US3849747A

US3849747A - Circuit breaker with handle indicating means

Info

Publication number: US3849747A
Application number: US00419744A
Authority: US
Inventors: S Mrenna; G Thomas
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1973-11-28
Filing date: 1973-11-28
Publication date: 1974-11-19
Anticipated expiration: 1991-11-19
Also published as: GB1452589A; CA972018A; DE2451915A1; CH587558A5; AU7538674A; ZA745867B; ES206534Y; PH12900A; BE822678A; ES206534U

Abstract

An improved circuit breaker comprises means operating, when the contacts are welded closed and the cradle is released, to block the trip member or cradle against movement to a reset or relatched position and to maintain the operating handle in the closed position to thereby provide a true external indication of the closed condition of the contacts. The blocking means on the cradle strikes the contact arm in an opening direction when the cradle is released and the contacts are welded whereby if the weld is not firm the striking action will break the weld and open the contacts.

Description

United States Patent [191 Mrenna et al.

CIRCUIT BREAKER WITH HANDLE INDICATING MEANS Inventors: Stephen A. Mrenna; Glenn R.

Thomas, both of Beaver, Pa.

Assigneez- Westinghouse Electric Co orgtion,

Pittsburgh, Pa.

Filed: Nov. 28, 1973 Appl. No.: 419,744

US. Cl. 335/166, ZOO/DIG. 42 Int. Cl. H01h 9/20 Field of Search 355/166; ZOO/DIG. 42;

References Cited UNITED STATES PATENTS Nov. 19, 1974 3,605,052 9/1971 Dimond et a1. 335/166 3,614,685 10/1971 Ellsworth et a1 335/166 Primary Examiner-Harold Broome Attorney, Agent, or FirmW. A. Elchik [5 7] ABSTRACT An improved circuit breaker comprises means operating, when the contacts are welded closed and the cradle is released, to block the trip member or cradle against movement to a reset or relatched position and to maintain the operating handle in the closed position to thereby provide a trueexternal indication of the closed condition of the contacts. The blocking means on the cradle strikes the contact arm in an opening direction when the cradle is released and the contacts are welded whereby if the weld is not firm the striking action will break the weld and open the contacts.

3 Claims, 5 Drawing Figures PAH-INTEL NOV 1 9l974 sum 1 or 3 1 FIGS PAIENIE NOV 1 91974 sum 2 or 5 FIG.4

PATENIE auv 191974 sum 30F 5:

1 CIRCUIT BREAKER WITH HANDLE INDICATING MEANS CROSS-REFERENCE TO RELATED APPLICATION Certain features of the circuit breaker herein disclosed are disclosed in the copending patent application of Francis L. Gelzheiser Ser. No. 419,749, filed concurrently herewith.

BACKGROUND OF THE INVENTION 1. Field of the Invention:

Circuit breakers of the type comprising latch and trip means automatically releasable to effect tripping operations and manually resettable following tripping operations.

2. Description of the Prior Art:

In the US. Pat. to Bullis, .lr. No. 3,200,217 there is disclosed a circuit breaker having an operating mechanism that is generally similar in operation to the mechanism of the circuit breaker of the subject invention. The circuit breaker of this invention is an improvement over that disclosed in the Bullis, Jr. patent in that the subject breaker comprises means operating, when the contacts are welded closed and the trip member is released, to block the cradle against movement to a resetting position and to maintain the operating handle in the closed position to provide a true indication of the closed condition of the contacts.

The idea of preventing a reset of the trip member or cradle when the contacts of a circuit breaker are welded closed and of maintaining the operating handle in the closed position when the contacts are welded closed is disclosed in the US. Pat. to Ellsworth et al, No. 3,525,959 and to Ellsworth No. 3,614,685. The operating and trip mechanisms in the above-mentioned Ellsworth et al and Ellsworth patents, however, are substantially different from the operating and trip mechanism of the circuit breaker of the subject invention.

SUMMARY OF THE INVENTION A circuit breaker is provided comprising an insulating housing and a circuit-breaker mechanism supported in the housing. The mechanism comprises a stationary contact and a movable contact. The movable contact is supported on a contact arm. A releasable cradle is pivotally supported in proximity to one end thereof and latched, at the other end thereof, on trip means. An operating spring is supported at one end thereof on the contact arm and at the other end thereof on the cradle. An operating member is operatively connected to the contact arm and extends through an opening in the front of the housing to permit manual operation of the breaker. With the cradle in the latched position, the operating member is manually operable between open and closed positions to operate the spring and contact arm to thereby move the movable contact arm between open and closed positions. Upon the occurrence of overload current conditions above a predetermined value the trip means releases the cradle whereupon the spring moves the cradle to a tripped position and the contact arm to the open position. Following movement of the cradle to the tripped position, the operating member is manually movable to the open position during which movement the operating member engages the cradle to move the cradle back to the latched position. Blocking means on the contact arm engages blocking means on the cradle to prevent movement of the cradle to the latched position when the contacts are welded closed and the cradle has been moved toward the tripped position. Following an attempt to reset the cradle, when the contacts are welded closed, the spring and mechanism will move the operating member back to the closed position upon release of the operating member by an operator, thereby providing a visual indication that the contacts are in the closed position. The blocking means on the cradle is bent-over tab part that also serves to strike the contact arm in an opening direction when the cradle is released and the contacts are welded whereby if the weld is not a firm weld the striking action will break the weld and permit opening movement of the contact arm.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a circuit breaker embodying principles of this invention. The circuit breaker is shown in the closed position;

FIG. 2 is a view similar to FIG. I with the breaker shown in the off or open position; 1

FIG. 3 is a view similar to FIG. 1 with the breaker being shown in the tripped open position;

FIG. 4 is a view similar to FIG. 1 with the breaker being shown in the tripped position when the contacts have been welded closed; and,

FIG. 5 is a partial view similar to FIG. 1 illustrating the position of parts when the breaker has tripped with the contacts welded closed and an attempt is made to reset the cradle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is shown a circuit breaker 9 comprising an insulating housing that comprises a molded insulating side compartment part I] and a molded insulating side cover part 13 (FIG. 5) secured together by means of four rivets 15 (FIG. 1). A circuit-breaker mechanism, indicated generally at 17, is supported in the housing ll, 13. The mechanism 17 comprises a stationary supporting frame 19 fixedly supported in the housing on the housing part 11. The mechanism 17 also comprises a stationary contact 21, a movable contact 23, and trip means indicated generally at 25.

The stationary contact 21 is welded or otherwise fixedly secured to a line tenninal 27 that extends out through an opening in the bottom of the housing ll, 13. The movable contact 23 is fixedly secured to one 7 end of a contact arm 29. The contact arm 29, at the upper end thereof, is provided with a depression 31 therein. A molded insulating part 33 of an insulating operating member 35 engages the contact arm 29 in the depression 31 to provide an operative driving connection between the operating handle 35 and the contact arm 29. The operating member 35 is molded with a pair of pin parts 37 at the opposite sides thereof which fit into bearing openings in the housing parts 11 and 13 to support the operating member for pivotal movement on the housing ll, 13. The operating member 35 comprises a handle part that extends through an opening at the top of the housing 11, 13, to enable manual operation of the circuit breaker. A cradle 41 (FIGS. 1-3) is supported at one end thereof for pivotal The trip means comprises an elongated bimetal member 49 secured, in proximity to its upper end, to a bent-over tab part 51 of the frame 19. A flexible conductor 53 is connected at one end thereof to the upper end of the bimetal 49 and at the other end thereof to a conductor 55 that extends through an opening 57 in the housing 11, 13 and is part of a solderless terminal connector 59 that is externally accessible and supported on the housing 11, 13 in a well-known manner. Another flexible conductor 61 is secured at one end thereof to the lower end of the bimetal 49 and at the other end thereof to the contact arm 29 to electrically connect the contact arm 29 with the bimetal 49.

The circuit through the circuit breaker 9 extends from the line terminal 27, through the stationary contact 21, the movable contact 23, the contact arm 29, the flexible conductor 61, the bimetal 49, the flexible conductor 53, the conductor 55, to a conducting line (not shown) that would be connected to the conductor 55 by means of the solderless terminal connector 59 at an installation.

The circuit breaker 9 may be manually operated to open and close the contacts by operation of the insulating operating handle member 35. Movement of the operating member clockwise from the closed or on position (FIG. 1) to the open or off position (FIG. 2) carries the upper 'end of the contact arm 29 to the left of the line of action of the spring 43 whereupon the spring 43 acts to move the contact arm 29 with a snap action to the open position (FIG. 2). Movement of the operating member 35 in a counterclockwise direction back to the closed position moves the upper end of the movable contact arm 29 to the right of the line of action of the spring 43 whereupon the spring acts to move the contact 29 to the closed position (FIG. 1) with a snap action.

The trip device 25 comprises the bimetal 49, a magnetic yoke 63 and a magnetic armature 65. The yoke 63 is a generally U-shaped member secured to the bimetal 49 at the bight portion of the yoke 63 with the opposite legs thereof facing the armature 65. The magnetic armature 65 is secured to a supporting spring 67 that is secured, at its lower end, to the bimetal 49 whereby the armature 65 is supported on the bimetal 49 by means of the spring 67. The armature 65 has a window opening 71 therein. The one end of the cradle 41 is disposed in the window opening 71 and engages the latch surface 73 of the armature 65 in the latched position shown in FIGS. 1 and 2.

Upon the occurrence of an overload current above a first predetermined value, the bimetal 49 becomes heated and deflects to the right as seen in FIG. 1 to effect a time delayed thermal tripping operation. The armature 65, which is supported on the bimetal 49 by means of the spring 67, is carried to the right with the bimetal to release the cradle 41. When the cradle 41 is released, the spring 43 acts to rotate the cradle clockwise onthe post 42 about an axis 77 until this motion is arrested by the engagement of the cradle 41 with a molded housing part 79 of the housing 11, 13. During this movement, the spring 43 moves the contact arm 29 to the open position and the operating member 35 to an intermediate position intermediate the on" and off positions to provide a visual indication that the circuit breaker has tripped open. The tripped position of the parts is shown in FIG. 3.

Before the contacts can be closed following an automatic tripping operation it is necessary to reset and relatch the mechanism. This is accomplished by moving the operating member 35 clockwise from the intermediate position to a position slightly beyond the full open or of position. During this movement, due to the engagement of a downwardly extending portion 79 of the operating member 35 with the bent-over extension 47 of the cradle 41 (FIG. 3), the cradle 41 is moved counterclockwise about the axis 77 until the end of the cradle 41 is again latched in the window opening 7-] of the armature on the latch surface 73 (FIG. 2). Following a resetting operation the circuit breaker can be manually operated in the same manner as was hereinbefore described.

The circuit breaker is magnetically tripped automatically and instantaneously in response to overload currents above a second predetermined value higher than the first predetermined value. Upon the flow of the overload current through the bimetal 49, magnetic flux, which is induced around the bimetal, takes the path of least reluctance through the magnetic yoke 63, across an air gap and through the armature 65. When an overload current above the second predetermined value occurs, the pull of the magnetic flux is of such strength that the armature 65 is attracted to the magnetic yoke 63 whereupon the spring 67 flexes pennitting the armature to move to the right to release the cradle 41 whereupon the circuit breaker is tripped open in the same manner as was hereinbefore described with regard to the thermal tripping operation. Following a magnetic tripping operation the circuit breaker is reset and relatched in the same manner as was hereinbefore described.

The circuit breaker 9 comprises means for maintaining the operating member 35 in the onT or closed position when the cradle 41 is released with the

contacts

21, 23 welded in the closed position, and blocking means for preventing a resetting operation of the cradle 41 whereby the external handle of the operating member 35 will provide a true indication that the contacts I 21, 23 are closed.

As can be understood with reference to FIG. 4, when the

contacts

21, 23 are welded closed and an overload occurs, the trip means 25 will release the cradle 41 and the spring 43 will move the cradle 41 clockwise about the axis 77 toward the tripped position during which movement a bent-over tab 81 on the cradle 41 strikes the contact arm 29 in opening direction whereby if the weld between the

contacts

21, 23 is not a firm weld this striking action will break the weld and the parts will move to the tripped open position seen in FIG. 3. As can be understood with reference to FIG. 4, the cradle 41 is a flat sheet-metal member and the tab 81 is bent over to protrude in the direction out of the paper as seen in FIG. 4 so that the tab 81 is disposed to engage the sheet-metal type contact arm 29 to strike the contact arm 29 in an opening direction. As can be seen in FIG. 4, when the

contacts

21, 23 are welded closed and the tab 81 does not break the weld, movement of the cradle 41 is arrested in the position shown inFIG.

4. In this position, the geometry of the parts and the force of the tension spring 43 are such as to maintain the operating member 35 in the on or closed position toprovide a true external visual indication that the contacts are closed. As can be understood with reference to FIG. 5, when the

contacts

21, 23 are welded and an attempt is made to reset the cradle 41, the operating member 35 is manually pivoted clockwise toward the off position during which movement the contact arm 29 is moved to move a blocking surface 85 into engagement with the tab 81 to block further resetting movement of the operating member 35, contact arm 29 and cradle 41 with the parts being blocked in the position seen in FIG. 5 so that if the weld between the

contacts

21, 23 is not broken by this action the operating member 35 cannot be moved further toward the resetting position and the movement of parts will stop in the position seen in FIG. 5 without movement of the cradle 41 to the reset or relatched position. Upon release of the operating member 35 following an attempt to reset the cradle 41 when the

contacts

21, 23 are welded closed the spring 43 and mechanism will move the parts back to the position seen in FIG. 4 with the operating member 35 beng moved back to the on or closed position to thereby provide a visual indication of the closed condition of the contacts. Thus, an operator cannot reset the breaker and the operating member 35, in the closed position, provides an external true indication that the contacts are in the closed position.

We claim:

1. A circuit comprising an insulating housing having an opening in the front thereof, a circuit-breaker mechanism supported in said housing, said mechanism comprising a stationary contact, a movable contact, a contact arm supporting said movable contact, trip means, a releasable cradle, means pivotally supporting said cradle in proximity to one end thereof, said cradle at the other end thereof being latched on said trip means, an operating spring supported at one end thereof on said contact arm and at the other end thereof on said cradle, an operating member operatively connected to said contact arm and extending through said opening to permit manual'operation of said circuit breaker, with said cradle in the latched position said operating member being manually movable between open and closed positions to operate said spring and said contact arm to thereby move said contact arm between open and closed positions, upon the occurrence of an overload current above a predetermined value said trip means releasing said cradle and said spring moving said cradle to a tripped position and said contact arm to the open position, following movement of said cradle to said tripped position said operating member being manually movable to the open position during which movement said operating member engages said cradle to move said cradle back to the latched position, blocking means on said contact arm engaging blocking means on said cradle to prevent movement of said cradle to the latched position when said contacts are welded closed and said cradle has been moved toward the tripped position, and said blocking means on said cradle striking said contact arm in an opening direction when said cradle is released and said contacts are welded closed whereby if the weld of said contacts is not a firm weld the striking action can break the weld to permit movement of said contact arm to the open position.

2. A circuit breaker according to claim 1, said mechanism maintaining said operating member in the closed position when said contacts are welded closed and said cradle has been moved toward the tripped position, said mechanism returning said operating member to the closed position upon release by an operator when an attempt is made to reset said cradle with said contacts welded closed to thereby provide a true indication of the closed condition of said contacts.

3. A circuit breaker according to claim 2, said cradle being a sheet-metal type member, and said blocking means on said cradle being a bent-over tab bent over to a position where said blocking means on said cradle will strike said contact arm in anopening direction when said cradle is released and said contacts are welded closed.

Claims

1. A circuit comprising an Insulating housing having an opening in the front thereof, a circuit-breaker mechanism supported in said housing, said mechanism comprising a stationary contact, a movable contact, a contact arm supporting said movable contact, trip means, a releasable cradle, means pivotally supporting said cradle in proximity to one end thereof, said cradle at the other end thereof being latched on said trip means, an operating spring supported at one end thereof on said contact arm and at the other end thereof on said cradle, an operating member operatively connected to said contact arm and extending through said opening to permit manual operation of said circuit breaker, with said cradle in the latched position said operating member being manually movable between open and closed positions to operate said spring and said contact arm to thereby move said contact arm between open and closed positions, upon the occurrence of an overload current above a predetermined value said trip means releasing said cradle and said spring moving said cradle to a tripped position and said contact arm to the open position, following movement of said cradle to said tripped position said operating member being manually movable to the open position during which movement said operating member engages said cradle to move said cradle back to the latched position, blocking means on said contact arm engaging blocking means on said cradle to prevent movement of said cradle to the latched position when said contacts are welded closed and said cradle has been moved toward the tripped position, and said blocking means on said cradle striking said contact arm in an opening direction when said cradle is released and said contacts are welded closed whereby if the weld of said contacts is not a firm weld the striking action can break the weld to permit movement of said contact arm to the open position.

3. A circuit breaker according to claim 2, said cradle being a sheet-metal type member, and said blocking means on said cradle being a bent-over tab bent over to a position where said blocking means on said cradle will strike said contact arm in an opening direction when said cradle is released and said contacts are welded closed.