US3158720A

US3158720A - Contact assembly having hinge means utilizing electrodynamic forces of current flow therethrough

Info

Publication number: US3158720A
Application number: US89977A
Authority: US
Inventors: Wiktor Dominik
Original assignee: Federal Pacific Electric Co
Current assignee: Federal Pacific Electric Co
Priority date: 1961-02-17
Filing date: 1961-02-17
Publication date: 1964-11-24
Anticipated expiration: 1981-11-24

Description

Nov. 24, 1964 WIKTOR 3,158,720

CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZING ELECTRODYNAMIC FORCES OF CURRENT FLOW THERETHROUGH 5 Sheets-Sheet 1 Filed Feb. 17. 1961 NVENTOR DOM/N/K W/KTOP.

Nov. 24, 1964 D. WIKTOR CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZIN ELECTRODYNAMIC FORCES OF CURRENT mow THERETHROUGH 5 Sheets-sheet 2 Filed Feb. 17. 1961 JNVENTOR. DOM/MK W//( 702 A TTORNEY Nov. 24, 1964 CONTACT ASSEMBLY l-IAVING HI D WIKTOR NGE MEANS UTILIZING ELECTRODYNAMIC FORCES OF CURRENT Filed Feb. 17, 1961 FLOW THERETHROUGH 3 Sheets-Sheet 3 INVENTOR. DOM/N/K W/KTOR Adm ATTORNEY United States Patent 3,158,720 CONTACT ASSEMBLY HAVING HINGE MEANS UTILIZING ELECTRODYNAMIC FORCES OF CURRENT FLOW THERETHROUGH Dominik Wiktor, Irvington, N.J., assignor to Federal Pacific Electric Company, a corporation of Delaware Filed Feb. 17, 1961, Ser. No. 89,977 6 Claims. (Cl. 200-146) This invention relates generally to power circuit breakers and more particularly to the moving contact assembly for such apparatus.

Each pole of an illustrative multipole circuit breaker that is described in detail below includes a moving contact arm that carries main and arcing contacts into and out of substantially normal contact engagement with companion contacts. The arcing contacts are designed to part from companion stationary arcing contacts only after the main moving contact arm has separated from its companion contact. Similarly, the arcing contacts engage their companion contacts before the main contacts touch each other during the closing operation.

An object of the present invention resides in the provision of an improved arrangement for providing a mechanical pivotal support for the contact arm of a novel form that is highly effective in making low-resistance electrical connection to the contact arm.

Another object of this invention resides in the provision of a moving contact assembly having means for providing high contact pressure between the pivot of the contact arm and its support, so as to provide low contact resistance not only under short-circuit conditions, but also under normal load-current conditions and during contactopening operations.

A further object of the invention relates to improvements in the mounting and spring-biasing of arcing contacts on a pivoted contact arm. It is customary for arcing contacts to extend up into an arc chute, and in usual arrangements there is a blow-off electrodynamic force that tends to reduce arcing-contact pressure and to lift the arcing contact prematurely away from its companion contact during opening of the circuit breaker. A feature of the invention resides in the provision of heavy spring biasing means for the arcing contacts in a novel arrangement, wherein the hinge or pivotal connection of the contact arm is also improved. Moreover, despite this relationship between hinge contact pressure and arcing-contact pressure, means is provided for independently augmenting the hinge contact pressure without developing excessive arcing-contact pressure such as would impose an excessive mechanical load on the contact-closing mechanism.

The illustrative embodiment of the invention, which has been generally referred to above as incorporating the various novel features of the invention, is more fully described in the remainder of this specification, from which further novel features, objects and advantages will become apparent. In the following description, reference is made to the accompanying drawings forming part of this disclosure.

In the drawings:

FIG. 1 is a side elevation of an illustrative circuit breaker embodying features of the invention;

FIG. 2 is a front elevation of the apparatus in FIG. I viewed from the left thereof, with portions omitted and other portions broken away; and

FIG. 3 is a view similar to FIG. 1, of the moving contact assembly of a single pole, including main and arcing contacts, the parts being shown with the arcing contacts touching and the main contacts parted.

Referring now to the drawings, a frame is shown bearing three blocks 12 of insulation. Each book supports the stationary and movable contacts in a respective 3,158,720 Patented Nov. 24, 1964 pole of the three poles illustrated. Each pole has a pair of rearwardly projecting terminals 14 and 16. Terminal 14 extends through the block of insulation to the front thereof where it bears stationary arcing contacts 18. A number of side-by-side main contact members 22 are confined between a pair of side plates 24. Hinge ends 26 of the main contact members 22 are biased by springs 28 into a groove in terminal 14.

When the circuit breaker is closed as illustrated in FIG. 1, main contact members 22 are forcibly displaced to the right against their compression springs 28 by the cooperating movable main contact 30. When contact arm 30 is operated to the left (as described in further detail below) so as to open the circuit breaker, compression springs 28 drive main contact members 22 clockwise about their hinge ends 26. Ears 32 of contact members 22 limit their counterclockwise movement by engagement with stationary pin 34 (FIG. 3) supported between side plates 24, and in this way these contacts are under substantial spring bias from the instant of engagement of contact arm 30 with contact members 22.

Terminal 16 provides a conductive path through block 12 and through two-turn over-current coil 36, forward through a hinge block 38 to movable contact arm 30. Cooperating with the over-current coil 36 is movable armature 37 and associated structures whose details are unnecessary to an understanding of the present invention.

Movable contact arm 30 is formed of a pair of vertical bars 30a brazed to and thus united by a horizontal part 30b. Contact arm 30 has a pair of laterally spaced hooks 40 (see also FIG. 3) that are received in slots 42 formed in block 38, one for each hook 40. (See the left-hand pole in FIG. 2.) A shaft 46 is united to block 38 and extends across the slots 42 in which hooks 40 are received. A slot 44 is formed in contact arm 30 adjacent the base of hook 40. The top and right-hand surfaces of slot 44 diverge and provide contact engagement along two arcuately spaced lines of contact along shaft 46.

Members

30, 38, and 46, are of copper, advantageously silver-plated, and form a hinge connection of extremely low resistance and high current capacity. Contact pressure is maintained between moving contact arm 30 and shaft 46 by a pressure roll 48 and a spring bias means to be described.

The conductivity of the hinge joint is excellent during normal conditions when currents of the order of one or two thousand amperes may be carried. However, when short-circuit current peaks are to be carried, the pressure between moving contact arm 30 and the hinge shaft 46 is greatly increased by virtue of the geometry of the conductors providing the main current path through the circuit breaker. There is a broad current loop extending horizontally through terminal 14, downward through the main contacts 22 and contact arm 30, and horizontally through terminal 16. This loop provides electrodynamic force tending to shift moving contact arm 30 to the left. Contact arm 30 thus tends to pivot clockwise about a mechanical operating pivot 75 (described below), building up the contact pressure of moving contact arm 30 against shaft 46. This tendency of member 39 to move to the left in FIG. 1 is resisted by the hooks 40 extending about shafts 46. Consequently, it is safe for notches defined by hooks 40 and the opposite portion 41 of arm 30 to open outwardly of the current loop through parts 14, 22, and 16.

The movable contact arm 30 in each pole bears a pair of laterally separated movable arcing contacts 50 which cooperate with stationary arcing contacts 18. The lateral separation between the arcing contacts 50 is maintained by suitably shaped insulating spacer 66 (FIG. 2). Rocker member or lever 62 is carried on pivot pin 70 which passes through moving contact arm 30.

Arcing contacts

18 and 50 engage at a point spaced vertically above the

main contacts

22 and 30, the arcing contacts 50 extending well up into an arc chute 51 only part of which is shown. In the closed condition of the circuit breaker as illustrated in FIG. 1 and even when

main contacts

22 and 30 are parted (FIG. 3) arcing contacts 50 are biased against stationary arcing contacts 18 by compression springs 52 which press against shoes 54 pivoted by pins 56 to the arcing contacts 50. Coil springs 52 are guided on rods 58 which are secured at one end to shoes 54. Insulated bushings 59 are interposed between the springs 52 and the shoes 54 to inhibit the flow of current through the springs. Rods 54 work slidably in suitable bores in a shaft 60 that is rotatably mounted in rocker member 62. Each of the arcing contacts 50 is biased clockwise by a spring 52, and pivots about a hinge contact pin 64, which is received in moving contact arm 30.

The reaction of the upward pressure by springs 52 against arcing contact 50 is applied to rocker member 62 in a manner that also develops heavy bias of roller 48 against shaft 46. The short lever arm between roller 48 and pivot pin 70 provides mechanical advantage that magnifies the force applied to shaft 46 by the springs 52 which act on the longer lever arm between the axis of shaft 60 and pivot pin 70. This bias on roller 48 provides normal operating contact pressure at the

main hinge contact

40, 46 of the movable contact arm 30 this pressure being at its maximum in the contact closed or on position.

Compression springs 72 act between portions of

members

30 and 62 well above pivot pin 79, to augment the pressure developed by springs 52 between

elements

40 and 46 when the circuit breaker is closed, and to provide hinge contact presstu'e when the circuit breaker is open and springs 52 no longer apply bias to rocker 62. The pressure of springs 72 assures proper mechanical pivoting operation of the contact arm at times when the arcing contacts are disengaged and it also provides good electrical contact at

hinge

40, 46 when the contacts are being opened. This is an important concern in the event that the circuit breaker is tripped open to interrupt currents of short-circuit magnitude, 50,000 amperes for example. This augmented hinge contact pressure is produced without correspondingly increasing the clockwise bias acting on the arcing contacts 50. Any excessive increase in the arcing-contact bias beyond the value needed for establishing normal operating contact pressure would unnecessarily increase the force required to close the circuit breaker.

Shaft 75 extends laterally beyond both side faces of moving contact arm 3%) and into the U-shaped member 76 carried by the common bar '78 which operates all of the contact arms and the arcing contacts of all three poles of the circuit breaker. The bar 78 and U-shaped members 76 form a driving link for moving the contact arms 36 between the open and closed positions thereof. An exemplary mechanism for operating bar 78 is described in my copending application Serial No. 101,314, filed concurrently herewith (now Patent No. 3,097,275), both applications having a common assignee.

When the circuit breaker is open, movable arcing contact 50 is spaced well away from stationary arcing contact 13. At this time, clockwise displacement of arcing contact 50 relative to contact arm 30 due to the clockwise bias of spring 52 is adjustably limited by nut 74. When the circuit breaker is in its closed configuration as illustrated in FIG. 1, nut or stop 74- has a small but definite separation from shaft 60. This spacing is made large enough to insure counterclockwise travel of moving contact arm 36 through a sufficient angle in an opening stroke to allow car 32 of main contact members 22 to be arrested by pin 34 and for a definite separation to be developed between the main contacts represented by members 22 and contact arm 30. Thereafter, during continued contact-opening travel of moving contact arm 30, shaft 60 comes into engagement with stop 74, as shown in FIG. 3. From this point on, operation of tie bar 78 in the opening direction provides positive drive to separate each arcing contact 50 from its companion stationary arcing contact 18.

It may now be considered that the circuit breaker is open or at an intermediate position with the main and arcing contacts parted, rather than in the closed condition shown. In the parted-contacts condition, springs 52 and 72 (there being two of each at each pole) bias rocker member 62 counterclockwise about pivot and thereby develop relatively heavy pressure of roller 48 against shaft 46. The reaction force resulting at shaft 70 in contact arm 30 acts to force hooks 4d of the moving contact arm 30 against the face of shaft 46 opposite roller 48.

When the circuit breaker is open and is to be closed, tie bar 78 is shifted to the right and the shafts of the several poles are swung clockwise in unison about the common axis of respective shafts 46. The moving arcing contacts 50 in each pole engage companion contacts 18, and nuts 74 are lifted from shafts 60 as shafts 75 continue their travel to the right. Thereafter, the moving contact arm 30 engages its companion contact members 22 in each of the three poles of the circuit breaker. Drive of tie bar 78 continues for a short distance after initial engagement of the

main contacts

22 and 30, building the contact pressure up by shifting main contact 22 to the right, and increasing the compression that is maintained initially in springs 28 by ears 32 and pin 34.

High hinge contact pressure is maintained at book 40 and shaft 46 of each contact arm 30, both when the circuit breaker is closed and when the contacts are being opened. Springs 52 function for the dual purposes of establishing arcing-contact pressure and for biasing lever 62 so as to force roller 48 against shaft 46 and thereby to develop strong contact pressure between the hinge elements 4t) and 46 of the contact arm 30. Hinge contact pressure is augmented by springs 72. These springs provide the only spring bias for the hinge at times when arcing contacts 50 are out of contact with contacts 18.

The term circuit breaker as used in this application ap plies to apparatus intended to carry high currents and to interrupt currents of short-circuit magnitude; and accordingly the term circuit breaker is used in a generic sense, to apply also to switches having similar duty re quirements.

The foregoing represents the presently preferred form in which the various aspects of the invention may be applied. However, various modifications will readily occur to those skilled in the art, and therefore, the invention should be broadly construed in accordance with its full spirit and scope.

What I claim is:

l. A circuit breaker including first and second terminal members, a movable contact arm, a companion contact mounted on said first terminal member, said contact arm being pivotally mounted on said second terminal member for movement from a closed position abutting said companion contact to an open position, a driving link connected to said arm for moving said arm between said open and said closed position, a current loop being formed by said terminals, said companion contact and said contact arm in its closed position, said second terminal being provided with a hinge element including a hinge shaft, said contact arm being provided with a complementary hinge element partially encompassing said shaft and providing electrical connection and mechanical articulation thereto, said complementary hinge element having an opening formed therein directed away from said current loop, said hinge elements being driven together in a given direction by electrodynamic forces due to high currents flowing in said loop, and spring means normally biasing said hinge elements together in said given direction.

2. A circuit breaker including first and second terminal members, a movable contact arm, a companion contact mounted on said first terminal member, said contact arm being pivotally mounted on said second terminal member for movement from a closed position abutting said companion contact to an open position, a driving link connected to said arm for moving said arm between said open position and said closed position, a current loop being formed by said terminals, said companion contact and said contact arm in its closed position, said second terminal being provided with a hinge element including a hinge shaft, said contact arm being provided with a complementary hinge element partially encompassing said shaft, said complementary hinge element having an open ing formed therein directed away from said current loop, said hinge elements being driven together in a given direction by electrodynamic forces due to high currents flowing in said loop, and spring means normally biasing said hinge elements together in said given direction, said spring means applying biasing force to said shaft portion exposed at the opening in said complementary hinge element.

3. A circuit breaker including first and second terminal members, a movable contact arm, a companion contact mounted on said first terminal member, said contact arm being pivotally mounted on said second terminal member for movement from a closed position abutting said companion contact to an open position, a driving link connected to said arm for moving said arm between said open and said closed position, a current loop being formed by said terminals, said companion contact and said contact arm in its closed position, said second terminal being provided with a first hinge element, said contact arm being provided with a complementary hinge element, said hinge elements being driven together in a given direction by electrodynamic forces due to high currents flowing in said loop, and spring means normally biasing said hinge elements together in said given direction, said spring means including a lever pivotally mounted on said contact arm and bearing against said first hinge element and a spring reacting between said lever and said contact arm.

4. A circuit breaker including first and second terminal members, a movable main contact arm, an arcing contact arm pivotally mounted on said main contact arm, companion main and arcing contacts, respectively, mounted on said first terminal member, said contact arm being pivotally mounted on said second terminal member for movement from a closed position wherein said main contact arm and said arcing contact arm abutt said respective companion contacts to an open position, a driving link connected to said arm for moving said arm between said opened position and said closed position, a main current loop being formed by said terminals said companion main contact and said main contact arm in its closed position, said second terminal being provided with a hinge element, said main contact arm being provided with a complementary hinge element, said hinge elements being driven together in a given direction by electrodynamic forces due to high currents flowing in said loop, first spring means normally biasing said hinge elements together in said given direction, said spring means including a lever pivotally mounted on said contact arm and bearing against said hinge element and a spring reacting between said lever and said contact arm, and second spring means between said arcing contact arm and said lever further biasing said hinge elements together in said given direction in the closed position of said contact arms.

5. A circuit breaker including first and second terminal members; a movable main contact arm; an arcing contact arm pivotally mounted on said main contact arm; companion main and arcing contacts, respectively, mounted on said first terminal member; said contact arm being pivotally mounted on said second terminal member for movement from a closed position wherein said main contact arm and said arcing contact arm abutt said respective companion contacts to an open position; a driving link connected to said arm for moving said arm between said opened position and said closed position; a main current loop being formed by said terminals, said companion main contact, and said main contact arm in its closed position; said second terminal being provided with a hinge element; said main contact arm being provided with a complementary hinge element; said hinge elements being driven together in a given direction by electrodynamic forces due to high currents flowing in said loop; first spring means normally biasing said hinge elements together in said given direction, said first spring means including a lever pivotally mounted intermediate its ends on said main contact arm and forming long and short lever arms, the end of said short arm operatively bearing against said hinge element, and a spring reacting between said long lever arm and said main contact arm; second spring means between said arcing contact arm and said long lever arm further biasing said hinge elements together in said given direction in the closed position of said contact arms.

6. A circuit breaker including a back plate, a pair of substantially parallel terminals extending through said back plate, and switching means at one side of said back plate extending from one of said terminals to the other when closed, said terminals and said switching means constituting a current loop that creates strong loopexpanding forces electrodynamically during short-circuit current conditions, said switching means including a contact arm having a mechanical and electrical hinge connection to one of said terminals, said hinge connection including a shaft and a bearing on said shaft, certain areas of said shaft and said bearing being forced together by said loop-expanding forces, and spring biasing means acting between said shaft and said bearing and arranged to provide contact pressure at said areas even in the absence of said loop-expanding forces.

References Cited in the file of this patent UNITED STATES PATENTS 1,749,200 Van Valkenburg Mar. 4, 1930 2,329,003 Seaman Sept. 7, 1943 2,581,181 Favre Jan. 1, 1952 2,627,559 Netzel Feb. 3, 1953

Claims

1. A CIRCUIT BREAKER INCLUDING FIRST AND SECOND TERMINAL MEMBERS, A MOVABLE CONTACT ARM, A COMPANION CONTACT MOUNTED ON SAID FIRST TERMINAL MEMBER, SAID CONTACT ARM BEING PIVOTALLY MOUNTED ON SAID SECOND TERMINAL MEMBER FOR MOVEMENT FROM A CLOSED POSITION ABUTTING SAID COMPANION CONTACT TO AN OPEN POSITION, A DRIVING LINK CONNECTED TO SAID ARM FOR MOVING SAID ARM BETWEEN SAID OPEN AND SAID CLOSED POSITION, A CURRENT LOOP BEING FORMED BY SAID TERMINALS, SAID COMPANION CONTACT AND SAID CONTACT ARM IN ITS CLOSED POSITION, SAID SECOND TERMINAL BEING PROVIDED WITH A HINGE ELEMENT INCLUDING A HINGE SHAFT, SAID CONTACT ARM BEING PROVIDED WITH A COMPLEMENTARY HINGE ELEMENT PARTIALLY ENCOMPASSING SAID SHAFT AND PROVIDING ELECTRICAL CONNECTION AND MECHANICAL ARTICULATION THERETO, SAID COMPLEMENTARY HINGE ELEMENT HAVING AN OPENING FORMED THEREIN DIRECTED AWAY FROM SAID CURRENT LOOP, SAID HINGE ELEMENTS BEING DRIVEN TOGETHER IN A GIVEN DIRECTION BY ELECTRODYNAMIC FORCES DUE TO HIGH CURRENTS FLOWING IN SAID LOOP, AND SPRING MEANS NORMALLY BIASING SAID HINGE ELEMENTS TOGETHER IN SAID GIVEN DIRECTION.