An injection molding apparatus for manufacturing hollow objects, such as plastic e.g. multi-layered preforms, comprising an injection mold (1) with a front (2) and a rear side (3), which is composed of a clamp plate (4) on the front side (2), and a hot runner plate (5), where a manifold (6) is mounted in the hot runner plate, between which a set of injection nozzles (7) is arranged, which are each provided with a central supply duct (8), at the free end (9) whereof an injection gate (10) is provided. Said apparatus is remarkable in that said injection gate (10) is closable by means of a locking rod (11), which is movable herein to and fro through a profiled inner part (12) which is received in a holder (13) around which a heating element (14) is provided into which a primary channel (15) opens for supplying the plastic base material to the injection gate (10). Each injection nozzle (7) is directly removable individually from the injection side (16) of the injection mold at the injection side thereof, and a respective secondary channel (17) is provided separately; and method therefor.