US3605051A

US3605051A - Avoidance of switching device false off handle indication

Info

Publication number: US3605051A
Application number: US4835A
Authority: US
Inventors: Robert T Casey; Keith W Klein
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-01-22
Filing date: 1970-01-22
Publication date: 1971-09-14
Anticipated expiration: 1988-09-14
Also published as: CA925133A

Abstract

Auxiliary trip device usable with an electrical switching apparatus having a movable contact arm, an operating mechanism including a releasable cradle for moving the contact arm between open and closed circuit positions, and a manually actuatable handle operably connected to the operating mechanism and automatically movable to a trip position upon release of the cradle. The auxiliary trip device is movable responsive to movement of the handle toward OFF position for tripping the cradle when the contact arm is in closed circuit position for avoiding a false OFF handle indication.

Description

I United States Patent 1 3,605,051

[72] inventors RobertT.Casey [5 Refel'ellcesciled s6u1hin m; f C UNITED STATES PATENTS A IN fgg 2,158,387 5/1939 Taylor 337/70 5; lg 15221970 3,171,927 3/1965 Kleinetal 335/43 Patented sepi. ml 3,525,959 8/1970 Ellsworthetalui 335/166 [73] Assignee General Electric Company Primary Examiner-Harold Broome [54] AVOIDANCE 0F SWITCHING DEVICE FALSE OFF HANDLE INDICATION 4 Claims, 4 Drawing Figs.

[52] US. Cl 335/166 [5|] Int. Cl IIOlh 3/20 Field ofSearch 335/166,

Attorneys-Robert S. Smith, Robert T Casey, D. M. Schiller,

Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Auxiliary trip device usable with an electrical switching apparatus having a movable contact am, an operating mechanism including a releasable cradle for moving the contact arm between open and closed circuit positions, and a manually actuatable handle operably connected to the operating mechanism and automatically movable to a trip position upon release of the cradle. The auxiliary trip device is movable responsive to movement of the handle toward OFF position for tripping the cradle when the contact arm is in closed circuit position for avoiding a false OFF handle indication.

AVOIDANCE OF SWITCHING DEVICE FALSE OFF HANDLE INDICATION FIELD OF THE INVENTION This invention relates to electrical switching apparatus and particularly to circuit breakers of a type incorporating means for avoiding a false OFF handle indication of the condition of the circuit breaker.

BACKGROUND OF THE INVENTION Heretofore movable contact arms for switching apparatus such as circuit breakers and the like have been commonly connected to an operating handle through spring-driven overcenter toggle linkage whereby it is possible to manually move the handle between N and OFF positions even though the movable contact remains in a closed circuit position due, e.g., to contact welding. When the handle is moved to OFF position under these conditions and returns toward ON position upon release of the handle, no problem is encountered even though the contacts are closed. However, were the handle to remain in its OFF position upon being released, the resulting handle indication may mislead an operator to believe the contacts are open when, in fact, they are closed.

Copending application Ser. No. 4942, filed Jan. 22, 1970 by H. M. Dimond and K. W. Klein and assigned to the same assignee as the present invention, discloses one solution to this problem, by which relatching or resetting of the circuit breaker mechanism is positively prevented if and when the movable contact is stuck in its closed-circuit position.

OBJECTS OF THE INVENTION Accordingly, a primary object of this invention is to provide a new and improved electrical switching apparatus particularly suited to avoid a false OFF handle indication when the movable contact arm is in closed circuit position.

Another object of this invention is to provide an improved auxiliary trip device which when utilized in circuit breakers and similar electrical switching apparatus will effect a mechanical trip of an operating mechanism when the handle is manually moved to OFF position with the contacts closed, causing the handle to be driven from OFF position upon being released.

A further object of this invention is to provide an improved auxiliary trip device of the above-described type which will positively preclude resetting the operating mechanism by handle movement while the contacts remain closed.

Still another object of this invention is to provide such an auxiliary trip device which can be incorporated in both new and existing electrical switching apparatus.

A still further object of this invention is to provide an improved auxiliary trip device usable in electrical switching apparatus which not only is of compact, simplified construction but is readily manufactured and assembled to provide reliable operation over a long service life.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

SUMMARY OF THE INVENTION In accordance with this invention, the above and related objects are attained by the provision of an electrical switching apparatus having a new and improved auxiliary trip device movable responsive to actuation of a manually operable handle to release a trip member or cradle from latched position to effect mechanical tripping of the switching apparatus whenever the handle is moved to an OFF position without simultaneous movement of a movable contact arm to open circuit position.

A better understanding of the objects, advantages, features, properties and relationships of this invention will be obtained from the following detailed description and accompanying drawing which set forth an illustrative embodiment and are indicative of the way in which the principle of this invention is employed.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a side elevational view, partly broken away and partly in section, showing a circuit breaker incorporating this invention and wherein a movable contact arm is in closed circuitposition with a handle shown in full lines in ON position;

FIG. 2 is a fragmentary view similar to FIG. 1 showing operative parts of the circuit breaker wherein the contact arm is in open circuit position with the handle shown in full lines in OFF position;

FIG. 3 is a view similar to FIG. 2 showing a condition wherein the contact arm remains in closed circuit position upon moving the handle toward OFF position; and

FIG. 4 is a fragmentary isometric view on an enlarged scale showing a trip latch of the circuit breaker in relation to an auxiliary trip device of this invention.

Description Of Preferred Embodiment Referring to the drawing in detail, for illustrative purposes, a circuit breaker is shown incorporating this invention, 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. A fixed contact 16 is supported on a terminal strap 18 secured in the casing base 12 and is associated with a line tenninal (not shown) at one end of the base 12. A movable contact 20 is carried on a pivotable contact arm assembly 22 connected by a flexible conductor 24 leading to a load terminal (not shown) on an opposite end of the base 12 to complete the circuit across the breaker.

As fully described in copending US. Pat. application Ser. No. 794,289 entitled Electric Circuit Breaker" of George E. Gauthier and Keith W. Klein, filed Jan. 27, 1969, now US. Pat. No. 3,564,l84 issued Feb. 16, 1971 and assigned to the assignee of this invention, the contact arm assembly 22 includes a contact operator 26 firmly mounted on a crossbar shaft 28, supported for pivotal movement in the casing base 12, and a composite contact carrier or arm 30 mounted on the contact operator 26 for limited pivotal movement by an interconnecting pivot pin 32. Rotation of the contact arm 30 in a counterclockwise direction as viewed in FIG. I, e.g., is resisted by a wire spring 34 secured in the operator 26 and held by the pivot pin 32 in a preloaded condition to continuously urge the contact arm 30 toward engagement with the fixed contact 16. Any clockwise rotational movement of the contact arm assembly 22 beyond that necessary for engagement between the

contacts

16, 20 will additionally load the spring 34 and ensure full contact pressure between the contact interfaces in the closed circuit position.

The contact arm 30 is operated between open and closed circuit positions by means of an operating mechanism 36 supported between a pair of fixed side frame members (only one shown at 38). The operating mechanism 36 includes a releasable trip member or cradle 40 pivotally supported by a pin 42 fixed on the side frames 38.

Operation of a circuit breaker of the general type shown in the drawing is fully explained in US. Pat. No. 3,l55,803 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. As described in the referenced patent, the cradle 40 is held in a latched position by a cooperating current responsive trip latch 44 adapted to release the cradle 40 automatically upon occurrence of a current of predetermined value within the circuit,

typically when certain abnormal or overcurrent conditions occur, which causes a spring-driven overcenter toggle linkage 46 of the operating mechanism 36 to collapse and to drive the movable contact arm 30 with a snap action into an open circuit position shown in FIG. 2. The cradle 40 is connected to the contact arm 30 through the toggle linkage 46 by a pivot pin connection at 48 to a pair of upper toggle links (only one shown at 52) pivotally connected to the contact arm 30 by the pin 32. The

links

50, 52 are pivotally connected by a knee pin 54.

To selectively move the contact arm 30 between openand closed circuit positions as well as for manually resetting or relatching the releasable cradle 40, the

toggle links

50, 52 are adapted to operate between collapsed and straightened conditions by a manually actuatable handle 56. The handle 56 protrudes through the cover 14 and is shown having a handle support or lever 58 mounted for oscillatory pivotal movement about a pivot pin 60 fixed to the side frame members 38. Tension spring means such as the driving spring 62 is connected between the handle lever 58 and the knee pin 54 of the toggle linkage 46 which not only serves to drive the linkage 46 between collapsed and straightened conditions as described in the aforementioned patent, but also applies a continuous upward biasing force on the knee pin 54 when the contact arm 30 is closed (FIGS. 1 and 3) which tends to rotate the cradle 40 clockwise about its pivot pin 42. Moreover, it will be seen that the preloaded wire spring 34 of the contact arm assembly 22 in closed circuit position also exerts a biasing force through the toggle linkage 46 tending to drive a latching nose 64 of the cradle 40 upwardly about its pivot pin 42,

Accordingly, upon occurrence of an overcurrent condition with the

contacts

16, 20 closed, the current responsive latch 44 is moved to automatically release the cradle 40 causing the toggle linkage 46 to collapse to open the

contacts

16,20, and automatically snap the handle 56 into its TRIP position shown in FIG. 1 intermediate its ON and OFF positions. Thereafter, if it is desired to relatch the cradle 40, the handle 56 is moved through its OFF position to RESET position (FIG. 2) whereby pin 66 carried by the handle lever 58 will engage the cradle 40 and reset it in latched engagement with a lug 68 of the trip latch 44. Once the line of action of the tension spring 62 crosses the handle pivot pin 60, the handle 56 will normally remain in its OFF position upon release under the biasing force of the tension spring 62 which will then be overcenter to the left of the handle pivot pin 60 as best seen in FIG. 2.

Should the movable contact 20 remain closed for any reason, it will be seen that upon manually moving the handle 56 to OFF position, the handle 56 upon release might then falsely indicate OFF, possibly causing an operator to erroneously assume that the circuit has been opened. To avoid such false OFF handle indication a significantly improved safety feature is provided in accordance with this invention by an auxiliary trip device 70 incorporated in the breaker to positively force a mechanical trip" when the handle 56 is moved manually to its OFF position without a simultaneous opening movement of the contact arm 30.

In the specifically illustrated embodiment of this invention, the auxiliary trip device 70 is shown comprising a generally L- shaped lever 72 carried on the handle lever 58 and supported thereon by a pivot pin 74 for angular movement. The L- shaped lever 72 has an arm 76 extending outwardly from the handle lever 58 and continuously biased counterclockwise by a suitable torsion spring 78 toward engagement with the latch 44 when the handle 56 is moved toward OFF position. By virtue of such construction, when the contact arm 30 remains in closed circuit position with the toggle linkage 46 in relatively straightened condition, the movement of the handle 56 toward OFF position will positively force a mechanical trip of the releasable cradle 40. The biasing forces exerted by the

springs

34 and 62 cause the cradle nose 64 to rotate upwardly past the latching lug 68 into a released position (FIG. 3). This construction positively ensures separation of the cradle 40 and its latch 44 to preclude any attempt to reset the operating mechanism 36 while the

contacts

16, 20 are closed. Moreover,

as best seen in FIG, 3, the line of action of the tension spring 62 does not cross the handle pivot pin 60, thereby continuously ensuring that with the toggle linkage 46 in straightened position, the handle 56 will always be driven away from OFF position, upon release and into ON position. After the

contacts

16, 20 have been opened and the toggle linkage 46 collapsed, the cradle 40 can once again be relatched by moving the handle 56 to its RESET position (FIG. 2).

To provide for normal operation without forcing a trip" each time handle 56 is moved from ON to OFF positions, a depending arm 80 is integrally formed on the lever 72 to extend generally downwardly from its pivot pin 74. The arm 80 is provided with a finger 82 suitably offset to lie in the path of movement of the upper toggle link 50. Upon collapse, the upper toggle link 50 engages the finger 82 to rotate the lever 72 against the force of its torsion spring 78 and drive the lever 72 into an inoperative position (FIG. 2) ensuring that its arm 76 bypasses or clears the latch 44, rendering the auxiliary trip device 70 ineffective to prevent unintended release of the cradle 40 under normal opening of the

circuit breaker contacts

16, 20.

A circuit breaker incorporating an auxiliary trip device 70 constructed in accordance with this invention will not only provide a significant safety feature to avoid any false OFF handle indication, but will also permit normal manual opening of the

circuit breaker contacts

16, 20 without disturbing latched engagement of the cradle 40. Moreover, the disclosed auxiliary trip device 70 is of a simplified construction well-suited to provide dependable operation over a long service life.

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.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Electrical switching apparatus comprising:

a. a stationary contact,

b. a movable contact,

40 c. an operating mechanism for moving the movable contact and including a releasable cradle movable into a latched position, and

. a handle movable between OFF and ON positions for manually operating the operating mechanism to move the movable contact between open and closed circuit positions respectively while the cradle is in latched position,

e. an auxiliary trip device movable responsive to handle movement from ON position toward OFF position while the cradle is in latched position and the movable contact is in the closed circuit position to cause release of the cradle from latched position,

. said operating mechanism including disabling means engaging said auxiliary trip device when said operating mechanism moves said movable contact to said open circuit position rendering said auxiliary trip device ineffective to cause release of said cradle from said latched position.

2. Electrical switching apparatus as set forth in claim I wherein said operating mechanism includes an overcenter tension spring which is normally operative through said operating mechanism to bias said movable contact toward said open circuit position when said handle is in said OFF position and to bias said movable contact toward said closed circuit position when said handle is in said ON position.

3. Electrical apparatus as set forth in claim 2 wherein said operating mechanism also includes a pair of toggle links movable between collapsed and straightened conditions corresponding to said open and closed circuit positions of said movable contact, said disabling means comprising a part of said toggle linkage.

4. Electrical apparatus as set forth in claim 2 wherein release of said cradle prevents said tension spring from crossing the pivotal axis of said handle during movement of said handle toward OFF position even if said movable contact remains in its closed circuit position.

Claims

1. Electrical switching apparatus comprising: a. a stationary contact, b. a movable contact, c. an operating mechanism for moving the movable contact and including a releasable cradle movable into a latched position, and d. a handle movable between OFF and ON positions for manually operating the operating mechanism to move the movable contact between open and closed circuit positions respectively while the cradle is in latched position, e. an auxiliary trip device movable responsive to handle movement from ON position toward OFF position while the cradle is in latched position and the movable contact is in the closed circuit position to cause releaSe of the cradle from latched position, f. said operating mechanism including disabling means engaging said auxiliary trip device when said operating mechanism moves said movable contact to said open circuit position rendering said auxiliary trip device ineffective to cause release of said cradle from said latched position.

2. Electrical switching apparatus as set forth in claim 1 wherein said operating mechanism includes an overcenter tension spring which is normally operative through said operating mechanism to bias said movable contact toward said open circuit position when said handle is in said OFF position and to bias said movable contact toward said closed circuit position when said handle is in said ON position.