Positive off toggle mechanism

Details Positive off toggle mechanism Positive off toggle mechanism

2000-02-18

2001-04-24

Gellner, Michael L. (Department: 2832)

Electricity: circuit makers and breakers

Toggle mechanisms

C335S167000

Reexamination Certificate

active

06222143

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of electrical circuit breakers, and more particularly to a circuit breaker which indicates an OFF condition only when contacts are separated.
BACKGROUND OF THE INVENTION
In general the function of a circuit breaker is to electrically engage and disengage a selected circuit from an electrical power supply. This function occurs by engaging and disengaging a pair of operating contacts for each phase of the circuit breaker. The circuit breaker provides protection against persistent overcurrent conditions and against the very high currents produced by short circuits. Typically, one of each pair of the operating contacts are supported by a pivoting contact arm while the other operating contact is substantially stationary. The contact arm is pivoted by an operating mechanism such that the movable contact supported by the contact arm can be engaged and disengaged from the stationary contact.
There are two modes by which the operating mechanism for the circuit breaker can disengage the operating contacts: the circuit breaker operating handle can be used to activate the operating mechanism; or a tripping mechanism, responsive to unacceptable levels of current carried by the circuit breaker, can be used to activate the operating mechanism. For many circuit breakers, the operating handle is coupled to the operating mechanism such that when the tripping mechanism activates the operating mechanism to separate the contacts, the operating handle moves to a fault or tripped position.
To engage the operating contacts of the circuit breaker, the circuit breaker operating handle is used to activate the operating mechanism such that the movable contact(s) engage the stationary contact(s). A motor coupled to the circuit breaker operating handle can also be used to engage or disengage the operating contacts. The motor can be remotely operated.
A typical industrial circuit breaker will have a continuous current rating ranging from as low as 15 amps to as high as several thousand amps. The tripping mechanism for the breaker usually consists of a thermal overload release and a magnetic short circuit release. The thermal overload release operates by means of a bi-metallic element, in which current flowing through the conducting path of a circuit breaker generates heat in the bi-metal element, which causes the bi-metal to deflect and trip the breaker. The heat generated in the bi-metal is a function of the amount of current flowing through the bi-metal as well as for the period of time that that current is flowing. For a given range of current ratings, the bi-metal cross-section and related elements are specifically selected for such current range resulting in a number of different circuit breakers for each current range.
On occasion, one or more movable contacts may be inadvertently welded to their respective stationary contacts due to, for example, excessive arcing or overcurrent. When this happens, it is desirable for the handle to not be positionable in the OFF position as to do so would mislead workers into believing that equipment and circuits connected to the load terminals of the circuit breaker were not electrically powered when, in fact, they would be.
Thus, there is a need for a circuit breaker to have a handle which is not positionable in an OFF position when contacts are welded together. There is also a need for a circuit breaker to have a positive “OFF” handle position to alert a worker that the contacts are welded together, or are otherwise inseparable.
SUMMARY OF THE INVENTION
The present invention provides a positive “OFF” toggle mechanism for a molded case circuit breaker having “ON”, “OFF”, and “TRIPPED” conditions and corresponding handle positions. The circuit breaker includes a pair of contacts, one of which is coupled to an operating mechanism having a pivoting member. The positive “OFF” toggle mechanism includes a lower toggle member having a first end operatively coupled to the contact coupled to the operating mechanism and a second end coupled to a toggle pivot pin; an upper toggle member having a first end coupled to the toggle pivot pin and a second end in operative contact with a toggle pin mounted on the operating mechanism. The positive “OFF” circuit breaker further includes a catch member mounted on the pivoting member of the operating mechanism, with the catch member arranged to engage the second end of the upper toggle when the circuit breaker is in the welded condition and the pair of contacts remain together.
The present invention also provides a positive “OFF” toggle mechanism for a circuit breaker having an operating mechanism including a handle and a moveable contact arm, a trip bar, a line terminal, a load terminal and a cover. The positive “OFF” toggle mechanism includes a lower toggle bar, having a first and a second end, with the first end pivotally coupled to the movable contact arm. The toggle mechanism further includes an upper toggle bar, having a first end and a second end, with the second end pivotally coupled to the second end of the lower toggle bar and with the first end of the upper toggle bar having a cam finger. A pivot pin is mounted on the operating mechanism and aligned to engage the first end of the upper toggle bar. The toggle mechanism further includes a handle arm associated with the handle, with the handle arm having a cam surface aligned to selectively engage the cam finger of the upper toggle bar when the operating mechanism is in a welded position and the movable contact arm has not moved, wherein the operating mechanism is prevented from being moved to an “OFF” position.
The present invention further provides a molded case circuit breaker including a molded housing provided with a removable breaker cover, a first terminal and a second terminal mounted in the case, a contact electrically coupled to the first terminal, a moveable contact electrically coupled to the second terminal, and an operating mechanism having a pivoting member moveable between an “ON” position, an “OFF” position and a “TRIPPED” position, wherein the pivoting member is coupled to the moveable contact. The circuit breaker also includes an intermediate latching mechanism mounted in the housing and coupled to the operating mechanism, a trip unit having a trip bar and coupled to the moveable contact and the second terminal with the trip unit in selective operative contact with the intermediate latching mechanism; and an accessory socket formed in the removable breaker cover on either side of an opening for the pivoting member; with the accessory socket in communication with the housing and configured to accept a plurality of different types of accessories. The circuit breaker further includes an accessory cover sized to cover the accessory mounted in the accessory socket, and a positive “OFF” toggle mechanism. The positive “OFF” toggle mechanism includes a lower toggle bar having a first and a second end, with the first end pivotally coupled to the movable contact arm; an upper toggle bar, having a first end and a second end, with the second end pivotally coupled to the second end of the lower toggle bar and with the first end of the upper toggle bar having a cam finger; a pivot pin mounted on the operating mechanism with the pivot pin aligned to engage the first end of the upper toggle bar; and a handle arm associated with the handle. The handle arm is provided a cam surface aligned to selectively engage the cam finger of the upper toggle bar when the operating mechanism is in a tripped position and the movable contact arm has not moved, wherein the operating mechanism is prevented from being reset.
The present invention still further provides a circuit breaker including a molded housing including a base and a cover, a means for connecting a load to the circuit breaker, mounted in the housing; a means for connecting an electrical line to the circuit breaker; and a means for coupling electrically to the means for connecting an electrical line. The circuit breaker also includes a movable means for

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