Switching device

Details Switching device Switching device

1999-09-24

2001-06-12

Friedhofer, Michael (Department: 2832)

Electricity: circuit makers and breakers

Electric switch details

Contact

C335S046000, C335S016000, C335S193000

Reexamination Certificate

active

06246021

ABSTRACT:

FIELD OF THE INVENTION
The present invention relate to a switching device having a contact arrangement having at least one movable contact member arranged on a rotatable or displaceable contact arm and at least one stationary contact member.
BACKGROUND INFORMATION
German Patent No. 37 25 860 A1 describes a power circuit-breaker having a contact arrangement including a movable contact member arranged on a rotatable contact arm and a stationary contact member, with a stop being provided to limit the movement of the contact arm in opening the movable contact member. When the contact arm has reached its end position, the arm is prevented from dropping back into the closed position of the contact arrangement by a suitable mechanical gripping device. One disadvantage of such a switching device is that there is the risk when opening the contact arrangement that the contact arm might be thrown back by the stop, especially at high switching capacities, before the mechanical gripping device is operative, so the contact arrangement is unintentionally closed again. There are switching devices, where the stop is provided with a damping layer, so some of the impact energy is absorbed. However, it has not been possible previously to prevent recoil of the contact member at a reasonable cost. Instead, the rate of recoil of the contact arm is simply reduced by the damping layer.
French Patent No. 1,048,980 A describes a switching device according to the definition of the species having a contact arrangement having a movable contact member arranged on a contact arm and a stationary contact member, where the switching device includes a stop in the form of a movably arranged braking body that limits the movement of the contact arm in opening the contact arrangement. After impact, the contact arm moves together with the damping buffer belonging to the braking body until it is braked. There is still the risk here that a contact arm striking with a high energy might be thrown back due to the elasticity of the damping buffer made of cured rubber or an equivalent material.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a switching device where the contact arm is braked on reaching its defined end position even in the case of high switching capacities, without then being thrown back by the stop.
The present invention includes a first stop in the form of movably arranged braking body. The first stop is movable as a whole, and the inertias of a contact arm including a movable contact member the braking body that are relevant for impact are approximately equal so that an impact is executed when the contact arm strikes the braking body, so that the contact arm is braked and the braking body is moved. The present invention employs a concept of using a movable braking body as a stop whose material and inertia (i.e., inert mass or moment of inertia) are matched to the contact arm so that when the contact arm strikes the braking body, there is an impact such that the contact arm is strongly braked and the braking body is displaced in a defined direction at a corresponding speed.
The braking body may optionally then be braked by suitable additional means, e.g., a second stop or a spring, after reaching a defined distance. In an advantageous embodiment of the present invention where the braking body is braked by a second stop, a damping body is provided between the braking body and the second stop, braking the movement of the switch arm after it collides with the braking body, if the braking body is in turn moved back into its starting position. This damping body can preferably be used at the same time as a holding element for the braking body. In order for the contact arm not to be struck again by the braking body moving backwards and thus be swung back, it has proven advantageous for the braking body to have a return stop.
In other advantageous embodiments of the present invention, an elastically or plastically deformable material such as lead is used for the braking body. In the latter case, a large portion of the energy of motion of the contact arm can thus be absorbed permanently as soon as the contact member strikes the braking body. In such an embodiment, the permanent deformation of the braking body can also easily be utilized (e.g., by using an inspection window or a pressure sensor, etc.) to display the lifetime of the switching device.
It is advantageous for the braking body to be supported by a guide so that it moves in the direction of impact after impact with the contact arm.
In an advantageous embodiment of the present invention, the switching device is one pole of a power circuit-breaker having two stationary contact members and two movable contact members per pole to be switched, with the movable contact members being attached to the two opposite ends of the contact arm and one braking body being provided for each end of the contact arm. Finally, it is expedient if the contact arm can be pivoted about a centrally positioned axis or if the contact arm is linearly movable.


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