EP2503576A1 - Method for producing a temperature-dependent switch - Google Patents

Abstract

The method involves arranging a power transmission unit at a temperature-dependent control unit, and providing a lower part for a housing. An upper part (15) is provided for the housing and made of positive temperature coefficient resistor material. Two contact rivets (33, 34) are mounted at through holes (46, 47) of the upper part. The control unit is inserted into the lower part, and the lower part is closed with the upper part. The contact rivets are inserted successively into the holes independent of each other and fastened to the upper part.

Description

The present invention relates to a method for producing a temperature-dependent switch with a temperature-dependent switching mechanism, a housing receiving the switching mechanism having a lower part and a top of PTC thermistor, two extending through the upper part contact rivets whose inner heads act as stationary contacts and the outer Heads serve the external connection, as well as arranged on the derailleur and moved by this current transmission member which is temperature-dependent with the two stationary contacts in the system, comprising the steps of: providing the temperature-dependent switching mechanism on which the current transmitting member is already arranged; Providing the lower part for the housing; Providing the upper part made of PTC resistor material for the housing, which has two passage openings for receiving the two contact rivets; Mounting the two contact rivets on the through holes; Inserting the rear derailleur in the lower part; and closing the lower part with the upper part.

Such a switch is from the DE 198 27 113 C2 known.

A comparable, from the DE 26 44 411 C2 Known switch has a housing with a cup-shaped lower part, in which a temperature-dependent switching mechanism is inserted. The lower part is closed by an upper part, which is held by the raised edge of the lower part of this. The lower part can be made of metal or insulating material, while the upper part here in any case consists of insulating material.

In the upper part sitting two contact rivets whose inner heads serve as stationary contacts for the rear derailleur. The rivet shanks protrude through through openings in the upper part to the outside and go there in outer heads that serve the external connection of the known switch. Lead wires can be soldered directly to these outer heads, it also being known to maintain contact angles with the outer heads, to be soldered or crimped to the connecting leads.

The rear derailleur carries a current transfer member in the form of a contact bridge, on top of which a silver support is provided which has two interconnected mating contacts, which are brought into contact with the two stationary contacts depending on the temperature and then electrically connect them together.

The temperature-dependent switching mechanism has a bimetal snap-action disc and a spring snap-action disc, which are centrally penetrated by a pin which carries the contact bridge. The spring snap-action disk is circumferentially guided in the housing, while the bimetallic snap disk is supported depending on the temperature at a shoulder of the lower part or at the edge of the spring snap disk and thereby allows either the system of contact bridge to the two stationary contacts or the Contact bridge of the stationary contacts lifts so that the electrical connection between the external connections is interrupted.

This temperature-dependent switch is used in a known manner to protect electrical equipment from overheating. For this purpose, the switch is electrically connected in series with the device to be protected and mechanically arranged on the device so that it is in thermal communication with this.

Below the response temperature of the bimetallic snap disk, the contact bridge is applied to the two stationary contacts, so that the circuit is closed and the device to be protected is supplied with power via the switch. If the temperature rises above a permissible value, the bimetallic snap-action disc lifts the contact bridge away from the stationary contacts, thus opening the switch and interrupting the supply of the device to be protected.

The now de-energized device can then cool down again. In this case, the thermally coupled to the device switch cools down again, which then automatically closes again.

By dimensioning the contact bridge of the known switch is able, compared to other temperature-dependent switches in which the operating current of the device to be protected flows directly through the bimetallic snap disk or its associated spring snap-action, so much higher operating currents to lead that it can be used to protect larger electrical appliances with high power consumption.

As already mentioned, the known switch automatically switches on again after cooling the device protected by it. While such a switching behavior for protecting a hair dryer, for example, can be quite useful, this is not desirable anywhere where the device to be protected Do not switch on automatically after switching off to avoid damage. This applies, for example, for electric motors that are used as drive units.

The initially mentioned DE 198 27 113 proposes therefore to provide a so-called self-holding resistor, which is electrically parallel to the external terminals. The self-holding resistor is in the open switch electrically in series with the device to be protected, through which only a harmless residual current now flows because of the resistance value of the self-holding resistor. However, this residual current is sufficient to heat the self-holding resistor so far that it emits a heat that holds the bimetallic snap disk above its switching temperature.

The from the DE 198 27 113 Known switch may also be equipped with a current-dependent switching function, to which a further resistor is provided, which is permanently connected in series with the external terminals. The operating current of the device to be protected thus constantly flows through this heating resistor, which can be dimensioned so that it ensures that the bimetallic snap disk is heated to a temperature above its response temperature when a certain operating current is exceeded, so that the switch at an increased Operating current already opens before the device to be protected has warmed up inadmissible.

The DE 198 27 113 C2 describes two different ways in which the self-holding resistor can be realized and installed. In a first embodiment, resistance paths are provided on the inside of the upper part, which connect the two stationary contacts with each other and, when the switch is open, carry the residual current which provides for latching.

In another embodiment, the upper part is made of PTC material, so that the upper part itself forms the self-holding resistor.

Manufacturing attempts in the company of the applicant have now shown that the from the DE 198 27 113 C2 Known switch can not produce with the required low reject rate and with sufficient certainty, if the upper part consists of PTC thermistor.

The known switch is therefore made for cost reasons in the variant with an upper part of an insulating material, on the inside of which resistance paths are provided which serve as self-holding resistance.

Although this switch has proven itself, it would be desirable if the switch could be made with a top of PTC thermistor, because on the one hand, the heat dissipation in this design variant is more efficient, so that a lower residual current is sufficient to keep the switch reliably opened.

Furthermore, a self-holding resistor made of PTC thermistor is a safety element, because with increasing temperature, the resistance of the self-holding resistor increases and thus limits the residual current.

On the other hand, upper parts, ie, covers made of PTC thermistor material, are already used in temperature-dependent switches. That's how it describes DE 195 17 310 C2 Such a switch, in which a stationary contact is arranged centrally on such a cover, with which cooperates a movable contact, which is supported by a derailleur and moved. The operating current of the device to be protected flows from the stationary to the movable contact and then through the spring washer of the switching mechanism in the made of conductive material lower part of the housing.

If the derailleur lifts the movable contact from the stationary contact because of too high a temperature, the cover made of PTC resistor material is connected in series between the stationary contact and the lower part and guides one Residual current, which leads to a sufficient warming of the lid to keep the derailleur at a temperature above the switching or response temperature.

The from the DE 195 17 310 C2 Known switch can also be produced inexpensively and with little waste.

Based on this prior art, it is therefore an object of the present invention to specify a cost-effective production method with a low reject rate for the switch mentioned above.

According to the invention, this object is achieved in the aforementioned method in that the two contact rivets are inserted successively and independently of each other in the through holes and then attached to the upper part.

The contact rivets are thus first placed individually - be it manually or automatically - and then fastened. The rivet shanks are inserted separately from each other and successively through the passage openings. Thereafter, the two closing heads can be formed again in a common manufacturing step. The setting heads of the contact rivets can form both the stationary contacts and the outer heads.

In general, however, the stationary contacts are formed by the setting heads, which are connected to rivet shanks which protrude through the through holes in the upper part to the outside and there pass into the closing heads, which are formed only after the insertion of the rivet shank through the through hole.

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

In the context of the present invention, a "PTC resistor material" is understood to mean an electrically conductive ceramic material which has a positive temperature coefficient, so that its electrical resistance increases as the temperature increases. The course of the electrical resistance value over the temperature is non-linear.

Such PTC thermistors are referred to in the context of the present invention as PTC resistors. They are made, for example, from semiconductive, polycrystalline ceramics such as BaTiO ₃ .

To produce the PTC caps, blends of barium and titanium compounds and other materials which together give the desired electrical and thermal properties are pressed into a mold having the desired geometric dimensions and through-holes and then sintered at high temperatures.

The inventor of the present application has recognized in this connection that the geometry of the cover changes as a result of the sintering, the geometric position of the passage openings varies. Both their distance from each other and their distance from the center of the lid changes in an unpredictable manner during sintering.

Although the material shrinkage is taken into account in this production, but with two through holes, the shrinkage of the diameter but not the change in the distance can be predicted with sufficient accuracy.

In other words, the location of the through holes varies, both between PTC caps from different batches and between PTC caps from a single batch. For PTC covers with a centric Through hole, as shown in the above DE 195 17 310 C2 are known, this problem does not exist.

The variation in the distance of the through holes has now led to the previous production attempts that the reasons of efficiency always together, so with a fixed distance automatically supplied to each other contact rivets were not always positioned exactly above the passage openings.

This has then either already during assembly of the contact rivets or at a later manufacturing step, for example, when closing the lower part with the upper part, led to the fact that the upper part is cracked or even completely broken.

On the other hand, if the contact rivets are supplied separately from one another according to the invention, the exact position of the individual passage openings can be determined beforehand in the case of automatic assembly. However, this means that the corresponding production machines must be provided with either an image recognition system or with a probe to determine the exact location of the two through holes for each individual shell before it is fitted with the contact rivets.

It should be noted that the tops are often kept in bulk as bulk, so that in the reservoir tops from different batches are available, and the position of the passage openings scatters wide accordingly.

It is therefore preferred if the tops are fitted manually with the two contact rivets.

The inventor has therefore not gone the way offering itself at first glance, to reduce the diameter of the rivet shank or to increase the clear width of the through holes.

Namely, the change of the diameters would have the disadvantage that the positions of the inner and outer heads would no longer be known reproducibly, so that there could be problems with the contact on the current transmitting member. Furthermore, the connection to the outer heads would no longer be fully automatic feasible.

Lower diameter of the rivet shanks could also cause problems with the high currents of over 10 A up to 25 A and more, for which the switch is intended. The rivet shafts must be able to conduct these currents without being burned or getting too hot.

Therefore, the inventor of the present application has chosen the unusual at first glance way to make the placement of the tops either highly automated or alternatively by hand. Although hand assembly appears to be disadvantageous from an automation standpoint, this manual step allows for all other steps to be performed fully automatically, yet still provides low rejection production with tight tolerances between port and rivet shank.

The derailleur can include a bimetallic snap disk, which ensures the closing pressure and the temperature-dependent opening movement. The closing pressure can also be applied alone or in addition by a Federschnappscheibe, while a bimetallic snap disk is provided, which either provides only for the opening movement or contributes to the contact pressure in its low temperature position.

Therefore, it is preferred if the derailleur comprises a bimetal snap-action disc which is mechanically connected to the current transfer member and this presses below its switching temperature against the stationary contacts and lifts above their switching temperature of these.

On the other hand, it is preferred if a spring snap-action disc, which biases the current transfer member in the sense of an abutment against the stationary contacts, and also a bimetallic snap disk is provided, which lifts the current transfer member above its switching temperature of the stationary contacts, and further preferably the spring -Schnappscheibe between the current transmitting member and bimetallic snap disk is arranged.

While it is quite sufficient, if only a bimetallic snap disk is provided which produces both the contact pressure and provides for the temperature-dependent opening, can by a spring-snap disk, which in addition to the bimetallic snap disk or alone causes the contact pressure, the bimetallic Snap disk are relieved of mechanical stress in their low temperature position, which contributes to greater long-term stability of their switching behavior.

Further, it is preferred if the current transmission member is an approximately round contact plate, which is provided on its surface facing the stationary contacts with two electrically interconnected contact surfaces.

The contact surfaces in each case have such a large contact surface, that even with production-related fluctuation of the position of the stationary contacts with these safely come into contact and thus reliably close the switch.

The contact plate is preferably connected by a pin-like rivet centric with the bimetallic snap disk and possibly the spring snap-action disc.

Here it is advantageous that the entire rear derailleur is to be handled during production as a separate unit and thus prefabricated can be stored.

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

einen schematischen, nicht maßstabsgetreuen Längsschnitt durch den neuen Schalter;

Fig. 2

in einer schematischen Seitenansicht die Bestückung des Oberteils für den Schalter aus Fig. 1 mit stationären Kontakten; und

Fig. 3

den Schalter aus Fig. 1 in einer schematischen Explosionsdarstellung in Seitenansicht, um den Zusammenbau der einzelnen Komponenten zu verdeutlichen.

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

Fig. 1

a schematic, not to scale longitudinal section through the new switch;

Fig. 2

in a schematic side view of the assembly of the upper part of the switch Fig. 1 with inpatient contacts; and

Fig. 3

the switch off Fig. 1 in a schematic exploded view in side view to illustrate the assembly of the individual components.

In Fig. 1 is denoted by a temperature-dependent switch 10, which includes a temperature-dependent switching mechanism 11 which is housed in a housing 12.

The housing 12 comprises a lower part 14 and a closing this upper part 15 which is held by a flanged edge 16 of the lower part 14 at this. Between the lower part 14 and the upper part 15, a ring 17 is arranged, which is supported on a shoulder 18 of the lower part 14 and there leads a spring snap-action disc 21 of the rear derailleur 11 at its edge.

The rear derailleur 11 additionally comprises, in addition to the spring snap-action disc 21, a bimetal snap-action disc 22 which, together with the spring snap disc 21, is centrally penetrated by a pin-like rivet 23 by which these are mechanically connected to a current transfer member in the form of a contact plate 24. The rivet 23 has a first shoulder 25 on which the bimetal snap disc 22 is seated with radial and axial play, with a second shoulder 26 is provided on which the spring snap disc 21 also sits with radial and axial play.

The bimetallic snap disk 22 is supported with its peripheral edge inside in the lower part 14.

The already mentioned contact plate 24 has in the direction of the upper part 15 two electrically interconnected, large-area contact surfaces 27 which cooperate with two arranged on the inside 29 of the upper part 29 stationary contacts 31, 32, the inner heads of contact rivets 33, 34 are the pass through the upper part 15 and with their outer heads 35, 36 serve the external connection.

In the in Fig. 1 shown switching position press spring snap-action disc 21 and bimetal snap disc 22 the contact plate 24 against the stationary contacts 31 and 32, which are thus connected to each other via the contact surfaces 27; the switch 10 is thus closed.

If the temperature of the bimetal snap-action disc 22 increases beyond its response temperature, it snaps from the convex into a concave shape and supports itself with its edge in the region of the ring 17 and pulls the contact plate 24 against the force of the spring. Snap-action disc 21 away from the stationary contacts 31, 32; the switch 10 is now open.

The switch described so far is from the DE 26 44 411 C2 and the DE 198 27 113 C2 known. If the temperature lowers now, would the from the DE 26 44 411 C2 well-known switch again in the in Fig. 1 snapped back, closed state shown.

Like the one from the DE 198 27 113 C2 Known switch is the upper part 15 made of a PTC thermistor, so represents a PTC resistor, which is electrically connected between the stationary contacts 31, 32. The upper part 15 thus acts as a self-holding resistor, as has already been described in detail above.

In Fig. 2 schematically shows how the upper part 15 is fitted with the contact rivets 33, 34, each having a setting head 37, 38 in the unformed state, from which a rivet shank 41, 42 extends, having a free end 43, 44 which with Help a schematically indicated at 45 molding tool is converted to closing heads.

First, it can be seen that two through-openings 46, 47 are provided in the upper part 15, the inner diameter 48, 49 of which corresponds approximately to the outer diameter 51, 52 of the rivet shanks 41, 42.

In the through-openings 47, 48, first the contact rivets 33, 34 are placed so that their setting heads 37, 38 come to rest on the inner side 29 of the upper part 15 and form the stationary contacts 31, 32 there. The rivet shanks 41, 42 protrude through the passage openings 46, 47 through the top 53 of the upper part 15, where they protrude with their free ends 43, 44.

In Fig. 2 on the left is a contact rivet 33 shown before insertion into the through hole 46, while in Fig. 2 on the right, the other contact rivet 34 has already been inserted into the passage opening 47.

As soon as both contact rivets 33, 34 are seated in the passage openings 46, 47, their upper free ends 43, 44 are deformed with the forming tool 45 indicated above the upper part 15 to the outer heads 35, 36, which are in Fig. 1 are shown.

The inner diameter 48, 49 of the through holes 46, 47 and the outer diameter 51, 52 of the contact rivets 33, 34 are matched to each other with very tight tolerances, so that the position of the inner heads 37, 38 and the outer heads 35, 36 on the upper part 15th as accurately as possible. The diameters 48, 49, 51, 52 in Fig. 2 are therefore almost the same size.

The upper part 15 is made of a PTC thermistor material and is solidified after pressing by sintering. In this sintering, the distance between the passage openings 46, 47 indicated at 54 changes slightly so that the two contact rivets 33, 34 can not be inserted into the passage openings 46, 47 simultaneously and fully automatically.

Since the exact distance 54 between the through holes 46, 47 may already vary between tops 15 from the same production batch, the distance 54 of the two contact rivets 33, 34 must be variable when fitting the upper part 15.

This is achieved in that the contact rivets 33, 34 are inserted one after the other into the passage openings 46, 47, although simultaneous insertion is actually preferred in the case of fully automatic production.

This insertion of the contact rivets 46, 47 can be done by hand, which is a disadvantage in the desired fully automatic production, but on the other hand ensures that the equipped with the contact rivets 33, 34 tops 15 in the molding of the outer heads 35, 36 and the subsequent obstruction in the temperature-dependent switches 10 do not burst, jump or break.

On the other hand, it is also possible in a highly automated machine first for each upper part 15, the position of the through holes 46, 47 to determine automatically in an accurate manner and then introduce the two contact rivets 33, 34 sequentially automated.

While in the switch 10 of Fig. 2 the setting heads 37, 38 of the contact rivets 33, 34 form the stationary contacts 31, 32, it is quite possible, hineinzustecken the contact rivets 33, 34 from above into the upper part 15, so that the setting heads 37, 38, the outer heads 35, 36th form while the closing heads then the stationary contacts 31, 32 represent.

After the upper part 15 has been fitted in the manner described with the two contact rivets 33, 34 and the contact rivets 33, 34 were then mounted by forming the closing heads, the new switch 10 can be assembled.

In Fig. 3 the switch 10 is off Fig. 1 shown in an exploded view, the above according to Fig. 2 manufactured upper part 15 can be seen.

Under the upper part 15 are the spacer ring 17 and including the rear derailleur 11 with the contact plate 24 and the bimetallic snap disk 22 and the spring snap disk 21st

At the bottom of Fig. 3 the lower part 14 is shown with the raised edge 16, which of course is not crimped here.

In the order shown now both the rear derailleur 11 and the ring 17 and then the upper part 15 are inserted into the lower part 14, whereupon then the raised edge 16 is crimped, so that the switch 10 made Fig. 1 results.

All these steps are fully automatic to perform, with the assembly of the rear derailleur 11 from the various items is fully automatic possible.

Only in the assembly of the upper part 15 with the contact rivets 33, 34, a manual step is provided, on the one hand does not really hindered the automatic production, but on the other hand, in an elegant way ensures that the Committee in the production of the tops 15 or the new Switch 10 is very small, even if the tolerances between the diameters 48, 49, 51, 52 of the through holes 46, 47 and the rivet shanks 41, 42 are very narrow.

These tight tolerances are desired so that on the one hand the diameters 51, 52 of the rivet shanks 41, 42 can be designed as large as possible in order to be able to carry the high currents of 25 A and more. On the other hand, the passage openings 46, 47 in the upper part 15 as small diameter 48, 49 as possible, so that the stability of the upper part made of PTC thermistor 15 does not suffer.

In addition to the production-related not exactly reproducible and unevenly varying distance 54 between the passage openings 46, 47 are in a pre-assembled with the contact rivets 33, 34 upper part 15, the stationary contacts 31, 32 also not symmetrical to the in Fig. 1 at 55 indicated center line of the switch 10, which also extends centrally through the rivet 23 and thus the contact plate 24.

However, the contact surfaces 27 on the contact plate 24 have such a large extent in the radial direction that the stationary contacts 31, 32 always get into secure contact with the contact surfaces 27, even if their distance to the center line 54 varies due to production.

Claims (9)

Method for producing a temperature-dependent switch (10) with a temperature-dependent switching mechanism (11), a housing (12) receiving the switching mechanism (11), which has a lower part (14) and an upper part (15) of PTC thermistor, two extending through the upper part (15) extending contact rivets (33, 34), whose inner heads (37, 38) act as stationary contacts (31, 32) and whose outer heads (35, 36) serve the external connection, as well as one arranged on the switching mechanism (11) and of this moving power transmission member (24) which is temperature dependent with the two stationary contacts (31, 32) in abutment, comprising the steps of: Providing the temperature-dependent switching mechanism (11) on which the current transmission member (24) is already arranged; Providing the lower part (14) for the housing (12); Providing the upper part (15) for the housing (12), which is made of PTC thermistor material and has two through openings (46, 47) for receiving the two contact rivets (33, 34); Mounting the two contact rivets (33, 34) to the passage openings (46, 47); Inserting the derailleur (11) in the lower part (14); and Closing the lower part (14) with the upper part (15), characterized in that the two contact rivets (33, 34) successively and independently inserted into the passage openings (46, 47) and then attached to the upper part (15). A method according to claim 1, characterized in that the contact rivets (33, 34) are thereby fixed to the upper part (15), that their rivet shanks (41, 42) at its free end (43, 44) in a common manufacturing step to a closing head be transformed. Method according to claim 1 or 2, characterized in that the contact rivets (33, 34) with their setting heads (37, 38) form the stationary contacts (31, 32). A method according to claim 1 or 2, characterized in that the contact rivets (33, 34) with their setting heads (37, 38) form the outer heads (35, 36). Method according to one of claims 1 to 4, characterized in that the upper part (15) is manually equipped with the contact rivets (33, 34). Method according to one of claims 1 to 5, characterized in that in the derailleur (11) a bimetal snap-action disc (22) is provided, which is mechanically connected to the current transmitting member (24) and this below its switching temperature against the stationary contacts (31 , 32) presses and lifts above their switching temperature of these. Method according to one of claims 1 to 6, characterized in that in the derailleur (11) a spring snap-action disc (21), which biases the current transfer member (24) in the sense of an abutment against the stationary contacts (31, 32), and a Bimetallic snap-action disc (22) is provided, which lifts the current transfer member (24) above its switching temperature of the stationary contacts (31, 32). Method according to one of claims 1 to 7, characterized in that the spring snap-action disc (21) between the current transmission member (24) and bimetallic snap disk (22) is arranged. Method according to one of claims 1 to 8, characterized in that the current transfer member is an approximately round contact plate (24) which is provided on its surface facing the stationary contacts with two electrically interconnected contact surfaces (27).

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