EP2332161B1 - Miniature circuit breaker - Google Patents

Description

The invention relates to a miniature circuit breaker, as used for example in the context of an automotive electrical system. Such circuit breakers are increasingly being used as a replacement for the automotive industry earlier standard flat fuses.

The Flachstecksicherungen used in the automotive industry are standardized in terms of their geometric dimensions. The relevant norm in Germany is DIN 72581-3. The international standard ISO 8820 is currently being prepared in this area. In the latter standard, three sizes are defined for the flat-type fuses, namely "type C (medium)", "type E (high current)" and "type F (miniature)".

Circuit breakers of the above-mentioned type are usually based on the standards developed for flat-type fuses in order to ensure the compatibility of the circuit breakers with plug-in sockets for blade-type fuses. As a miniature circuit breaker is generally referred to here a circuit breaker, which is compatible in terms of its geometric dimensions with a socket for a Flachstecksicherung, in particular a Flachstecksicherung the (smallest) type F according to ISO 8820. Such circuit breakers are sold, for example, by the company Cooper Bussmann under the name "Series 21 X mini circuit breaker".

Circuit breakers of the abovementioned type usually comprise as tripping mechanism a bimetallic snap-action disc, which changes suddenly and reversibly between two curvature positions as a function of the temperature. The Bimetallschnappscheibe is firmly connected in one or more attachment points with a Bimetallkontaktarm. The remote from the attachment points or the free end of the Bimetallschnappscheibe forms or carries a moving contact. The Bimetallschnappscheibe is arranged such that the moving contact is applied to a corresponding fixed contact of a Festkontaktarms, as long as the temperature prevailing in the circuit breaker temperature falls below a predetermined building temperature threshold. In this case, an electrically conductive path between the bimetallic contact and the fixed contact is thus closed via the Bimetallschnappscheibe. As soon as due to an overcurrent prevailing in the circuit breaker temperature exceeds the temperature threshold, the Bimetallschnappscheibe abruptly changes its shape, whereby the moving contact lifted from the fixed contact and the current path is thus separated.

In simple circuit breakers of the type mentioned above, the closure or interruption of the current path takes place exclusively by the temperature-induced change in shape of the bimetallic snap disk. Such circuit breakers work in persistent overload condition, so for example in the case of a persistent even after the first triggering of the circuit breaker intermittently, especially since the circuit breaker gradually cools after tripping, causing the Bimetallschnappscheibe closes the circuit again, and thus the tripping cycle of the circuit breaker again abuts.

More elaborate designed circuit breaker of the above type included in addition to the Bimetallschnappscheibe a separation mechanism that pushes when triggering the circuit breaker between the moving contact and the fixed contact, so that even after the snapping back of the Bimetallschnappscheibe the circuit is interrupted. Such separation mechanisms are for relatively large circuit breaker (eg compatible with ISO 8820 type C), for example in DE 35 26 785 C1 or EP 1 278 226 B1 described.

A generic circuit breaker is off US 6 144 541 A known. The circuit breaker comprises a housing having a housing base of insulating material and a cup-like housing cover placed on the housing base _. In the housing base are two elongated and flat contact arms partially and in terms their longitudinal direction parallel to each other embedded. At an inner end of a first of the contact arms, a fixed contact is arranged. At an inner end of the second contact arm, a bimetallic snap-action disc having a free-end forming or supporting end is mounted in a mounting point such that the attachment point and the moving contact are on an axis parallel to the longitudinal direction of the contact arms. Further circuit breakers in which the attachment point of the Bimetallschnappscheibe and the moving contact are also on a parallel to the longitudinal direction of the Kontaktartne axis are off US 4,363,016 A . US 5 513 063 A and US 5,248,954 known.

The invention has for its object to provide a particularly suitable for miniaturization, especially easy to manufacture and functionally reliable circuit breaker.

This object is achieved by the features of claim 1. Thereafter, the circuit breaker comprises a housing which is formed from a housing base made of insulating material as well as from an attachable to the housing base or attached housing cover. The housing cover is in this case pot-shaped and thus - at least substantially - closed on all of the housing base facing away from five sides. In the housing base two elongate and flat contact arms are partially embedded and parallel to each other with respect to their longitudinal direction. At an inner end of a first of the two contact arms in this case a fixed contact is arranged. At an inner end of the second contact arm, a fastening point is arranged, on which a Bimetallschnappscheibe is mounted, wherein the Bimetallschnappscheibe forms a moving contact in the region of its free end (or a separate moving contact) carries.

The Bimetallschnappscheibe is in this case arranged in the housing, that the attachment point and the moving contact lie on a common, parallel to the longitudinal extent of the contact arms axis.

It has been found that in particular the combination of the longitudinally aligned bimetallic snap-action disc with the pot-like housing cover is particularly advantageous for a simple miniaturization of the circuit breaker. So can be used particularly well by the longitudinal position of the Bimetallschnappscheibe available for this space. In particular, a sufficiently long for a reliable switching behavior Bimetallschnappscheibe due to the longitudinal position of the Bimetallschnappscheibe be arranged on a particularly small space. The use of a pot-like housing cover in this case allows a particularly good accessibility of the electrical components, in particular the Bimetallschnappscheibe, which greatly simplifies the installation of the same. The design principle described above has proved particularly advantageous for the construction of a circuit breaker with the geometric dimensions defined in ISO 8820 Type F (miniature).

In an advantageous embodiment of the housing cover is a one-piece part, which also consists of insulating material, in particular a thermoplastic material.

By completely formed from (electrical) insulating material housing on the one hand, the reliability of the circuit breaker is increased, especially a leakage of current from the housing in case of faulty contact of the housing with an electrically conductive component of the protective circuit and thus the risk of short circuits and current loops on the housing is safely avoided , On the other hand, the completely made of insulating material housing - in contrast to a wholly or partially metallic housing - a very low thermal conductivity, whereby an improved response of the circuit breaker is achieved. Specifically, a relatively low heat loss must be generated in the circuit breaker due to the reduced heat dissipation in case of overload in order to bring this when using a conventional bimetallic snap-action. In addition, the cooling of the circuit breaker is slowed down. A simple intermittent circuit breaker of the type according to the invention therefore has - under the same environmental conditions - a significantly longer trip time than a comparable circuit breaker with metallic housing. The life of the circuit breaker is thereby prolonged and the risk of malfunction due to a prematurely worn bimetallic snap disk is reduced.

Conveniently, the inner end of the second contact arm (hereinafter referred to as Bimetallkontaktarm) free from the housing base, so that the attachment point of the Bimetallschnappscheibe is spaced from the housing base. This distance is in an advantageous embodiment at least 2 mm, preferably between 3 mm and 5 mm, and in particular about 4.5 mm (specifically, for example, 4.65 mm).

Due to the free-standing arrangement of the inner end of the second contact arm of this free end is particularly accessible, whereby the mounting of the Bimetallschnappscheibe is simplified. In particular, the freestanding design of the Bimetallkontaktarms allows the use of a particularly simple, precise and jam-free mounting method in which the snap-mounted first fixed without mechanical bias against the fixed contact on the Bimetallkontaktarm, and the bias of Bimetallschnappscheibe against the fixed contact only in a subsequent adjustment step by bending the inner end of the bimetal contact arm is adjusted. The bend is advantageously carried out about an axis extending transversely to the longitudinal direction of the contact arms. In the final assembly state of the circuit breaker, therefore, the inner end of the second contact arm between the housing base and the attachment point of the Bimetallschnappscheibe is advantageously slightly bent by a transverse to the longitudinal direction of the contact arms axis as a result of the adjustment. It thus extends obliquely to the plane defined by the adjacent region of the Bimetallkontaktarms. The adjusting method described above is considered as an independent invention.

As is usual with circuit breakers of the above-mentioned type, an outer end of each contact arm for forming a plug contact from the housing socket after led out the outside. Analogous to Flachstecksicherungen the two plug contacts are spaced offset parallel in a common plane. The common axis, on the present invention, the attachment point of the Bimetallschnappscheibe and the moving contact are expediently approximately centrally between the plug contacts.

In order to ensure a good hold of the contact arms in the housing base, the contact arms are preferably embedded in a form-fitting manner in the housing base. The contact arms are in particular encapsulated with the material of the housing base.

In a further advantageous variant of the circuit breaker this is provided with a separating element for the electrical separation of the moving contact and the fixed contact. This separating element comprises a separating plate made of insulating material and a push button which protrudes from the housing cover in the assembled state. The partition plate is displaceably guided between a separating position in which the separating plate rests in an insulating manner between the moving contact and the fixed contact, and a release position in which the separating plate releases a contacting of the moving contact and the fixed contact. The separating element is in this case biased by a spring in the direction of the separating position, so that the separating plate automatically assumes the disconnected position when the circuit breaker is triggered. On the other hand, the push button is designed in such a way that the separating plate can be returned to the release position by manual pressure on it. In a comparatively simple embodiment, the separating element is in particular a one-piece plastic injection-molded part. An extended position of the push button corresponds in this case always with the disconnected position of the partition plate, while a depressed position of the push button corresponds to the release position.

When the separator biasing spring is expediently a helical compression spring. This helical compression spring is advantageously placed on a guide pin made of metal, which extends at least substantially over the entire spring length. This realization lies the knowledge on the one hand, that the use of a helical compression spring for reasons of high reliability and high ease of assembly is desirable on the one hand, but that such Wendeldruckfedem on the other hand in the required miniaturization are not kink-proof and therefore require guidance. As is known, the spring-penetrating metallic guide pin forms an extremely space-saving, yet effective way of guiding the helical compression spring. In a manufacturing technology particularly simple embodiment of the guide pin is integrally formed with one of the contact arms, in particular the Festkontaktarm.

Preferably, the guide pin protrudes through the spring into a guide bore of the separating element, in particular the push button, into it, wherein in particular the cross section of the guide bore is approximately adapted to the cross section of the guide dome. The guide pin thus advantageously also serves for direct guidance of the separating element. The separating element is additionally or alternatively, in particular in the region of the separating plate, expediently (also) on a Führungsgrat the other contact arm, in particular so the Bimetallkontaktarms out. For this purpose, the separating element advantageously has a fork-like guide contour, which engages around the guide ridge in a form-fitting manner. The "threading" the guide contour on the Führungsgrat is thereby expediently simplified in that the guide contour has two longitudinally offset guide tines. This embodiment also simplifies the production of the separating element by injection molding. The Führungsgrat may alternatively be formed on the base.

In a particularly advantageous variant of the circuit breaker, the push button and the partition plate are not integral, but designed as separate, mutually displaced guided components. The push button in this case has a driver, which is guided so that it moves the separating plate in the release position upon depression of the push button from its extended position to its depressed position, but that when the depressed position of the push button, the driver is decoupled from the partition plate , By decoupling the driver of the partition plate is a so-called free trip reached the partition plate. As a result of the free release, the separating function of the partition plate can not be rendered ineffective by the fact that the push button is kept permanently in its depressed state. A malfunction of the circuit breaker by abusive or accidentally depressed push button is therefore excluded.

In order to achieve the coupling and decoupling of the driver with the separating plate when pressing and releasing the push button in a simple and comparatively well miniaturized way, the driver is preferably guided on a closed circular path, so that he takes a different path when pressing the push button than when Jump back the push button in the extended position. The driver is guided in particular on a guide ridge, which is formed integrally with one of the contact arms, in particular the Bimetallkontaktarm. To guide the driver on a closed circular path, the driver is preferably guided around this ring guide annularly.

In order to achieve a circuit guide of the driver in a simple way, this is expediently provided with two with respect to the displacement direction of the push button obliquely hired, in particular approximately parallel sliding surfaces. These sliding surfaces are arranged with respect to the above-mentioned Führungsgrates that the driver is deflected when pressing the push button and when extending the push button on each other flat side of the contact arm.

The driver is preferably connected elastically deflectable with the push button. In particular, the driver is integrally connected via an integrally formed on the push button spring arm with this. When pressing the push button from its extended position to its depressed position, the driver is preferably guided so that it is in an elastically deflected state. For simple and quick decoupling of the driver of the partition plate here, the contact arm is provided with an incision through which the driver springs back to a rest position when the Push button has reached its depressed position, so that the driver is quickly and safely decoupled from the separator plate.

The push button advantageously additionally has a second driver. This second driver is arranged such that it abuts in the extension of the push button on the partition plate, so that the push button is held by the partition plate in the depressed position, as long as the partition plate is in the release position.

In an advantageous embodiment, both parts are separately biased by a separate helical compression spring in the direction of the separation position of the partition plate or on the extended position of the push button in a separate embodiment of the partition plate and the push button. Each of these two helical compression springs is hereby placed in the sense of an easily miniaturizable and effective guidance on a separate guide pin of one of the contact arms. Preferably, both helical compression springs are guided on the same contact arm, in particular the fixed contact arm.

Fig. 1

in einer Explosionsdarstellung eine erste Variante eines Schutzschalters mit einem aus einem Gehäusesockel und einem Gehäusedeckel gebildeten Gehäuse, zwei in den Gehäusesockel teilweise eingebetteten Kontaktarmen und einer Bimetallschnappscheibe,

Fig. 2

in perspektivischer Darstellung den Schutzschalter gemäß Fig. 1 in montiertem Zustand mit geschlossenem Gehäuse,

Fig. 3

in Frontansicht die in den Gehäusesockel eingebetteten Kontaktarme des Schutzschalters gemäß Fig. 1,

Fig. 4

in perspektivischer Darstellung den Schutzschalter gemäß Fig. 1 in dem Teilmontagezustand gemäß Fig. 3,

Fig. 5

in Darstellung gemäß Fig. 3 den Schutzschalter gemäß Fig. 1 im Montagezustand, jedoch ohne Gehäusedeckel,

Fig. 6

in Darstellung gemäß Fig. 4 den Schutzschalter gemäß Fig. 1 im Montagezustand ohne Gehäusedeckel,

Fig. 7

in Seitenansicht den Schutzschalter gemäß Fig. 1 im Montagezustand ohne Gehäusedeckel in einem (elektrisch leitenden) Normalzustand,

Fig. 8

in Darstellung gemäß Fig. 7 den Schutzschalter gemäß Fig. 1 in ausgelöstem Zustand,

Fig. 9

in Darstellung gemäß Fig. 1 eine zweite Variante des Schutzschalters, die gegenüber der ersten Variante zusätzlich ein Trennelement und eine Wendeldruckfeder umfasst,

Fig. 10

in Darstellung gemäß Fig. 2 den Schutzschalter gemäß Fig. 9,

Fig. 11

etwa in Darstellung gemäß Fig. 4 die in den Gehäusesockel eingebetteten Kontaktarme des Schutzschalters gemäß Fig. 9 mit aufgeschobener Wendeldruckfeder,

Fig. 12

in Darstellung gemäß Fig. 11 den Schutzschalter gemäß Fig. 9 mit zusätzlich montiertem Trennelement,

Fig. 13

in Frontansicht den Schutzschalter gemäß Fig. 9 im Montagezustand ohne Gehäuse,

Fig. 14

in Draufsicht von oben den Schutzschalter gemäß Fig. 9 im Montagezustand ohne Gehäuse,

Fig. 15

in Seitenansicht den Schutzschalter gemäß Fig. 9 im Montagezustand ohne Gehäuse in seinem Normalzustand,

Fig. 16

in Darstellung gemäß Fig. 1 eine dritte Variante des Schutzschalters, die ein zweigeteiltes Trennelement sowie gegenüber der zweiten Variante eine zusätzliche Wendeldruckfeder umfasst,

Fig. 17

in Darstellung gemäß Fig. 2 den Schutzschalter gemäß Fig. 16,

Fig. 18

in Darstellung gemäß Fig. 11 den Schutzschalter gemäß Fig. 16,

Fig. 19

in Darstellung gemäß Fig. 12 den Schutzschalter gemäß Fig. 16,

Fig. 20

in Darstellung gemäß Fig. 13 den Schutzschalter gemäß Fig. 16,

Fig. 21 bis 24

in jeweils ausschnitthafter Seitenansicht den Schutzschalter gemäß Fig. 16 im Montagezustand ohne Gehäusedeckel in verschiedenen Stellungen des Trennelements beim Rückstellen des Schutzschalters.

Embodiments of the invention will be explained in more detail with reference to a drawing. Show:

Fig. 1

in an exploded view, a first variant of a circuit breaker with a housing formed from a housing base and a housing cover, two in the housing base partially embedded contact arms and a Bimetallschnappscheibe,

Fig. 2

in perspective view of the circuit breaker according to Fig. 1 in assembled condition with closed housing,

Fig. 3

in front view embedded in the housing base contact arms of the circuit breaker according to Fig. 1 .

Fig. 4

in perspective view of the circuit breaker according to Fig. 1 in the partial assembly state according to Fig. 3 .

Fig. 5

in illustration according to Fig. 3 the circuit breaker according to Fig. 1 in the assembled state, but without housing cover,

Fig. 6

in illustration according to Fig. 4 the circuit breaker according to Fig. 1 in the assembled state without housing cover,

Fig. 7

in side view the circuit breaker according to Fig. 1 in the assembled state without housing cover in a (electrically conductive) normal state,

Fig. 8

in illustration according to Fig. 7 the circuit breaker according to Fig. 1 in a triggered state,

Fig. 9

in illustration according to Fig. 1 a second variant of the circuit breaker, which in addition to the first variant comprises a separating element and a helical compression spring,

Fig. 10

in illustration according to Fig. 2 the circuit breaker according to Fig. 9 .

Fig. 11

in representation according to Fig. 4 the embedded in the housing base contact arms of the circuit breaker according to Fig. 9 with deferred helical compression spring,

Fig. 12

in illustration according to Fig. 11 the circuit breaker according to Fig. 9 with additionally mounted separating element,

Fig. 13

in front view the circuit breaker according to Fig. 9 in the assembled state without housing,

Fig. 14

in plan view from above the circuit breaker according to Fig. 9 in the assembled state without housing,

Fig. 15

in side view the circuit breaker according to Fig. 9 in the assembled state without housing in its normal state,

Fig. 16

in illustration according to Fig. 1 a third variant of the circuit breaker, which comprises a two-part separating element and compared to the second variant an additional helical compression spring,

Fig. 17

in illustration according to Fig. 2 the circuit breaker according to Fig. 16 .

Fig. 18

in illustration according to Fig. 11 the circuit breaker according to Fig. 16 .

Fig. 19

in illustration according to Fig. 12 the circuit breaker according to Fig. 16 .

Fig. 20

in illustration according to Fig. 13 the circuit breaker according to Fig. 16 .

Fig. 21 to 24

in each case a partial side view of the circuit breaker according to Fig. 16 in the assembled state without housing cover in different Positions of the separating element when resetting the circuit breaker.

Corresponding parts are always provided with the same reference numerals in all figures.

A first variant of the circuit breaker is initially in the Fig. 1 to 8 shown. As in particular the exploded view according to Fig. 1 can be seen, the circuit breaker 1 comprises in this embodiment a housing 2, which is formed from a housing base 3 and a housing cover 4. The circuit breaker 1 further comprises a Festkontaktarm 5, a Bimetallkontaktarm 6 and a Bimetallschnappscheibe 7. The circuit breaker 1 also includes a fixed contact 8 in the form of a weld plate, a moving contact 9 in the form of a rivet and for attaching the Bimetallschnappscheibe 7 another rivet 10 and another Welding plate 11.

The housing base 3 and the housing cover 4 are made of electrical insulating material, namely a thermoplastic material. The one-piece housing cover 4 is pot-shaped and thus encloses with five closed walls a volume which defines an interior 12 (indicated by a dashed reference arrow) of the circuit breaker 1. The housing cover 4 can be snapped onto the housing base 3 with its open side. Fig. 2 shows the circuit breaker 1 with the housing 2 closed, ie with attached to the housing base 3 housing cover 4th

The contact arms 5 and 6 are bent-stamped parts made of sheet metal, in particular tinned brass, with a flat, rectangular cross-section. In the housing base 3 of the Festkontaktarm 5 and the Bimetallkontaktarm 6 are positively embedded by the contact arms 5 and 6 are encapsulated with the material of the Gehäuesockels 3 in the manufacture of the circuit breaker 1. The contact arms 5 and 6 protrude on an underside 13 of the housing base 3, each with a plug contact 14 from the housing base 3 to the outside. The housing 2, in particular the housing cover 4, have approximately the shape of a Flachquaders with a (housing) narrow side 15 and a (housing) broadside 16. The contact arms 5 and 6 are embedded in the housing base 3 in such a way that the plug contacts 14 parallel to each other and with respect to the housing narrow side 15 approximately centrally and spaced from each other are.

The circuit breaker 1 is based on the standard ISO 8820 type F (miniature) in terms of its external geometrical dimensions, ie corresponds from the outside a type F flat fuse according to this standard, so that the circuit breaker 1 is compatible with a socket for such Flachstecksicherung, i. in such a socket can be inserted.

In view of the housing broadside 16, the plug contacts 14 of the contact arms 5 and 6 are each arranged at the edge. In the housing interior 12, both contact arms 5 and 6 are each guided inwardly toward the housing center, so that an inner end 17 of the Festkontaktarms 5 is disposed over an inner end 18 of the Bimetallkontaktarms 6. As "top" here - regardless of the actual orientation of the circuit breaker 1 in the room - the side facing away from the housing base 3 and the plug contacts 14 side of the circuit breaker 1 is designated.

The inner ends 17 and 18 of the contact arms 5 and 6 are - as in particular from Fig. 3 can be seen - in the direction of the housing broadside 16 centered with respect to a central longitudinal axis 19 ( Fig. 3 ) of the housing 2.

As in particular from the perspective oblique view according to Fig. 4 it can be seen, the inner ends 17 and 18 of the contact arms 5 and 6 - seen in the direction of the housing narrow side 15 - bent out of the defined by the plug contacts 14 center plane 20 of the circuit breaker 1 and extend approximately parallel offset to this center plane 20th Das Innen End 17 of Festkontaktarms 5 is here - in the perspective of Fig. 3 and 4 - Set back from the center plane 20. The inner end 18 of the Bimetallkontaktarms 6 is - again from the perspective of Fig. 3 and 4 - The center plane 20 upstream.

The longitudinal extent of the contact arms 5 and 6, and in particular of the plug contacts 14 of these contact arms 5 and 6, defines a longitudinal direction 21. The direction perpendicular to the longitudinal direction 21 within the center plane 20 is referred to below as transverse direction 22.

For better fixation of the contact arms 5 and 6, the housing base 3 in the transverse direction 22 each edge, and thus approximately in extension of the plug contacts 14, two of a base plate 23 in the interior 12 projecting arms 24 and 25, wherein the Festkontaktarm 5 in the arm 24 and the Bimetallkontaktarm 6 are embedded in the arm 25. The arms 24 and 25 can - again in the transverse direction 22 seen - between them a free space 26, in which the inner ends 17 and 18 of the contact arms 5 and 6 protrude. In other words, both ends 17 and 18 of the contact arms 5 and 6 are free from the base 3 in the interior 12 from. In this area, thus at a distance from the housing base 3, (also freiendseitig) at the inner end 17 of the Festkontaktarms 5 of the fixed contact 8 is welded. Also freiendseitig is at the inner end 18 of the contact arm 6 - thus again at a distance from the housing base 3 - the rivets 10 attached (see in particular Fig. 3 and 4 ).

On the rivet 10, the Bimetallschnappscheibe 7 is welded by means of the welding plate 11 (see in particular Fig. 5 or 6 ). The Bimetallschnappscheibe is in this case in the assembled state - as in particular in the Fig. 7 and 8th recognizable - sandwiched between the rivet 10 and the welding plate 11 is arranged. In the assembled state, the oval-shaped bimetallic snap disk 7 is arranged with respect to its longitudinal extension - in the direction of the housing broadside 16 - centered with the central longitudinal axis 19 (see Fig. 5 ). The moving contact 9 and the spatially coincident with the rivet 10 attachment point 34 of the Bimetallschnappscheibe 7 are thus aligned in particular parallel to the longitudinal direction 21 of the circuit breaker 1 and its contact arms 5 and 6. The end of the Bimetallschnappscheibe 7, with which it is attached to the inner end 18 of the Bimetallkontaktarms 6, hereinafter referred to as the fixed end 27. The opposite longitudinal end of the Bimetallschnappscheibe 7 is free in the interior 12 and is referred to as free end 28 accordingly. At this free end 28 carries the Bimetallschnappscheibe 7 in juxtaposition to the fixed contact 8 and on its fixed contact 8 side facing the moving contact 9 (see in particular Fig. 7 and 8th ; in the illustration according to Fig. 5 is not visible moving contact 9 only indicated by dashed lines).

In its normal position, the Bimetallschnappscheibe 7 according to Fig. 7 arranged obliquely with respect to the median plane 20, that the moving contact 9 is biased against the fixed contact 8, and so via the contact arms 5 and 6, the fixed contact 8, the moving contact 9 and the rivets 10, an electrically conductive connection between the plug contacts 14 is formed , The circuit breaker 1 is thus electrically conductive in the normal state.

The Bimetallschnappscheibe 7 is further formed such that it changes its shape abruptly when its temperature exceeds a design predetermined default trip temperature of preferably 1700 ° C. This change in shape takes place in such a way that the moving contact 9 is lifted off the fixed contact 8, and thus the electrical connection existing between the fixed contact arm 5 and the bimetallic contact arm 6 is disconnected. Fig. 8 shows the circuit breaker 1 in the tripped position.

The change in shape of the Bimetallschnappscheibe 7 is reversible depending on their temperature, so that the Bimetallschnappscheibe 7 in the normal position according to Fig. 7 springs back when its temperature falls below a building-specific predetermined return temperature. In order to avoid frequent switching of the bimetallic snap disk, this optionally has a snap hysteresis, in which the return temperature is lower than the release temperature. The circuit breaker is therefore only at a low compared to the triggering temperature return temperature conductive again.

When mounting the circuit breaker 1, the punched out, curved in shape and provided with the fixed contact 8 and the rivets 10 contact arms. 5 and 6 with the housing base 3 encapsulated and thus embedded in this. Subsequently, the Bimetallschnappscheibe 7 provided with the moving contact 9 is welded to the Bimetallkontaktarm 6 - more precisely to the rivet 10 -. The Bimetallschnappscheibe 7 is first welded so that the moving contact 9 is spaced from the fixed contact 8 or only loosely rests on this, so that the Bimetallschnappscheibe 7 is not initially under a bias. The required bias of the Bimetallschnappscheibe 7 in the normal state is produced only in a subsequent manufacturing step by the inner end 18 of the Bimetallkontaktarms 6 about a 22 extending in the transverse direction and from the housing base 3 sufficiently spaced buckling axis 29 (see Fig. 3 and 5 ) is bent over. The bending of the end 18 takes place in the representation of the Fig. 3 and 5 to the rear, and thus in the direction of the end 17 of the Festkontaktarms 5. The bending is preferably controlled, wherein the bending process is continued until the Bimetallschnappscheibe 7 has reached a predetermined target bias.

The bend of the end 18 thus allows an adjustment of the circuit breaker 1, compensated by the manufacturing tolerances, especially in the embedding of the contact arms 5 and 6 in the housing base 3, and a uniform, precise tripping behavior of the circuit breaker 1 can be ensured.

As a result of this adjustment, the inner end 18 of the Bimetallkontaktarms 6 is slightly inclined in the final assembled state with respect to the center plane 20 of the circuit breaker 1 is arranged (as shown in FIGS Fig. 7 and 8th exaggerated).

In a final assembly step, the housing cover 4 is snapped onto the housing base 3.

In the simple variant according to the Fig. 1 to 8 the circuit breaker 1 operates intermittently. In case of overload, especially in the case of short circuit, the Bimetallschnappscheibe 7 is heated by the electrical power loss until the release temperature is exceeded, and the Bimetallschnappscheibe 7 by leaps and bounds Shape change separates the circuit. Due to the now forcibly collapsing current flow occurs a gradual cooling of the circuit breaker 1, and thus the bimetallic snap 7. As soon as the temperature of the bimetallic snap disk 7 drops below the return temperature, the bimetallic snap disk 7 returns to the normal position, whereby the circuit is closed again. If, at this time, the overload condition, in particular the short circuit, persists, this leads to a renewed electrical overload and as a result to a renewed triggering of the circuit breaker 1. The triggering sensitivity of the circuit breaker 1 is here - significantly improved with a given interpretation of Bimetallschnappscheibe 7 the plastic housing cover 4, which effectively thermally insulates the interior 12 of the circuit breaker 1. Due to the thermally insulating housing 2, the turn-off of the circuit breaker 1 is extended in case of overload, since the cooling of the bimetallic snap disk 7 is slowed down after the release. Thus, both protected by the circuit breaker 1 circuit and the circuit breaker 1 itself is spared.

A second variant of the circuit breaker 1 is based on Fig. 9 to 15 described. This second variant is similar in terms of construction, assembly and function - unless otherwise described below - in the first variant. In particular, the housing base 3, the contact arms 5 and 6, the Bimetallschnappscheibe 7, the fixed contact 8, the moving contact 9, and the rivet 10 and the welding plate 11 with the corresponding parts of the embodiment described above are identical. Instead of the heating resistor 30, the second variant of the circuit breaker 1 according to the Fig. 9 to 15 but a separator 36 and a helical compression spring 37th

The separating element 36 is designed as a one-piece plastic injection molded part and essentially comprises a separating plate 38 and a push button 39.

The housing cover 4 substantially corresponds to the housing cover 4 of the variants of the circuit breaker 1 described above, but deviating from this has in its upper surface a recess 40 through which the push button 39 of the separating element 36 in the installed state protrudes from the housing 2. The Fig. 10 shows the circuit breaker 1 in the assembled state, and in particular protruding from the housing 2 pushbutton 39th

In the assembled state, the helical compression spring 37 and the push button 39 are guided on the Festkontaktarm 5. The fixed contact arm 5 has for this purpose two thin, elongated guide domes 41 and 42. The helical compression spring 37 is in this case pushed onto the outer guide pin 41 (see in particular Fig. 11 ). Subsequently, the push button 39 is pushed onto the guide dome 41 and 42, so that the helical compression spring 37 sandwiched between the arm 24 of the housing base 2 and the push button 39 (see Fig. 12 ). For positively receiving the guide pins 41 and 42, the pushbutton 39 has a receptacle which is substantially adapted to the dimensions of the domes 41 and 42. This receptacle is optionally formed of two separate bores for receiving in each case one of the guide domes 41 and 42 or through a slot-shaped opening in which both guide domes 41 and 42 einliegen together.

In the installed position of the separating element 36, the partition plate 38 is approximately in the transverse direction 22 from the push button 39 and is approximately co-planar with the median plane 20 the inner end 17 of the Festkontaktarms 5 upstream (see Fig. 12 ). It lies thus in particular between the inner end 17 of the Festkontaktarms 5 and the Bimetallschnappscheibe 7. At its side facing away from the push button 39 in the transverse direction edge 22, the partition plate 38 is guided on the inner edge of a longitudinal extension 33 of the contact arm 6, which is approximately in extension of the plug contact 14 into the interior 12 into it. This inner edge thus forms a Führungsgrat 43 for the partition plate 38. The partition plate 38 engages around this Führungsgrat 43 with an integrally formed, fork-like guide contour 44. This guide contour 44 has two, the Führungsgrat 43 front and rear embracing tines 45 and 46 (see in particular Fig. 14 ). The two prongs 45 and 46 of the guide contour 44 are - as in particular from Fig. 15 is recognizable - slightly offset in the longitudinal direction 21 to the "Einfädein" the guide contour 44 on the Führungsgrat 43 of the longitudinal extension 33 to facilitate.

In the installed state, the separating element 36 is displaceably guided on the guide domes 41 and 42 as well as on the guide ridge 43 in the longitudinal direction 21 between a separating position and a release position. In the (in the Fig. 12 and 15 shown) release position, the partition plate 38 is disposed below the fixed contact 8 and the moving contact 9. More precisely, the partition plate 38 - seen in the longitudinal direction 21 - between the fixed contact 8 and the moving contact 9 on the one hand and the end 18 of the contact arm 6 and the attachment point 34 of the Bimetallschnappscheibe 7 is arranged. The partition plate 38 is thus withdrawn from the area of the fixed contact 8 and the moving contact 9, so that the moving contact 9 can touch the fixed contact 8 unhindered. In the (in Fig. 14 shown) separating position is the separating element 36 (compared to the illustration in FIG Fig. 12 ) Move upward, so that the partition plate 38 rests between the fixed contact 8 and the moving contact 9.

The separator 36 is raised by the helical compression spring 37, i. biased in the direction of the release position. Under the spring pressure, the separating element 36 automatically assumes the disconnected position when, when the circuit breaker 1 is triggered, the moving contact 9 is lifted off the fixed contact 8. The partition plate 38 thus pushes between the fixed contact 8 and the moving contact 9 and prevents that upon cooling of the Bimetallschnappscheibe 7, the electrical connection between the fixed contact 8 and the moving contact 9 is closed again.

The release position of the partition plate 38 corresponds to a position of the push button 39, in which the push button 39 is flush with the upper edge of the housing cover 4 or protrudes only slightly from the housing 2 to the outside. This position of the push button 39 is referred to as depressed position.

The separating position of the partition plate 38, in contrast, corresponds to a position of the pushbutton 39, in which - if appropriate - protrudes from the housing 2 as in the depressed position. This position of the push button 39 is hereinafter referred to as "extended position".

By manual pressure on the push button 39, this can be moved back against the spring pressure of the helical compression spring 37 from its extended position to the depressed position, whereby the partition plate 38 is moved back to the release position and the Bimetallschnappscheibe 7 the moving contact 9, if the temperature of the Bimetallschnappscheibe. 7 the return temperature falls below, again on the fixed contact 8 brings to the plant. In the thus restored normal position of the circuit breaker 1, the partition plate 38 strikes under the spring pressure of the helical compression spring 37 from below to the moving contact 9 (see Fig. 15 ) and is thus locked in its release position. In order to avoid unwanted self-release of the circuit breaker 1, for example, under the influence of vibration, the partition plate 38 is at least on its bimetallic snap disk 7 facing front with a sharp upper edge (hereinafter referred to as contact edge 47) provided with the partition plate 38 on the Moving contact 9 is present. The abutment edge 47 is for this purpose in particular, as from the Fig. 12 and 15 emerges outward, thus on the bimetallic snap disk 7, obliquely employed.

The displacement of the push button 39 is limited downwards by a stop 48 which is integrally formed on the arm 24 of the housing base 3. The stop 48 flanks the helical compression spring 37 and is dimensioned sufficiently long to preclude crushing of the helical compression spring 37. At the top, the displacement of the push button 39 is limited by stops 49 which are integrally formed at the lower end of the push button 39, and with which the push button 39 abuts in the extended position on the housing cover 4.

A further improved variant of the above-described embodiment of the circuit breaker 1 is in the Fig. 16 to 24 shown. In this variant are the partition plate 38 and the push button 39 of the separating element 36 realized as separate components which are guided against each other slidably to allow a free release of the circuit breaker 1. The housing base 3, the fixed contact 5, the Bimetallschnappscheibe 7, the fixed contact 8, the moving contact 9, the rivets 10 and the welding plate 11 are in turn identical to the corresponding parts of the embodiments described above. Furthermore, the Bimetallkontaktarm 6 is formed substantially identical to the Bimetallkontaktarm 6 of the embodiments described above. Notwithstanding this, only the longitudinal extension 33 is according to Fig. 16 Compared to the Bimetallkontaktarm 6 of the embodiments described above extended upward, so that at its the Führungsgrat 43 forming inner edge approximately at the same height with the fixed contact 8, a recess 50 is formed. Also, the housing cover 4 substantially corresponds to the housing cover 4 according to Fig. 9 , Only the shape of the recess 40 is in adaptation to a in the embodiment according to Fig. 16 to 24 modified cross section of the push button 39, which here essentially has the shape of a letter "H" - modified. The closed housing 2 with the protruding from the housing 2 push-button 39 is in Fig. 17 shown.

For biasing the partition plate 38 comprises the circuit breaker 1 in the embodiment according to the Fig. 16 to 24 an additional helical compression spring 51, which - is pushed parallel to the helical compression spring 37 - on the guide pin 42 (see Fig. 18 ).

The push button 39 comprises an integrally formed transverse strut 52, which in the assembled state (see Fig. 19 ), the partition plate 38 engages under. At the longitudinal extension 33 of the Bimetallkontaktarms 6 facing free end of the cross member 52 here the guide contour 44 is formed, which - in particular for preventing rotation of the push button 39 - as described above, the Führungsgrat 43 below the incision 50 surrounds. At the free end of the transverse strut 52, a spring arm 53 protruding in the longitudinal direction 21 is furthermore molded, which is provided with a driver 54 at its free end. In the assembled state, the spring arm 53 extends at a small distance to the Guide ridge 43 approximately parallel to the longitudinal extension 33 (FIG. Fig. 19 ), wherein the driver 54 overlaps in the transverse direction 22 with the Führungsgrat 43.

For mechanical stabilization and for improved guidance, a support arch 55 is formed on the partition plate 38, which vaulted over the actual partition plate 38. At its the Festkontaktarm 5 facing (in the illustration Fig. 16 Right) edge of the partition plate 38 is provided with a fork-like guide projection 56 which engages around the guide mandrel 42 in a form-fitting manner in the assembled state. This guide projection 56 serves at the same time as an abutment for the helical compression spring 51, via which the helical compression spring 51 initiates a spring plate, the biasing plate 38 in the direction of its separation position. The housing side, the helical compression spring 51, as well as the helical compression spring 37, supported on the arm 24 of the housing base 3.

In the embodiment according to the Fig. 16 to 24 the push button 39 is guided on Festkontaktarm 5 only by the guide pin 41, which stands for this purpose in a corresponding opening of the push button 39. The guide pin 42 and the patch on this coil spring 51, however, extend without direct interaction with the push button 39 in a recess 57 (FIG. Fig. 19 ) of the latter.

At its longitudinal extension 33 facing (in the illustration Fig. 16 left) edge is an approximately L-shaped driving arm 58 is integrally formed on the partition plate 38. This Mitnehmerarm 58 engages in the installed state, the longitudinal extension 33 and lies close to the (in the diagram according to Fig. 19 facing away from the viewer) back of the longitudinal extension 33 at. The partition plate 38 is thus guided between the guide pin 42, the inner end 17 of the contact arm 5 and the longitudinal extension 33 of the Bimetallkontaktarms 6.

The interaction of the driver 54 with the Führungsgrat 43 and the Mitnehmerarm 58 is below with reference to Fig. 21 to 23 explained in more detail, the circuit breaker 1 each in a fragmentary side view in different Positions of the push button 39 and the partition plate 38 when pressing and then releasing the push button 39 show.

Fig. 21 In this case, first shows the circuit breaker 1 in the released state, wherein the push button 39 is in its extended position, and the partition plate 38 in the disconnected position between the moving contact 9 and the fixed contact 8 not visible here. In this state of the circuit breaker 1, the free end 59 of the driver arm 58 is aligned approximately with the free end 60 of the longitudinal extension 33. The driver 54, however, - arranged in extension of the plane defined by the longitudinal extension 33 - above its free end 60. The spring arm 53 thus protrudes beyond the longitudinal extension 33 in this state. The spring arm 53 is in this case in a relaxed state (also referred to as idle state).

The driver 54 has, as in particular from the Fig. 21 to 24 becomes clear, a roughly diamond-shaped cross-section. The downward or upward surfaces 61 and 62 are aligned obliquely to the longitudinal direction 21 and serve as Abgleitschrägen, where the driver 54 is deflected by the Führungsgrat 43.

When pressing the push button 39, the driver 54 first encounters the upper edge of the longitudinal extension 33 formed at the free end 60. Due to the inclination of the surface 61 and a corresponding inclination of the upper edge of the longitudinal extension 33 of the driver 54 is under deflection of the spring arm 53 to the back of the longitudinal extension 33rd deflected out. He meets here on the free end 59 of Mitnehmerarms 54 and moves it with continued pressing the push button 39 down (see Fig. 22 ). With the Mitnehmerarm 58 and the partition plate 38 is moved downward, in the direction of their release position.

With the reaching of the release position of the driver 54 comes in the region of the incision 50 of the Führungsgrats 43. The upper edge 63 of the representation in accordance with Fig. 21 to 24 invisible incision 50 is in these figures indicated by dashed lines. In the region of the incision 50, the driver 54 out of contact with the longitudinal extension 33, whereby the spring arm 53 snaps back to its rest position and the driver 54 is immersed back into the plane of the longitudinal extension 33 (the position of the driver 54 and the spring arm 53 is in Fig. 23 indicated by dashed lines). By dipping the driver 54 in the recess 50 of the driver 54 is decoupled from the driving arm 58. The thus no longer connected to the push button 39 partition plate 38 is then shifted under the pressure of the helical compression spring 51 back up.

If the Bimetallschnappscheibe 7 is already cooled below its return temperature at this time, and the moving contact 9 therefore rests again on the fixed contact 8, proposes the partition plate 38 as in the embodiment described above on the moving contact 9, whereby the partition plate 38 locked in its release position will (see Fig. 24 ).

If, on the other hand, the bimetallic snap-action disc 7 is still in its released position, the separating plate 38 is again moved under the pressure of the helical compression spring 51 into its separating position, even if the push-button 39 is still held in its depressed position.

When you release the push button 9, this is shifted by the spring pressure of the coil spring 37 upward in the direction of its extended position. The driver 54 strikes with its upper surface 62 at the upper edge 63. Due to the inclination of the surface 62, and a corresponding inclination of the edge 63 of the driver 54 is deflected with continued displacement of the push button 39 with renewed deflection of the spring arm 53 to the front of the longitudinal extension 33 out. The driver 54 is thus past the driver arm 58, and thus decoupled from this, moved upwards.

If at this time the partition plate 38 is locked in its release position on the moving contact 9, the displacement of the push button 39 is limited by the partition plate 38 by the push button 39 with the top of his Cross strut 52 abuts the lower edge of the partition plate 38. The crossbar 52 thus forms another driver, which locks the push button 39 in its depressed position, as long as the partition plate 39 is in its release position.

The partition plate 38, however, is in its disconnected position, the push button 39 is moved under the pressure of the coil spring 37 upwards until it reaches its extended position, and thus the starting position shown in FIG. 25 is reached again. The in the Fig. 21 to 23 shown reset operation of the circuit breaker 1 can thus be restarted. LIST OF REFERENCE NUMBERS 1 breaker 33 Longitudinal extension 2 casing 34 attachment point 3 housing base 35 Central transverse axis 4 housing cover 36 separating element 5 Festkontaktarm 37 Helical compression spring 6 bimetallic 38 separating plate 7 bimetal 39 push-button 8th fixed contact 40 recess 9 moving contact 41 guide pin 10 rivet 42 guide pin 11 welding plates 43 Führungsgrat 12 inner space 44 guide contour 13 bottom 45 prong 14 plug contact 46 prong 15 (Housing) narrow side 47 contact edge 16 (Housing) broadside 48 attack 17 (inner) end 49 attack 18 (inner) end 50 incision 19 central longitudinal axis 51 Helical compression spring 20 midplane 52 crossmember 21 longitudinal direction 53 spring arm 22 transversely 54 takeaway 23 plinth 55 supporting arch 24 poor 56 guide projection 25 poor 57 recess 26 free space 58 driver arm 27 fixed end 59 free end 28 free end 60 free end 29 bending axis 61 area 62 area 63 (upper edge

Claims (21)

1. Miniature circuit breaker (1) having a housing (2), comprising a housing socket (3) made from insulating material, as well as a pot-shaped housing cover (4) that can be fitted or is fitted onto the housing socket (3), wherein two oblong and flat contact arms (5, 6) are embedded in the housing socket (3) partially and parallel to each other with regard to their longitudinal direction (21), wherein a fixed contact (8) is arranged on an inner end (17) of a first of the contact arms (5), wherein a bimetallic snap dome (7) having a free end (28) that forms or bears a moving contact (9) is attached to an inner end (18) of the second contact arm (6) at a fixing point (34), wherein the fixing point (34) and the moving contact (9) lie on an axis (19) that is parallel to the longitudinal direction (21) of the contact arms (5, 6),
   characterised in that,
   the inner end (18) of the second contact arm (6) is bent between the housing socket (3) and the fixing point (34) of the bimetallic snap dome (7) around an axis (29) that runs transversely to the longitudinal direction (21) of the contact arms (5, 6), such that the inner end (18) of the second contact arm (6) is engaged in a slightly sloping manner to a centre plane (20) of the circuit breaker (1).
2. Circuit breaker (1) according to claim 1, wherein the inner end (18) of the second contact arm (6) protrudes from the housing socket (3) such that the fixing point (34) of the bimetallic snap dome (7) is at a distance from the housing socket (3).
3. Circuit breaker (1) according to claim 2, wherein the distance of the fixing point (34) to the housing socket (3) amounts to at least 2mm, preferably between 3mm and 5mm, in particular approximately 4.5mm.
4. Circuit breaker (1) according to one of claims 1 to 3, wherein an outer end of each contact arm (5, 6) projects outwards from the housing socket (3) as a plug contact (14), and wherein the mutual axis (19) of the fixing point (34) and the moving contact (9) run approximately centrally between the outer ends (14) of the contact arms (5, 6).
5. Circuit breaker (1) according to one of claims 1 to 4, wherein an outer end of each contact arm (5, 6) projects outwards from the housing socket (3) as a plug contact (14), and wherein the outer ends of the contact arms (5, 6) as well as the housing socket (3) are formed to be compatible with a socket for a flat plug fuse according to ISO 8820 type F (miniature).
6. Circuit breaker (1) according to one of claims 1 to 5, having a separating element (36) for the electronic separation of the moving contact (9) and the fixed contact (8), which has a separating plate (38) made from insulating material and a push button (39) protruding from the housing cover (4) in the assembled state, wherein the separating element (36) is guided moveably between a separating position, in which the separating plate (38) is enclosed between the moving contact (9) and the fixed contact (8), and a release position, in which the separating plate (38) releases a contact of the moving contact (9) and the fixed contact (8), wherein the separating element (36) is pre-stressed by a spring (37, 51) in the direction of the separating position, and wherein the separating element (36) can be reset by applying pressure on the push button (39) in the release position.
7. Circuit breaker (1) according to claim 6, wherein the spring is a coil compression spring (37, 51) and wherein the spring (37, 51) is fitted onto a first guiding mandrel (41, 42) that is made from metal and extends at least substantially over the entire length of the spring.
8. Circuit breaker (1) according to claim 6 or 7, wherein the guiding mandrel (41, 42) is connected integrally to one of the contact arms, in particular to the first contact arm (5) .
9. Circuit breaker (1) according to one of claims 6 to 8, wherein the guiding mandrel (41, 42) extends into a guiding bore-hole of the separating element (36), in particular of the push button (39).
10. Circuit breaker (1) according to claim 8 or 9, wherein the separating element (36), in particular the separating plate (38), is guided on a guiding ridge (43) of the other contact arm (6).
11. Circuit breaker (1) according to claim 10, wherein the separating element (36) positively encloses the guiding ridge (43) with a fork-like guiding contour (44).
12. Circuit breaker (1) according to claim 11, wherein the guiding contour (44) has two guiding prongs (45, 46) that are offset to one another in the longitudinal direction (21) .
13. Circuit breaker (1) according to one of claims 6 to 12, wherein the push button (39) and the separating plate (38) are formed as separate components and are guided so that they can be moved against one another, wherein the push button (39) has a tappet (54) which is guided in such a way that it moves the separating plate (38), when the push button (39) is pressed from an extended position into a pressed position, into the release position, and that when the pressed position of the push button (39) is reached, it is de-coupled from the separating plate (38).
14. Circuit breaker (1) according to claim 13, wherein the tappet (54) is guided on a closed circuit for coupling with and de-coupling from the separating plate (38).
15. Circuit breaker (1) according to claim 13 or 14, wherein the tappet (54) is guided around a guiding ridge (43) which is formed integrally with one of the contact arms, in particular the second contact arm (6).
16. Circuit breaker (1) according to claim 14 or 15, wherein the tappet (54) has two sliding surfaces (61, 62) which are engaged in a sloping manner with respect to the direction of movement of the push button (39), said sliding surfaces (61, 62) being arranged with respect to the contact arm (6) guiding the tappet (54) in such a way that the tappet (54) is deflected, when the push button (39) is pressed, onto a flat side of the contact arm (6) and, when the push button (39) is extended, onto the other flat side.
17. Circuit breaker (1) according to one of claims 13 to 16, wherein the tappet (54) is connected to the push button (39) in an elastically deflectable manner.
18. Circuit breaker (1) according to claim 17, wherein the tappet (54) is connected integrally to the push button (39) via a spring arm (53).
19. Circuit breaker (1) according to claim 17 or 18, wherein the tappet (54) is guided on one of the contact arms, in particular the second contact arm (6), from an extended position into a pressed position in the deflected state when the push button (39) is pressed, and wherein this contact arm (6) has an incision (50) to decouple the tappet (54) from the separating plate (38), through which the tappet (54) springs back into a neutral position.
20. Circuit breaker (1) according to one of claims 13 to 19, wherein the push button (39) has a second tappet (52), which strikes the separating plate (38) in the extension direction of the push button (39), such that the push button (39) is held in the pressed position as long as the separating plate (38) is situated in the release position.
21. Circuit breaker (1) according to one of claims 13 to 20, wherein the separating plate (38) and the push button (39) are pre-stressed in the direction of the separating position or the extended position separately by a respective separate coil compression spring (37, 51) fitted on a respective separate guiding mandrel (41, 42) of one of the contact arms, in particular the first contact arm (5).

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