EP2541571A1 - Self-supporting temperature-dependent switch - Google Patents

Abstract

The switch (10') has a housing (11) comprising upper and lower housing portions (13, 14). Terminals of the electrical self-holding resistor are electrically connected with two external clamping terminals (26, 27), respectively. One of the terminals of the resistor is provided in contact with an electrically conducting clamp. The resistor is held at the housing by the clamp. A bottom electrode (15) is arranged in the housing and connected with one of the external terminals. The electrode connected with the clamp through an aperture (38) in the lower housing portion. The electrical resistor is designed as a positive temperature co-efficient (PTC) cylindrical block.

Description

The present invention relates to a self-holding temperature-dependent switch, comprising a housing having a first housing part and a first housing part occlusive second housing part, wherein in the housing, a temperature-dependent switching mechanism is arranged, depending on its temperature, an electrically conductive connection between a the first housing part and an outer terminal disposed on the second housing part, wherein externally to the housing, an electrical resistance part is arranged, which is electrically connected with its first terminal electrically connected to a first of the two outer terminals and with its second terminal electrically connected to a second of the two outer terminals ,

Such a temperature-dependent switch is out of DE 41 42 716 A1 known.

The known temperature-dependent switch comprises a lower housing part made of electrically conductive material, in which a temperature-dependent switching mechanism is inserted, which has a bimetallic snap disk and a spring snap-action disc.

The derailleur carries centrally a movable contact part, which cooperates with a stationary contact part, which is arranged on an electrically insulating housing upper part, through which the lower housing part is closed.

The spring snap disc is supported with its edge inside of the lower housing part and presses the movable contact part against the stationary contact part. In this way, there is an electrically conductive connection between the lower housing part and the stationary contact part on the upper housing part.

If the temperature of the switching mechanism now increases beyond the response temperature of the bimetallic snap disk, it lifts against the force of the spring snap disk, the movable contact part of the stationary contact part and thus opens the temperature-dependent switch.

When the temperature of the switching mechanism cools below its return temperature, the bimetallic snap disk snaps back to its cryogenic temperature and the spring snap-action disc can again bring the movable contact part into contact with the stationary contact part, so that the switch is closed again.

The known switch, like many other such temperature dependent switches, is used to protect an electrical device from overheating. For this purpose, the known temperature-dependent switch is electrically connected in series in the electrical supply circuit of the electrical device to be protected, so that the supply current of the electrical device flows through the temperature-dependent switch.

Furthermore, the temperature-dependent switch is thermally coupled to the device to be electrically protected, so that it - possibly with a certain delay - follows the changes in the temperature of the electrical device to be protected.

If the electric device now heats up beyond the permissible temperature specified by the response temperature of the bimetallic snap disk, this results in the temperature-dependent switch opening in the manner described above, so that the supply current to the electrical device is interrupted, so that this can cool down again.

The cooling of the electrical device also leads to a cooling of the temperature-dependent switch so that it closes again and supplies the device with electrical power.

Such temperature-dependent switches are common, for example, in electric hair dryer, which turn off when overheating and are immediately reusable after cooling.

In many other electrical devices, however, this automatic reconnection is undesirable because it leads to unpredictable damage to the protected electrical equipment. Examples of electrical devices in which an automatic restart is undesirable, are electric motors that are used for example in washing pump lye pumps.

In these electrical devices, it is desirable that they do not automatically turn on again after shutdown due to overheating, but that this reconnection is only possible if previously the electrical supply voltage was switched off.

This is necessary, for example, in the case of the abovementioned lye pumps because the lye pump can jam mechanically due to lint, etc., so that the motor would heat up again after each automatic switch-on, which ultimately leads to a defect in the engine or even to a cable fire could.

If, on the other hand, the electrical device has to be actively switched off, the user is informed that there is a fault and, for example, he can clean the drain pump.

The above-mentioned temperature-dependent switch is equipped for such functions, which is why it is provided with a so-called resistance part, which is arranged electrically parallel to the two outer terminals of the switch. As long as the temperature-dependent switch is closed, the switching mechanism bypasses this also called self-holding resistor resistor part, so that this has no effect on the operating current of the protected electrical equipment.

However, if the temperature-dependent switch opens the circuit, a residual current flows through the self-holding resistor, which is no longer short-circuited.

The resistance of the self-holding resistor is chosen so large that only a very small residual current in the protected electrical appliance flies, on the one hand does not lead to further damage to the electrical device, but on the other hand can heat up the self-holding resistor so far that the temperature-dependent switching mechanism on a Temperature can be maintained, which is above the return temperature.

In other words, just enough ohmic heat is generated in the resistance part when the temperature-dependent switch is open so that the bimetal snap-action disc can not cool down to a temperature below its return temperature.

In this way, the temperature-dependent switch remains open until the circuit is interrupted. Such temperature-dependent switches are also referred to as self-holding switches.

When actively interrupted by the user circuit no residual current flows through the resistor part, so that the temperature-dependent switch can cool down and finally closes again.

In the known temperature-dependent switch, the resistance part is a substrate provided with a resistance paste to which lead terminals are attached.

In the DE 41 42 716 A1 Two embodiments are described how this resistance part can be mechanically held outside the housing of the temperature-dependent switch.

In a first embodiment, a coupling ring is provided, which is plugged from below onto the lower housing part and thus comes into electrical contact with this. The coupling ring has on its underside a plate with retaining tabs, in which the resistance part is held on the retaining plate.

At its one terminal, the resistance part is electrically connected via the retaining tabs and the coupling ring with the housing base, while the other terminal to be connected in a manner not shown via a strand to the stationary contact part.

In a second exemplary embodiment, the resistance part is to be arranged at the top in the region of the stationary contact part and fastened to the housing via a connection bracket.

How exactly the electrical contacting of the resistance member in this embodiment is to take place, this document is not apparent.

The document mentions, however, that the connection of the components, ie the contacting of the substrate by a combination of clamping / riveting and soldering connections in SMD technology should be done.

In this construction, on the one hand, a disadvantage that the structure and the arrangement of the resistance part of the housing is technically complicated and expensive to produce because of the solder joint.

If the resistance part is arranged with the help of the coupling ring down to the bottom of the known switch, it hinders the thermal connection to the electrical device to be protected, because this thermal connection is made only through the intermediate plate.

If, however, the resistance part is arranged on the cover part, then the thermal connection of the resistance part to the temperature-dependent switching mechanism is insufficient, because the heat generated in the resistance part, which is to be used for latching, must pass through the insulating cover into the interior of the temperature-dependent switch.

From the DD 119 497 A1 an open self-holding temperature-dependent switch is known in which an insulating support member, a first terminal lug is arranged, which is connected to a bimetallic spring, and a second terminal lug, which is connected to a fixed contact part, with which the free end of the bimetal.

Spring interacts. On the bimetallic spring is a resistance element which is held by an electrically conductive clip which rests with its one leg on the resistance element and with its other leg on the second terminal lug.

In this way, the resistance element is connected in parallel to the first and the second terminal lug and acts as a self-holding resistor.

Against this background, the present invention seeks to provide a temperature-dependent switch of the type mentioned, which is easy to assemble and structurally simple and avoids the disadvantages of known switch.

In the case of the switch mentioned at the outset, this object is achieved according to the invention in that the resistance part is at its first connection in a preferably planar contact with an electrically conductive clamp, via which the resistance part is held on the housing and at the same time electrically connected to the first external connection.

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

Namely, the inventors of the present application have recognized that the resistance part can be connected by pure clamping technology with the temperature-dependent switch, wherein the electrically conductive clip also serves for the thermal connection of the thus formed, self-holding switch to the electrical device to be protected.

It is preferred that the first terminal surface comes into contact with the clip, which is in a manner to be described for the electrical contacting advantage.

In this case, it is preferable if the resistance part rests with its second connection preferably flat on an electrode connected to the second external connection.

Several advantages are associated with this measure. On the one hand, the contacting takes place on the second connection by mechanical contact, soldering, welding or similar connection measures can therefore be dispensed with according to the invention.

On the other hand, the electrical contacting between the resistance part and the switch preferably also takes place at the second connection via a flat contact, so that the heat developed in the resistance part is well introduced into the interior of the temperature-dependent switch, so that even a small heat development of the resistance part is sufficient to keep the temperature-dependent derailleur at a temperature that is above the return temperature.

However, this measure does not lead to the fact that the thermal connection of the switch is reduced to the electrical device to be protected, because at its other terminal, the resistance part is electrically connected to the electrically conductive bracket, via which the thermal connection to the device to be protected he follows.

While in the switch according to the above-mentioned DE 41 42 716 between the resistance part and the housing, the retaining plate of the coupling ring or other holding part is provided according to the invention, the resistance part with its one connection now directly and preferably flat on a connected to the corresponding outer terminal of the housing electrode, so that here both the electrical and the thermal connection is optimal.

The inventors of the present application have further recognized that it is sufficient for the electrical connection of a self-holding resistor, if the contacts are made purely by mechanical clamping, which is advantageous if the system is flat.

In the context of the present invention, "flat contact" is understood to mean the installation of two flat parts, that is to say straight no point or line contact with arched, elongated or pointed components. With a suitable design, the advantages of the invention can also be realized by rather point or line-shaped contacts. It is important above all that the electrical contact is ensured in particular by mechanical pressure and not by material-locking connections.

In particular, when the resistance part has a PTC characteristic, ie with increasing heating has an increasing resistance, so to speak counteracts the increasing heating by reducing the current flow, it is namely not necessary that the contact resistance between the resistance part and the external terminals so low are, as is possible by soldering or welding connections.

The resistance value of a self-holding resistor is typically in the range of several kilo-ohms, and because of the positive temperature characteristic, the thermal output is approximately identical for a voltage drop in the range of 90 to 250 volts across the resistor portion.

In other words, this means that a contact resistance of several 100 ohms can be tolerated if the resistance part itself has a resistance value in the range of a few kilo-ohms and the supply voltage of the electrical device to be protected corresponds to the mains voltage.

The inventors of the present application have thus recognized that the quality of the contact resistances in the just-described terminal contact is sufficient to provide sufficient heating of the temperature-dependent switching mechanism via the resistance part, so that the latter remains at a temperature above the return temperature until the Circuit is actually interrupted.

It is preferred if the housing has a closed by an electrically conductive cover electrode housing lower part of electrically insulating material, and the resistance part rests with its second terminal on the cover electrode, wherein further preferably in the lower housing part, a bottom electrode is arranged, through an opening in the lower housing part is electrically connected to the bracket.

The advantage here is that a mechanically simple constructed temperature-dependent switch can be provided in a technically simple manner subsequently with a self-holding function.

The thermal connection to the electrical device to be protected via the clip, the thermal coupling to the resistor part by direct contact with the cover electrode.

In general, it is preferred if the clamp is U-shaped with a bottom and two approximately perpendicular side walls, wherein the housing is held by the side walls and the resistance part between the bottom and the housing is clamped, preferably at least one of the side walls, a holding portion is provided which extends approximately parallel to the bottom of the bracket and bears against the bottom of the housing, wherein more preferably on the holding portion, a hook is provided, which projects into the bottom of the housing.

This measure is constructively advantageous. The one-piece U-shaped bracket engages around the assembly of housing and resistance part such that the finished self-holding switch is easy to assemble and held together purely by the spring force of the clip. At the same time, the electrical parallel connection of the resistance part to the external connections takes place.

In the clip are successively inserted from the side first, the housing and then the resistance part, further manipulations are not required.

Further, it is preferred if beads are provided for fixing the resistance part in the bottom of the clip, wherein more preferably a tab for fixing the housing is provided on the holding portions, wherein preferably the clip is made of resilient material.

These measures are in terms of a quick and easy installation of the new switch advantageous because even when inserting or inserting the housing and resistance part in the bracket these are fixed and clamped, which gelichzeitig also the electrical contact takes place.

In general, it is preferred if the resistance part has an electrical resistance with PTC characteristic.

Here it is advantageous that the height of the contact resistances for the reasons mentioned above play a minor role for the self-holding function, so that a pure Klemmkontaktierung is possible.

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 particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Fig. 1

eine schematische Schnittdarstellung eines temperaturabhängigen Schalters in Seitenansicht, ohne Widerstandsteil;

Fig. 2

eine schematische Draufsicht auf einen perspektivisch dargestellten Schalter gemäß Fig. 1;

Fig.3

eine schematische Draufsicht auf eine perspektivisch dargestellte Klammer, mit der ein Widerstandsteil an dem Schalter aus Fig. 2 befestigt wird;

Fig. 4

die um 180° gedrehte Anordnung des Schalters aus Fig. 2 in der Klammer aus Fig. 3, in perspektivischer Ansicht von schräg oben;

Fig. 5

die Montage eines Widerstandsteiles an der Anordnung aus Fig. 4; und

Fig. 6

den fertig montierten Schalter in einer Ansicht wie in Fig. 5.

The invention is illustrated in the drawing and will be explained in more detail in the following description. Show it:

Fig. 1

a schematic sectional view of a temperature-dependent switch in side view, without resistance part;

Fig. 2

a schematic plan view of a switch shown in perspective according to Fig. 1 ;

Figure 3

a schematic plan view of a bracket shown in perspective, with a resistance part of the switch Fig. 2 is attached;

Fig. 4

the rotated by 180 ° arrangement of the switch Fig. 2 in the clip Fig. 3 in a perspective view obliquely from above;

Fig. 5

the assembly of a resistor part of the arrangement Fig. 4 ; and

Fig. 6

the fully assembled switch in a view as in Fig. 5 ,

In Fig. 1 is shown in a schematic side view and cut a temperature-dependent switch 10 ', which is not yet equipped with a self-holding function. The switch 10 'has a housing 11 in which a temperature-dependent switching mechanism 12 is arranged.

The housing 11 comprises a housing lower part 14, which is closed by an upper housing part 13 and made of electrically insulating material, at the bottom of which a flat bottom electrode 15 which is partially overmolded by the material of the housing lower part 14 is arranged, which has a center in the middle which serves as a stationary contact part 16.

The upper housing part 13 is formed by an electrically conductive cover electrode 17.

The temperature-dependent rear derailleur 12 comprises, in a manner known per se, a spring snap-action disc 18, which carries a movable contact part 19, which in the in Fig. 1 shown switching position in contact with the stationary contact part 16.

Between the spring snap-action disc 18 and the movable contact part 19, a bimetal snap-action disc 21 is arranged freely.

The spring snap-action disc 18 is supported by its edge 22 on the cover electrode 17, so that it produces an electrically conductive connection between the cover electrode 17 and the bottom electrode 15 in the housing lower part 14.

Increases now the temperature of the bimetallic snap disk 21, so it comes with its edge 23 in abutment with a circumferential shoulder 24 of the housing part 14, which covers the bottom electrode 15 at the edge 25 and there isolated from the bimetallic snap disk 21. The bimetallic snap disk 21 then jumps from its in Fig. 1 shown convex in a concave shape in which it lifts against the force of the spring snap disk 18, the movable contact part 19 of the stationary contact part 16, so that the switch 10 is opened.

The outer contact of the switch 10 'from Fig. 1 takes place on the side of the housing 11 protruding external terminals 26, 27, which are integrally formed with the bottom electrode 15 and the cover electrode 17.

The cover electrode 17 is fixed to the lower housing part 14 via a circumferential, hot-pressed edge 28 of the lower housing part 14. In this case, the cover electrode 17 rests on a circumferential shoulder 29 inside in the lower housing part 14.

In Fig. 2 the switch 10 'is off Fig. 1 shown in a schematic perspective view obliquely from above.

The two outer terminals 26, 27 are designed as terminal connections which protrude laterally from the switch 10 '.

In Fig. 2 It can be seen that the lower housing part 14 with its peripheral edge 28 surrounds the upper housing part 13, that is to say the cover electrode 17, and forms a type of upwardly open, almost circular receiving space 30.

The described so far switch 10 'is disclosed for example in the DE 196 09 310 A1 , the disclosure of which is hereby incorporated by reference into the subject of the present application.

In Fig. 3 is shown a one-piece, U-shaped bracket 31 made of resilient and electrically conductive material having a bottom 32 and two side walls 33 and 34 which are perpendicular to the bottom 32. The side wall 33 is provided with an angled holding portion 35 which is parallel to the bottom 32.

Opposite the side wall 34 is also provided with a holding portion 35, which merges into a tab 36, which is also parallel to the Floor 32 runs. At its free end, the tab 36 is provided with a small hook 37, which is bent back to the bottom 32 and approximately parallel to the side wall 34 extends.

The bracket 31 has a length LK and a width BK, which correspond somewhat to the length LS and the width BS of the switch 10, which in Fig. 2 are indicated.

In Fig. 4 is shown that the switch 10 'off Fig. 2 in the clip Fig. 3 is inserted, this arrangement compared to the Fig. 1 to 3 turned around and again shown in perspective from above.

In Fig. 4 It can be seen that the tab 36 engages with a projection 37 in an opening 38 in the bottom 39 of the housing lower part 14. This opening 38 is also in Fig. 1 to recognize, it leads directly to the bottom electrode 15, which is thus partially free in the opening 38. In this way, the tab 36 abuts against the bottom electrode 15 and is electrically connected to the bottom electrode 15 and thus to the external terminal 26.

In Fig. 3 and 4 It can also be seen that on the holding part 35, a further tab 40 is arranged, which is bent back onto the bottom 32 and extends transversely to the side wall 33, so that is held by the switch 10 'laterally immovable in the bracket 31.

In the Fig. 5 and 6 is the further assembly of the arrangement Fig. 4 shown, now between the bottom 32 of the bracket 31 and the in Fig. 5 downwardly facing cover electrode 17 of the switch 10, a resistance part 41 in the form of a cylindrical PTC module 42 is inserted. The resistance part 41 has a lower port 43 and an upper port 44 each formed by the round end face of the cylinder.

The fully assembled, self-holding temperature-dependent switch 10 is in Fig. 6 to see.

After complete insertion, the PTC module 42 is electrically connected to the bottom 32 of the clamp 31 by its flat connection 43, while it is seated with its upper connection 44 in the receiving space 30 and electrically connected to the cover electrode by planar mechanical contact 17 is connected.

The PTC module is defined by the edge 28 and two only in Fig. 3 to be recognized beads 45 mechanically fixed in the bottom 32 of the bracket 31.

At the bottom 39 of the housing 11 thus are the two holding portions 35, which compress the resistance part 41 and the housing 11 between itself and the bottom 32 of the resilient clamp 31.

The assembly of the new switch is extremely simple. In addition to the existing switch 10, the clip 31 is still required, in the first case, the housing 11 is inserted. In this case, the housing 11 is already prefixed by the hooks 37 and the tab 40 in the bracket 31.

Next, only the PTC module 42 between bottom 32 and cover electrode 17 must be pushed, being fixed by the receiving space 30 and the beads 45. By the spring force of the bracket 31, the entire assembly is mechanically held together, adjustments or further manipulations are not required.

The clip 31 serves not only the mechanical support of the resistance part 41 on the switch 10, it also leads simultaneously to an electrical parallel connection of the resistance part 41 to the temperature-dependent switch 10th

Via the tab 36, the resistance part 41 is now electrically connected with its lower terminal 43 to the bottom electrode 15 and consequently to the outer terminal 26. With its upper terminal 44, the resistance part 41 abuts directly on the cover electrode 15, that is, it is electrically connected to the second outer terminal 27.

In this way, therefore, the resistance part 41 is electrically parallel to the two outer terminals 26 and 27, wherein the electrical contact is made by the clamping force of the clip 31, further connection measures are not required.

Of course, it is possible, instead of the switch 10 according to Fig. 1 to use a switch in which the upper housing part 13 and the lower housing part 14 are made of electrically conductive material, as it is realized for example in the switch, which in the DE 21 21 802 A1 is described.

This switch also has a temperature-dependent switching mechanism, which produces an electrically conductive connection between the electrically conductive upper part and the electrically conductive lower part. Upper housing part and lower housing part are electrically separated from each other by an insulating film.

With the bracket 31 off Fig. 3 can now also the resistance part 41 mounted on such a switch, wherein for contacting and mechanical support in the bottom of this switch, an opening may be provided, into which the hook 37 of the tab 36 engages.

On the hook 37 and the associated opening in the bottom of the switch can also be dispensed with, if the stop and the contact can be made solely by the tab 36.

Claims (11)

Self-holding temperature-dependent switch, comprising a housing (11) having a first housing part (14) and a second housing part (13) closing the first housing part (14), wherein a temperature-dependent switching mechanism (12) is arranged in the housing (11), which, depending on its temperature, produces an electrically conductive connection between an outer terminal (26, 27) arranged on the first housing part (14) and an outer housing part (13), an electrical resistance part (41 ) is electrically arranged with its first terminal (43) electrically connected to a first (26) of the two outer terminals (26, 27) and with its second terminal (44) electrically connected to a second (27) of the two outer terminals (26, 27). connected is,
characterized in that the resistance part (41) is at its first connection (43) in preferably planar contact with an electrically conductive clip (31) via which the resistance part (41) held on the housing (11) and at the same time electrically to the first External connection (26) is connected. Switch according to claim 1, characterized in that the resistance part (41) rests with its second connection (44) areally on an electrode (17) connected to the second external connection (27). Switch according to Claim 2, characterized in that the housing (11) has a housing lower part (14) made of electrically insulating material which is closed by an electrically conductive cover electrode (17), and the resistance part (41) has its second connection (44) on the cover electrode (17). Switch according to one of claims 1-3, characterized in that in the lower housing part (14) with the first outer terminal (26) connected to the bottom electrode (15) is arranged through an opening (38) in the lower housing part (14) electrically the clip (31) is connected. Switch according to one of claims 1 - 4, characterized in that the clip (31) is U-shaped with a bottom (32) and two approximately perpendicular side walls (32, 33) is formed, wherein the housing (11) through the Side walls (33, 34) held and the resistance part (41) between the bottom (32) and the housing (11) is clamped. A switch according to claim 5, characterized in that on at least one of the side walls (33, 34) a holding portion (35) is provided, which extends approximately parallel to the bottom (32) of the bracket (31) and on the bottom (39) of the Housing (11) is applied. Switch according to claim 5, characterized in that on the holding portion (35) has a hook (37) is provided which projects into the bottom (39) of the housing (11). Switch according to one of claims 5 - 7, characterized in that in the bottom (32) of the clip (31) beads (45) for fixing the resistance part (41) are provided. Switch according to one of claims 6 - 8, characterized in that on the holding portions (35) has a tab (40) for fixing the housing (11) is provided. Switch according to one of claims 1 - 9, characterized in that the 4Viderstandsteil (41) has an electrical resistance (42) with PTC characteristic. Switch according to one of claims 1 - 10, characterized in that the clip (31) is made of resilient material.

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