Abstract: A drilling head with a cone rock bit, each cone having a stationary part and a rotary part which rotates about an axis of rotation. Also included is a dynamic sealing device between the stationary part and the rotary part. The sealing device is borne by the rotary party and has a first sealing lip and a second sealing lip, each of which forms a surface of revolution about the axis of rotation. Further, the first and second lips bear respectively against a first bearing face and a second bearing face secured to the stationary part. The first lip is oriented in such a way that it presses against the first bearing face under the action of the pressure, and the second lip is oriented in such a way that it moves away from the second bearing face under the action of the pressure of the lubricating product, so as to allow this product to fill a cavity and compensate for the pressure in the cavity.