EP3024010B1 - Temperature-dependent switch - Google Patents

Description

The present invention relates to a temperature-dependent switch, which has a temperature-dependent switching mechanism and a housing receiving the switching mechanism, wherein on the outside of the housing a first and a second connection surface for the electrical connection of supply lines are provided, the temperature-dependent switching mechanism as a function of its temperature between the two connection surfaces produces or opens an electrically conductive connection, and at least one of the connection surfaces is cohesively attached to a supply line with its inner end, wherein the inner end of the feed line is welded by at least one welding point to the at least one connection surface.

Such a switch is from the EP 0 651 411 A1 known.

Such temperature-dependent switches are also widely known from the prior art; see eg the DE 10 2009 030 353 B3 , They are used to protect electrical equipment such as hair dryers, lye pump motors, irons etc. from overheating and / or high current.

For this purpose, the known temperature-dependent switches are electrically connected in series with the device to be protected in the supply circuit, so that the operating current of the device to be protected flows through the temperature-dependent switch. The switch is also attached to the device to be protected so that it adopts the temperature of the device to be protected.

The known temperature-dependent switches comprise a temperature-dependent switching mechanism which, depending on its temperature, opens or closes an electrical connection between two connection surfaces provided outside the housing of the switch. For this purpose, a bimetallic part is usually provided in the derailleur, which deforms abruptly from its low-temperature position into its high-temperature position when reaching its switching temperature and usually lifts a movable contact part of a fixed contact part.

The fixed contact part is connected to one of the two connection surfaces, while the movable contact part interacts with the second connection surface either via the bimetal part or a snap disk or spring associated with the bimetal part.

There are also constructions known in which the bimetallic carries a contact bridge, which directly establishes an electrical connection between two pads.

Examples of such temperature-dependent switches are mentioned in the opening paragraph DE 10 2009 030 353 B3 , of the DE 41 39 091 C2 , of the DE 198 16 807 A1 , of the DE 26 44 411 A and further intellectual property rights of the applicant, so that reference may be made to these patents for further details.

When using the known switches must often be ensured that the switches are electrically isolated from the electrical device to be protected so that it does not come to unwanted short circuits.

The known switch namely have an electrically conductive housing lower part, which is designed as a pot and receives the temperature-dependent switching mechanism. The electrically conductive housing lower part is closed by a likewise electrically conductive cover part, which is fixed with the interposition of an insulating film on the housing lower part by crimping the edge of the lower part to the cover part. The first connection surface is provided on the cover part, while the second connection surface is provided on the bottom, the side wall or the edge of the housing lower part holding the cover part.

With these two pads now leads, usually either flexible leads or rigid connection lugs, materially connected, so soldered or welded, the strands or terminal lugs then serve the further interconnection of the known temperature-dependent switch.

The initially mentioned EP 0651 411 A1 describes a temperature-dependent switch with a lid and a lower part made of metal, are welded to the connecting strands or terminal lugs, which is mentioned as a method electro-spot welding.

The prefabricated switches thus provided with strands or terminal lugs are then provided with a cap or a shrink cap in order to electrically isolate the switches from the outside.

In the from the DE 41 39 091 C2 Known switches, the leads are designed as relatively rigid sheets, which are riveted with their inner ends to the pads. Thereafter, the switch with the riveting and the inner ends of the sheets is overmolded with a low pressure epoxy resin. By riveting and encapsulation with the thermoset to ensure a firm and mechanically durable durable connection between the sheets and the housing of the switch on which the pads are formed.

In the known switch, however, has the disadvantage that the riveting of the sheets is time-consuming and carries the risk that it comes in the riveting process to deformation of the housing. Because of the extremely small dimensions of the temperature-dependent switch but the slightest deformation of the housing can cause the switch no longer reliably closes and / or opens.

Furthermore, it is disadvantageous that the riveting must be done before the final assembly of the housing. This then results in the problem that because of the already attached to the cover part connecting lug, the edge of the lower part can not be easily crimped onto the patch lid part. For the manufacture of this known switch, therefore, a different manufacturing process must be used as for switches in which the terminal lugs or leads are connected to the fully assembled and tested switch electrically and mechanically.

In the from the above-mentioned DE 10 2009 030 353 B3 known switches are used as leads connecting lugs, which are soldered with their inner ends to the pads, the free ends of the terminal lugs are designed as plug-in connections. The switch and the inner ends of the terminal lugs are then surrounded together with an insulating, sintered protective layer.

By co-sheathing or enveloping the switch, the pads and the inner ends of the terminal lugs with the protective layer, a structurally stable connection is made, which then mechanically sufficient is resilient without the quality of the electrical connection is impaired.

In particular, when the free ends of the leads with lines or external connection points, for example. Must be welded to be protected devices, however, may arise in the later assembly of the switch in or on the device to be protected problems with the solder joints. These are often not so heat resistant that they survive the subsequent welding of the free ends of the terminal lugs always unscathed.

The solder joints may become soft due to the strong heating of the terminal lugs during the welding operations, so that there is a risk that the terminal lugs change their geometric position and / or the electrical connection between the inner ends of the terminal lugs and the pads on the housing of the switch suffers, possibly even interrupted, the solder joint is so cold.

The DE 10 2009 030 353 B3 However, it also mentions that the inner ends of the terminal lugs can also be welded to the connection surfaces. However, the welding tests previously performed at the applicant were not successful because the heat development leads directly to the lid part to the fact that the movable contact part and the fixed contact part welded together or at least as far changed in their geometry that the so-assembled switch no longer or at least not switch more reliably. Furthermore, the heat entering the interior of the housing during the welding operation may cause the domes to be affected, thereby unduly altering their required switching characteristics.

Another disadvantage of this known switch can be seen in the complex final manufacturing step, in which the sintered protective layer is applied.

Against this background, the present invention has the object, the known switch in such a way that the above-mentioned disadvantages are reduced or avoided altogether.

In the known switch, this object is achieved in that the inner end of the lead is welded by one-sided spot welding to the at least one pad, and the inner end of the lead has at least two tabs, each of which welded with a weld point to the at least one pad is.

Single-sided spot welding, also referred to as parallel gap welding in the English-speaking world, is a form of conductive resistance welding in which the two welding electrodes are welded from one side, e.g. be brought into contact with a surface of one of the two parts to be joined. The welding current thus flows from one of the two welding electrodes partly through the upper part and partly through the lower part and then back into the other welding electrode. The two parts are thus joined together by two "associated" welding points.

It is also known to place a welding electrode on the upper side of the upper part and the second welding electrode next to the upper part on the upper side of the lower part, ie on the surface on which the upper part rests. In this way, the two parts are connected only by a welding point.

In this way, parts can be welded together, of which only the upper part and possibly its bearing surface on the lower part of the welding electrodes are accessible.

One-sided resistance welding is described for example in US Pat DE 10 2007 020 211 A1 , of the US 3,478,190 A and the "Resistance Welding - Parallel Gap Welding Basics" datasheet , which can be downloaded from the www.microjoining.com website.

The inventors of the present application have now recognized that this form of resistance welding, contrary to expectations, is also suitable for welding leads to housings of temperature-dependent switches, after the switches have already been completely assembled.

The thereby flowing through a portion of a wall of the housing welding current does not damage the switch, but ensures a mechanically strong, electrically safe and temperature-resistant connection between the supply line and the pad.

The supply line can therefore now be formed as a terminal lug, which can be welded at its free end with lines or contact areas, without the connection of the inner end is adversely affected by the switch. In particular, it is no longer necessary to surround the switch connected to the supply lines with, for example, a sintered protective layer, in order to ensure a connection which is structurally so stable that it can subsequently be subjected to sufficient mechanical load.

The free end of the invention according to the invention welded to the switch terminal lug can also be designed as a crimp connection, plug connection or for Surface Mounted Technology (SMT) connection. The manipulations required in the final assembly of the switch on the device to be protected then also lead to knowledge of the inventors also not that the connection of the inner end of the terminal lug is affected by the switch.

The new switch can be provided, for example, in accordance with the invention with a terminal lug on the lid part, which is angled and provided at its free end with a contact surface for SMT, that the switch as Surface Mounted Device (SMD) according to the Reel Technik ( Belt and spool) and can be applied to a printed circuit board with pick and place SMD placement machines and mounted there and, for example, contacted by the reflow method.

The bottom of the lower part of the housing then serves directly as a second connection surface, which is contacted directly on the circuit board, thus providing the second supply line to the switch. This connection method is now available according to the invention, because the new switch for the reasons mentioned above does not need to be provided with a protective layer, so that the bottom of the switch can be mounted directly on a circuit board. The connection lug serves to connect the other connection surface to the circuit board.

If the new switch is not further processed as an SMD, it can be provided with an insulating sheath, which, however, does not have to provide a mechanically strong stabilization of the connection between the supply line and the housing. As a shell, therefore, a cheap, quick and easy to install shrink cap can be used.

The above-described possibilities of further processing of the new temperature-dependent switch were previously not possible for the reasons mentioned above.

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

In this case, it is preferred if the two tabs extend away from one another and are welded to the at least one connection surface via an associated pair of spot welds, and more preferably the two tabs extend parallel to one another, are separated from one another by a gap and have an associated one Preferably, the inner end of the lead has four paired tabs, each of which is welded to the at least one pad with a weld point, and further preferably each pair of tabs has a gap, which separates the tabs, and the two pairs point away from each other.

In these measures, it is advantageous that, depending on the geometric, electrical and mechanical requirements, a connection with 1, 2 or 4 welds can be made.

The gap between two parallel tabs allows a particularly good connection, because the welding current flows largely from the one tab in the wall of the housing of the switch, there through the bottom of the base or the lid part and then passes into the second tab. In other words, only a small part of the welding current flows from one to the other tab through the inner end of the supply line. The gap extends between the two tabs over a length which preferably corresponds at least to the width of the inner end transverse to the gap. The width of the gap corresponds approximately to twice the material thickness of the inner end of the supply line.

Further, it is preferred if the supply line is designed as a pigtail or as a terminal lug.

The inventors have recognized that, contrary to expectations, both connection lugs and connecting leads can be welded to housing of temperature-dependent switches by means of one-sided spot welding.

Furthermore, it is preferred if a series resistance is integrated into the supply line.

Because the supply line is subsequently welded from the outside to a connection surface, a series resistor integrated in the supply line is a simple and cost-effective way of providing an already prefabricated switch, whose housing is already closed, with a current dependency. By the weld connection is provided for a good heat transfer from the series resistor in the housing.

Finally, it is preferred if a self-holding resistor is arranged on the inner end of a first supply line, which is electrically connected at one terminal to the supply line and at its other terminal to a second supply line.

This is a simple and inexpensive way to provide a pre-assembled switch, the housing is already closed, with a self-holding function. Again, the weld joint provides good heat transfer to the interior of the housing. The self-holding resistor can be glued or soldered onto the inner end, for example.

In general, it is preferred if the housing comprises a cover part, on which the first connection surface is formed, and a lower part, at the bottom of which the second connection surface is formed, wherein preferably the supply line comprises a multiply angled connection lug, which at its inner end with the first connection surface is connected and at its free end has a at the level of the second connection surface and extending parallel thereto connecting portion.

The angled terminal lug thus enables the above-described use of the new switch as an SMD component and its mounting on a printed circuit board, on the two juxtaposed connection areas for the terminal portion of the angled terminal lug and thus the first pad of the switch and the bottom of the housing, ie the second pad of the housing can be provided.

In general, it is preferred if the temperature-dependent switching mechanism comprises a bimetallic part, wherein preferably the bimetal in the closed state of the switch is electrically in series between the pads, more preferably the temperature-dependent switching mechanism comprises a spring member which in an application in the closed state of the switch electrically in Row between the pads lies. Alternatively, the derailleur may comprise a contact bridge, the is carried by the bimetal part or the spring part and in the closed state of the switch is electrically in series between the pads.

These are the preferred types of temperature-dependent switches.

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

The bimetal is usually designed as a cantilever spring or as a loosely inserted disc.

If the bimetallic part as in the above-mentioned DE 198 16 807 A1 is designed as a bimetallic spring tongue, so it carries at its free end a movable contact part, which cooperates with a fixed contact part. The fixed contact part is electrically connected to a first outer terminal, wherein a second outer terminal is electrically connected to the clamped end of the bimetallic spring tongue.

Below its response temperature, the bimetallic spring tongue closes the electrical circuit between the two outer terminals by pressing the movable contact part against the fixed contact part.

As the temperature of the bimetallic spring tongue increases, it begins to stretch and deform in a creep until it eventually springs over to its open position, lifting the movable contact portion from the fixed contact portion.

On the other hand, if the bimetallic part is designed as a bimetallic disc, it generally interacts with a spring snap-action disc which carries the movable contact part which cooperates with the fixed contact part in the manner described above. The spring snap disc is supported by its edge on an electrode which is connected to the second external connection. Such a switch is for example in the DE 21 21 802 A or the DE 196 09 310 A1 described.

Below its response temperature, the bimetallic disc is loosely inserted, so it is mechanically unloaded. The contact pressure between the fixed and movable contact part and thus the electrical connection between the two outer terminals are provided via the spring snap disk. Increases the temperature of the known temperature-dependent switch, so the bimetal passes through a creep phase in which it gradually deforms until it then suddenly jumps into its open position in which it acts on the Federschnappscheibe that it lifts the movable contact part of the fixed contact part and thus the well-known Switch opens.

In the switch described above with the bimetallic spring tongue, the bimetal part itself is current-flowed, so that it heats up by the current flowing through the switch. In this way, the known switch not only reacts to external temperature increases, it also responds to a high current flow.

Such switches therefore react temperature-dependent and current-dependent.

In contrast, in the switch with bimetallic disc and Federschnappscheibe the bimetallic always energized, so does not heat up by the current flowing, so that switch such switch largely independent of current.

But there are also switches are known in which a bimetallic spring tongue cooperates with a Federschnappteil, which carries the flowing current, so that in these constructions, the bimetallic spring tongue itself carries no electricity. Conversely, switches are also known in which only one bimetallic disc is provided which carries the movable contact part, produces the closing pressure and has current flowing through it.

Finally, temperature-dependent switches with two external terminals are known, which are each connected to a fixed contact part, wherein an electrically conductive contact bridge is provided, which carries the flowing current when it rests against the fixed contact parts.

Such switches with contact bridge are eg in the DE 197 08 436 A1 described. They are intended for applications where high rated currents through flow the switch, which would lead to a heavy load or self-heating of a current-carrying Federschnappteils or Bimetallteils.

The contact bridge is supported by a Federschnappscheibe, which cooperates with a bimetallic disc. If the bimetal disc is below its response temperature, it is exposed without mechanical load in the switch, the spring snap disc presses the contact bridge against the fixed contact parts, so that the circuit is closed. When the temperature increases, the bimetallic disc snaps from its force-free closed position to its open position in which it works against the spring snap disc and lifts the contact bridge of the fixed contact parts.

Further 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 the respective combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Fig. 1

in einer schematischen, geschnittenen Querschnittsdarstellung eine Ausführungsform eines temperaturabhängigen Schalter, der erfindungsgemäß eingesetzt werden kann;

Fig. 2

eine schematische Darstellung für ein erstes Beispiel des einseitigen Punktschweißverfahrens ;

Fig. 3

eine schematische Darstellung für ein zweites Beispiel des einseitigen Punktschweißverfahrens ;

Fig. 4

eine schematische Darstellung für ein drittes Beispiel des einseitigen Punktschweißverfahrens ;

Fig. 5

den Schalter aus Fig. 1 in Ansichten von unten, von der Seite und von oben, mit gemäß dem Verfahren aus Fig. 3 angeschweißten Anschlusslitzen;

Fig. 6

eine Darstellung wie in Fig. 5, jedoch mit gemäß dem Verfahren aus Fig. 4 angeschweißten Anschlusslitzen;

Fig. 7

den Schalter aus Fig. 1 in Ansichten von unten, von der Seite und von oben, mit gemäß dem Verfahren aus Fig. 2 angeschweißter unterer Anschlussfahne, und mit gemäß dem Verfahren aus Fig. 4 angeschweißter oberer Anschlussfahne;

Fig. 8

eine Darstellung wie in Fig. 7, jedoch mit einen weiteren Ausführungsbeispiel für die untere Anschlussfahne;

Fig. 9

den Schalter aus Fig. 1 in perspektivischer Ansicht von oben und eine gemäß dem Verfahren aus Fig. 4 anzuschweißende obere Anschlussfahne in perspektivischer Ansicht, in einem Ausführungsbeispiel für SMD-Montage;

Fig. 10

Schalter und Anschlussfahne aus Fig. 9 in Seitenansicht und Draufsicht; und

Fig. 11

den Schalter aus Fig. 8, bei dem auf die untere Anschlussfahne eine PTC-Scheibe aufgeklebt wurde, um den Schalter mit einer Selbsthaltefunktion zu versehen.

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

Fig. 1

in a schematic, sectional cross-sectional view of an embodiment of a temperature-dependent switch, which can be used according to the invention;

Fig. 2

a schematic representation of a first example of the one-sided spot welding process;

Fig. 3

a schematic representation of a second example of the one-sided spot welding process;

Fig. 4

a schematic representation of a third example of the one-sided spot welding process;

Fig. 5

the switch off Fig. 1 in views from below, from the side and from above, with according to the method Fig. 3 welded-on pigtails;

Fig. 6

a representation like in Fig. 5 , but with according to the method Fig. 4 welded-on pigtails;

Fig. 7

the switch off Fig. 1 in views from below, from the side and from above, with according to the method Fig. 2 welded lower terminal lug, and with according to the method Fig. 4 welded upper connection lug;

Fig. 8

a representation like in Fig. 7 but with a further embodiment for the lower terminal lug;

Fig. 9

the switch off Fig. 1 in a perspective view from above and one according to the method Fig. 4 to be welded upper terminal lug in perspective view, in one embodiment for SMD assembly;

Fig. 10

Switch and connection lug off Fig. 9 in side view and top view; and

Fig. 11

the switch off Fig. 8 , in which a PTC disc was glued to the lower terminal lug to provide the switch with a self-holding function.

In Fig. 1 is denoted by a temperature-dependent switch 10, which comprises an electrically conductive, pot-like lower part 11 which is closed by an electrically conductive cover part 12 which is held with the interposition of an insulating film 13 by a flanged edge 14 on the housing lower part 11.

In the housing 10 formed by the lower part 11 and the cover part 12 of the switch 10, a temperature-dependent switching mechanism 15 is arranged, which comprises a Federschnappscheibe 16 which carries a movable contact member 17 centrally, on which a freely inserted bimetallic disc 18 is seated.

The Federschnappscheibe 16 is supported on a bottom 19 inside of the lower part 11, which is made of electrically conductive material.

The movable contact part 17 is in contact with a fixed contact part 20, which is provided on an inner side 21 of the cover part 12, which is also made of metal.

In this way, the temperature-dependent switching mechanism 15 in the in Fig. 1 shown low-temperature position an electrically conductive connection between the cover part 12 and the lower part 11 forth, the operating current on the fixed contact part 20, the movable contact member 17 and the spring snap disk 16 flows.

The cover part 12 serves with its surface 24 as the first connection surface 22, and the lower part 11 serves with its bottom 25 as the second connection surface 23. At these connection surfaces 22, 23, connecting litz wires or connection lugs can be attached.

It is alternatively also possible, instead of the spring snap disc 18 directly insert a bimetallic, that the movable contact member 17 carries and generates the closing pressure and thus when the switch 10 is closed, the operating current.

Other constructions of the temperature-dependent switching mechanism 15 are conceivable, for example, a cantilever clamped on one side or a cantilevered snap spring, which works against a bimetal.

Furthermore, it is possible to arrange the two connection surfaces 22, 23 next to one another on the cover part 12 and to the switching mechanism 15 with a contact bridge provided, which is supported by the bimetal part or the spring part and in the closed state of the switch 10 is electrically in series between the pads 22, 23.

In the switch 10 off Fig. 1 is the cover part 12 made of electrically conductive material, but it can also be made of insulating material or PTC thermistor ceramic. In these cases, the pad 22 is formed by a layer of metal disposed on the surface 24, which is plated through the lid member 12 to the fixed contact portion 20. By the cover part of PTC material, the switch 10 is replaced in a conventional manner, a self-holding function.

Consequently, it does not matter for the advantages according to the invention whether the switch 10 is as in FIG Fig. 1 or is formed as disclosed in the publications mentioned above.

Increases in the switch 10 off Fig. 1 the temperature of the bimetallic disc 18 beyond its response temperature, so it snaps from the in Fig. 1 shown convex position in its concave position in which it lifts the movable contact member 17 against the force of the spring washer 16 of the fixed contact member 20 and thus opens the circuit.

Such a temperature-dependent switch 10 is for example from the DE 196 23 570 A1 known.

After the switch 10 has been assembled as described above, it can be tested for functionality and compliance with its specification and then temporarily stored until it is used, for example, according to the invention provided with the connection technique.

The switch 10 is then provided with one-sided spot welding with leads, as in principle now in the Fig. 2 to 4 is shown.

In Fig. 2 a first sheet metal part 31 is shown, to which a second sheet metal part 32 is to be welded by means of one-sided spot welding. For this purpose, two welding electrodes 33 and 34 are provided which have a distance indicated at 35 to each other.

The two welding electrodes 33, 34 are placed on the surface 36 of the upper sheet metal part 32, whereupon then a current flows through both the upper sheet metal part 32 and through the lower sheet metal part 31 and leads to the formation of welds, which are indicated at 37 and 38.

With the one-sided spot welding method according to Fig. 2 The two sheet metal parts 31 and 32 are thus connected to each other by an associated pair of welds 37 and 38.

In Fig. 3 a situation is shown where the second welding electrode 34 does not touch on the upper side 36 of the upper sheet metal part 32 but on the upper side 39 of the lower sheet metal part 31, so that only one welding point 37 is generated.

If the distance 35 between the two welding electrodes 33 and 34 can not be so large due to geometrical conditions that a sufficient proportion of the flowing welding current flows through the lower sheet metal part 31, the upper sheet metal part 32 is provided with a gap 41, as in Fig. 4 is shown. The upper sheet metal part 32 then has two mutually parallel tabs 42, 43, which are separated by the gap 41 from each other. The gap 41 in this case has a length transversely to the distance 35, which is so large that the welding current flows around the gap 41 only to a small extent.

Now, when the welding electrodes 33 and 34 are placed on the top 36 of the upper sheet metal part 32, the welding current flows predominantly through the lower sheet metal part 31, which leads to the formation of the associated welds 37 and 38.

That in the Fig. 2 to 4 Briefly described, one-sided spot welding method is known in principle in the prior art, but it has not been used to weld leads to pads on housings of temperature-dependent switches.

In Fig. 5 is in a first embodiment of the temperature-dependent switch 10 off Fig. 1 top in bottom view, center in side view and bottom in plan view.

To the upper pad 22 and the lower pad 23 each have a pigtail 46 and 47 welded, the welding according to the above with reference to Fig. 3 described method, so that in each case only one welding point 37 connects the stripped inner end 48 and 49 of the connecting strands 46 and 47 with the housing of the switch 10.

In Fig. 6 is in a presentation like Fig. 5 the switch 10 is shown, are soldered to the again two connecting leads 46 and 47.

The stripped inner ends 48, 49 of the connecting strands 46 and 47 now run apart fork-shaped, so that two tabs 51 and 52 or 53 and 54 form, each by a weld point 37 and 38 to the corresponding pads 22 and 23rd are welded. The welds 37 and 38 form here an associated pair, as determined by the Fig. 2 and 4 has been described.

In Fig. 7 is comparable in a representation too Fig. 6 the temperature-dependent switch 10 is shown, wherein the connecting wires 46 and 47 are not welded directly to the connection surfaces 22 and 23, but are connected to terminal lugs 55 and 56 made of sheet metal. The connection of the connecting strands 46 and 47 with the terminal lugs 55 and 56, for example, by crimping or done by plugging. In Fig. 7 At 57 and 58, corresponding crimping ends of the terminal lugs 55 and 56 are shown.

The lower terminal lug 56 has at its inner end 59 two tabs 61 and 62 extending in opposite directions away from each other and welded to the terminal surface 23 via a pair of welds 37 and 38.

The distance between the welding points 37 and 38 is here so large that the situation of Fig. 2 arises where a portion of the welding current flows through the lower sheet metal part 31, in this case through the lower housing part 11.

The upper connecting plate 55, however, has at its inner end 60 two mutually parallel tabs 63 and 64, which are separated by a gap 65 from each other. The tabs 63 and 64 are welded by welds 37 and 38 with the pad 22.

The connection according to Fig. 7 below will therefore according to the basis of Fig. 4 prepared method described.

Of course, it is also possible to use the connection plate 55 for the connection of the connecting strand 46 to the connection surface 23.

Fig. 8 shows an embodiment analogous to that of Fig. 7 , only the lower pigtail 47 is now connected via a connecting lug 66 with the connecting surface 23, which has four paired tabs 67, 68 at its inner end 70, wherein the tabs 67, 68 of each pair define a gap 69 between them and the two pairs diametrically away from each other.

Each pair of tabs 67, 68 is over an associated pair of welds 37, 38, which according to the Fig. 4 described, one-sided Spot welding are created, connected to the corresponding pad 23.

The extent described mechanical and galvanic, cohesive connection of the connecting strands 46 and 47 either directly or via terminal lugs 55, 56 and 66 is mechanically stable and temperature resistant so that the compound not only the crimping or conventional manipulation of the connecting strands 46 and 47 survives In addition, the terminal lugs 55, 56, 66 can also be welded directly to connecting strands or other connection surfaces on a device to be protected, without the weld spots 37, 38 becoming "soft", ie their mechanical or electrical connection is deteriorated.

For this reason, it is now also possible for the first time to configure the temperature-dependent switch 10 like an SMD component, so that it can be positioned with a conventional SMD placement machine and then contacted.

For this purpose, according to Fig. 9 a multiple, here quadruple angled terminal lug 71 having at its inner end 72 two tabs 73 and 74 which are separated by a longitudinally extending therebetween gap 75 from each other, welded to the pad 22, as shown in Fig. 7 already shown for the terminal lug 55.

The terminal lug 71 has at its free end 76 a at the height of the pad 23 and extending parallel to this connection portion.

Between the inner end 72 and the free end 76 of the terminal lug 71, three sheet metal sections 77, 78, 79 are arranged, which are angled to each other so that the sheet metal portion 77 initially extends at about 45 ° to the inner end 72 upwards, the sheet metal section 78 then again parallel to the inner end 72 and the outer end 76 extends, and the sheet metal portion 77 is then angled downwards at 45 °, so that it connects the sheet metal portion 78 with the connection portion.

In Fig. 10 the switch 10 is off Fig. 9 with the terminal lug 71 at the top in side view and at the bottom in plan view.

The switch 10 is mounted on a printed circuit board 81, so that now with a conventional reflow process, both the pad 23 and the free end 76 can be connected to corresponding contact areas 82, 83, 84 in the circuit board 81. The terminal lug 71 ensures both the electrical connection of the pad 22 and the mechanical support of the switch 10th

Due to the angled terminal lug 71, when the switch 10 is mounted on the circuit board, both a sufficient air gap indicated at 85 and a sufficient creeping distance indicated at 86 are maintained.

The material of the terminal lugs 55, 56, 66 and 71 is for example German silver with a thickness of 0.3 mm, wherein the gaps 65, 69, 75 have a width of 0.5 mm and a length of 2 to 4 mm. The material of the lower part 11 and the lid part 11 is, for example, steel of the type DC0.1 and can be silvered entirely or only in the areas serving as connection surfaces 22 and 23.

The material of the lower terminal lugs 56 and 66 may also consist wholly or partly of a resistance alloy, so that a series resistor 92 is integrated into this supply line, which in Fig. 8 is indicated by a dashed area. The terminal lug 56, 66 thus has a low electrical resistance, so that the terminal lug 56 or 66 heats up when the current flows. This results in too high amperage to such a heating of the lower part 11 that the switch 10 already opens due to the excessive current, even before the device to be protected has heated itself so far that this leads to such a heating of the switch, that this opens as a result of the transmitted heat from the device. The lower connection lug 56 or 66 thus ensures current-dependent switching.

Additionally or alternatively, outside on the lower terminal lug 56 or 66, a self-holding resistor can be applied, as in Fig. 11 very schematically for the switch 10 off Fig. 8 is shown in Fig. 11 is shown in side view.

On the lower terminal lug 66 is an above in Fig. 11 glued PTC disc 87 shown enlarged, which is thereby electrically connected with its upper terminal 89 to the lower Anschlußlitze 47. Via a schematically indicated electrical connection 88, the PTC plate 87 is electrically conductively connected at its lower terminal 91 to the upper connecting lug 55 and thus to the upper pigtail 46. In this way, the self-holding resistor formed by the PTC plate 87 is electrically connected in parallel with the switching mechanism 15.

When the switch 10 is open, the self-holding resistor accepts a part of the operating current in a manner known per se and keeps the switching mechanism 15 at a temperature above the return temperature of the bimetallic disc 18 until the power supply of the device to be protected is switched off.

Claims (14)

1. A temperature-dependent switch (10) comprising a temperature-dependent switching mechanism (15) and a housing (11, 12) receiving the switching mechanism (15), wherein a first and a second connection surface (22, 23) for the electrical connection of connection leads (46, 47; 55, 56, 66; 71, 82, 83) are provided externally on the housing (11, 12), the temperature-dependent switching mechanism (15) producing or opening an electrically conductive connection between the two connection surfaces (22, 23) depending on the temperature of said switching mechanism, to at least one of the connection surfaces (22, 23) a connection lead (46, 47; 55, 56, 66; 71) being secured in materially bonded manner via its inner end (48, 49; 59, 60, 70; 71), and wherein the inner end (48, 49; 59, 60, 70; 71) of the connection lead (46, 47; 55, 56, 66; 71) is welded on to the at least one connection surface (22, 23) by at least one weld spot (37, 38),
   characterized in that the inner end (48, 49; 59, 60, 70; 71) of the connection lead (46, 47; 55, 56, 66; 71) is welded on to the least one connection surface (22, 23) by one-sided spot welding, and that the inner end (48, 49; 59, 60, 70; 71) of the connection lead (46, 47; 55, 56, 66; 71) comprises at least two lugs (51, 52, 53, 54; 61, 62, 63, 64, 67, 68; 73, 74), each of which is welded on to the at least one connection surface (22, 23) via a weld spot (37, 38).
2. The switch according to claim 1, characterized in that the two lugs (51, 52, 53, 54; 61, 62) extend away from one another and are welded on to the at least one connection surface (22, 23) via an associated pair of weld spots (37, 38).
3. The switch according to claim 1, characterized in that the two lugs (63, 64; 67, 68; 73, 74) extend parallel to one another, are separated from one another via a gap (65; 69; 75) and are welded on to the at least one connection surface (23) via an associated pair of weld spots (37, 38).
4. The switch according to claim 1, characterized in that the inner end (70) of the connection lead (66) comprises four lugs (67, 68) arranged in pairs, each lug being welded on to the at least one connection surface (22, 23) via a weld spot (37, 38).
5. The switch according to claim 4, characterized in that each pair of lugs (67, 68) comprises a gap (69), which separates the lugs (67, 68) from one another, and in that the two pairs of lugs point away from one another.
6. The switch according to claim 1 or claim 2, characterized in that the connection lead is formed as a connection strand (46, 47).
7. The switch according to anyone of claims 1 to 6, characterized in that the connection lead is formed as a terminal lug (55, 56, 66; 71).
8. The switch according to anyone of claims 1 to 7, characterized in that a series resistor (92) is integrated into the connection lead.
9. The switch according to anyone of claims 1 to 8, characterized in that a self-holding resistor (87) is arranged at the inner end (70) of the first connection lead (66) and is electrically connected via one of its terminals (89) to the connection lead (66) and is electrically connected via its other terminal (91) to the second connection lead (55).
10. The switch according to anyone of claims 1 to 8, characterized in that the housing comprises a cover part (12), on which the first connection surface (22) is formed, and a lower part (11), on the base (25) of which the second connection surface (23) is formed, and in that the connection lead comprises a terminal lug (71) bent a number of times, which at its inner end (72) is connected to the first connection surface (22) and at its free end (76) comprises a terminal portion arranged at the height of the second connection surface (23) and extending parallel thereto.
11. The switch according to anyone of claims 1 to 10, characterized in that the temperature-dependent switching mechanism (15) comprises a bimetal part (18).
12. The switch according to claim 11, characterized in that the bimetal part in the closed state of the switch (10) is arranged electrically in series between the connection surfaces (22, 23).
13. The switch according to anyone of claims 1 to 11, characterized in that the temperature-dependent switching mechanism (15) comprises a spring part (17).
14. The switch according to claim 13, characterized in that the spring part (17) in the closed state of the switch (10) is arranged electrically in series between the connection surfaces (22, 23).

Images