover part and / or lower part are not made of electrically conductive material, so that the insulating film is only the mechanical seal against the entry of impurities, but not the electrical insulation.

Alternatively or additionally, it is preferred if the at least one protective film comprises a cover film which rests on the upper side of the cover part, the cover film preferably extending to below the edge region of the insulating film.

When the cover film is used alone, it is used in switches in which usually the upper part is not made of metal, but consists of electrically insulating plastic or PTC material. The cover then serves both the mechanical protection of the upper part, on the other hand, the seal between the curved edge and the top of the cover part.

The front side of the curved edge can also be bent down so far on the cover that it penetrates into the cover, which also causes a particularly efficient over the entire circumference of the curved edge.

If the cover film is used in addition to the insulating film, this ensures a particularly good sealing of the new switch, wherein the diameter of the insulating film may be chosen so that the end face of the curved edge either penetrates into the resting on the cover film edge region of the insulating film, or but in the cover itself, namely because the insulating ends with its edge region under the curved edge of the peripheral wall.

All these measures mean that the new switch against the entry of impurities in the interior of the housing is very well protected, namely because the edge with its front side enters such a close connection with the protective film that neither particulate nor liquid contaminants in the interior of the switch can penetrate.

It is further preferred if the protective film consists of polyimide, preferably of aromatic polyimide, or aramid paper.

Such protective films are known from the prior art, they are sold, for example under the trade name Kapton® or Nomex®.

Insulating films made of these materials are characterized by the fact that they are "drawable", so slightly stretch when inserting the lid part in the lower part, and that they can still be folded well around the front side of the lid part on the top, and further the required Dielectric strength is achieved.

In general, it is preferred if the second outer contact surface is arranged on the curved edge, wherein then preferably the switching mechanism carries a movable contact part, which cooperates with a stationary counter-contact, which on an inner side the lid part is arranged and cooperates with a arranged on the top first outer contact surface.

Here it is advantageous that the two outer contact surfaces are almost in one plane, so that the switch can be mounted with the lid part on a printed circuit board according to SMT and contacted. The curved edge serves not only the mechanical fixation and the electrical contact of the switch, but at the same time the thermal connection to the circuit board, further being given a further protection against the ingress of contaminants, because the curved edge closes the top of the lid part tight towards the outside.

Alternatively, it is preferred if the second outer contact surface is arranged on the upper side of the cover part, wherein preferably the switching mechanism then carries a Stromübertragungsglied, which cooperates with two stationary mating contacts, which are arranged on an inner side of the cover part, and one of which with a the two arranged on the top outer contact surfaces cooperates.

The advantage here is that the new switch can also be designed for switching and carrying very high currents, what the two stationary mating contacts interact with a current transfer member in the form of a contact bridge or a contact plate, so that the operating current of the device to be protected not by the spring -Schnappscheibe or even the bimetallic snap disk but only flows through the power transmission element.

The curved edge then serves not the electrical contact, but on the one hand, the mechanical fixation and the thermal connection, on the other hand, the protection of the top of the lid part before the entry of impurities.

In all the cases where the new switch is used and processed as an SMD component, the curved edge surrounds after mounting on the circuit board, the contact surface or the contact surfaces on the top of the cover part and the transition between the protective film on the top of the lid part and the front side of the curved edge, so is a barrier against the ingress of contaminants.

The cover part and / or the lower part can be made of electrically conductive material, which allows the construction of a mechanically very pressure-resistant and easy to manufacture switch.

It is preferred if the switching mechanism has a bimetal part.

The bimetallic part may be a round, preferably circular bimetal snap-action disc, wherein it is also possible to use as bimetallic an elongated, cantilevered bimetallic spring. With simple switches, this bimetal can also be used to conduct electricity.

However, it is preferred if the rear derailleur additionally has a spring snap-action disc.

This spring snap-action disc can, for example, carry the movable contact part and carry the current through the closed switch and, in the closed state, provide for the contact pressure. In this way, the bimetal is relieved of both the current flow and the mechanical load when it is closed.

If the derailleur has a current transmitting member which cooperates with two stationary mating contacts, either only one bimetallic part can be provided, which then provides the closing pressure and the opening function takes over, or it can additionally be provided a spring member, which expends the closing force, so that the bimetal part is only mechanically loaded when it opens the switch.

The present invention is particularly suitable for round temperature-dependent switches, which are thus round, circular or oval in the plan view of the lower part or cover part, with other housing forms can use the invention, when bending over the upper portion of the peripheral wall of the lower part of the curved Edge arises, which presses on the protective film and thus exerts the protective function against the entry of impurities.

Against this background, the present invention also relates to an electronic circuit with at least one mounted on a circuit board, temperature-dependent switch according to the invention, wherein the switch rests with its cover part on the circuit board.

In this way, the advantages already mentioned above are realized, namely that the new temperature-dependent switch can be used as an SMD component, without additional contact lugs, contact bridges or connecting leads are required to electrically connect the switch to the printed circuit board.

So far, namely switches of the type in question were mounted on a circuit board, that they are placed with their underside on the circuit board, in which case contact lugs are guided by the contact surfaces on the switch to pads on the circuit board. However, this type of assembly is very complex and error-prone, requires in particular an additional pre-assembly of the temperature-dependent switch with the contact lugs.

The new, so to speak over head on the circuit board to be mounted switch the disadvantages associated with the conventional mounting method in the prior art are eliminated in a surprisingly simple manner. These advantages are particularly due to the fact that in the new switch, the lid portion overlapping upper portion of the peripheral wall of the lower part is formed as a continuous curved edge, so that this edge is available as a contact surface.

Even without the protective function, which achieves the curved edge in that its front side presses on the protective film, so shows an inventive switch advantages, because for the first time the mounting SMT in a simple manner possible.

During assembly, then, the first outer contact surface on a provided on the circuit board first soldering surface and is soldered thereto, while the curved edge assigns to a provided on the circuit board second solder surface and soldered thereto, preferably wherein the second soldering surface an annular Soldering surface is, and the curved edge is soldered along its entire circumference continuously with the second soldering surface.

Here it is advantageous that the curved edge not only serves the electrical contact, but also serves in the sense already described above as a barrier against the entry of impurities. Even if the front side of the curved edge does not press on the protective film or even penetrates into this, it is very effectively ensured at least in a fully assembled switch that no contaminants from the top of the switch can get into the interior of the switch, Namely, because the top of the switch is effectively protected from the entry of particulate or liquid contaminants by the soldering edge acting as a barrier.

In this case, it is further preferred if the second outer contact surface is arranged on the curved edge, wherein alternatively the second outer contact surface can also be arranged on the upper side of the cover part and is soldered to a third soldering surface provided on the printed circuit board.

As already mentioned above, the curved edge can serve for the mechanical fixation and for the formation of a barrier against contamination, while at the same time serving as a second contact surface.

It is still preferred if in the circuit board, a vent hole is provided, which opens into a space which is formed between the circuit board and the curved edge.

Here is an advantage that in this space, which is completely closed after soldering the curved edge to the environment, no pressure, which forms would counteract a secure mechanical and electrical connection of the contact surfaces with the solder pads on the circuit board.

Other features and advantages will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in respectively specified combinations, but also in other combinations or alone, without departing from the scope of the present invention.

Fig. 1

eine schematische Schnittdarstellung in Seitenansicht eines temperaturabhängigen Schalters aus dem Stand der Technik;

Fig. 2

in einer schematischen, teilweise geschnitten Darstellung in Seitenansicht einen neuen temperaturabhängigen Schalter;

Fig. 3

in einer Darstellung wie Fig. 2 den neuen Schalter, der als SMD mit seiner Ober-seite auf eine Leiterplatte gelötet ist; und

Fig. 4

in einer schematischen, teilweise geschnitten Teil-Darstellung in Seitenansicht einen weiteren neuen temperaturabhängigen Schalter.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

Fig. 1

a schematic sectional view in side view of a temperature-dependent switch from the prior art;

Fig. 2

in a schematic, partially sectional view in side view of a new temperature-dependent switch;

Fig. 3

in a presentation like Fig. 2 the new switch, which is soldered as an SMD with its upper side on a printed circuit board; and

Fig. 4

in a schematic, partially cut part representation in side view of another new temperature-dependent switch.

In Fig. 1 is shown schematically, not to scale and in the lateral section a circular in plan view temperature-dependent switch 10 ', as is known from the prior art.

The well-known switch 10 'has a temperature-dependent switching mechanism 11, which is arranged in a housing 12 in which an insulating film 13 is arranged between a cup-shaped lower part 14 and a lid part 15 extends, which closes the lower part 14.

In the lower part 14, a circumferential, stepped shoulder 16 is provided, on which a spacer ring 17 is arranged, on which the lid part 15 rests under intermediate storage of the insulating film 13, the edge region 18 extends to the top of the lid part 15.

The lower part 14 has a circumferential wall 19, whose upper portion 20 engages over the lid part 15. The upper portion 20 is bent radially inwardly so that it presses the lid member 15 on the spacer ring 17 and this on the peripheral shoulder 16.

Lower part 14 and cover part 15 are made of electrically conductive material in the embodiment shown, which is why the cover 15 is provided around extending insulating film 13 which extends inside the housing 12 parallel to the cover member 15, laterally between the wall 19 and the cover part 15 is guided upward and with its edge region 18 facing upward.

The upper portion 20 of the wall 19 lies flat on the edge region 18 of the insulating film 13, and pushes it toward the top 21 of the cover part 14. The at its edge region 18 thereby radially inwardly folded, rigid insulating film 13 is thereby in its edge region 18th wavy and forms wrinkles, whereby it exerts a back pressure on the upper portion 20, so that edge region 18 and upper portion 18 extend to the top 21 at an angle W, which is about 30 °.

By this construction, the edge portion 18 is above over the upper portion 20 via.

On the upper side 21 of the cover part 15, a further insulating cover 22 is provided, which extends radially outwards to the edge region 18 of the insulating film 13.

Despite this double seal, so to speak, the folds of the edge region 18 can not be reliably sealed in every manufacturing process, so that it is ensured in each case that no contaminants can enter the interior of the switch 10 in the region of the angle W.

The housing 12 is therefore usually protected against the entry of impurities by an additional seal, wherein it can not be ruled out that the coating enamel used in this case penetrates into the housing 12.

This situation means that in the production of the known switch 10 'a costly follow-up is required, in the course of which rejects repeatedly identified and discarded.

On an inner side 23 of the cover part 15, a stationary mating contact 24 is arranged, with which a movable contact part 25 supported by the switching mechanism 11 cooperates.

The rear derailleur 11 comprises a spring snap-action disc 26, which is permanently clamped with its edge 27 between the spacer ring 17 and the shoulder 16, so that it produces a permanent electrically conductive connection there.

Below the spring snap-action disc 26, that is on its side facing away from the stationary counter-contact 24 side, a bimetal snap-action disc 28 is provided, which has two geometric temperature positions, the in Fig. 1 shown low-temperature position and a high-temperature position, not shown.

The bimetallic snap disk 28 lies with its edge 29 freely above a wedge-shaped, circumferential shoulder 31, which is formed on an inner bottom 32 of the lower part 14.

The lower part 14 has an outer bottom 33, is made with the thermal contact with a device to be protected.

The bimetallic snap disk 28 is supported on a peripheral shoulder 34 of the contact part 25 with its center 35.

The spring snap-action disc 26 is connected to an inner region 36 in its center permanently connected to the movable contact part 25, to which on the pin 30 which projects through the two snap discs 26 and 28, a ring 37 is pressed, on which also the shoulder 34 is formed.

The electrically conductive connected to the top 21 of the cover member 15 stationary counter-contact 24 cooperates with the movable contact part 25 and via this with the inner portion 36 of the spring snap-action disc 26, the mechanically and electrically permanently with the shoulder 16 and via this with the lower part 14 is connected.

The top 21 serves as the first outer contact surface 38, which is indicated by a black area. The outer bottom 33 of the lower part 14 is used in the known switch as a further contact surface, wherein it is also known to use as the second outer contact surface 39, the upper portion 20 of the wall 19.

In the in Fig. 1 shown, closed switching position of the switch 10, the movable contact member 25 is pressed by the spring snap-action disc 26 against the stationary counter-contact 24. Because the electrically conductive spring snap-action disc 26 with its edge 27 is in communication with the lower part 14, an electrically conductive connection between the two outer contact surfaces 38, 39 is made.

If now the temperature inside the switch 10 increases beyond the response temperature of the bimetallic snap disk 28, then it works from the in Fig. 1 shown convex configuration in a concave configuration in which its edge 29 in Fig. 1 moved upwards so that it comes from below into contact with the edge 27 of the spring snap-action disc 26.

The bimetallic snap disk 28 presses with its center 35 on the shoulder 34 and thus lifts the movable contact part 25 from the stationary counter contact 24.

The spring snap-action disc 26 may be a bistable spring washer, which is geometrically stable even in the open position of the switch, so that the movable contact member 25 does not come back into contact with the stationary counter contact 24 even if the edge 29 of the bimetallic snap disk 28 no longer presses against the edge 27 of the spring snap-action disc 26.

If now the temperature inside the switch 10 is lowered again, then moves the edge 29 of the bimetallic snap disk 26 down and comes into abutment with the wedge-shaped shoulder 31. With its center 35, the bimetallic snap disk 26 then presses from below against the spring snap-action disc 26 and pushes them back into their other geometrically stable position, in accordance with Fig. 1 the movable contact member 25 presses against the stationary mating contact 24.

In the present embodiment, the rear derailleur 11 in addition to the bimetallic snap disk 28, the current-conducting spring snap disk 26, wherein in the rear derailleur 11, only the bimetallic snap disk 28 may be provided, which then clamped with its edge 29 under the rotating ring 17 would be and lead the stream.

It is also possible to arrange the bimetal snap-action disc 28 above the spring snap-action disc 26.

In Fig. 2 is the development of the switch 10 'according to the invention Fig. 1 shown, wherein the new switch 10 is cut only cut in the upper section.

The upper portion 20 of the peripheral wall 19 is at the switch 10 from Fig. 2 bent inwardly so that a continuously curved edge 41 is formed, which rests with its end face 42 on the edge region 18 of the insulating film 13. When bending the upper portion 20, the end face 42 is so in contact with the edge region 18 arrives that this is pressed to the top of the cover member 15, so it applies more tightly to the cover 22, as this at the switch off Fig. 1 the case is.

Compared to the lower portion of the peripheral wall 19, the upper portion 20 in the embodiment of Fig. 2 bent over almost 180 °, so that the curved edge 41 in cross section looks like a U-shaped bead.

However, according to the invention it is also possible to bend over the upper portion 20 by less than 180 °, as long as a curved edge 41 is formed, wherein it is particularly preferred if even then the end face 42 comes into contact with the insulating film 13.

By corresponding bending of the upper portion 20 of the peripheral wall 19 of the curved edge 41 penetrates with its end face 42 even in the edge region 18 of the insulating film 13, so that a particularly good sealing of the interior of the switch 10 takes place.

The in Fig. 1 still accessible from the outside angle range W is at the switch off Fig. 2 now protected by the curved edge 41 completely from the entry from dirt.

In the in Fig. 2 embodiment shown is below the edge portion 18 of the insulating film 13 nor the cover 22, which could also be dispensed with.

In the event that the lower part 14 or cover part 15 are made of insulating material, can also be dispensed with the insulating film 13, the sealing effect by the curved edge 41 is then achieved in conjunction with the cover 22.

In the embodiment according to Fig. 2 For example, the edge region 18 of the insulating film 13 can also be turned over only slightly on the upper side of the cover part 15 so that it ends within the U-shaped bead of the edge 41 so that the end face 42 comes into contact with the cover film 22 past the edge region 18 ,

Regardless of the fact that the formation of the curved edge, the interior of the switch 10 is more effectively protected from the ingress of contaminants than the switch according to Fig. 1 , the switch points according to Fig. 2 a further advantage, which is additionally or independently of the sealing effect of the curved edge 41 can be realized.

The curved edge 41 spans a plane 43 which lies parallel to a plane 44 which spans the first contact surface 38 on the upper side of the cover part 15.

The indicated at 45 distance between the two planes 43 and 44 is so small that it can be compensated by the solder paste in SMT assembly. In the embodiment shown, the distance 45 is less than 0.3 mm. In this context, it should be noted that the switch 10, depending on the design has a diameter between 8 and 20 mm and has a height of 6 to 15 mm.

In Fig. 3 is the assembly of the switch 10 off Fig. 3 shown on a printed circuit board 46, to which the switch 10 is placed with its lid part 15 on the circuit board 46.

On the circuit board, an annular soldering surface 47 is provided, which corresponds to the diameter of the curved edge 41. Within the annular soldering surface 47, a soldering surface 48 is centrally provided, which serves to contact the first contact surface 38.

Between the annular soldering surface 47 and the central soldering surface 48, a vent hole 49 is provided in the printed circuit board 46.

As usual with SMD mounting, solder pastes 51, 52 are applied on the annular soldering surface 47 and on the central soldering surface 48, whereupon the switch is thus placed upside down on the printed circuit board 46, so to speak, that the soldering paste 51 between the annular soldering surface 47 and the curved edge 41 and the solder paste 52 between the central soldering surface 48 and the first outer contact surface 38th

After the usual reflow technique, the solder pads 47, 48 and the outer contact surfaces 38, 39 are now soldered together.

In this case, a space 53 is formed between the printed circuit board 46 and the curved edge 41, which is vented through the vent hole, so that no mechanical disturbing forces occur during soldering.

In Fig. 3 It can be seen that the curved edge 41 together with the annular soldering surface 47 and the solder paste 51 therebetween causes a seal of the top of the switch 10, so that no impurities can reach the top of the switch 10 laterally, which then between the curved edge 41 and the protective film 13 could penetrate into the interior of the switch 10.

The curved edge 41 thus provides for SMD mounting of the switch 10 for a protection of the interior of the switch 10 against the entry of impurities, even if the curved edge 41 is not sealingly in contact with the insulating film 13 and / or the cover 22.

While in the Fig. 1 . 2 and 3 a switch 10 or 10 'is shown, in which the temperature-dependent switching mechanism carries a movable contact part, which is in contact with a stationary mating contact, which is contacted by the cover part through outwardly to the first outer contact surface shows Fig. 4 an alternative embodiment of a switch 10, in which on a plastic cover part 55 two stationary mating contacts 56, 57 are arranged.

The two stationary mating contacts 56, 57 cooperate with a current transfer member 58, which differs from the in Fig. 4 not shown, temperature-dependent switching mechanism is moved.

The two stationary mating contacts 56, 57 cooperate with two outer contact surfaces 61, 62, with which they are in Fig. 4 not shown manner are electrically connected.

This switch can also be mounted on a printed circuit board in an SMT manner, two soldering surfaces for the contact surfaces 61, 62 then being provided on the printed circuit board in order to electrically connect the switch.

Further, an annular soldering surface for the curved edge 41 is provided to mechanically fix the switch. If the curved edge is connected along its entire circumference with an annular soldering surface, the curved edge 41 also serves as a barrier against the entry of impurities, as already described above.

Because the cover part 55 is here made of an insulating plastic, no insulating film is required between the cover part 55 and the lower part, although of course this can also be provided here.

It is important, however, if on the upper side of the plastic cover part 55, a protective film 63 is arranged, which serves the sealing between the lower part and the cover part, wherein the curved edge 41 with its end face 42 can rest on the protective film 63 sealingly.

Claims (23)

1. Temperature-dependent switch comprising a housing (12) which has a cover part (15) with a top side (21) and a bottom part (14) with a peripheral wall (19), wherein the upper section (20) of the peripheral wall (19) engages over the cover part (15), comprising at least one first outer contact area (38, 61) which is arranged on the top side (21) of the cover part (15), at least one second outer contact area (39, 62) which is provided on the outside of the housing (12), and at least one protective film (13, 22, 63) which is arranged at least on the top side (21) of the cover part (15), wherein the upper section (20) of the peripheral wall (19) of the bottom part (14), which upper section engages over the cover part (15), holds the cover part (15) on the bottom part (14) with the interposition of the protective film (13, 22, 63), and comprising a temperature-dependent switching mechanism (11) which is arranged in the housing (12) and, depending on its temperature, establishes or opens an electrically conductive connection between the first and the second outer contact area (38, 39; 61, 62),
   characterized in that the upper section (20) of the peripheral wall (19) of the bottom part (14), which upper section engages over the cover part (15), is designed as a continuously curved rim (41) which, by way of its end side (42), presses onto the protective film (13, 22, 63).
2. Switch according to Claim 1, characterized in that the end side (42) penetrates the protective film (13, 22, 63).
3. Switch according to Claim 1 or 2, characterized in that the upper section (20) of the peripheral wall (19) is bent over through at least 90°, preferably at least 120°.
4. Switch according to one of Claims 1 to 3, characterized in that the curved rim (41) is designed as a bead of U-shaped cross section.
5. Switch according to one of Claims 1 to 4, characterized in that the curved rim (41) defines a first plane (43), the at least one contact area (38) on the top side (21) defines a second plane (44) which is parallel to the first plane (43), and the first and the second plane (43, 44) are at a distance (45) from one another, which distance allows mounting of the switch (10) on a printed circuit board (46) using SMT, preferably is smaller than 2 mm.
6. Switch according to one of Claims 1 to 5, characterized in that the at least one protective film (13, 22, 63) comprises an insulating film (13) which runs on the inside in the switch (10) between the bottom part (14) and the cover part (15) and laterally between the peripheral wall (19) of the bottom part (14) and the cover part (15) and, by way of its rim region (18), is turned over onto the top side (21) of the cover part (15).
7. Switch according to one of Claims 1 to 6, characterized in that the at least one protective film (13, 22, 63) comprises a covering film (22) which lies on the top side (21) of the cover part (15).
8. Switch according to Claims 6 and 7, characterized in that the covering film (22) extends to below the rim region (18) of the insulating film (13).
9. Switch according to one of Claims 1 to 8, characterized in that the protective film (13, 22, 63) consists of polyimides, preferably of aromatic polyimides, or aramid paper.
10. Switch according to one of Claims 1 to 9, characterized in that the second outer contact area (39) is arranged on the curved rim (41).
11. Switch according to Claim 10, characterized in that the switching mechanism (11) supports a moving contact part (25) which interacts with a stationary mating contact (24) which is arranged on an inner side (23) of the cover part (15) and interacts with the first outer contact area (38) which is arranged on the top side (21).
12. Switch according to one of Claims 1 to 9, characterized in that the second outer contact area (62) is arranged on the top side (21) of the cover part (15).
13. Switch according to Claim 12, characterized in that the switching mechanism (11) supports a current transfer element (58) which interacts with two stationary mating contacts (56, 57) which are arranged on an inner face (23) of the cover part (15) and each of which interacts with one of the two outer contact areas (61, 62) which are arranged on the top side (21).
14. Switch according to one of Claims 1 to 13, characterized in that the cover part (15) is produced from an electrically conductive material.
15. Switch according to one of Claims 1 to 14, characterized in that the bottom part (14) is produced from an electrically conductive material.
16. Switch according to one of Claims 1 to 15, characterized in that the switching mechanism (11) has a bimetallic part (28).
17. Switch according to one of Claims 1 to 16, characterized in that the switching mechanism (11) has a spring-mounted snap-action disc (26).
18. Electronic circuit comprising at least one temperature-dependent switch (10) according to one of Claims 1 to 17 which is mounted on a printed circuit board (46), characterized in that the switch (10) lies, by way of its cover part (15), on the printed circuit board (46).
19. Electronic circuit according to Claim 18, characterized in that the first outer contact area (38, 61) faces a first soldering area (48), which is provided on the printed circuit board (46), and is soldered to the said first soldering area, and in that the curved rim (41) faces a second soldering area (47), which is provided on the printed circuit board (46), and is soldered to the said second soldering area.
20. Electronic circuit according to Claim 19, characterized in that the second soldering area (47) is an annular soldering area, and the curved rim (41) is continuously soldered, along its entire periphery, to the second soldering area (47).
21. Electronic circuit according to Claim 19 or 20, characterized in that the second outer contact area (39) is arranged on the curved rim (41).
22. Electronic circuit according to Claim 19 or 20, characterized in that the second outer contact area (62) is arranged on the top side (21) of the cover part (15) and is soldered to a third soldering area which is provided on the printed circuit board (46).
23. Electronic circuit according to one of Claims 19 and 22, characterized in that a ventilation bore (49) is provided in the printed circuit board (46), which ventilation bore issues into a space (53) which is formed between the printed circuit board (46) and the curved rim (41).

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