A blow molding system for a thermoplastic blank which is supported in a mold. The system includes a fixed tubular body connected to a high-pressure fluid source and, at the lower end thereof, supporting moveable equipment consisting of a tuyere, the tuyere being defined laterally by a terminal sleeve of the moveable equipment and the bottom thereof being the front wall of the body, wherein the lateral inner wall of the sleeve is configured in such a way that the pressure of a fluid inside the tuyere does not result in a reaction force component on the lateral wall, which is directed opposite to the wall of the mold.
