Title:
CIRCUIT BREAKER WITH TRIP INDICATOR
United States Patent 3596219
Abstract:
The circuit breaker has a trip lever which normally is latched by a latch mechanism in an untripped position wherein it maintains the contacts in condition to be opened and closed by a manual operator. The latch mechanism releases the trip lever only upon the occurrence of abnormal current conditions whereupon the contacts are opened and the trip lever is returned to a tripped position. An indicator strip of flexible, nonconducting material having an indicating portion at its outer end is carried by the trip lever. The strip is pushed thereby endwise so that the outer end of the strip engages an interior wall of the housing of the circuit breaker and is guided therealong into alignment with a window in the wall, as the lever moves to tripped position, thereby indicating the tripped condition of the circuit breaker. The indicator strip flexes during its movement to and from trip indicating position to facilitate its proper movement.
US Patent References:
Circuit breaker
Taylor - January 1945 - 2367382
Electric circuit breaker
Boller et al. - July 1954 - 2685011
Circuit breaker
Taylor - January 1945 - 2367382
Electric circuit breaker
Boller et al. - July 1954 - 2685011
Application Number:
04/879733
Publication Date:
07/27/1971
Filing Date:
11/25/1969
View Patent Images:
Export Citation:
Assignee:
Square D Company (Park Ridge, IL)
Primary Class:
Other Classes:
337/79
International Classes:
H01H71/04; H01H71/04
Field of Search:
335/17 337/79 200/167
Primary Examiner:
Broome, Harold
Claims:
Having thus described my invention, I claim
1. In a circuit breaker:
2. The circuit breaker according to claim 1 wherein, the strip is directly connected to, and is movable with, said one element.
3. The circuit breaker according to claim 1 wherein said guide means comprise a surface portion of said wall adjacent the window, said indicating portion is moved by said one element into yieldable engagement with, and along, said surface portion of the wall into alignment with said window when the lever element is tripped.
4. The circuit breaker according to claim 3 wherein said one element is pivotally mounted in the housing for rocking about a predetermined axis toward said wall when said trip lever element is released, and the indicator is connected to said one element and is moved thereby generally tangentially of the rocking axis of said one element, indicating portion foremost, into engagement with said surface portion and to tripped indicating position.
5. The circuit breaker according to claim 1 wherein the guide means have a guide surface which is curvilinear and concave toward said one elements, said strip is elongated, the indicating portion is on the outer end portion of the strip, and said one element, guide surface, and strip are related so that, upon tripping, the outer end of said strip engages said guide surface initially while the strip is unflexed, and upon continued rocking movement of said one element to its tripped position, the strip is flexed by engagement with said guide surface to dispose its outer end portion into resilient engagement with said surface.
6. The structure according to claim 4 wherein said one element is the trip lever.
7. The circuit breaker according to claim 5 wherein the strip, at its end portion opposite from its indicating portion, is connected to said one element for limited movement relative to said one element.
1. In a circuit breaker:
2. The circuit breaker according to claim 1 wherein, the strip is directly connected to, and is movable with, said one element.
3. The circuit breaker according to claim 1 wherein said guide means comprise a surface portion of said wall adjacent the window, said indicating portion is moved by said one element into yieldable engagement with, and along, said surface portion of the wall into alignment with said window when the lever element is tripped.
4. The circuit breaker according to claim 3 wherein said one element is pivotally mounted in the housing for rocking about a predetermined axis toward said wall when said trip lever element is released, and the indicator is connected to said one element and is moved thereby generally tangentially of the rocking axis of said one element, indicating portion foremost, into engagement with said surface portion and to tripped indicating position.
5. The circuit breaker according to claim 1 wherein the guide means have a guide surface which is curvilinear and concave toward said one elements, said strip is elongated, the indicating portion is on the outer end portion of the strip, and said one element, guide surface, and strip are related so that, upon tripping, the outer end of said strip engages said guide surface initially while the strip is unflexed, and upon continued rocking movement of said one element to its tripped position, the strip is flexed by engagement with said guide surface to dispose its outer end portion into resilient engagement with said surface.
6. The structure according to claim 4 wherein said one element is the trip lever.
7. The circuit breaker according to claim 5 wherein the strip, at its end portion opposite from its indicating portion, is connected to said one element for limited movement relative to said one element.
Description:
This invention relates to a circuit breaker and trip indicator combination and particularly to an improvement in trip indicator and the manner in which it is incorporated in the circuit breaker.
The principal object of the invention is to provide in a circuit breaker a simple and improved trip indicator for indicating the tripped condition of the circuit breaker.
A more specific object is to provide an indicator which is connected to one of the moving parts of the circuit breaker mechanism so as to be moved thereby to "tripped" indicating position when the circuit breaker is tripped.
A more specific object is to provide an indicator which is connected to the trip lever of the trip mechanism of the circuit breaker and is moved thereby into trip indicating position by movement of the lever to tripped position.
A more specific object is to provide a trip indicator in the form of a simple strip of flexible self-restoring material which is detachably connected to the trip lever and is flexed and moved thereby into a trip indicating position upon tripping of the lever and is restored to its original condition upon movement of the trip lever to untripped or latched position.
Other objects and advantages will become apparent from the following description wherein reference is made to the drawing, in which:
FIG. 1 is a side elevation of a circuit breaker and trip mechanism embodying the principles of the present invention, the cover of the circuit breaker being omitted for clearness in illustration, and showing the circuit breaker in untripped and contact closing condition;
FIG. 2 is a view similar to FIG. 1 showing the circuit breaker in tripped contact opening condition;
FIG. 3 is a fragmentary front view of part of the trip mechanism, and is taken as indicated by the line 3-3 in FIG. 2; and
FIG. 4 is an enlarged fragmentary side elevation of the circuit breaker as shown in FIG. 1, part thereof being shown in section for clearness in illustration and showing particularly the latching mechanism.
As illustrated in the drawings, the circuit breaker trip mechanism and trip lever are such as fully disclosed in U.S. Letters Pat. No. 3,061,697 of A. J. Kralik et al., issued Oct. 30, 1962, and entitled "Thermal and Magnetic Trip Device." Accordingly, only those portions of the circuit breaker herein necessary to show the cooperation between the breaker parts and the indicator are described herein in detail.
In general, the breaker 1 comprises an insulating base 2, and a cover, not shown, which support the components of the circuit breaker. The circuit breaker may be held in a panelboard and connected to one side of a source of electrical energy by clips 3 and 3a. A terminal strip 4 is used to make a connection with the same side of the source in some instances. A load terminal strip 5 is connected to a connector 6 by which the circuit breaker can be connected to a load. The circuit breaker has a set of stationary contacts 10 and a set of movable contacts 11. The contacts 11 are mounted on the carrier 12 which is rockable about a pivot 13. An operating member 14 is also pivoted on the pivot 13 and is operatively coupled to an operating handle or manual operator 15 by means of a transverse pin 16 carried by the member 15 and engaging the sidewalls of a groove 17 in the operator 15.
A U-shaped connecting link 18 has legs with free end portions pivotally connected to the operating member 14 by a pivot 19, and has a bight portion 20 received within the slot 21 formed in the contact carrier 12. A helical operating spring 22 has one end secured to the bight portion 20 of the connecting link 18 and has its other end secured to an upstanding hooklike portion 23 of a trip lever 24. The trip lever 24 is pivotally supported on a transverse pivot pin 25 which is suitably supported within the base 2 of the circuit breaker.
The trip lever 24 is latched in untripped condition by a mechanism, to be described, and when so held the circuit breaker can be operated by the operator 15 to dispose the contacts 10 and 11 in the closed or ON position illustrated in FIG. 1, and in the open or OFF position, selectively.
The trip mechanism is electrically and mechanically connected to the load terminal strip 5 which is secured within the insulating base 2.
The trip mechanism comprises an elongated bimetallic strip 30 which is electrically and mechanically connected at its upper end portion to the upper end portion of the terminal strip 5. The strip 30 has a high expansion portion 30a and a low expansion portion 30b, and carries a yoke or core 31 of magnetic material attached to the lower end of the bimetallic strip 30. The magnetic yoke 31 extends upwardly generally parallel to the bimetallic strip 30 and an end portion of a flexible conductor 32 is interposed between portions of the magnetic yoke 31 and the bimetallic strip 30 and is electrically and mechanically secured to the strip 30, the other end portion of the conductor 32 being connected to the carrier 12 so that the strip 30 carries the current of the circuit associated with the circuit breaker. The strip 30 is so disposed relative to the yoke 31 that the current in the strip 30 causes flux to be created in the yoke 31 which is related in amount to the magnitude of the current in the circuit.
The central portion of the strip 30 is spaced from the back portion of the magnetic yoke 31 by a pair of protrusions 33 formed in the magnetic yoke. The magnetic yoke 31 is provided near its upper end with hooklike armature supports which pivotally support a magnetic armature 34 responsive to the flux created in the yoke 31.
The armature 34 comprises a bimetallic strip having a high expansion portion 34a. Facing and next adjacent the high expansion portion 30a of the strip 30 is a low expansion portion 34b facing inwardly of the circuit breaker. The bimetallic armature is indirectly heated by radiant, conductive, and convective transfer of heat produced by current flowing through the current responsive bimetallic strip 30. An offset lower end portion or finger 38 on the armature 34 extends through a cutout portion 39 in a spring retainer 40 formed by turning the lower end portion of the yoke 31 inwardly of the circuit breaker. A helical compression spring 41 is disposed between the spring retainer cup 40 and a pair of spaced shoulders 42 on the bimetallic armature 34. Normally the spring biases the armature clockwise about its pivotal connection with the yoke 31 so as to provide an air gap between the armature 34 and the pole faces of the yoke 31.
When the amount of flux in the core exceeds a predetermined value, magnetic attraction on the armature 34 overcomes the bias of the spring 41 and causes the armature to swing counterclockwise about its pivot supports. An upper end portion of an ambient temperature compensating bimetallic strip 43 is attached to an upper end portion of the bimetallic armature 34 and extends downwardly substantially parallel to the armature from its point of attachment to engage the releasable trip lever 34. The high expansion portion of the ambient bimetallic strip 43 is affixed adjacent to and faces the low expansion side 34b of the magnetic armature 34. The lower edge face 43a of the bimetallic strip serves as a latch for the trip lever 24 and normally engages an upwardly directed surface 24a at the outer end of the trip lever 24 to hold the trip lever 24 in untripped position.
The path of the current through the trip device is from the terminal strip 5, through the bimetallic strip 30 and flexible conductor 32 to the contact carrier 12, to the movable contact 11 and fixed contact 10, to the strip 4, and then to the spring jaw clips 3 or a flexible conductor, if desired.
Upon the occurrence of an overload in the circuit connected by the circuit breaker, the flow in the current responsive bimetallic strip 30 causes the strip to deflect in a counterclockwise direction about its point of attachment to the terminal strip 5. When the overload is moderate and of relatively short duration, the current responsive bimetal strip 30 flexes slightly, but due to the short duration of the overload the bimetallic armature 34 is not heated sufficiently by radiation, conduction or convection to flex and supplement the flexures of the current responsive bimetal strip 30 and the latching face 43a of the ambient temperature bimetal 43 is not retracted from engagement with the face 24a of the releasable latch lever 24. Upon occurrence of a sustained moderate overload heat produced as a result of the current flow through the bimetallic strip 30 indirectly heats the bimetallic armature 34 and causes it to flex thereby to move and offset the upper portion thereof in a counterclockwise direction about its pivotal connection. This causes the lower edge 43a of the ambient temperature bimetallic strip 43 to move away from the surface 24a to release the trip lever 24.
Upon occurrence of severe overload, the current responsive bimetal strip 30 is heated sufficiently to retract the latching face 43a of the ambient temperature bimetal strip 43 from engagement with the latching surface 24a of the trip lever 24 before heat transfer to the bimetal armature 34 is sufficient to cause flexure thereof to effect tripping in the manner described.
Upon the occurrence of a fault current, the magnetic bimetallic armature 34 is attracted to the pole faces of the magnetic yoke or core 31, thereby disengaging the latching face 43a of the ambient temperature bimetal 43 and the latching surface 24a of the trip lever 24 before the current responsive bimetal flexes in response to the fault.
Thus the trip device provided is one wherein release of the trip lever 24 due to an overload is a function of time as well as magnitude and wherein release due to a fault current is substantially instantaneous.
Upon release of the trip lever 24, the trip lever is rotated counterclockwise about the pin 25 by the spring 22 and carries the operating spring 22 across a line between the point of engagement of the link 18 in the slot 21 of the contact carrier 12 and the pivot 19 of the link 18 on the operating member 14, and thereby causing the spring 22 to open the contacts 10 and 11. Thus the latch lever 24 is swung from the untripped condition in FIG. 1 to the tripped condition in FIG. 2, wherein its outermost or latching end, with the face 24a, is swung toward the front wall of the casing or base 2.
In this connection, the lever 24 is used to operate an indicator for indicating the tripped condition of the circuit breaker. For this purpose the front wall of the circuit breaker base 2, toward which the released trip lever 24 swings, is provided with a window 45. Mounted on the outer end of the trip lever 24 is an indicator 46 which comprises a strip 47. The indicator strip 47 preferably is of fibrous, nonconducting, material which is relatively stiff, but flexible and self-restoring. It may, however, be of other suitable material. The strip 47 is connected at its inner end to the outer end of the trip lever 24 and, lengthwise, extends from its point of connection to the lever 24 toward the window 45. The wall of the base 2 adjacent the window 45 has a curvilinear wall portion 48 which is concave generally inwardly of the base 2 toward the outer end of the trip lever 24. The outer end of the indicator strip 47 bears suitable indicating indicia 49, which, when aligned with the window 45, is readily observable therethrough. The indicator strip 47 is so arranged that when the trip lever 24 is released and returned to the tripped position illustrated in FIG. 2, the indicator strip 47 is moved endwise generally tangentially of the pivotal axis of the trip lever 24 so that its outer end engages the curvilinear wall portion 48 and travels therealong toward and into alignment with the window 45. Since the outer end of the strip 47 is pushed into engagement with the wall 48, the indicator strip 47 flexes to the extent necessary to permit its outer end to align the window.
Generally, the lower end of the indicator strip 47 is provided with an enlarge portion or hub 50 which has a slit therein through which the outer end of the trip lever 24 extends so as to accommodate and support the inner end of the indicator strip 47 for limited sliding movement along the outer end portion of the trip lever 24 and for slight rocking movement of the strip 47 relative to the lever 24, so that the outer end 49 can readily adjust itself to the proper position for moving along the wall portion 48 and into alignment with the window 45 when the lever moves to tripped contact opening position.
When the trip lever is restored to untripped position, the indicator is returned and flexed back to its original unbent shape and so that its outer end 49 is out of alignment with the window.
The principal object of the invention is to provide in a circuit breaker a simple and improved trip indicator for indicating the tripped condition of the circuit breaker.
A more specific object is to provide an indicator which is connected to one of the moving parts of the circuit breaker mechanism so as to be moved thereby to "tripped" indicating position when the circuit breaker is tripped.
A more specific object is to provide an indicator which is connected to the trip lever of the trip mechanism of the circuit breaker and is moved thereby into trip indicating position by movement of the lever to tripped position.
A more specific object is to provide a trip indicator in the form of a simple strip of flexible self-restoring material which is detachably connected to the trip lever and is flexed and moved thereby into a trip indicating position upon tripping of the lever and is restored to its original condition upon movement of the trip lever to untripped or latched position.
Other objects and advantages will become apparent from the following description wherein reference is made to the drawing, in which:
FIG. 1 is a side elevation of a circuit breaker and trip mechanism embodying the principles of the present invention, the cover of the circuit breaker being omitted for clearness in illustration, and showing the circuit breaker in untripped and contact closing condition;
FIG. 2 is a view similar to FIG. 1 showing the circuit breaker in tripped contact opening condition;
FIG. 3 is a fragmentary front view of part of the trip mechanism, and is taken as indicated by the line 3-3 in FIG. 2; and
FIG. 4 is an enlarged fragmentary side elevation of the circuit breaker as shown in FIG. 1, part thereof being shown in section for clearness in illustration and showing particularly the latching mechanism.
As illustrated in the drawings, the circuit breaker trip mechanism and trip lever are such as fully disclosed in U.S. Letters Pat. No. 3,061,697 of A. J. Kralik et al., issued Oct. 30, 1962, and entitled "Thermal and Magnetic Trip Device." Accordingly, only those portions of the circuit breaker herein necessary to show the cooperation between the breaker parts and the indicator are described herein in detail.
In general, the breaker 1 comprises an insulating base 2, and a cover, not shown, which support the components of the circuit breaker. The circuit breaker may be held in a panelboard and connected to one side of a source of electrical energy by clips 3 and 3a. A terminal strip 4 is used to make a connection with the same side of the source in some instances. A load terminal strip 5 is connected to a connector 6 by which the circuit breaker can be connected to a load. The circuit breaker has a set of stationary contacts 10 and a set of movable contacts 11. The contacts 11 are mounted on the carrier 12 which is rockable about a pivot 13. An operating member 14 is also pivoted on the pivot 13 and is operatively coupled to an operating handle or manual operator 15 by means of a transverse pin 16 carried by the member 15 and engaging the sidewalls of a groove 17 in the operator 15.
A U-shaped connecting link 18 has legs with free end portions pivotally connected to the operating member 14 by a pivot 19, and has a bight portion 20 received within the slot 21 formed in the contact carrier 12. A helical operating spring 22 has one end secured to the bight portion 20 of the connecting link 18 and has its other end secured to an upstanding hooklike portion 23 of a trip lever 24. The trip lever 24 is pivotally supported on a transverse pivot pin 25 which is suitably supported within the base 2 of the circuit breaker.
The trip lever 24 is latched in untripped condition by a mechanism, to be described, and when so held the circuit breaker can be operated by the operator 15 to dispose the contacts 10 and 11 in the closed or ON position illustrated in FIG. 1, and in the open or OFF position, selectively.
The trip mechanism is electrically and mechanically connected to the load terminal strip 5 which is secured within the insulating base 2.
The trip mechanism comprises an elongated bimetallic strip 30 which is electrically and mechanically connected at its upper end portion to the upper end portion of the terminal strip 5. The strip 30 has a high expansion portion 30a and a low expansion portion 30b, and carries a yoke or core 31 of magnetic material attached to the lower end of the bimetallic strip 30. The magnetic yoke 31 extends upwardly generally parallel to the bimetallic strip 30 and an end portion of a flexible conductor 32 is interposed between portions of the magnetic yoke 31 and the bimetallic strip 30 and is electrically and mechanically secured to the strip 30, the other end portion of the conductor 32 being connected to the carrier 12 so that the strip 30 carries the current of the circuit associated with the circuit breaker. The strip 30 is so disposed relative to the yoke 31 that the current in the strip 30 causes flux to be created in the yoke 31 which is related in amount to the magnitude of the current in the circuit.
The central portion of the strip 30 is spaced from the back portion of the magnetic yoke 31 by a pair of protrusions 33 formed in the magnetic yoke. The magnetic yoke 31 is provided near its upper end with hooklike armature supports which pivotally support a magnetic armature 34 responsive to the flux created in the yoke 31.
The armature 34 comprises a bimetallic strip having a high expansion portion 34a. Facing and next adjacent the high expansion portion 30a of the strip 30 is a low expansion portion 34b facing inwardly of the circuit breaker. The bimetallic armature is indirectly heated by radiant, conductive, and convective transfer of heat produced by current flowing through the current responsive bimetallic strip 30. An offset lower end portion or finger 38 on the armature 34 extends through a cutout portion 39 in a spring retainer 40 formed by turning the lower end portion of the yoke 31 inwardly of the circuit breaker. A helical compression spring 41 is disposed between the spring retainer cup 40 and a pair of spaced shoulders 42 on the bimetallic armature 34. Normally the spring biases the armature clockwise about its pivotal connection with the yoke 31 so as to provide an air gap between the armature 34 and the pole faces of the yoke 31.
When the amount of flux in the core exceeds a predetermined value, magnetic attraction on the armature 34 overcomes the bias of the spring 41 and causes the armature to swing counterclockwise about its pivot supports. An upper end portion of an ambient temperature compensating bimetallic strip 43 is attached to an upper end portion of the bimetallic armature 34 and extends downwardly substantially parallel to the armature from its point of attachment to engage the releasable trip lever 34. The high expansion portion of the ambient bimetallic strip 43 is affixed adjacent to and faces the low expansion side 34b of the magnetic armature 34. The lower edge face 43a of the bimetallic strip serves as a latch for the trip lever 24 and normally engages an upwardly directed surface 24a at the outer end of the trip lever 24 to hold the trip lever 24 in untripped position.
The path of the current through the trip device is from the terminal strip 5, through the bimetallic strip 30 and flexible conductor 32 to the contact carrier 12, to the movable contact 11 and fixed contact 10, to the strip 4, and then to the spring jaw clips 3 or a flexible conductor, if desired.
Upon the occurrence of an overload in the circuit connected by the circuit breaker, the flow in the current responsive bimetallic strip 30 causes the strip to deflect in a counterclockwise direction about its point of attachment to the terminal strip 5. When the overload is moderate and of relatively short duration, the current responsive bimetal strip 30 flexes slightly, but due to the short duration of the overload the bimetallic armature 34 is not heated sufficiently by radiation, conduction or convection to flex and supplement the flexures of the current responsive bimetal strip 30 and the latching face 43a of the ambient temperature bimetal 43 is not retracted from engagement with the face 24a of the releasable latch lever 24. Upon occurrence of a sustained moderate overload heat produced as a result of the current flow through the bimetallic strip 30 indirectly heats the bimetallic armature 34 and causes it to flex thereby to move and offset the upper portion thereof in a counterclockwise direction about its pivotal connection. This causes the lower edge 43a of the ambient temperature bimetallic strip 43 to move away from the surface 24a to release the trip lever 24.
Upon occurrence of severe overload, the current responsive bimetal strip 30 is heated sufficiently to retract the latching face 43a of the ambient temperature bimetal strip 43 from engagement with the latching surface 24a of the trip lever 24 before heat transfer to the bimetal armature 34 is sufficient to cause flexure thereof to effect tripping in the manner described.
Upon the occurrence of a fault current, the magnetic bimetallic armature 34 is attracted to the pole faces of the magnetic yoke or core 31, thereby disengaging the latching face 43a of the ambient temperature bimetal 43 and the latching surface 24a of the trip lever 24 before the current responsive bimetal flexes in response to the fault.
Thus the trip device provided is one wherein release of the trip lever 24 due to an overload is a function of time as well as magnitude and wherein release due to a fault current is substantially instantaneous.
Upon release of the trip lever 24, the trip lever is rotated counterclockwise about the pin 25 by the spring 22 and carries the operating spring 22 across a line between the point of engagement of the link 18 in the slot 21 of the contact carrier 12 and the pivot 19 of the link 18 on the operating member 14, and thereby causing the spring 22 to open the contacts 10 and 11. Thus the latch lever 24 is swung from the untripped condition in FIG. 1 to the tripped condition in FIG. 2, wherein its outermost or latching end, with the face 24a, is swung toward the front wall of the casing or base 2.
In this connection, the lever 24 is used to operate an indicator for indicating the tripped condition of the circuit breaker. For this purpose the front wall of the circuit breaker base 2, toward which the released trip lever 24 swings, is provided with a window 45. Mounted on the outer end of the trip lever 24 is an indicator 46 which comprises a strip 47. The indicator strip 47 preferably is of fibrous, nonconducting, material which is relatively stiff, but flexible and self-restoring. It may, however, be of other suitable material. The strip 47 is connected at its inner end to the outer end of the trip lever 24 and, lengthwise, extends from its point of connection to the lever 24 toward the window 45. The wall of the base 2 adjacent the window 45 has a curvilinear wall portion 48 which is concave generally inwardly of the base 2 toward the outer end of the trip lever 24. The outer end of the indicator strip 47 bears suitable indicating indicia 49, which, when aligned with the window 45, is readily observable therethrough. The indicator strip 47 is so arranged that when the trip lever 24 is released and returned to the tripped position illustrated in FIG. 2, the indicator strip 47 is moved endwise generally tangentially of the pivotal axis of the trip lever 24 so that its outer end engages the curvilinear wall portion 48 and travels therealong toward and into alignment with the window 45. Since the outer end of the strip 47 is pushed into engagement with the wall 48, the indicator strip 47 flexes to the extent necessary to permit its outer end to align the window.
Generally, the lower end of the indicator strip 47 is provided with an enlarge portion or hub 50 which has a slit therein through which the outer end of the trip lever 24 extends so as to accommodate and support the inner end of the indicator strip 47 for limited sliding movement along the outer end portion of the trip lever 24 and for slight rocking movement of the strip 47 relative to the lever 24, so that the outer end 49 can readily adjust itself to the proper position for moving along the wall portion 48 and into alignment with the window 45 when the lever moves to tripped contact opening position.
When the trip lever is restored to untripped position, the indicator is returned and flexed back to its original unbent shape and so that its outer end 49 is out of alignment with the window.