The present invention relates to the field of circuit breakers for low-voltage distribution networks. It relates in particular to a moving contact unit for a contact arrangement in a circuit breaker as claimed in the precharacterizing clause of patent claim 1, and to a contact arrangement having such a contact unit, and to a circuit breaker having this contact arrangement.
Circuit breakers in the form of flush-mounted service switches are used in low-voltage distribution networks for quick and reliable protection of cables, motors, apparatuses and systems to which low voltage is applied against the consequences of overloading and short-circuit currents. Generally, they each have a thermal release with a bimetallic strip, and an electromagnetic release with a coil and an impact-type armature, as well as a contact arrangement which interacts with a quenching device and in general has one or two switching points. Depending on whether it has one or two switching points, the contact arrangement contains one or two stationary contact pieces as well as a moving contact unit which interacts with it/them and has one contact piece or has two contact pieces, which are generally integrated in a contact link.
A moving contact unit of the type mentioned above is described in EP 0 616 350 A1. The described contact unit is part of a contact arrangement of a circuit breaker, and contains an extended contact mount, one of whose ends is mounted such that it can pivot on a stationary shaft that is held in the housing of the circuit breaker, and whose other end is in the form of a contact piece and, when the circuit breaker is in the connected state, is supported on a stationary contact piece of the contact arrangement. The contact mount holds a latching lever, which is mounted on the stationary shaft such that it can pivot, as well as a two-armed lever, whose rotation point is arranged approximately in the center of the contact mount. One arm (which is provided with a striking surface) of the two-armed lever interacts with a tripping pin of a thermal and magnetic release while, in contrast, the other arm is fitted with a latching hook. The latching hook and the latching lever form a latching point (which is generally referred to as a breaker latching mechanism) in the circuit breaker. The breaker latching mechanism is closed during connection of the circuit breaker by tilting a switching lever (which is coupled with a force fit via a transmission bracket to the latching lever) while at the same time loading a spring energy store to a preferred position. When a short-circuit current or overcurrent occurs, the release trips and opens the breaker latching mechanism, via the tripping pin. The spring energy store, which has not been unloaded, rotates the moving contact unit about the stationary shaft, and opens the contact arrangement in the circuit breaker.
The invention, as it is specified in the patent claims, is based on the object of providing a moving contact unit of the type mentioned initially, a contact arrangement having such a moving contact unit, and a circuit breaker with this contact arrangement, which allow a high disconnection rating, with a simple configuration and minor maintenance requirements.
In the moving contact unit according to the invention, a tripping lever is also arranged on the pivoting shaft alongside a contact mount, and a contact piece is placed on the contact mount and is held by at least one prestressed bending spring, which is mounted on the pivoting shaft. These measures allow the contact unit to be fitted easily by plugging the contact mount, the tripping lever and a tripping spring onto the pivoting shaft, and by then fixing these components and the contact piece by means of a bending spring, or possibly two bending springs. In this case, it is particularly advantageous that the bending spring not only fixes the various components of the moving contact part, but at the same time also defines the contact force of the contact piece which rests only on the contact mount. Since the contact piece rests on the contact mount, it can easily be replaced and exchanged for a contact piece which may have different dimensions.
Quick fitting or removal of the moving contact unit according to the invention and simple control of the contact force are made possible by means of a bending spring which has a cylindrical helical spring through which the pivoting shaft passes and which has two limbs which can rotate in opposite directions with respect to one another, one of which limbs is supported on the contact mount, and the other is supported on the contact piece, forming the prestress. A bending spring such as this can easily be plugged onto the pivoting shaft and can be fixed easily by bending up the two lever arms in a simple manner, fixing the contact mount, the contact piece, the pivoting shaft and the tripping lever. The formation of a holding finger, which clasps the contact piece, in the limb which is supported on the moving contact piece holds the contact piece by simple means while, in contrast, the second limb is advantageously held in a groove which is formed in the contact mount.
A particularly robust moveable contact unit is achieved by providing two bending springs which are arranged with mirror-image symmetry on the shaft, or by the bending spring being in the form of a double-torsion spring and having the following components:
two cylindrical helical springs, through each of which the pivoting shaft passes,
a U-shaped connection section which couples the two helical springs with a force fit and is supported on the contact mount, and
two limbs which are respectively connected to in each case one of the two helical springs and are supported on the contact piece, forming the prestress.
In the double-torsion spring, the two helical springs are coupled to one another with a force fit by means of the U-shaped connection section, thus fixing the spring axially. There is therefore no need for any groove on the contact mount to hold one of the limbs of the bending spring.
For reasons relating to a high current carrying capacity and simple manufacture, the contact mount is made from insulating material and holds a contact link, which is fitted with two contact pieces, instead of one contact piece.
A contact force which is defined by the characteristic of the bending spring and acts over a long distance is formed by designing the contact link as follows:
it is U-shaped,
the two contact pieces form the limbs of the U,
the base of the U is in the form of a plate, rests on one surface of the contact mount and, on its side which faces away from the contact pieces, rests on a projection which is formed in the contact mount.
Specifically, when the contact arrangement is being closed, the two contact pieces of the contact link then strike against two stationary contact pieces of the contact arrangement and are then pivoted about a shaft, which is formed by the projection, against the influence of the bending spring. In the process, a defined contact force is produced over a comparatively long distance. This allows unavoidable contact erosion to be compensated for well.
The contact link is held particularly well by the base of the U, which is in the form of a plate, having an opening into which a tab which is integrally formed in the contact mount projects. An arm which is formed in the tripping lever can also be passed through this opening and can be operated by a tripping element of a preferably thermal or magnetic tripping unit.
One exemplary embodiment of the invention will be explained in more detail in the following text with reference to drawings, in which:
In all of the figures, the same reference symbols denote parts having the same effect.
As can be seen, the contact piece 111 is part of a U-shaped contact link 11. The two limbs of the U are formed by the moving contact piece 111 and the corresponding contact piece 112 of the second switching point, which cannot be seen in
As can be seen from
During fitting of the moving contact unit 10, the contact mount 13 and the tripping lever 14 which holds the resetting spring 144 in the groove 143 are plugged together in such a way that the pivoting shaft 12 can be passed through these three parts, as shown in
As can be seen from
When a short-circuit current or overcurrent occurs, a magnetic or thermal release in the circuit breaker is activated, and a tripping element of one of the releases then strikes against one of the two fingers 141 or 145, or against the striking surface 148. The tripping lever 14 is now rotated in the counterclockwise direction against the force of the resetting spring 144, and in the process overcomes a latch which is formed by the tripping lever 14 and the catch 135. The moving contact unit 10, which is subject to the influence of a loaded spring energy store (which is not illustrated), is pivoted in the counterclockwise direction, and the contact arrangement 1 is opened, forming two series-connected switching arcs.
Once the switching arcs have been quenched in the arc quenching device 2, the circuit breaker can be reconnected. In this case, force is transferred from a switching lever system (which is not illustrated) via the transmission bracket 4 that can be seen in
A simplification of the described embodiment of the moving contact unit 10 is achieved by using only one bending spring instead of two bending springs. This bending spring may be one of the two bending springs 51 or 52. The moving contact unit then advantageously has only one moving contact piece 111 or 112. However, in order to make it possible to position the contact links 11 well in addition, a bending spring is provided having two cylindrical helical springs, through each of which the pivoting shaft passes, and having a U-shaped connection section (which couples the two helical springs with a force fit and is supported on the contact mount), and having two limbs which are each connected to one of the two helical springs and are supported on the contact link 11, or on the contact pieces 111, 112, forming the prestress. A spring such as this, which is identified by the reference symbol 53, is shown partially by dashed lines in
Number | Date | Country | Kind |
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04405415 | Jul 2004 | EP | regional |
Number | Name | Date | Kind |
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2370206 | Taylor | Feb 1945 | A |
4595895 | Fujii et al. | Jun 1986 | A |
4618745 | Thompson, III | Oct 1986 | A |
4641001 | Fujihisa et al. | Feb 1987 | A |
5214402 | DiVincenzo et al. | May 1993 | A |
5539167 | Hood et al. | Jul 1996 | A |
6492607 | Bruckert et al. | Dec 2002 | B1 |
Number | Date | Country |
---|---|---|
0577586 | Jun 1992 | EP |
0 570 647 | Nov 1993 | EP |
0570647 | Nov 1993 | EP |
0 616 350 | Sep 1994 | EP |
0 696 041 | Feb 1996 | EP |
02052597 | Jul 2002 | WO |
Number | Date | Country | |
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20060001511 A1 | Jan 2006 | US |