EP0887826B1 - Thermally actuated switch with contact bridge - Google Patents

Abstract

The switch (10) has a temperature-responsive switch mechanism (12) contained within housing (11) provided by a base (14) and a cooperating cover which are each made of an insulating material. A pair of stationary contacts (26,27) are applied to the inside of the cover and contacted by a contact bridge (29) in dependence on the temperature. The cover has a pocket (43) into which a pair of contact surfaces (44,45) coupled to the stationary contacts project, for bridging by a resistance (46) inserted in the pocket, to provide a self-holding function.

Description

The present invention relates to a temperature dependent Switch with a temperature-dependent switching mechanism, the one Rear derailleur housing, which is a lower part as well as a Has upper part made of insulating material, two on the upper part provided inside of the stationary contacts, from each of which is electrically connected to an external connection assigned to it is connected, and one moved by the switching mechanism Current transmission element, which is temperature-dependent, the two stationary Connects contacts electrically.

Such a switch is from DE 26 44 411 C2 and EP 0 453 596 A1, according to the preamble claim 1, known.

The known switch has a housing with a cup-like Lower part in which a temperature-dependent rear derailleur is inserted. The lower part is closed by an upper part, by the raised edge of the lower part this is held. The lower part can be made of metal or insulating material be made while the top in any case is made of insulating material.

In the upper part there are two rivets, whose inner heads are serve stationary contacts for the rear derailleur. The rear derailleur carries a current transmission element in the form of a contact bridge, depending on the temperature with the two stationary contacts in System is brought and these then electrically together combines.

The outer heads of the two rivets serve as solder connections for strands.

The temperature-dependent switching mechanism is known per se Have a bimetallic washer and a spring washer that are centrally penetrated by a pin that the contact bridge wearing. The spring washer is circumferentially in the housing led while the bimetallic disc varies depending on the temperature on the bottom of the lower part or on the edge of the spring washer supports and either the contact bridge allows the two stationary contacts or the contact bridge stands out from the stationary contacts, so that the Electrical connection between the external connections interrupted becomes.

This temperature-dependent switch is made in a known manner used to prevent electrical devices from overheating protect. To do this, the switch is electrically connected to the protective device connected in series and mechanically on the Device arranged that it is in thermal communication with this stands. Below the response temperature of the bimetal disc the contact bridge is on the two stationary contacts so that the circuit is closed and that too protective device is supplied. The temperature rises the bimetal disc lifts above a permissible value the contact bridge from the stationary contacts, whereby the switch opens and the supply to the device to be protected is interrupted so that it cools down again can, whereupon the switch closes automatically.

Although the known switch technically fulfills many requirements, he has a number of disadvantages, which with its manufacture, its assembly on a protected one Device and the automatic closing after cooling are.

A disadvantage is the complex manufacture of the known Switch, after making the cover namely the rivets are subsequently attached to this. On another disadvantage is that to the outside Rivet heads still need to be soldered to what is in the strands Rule cannot be automated. However, this means that the Production of a ready-to-use assembly with strands Switch here is time consuming and therefore costly.

Other disadvantages are associated with the assembly of the known Switch on a device to be protected. To the one provides the known switch only solder connections or Stranded wire, whereas crimp or screw connections are often required today are. If the lower part is made of plastic, is the thermal coupling to the device to be protected the known switch relatively bad, while one off Metal-made lower part, the thermal coupling is easy to implement, but the raised metallic one Edge of the lower part often electrically outwards must be isolated.

In summary, in the known switch, on the one hand the elaborate, complicated manufacture and secondly the inadequate installation option for many applications disadvantageous on a device to be protected.

In this context, DE 31 22 899 C2 is a temperature-dependent one Switch with a lower part made of metal and a housing upper part made of insulating material. In the The upper part is cast in two connecting tongues, of which the first connected to a central, stationary contact is. The second connecting tongue is provided with tabs, which are electrically connected to the lower part when the upper part is installed are.

Inside the closed housing thus formed is a Bimetal rear derailleur arranged depending on its Temperature an electrically conductive connection between the stationary contact and the lower housing part and thus between the two connecting tongues.

The disadvantage of this switch is that the assembly, in particular the arrangement of the upper part on the lower part, is complicated because the one with the second connecting tongue trained tabs flipped accordingly Need to become. In case of manufacturing errors or inaccuracies the safety of the electrical connection between the connecting lug and the lower part is not guaranteed.

As with the switch mentioned above also requires here the raised lower part made of metal for certain applications side insulation.

Another disadvantage of the known switch is that the connecting tabs protrude vertically from the upper part, what the assembly on the device to be protected and in particular obstructed the electrical connection.

This switch also has another disadvantage in it too see that it automatically switches on again after cooling. While such switching behavior for protection of a hair dryer can be quite useful two switches described so far for the protection of devices not suitable, which does not change automatically after cooling should turn on again, as it e.g. for electric motors may be the case. In this context it's over many publications already know, the temperature-dependent To provide switches with a so-called self-holding function, which is why there is a resistor parallel to the external connections is switched. After opening the rear derailleur flows in low current through this resistor, which is sufficient Heat developed to the rear derailleur Maintain switching temperature so that the switch automatically does not close again. Rather, the supply voltage must be used for this be switched off so that the rear derailleur no longer through the current flowing through the self-holding resistor is kept above the switching temperature.

Against this background, it is an object of the present invention to create a switch of the type mentioned in the introduction, which is easy to manufacture and simple to protect The device is to be assembled, optionally with a self-holding function can be realized.

With the switch mentioned at the beginning this task solved according to the invention in that in the upper part preferably outwardly open pocket is provided in the Protrude contact areas, each with one of the stationary contacts are connected.

The object underlying the invention is based on this Way completely solved.

The inventor of the present application has recognized that that it is initially also without constructive changes to the known Switch is possible, one preferably to the outside to provide an open pocket into which a resistor is inserted can be that he with his pads in plant with the two contact surfaces. This will Resistor connected in series between the two external connections, with the switchgear closed, i.e. below by its switching temperature, bridged by the switching mechanism becomes. The temperature of the rear derailleur rises above the permissible value, the short circuit is opened, so that now a small current flows through the resistor, which develops sufficient heat to open the rear derailleur to keep.

Because the bag, so to speak, between the stationary contacts the heating resistor is located in the upper part relatively close to the rear derailleur, so that even small Currents are sufficient to develop the required ohmic heat.

If it is not necessary, the switch with a self-holding function to provide, so instead of a resistance also a blind plug to be inserted into the bag the contact areas freely accessible in the bag to the outside isolate. In terms of production technology, the new switch shows great advantages when he was both after his manufacture provided with a self-holding function as well as without it Function can be delivered. In a single production run can therefore use two different switch types are manufactured, which is understandably extremely cost effective is.

Another major advantage is that there are no complex ones Assembly work is required to keep the self to mount the intended resistor on the new switch. The resistance only needs to be in from the outside the bag can be inserted where it then automatically with the Contact areas come into contact. The resistance can be of any Be of a type, a PTC resistor being preferred, has the corresponding pads with which it on the contact surfaces.

With the new switch, it is therefore preferred if in the Bag a resistor is inserted, with both contact surfaces is connected so that it is in series between the external connections is switched and for a self-holding function provides, it is preferred if the resistance in the Bag is pinched or glued and / or preferably through a shrink tube surrounding the switch is insulated on the outside.

These measures are also advantageous in terms of production technology, the resistor only has to be installed in the Pocket can be inserted where it is either mechanical jammed or held by gluing. additionally and / or alternatively the switch can be operated by one Heat shrink tubing surrounded by the resistance after is insulated on the outside, with the heat shrink tubing in addition can also ensure the mechanical hold of the resistor, so that gluing or clamping entirely or partially can be dispensed with.

It is advantageous if the upper part has two connection electrodes are shed, each with one of the stationary Contacts, one of the contact areas and one of the External connections is connected.

The inventor of the present application has recognized that at the new switch connection electrodes poured into the upper part can be the stationary contacts on the Inside of the upper part with external connections outside the Connect the upper part. A particular advantage is included here the manufacture of the new switch, because the connection electrodes can in a first step with stationary contacts as well as the external connections, whereupon then when spraying the upper part, the connection electrodes, so to speak be poured in or overmolded. In other words, while the manufacture of the upper part itself will be the External connections and the stationary contacts attached to this. Furthermore, during the spraying of the upper part the pocket are already formed, areas of Protruding connection electrodes into the pocket around the contact surfaces provide with which a resistor contacts can be. Can be done in a single manufacturing step So the upper part together with the attachment of the connection electrodes as well as that for fastening and contacting the Resistance provided pocket can be realized.

Another advantage is that by choosing the Shape of the connection electrodes now the external connections geometrically can be placed anywhere with the stationary contacts with the external connections themselves now as soldering, Crimp or screw connections can be formed.

This is another advantage of the new switch in it too see that this is much easier to protect Devices can be installed, since the required for the device Connection technology can be provided.

In a further development of the new switch, it is preferred if each connection electrode is a flat metal part, with which the respective external connection, which preferably from the side protrudes the upper part, is integrally formed, wherein further preferably the connection electrodes in parallel next to each other lie in the top.

The advantage here is that the "next to the switch" External connections are well connected, so that the Installation of the new switch on a device to be protected is simplified.

In addition, the new switch is also easy to manufacture, namely the connection electrodes can e.g. strapped or on Tape are fed, while also having good stability cause the upper part, since they are flat metal parts are. Because of this extensive training results in addition, better heat absorption and heat input in the inside of the new switch to the temperature dependent Rear derailleur.

It is further preferred if the respective contact surface is on the respective metal part is formed.

As mentioned above, the advantage here is that automatically release the pocket when spraying the upper part into which e.g. the metal parts on the side protrude so that areas of their surface there as contact surfaces Act.

With the new switch, it is further preferred if everyone welded stationary contact to the associated connection electrode is.

This measure is also advantageous in terms of production technology, because after punching out the connection electrode with associated External connection must only in a next step stationary contact are welded on before then the upper part is encapsulated. Another advantage is that that not part of the connection electrode as a stationary contact is bent downwards, but that the connection electrode itself remains, so to speak, as a flat part that the stationary contact is welded on. With it result but there are clear geometric conditions, errors in Punching or bending the connection electrode cannot do this cause the position of the stationary contacts to each other changes. For the sake of completeness, it should be mentioned that the two stationary contacts at approximately the same level must lie so that the contact bridge is safe on both stationary contacts.

In general, it is preferred with the new switch if that Lower part plate-like and the upper part cup-shaped and the upper part is ring-shaped at its edge, the lower part engages, preferably the lower part made of metal is.

The advantage here is that it is made of metal A good thermal connection of the new switch results in the device to be protected, but still a good adequate lateral electrical insulation by the cup-like upper part made of insulating material is reached. There is also a good seal of the housing outside because of the ring-shaped overlapping edge the upper part can be hot stamped or welded.

It is further preferred if the lower part on his Edge has an external, circumferential groove with which one Bead is engaged on the inside on the edge of the top is trained.

The advantage here is that there is a snap connection, so to speak between top and bottom that results simultaneously represents a kind of labyrinth seal over which the inside of the Housing is protected from dirt, etc. This measure not only ensures a very dust-tight seal of the housing, it also enables one easy manufacture, because after inserting the rear derailleur Upper part and lower part are only locked together need to get all parts of the switch captive together connect to. Then the switch can be closed as desired a welding or stamping station, where the projecting edge is welded or stamped.

Finally, at any point in the manufacturing process optionally a production step can be inserted, where either a resistor or a blind plug in the bag is inserted to either hold it down to effect. The resistance is either pressed in, pinched or glued in, he additionally or alternatively held and / or insulated by a shrink tube can be.

Further advantages result from the description and the attached drawing.

It is understood that the above and those below Features still to be explained not only in the respective specified combinations, but also in other combinations or can be used alone without the frame to leave the present invention.

Fig. 1

einen Längsschnitt durch den neuen Schalter, längs der Linie I-I aus Fig. 3, mit oberhalb davon angedeutetem Widerstand;

Fig. 2

eine Darstellung wie Fig. 1, jedoch mit einem in die Tasche eingelegten Isolierstopfen sowie mit umschließendem Schrumpfschlauch; und

Fig. 3

eine Draufsicht auf den Schalter aus Fig. 1;

An embodiment of the invention is shown in the accompanying drawing and is explained in more detail in the following description. Show it:

Fig. 1

a longitudinal section through the new switch, along the line II of Figure 3, with resistance indicated above it.

Fig. 2

a representation like Figure 1, but with an inserted in the bag insulating plug and with a surrounding shrink tube. and

Fig. 3

a plan view of the switch of Fig. 1;

In Fig. 1, 10 denotes a temperature-dependent switch, which has a housing 11 in which a temperature-dependent Rear derailleur 12 is arranged.

The housing 11 comprises a plate-like lower part 14 the raised edge 15 an external, circumferential Groove 16 is provided. Based on the raised edge 15 a cup-like upper part 17 with an inner shoulder 18 from. Over the shoulder 18 protrudes an edge 19 on which one inside circumferential bead 21 is provided which engages with the groove 16, whereby the lower part 14 with the upper part 17th is locked.

The edge 19 merges into an annular overlap 22, through which the lower part 14 is held on the upper part 17 becomes. This overlap 22 can by stamping or welding a protruding area of the edge 19 is generated become.

While the upper part 17 is made of insulating material, the lower part 14 also made of insulating material or Be made of metal, with a lower part Metal a better thermal connection of the switch 10 results in a device to be protected.

In the upper part 17 are two adjacent connection electrodes 24, 25 cast, each welded wear stationary contact 26, 27. The two stationary Contacts 26, 27 are on an inner side 28 of the upper part 17 arranged.

The two stationary contacts 26, 27 is a current transmission element assigned in the form of a movable contact bridge 29, which via a rivet 30 with the temperature dependent Switch 12 is connected. This includes in a known manner Rear derailleur 12 a bimetallic disc 31, which is with its edge 32 in the switching position shown on a floor 33 of the Base 14 supports. Furthermore, the switching mechanism 12 includes one Spring washer 34, with its edge 35 circumferentially in a circumferential Groove 36 is guided between the shoulder 18th and the edge 15 is formed.

Depending on the temperature, the switching mechanism 12 now brings the contact bridge 29 in contact with the two stationary contacts 26, 27 or differentiate them from them. The exact function of the bimetal rear derailleur is in the aforementioned DE 26 44 411 C2 described so that for more information on this Reference is made.

The top view of the new switch 10 according to FIG. 3 is to recognize that the two trained like knife blades Connection electrodes 24, 25 in one piece with external connections 38, 39 are connected, in the case shown as crimp connections are provided. If the contact bridge 29 in System with the two stationary contacts 24, 25 is so consequently, the two external connections 38, 39 are electrical Conductively connected to each other, the switch 10 is therefore closed. In Fig. 3 it can also be seen that in the upper part 17 an annular space 41 is provided for receiving the switching mechanism 12 is.

The stationary contacts 26, 27 are incidentally on the connection electrodes 24, 25 welded or soldered. From the stationary Contacts 26, 27 are remote in the upper part 17 two outward openings 40 are provided, on the one hand a thermal coupling of the switch 10 to a protective device takes place, these openings on the other hand can be provided for test purposes, namely the inside the switch 10 by heating stamp as quickly as possible and / or the two stationary contacts 26, 27 through Contact test pins from outside to ensure the function of the Switch 10 to test.

During manufacture, the rear derailleur 12 is in the upper part 17th or the lower part 14 inserted, the housing 11 by locking closed between upper part 17 and lower part 14 and finally by stamping or welding the ring-shaped Attack 22 made. The openings serve here 40 for pressing the upper part 17 onto the lower part 14. The reached by the pressure exerted on the electrodes Manufacturing accuracy is better than when directly on Plastic areas of the upper part 17 would be pressed here the dimensional accuracy is worse.

Returning to FIG. 1, there is also shown a web 42 which the two electrodes 24, 25 are insulated from one another in the transverse direction. Above the web 42 is an open to the outside Pocket 43 is provided, in which the two electrodes 24, 25th Extend into the side so that they are in contact with contact surfaces 44, Point 45 into pocket 43. Bridge 42, pocket 43 and Contact surfaces 44, 45 are also in the top view of FIG. 3 clearly visible.

1, a resistor 46 is arranged above the switch 10, which has two pads 47, 48. The resistance 46 is cuboid, so that it is in the pocket 43 can be pressed in, its connecting surfaces 47, 48 come into contact with the contact surfaces 44, 45. The Resistor 46 is preferably a PTC resistor, but it can any type of resistance can be used.

The resistor 46 thus inserted into the pocket 43 can be there jammed or locked, e.g. also possible is to glue the inserted resistor 46 to be Prevent falling out of the pocket 43 and at the same time for good electrical contact between the pads 47, 48 and the contact surfaces 44, 45 to provide.

In this way, resistor 46 is connected in series between the Electrodes 24, 25 and thus between the external connections 38, 39 switched. In the switching state shown in Fig. 1 the resistor 46 bridges through the contact bridge 29, so that it has no electrical function.

If the switching temperature of switch 10 is now exceeded, so the switching mechanism 12 lifts the contact bridge 29 from the stationary contacts 26, 27, so that the resistor 46 now electrically in series between the external connections 38 and 39 lies and is traversed by electricity. This stream is less than the original operating current because of the Resistor 46 drops an additional voltage. The one in the Resistance 46 developed heat passes through the electrodes 25, 26 and the web 42 into the annular space 41, where they ensures that the rear derailleur 12 is not under the Switchover temperature cools down. In other words, by the Resistor 46 flowing residual current causes switch 10 gets into a self-holding state, so it does not automatically closes again. Only when the operating current is switched off is, the switch 10 cools down so that it returns to the 1 state decreases.

If the switch 10 is not to be equipped with a self-holding function instead of resistor 46 e.g. on Blind plug 51 inserted into the pocket 43, as shown in FIG. 2 is shown. This blind plug 51 is made of insulating material and protects the contact surfaces 44, 45. The blind plug as well 51 can by jamming, locking or gluing in the pocket 43 are held, in this regard in FIG Shrink tube 52 is provided, the entire switch 10 surrounds. This shrink tube 52 presses the blind plug 51 into the pocket 43, where it holds it captively. Of course, one can also be inserted into the pocket 43 Resistor 46 held only by a shrink tube 52 become.

In the production of the new switch 10, the connection electrodes 24, 25 encapsulated with insulating material, which the Upper part 17 including the pocket 43 and the annular space 41 is trained. So with a single pass both the connection electrodes 24, 25 integrated into the upper part 17 as well as a recording room for possible resistance 46 created. This recording space is the cuboid Pocket 43, in which a geometrically adapted resistor 46 Can be inserted as needed. The additional manufacturing step around the new switch 10 with a Providing a self-holding function is very easy Resistor 46 only needs to be in the standard one Pocket 43 are inserted.

Claims (12)

1. A temperature-dependent switch having a temperature-dependent switching mechanism (12), a housing (11) receiving the switching mechanism (12), said housing having a lower part (14) and an upper part (17) made of insulating material, two stationary contacts (26, 27) provided on the upper part (17) on its inner side (28), each of said contacts being contacted to an associated external terminal (38, 39), and a current transfer member (29), moved by the switching mechanism (12), which current transfer member electrically connects the two stationary contacts (26, 27) to one another in a temperature-dependent fashion,
   characterized in that there is provided in the upper part (17) a cavity (43), open preferably to the outside, into which cavity project two contact surfaces (44, 45) which are each connected to one of the stationary contacts (26, 27).
2. The switch of claim 1, characterized in that there is placed into the cavity (43) a resistor (46) which is connected to both contact surfaces (44, 45) such that the resistor is connected in series between the external terminals (38, 39) and provides for a self-hold function.
3. The switch of claim 2, characterized in that the resistor is press-fitted or adhesively bonded into the cavity (43).
4. The switch of claim 2 or 3, characterized in that the resistor (46) is externally insulated by means of a heat-shrink sleeve (52) surrounding said switch (10).
5. The switch of anyone of claims 1 - 4, characterized in that two connector electrodes (24, 25) are insert-molded into the upper part (17), each of said connector electrodes being connected to one of the stationary contacts (26, 27), to one of the contact surfaces (44, 45) and to one of the external terminals (38, 39).
6. The switch of claim 5, characterized in that each connector electrode (24, 25) is a flat metal part with which the respective external terminal (38, 39), which preferably projects laterally out of the upper part (17), is integrally configured.
7. The switch of claim 6, characterized in that the respective contact surface (44, 45) is configured on the respective metal part.
8. The switch of claim 6 or 7, characterized in that the connector electrodes (24, 25) lie parallel to one another in the upper part (17).
9. The switch of anyone of claims 1 - 8, characterized in that each stationary contact (26, 27) is welded onto the associated connector electrode (24, 25).
10. The switch of anyone of claims 1 - 9, characterized in that the lower part (14) is configured in a dish-shape and the upper part (17) in a cup-shape, the upper part (17) annularly overlapping the lower part (17) at its rim (19).
11. The switch of claim 10, characterized in that the lower part (17) is produced from metal.
12. The switch of claim 11, characterized in that the lower part (17) comprises at its rim (15) an external peripheral groove (16) with which a ridge (21), configured internally on the rim (19) of the upper part (17), is in engagement.

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