Power circuit breaker

A power circuit breaker includes a switching pole enclosure for accommodating at least one switching pole, whose switching contacts, when closed, rest against one another on a predetermined contact plane. It further includes a switching shaft for transferring drive forces to the at least one switching pole. The switching pole enclosure includes a first and a second enclosure shell, which rest against one another along a separating joint running essentially parallel to the contact plane, and in which the switching shaft is mounted by use of at least two switching shaft mounts held on the first enclosure shell. At least one first and one second fastening device, each serving the purpose of connecting the two enclosure shells, is in each case supported on the one hand on the second enclosure shell and on the other hand on one of the switching shaft mounts.

The present application hereby claims priority under 35 U.S.C. §119 on German patent application number DE 103 23 094.7 filed May 16, 2003, the entire contents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to a power circuit breaker.

BACKGROUND OF THE INVENTION

In the event of a short circuit, high operating forces, such as gas pressure forces and current loop forces, occur in power breakers. These have an effect on the components concerned, in particular the enclosure parts which are screwed to one another and which contain the switching chambers, the contact supports, the switching shaft and the mount and support for the switching shaft which are deformed when subjected to the loads. This deformation, in particular owing to the associated reduction in the contact forces on the interacting switching contacts, reduces the ability of the power breaker to withstand surge currents.

A known measure for avoiding this problem is to increase the contact forces. However, this also brings with it an increase in the drive forces and thus a need to increase the dimensions of all of the drive parts.

U.S. Pat. No. 4,899,253 further discloses a way of improving the robustness of an assembled breaker enclosure using interlocking device(s) such as, in particular, dovetailed strips and corresponding grooves. However, these device(s) only affect the width and not the depth of the breaker.

In addition to the problems involved with the required insulation, an enclosure design having steel components or the like is outdated now, not cost-effective and difficult to work with.

SUMMARY OF THE INVENTION

It is therefore an object of an embodiment of the invention to avoid the disadvantages of the known prior art and to create a power circuit breaker which is distinguished by a design which is simple to realize and is subject to little deformation and is able to withstand high surge currents with low required contact forces.

An object may be achieved according to an embodiment of the invention by at least one first and one second fastening device, each serving the purpose of connecting the two enclosure shells, being in each case supported on the one hand on the second enclosure shell and on the other hand on one of the switching shaft mounts. With a design such as this, the force thus flows via the second enclosure shell and the fastening device directly to the switching shaft mounts and the switching shaft.

The bending resistance of the switching shaft thus contributes to relieving the load on the first enclosure shell such that this first enclosure shell can thus correspondingly be formed such that it is not as robust as the second enclosure shell. This makes it possible to achieve a design for the power circuit breaker which can be realized simply, is subject to little deformation, and has an advantageous geometry. The fact that it is subject to little deformation ensures that it is able to withstand high surge currents with small contact forces being required.

One preferred refinement of an embodiment of the invention provides for the second enclosure shell to be ribbed. This reduces the deformability of the second enclosure shell and thus of the remaining components which are directly or indirectly connected to it, as a result of which the ability to withstand surge currents is increased.

In the case of a power circuit breaker in which the switching pole enclosure has pole partitions for the purpose of physically separating adjacent switching poles and in which the two enclosure shells form outer side walls, a further preferred refinement of an embodiment of the invention provides for at least one of the fastening devices to extend in one of the pole partitions and/or one of the side walls. In this manner, there is no need for any additional physical space, in particular any physical space in the switching chambers. Furthermore, no additional insulation is required for the at least one fastening device as a result of this, since the respective pole partition or the respective outer side wall is self-insulating. Tie rods may advantageously be provided as the fastening device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a detail of an illustration of a power circuit breaker10according to an embodiment of the invention. The power circuit breaker10includes a multi-part switching pole enclosure14(of which only one first enclosure shell16, which is in the form of a front wall, is visible) three switching poles22, a switching shaft12and switching shaft mounts18,20. Pole partitions30run between the switching chambers of the switching poles22such that each of the switching poles22is accommodated in a switching pole chamber. In addition, outer side walls31formed by the two enclosure shells16,24contribute to the formation of the outer switching pole chambers.

FIG. 2shows a section through the power circuit breaker10inFIG. 1along the line B—B, which intersects one of the switching shaft mounts20and runs through a pole partition30. Switching contacts11and13of the switching poles22make contact in a specified contact plane15when in the closed position as shown herein. Fastening device26in the form of tie rods, which extend from the second enclosure shell24through the first enclosure shell16to the respective switching shaft mount20and are each arranged in a pole partition30, serve the purpose of connecting the switching shaft mounts20to a second enclosure shell24, which is in the form of a rear wall, of the enclosure14. The two enclosure shell16and24fit against each other along a separation joint17, extending essentially parallel to the contact plane15. The tie rods and the switching shaft mounts20are each connected by way of a screw connection28.

On the opposite side of each of the switching shaft mounts20, the power circuit breaker10has a further screw connection28for the purpose of connecting the switching shaft mount20to the first enclosure shell16. The switching shaft mounts20cause the switching shaft12to bend, the force flowing via the second enclosure shell24, the fastening device26and the screw connection28to the thread of the switching shaft mounts20and finally to the switching shaft12. As a result, the load is reduced on the first enclosure shell16, which, for geometrical reasons, can be designed such that it is not as robust as the second enclosure shell24. The design of the power circuit breaker10according to an embodiment of the invention, which is subject to little deformation, makes it possible for the power circuit breaker10to withstand high surge currents with low contact forces.