US 3605052 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent Herbert M. Dimond West Hartford;
Keith W. Klein, Simsbury, both of, Conn. 4,942
Jan. 22, 1970 Sept. 14, 1971 General Electric Company Inventors Appl. No. Filed Patented Assignee AVOIDANCE OF SWITCHING DEVICE FALSE OFF HANDLE INDICATION 7 Claims, 6 Drawing Figs. 1
US. Cl. 335/166 Int. Cl. H0lh 3/20 Field olSeu-eh 335/166,
 References Cited UNITED STATES PATENTS 2,158,387 5/1939 Taylor 337/70 3,525,959 8/1970 Ellsworth et al. 335/166 Primary Examiner-Harold Broome AtwrneysRobert S. Smith, Robert T. Casey, D. M. Schiller,
Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Switching apparatus having an operating mechanism including a releasable trip member or cradle for automatically opening relatively movable contact means, a manually actuatable handle movable between ON, OFF, and RESET positions for manually closing and opening the contact means and for resetting the cradle in a latched position and means-preventing movement of the handle to the OFF or RESET positions when the contact means is in closed circuit position, to preclude a false OFF handle indication.
AVOIDANCE OF SWITCHING DEVICE FALSE OFF HANDLE INDICATION FIELD OF THE INVENTION This invention generally relates to electrical switching apparatus and particularly concerns electric circuit breakers having means for avoiding a false OFF handle indication.
BACKGROUND AND OBJECTS OF THE INVENTION In certain prior art switching apparatus and circuit breakers, release of a trip member from latched position takes place automatically upon occurrence of certain abnormal current conditions, typically an overcurrent condition, permitting an operating mechanism to move a movable contact to open circuit position. A manually actuatable handle is normally provided, not only to manually effect a switching movement upon moving the handle from ON to OFF positions, but also to reset the trip member in latched position, e.g., after automatic tripping of the circuit breaker.
If the movable contact were to be welded in closed circuit position, and the handle manually moved to the OFF position, the handle of known circuit breakers might remain in an OFF position when released, particularly when the handle is conventionally connected by a tension spring to an overcenter toggle linkage of the operating mechanism controlling movement of the movable contact.
Accordingly, a primary object of this invention is to provide an improved electrical switching apparatus of the general type described which will preclude the handle from remaining in OFF position upon being released when the contacts are in closed circuit position to eliminate any possibility of an operator being misled by the handle indication to believe that the circuit is open.
Another object of this invention is to provide an electrical switching apparatus having an improved safety feature precluding resetting of the operating mechanism trip member in a latched position when the contacts are in closed circuit position.
A further object of this invention is to provide an electrical switching apparatus including an improvement wherein the handle is automatically blocked from being moved to OFF position when the contacts are welded in closed circuit position.
Still another object of this invention is to provide an electrical switching apparatus of the type described particularly suited to avoid false OFF handle indication and which is quick and easy to manufacture and assemble and of rugged, compact construction for reliable operation over a long service life.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments and are indicative of the varims ways in which the principle of the invention is employed.
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:
FIG. 1 is a side elevational view, partly broken away and partly in section, showing a circuit breaker in corporating this invention;
FIG. 2 is a side elevational view, partly broken away and partly in section, showing the trip release mechanism of the circuit breaker of FIG. 1 in a TRIPPED condition with the contacts in closed circuit position;
FIG. 3 is an exploded isometric view, partly broken away, showing portions of the operating mechanism of this invention on an enlarged scale;
FIG. 4 is a view similar to FIG. 1 showing a circuit breaker incorporating another embodiment of this invention; showing the relationship of the parts in the ON position in solid lines;
FIG. 5 is a view similar to FIG. 4 and showing the relationship of the parts in the OFF position; and
FIG. 6 is a view similar to FIG. 3 showing portions of the operating mechanism of the circuit breaker of FIG. 4 on an enlarged scale.
DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings in detail, wherein like numerals identify like parts throughout the several figures, a preferred embodiment of this invention is shown in FIGS. I-3 which for illustrative purposes is shown incorporated in an electric circuit breaker although it is to be understood that this invention is adapted to be used in a variety of different electrical switching applications having requirements for selectively controlling an electrical switching operation by a manually actuated operating handle and wherein the handle additionally serves to indicate the condition of the circuit controlled by the switching apparatus The circuit breaker includes an insulating casing 10 having a base 12 and a cover 14. It is to be understood that a line ter minal, not shown, is suitably connected to a fixed contact I6 shown supported on a terminal strap 18. A relatively movable contact 20 is carried by a contact arm assembly 22 pivotable about a crossbar shaft 24 suitably mounted in the casing base 12. The contact arm assembly 22 is connected by a flexible conductor 26 to a terminal member, not shown, which passes through and energizes a current responsive automatic trip release mechanism or trip unit 28 and the terminal member is connected to a load terminal, not shown, fixed in the casing base 12 to complete the circuit across the breaker.
As shown in FIG. 1, the trip unit 28 includes a thermally responsive bimetal conductive strip 30 suited to be activated by an overload current of low value which heats the strip 30 causing it to deflect toward a trip bar 32 of a resettable trip mechanism 34. Upon sufficient deflection, a calibrating screw 36 carried on the strip 30 drives the trip bar 32 clockwise whereby a projection 38 formed on the trip bar 32 moves away from a trip latch 40 permitting it to move out of latched position with a releasable trip member of cradle 42 pivotally supported on a pivot pin 43 fixed to side frame members 45, 45 of the base 12.
A switch operator or operating mechanism 44 including toggle linkage 46 is provided to connect the cradle 42 to the contact arm assembly 22, and the toggle linkage 46 is connected at its knee pin 48 by spring means such as tension spring 50 to a handle lever 52 of a manually operable handle 54. As explained and described in US. Pat. No. 3,I55,803 of Keith W. Klein and David B. Powell granted Nov. 3, 1964, entitled Electric Circuit Breaker with Toggle Positioning Means and assigned to the assignee of this invention, the tension spring 50 acts through an upper toggle link 56 to impose a force on the cradle 42 tending to rotate it in a clockwise direction upon being released from latched position (FIG. 1).
Movement of the cradle 42 out of latched position causes the operating mechanism 44 to open the circuit contacts 16, 20 and move the handle 54 to TRIP position shown in phantom lines in FIG. I. The trip bar 32 is then held in its released position (FIG. 2) by cooperative engagement between the trip latch 40 and a raised boss 58 carried by the projection 38 of the trip bar 32.
The construction and operation of the trip release and trip mechanism 28 and 34 are fully shown and described in copending U.S. Pat. application Ser. No. 825,6l0 of Keith W. Klein entitled Bi-Metal Shunting Contacts With Weld-breaking Means" filed May 19, 1969 and assigned to the assignee of this invention, now US. Pat. No. 3,548,358 issued Dec. I5, I970. As fully explained in the referenced application, the releasable cradle 42 is reset in latched position by moving the handle 54 rearwardly toward RESET position causing a reset pin 60 of the operating mechanism 44 to move the cradle 42 in a counterclockwise direction about its pivot pin 43 until an arcuate front face 64 of the cradle 42 clears a crossbar portion 66 of the trip latch 40. This action permits the trip bar 32 to return to latched position under the biasing force of a spring, not shown, whereby the trip latch 40 slides off the boss 58 of the trip bar 32 and is again held in latched position by the trip bar projection 58 to once again relatch the cradle 42. With the cradle 42 in latched position, the trip mechanism 34 is conditioned for automatic release upon the next occurrence of an abnormal current condition after the breaker is reclosed upon movement of the handle 54 to its ON position causing the toggle linkage 46 to be straightened to move the movable contact 20 into closed circuit position with the fixed contact 16.
To avoid any possibility of a false OFF handle indication in the event the contacts 16, 20 welded or otherwise remained closed for any reason upon moving the handle 54 rearwardly toward OFF position, an interlock 70 is mounted in accordance with this invention within the casing base 12 for pivotal movement on a pivot shaft 72 secured to the side frame members 45, 45. The interlock 70 is biased in a clockwise direction as viewed in FIGS. 1-3 so as to be positioned in the path of movement of the cradle 42 to interfere with its being relatched or reset responsive to movement of the handle 54 to RESET position when the contact arm assembly 22 remains in closed circuit position.
More specifically, the interlock 70 comprises a blocking lever 74 having a pair of arms 76, 76 connected by a bottom web 78 adjacent the pivot shaft 72. The arms 76, 76 extend upwardly in spaced apart alignment for receiving the cradle 42 therebetween, and each arm 76, 76 has a swinging end suitably notched to provide a pair of contact shoulders 80, 80 for engaging opposite ends of a crosspin 82 secured to extend laterally through the cradle 42. A resilient leg 84 is integrally formed on the lever 74 to extend outwardly from the web 78 to be positioned in a rest position in adjacent overlying relation to the contact arm assembly 22 when in closed circuit position as shown in FIG. 2. A torsion spring 86 is suitably connected between one of the side frame members 45 and the blocking lever 74, and continuously urges the lever 74 in a clockwise angular direction as seen in FIGS. 1-3.
If the contact arm assembly 22 remains in closed circuit position upon release of the cradle 42 from latched position by movement of the trip bar 32 into releasing position (FIG. 2), the handle 54 would remain in ON position under the biasing force of the tension spring 50 while the toggle linkage 46 remains in a relatively straightened position as shown in FIGS. 1 and 2. By virtue of the above described structure, if an attempt was made to manually move the handle 54 to its OFF position, the cradle 42 could not be reset due to the blocking action of the interlock 70. Instead, the blocking lever 74 will assume an operative position shown in FIG. 2 under the force of its spring 86 wherein the contact shoulders 80, 80 of the lever 74 will positively engage the cradle 42 before it moves under the crossbar portion 66 of the trip latch 40 to be reset as in FIG. 1. Upon manual release of the handle 54 in the position where it is blocked between the ON and OFF positions by interlock 70, the tension spring 50 will automatically return the handle 54 to its ON position to effectively eliminate any possibility of a false OFF handle indication. The toggle linkage 46 in relatively straightened position restrains the line of action of the spring 50 from crossing the handle pivot pin 87 and continuously urges the handle 54 toward its ON position under such a closed circuit condition. However, when the contact arm assembly 22 pivots to move the movable contact 20 to open circuit position as shown in phantom lines in FIG. I, the upper surface 88 of the contact arm assembly 22 engages the free end of the leg 84 and transmits angular motion to the blocking lever 74 to rotate it counterclockwise into an inoperative position against the biasing force of its torsion spring 86. Movement of the handle 54 to RESET position then effectivelv resets the cradle 42 in its illustrated latched reset posi- In the embodiment of the invention illustrated in FIGS. 4-6, operation of the circuit breaker is generally similar to that described above in connection with the first embodiment. it will be noted that an armature )0 of a magnetizable shunting plate 92 is also shown continuously biased by a drive spring 94 toward its illustrated rest position against attractive forces of a field magnet 96 of an electromagnetic shunting trip device 98. The electromagnetic trip device is shown in FIG. 5 in closed shunt position with the trip bar in released position after occurrence of an overload condition of high value suili cient to activate the electromagnetic trip device W in accordance with well known techniques and to drive the trip bar 32 to release the cradle 42 in a manner similar to that described above in connection with the thermally responsive bimetal strip 30.
In the embodiment of FIGS. 4--6, movement of the handle lever 54 in OFF/RESET direction is automatically restrained unless the contact arm assembly 22 has moved toward its open circuit position shown in FIG. 5, regardless of whether the trip member has been released. More specifically, a blocking lever 100 is pivotally supported by a pin 102 on side frame members 45, 45 fixed to the casing base 12.. The lever 100 has an upright arm 104 suitably dimensioned and configured to provide a terminal finger 106 preventing movement of the handle 54 into its OFF position when the contact arm assembly 22 is in closed circuit position. The finger 106 is shown suitably offset to be positioned in the path of movement of the handle lever 52 for engagement with a shoulder 108 formed by a recess 110 in the lever 100. The blocking lever 100 is continuously urged toward its operative position blocking handle movement (FIG. 4) under the biasing force of a torsion spring 112 would about the pivot pin 102 and with opposite ends of the spring 112 secured to the blocking lever I00 and side frame member 45.
As in the previously described embodiment, the blocking lever 100 has an integral leg 114 projecting outwardly toward a rest position adjacent the contact arm assembly 22 in its closed circuit position. The torsion spring 112 continuously urges the blocking lever I00 toward interference engagement with the handle lever 52 to block complete manual movement of the handle 54 to the OFF position when the contacts 16, 20 remain closed whereby upon release the handle 54 is returned by the tension spring 50 to the ON handle position. Such construction still permits movement of the lever 100 to an inoperative position under the drive force of the contact arm assembly 22 upon opening of the contacts 16,20. In view of such construction when the contacts 16,20 are opened, the handle 54 is permitted to be moved to its RESET position shown in phantom lines in FIG. 5 for resetting the cradle 42. The blocking lever 100 is rotated into noninterfering relation to the recess 110 above the shoulder 108 of the handle lever 52 by the angular motion applied to the leg 114 of the blocking lever 100 by the contact opening movement of the pivoting contact arm assembly 22. This rotation occurs after tension spring 50 passes over center of the toggle linkage 46 during either automatic tripping or manual opening of the contacts 16,20.
In FIG. 4, the phantom lines depicting handle 54 show its maximum travel when contacts 16, 18 are closed such as by welding. The blocking terminal finger 106 of lever I00 engages the handle lever 52 at shoulder portion 108 (shown in phantom) to prevent further travel.
By virtue of the above disclosed embodiments, an electrical switching apparatus incorporating an interlock of this invention will provide a significant safety feature in a compactrugged construction which is not only quick and easy to manufacture but is also capable of providing long, reliable service.
As will be apparent to persons skilled in the art, various modifications adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of this invention.
1. Electrical switching apparatus comprising an enclosing a, a stationary contact supported in said casing,
b. a movable contact supported in said casing,
c. an operating mechanism in said casing for moving said movable contact and including a releasable cradle movable between a latched position and a released position,
d. said operating mechanism also including a handle movable between OFF and ON positions for manually operating said movable contact between open and closed circuit positions respectively while said cradle is in said latched position,
e connecting means between said handle and said cradle providing for movement of said cradle from said released to said latched position by movement of said handle in a direction from said ON toward said OFF position, and
f. blocking means positively preventing movement of said handle to move said cradle to said latched position while said movable contact is in said closed circuit position, and
g. means operated in response to movement of said movable contact from said closed to said open circuit position to defeat said blocking means to permit movement of said cradle to said latched position.
2. Electric switching apparatus as set forth in claim 1 wherein said blocking means comprises a blocking interlock member movable between a blocking and a nonblocking position, biasing means biasing said blocking means to said blocking position while said movable contact is in said closed circuit position, said operating mechanism including means operated in response to movement of said movable contact to said open circuit position for moving said blocking means to said nonblocking position despite said biasing means.
3. Electrical switching apparatus as set forth in claim 2 wherein said blocking member when in said blocking position is in the path of movement of said releasable cradle and prevents movement of said cradle to said relatched position.
4. Electrical switching apparatus as set forth in claim 2 wherein said blocking member when in said blocking position is in the path of movement of said handle member and prevents movement of said handle to said OFF position.
5. Electrical switching apparatus as set forth in claim 1 wherein said blocking member comprises a lever pivotally supported in said casing, said lever having an abutment portion for engaging and blocking a portion of said operating mechanism for preventing movement of said cradle to said relatched position, means biasing said lever to blocking position, and said lever having a second portion engageable by said movable contact means for moving said lever out of said blocking position against the bias of said biasing means.
6. Electrical switching apparatus as set forth in claim 1 wherein said blocking member comprises a lever pivotally supported in said casing, said lever having an abutment portion for engaging and blocking one of said cradle and handle members for preventing movement of said cradle and handle members for preventing movement of said cradle to said relatched position, means biasing said lever to blocking position, and said lever having a second portion engageable by said movable contact means for moving said lever out of said blocking position against the bias of said biasing means 7. Electrical switching apparatus as set forth in claim 1 wherein said operating mechanism includes an overcenter spring biasing said handle to said ON position when said handie is in said ON position and biasing said handle to said OFF position when said handle is in said OFF position, said blocking means, when operative preventing movement of said handle from said ON to said OFF position far enough to prevent said overcenter spring means from crossing the handle pivot point for insuring that said handle when released will be moved away from said OFF position by said overcenter spring.