Medium or high voltage circuit breaker

A medium-or high-voltage circuit breaker, comprising:

• a first arcing contact and a second arcing contact that are axially movable relative to each other between an open position of the circuit breaker, in which the arcing contacts are separated from each other, and a closed position of the circuit breaker, in which the arcing contacts are in contact with each other,
• wherein the first arcing contact includes a contact opening on a first side facing the second arcing contact, the first arcing contact being configured to receive the second arcing contact within the contact opening when the arcing contacts are in the closed position,
• wherein the first arcing contact is disposed in a support member on a second side facing away from the second arcing contact and in an auxiliary nozzle on the first side of the first arcing contact,
• wherein the auxiliary nozzle comprises an auxiliary nozzle opening aligned with the contact opening and is made of a fluorocarbon polymer,
• wherein the support member and the auxiliary nozzle are connected to each other by a threaded connection including an anti-loosening mechanism configured to prevent the auxiliary nozzle from moving relative to the support member in a screw-out direction.