Circuit breaker rotary contact arm arrangement

Abstract: A rotary contact arrangement (20) for circuit breakers includes pairs of contact springs (23A, 23B, 24A, 24B) arranged on each side of a rotary contact arm (15). The contact springs (23A, 23B, 24A, 24B) interconnect between the rotors (17A, 17B) and the contact arm (15) via a pair of U-shaped levers (31A, 31B). The provision of the U-shaped levers (31A, 31B) provides uniform contact pressure between both pairs of fixed and moveable contacts (13A, 13B, 14A, 14B) to prevent contact erosion.

Description: This invention relates to circuit breaker, and, more particularly, to a circuit breaker rotary contact arm arrangement. Circuit breakers having a current interrupting module within a rotary contact arm arrangement whereby the circuit breaker movable contact arms are arranged at the opposite ends of the movable contact carrier are able to interrupt circuit current at a faster rate than circuit breakers having a movable contact carrier with a contact arranged at one end. U.S. Patent No. 5,310,971 entitled Rotary Contact System for Circuit Breakers, describes a rotary.contact arm that employs rollers between the contact springs and the contact arm to provide a uniform force distribution between the fixed contacts attached to the circuit breaker line and load straps and the movable contacts arranged at the opposite ends of the movable contact arm. One problem associated with a non-uniform force distribution between the fixed and movable contacts is the possibility of excessive contact erosion on the pair of contacts at the lower force points along the fixed contact surface. In an exemplary embodiment of the invention, a rotary contact arrangement for circuit breakers of the type including a pair of contact springs arranged on each side of the rotary contact arm, has the contact springs interconnected between the rotors and the contact arm via a pair of U-shaped levers. The U-shaped lever side arms interact with the perimeter surfaces of the rotors whereas the bights of the U-shaped levers interact with the shaped surfaces of the contact arm to insure uniform spring force between the fixed and movable contacts. Uniform contact pressure between both pairs of fixed and movable contacts in a rotary type circuit breaker is provided without having to interpose rollers between the contact springs and the movable contact arm, especially when used in multi-pole circuit breakers that require a separate movable contact arm in each of the separate poles. Document EP 0 589 498 discloses a device according to the preamble of claim 1. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- Figure 1 is a front perspective view of a rotary contact circuit breaker interior employing the rotary contact assembly according to one embodiment of the invention; Figure 2 is an enlarged front perspective view of the rotor assembly contained within the circuit breaker interior of Figure 1; and Figure 3 is an enlarged front perspective view of the rotor assembly contained within the circuit breaker interior of Figure 2 with the rotor plate removed to depict the U-shaped levers in greater detail. Referring to Figure 1, a rotor assembly 20 in a circuit breaker interior assembly is generally shown intermediate a line strap 11 and a load strap 12 and associated arc chutes 16A, 16B. Although a single rotor assembly is shown, it is to be understood that a separate rotor assembly is employed within each pole of a multi-pole circuit breaker and that each operates in a similar manner. The arc chutes 16A, 16B are similar to that described in U.S. Patent No. 4,375,021 entitled Rapid Electric Arc Extinguishing Assembly in Circuit Breaking Devices Such as Electric Circuit Breakers, which is incorporated by reference. Electrical transport through the circuit breaker interior proceeds from the line strap 11 to an associated fixed contact 13B to a movable contact 14B connected to one end of a movable contact arm 15. The current transfers then to the opposite end of movable and fixed contacts 14A, 13A to the associated load strap 12. The movable contact arm 15 moves a pivot 18 (pin) in unison with a rotor 17 upon articulation of the circuit breaker operating mechanism (not shown) by links 19A, 19B to move the movable contacts 14A, 14B between , CLOSED and OPEN positions. The rotor 17 responds to the rotational movement of the pivot 18 to effect the contact closing and opening. An extended pin 25 provides attachment of the rotor 17 with the circuit breaker operating mechanism through links 19A, 19B to allow manual intervention for opening and closing the circuit breaker contacts. Referring to Figure 2, a rotor assembly 20 a first embodiment of the invention is generally shown as a single unitary assembly comprising a pair of opposing rotor plates 17A, 17B joined by a pair of extended cylinders 21A, 21B each having a passageway as shown at 22. The rotor plates and cylinders are preferably fabricated from a glass-filled thermoset resin having good structural and electrical insulative properties and the central operating pivot 18 extends through both of the rotor plates as well as the movable contact arm 15. The rotor plates 17A, 17B each include, on their opposing perimeters, a U-shaped retainer slot 28 and a sloping carrier slot 29 which includes a raised radial stop as shown at 30. An opposing pair of contact springs 23A, 23B are guided along shaped carrier slots 29 at one end by spring pins 26A, to which one end of the springs is attached and are retained at an opposite end by means of spring pins 27B that are captured within U-shaped retainer slots 28. An opposing pair of contact springs 24A, 24 B are guided along shaped carrier slots 29 at one end by spring pins 26B to which one end of the springs is attached and are retained at an opposite end by spring pins 27A that are captured within U-shaped retainer slots 28. The spring pins 26A, 26B and 27A, 27B cooperate with a pair of U-shaped levers 31A, 31B in the manner best seen by now referring to the rotor assembly 20 shown in Figure 3 with the rotor plate 17A removed and the cylinders 21A, 21B sectioned to depict the U-shaped levers 31A, 31B in greater detail. Referring now to Figure 3, the U-shaped levers 31A, 31B connect with the central pivot 18 through apertures 41, 42 and each define a pair of opposing side arms 32A, 32B and 34A, 34B joined by bights 33, 35 respectively. The spring pins 26A, 27A at the ends of the contact springs 23A, 23B extend through openings 36 at the ends of the side arms 32A, 32B and terminate on the surface of the carrier slot 29, as indicated at 39. The bight 33 joining the side arms 32A, 32B rides along the surface 15B of one end of the movable contact arm 15. The bight 35 joining the side arms 34A, 34B rides along the surface 15A of the opposite end of the movable contact arm. It is to be understood that the spring pins 26B, 27B are arranged in as similar manner on the rotor plate 17A, shown earlier in Figure 2. The provision of the U-shaped levers 31A, 31B intermediate the rotor plates 17A, 17B and the surfaces 15A, 15B on the opposing ends of the movable contact arm 15 thereby allows the forces of the contact springs 23A, 23B and 24A, 24B to interact in feed-back relation, whereby a generally constant force is applied between the fixed and movable contacts 13A, 14A and 13B, 14B of Figure 1. The forces exhibited by the contact springs at one end of the movable contact arm are transmitted via interaction with the bight associated with the one end to the bight associated with the other end of the movable contact arm to adjust the position of the bight associated with the other end thereof. An increase in force between one pair of fixed and movable contacts at one end of the movable contact arms is accordingly reflected in a corresponding increase in force between the other pair of fixed and movable contacts resulting in a constant force between both pair of fixed and movable contacts through-out the operational life of the associated circuit breaker.

Claims: A circuit breaker rotary contact arrangement comprising: a pair of opposing circular rotor plates (17A, 17B), each of said rotor plates (17A, 17B) defining a carrier slot (29) on a perimeter thereof; a movable contact arm (15) intermediate said rotor plates (17A, 17B), said contact arm (15) defining a first movable contact (14A) at one end arranged opposite an opposing first fixed contact (13A) and a second movable contact (14B) at an end opposite said one end arranged proximate a second fixed contact (13B); a pivot pin (18) extending through said rotor plates (17A, 17B) and said movable contact arm (15), whereby said rotor plates (17A, 17B) and said movable contact arm (15) rotate in unison; a pair of first contact springs (23A, 23B), one of said first contact springs (23A) arranged on one side of said movable contact arm (15) and another of said first contact springs (23B) arranged on an opposite side thereof; characterised by a U-shaped lever (31A) intermediate said rotor plates (17A, 17B), said U-shaped lever (31A) defining a pair of side arms (32A, 32B) joined at one end bv a bight (33), said bight (33) arranged proximate a first shaped surface (13B) formed on said contact arm (15) for providing a constant spring force between said first and second fixed and movable contacts (14A, 13A). The rotary contact arrangement of Claim 1 including a spring retainer pin (26A) arranged through one end of each of said contact springs (23A, 23B) and through said side arms (32A, 32B), at an end of said side arms (32A, 32B) opposite said bight (33), said retainer pin (26A) defining a pair of opposing retainer pin ends, said retainer pin ends being positioned within said rotor carrier slots (29). The rotary contact arrangement of Claim 2 wherein said rotor plates (17A, 17B) further define a retainer slot (28) on said perimeter thereof and said contact springs (23A, 23B) include an additional spring retainer pin (27B) arranged through another end thereof, said additional spring retainer pin (27B) being arranged within said retainer slot (28). The rotary contact arrangement of Claim 2 including an additional U-shaped lever (31B) intermediate said rotor plates (17A, 17B), said additional U-shaped lever (31B) defining a pair of additional side arms (34A, 34B) joined at one end by an additional bight (35), said additional bight (35) arranged proximate a second shaped surface (15A) formed on said contact arm (15). The rotary contact arrangement of Claim 4 a pair of additional contact springs (24A, 24B), one of said additional contact springs (24A) arranged on said one side of said movable contact arm (15) and another of said additional contact springs (24B) arranged on said opposite side thereof. The rotary contact arrangement of Claim 5 including a first additional spring retainer pin (26B) arranged through one end of each of said additional contact springs (24A, 24B) and through said additional side arms (34A, 34B), at an end of said additional side arms (34A, 34B) opposite said additional bight (35), said additional retainer pin (26B) defining a first pair of opposing additional retainer pin ends, said first pair of opposing additional retainer pin ends being positioned within one of said rotor additional retainer slots (28). The rotary contact arrangement of Claim 6 wherein said rotor plates (17A, 17B) further define an additional carrier slot (29) on said perimeter thereof and said additional contact springs (24a, 24b) include a second additional spring retainer pin (27A) arranged through another end thereof, said second additional retainer pin defining a second pair of opposing additional retainer pin ends, said second pair of opposing additional spring retainer pin ends being arranged within said additional carrier slots (29). A circuit breaker interior assembly comprising: a line strap (11) arranged for connection with an electric circuit and a load strap (12) electrically connecting with said line strap (11) and arranged for electrically connecting with associated electrical equipment, said line and load straps (11,12) being intermittently connected by a rotary contact arrangement, said rotary contact arrangement (20) comprising a pair of opposing circular rotor plates (17A, 17B), each of said rotor plates (17A, 17B) defining a carrier slot (29) on a perimeter thereof; a pair of first and second arc chutes (16A, 16B), said first arc chute (16B) proximate said line strap (11) and said second arc chute (16A) proximate said load strap (12) for quenching arcs occurring upon overcurrent transfer between said line and load straps (11,12); and a rotary contact arrangement as claimed in any preceding claim.

Inventors: BAUER ROLF-DIETER, BAUER, ROLF-DIETER
Applicants: AEG NIEDERSPANNUNGSTECH GMBH, AEG NIEDERSPANNUNGSTECHNIK GMBH & CO. KG
Application year: 1999
Main classification: H01H73
IPC codes: H01H73