If after closure the fault current persists the circuit breaker will trip, opening the contacts again. If the fault current was just temporary, the circuit breaker

continues to operate in closed condition.

To operate a circuit breaker it is known to use an operating mechanism with at least two linked rods hinging in a single hinge plane. On end of the linked rods is arranged to the frame of the circuit breaker, whereas the other free end of the linked rods is attached to the operating rod of the circuit breaker to move the movable contact of the circuit breaker .

With the known mechanism a cam arranged on an axle is provided, which engages on one of the hinges of the linked rods, typically the hinge, which connects two rods. This allows for a rotation to be converted into a translation to move the contacts of the circuit breaker to a closed position. It also allows for a small rotation force to be converted into a high closing force. The disadvantage is however, that in order to generate a high force with a small force, the path of travel is long, which prevents quick opening of the contacts of the circuit breaker.

A circuit breaker with such a cam and linked rods mechanism is shown in GB 1319269. This publication also shows a latch with which the operating rod of the circuit breaker is locked, while the contacts are in the closed position. This latch is provided according to GB 1319269 to withstand sudden abrupt magnetic repulsion forces.

It is however desired to provide a circuit breaker which allows for OCO functionality, wherein a cam and linked rods mechanism is used for moving the contacts between an open and closed position.

It is an object of the invention to reduce the above mentioned disadvantages.

This object is achieved with a circuit breaker comprising :

- a frame ;

- a first contact fixed to the frame and a second contact movable arranged to the frame and relative to the first contact between a closed and an open position, wherein the contacts are urged to the open position;

- at least two linked rods hinging in a single hinge plane, wherein a first free end of the linked rods is arranged hingedly to the frame and wherein a second free end of the linked rods is arranged hingedly to the second movable

contact ;

- a first cam arranged on an axle, which axle is rotatable arranged in the frame, wherein the cam is arranged parallel to and in the hinge plane and wherein the lobe of the cam is arranged to engage on the linked rods to move the contacts between a closed and an open position;

- drive means for rotatably driving the axle;

- a latch tiltable arranged to the frame, which latch engages on the at least two linked rods in the closed position of the contacts; and

- an actuator for disengaging the latch from the at least two linked rods to have the contacts move to the open position .

With the circuit breaker according to the invention the contacts of the circuit breaker can be moved to the closed position by rotating the cam, which in turn operates the linked rods, which move the movable second contact towards the first contact.

The latch then engages the linked rods, such that the cam is no longer required to push against the linked rods and to keep the contacts in the closed position. After the latch has engaged, the cam can be rotated out of contact with the linked rods.

When a short circuit or a fault event occurs, the actuator is operated to disengage the latch, releasing the linked rods, such that the contacts of the circuit breaker can move to the open position.

Then the cam can be driven to rotate and move the linked rods to close the contacts again.

The invention thus allows for a quick opening of the contacts, even though a cam and linked rod mechanism is used. This in turn allows for the desired OCO functionality.

In a preferred embodiment of the circuit breaker according to the invention the latch is tiltable in a tilting plane parallel to the hinge plane, further comprising a second cam arranged on the axle and arranged in the tilting plane, wherein the latch comprises a contact surface for contact with the second cam for the second cam to urge the latch into the engaged position.

When the first cam is rotated to operate the linked rods and to move the contacts to the closed position, the second cam will be able to take the latch along, such that the latch automatically engages on the linked rods, when the contacts arrive at the closed position. Thus with a single rotary movement of the axle, the contacts are closed and the latch is engaged on the linked rods.

Preferably, the circuit breaker according to the invention further comprises first spring means for urging the latch to an unlatched position.

In yet another preferred embodiment of the circuit breaker according to the invention the actuator comprises a solenoid operated pin for locking the latch in the engaged position .

The solenoid operated pin allows for a quick release of the latch by a small current, which may be provided by a controller, which detects the short circuit or a fault event.

Yet another preferred embodiment of the circuit breaker according to the invention comprises further second spring means for rotatably urging the axle and locking means for locking the rotation of the axle.

By providing spring means for rotatably urging the axle, it is possible to tension or compress the spring means during normal operation of the circuit breaker. Once a short circuit of fault event occurs, and the latch has been

disengaged to quickly open the contacts of the circuit breaker, the energy stored in the spring means can be used to quickly rotate the axle and to quickly close the contacts again. This further shortens the time frame between the start of the opening cycle and the end of the closing cycle, which allows for even shorter open-close-open cycles.

Preferably the locking means comprise a second solenoid for electronically operating the locking means. The second solenoid could also be controlled by a controller, such that the OCO-cycle is fully controllable, while still a simple cam and linked rod mechanism is used for operating the circuit breaker .

In yet another embodiment of the circuit breaker according to invention the latch has an elongate body, a tilt axle arranged in the middle section of the elongate body, which tilt axle is arranged to the frame, wherein the actuator engages on a first end of the elongate body and wherein the other end of the elongate body engages the at least two linked rods .

Preferably, a cavity is arranged in the other end of the elongate body and wherein the at least two linked rods comprise a protrusion, preferably on a hinge of the linked rods, which is accommodated in the cavity in the engaged position of the latch.

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

Figures 1 - 4 show a schematic side view of an embodiment of the circuit breaker according to the invention in four different positions.

Figure 1 shows a circuit breaker 1 according to the invention. The circuit breaker 1 has a first contact 2 fixed to a frame 3 and a movable contact 4. Two linked rods 5, 6 are arranged with one end to the frame 3 and with the other free end to the movable contact 4.

The circuit breaker 1 has furthermore an axle 7 with a first cam 8 and a second cam 9. The first cam 8 is used to push against the hinge 10 between the two rods 5, 6 to move the contacts 2, 4 from an open position (shown in figure 3) to a closed position (shown in figure 1) .

An elongate latch 11 is also arranged via tilt axle 12 to the frame 3. The tilt axle 12 is arranged in the middle section of the latch 11. The latch 11 has on one end a contact surface 13 for contact with the second cam 9. Also a cavity 14 is provided in the latch 11 in which a protrusion of the hinge 10 can be accommodated.

A solenoid operated pin 15 is arranged at the other end of the latch 11 to lock the latch 11 in the engaged position, as shown in figure 1. A spring 16 is furthermore provided to urge the latch 11 to tilt around the tilt axle 12.

In figure 2, the axle 7 is rotated such that the first cam 8 is out of contact with the hinge 10 of the linked rods 5, 6 and such that the second cam 9 is out of contact with the contact surface 13 of the latch 11.

Because the latch 11 is locked by the pin 15 and the protrusion on the hinge 10 is captured in the cavity 14 of the latch, the contacts 2, 4 will remain in the closed postion.

When a short circuit or a fault event is detected, the pin 15 will be actuated to retract from the latch 11, such that the spring 16 will tilt the latch 11 and the hinge 10 will be released from the cavity 14 allowing the contacts 2, 4 to move to an open position. The contact surface 13 will then abut the second cam 9.

After a short period of time, typically less than 0.3 seconds, the axle 7 will be rotated further, such that the first cam 8 will contact the hinge 10 again and push the linked rods 5, 6 to move the contacts 2, 4 to the closed position again.

Simultaneously, the second cam 9, which is already in contact with the contact surface 13 will tilt the latch 11 back to a horizontal position, allowing the solenoid operated pin 15 to relock the latch 11 again and capture the protrusion of the hinge 10 in the cavity 14, to arrive at the position as shown in figure 1.

The rotation of the axle 7 could be done by an electric motor or the like, but it is preferred to use a spring (not shown) in combination with a electronically operated lock of the axle 7. The spring, when tensioned and when releasing the axle 7, allows for a quick rotation of the axle, which would otherwise require a powerful motor.

The spring can be retensioned during normal operation by an electric motor, which requires less power as speed is not essential, when retensioning the spring.