An apertured shield is disclosed having spring tongues, pointing radially inwards, each of the tongues having two lateral limiting edges and a longitudinal extent terminating in an irregular edge all of which edges define together an aperture. Adjacent spring tongues are overlapped in an area on the limiting edges, and are connected together at the circumference of the shield by being flanged into a retainer ring. The apertured shield is disposed in close proximity to the injection valve to cause a turbulence with superimposed spin flow of the medium flowing into the combustion chamber of an internal combustion engine.