Patent Application
20060202785
1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to a trip indicator for a circuit breaker. The invention also relates to circuit breakers including a trip indicator.
2. Background Information
Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 5,341,191 and 5,471,184. Circuit breakers are used to protect electrical circuitry from damage due to a trip condition, such as, for example, an overcurrent condition, an overload condition, an undervoltage condition, or a relatively high level short circuit or fault condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case, or automatically by way of a trip unit in response to the trip condition.
Circuit breakers typically have two or three operating handle positions corresponding to the status of the separable contacts. For example, a three position breaker may include an ON position in which the separable contacts are closed, an OFF position in which the contacts are open, and a tripped position in which the contacts are tripped open. Typically, the handle position corresponding to the tripped position of the contacts is between the ON and OFF positions. However, this is not always the case. In two-position breakers, the tripped operating handle position is shared with the OFF position. Specifically, when the trip condition occurs and the circuit breaker trips, the operating handle is automatically forced to the OFF position. It is difficult to quickly visually determine the status of such circuit breakers. This is problematic and it is even more pronounced when the circuit breaker is only one of a plurality of circuit breakers arranged within the same panelboard or switchboard, perhaps with several breakers already intentionally turned OFF. Under such circumstances, it is nearly impossible to determine which circuit breakers have tripped because the operating handle appears in the same position as it does for the breakers which have been intentionally turned OFF.
To help alleviate this problem, known circuit breaker designs employ a variety of trip and status indicators. For example, it is known to provide a trip flag in the circuit breaker to indicate the tripped condition. Generally, the trip indicator comprises an indicator assembly which interacts with the operating handle or cradle of the circuit breaker in order to position a visual indicia, such as the trip flag, or printed words indicative of the circuit breaker status (e.g., “T”, “TRIPPED”, “ON” or “OFF”), beneath a lens or window which covers an opening in the circuit breaker housing. Typically, the flag or other indicia is actuated, in response to the trip condition, by the cradle. For example, when the cradle unlatches in response to the trip mechanism and pivots, the separable contacts of the circuit breaker are opened. The flag is then reset by relatching the cradle through movement of the operating handle. However, the trip indicia of such indicators are somewhat concealed within the opening in the circuit breaker housing and often can only be clearly seen when viewed from a very close range and substantially straight on through the lens or glass window. This is disadvantageous because, in most circuit breaker applications, many of the circuit breakers are located or positioned at an elevation other than at eye level, thus limiting the effectiveness of the indictor.
Additionally, as previously discussed, in most known trip indicators, the indicator assembly interacts with the operating handle in such a manner that the visual indicia moves therewith. See, e.g., U.S. Pat. No. 6,246,304. Therefore, one can easily reset the circuit breaker from the tripped position by merely moving the operating handle back to the ON position. This is undesirable under certain circumstances where it is advantageous to prevent the breaker from being arbitrarily reset. For example, it is frequently important to evaluate the cause of a circuit breaker trip (e.g., identify the source of the abnormal current condition) before any necessary repairs or corrections can be made in order to resolve the problem. Otherwise, the breaker might continue to trip or damage could occur to electrical equipment in communication with the circuit breaker.
There is a need, therefore, for a trip indicator which provides a visual indication of a tripped circuit breaker condition which can be quickly and easily seen from a variety of viewing positions, and for providing a trip indicator capable of simultaneously locking the breaker in the tripped position in order to, for example, provoke some thought as to why the breaker tripped before simply resetting the handle.
There is, therefore, room for improvement in trip indicators for circuit breakers and in circuit breakers employing trip indicators.
These needs and others are satisfied by the present invention, which is directed to a circuit breaker and trip indicator therefor comprising a trip indicating member which is movable to protrude at one end from the circuit breaker housing in order to provide a visual indication of a tripped circuit breaker condition. At the opposite end, the trip indicating member engages and locks the operating handle in the tripped position. Before the circuit breaker can be reset, the protruding first end of the trip indicating member is physically depressed by the user, thereby preventing the tripped breaker from inadvertently or arbitrarily being reset.
As one aspect of the invention, a trip indicator is for an electrical switching apparatus including a housing having first and second openings, separable contacts enclosed by the housing, and an operating mechanism having an operating handle with a first end and a second end. The first end of the operating handle protrudes from the first opening of the housing and is structured to open and close the separable contacts. The operating mechanism is structured to trip open the separable contacts in response to a trip condition. The trip indicator comprises: a trip indicating member including a first end and a second end, the first end of the trip indicating member having a trip indicia, the second end of the trip indicating member including a first portion and a second portion, wherein the first portion of the trip indicating member is structured to be engaged by the operating mechanism when the separable contacts are not tripped open, in order to prevent the trip indicia from being viewable at the second opening of the housing, and wherein the first portion is further structured to be disengaged and released by the operating mechanism when the separable contacts are tripped open, causing the trip indicating member to move in order that the trip indicia is viewable at the second opening of the housing and the second portion of the second end of the trip indicating member engages and locks the second end of the operating handle.
The operating mechanism may further have a cradle pivotally mounted within the housing proximate the second end of the operating handle. The cradle may be moveable between latched and unlatched positions corresponding to the separable contacts being closeable and tripped open, respectively, the first portion of the second end of the trip indicating member is structured to be engaged by the cradle when the cradle is latched and the separable contacts are not tripped open, thereby preventing the first end of the trip indicating member from being viewable at the second opening of the housing, and the first portion is structured to be disengaged and released by the cradle when the cradle is unlatched in response to the trip condition tripping open the separable contacts.
The trip indicia may be a protrusion of the first end of the trip indicating member which is structured to protrude from the second opening of the housing when the cradle is in the unlatched position and the separable contacts are tripped open, and which is structured not to protrude when the cradle is latched and the separable contacts are not tripped.
The second end of the operating handle may include a recess. The first and second portions of the second end of the trip indicating member may be first and second projections, wherein the first projection is structured to be engaged and disengaged by the cradle when the cradle is latched and unlatched, respectively, in response to the separable contacts being closeable and tripped open, and the second projection is structured to engage the second end of the operating handle at the recess in order to lock the operating handle when the separable contacts are tripped open, the cradle is unlatched and the first end of the trip indicating member is protruding from the housing. The first projection may further include first and second sides. The first side of the first projection may be structured to be engaged by the cradle when the cradle is latched and the separable contacts are not tripped open. The second side of the first projection may be structured to engage the housing in order to prevent the first end of the trip indicating member from protruding therefrom when the separable contacts are not tripped open and the cradle is latched.
The trip indicating member may further include at least one resilient extension structured to provide a bias of the trip indicating member.
As another aspect of the invention, a circuit breaker comprises: a housing including first and second openings; separable contacts enclosed within the housing; an operating mechanism including an operating handle for opening and closing the separable contacts, the operating handle including a first end and a second end, the first end protruding from the first opening of the housing and moving among OFF. ON and tripped positions corresponding to the separable contacts being open, closed and tripped open, respectively; and a trip indicator comprising: a trip indicating member including a first end and a second end, the first end of the trip indicating member having a trip indicia, the second end of the trip indicating member including a first portion and a second portion, wherein the first portion is engaged by the operating mechanism when the separable contacts are not tripped open, in order to prevent the trip indicia from being viewable at the second opening of the housing, and wherein the first portion is disengaged and released by the operating mechanism when the separable contacts are tripped open, causing the trip indicating member to move in order that the trip indicia is viewable at the second opening of the housing and the second portion of the second end of the trip indicating member engages and locks the second end of the operating handle.
The trip indicating member may be biased towards protruding the protrusion of the first end thereof from the second opening of the housing. The trip indicator may be structured such that the separable contacts, when tripped open, cannot be reset unless the protrusion of the first end of the trip indicating member is first depressed against the bias in order that the second projection disengages the recess at the second end of the operating handle which also causes the second side of the first projection to engage the housing thereby preventing the first end of the trip indicating member from protruding therefrom.
The trip indicating member may further include at least one resilient extension which is structured to provide the bias of the trip indicating member. Alternatively, the housing may further include a bias member, which provides the bias of the trip indicating member. The bias member may be a spring.
The trip indicating member may be made from a resilient material having flexural properties and the housing may further include a catch, wherein the first projection moves between an undeflected position and a deflected position. In the undeflected position, the cradle may not engage the first side of the first projection and the second side of the first projection may not engage the catch, in order that the trip indicating member is free to move in accordance with the bias, when the cradle is unlatched and the separable contacts are tripped open. In the deflected position, the cradle may engage the first side of the first projection in order to deflect it, causing the second side thereof to engage the catch and hold the trip indicating member against the bias, thereby preventing it from protruding from the second opening of the housing when the separable contacts are not tripped and the cradle is latched.
As another aspect of the invention, a circuit breaker comprises: a housing including first and second openings; separable contacts enclosed within the housing; an operating mechanism including an operating handle for opening and closing the separable contacts, the operating handle including a first end and a second end, the first end protruding from the first opening of the housing and moving among OFF, ON and tripped positions corresponding to the separable contacts being open, closed and tripped open, respectively, the cradle pivotally mounted within the housing proximate the second end of the operating handle and moveable between a latched position and an unlatched position corresponding to the separable contacts being tripped open in response to a trip condition; and a trip indicator comprising: a trip indicating member including a first end and a second end, the first end of the trip indicating member having a trip indicia, the second end of the trip indicating member including a first portion and a second portion, wherein the cradle engages the first portion of the second end of the trip indicting member when the cradle is latched and the separable contacts are not tripped open, in order that the first end of the trip indicating member does not protrude from the housing, and wherein the cradle disengages and releases the first portion of the second end of the trip indicating member when the cradle is unlatched and the separable contacts are tripped open, causing the trip indicating member to move in order that the first end of the trip indicating member protrudes from the second opening of the housing.
The second portion of the second and of the trip indicating member may be structured to engage and lock the second end of the operating handle when the separable contacts are tripped open, the cradle is unlatched and the first end of the trip indicating member protrudes from the second opening of the housing.
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
For purposes of illustration, the invention will be described as applied to the trip indicator of a circuit breaker, although it will become apparent that it could also be applied to other types of electrical switching apparatus (e.g., without limitation, circuit switching devices and other circuit interrupters, such as, for example, contactors, motor starters, motor controllers and other load controllers) having an operating mechanism with a tripped position.
As employed herein, the term “fastener” refers to any suitable connecting or tightening mechanism expressly including, but not limited to, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “trip condition” refers to any abnormal electrical condition which could cause a circuit breaker to trip expressly including, without limitation, an overcurrent condition, an overload condition, an undervoltage condition, or a relatively high level short circuit or fault condition.
As employed herein, the term “trip indicia” refers to any suitable visual indication of a trip condition, expressly including but not limited to a colored indicator, a light emitting diode (LED), a trip flag, a suitable word (e.g., “TRIPPED”) or a suitable letter (e.g., “T”) or other suitable term or indicia and the exemplary protrusion of the first end of the trip indicating member which protrudes from an opening in the circuit breaker housing in order to indicate the trip condition. Indicia such as the, for example, words “ON” and “OFF” or positive (+) and negative (−) signs, which indicate non-tripped status of the breaker, are also contemplated by the invention.
As employed herein, the term “flexural properties” refers to the resilient nature of the exemplary trip indicating member which is facilitated in large part by the material from which it is made. Specifically, the material is resilient (e.g., flexible) in that it can be temporarily flexed or deflected from a natural position in which no external force is acting upon it, to a deflected position in which it is deflected or displaced from its natural position in response to being engaged and moved by an external force. Upon removing the external force, it will return to the natural position. Certain plastic materials including, without limitation, Lexan® and Delron® are representative resilient materials exhibiting such flexural properties. Lexan® and Delron® resilient materials are commercially available from the General Electric Company having a place of business in Fairfield, Conn.
As shown in
When the circuit breaker 50 is not tripped as shown in
In the example of
Conversely, referring to
In addition to the visual indication provided by the exemplary trip indicator 2, the present invention further provides a locking feature adapted to lock the operating handle 62 in the tripped position (
The aforementioned locking feature of the present invention provides a significant safety feature. It prevents the operating handle 62 from being pivoted in order to reset the circuit breaker 50 arbitrarily, without provoking some forethought. This is important in order to resist merely resetting the tripped breaker 50 without first investigating as to the cause and the source of the trip condition. Resetting the circuit breaker 50 without first determining the cause of the trip condition, could result in the circuit breaker 50 repetitively tripping, or worse, it could result in damage to electrical equipment in electrical communication with the circuit breaker 50. The trip indicator 2 of the present invention resists these undesirable scenarios by not permitting the separable contacts 58 (
It will be appreciated that the present invention contemplates trip indicators (e.g., 2) having a variety of alternative suitable trip indicating member (e.g., 4) configurations other than those described and illustrated herein. For example,
In the example of
Accordingly, the present invention provides a trip indicator 2,102 which not only provides a visual indication of a trip condition, which can be readily viewed from any elevation with respect to the circuit breaker 50, but it also provides an operating handle 62 locking feature which prevents the operating handle 62 from being arbitrarily moved from the tripped position. The unique flexural properties of the trip indicating member 4,104 facilitate the ability and the trip indicator 2,102 to perform this dual function.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.
