IE56497B1 - Automatic circuit breaker with an arc blow-out field - Google Patents

Description

The present invention relates to an automatic circuit breaker with an arc blow-out field, wherein a rotatably mounted contact arm supports a movable contact member associated with a stationary contact member, the stationary contact member being provided on the transverse member of a contact strip bent into a U-shape and forming a loop connected at one end to an electric circuit, the other end of the loop being free, the contact strip forming a discharge horn and being associated with a group of de-ionizing plates, at least one arc guide plate leading to the de-ionizing plates and the ground plate of the release magnet acting as the support of the stationary contact member and the contact strip, the contact strip extending :widthwise between two ceramic insulating plates.

In a conventional circuit breaker of this type (see QB-A-2 063 566), the contact strip is formed by a single plate.

The curved contact strip serves to conduct the arcs formed between the contacts when a short circuit occurs to the deionization plates. It frequently happens that the discharge of short-circuit arcing is unsatisfactory in this small circuit breaker. An important demand made of small circuit breakers is for a high level of breaking performance. Since, however, the contacts in these breakers are small and light, it is important that when the points are opened the arc is deflected very rapidly away from the con25 tacts to the discharge plates. Several attempts that serve this end have been made. For example, blowout coils, and even blowout strips, which generate a magnetic blowout field in the vicinity of the opened contacts have been provided. However, these are both complex and costly. Above all else, however, they require a great deal of space, which is not available to the required extent in modern, small, narrow circuit breakers.

Thus the present invention provides a circuit breaker > of the aforesaid type having improved discharging short-circuit arcing and in particular an economical and convenient arcing blow35 out system.

According to the present invention there is provided an automatic circuit breaker with an arc blow-out field, wherein a rotatably mounted contact arm supports a movable contact member associated with a stationary contact member, the stationary contact member being provided on the transverse member of a contact strip bent into a U-shape and forming a loop connected at one end to an electric circuit, the other end of the loop being free, the contact strip forming a discharge horn and being associated with a group of de-ionizing plates, at least one arc guide plate leading to the de-ionizing plates and the ground plate of the release magnet acting as the support of the stationary contact member and the contact strip, the contact strip extending widthwise between two ceramic Insulating plates, characterized ln that a ferromagnetic sheet-metal strip is secured to the side of the contact strip remote from the fixed contact member, the contact strip being bent into a Ushape and forming a loop.

The incorporation of the metal strip leads to a considerable improvement in the discharge of short-circuit arcing from the contacts to the deionization plates.

In fixed contacts, and also in moving contacts, should this be required, a sheet iron strip some 0.8 mm thick is xnstal25 led more or less closely on the side that faces away from the contacts. These blowout plates serve as a magnetic return for the short-circuit current flowing through the contact points. The inherent dynamic magnetic field that acts on the contact arcing is considerably increased by this means, and a powerful accelerat30 ing force is applied to the switch arcing.-The blowout sheet metal strip is easily fitted into the U-shaped contact strip.

It is also particularly advantageous and expedient when the installed blowout plate extends across the width of the curved contact strip and its width tapers down towards the free end. Such a structure leads to optimal conditions with regard to dissipation of the arcing.

The present invention can be applied to particular : advantage in the structure according to DE-B 19 66 598 in which the return plate of the tripping magnet serves as the carrier for a fixed contact, since the fixed contact and the blowout plate can be in a form that has an advantageous effect on overall dissipation. Sheet iron plated on one side with copper can be used in place of the separately produced blowout plates.

The present invention will be further illustrated by way of the accompanying drawings, in which:Figure 1 is a plan view of a circuit breaker in accordance with one embodiment of the present invention with a curved contact strip; and Figure 2 is a detail cross-section on the line II-II in Figure 1· The circuit breaker has a narrow housing comprising a casing 1 and a cover (not shown) that is placed on top. The side wall of the casing 1 has three eyelets 2, each of which has a drilled hole and these line up with drilled holes in the cover.

Rivets that hold the housing together pass through these holes.

On the rear side the housing has facing spring hooks 3, one'being spring loaded. These hooks constitute the means for attaching . the housing to rails.

The housing has in each instance a screw connector 4 on , an upper and lower transverse side, and the input and output side power lines are connected thereto. The upper screw connector 4 4 is mounted on a carrier 4' that extends into the housing and carries a bimetal tripping device 5. The bimetal tripping device 5 is connected via a stranded metal (litz) wire 6 to a contact arm Η.

•J that provides a moving contact 8 operating in conjunction with a fixed contact 9. The fixed contact 9 is connected to the coil of a solenoid tripping device 10 that includes a spring-loaded pushrod 21. The other end of the coil is connected via a stranded metal (litz) wire 11 to the lower screw terminal 4.

The ccntact arm 7 is mounted on a shaft 12 in such a manner that it can pivot and on its part that faces the front side it bears a pivotable three-arm locking lever 14. The bimetal tripping device 5 acts on one arm of the locking lever 14 via the IO adjustable grub screw. The pushrod 21 of the solenoid tripping device 10 acts on the second arm. The third arm of the locking arm 14 operates in conjunction with an arm of the detent pawl 15 mounted on the front end of the contact arm 7 so as to be able to pivot about a shaft 16. A connector 17 is articulated onto the other end of the detent pawl 15, and the other end of this connector is articulated onto an arm of the pivotably mounted handle lever 18, the grip portion of which extends through an opening in the side wall at the front 13. The handle lever 18 is loaded by a helical spring 19 to move the handle lever into the position 20 with the grip portion uppermost, this corresponding to contacts being open. A pull-off spring 20 acts on the contact arm 7.

Within the arcing chamber 21, in which the contacts 8 and 9 are located, there is also a group of deionization plates 22. A discharge plate 23 from the carrier 4' and a discharge pC plate 24 fron the solenoid tripping device 10 are parallel to the deionization plates 22. The fixed contact 9 is a component part of a contact strip 25, that is connected rigidly to the solenoid tripping device 10 and connected electrically to the coil of this solenoid. The looped contact strip 25 is of U-shape, of which 30 one arm begins at the face of the solenoid tripping device 10, of which the angle formed by this arm and the bridge forms contact 9, and the second arm of which ends after the second angle with the free end on the face edges of the deionization plates 22. Λ sheet-metal strip 26 is inserted in the contact strip , and this matches the contact strip 25 throughout its entire length. The thickness of the inserted metal strip 26 is signi5 ficantly less- than that of the contact strip 25. There is no rigid internal surface connection between the curved contact strip 25 and the inserted metal strip 26.- The contact strip 25 and the metal strip 26 extend, widthwise, between two ceramic in- 9 sulator discs 27 of which only the one on the base of the casing IO 1 is shown in Figure 1. These two insulating discs 27 define the Φ portion of the arcing chamber that is not occupied by the group of deionization plates 22.

Claims (3)

1. CIAIMS

1. An automatic circuit breaker with an arc blow-out field, wherein a rotatably mounted contact arm supports a movable contact member associated with a stationary contact member, the stationary contact member being provided on the transverse member of a contact strip bent into a U-shape and forming a loop connected at one end to an electric circuit, the other end of the loop being free, the contact strip forming a discharge horn and being associated with a group of de-ionizing plates, at least one arc guide plate leading to the de-ionizing plates and the ground plate of the release magnet acting as the support of the stationary contact member and the contact strip, the contact strip extending widthwise between two ceramic insulating plates, characterized in that a ferromagnetic sheet-metal strip is secured to the side of the contact strip remote from the fixed contact member, the contact strip being bent into a U.shape and forming a loop.

2. An automatic circuit breaker according to Claim 1, characterized in that the secured sheet-metal strip extends over the width of the bent contact strip and tapers with the contact strip towards its free end.

3. An automatic breaker according to Claim 1, substantially as herein described with reference to the accompanying drawings