EP2689448B1 - Overload release, in particular for a circuit breaker - Google Patents

Description

The invention relates to an overload release, in particular for a circuit breaker with a metal strip of at least two different types of metal, around which a heating conductor is wound.

Among other things, the technical characteristics of motor or power protection devices include detecting the temperature by means of wound thermostatic bimetals which are arranged in the current-carrying leads to be monitored electrical consumers.

In electro-mechanical protective devices, in particular in circuit breakers, bimetal or trimetal strips are used as overload triggers. In order to achieve the desired tripping characteristics, the metal strips usually have either a heating coil or a heating package.

Heater windings are metal wires or tapes wrapped around the bimetallic strip. Between bimetallic strip and heating coil is an electrical insulator, for example glass fiber fabric, to prevent a short circuit of the individual heating conductor windings to the bimetallic strip. At the upper end of the bimetallic strip heating conductor and bimetal are welded together.

In electro-mechanical protective devices accordingly bimetallic strips are used. If this current flows through, ie directly heated, then they must be connected in the device not only mechanically but also electrically. These two connections are realized with a weld between the bimetallic strip and the metal part. With this metal part of the bimetallic strip is in the device fixed. At the same time, the current is supplied via the metal part to the bimetallic strip.

In devices for higher currents, the above-described problem of device heating on the one hand and manufacturing and device-related obstacles on the other hand has been solved by using copper-plated steel materials for the metal part. This material can be well welded with the bimetal strips under certain conditions. Due to the steel content, the material is ferromagnetic on the one hand and can thus be integrated into the magnetic circuit of a short-circuit release. On the other hand, the steel content also provides the required rigidity for the metal part. The thickness of the copper cladding is chosen so that the resistance of the metal part, and thus its heating during operation of the device, decreases to the required level.

Economically and technically useful is the use of copper-plated steel strips for the production of metal parts only up to a certain limit. An economic limit is found in the material price, which is about twice as high as that for pure copper strips of the same size. In addition, more expensive in this context, that the punching waste as Mischmetallschrot achieve only low revenues. This results in the economic compulsion to constructively minimize the use of this material in the device and the resulting punching waste. The use of the copper-clad steel material with respect to the current range of the devices is technically limited at the top because the thickness of the copper cladding must increase with increasing current range. At the same time, however, the total sheet thickness of the material should remain the same, so that no separate means of production such as stamping and bending tools, part feeders, mounting devices or welding fixtures are needed. This has the consequence that the steel content in the material decreases. This leads from a certain limit to problems when connecting metal part and bimetallic strip. Farther loses the metal part of the required rigidity for sufficient mechanical fixation of the bimetallic strip. In devices with short-circuit releases, such as circuit breakers, the low steel content in the metal part causes a reduced function in the magnetic circuit of the trigger coil.

An overload release according to the preamble of claim 1 is made DE-B-1149803 known.

Accordingly, the object of the present invention is to provide an overload release, which enables an optimized heat balance, especially for higher current ranges.

This object is achieved by an overload release with the features of patent claim 1. Advantageous embodiments and developments, which can be used individually or in combination with each other, are the subject of the dependent claims.

According to the invention this object is achieved by an overload release, in particular for a circuit breaker with a metal strip of at least two different types of metal, around which a heating element is wound. The invention is characterized in that the mechanical and electrical connection of the metal strip is fully or partially separated, so that when fully pronounced no current flows through the mechanical connection of the metal strip and part of the current flows through the mechanical connection with partial expression ,

The solution according to the invention therefore consists in the fact that the mechanical and the electrical connection of the metal strip, in particular of the bimetallic strip, are separated. As a result, on the one hand, it is possible to achieve an optimized heat balance and, on the other hand, to achieve both manufacturing and device-related advantages. According to the invention, the separation of mechanical and electrical connection can be fully or partially pronounced. In a full version, no current flows through the mechanical connection of the bimetallic strip, with partial expression Part of the electricity flows through the mechanical connection. The separation of the two connections according to the invention eliminates the need for a compromise between mechanical and electrical requirements. The respective connection can thus be optimized.

The mechanical connection and thus the fixation of the bimetallic strip in the device is preferably carried out via a simple steel part. The welding between the steel part and the bimetallic strip is possible due to the material pairing in a simple manner. There is no current flowing through the welding during operation of the device. The thermobimetal strip in the upper part of the circuit breaker is mechanically fixed precisely via the steel part.

The electrical connection of the bimetallic strip is carried out according to the invention directly, that is, without power supply via the metal part, which binds the bimetallic strip mechanically. The current in the current path of the switching device is usually via a copper conductor. This is inventively connected directly to the bimetallic strip. Copper conductors with a small cross-section can be welded directly to the bimetallic strip. Copper conductors with a large cross-section can not be readily welded to the bimetallic strip. Copper conductors with a large cross-section can be soldered to the bimetallic strip under certain conditions. This can be done with a suitable flux and solder.

Another way of soldering the copper wire to the bimetallic strip is to produce at least partially beforehand a surface solderable to a post-free solder on the bimetallic strip. There, the copper conductor can then be soldered. There are several approaches to producing such solderable surfaces on the bimetallic strip. In Trimetallstreifen located inside a copper soul, which can be exposed, the Surface of trimetal strips can be remelted to the copper core, it can be welded to a suitable plate or the surface of the bimetallic strip can be coppered.

Switching devices for higher current ranges almost exclusively so-called trimetal metals are used for the production of the metal strip. These trimetals have a copper core, which is arranged between the active and the passive side. By partial removal of the active or passive side, the copper core can be exposed, for example by milling, broaching, grinding or other manufacturing processes. This creates a copper surface.

If the surface of the trimetallium is sufficiently remelted, copper is deposited from the copper core in the active or passive side. As a result, copper is also on the surface so that it can be soldered there. The remelting can be done for example by a laser beam.

With the help of a small plate can also be produced a solderable surface on the bimetallic strip. The plate has the property that it is weldable both with the bimetallic strip weldable, and with the copper conductor solderable. In this case, the plate can either consist of a homogeneous material, such as brass or bronze, or of a multilayer material such as copper-coated steel. In the case of copper coated steel, the steel side plate is welded to the bimetallic strip. On the outer copper coated side of the copper conductor can be soldered or otherwise connected.

By a complete or partial coppering of the Thermobimetalloberfläche a solderable surface can be generated. The coppering can be done using different methods: It is possible, the starting material for clad the bimetallic strips with copper or coat them galvanically with at least 10μm copper. It is also possible to galvanically coat the stamped bimetallic strips with at least 10 μm of copper before winding. It is also conceivable to coat the stamped bimetallic strips before winding by so-called cold gas spraying with at least 10 microns of copper.

The present invention consists in separating the mechanical and electrical connection of the bimetallic strip in the switching device with current bimetallic strip flowing through. This makes it possible to directly connect a good conductive material with a bimetallic strip. The metal part for mechanical connection of the bimetallic strip can be optimized for its mechanical and magnetic functions. It can be designed as a cost-effective steel component and thus simultaneously opens up the possibility of a rigid fixation of the bimetallic strip. This is from a device technical point of importance. For the connection of bimetallic strip with the fixing steel component, the easily automatable laser welding process can be used, whereby the manufacturing costs are reduced. Since the connection is not current leader, there are fewer requirements for the welded cross-section. This has a positive manufacturing and economic impact. The virtually direct current conduction in the bimetallic strip without the interposition of another metal part makes an important contribution to minimizing the electrical resistance and thus the heating in the current path outside of the bimetallic strip. This is of great importance in terms of equipment, since compliance with the permissible heating poses a challenge due to the increasing power density in the switching device desired by the customer. The separation of mechanical and electrical connection of the bimetallic strip in the switching device allows the saving of expensive copper plated material. In addition, the electrical connection can be improved. This results in larger welded, current-carrying cross-sections, so that the safety of short-circuit currents and overload currents is increased.

• Fig. 1 in einer Frontansicht einen Überlastauslöser aus einem Metallstreifen mit einer Heizleiterwicklung, insbesondere für einen Leistungsschalter mit einer mechanisch und elektrisch getrennten Anbindung des Metallstreifens;
• Fig. 2 in einer Seitenansicht den Überlastauslöser nach Fig. 1;
• Fig. 3 in einer Frontansicht einen Metallstreifen, insbesondere einen Trimetallstreifen mit frei liegender Kupferseele;
• Fig. 4 in einer Seitenansicht den Metallstreifen nach Fig. 3;
• Fig. 5 in einer Frontansicht einen Metallstreifen mit umgeschmolzener Oberfläche;
• Fig. 6 in einer Seitenansicht den Metallstreifen nach Fig. 5;
• Fig. 7 in einer Frontansicht einen Metallstreifen, insbesondere einen Thermobimetallstreifen mit aufgeschweißten Plättchen aus homogenem Werkstoff;
• Fig. 8 in einer Seitenansicht den Metallstreifen nach Fig. 7;
• Fig. 9 in einer Frontansicht einen Metallstreifen, insbesondere einen Thermobimetallstreifen mit aufgeschweißten Plättchen aus mehrschichtigem Werkstoff;
• Fig. 10 in einer Seitenansicht den Metallstreifen nach Fig. 9.

Further advantages and embodiments of the invention will be explained below with reference to embodiments and with reference to the drawing. Here are shown schematically:

• Fig. 1 in a front view of an overload release of a metal strip with a Heizleiterwicklung, in particular for a circuit breaker with a mechanically and electrically separate connection of the metal strip;
• Fig. 2 in a side view the overload release after Fig. 1 ;
• Fig. 3 in a front view of a metal strip, in particular a Trimetallstreifen with exposed copper soul;
• Fig. 4 in a side view of the metal strip Fig. 3 ;
• Fig. 5 in a front view, a metal strip with remelted surface;
• Fig. 6 in a side view of the metal strip Fig. 5 ;
• Fig. 7 in a front view of a metal strip, in particular a bimetallic strip with welded plates of homogeneous material;
• Fig. 8 in a side view of the metal strip Fig. 7 ;
• Fig. 9 in a front view of a metal strip, in particular a bimetallic strip with welded plates of multilayer material;
• Fig. 10 in a side view of the metal strip Fig. 9 ,

Fig. 1 shows an overload release 1 according to the invention with a metal strip 2 and a heating conductor winding 3. The metal strip 2 is preferably formed as a bimetallic strip and is connected to the heating conductor winding 3 via a weld 4. Between the metal strip 2 and the heating conductor 3, an insulating sleeve 5 is arranged. Mechanically, the metal strip 2 is fixed by a metal part 6. Electrically, the connection of the metal strip 2 is formed via a current conductor 7, in particular via a copper conductor. The power connection can be formed, for example, via a welded-on plate 8. The current guide 9 extends over the current conductor 7 and the welded plate 8 in the metal strip. 2

In Fig. 2 is the overload release 1 after Fig. 1 shown from the side. From this representation, the connection points for the mechanical connection of the metal strip 2 to the metal part 6 by means of a weld 10 and the electrical connection via the welding or soldering 11 between the conductor 7 and the welded-on wafer 8.

In Fig. 3 a metal strip 2, in particular a trimetal strip with exposed copper core 12 is shown. In switching devices for higher current ranges, so-called trimetal metals are almost exclusively used for producing thermo-metallic strips. These trimetals have a copper core, which is arranged between the active and the passive side of the trimetal strip. By partial removal of the active or passive side, the copper core can be exposed by milling, broaching, grinding or other manufacturing processes. This creates a copper surface.

In Fig. 4 is the metal strip 2 from the Fig. 3 shown in a side view. Fig. 4 shows the metal strip 2 in one embodiment as Trimetallstreifen. The trimetal strip comprises a passive side 13, an active side 14 and a copper core 15 which is located between the passive side 13 and the active side 14 is arranged. At one end of the trimetal strip is a point exposed from the active side 14 which represents the exposed copper core 12.

In Fig. 5 the metal strip 2 is likewise formed as a trimetal strip which has a remelted surface 16 at one end. If the surface of the trimetallium is sufficiently strongly remelted, copper is deposited from the copper core 15 into the active 14 or passive side 13. As a result, copper is also on the surface so that it can be soldered there. The remelting can be done for example by a laser beam.

In Fig. 6 is the metal strip 2 after Fig. 5 shown in a side view. The side view shows that the remelting of the surface of the trimetal strip extends into the copper core.

Fig. 7 shows a metal strip 2, in particular a bimetallic strip with welded-plate 8. With the help of a small plate a solderable surface can be produced on the bimetallic strip. The plate has the property that it is weldable both with the bimetallic strip weldable, and with the copper conductor solderable. In this case, the plate 8 may be formed either of a homogeneous material such as brass or bronze or of a multilayer material such as copper coated steel. In the case of copper coated steel, the plate 8 is welded to the bimetallic strip with the steel side. On the outer copper coated side of the copper conductor can be soldered or otherwise connected.

In Fig. 8 is a side view of the embodiment according to Fig. 7 represented with a plate of a homogeneous material.

In Fig. 9 a metal strip 2, in particular a bimetallic strip with welded-on plates 17 made of a multilayer material is shown. The multilayer material may be, for example, copper-coated steel. In the case of copper coated steel, the steel side plate is welded to the bimetallic strip. On the outer copper coated side of the copper conductor can be soldered or otherwise connected. Fig. 10 shows this embodiment in a side view.

The present invention consists in separating the mechanical and electrical connection of the bimetallic strip in the switching device with current bimetallic strip flowing through. This makes it possible to directly connect a good conductive material with a bimetallic strip. The metal part for mechanical connection of the bimetallic strip can be optimized for its mechanical and magnetic functions. It can be designed as a cost-effective steel component and thus simultaneously opens up the possibility of a rigid fixation of the bimetallic strip. This is from a device technical point of importance. For the connection of bimetallic strip with the fixing steel component, the easily automatable laser welding process can be used, whereby the manufacturing costs are reduced. Since the connection is not current leader, there are fewer requirements for the welded cross-section. This has a positive manufacturing and economic impact. The virtually direct current conduction in the bimetallic strip without the interposition of another metal part makes an important contribution to minimizing the electrical resistance and thus the heating in the current path outside of the bimetallic strip. This is of great importance in terms of device technology, since due to the increasing power density in the switching device desired by the customer, compliance with the permissible heating represents a challenge. The separation of mechanical and electrical connection of the bimetallic strip in the switching device allows the saving of expensive copper plated material. In addition, the electrical connection can be improved. This results in larger welded, current-carrying cross-sections, so that the safety is increased in short-circuit currents and overload currents.

Claims (9)

1. Overload release (1), in particular for a circuit breaker comprising a metal strip (2) consisting of at least two different types of metal, around which a heating conductor (3) is wound, characterized in that the mechanical and electrical connection of the metal strip (2) is completely or partially separated, with the result that, in the case of complete separation, no current flows via the mechanical connection of the metal strip (2) and in the case of partial separation, some of the current flows via the mechanical connection.
2. Overload release (1) according to Claim 1, characterized in that the mechanical connection of the metal strip (2) is formed by welding to a metal part (6).
3. Overload release (1) according to Claim 1 or 2, characterized in that the electrical connection is formed via a current conductor (7).
4. Overload release (1) according to Claim 3, characterized in that the metal strip (2) is in the form of a trimetallic strip with a copper core (15), which is arranged between an active and a passive side (14, 13), wherein the copper core (15) can be exposed by partially removing the active or passive side (14, 13).
5. Overload release (1) according to Claim 3, characterized in that the metal strip (2) in the form of a trimetallic strip has or embeds copper from the copper core (15) in the surface by virtue of the surface comprising the active or passive side (14, 13) being refused.
6. Overload release (1) according to Claim 5, characterized in that the refusing is in the form of laser jet alloying.
7. Overload release (1) according to Claim 3, characterized in that the metal strip (2) can be electrically connected via both a weldable and a solderable platelet (8).
8. Overload release (1) according to Claim 7, characterized in that the platelet (8) is formed from brass or bronze or copper-coated steel.
9. Overload release (1) according to Claim 3, characterized in that the metal strip (2) has a copper-plated surface.

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