Electricity: circuit makers and breakers – Liquid contact – Time delay
Patent
1987-12-17
1989-07-18
Macon, Robert S.
Electricity: circuit makers and breakers
Liquid contact
Time delay
H01H 3306, H01H 932
Patent
active
048495913
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electromechanical protection switching apparatus with current threshold.
Such a switching apparatus is described in French Pat. No. 2 563 939. It includes in a case a breakable electric circuit which includes a magnetic trip, at least on separable fixed contact and mobile contact, as well as an arc breaking screen interposable between the contacts during a separation thereof caused by the actuation of the magnetic trip in response to an overcurrent or a short circuit. In French Pat. No. 2 540 665, such a device is also described in which the screen has a front surface able to be applied at the end of travel against a stop of the case.
Such switching apparatus operate satisfactorily. However, it can be observed that the arc breaking screen is projected at high speed towards its stop by the plunger of the magnetic trip. It reaches its stop with a very high speed, sometimes greater than 20 m/s and with keen acceleration capable of exceeding 400 g. This is observed particularly at the periphery of rotary breaking screens.
The screen risks then either breaking the stop or being itself broken. If the screen and/or its stop are reinforced, the screen risks bouncing and letting the arc phenomenon continue to exist, which adversely affects the operation of the apparatus and its lifespan. In addition, such reinforcement causes an increase of size, which is undesirable in the case of modular apparatus.
The purpose of the invention is to overcome these drawbacks and to prevent the continuation of the arc phenomenon as soon as this latter has been destabilized by the breaking screen, using simple, compact and efficient means. It also aims at integrating these means simply in the case of the apparatus. In accordance with the invention, the stop associated with the case for receiving the breaking screen is deformable. The stop is preferably at least partly resilient and adapted so as not to restore immediately to the breaking screen the kinetic energy received therefrom, the delay in restoring this energy being determined so that return of the screen only takes place after total extinction of the arc.
The stop may advantageously be attached to a part of the case of the apparatus and be integrally molded therewith; to balance the reaction on the screen, two deformable stops are preferably provided disposed opposite each other on two mutually assemblable parts of the case.
The deformable stop may have at least two zones of different resilience, the zone of highest resilience receiving the impact of the screen and being applied on the zone of lower resilience, so as to ensure a graduated deceleration of the screen. When the breaking screen is of the rotary type, the stop is preferably disposed between the periphery of the screen and the axis of rotation thereof, while being close to the striking center of the screen, so as to attenuate the reaction on the pivots of the screen .
Other features and advantages of the invention appear in greater detail from the following description.
In the accompanying drawings:
FIG. 1 shows schematically, in elevation, a switching apparatus having an arc breaking screen and a deformable screen stop in accordance with the invention;
FIG. 1 shows, on a larger scale, the detail A of FIG. 1;
FIG. 3 is a sectional view through III--III of FIG. 2;
FIG. 4 shows on a larger scale the crushing of the stop by the screen; and
FIG. 5 is a partial section through the plane V--V of FIG. 4.
The switching apparatus 10 shown in FIG. 1 is an isolating cut-out switch including a case 11 and, in this case, a breakable electric circuit which includes a magnetic trip 12, as well as a fixed contact 13 and a mobile contact 14. Apparatus 10, which could also be a contact breaker or contact maker-breaker, controls an external circuit capable of being connected to terminals 15, 16. The current flows, for example, from terminal 15 to terminal 16 through the mobile contact 14, the fixed contact 13 and the trip 12 via the connections shown with broken lines. Trip 12 acts on the mobile c
REFERENCES:
patent: 3576967 (1971-05-01), Jeffries
patent: 4647741 (1987-03-01), Belbel et al.
patent: 4659887 (1987-04-01), Belbel et al.
Comtois Patrick
Moreau Luc
Nourry Daniel
Paggi Serge
Drucker William A.
La Telemecanique Electrique
Macon Robert S.
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