Apparatus and method of shaping plastics material pre-forms into plastics material containers with air extraction guided through a surge chamber

An apparatus for the shaping of plastics material pre-forms into plastics material containers with at least one blow moulding station which is arranged on a conveying device rotatable about a pre-set axis of rotation (D), wherein the blow moulding station has a blow mould and this blow mould forms a cavity in the interior of which the plastics material pre-forms are capable of being expanded by being acted upon with a gaseous medium to form the plastics material containers, with a stressing device, which acts upon the plastics material pre-forms with the gaseous medium in order to expand them, and with a clean room, which surrounds the blow moulding station at least in part, wherein this clean room is bounded off from an environment by at least two walls which are movable relative to one another, and the apparatus has a sealing device which bounds off from the environment the clean room in a region of the walls movable relative to one another, wherein the sealing device has a first continuous duct, which is capable of being filled with a liquid medium, as well as a first continuous wall member which is movable with respect to this duct and which is capable of being guided at least locally inside the liquid medium, wherein a line for a flowable medium extends in at least a portion of the duct, wherein this flowable medium is capable of being conveyed through this portion of the duct and is permanently separated from the liquid medium present in the duct, and wherein the apparatus has a second wall member which is movable with respect to the duct and which is arranged at a distance from the first wall member in a radial direction (R) with respect to the axis of rotation (D) and which is capable of being guided at least locally into the liquid medium.