For certain applications it is required that a circuit breaker, after detecting a fault, opens the contacts and then quickly closes the contacts. When the fault remains, the contacts can then be kept open for a longer duration. The first opening and closing of the contacts should be performed in less than a second, typically less than 0,3 seconds. If the fault remains, the contacts can then be opened again and closed after a longer duration, for example a minute. This is called in the art an open-close-open (OCO) cycle.

Due to space restrictions in the switch gear, wherein the circuit breakers are applied, it is not possible to provide an electric motor, sufficiently strong and quick to open and close the contacts within a split second. So, a mechanism is required in which for example spring energy is used to provide the quick opening and closing of the contacts.

US 5107715 discloses a mechanism with open-close- open cycle for a circuit breaker. The circuit breaker is connected with a shaft which comprises a first, spring loaded, lever. The shaft is furthermore coupled via a freewheel coupling to a second shaft part on which a second, spring loaded, lever is arranged. When a fault occurs, the first lever is released driving the circuit breaker in an open position. Then the second lever is released driving the shaft further, such that the circuit breaker re-closes and the first spring is reloaded again. As the first lever is still

released, the reloaded first spring will drive the shaft yet again further, such that the circuit breaker opens again. This mechanism is quite complex and is voluminous.

Furthermore, the reloading of the first spring depends on the spring force of the second spring, which thus needs to provide both the force to operate the circuit breakers and the force to reload the first spring.

US 3729065 discloses a mechanism with a three rod system. One of the rods is kept in position by a trigger lever, while the other two rods are moved by a cam, such that the contacts are closed. When the contacts need to be opened, the trigger lever is operated, such that the rod system becomes undefined and the contacts are opened under spring force .

For reclosing the contacts, the trigger lever has to push the respective rod back in position, after which the cam can move the other rods to close the contacts. In order to have a quick reclosing within under a second, the movement of the trigger lever and the cam need to be synchronized, which is difficult.

It is an object to provide a mechanism, which reduces or even removes the above mentioned disadvantages.

This object is achieved according to the invention with a mechanism for opening and closing a circuit breaker having an operating rod for moving the contacts of the circuit breaker between an open position and a closed position, which mechanism comprises

- a frame ;

- a first rod hingedly arranged with one end to the frame ;

- a second rod hingedly arranged with one end to the other end of the first rod and arranged with the other end slidable to the frame between a contact open position and a contact closed position in a direction substantially

perpendicular to the direction of movement of the other end of the first rod;

- a first cam arranged on one side of both rods; - a second cam arranged on the opposite side of both rods; and

- a roller arranged on either the first rod or second rod, adjacent to the other end of the first rod;

wherein the first cam is in contact range with the roller in the contact closed position and wherein the second cam is in contact range with the roller in the contact open position .

With the mechanism according to the invention, a toggle mechanism is provided with which the contacts can easily be operated from a closed position to an open position and back to a closed position. This is achieved by rotating the first cam to toggle the mechanism from the closed to the open position and then by rotating the second cam to toggle the mechanism back from the open position to the closed position .

Under the term "in contact range" it must be

understood in the context of this invention, that by rotating the cam can be brought into contact with the roller.

A preferred embodiment of the mechanism according to the invention further comprises spring means arranged between the frame and the other end of the second rod to urge the other end into the contact open position.

A circuit breaker typically has an internal spring for urging the contacts to an open position. This internal spring could be used in combination with the rods of the mechanism to obtain the toggle action of the mechanism.

However, not all internal springs are sufficient nor do all operable contacts have such an internal spring. By arranging spring means between the frame and the other end of the second rod, the mechanism it self is provided with the required spring force for the toggle action. This provides reliability and allows for a more controlled movement within the required time frame for reclosing the contacts.

In a further preferred embodiment of the mechanism according to the invention at least one of the first cam and the second cam comprise cam spring means for rotatably urging the respective cam and locking means for locking the rotation of the respective cam.

By providing spring means to one or both cams, the rotation of the cams can be initiated by releasing the locking means, while the spring means will provide sufficient force to push the roller and toggle the mechanism from the closed to the open position or vice versa.

Preferably, the cam spring means comprise a tension spring, which tension spring is arranged with one end to the frame and with the other end to the respective cam offset from the center of rotation.

Yet another embodiment of the mechanism according to the invention further comprises at least one stopper pin for limiting the movement of the two rods.

The stopper pins limit the movement of the rods and prevent that the rod system moves to far when moving from the one position to the other position. This could result in damage or disfunction of the mechanism.

When the mechanism is being moved from the closed to the open position and then within a fraction of a second back to the closed position, the stopper pins stop the rods in the correct closing position, even when the first cam is not yet in the starting position, as it was rotated to initiate the open and reclose motion of the mechanism. This further

prevents the contacts from reopening due to the rods moving past the position in which the cam would contact the roller in the contact closed position.

The invention also relates to a combination of a mechanism according to the invention and a circuit breaker comprising two contacts movable relative to each other between a closed position and an open position, and an operating rod arranged to at least one of the contacts for moving the at least one contact, wherein the other end of the second rod is in contact with the operating rod to move the operating rod to open and close the contacts.

These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

Figures 1 - 4 shows schematically an embodiment of a combination according to the invention in different positions.

Figure 1 shows a combination 1 according to the invention. The combination 1 has a circuit breaker with a fixed contact 2 and a movable contact 3 to which an operating rod 4 is arranged.

According to the invention, the operating rod 4 is operated by a mechanism, which comprises a first rod 5, which is arranged hingedly with one end 6 to the frame of the combination 1, while at the other end 7 a roller 8 is

arranged. A second rod 10 is arranged with one end 9 to the other end 7 of the first rod and is arranged with the other end 11 in a slot 12 to allow for substantial vertical

movement, while the other end 7 of the first rod 5 moves in a substantial horizontal direction. The other end 11 of the second rod 10 is connected to the operating rod 4 of the movable contact 3, such that movement of the rod system 5, 10 results in movement of the operating rod 4 and accordingly opening and closing of the contacts 2, 3.

A first cam 13 is arranged on one side of the rods 5, 10, while a second cam 14 is arranged on the other side of the rods 5, 10. The first cam 13 has a lever 15 to which a spring 16 is arranged, while the second cam 14 has a lever 17 to which a spring 18 is arranged. Both cams 13, 14 are

furthermore provided with locking means (not shown) , which are known in the prior art and which allow for controlled release of the spring 16, 18 force and according rotation of the cams 13, 14 respectively.

Furthermore a spring 19 is arranged to the other end 11 of the second rod 10, which urges the contacts 2, 3 to an open position. In figure 2, the locking means of the second cam 14 are released, such that the spring 18 rotate the cam 14 by pulling on the lever 17. The second cam 14 will push the roller 8 towards the first cam 13. As soon as the axis of the roller 8 passes the plane extending through the first end 6 and the other end 11, the spring 19 will push both rods 5, 10 further until the rod 10 contacts a stopper pin 20. This ensures that the rod system 5, 10 stops in the contact closed position at which the contacts 2, 3 are fully and reliably closed. If the rod system 5, 10 would move too far, the contacts 2, 3 could reopen.

Referring to figure 3, when a fault occurs, the locking means of the first cam 13 are released such that the spring 16 can start to rotate the cam 13 by pulling on the lever 15. As a result, the first cam 13 will be brought into contact with the roller 8, moving the roller towards the second cam 14. The second cam 14 has been put in its initial position, where the spring 18 is tensioned again, similar to the position shown in figure 1.

As soon as the axis of the roller 8 passes the plane extending through the first end 6 and the other end 11, the spring 19 will push both rods 5, 10 further until the roller 8 contacts the second cam 14 and the contacts 2, 3 are opened. ( see figure 4 ) .

If a quick reclosing of the contacts 2, 3 is

desired, the locking means of the second cam 14 are released again, such that the roller 8 is pushed back to the first cam 13 and the contacts 2, 3 are closed again, such as explained in conjunction with figure 2.