When injection molding large plate-shaped elastomer parts, the molded part is released from the mold by blowing compressed air underneath it. The cylinder used for this purpose keeps the air supply opening closed against the spray pressure during the spraying process. To blow out the air, the cylinder is retracted, exposing an internal cross-section for blowing air through. As the cylinder end is adapted to the geometry of the injection mold, the cylinder is secured against twisting to ensure correct contour coverage at all times.