AN IMPROVED FLIP-LOCK ARRANGEMENT FOR DOUBLE BREAK CONTACT SYSTEM IN A CIRCUIT BREAKER
Field of the invention
[0001] The invention generally relates to molded case circuit breaker. More particularly the invention relates to circuit breaking device for a low voltage current limiting molded case circuit breaker.
Prior Art [0002] In one of the prior art known the contact bridge of a molded case circuit breaker is rotatably mounted in a bar by two springs arranged symmetrically from the rotation axis. Each spring is, on the one hand, anchored to the contact bridge, and, on the other hand, anchored to a rod housed in a notch of the bar. The same springs provide contact pressure and slowing-down of opening of the contact bridge at the end of repulsion travel by electrodynamic effect. The contact bridge bears on its edge cam surfaces, which, at the end of opening travel, engage the anchoring rods to move them in the notches in the elongation direction of the tension springs. The energy of the contact bridge is thus taken up and stored in the springs causing slowing-down of the contact bridge. The profile of the cams can be chosen to enable reclosing of the contact bridge, this reclosing naturally being delayed by the slowing-down effect at the end of travel. The cam profile can also ensure latching of the contact bridge in the open position.
[0003] In other prior art known a movable contact bridge of a molded case limiting circuit breaker is supported by a bar by a system of springs enabling opening with electrodynamic repulsion. The contact bridge cooperates with stationary contacts rigidly secured to current input conductors in the shape of half-loops. An anvil is adjoined to the rear of the stationary contacts to increase the closing impact effect of the contact bridge and prevent contact resistance dispersions. The anvil is made of ferromagnetic material increase the magnetic field for blowout of the arc to the extinguishing chambers.
[0004] According to another prior art known a breaking device for a low voltage circuit breaker comprises in each pole a switching bar, a pair of stationary contacts

connected to the connection terminals, a double-break rotary contact extending in a housing of the bar, and two arc chutes disposed on each side of the bar. Two contact pressure springs ensure elastic positioning of the rotary contact along the longitudinal direction of the pole. Pivoting of the rotary contact takes place around a fictitious axis mounted floating with respect to the fixed rotation axis of the bar. [0005] Hence there is a need for a flip-lock mechanism for double break contact system in a circuit breaker with high contact pressure. Further, the flip lock mechanism should provide a higher spring force and facilitate automatic flipping of the contact at minimum rotation. There is also a need for a flip lock mechanism that facilitates easier assembly of the components.
OBJECT OF THE INVENTION
[0006] It is an object of the invention to provide an improved flip-lock mechanism
for double break contact system in a circuit breaker. More particularly, it is an
object of invention to provide easy flip-lock mechanism with high contact
pressure.
[0007] It is another object of the invention to provide a mechanism to provide the
process of assembling the compression spring is easy for higher spring force. It is
also an object of the invention to provide alignment of spring such that it helps in
automatic flipping at minimum rotation.
[0008] It is further object of the invention to provide a new casing design, which
provides easier assembly.
[0009] It is another object of the invention to provide a design for higher breaking
capacity due to robust components and simple assembly.
BRIEF DESCRIPTION OF THE DRAWINGS [0010] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of

this invention and are therefore not to be considered limiting of its scope, for the
invention may admit to other equally effective embodiments.
[0011] Figure 1 shows outline diagram of the contacts of a pole of circuit breaker
according to an example of an embodiment of the invention,
[0012] Figure 2 shows outline diagram of the contact of the pole of circuit breaker
according to an example of an embodiment of the invention.
[0013] Figure 3 shows outline diagram of the contact system according to an
example of the invention.
[0014] Figure 4 shows outline diagram of the moving contact assembly according
to an example of an embodiment of the invention.
[0015] Figure 5 shows outline diagram of the contact system as incorporated in a
circuit breaker according to an example of an embodiment of the invention.
[0016] Figure 6a shows outline diagram of the contact system before assembly
according to an example of an embodiment of the invention.
[0017]Figure 6b shows outline diagram of the contact system after assembly
according to an example of an embodiment of the invention.
DETAILED DESCRIPTION OF INVENTION
[0018] The invention relates to molded case circuit breaker. More particularly the invention relates to circuit breaking device for a low voltage current limiting molded case circuit breaker.
[0019] Figure 1 shows outline diagram of the contacts of a pole of circuit breaker in the closed position according to an example of an embodiment of the invention. The molded case circuit breaker comprises of a pair of fixed contacts (2), a moving contact (1) hinged at the center to provide equal spring force distribution and make the rotary contact symmetrically, casing 0 where the moving contact (1) and compression springs (3) are placed. The rotary contact system is divided into two hemispherical rotor halves. In an example of the invention, each of hemispherical half is configured with a protrusion member at one end and a receiving member at other end. In an another example of the invention, one hemispherical half is configured to have only receiving member at its either end and the other

hemispherical half is configured to have only the protrusion member at its either end.
[0020] In an example of the invention, the first compression spring (3) is positioned within one hemispherical rotor half and the second spring is positioned within the second hemispherical rotor half also shown in Figure 6 and is then screwed with self taping screws. In the process the compression spring (3) is in its uncompressed state during initial stage of screwing and when the screwing completes the compressing spring (3) provides the necessary contact force. [0021] According to an example of the invention, the first hemispherical rotor half and the second hemispherical rotor half are configured to adjoin with each other to enclose the first and second compression spring. Further, the moving contact (1) is sandwiched between hemispherical rotor half comprising a first compression spring and second hemispherical rotor half comprising second half. The arrangement of flip-lock is such that, the moving contact (1) centrally adapted to receive the spring from each of the hemispherical halves providing equal spring distribution. The moving contact also includes a central portion having a non-circular opening for receiving the spring from each of the hemispherical rotor halves,
[0022] According to an example of the invention, the flip-lock is arranged such that the first hemispherical rotor half is arranged with in inner side, while second hemispherical rotor half mounted with an inner side over the first hemi-spherical rotor half and rotatably mounting a moving contact over the hemispherical rotor half. The one end of first spring is mounted on the pine provided within the first hemispherical rotor half and coupling the other end of a first spring to a first non-circular groove provided on the rotatably mounted moving contact. The one end of second spring is mounted on the pin provided within the second spring to a second non-circular groove situated diametrically opposite on the rotatably mounted moving contact and adjoining the first hemispherical rotor half and the second hemispherical rotor half with each other as mentioned above.

[0023] Figure 2 shows outline diagram of the contact system in its flipping condition where the forces due to compression spring are theoretically zero according to an example of an embodiment of the invention. [0024] Figure 3 shows outline diagram of the contact system where the moving contact (1) has crossed the dead center and is in resting position. The current input through the input fixed conductor, closing moving conductor and the output fixed conductor leads to formation of a closed loop. The current flowing in the fixed conductor and the moving conductor are in opposite direction, which produces a magnetic forces that repels each other but one conductor is fixed so the effective force is on the other contact which is movable. Further, as soon this repelling force goes higher than the spring force it provides the contact pressure, the moving contact (1) starts opening. The spring is arranged in a manner that whenever the contact moves away from the fixed contact (2), the force on the moving contact (1) increases gradually till the contact reaches the dead center and further reduces after crossing dead center. The electromagnetic force required for further repulsion is very less after crossing the dead center.
[0025] The invention, as described herein and as illustrated by diagrams provide an improved flip-lock mechanism for a double break contact system in circuit breaker.
[0026] The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

We claim:
1. A flip lock arrangement for a rotary contact system comprising:
a first hemispherical rotor half;
a first spring positioned within the first hemispherical rotor half;
a second hemispherical rotor half;
a second spring positioned within the second hemispherical rotor half; and
a moving contact rotatably mounted and centrally adapted to receive the
spring from each of the said hemispherical halves.
2. A flip lock arrangement of claim 1, wherein the first hemispherical rotor half and the second hemispherical rotor half are configured to adjoin with each other to enclose the first and second springs;
3. A flip lock arrangement of claim 1, wherein the moving contact is sandwiched between a first hemispherical rotor half comprising a first spring and a second hemispherical rotor half comprising a second spring.
4. A flip lock arrangement of claim 1, wherein the moving contact centrally adapted to receive the spring from each of the said hemispherical halves provides equal spring force distribution.
5. A flip lock arrangement of claim 1, further wherein the moving contact includes a central portion having a non-circular opening for receiving the spring from each of the said hemispherical rotor halves.
6. A flip lock arrangement of claim 1, wherein the first spring and second spring are compression springs.
7. A method for assembling a flip lock arrangement for a rotary contact system, the method comprising:
arranging a first hemispherical rotor half with an inner side;
rotatably mounting a moving contact over the first hemispherical rotor half;
mounting one end of a first spring on the pin provided within the first
hemispherical rotor half and coupling the other end of a first spring to a
first non circular groove provided on the rotatably mounted moving
contact;

mounting a second hemispherical rotor half with an inner side over the first
hemispherical rotor half;
mounting one end of a second spring on the pin provided within the second
hemispherical rotor half and coupling the other end of a second spring to a
second non circular groove situated diametrically opposite on the rotatably
mounted moving contact; and
adjoining the first hemispherical rotor half and the second hemispherical
rotor half with each other by mating at least one of: a protrusion on the first
hemispherical rotor half with a receiving portion on the second
hemispherical rotor half; and, a protrusion the second hemispherical rotor
half with a receiving portion on the first hemispherical rotor half.
8. The method of claim 7, wherein the first spring is uncompressed before
adjoining the first hemispherical rotor half and second hemispherical rotor half
and further wherein the second spring is uncompressed before adjoining the
first hemispherical rotor half and second hemispherical rotor half.
9. The method of claim 7, wherein the first spring is compressed after adjoining
the first hemispherical rotor half and second hemispherical rotor half and
further wherein the second spring is compressed after adjoining the first
hemispherical rotor half and second hemispherical rotor half.
10. A circuit breaker comprising:
a first fixed contact;
a second fixed contact;
an arch chute; and
a flip lock arrangement as claimed in claims 1 - 6 and as assembled by the
method as claimed in claims 7-9.