DE9214940U1 - Temperature monitor - Google Patents

Description

The invention relates to a temperature monitor with a switching mechanism and a PTC element connected in parallel to it.

A temperature monitor with a PTC element connected in parallel to the switchgear is a self-holding temperature monitor. The switchgear has a bimetal element as an active part. As long as the switchgear is closed, the switchgear has only a low electrical resistance, so that the current flows essentially through the switchgear. If a device that is to be protected by the temperature monitor and is located in its vicinity reaches an excess temperature, the bimetal switchgear switches from its closed to its open state so that no more current can flow through the switchgear. This results in a sufficient current flow through the PTC element, which is heated up by the current flow and the bimetal element

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of the switching mechanism continues to heat up. This prevents the switching mechanism from cycling and thus the electrical device to be protected from switching on and off, as would be the case if, after the electrical device was switched off by opening the bimetal switching mechanism, it cooled down again so that the bimetal switch would switch back to its closed state without the fault in the device to be protected being rectified.

The invention is therefore based on the object of creating a self-holding temperature monitor in which a higher power conversion is possible, whereby more precise switching can be achieved.

According to the invention, the above-mentioned object is achieved in a temperature monitor of the type mentioned at the outset by a heating resistor connected in series with the switching mechanism and arranged close to it.

In a preferred embodiment, it is provided that the heating resistor is arranged below the switching mechanism and that the switching mechanism rests with its base on the resistor with an insulating layer interposed. Developments provide a ceramic carrier, whereby in particular the resistor is designed as a thick-film resistor on the ceramic carrier.

By arranging the series resistor under the switching mechanism, very defined switch-off times can be set with only slight deviations from the target value. With a thick-film resistor under the switching mechanism and the resulting good thermal conductivity and heat transfer to the switching mechanism, a surface power of approx. 2 W/mm ² can be achieved up to the time the switching mechanism switches off.

According to another embodiment, it can be provided that the PTC element is also carried by the carrier, whereby in further developments it is particularly provided that soldering points are provided on the carrier for connecting a strand of the PTC element and for fastening and electrically connecting the switching mechanism.

The actual electrical circuit is such that the switching mechanism and heating resistor are connected together in parallel to the PTC element.

The temperature monitor according to the invention ensures

2 A power of up to 2 W per mm is achieved, which ensures greater switch-off accuracy.

The ceramic is usually an aluminum oxide ceramic.

The entire object may be surrounded by insulation, such as shrink wrap or a plastic casing.

Further advantages and features of the invention emerge from the claims and from the following description, in which a preferred embodiment of the invention is explained in detail with reference to the drawings.

Figure 1 shows a temperature monitor according to the invention in vertical section; 30

Figure 2 shows a horizontal section through the temperature monitor of Figure 1;

Figure 3 is a circuit diagram of the temperature monitor according to the invention;

Figure 4 is a schematic representation of the ceramic plate with its applications

and

Figure 5 is a side view of the ceramic plate provided with the coatings of Figure 4 in the direction of arrow V.

The temperature monitor 1 according to the invention has a ceramic plate 2 provided with conductive and insulating coatings as a carrier. On the ceramic plate 2 sits an encapsulated switching mechanism 3 with a bimetal switching element (not shown). Furthermore, next to the switching mechanism 3 sits a PTC module 4.

Switching mechanism 3 and PTC element 4 are electrically connected in parallel. A first contact wire 8 is soldered to the cover part 7 of the switching mechanism 3, which is insulated from the housing 6 of the switching mechanism 3. This wire also runs over the PTC element 4 (at 9) and is connected to it there. A second wire 11 is soldered directly to the carrier 2 and is initially in electrically conductive connection with the underside of the PTC element 4.

The switching mechanism 3 can be provided with an insulating cap 12 which, on the one hand, leaves the connection of the strand 8 to the cover part 7 free, but on the other hand also does not insulate a base area of the housing 6 of the switching mechanism 3.

Starting from the connection area 11 connected to the strand 11a, the carrier 2 has an electrical conductor track 14 which runs approximately centrally below the switching mechanism 3

(Fig. 3). From there, the track 14 is in contact with a thick-film resistor 16, which in turn is in contact with a conductor track 17 - so that the thick-film resistor 16 is electrically connected between the conductor track 14 and the conductor track 17 - whereby the conductor track 17 is designed as a soldering point for the switching mechanism 3 and is connected to it.

The remaining area of the carrier 2, but in particular the resistor 16, can be covered by an insulating layer, so that the resistor 16 is insulated from the remaining base area of the housing 6 of the switching mechanism 3.

The PTC element 4 is attached to the carrier 2 at the soldering point 19, which is electrically connected to the conductor 17, so that it is electrically connected in parallel to the switch 6.

0 The inventive design of the temperature monitor creates a temperature monitor that enables high performance conversion, whereby the risk of temperature shock is largely excluded.

Claims (8)

PATENT ATTORNEYS Diii-iNO HEINER LICHTI DIIM..-PIIYS. DR. Rl-RNAT. JOST LEMPERT DiiM-iNG HARTMUT LASCH D-7500 KARLSRUHE 41 (DURLACH) BIRGWALDSlRASSH 1 TIiLHK)N: (0721) 9432SI5 Tl-IJ-COPY: (0721) 9432840 05 Thermik Gerätebau GmbH Im Altgefäll 8 D-7530 Pforzheim 11600.7/92 Le/es 02 November 1992 10 15 Protection claims 1. Temperature monitor with a switching mechanism and a PTC element connected in parallel to it, characterized by a heating resistor (16) connected in series to the switching mechanism (3) and arranged close to it. 2. Temperature monitor according to claim 1, characterized in that the heating resistor (16) is arranged below the switching mechanism (3). 30 3. Temperature monitor according to claim 1 or 2, characterized in that the switching mechanism (3) rests with its base side on the resistor (16) with an insulating layer (17) interposed. 35 4. Temperature monitor according to one of the preceding claims, characterized by a ceramic carrier (2). 5. Device according to claim 4, characterized in that the resistor (16) is designed as a thick-film resistor on the ceramic carrier (2). 6. Device according to claim 4 or 5, characterized in that the PTC element is also carried by the carrier (2). 7. Device according to one of claims 4 to 6, characterized in that soldering points (11, 17, 19) for connecting a strand (11) of the PTC element (4) and for fastening and electrically connecting the switching mechanism (3) are provided on the carrier (2). 8. Temperature monitor according to one of the preceding claims, characterized in that the switching mechanism (3) and the heating resistor (16) are connected together in parallel to the PTC element (4).