Latch resetting arrangement

Details Latch resetting arrangement Latch resetting arrangement

2000-03-08

2001-07-17

Donovan, Lincoln (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Electromagnetically actuated switches

Latching means

C335S172000

Reexamination Certificate

active

06262644

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to circuit breakers, and, more particularly, to a means for resetting an operating mechanism latch which will not impede the trip time of the operating mechanism.
Circuit breaker operating mechanisms are used to control the opening and closing of separable contacts within a circuit breaker system. These operating mechanisms utilize linkage arrangements to translate the potential energy of biased springs into an output force required to quickly trip the circuit and separate the contacts in the event that a fault condition occurs.
In the prior art circuit breaker operating mechanisms, a torsion spring is typically used to bias two cooperative elements during the resetting of the latching system. For example, in U.S. Pat. No. 4,001,742 entitled “Circuit Breaker Having Improved Operating Mechanism”, a torsion spring biases a primary latch in a counterclockwise direction about a pivot point of the primary latch while also biasing a secondary latch in a clockwise direction about a pivot point of the secondary latch thereby bringing both latches into latching engagement with each other. In the resetting operation of this system, however, the force of the torsion spring is a factor in the interengagement of the latches, and the time required of the mechanism to overcome that force may be significant.
While the torsion springs of the prior art systems adequately allow the elements of the latch linkage system to interengage and reset the operating mechanism, the latch linkage components must be displaced by the operating mechanism prior to the separation of the contacts. In low force output systems, this displacement requires a significant amount of time. The use of a torsion spring, therefore, the force of which must be overcome in the tripping operation, significantly increases the amount of time needed to separate the breaker contacts. An operating mechanism is needed that reduces the amount of time needed to trip the circuit breaker operating mechanism thereby allowing for faster separation of the breaker contacts.
SUMMARY OF THE INVENTION
A circuit breaker assembly includes a housing, a plurality of stationary contacts mounted proximate the housing, a movable contact arm pivotally mounted within the housing and having at least one movable contact disposed thereon, and an operating mechanism for moving the movable contact arm. The operating mechanism includes a cradle assembly pivotally mounted within the housing, a toggle assembly linkably connected to the movable contact aim and the cradle assembly, a handle operably connected to the cradle assembly, and a latch resetting mechanism operably connected to the cradle assembly and configured to retain the cradle assembly thereon.
The inventive latch resetting mechanism eliminates the torsion spring of the prior art systems and utilizes a latching arrangement wherein a secondary latch releasably sustains the primary latch in engagement with a cradle without the use of the spring. The mechanism includes primary and secondary latches. The primary latch is an elongated member having a notch formed therein and having an opening extending laterally therethrough for pivotally mounting the elongated member. The primary latch also includes a foot portion and a tab depending from the elongated member for engaging the cradle assembly. The secondary latch is also an elongated member having a notch formed therein and having an opening extending therethrough for pivotally mounting that elongated member. The secondary latch restingly engages the notched portion of the primary latch to prevent the pivotal motion of the primary latch.
The elimination of the torsion spring in the latching mechanism allows the latching system to be utilized in a circuit breaker operating mechanism having a trip unit that generally has a low force output. Because the force of the spring does not have to be overcome during the tripping operation, the latch linkage can be more easily displaced and the tripping time of the operating mechanism can be significantly educed.


REFERENCES:
patent: 4001742 (1977-01-01), Jencks et al.
patent: 4123734 (1978-10-01), Maier et al.
patent: 4622530 (1986-11-01), Ciarcia et al.

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