is arranged between the top face of the heating sole plate 2 and a sheet metal wall 6b the heating sole plate 2 is traversed by steam distribution ducts not shown in the drawings through which the vaporization chamber 3 communicates with the exterior beneath the sole plate 2 the casing 1 contains a water reservoir 4 the bottom sheet metal wall 6a of which is located above the top wall 6b of the chamber 3 there is formed between the walls 6a and 6b a hollow space 6c the function of which is to prevent overheating of the water and formation of steam within the reservoir 4 the walls 6a and 6b are substantially horizontal in the service position of the iron in which the sole plate 2 itself is horizontal an opening 7 extends through the walls 6a and 6b the nozzle 8 of a water injection device 9 being mounted within said opening by means of this injection device the water contained in the reservoir 4 is selectively fed drop by drop into the vaporization chamber 3 under the action of gravity the nozzle 8 comprises a tubular body 11 and the annular end portion of said body which is directed towards the reservoir 4 has an annular flange 12 which is applied around the opening 7 and beneath the bottom sheet metal wall 6a which is adjacent to the reservoir 4 the bottom wall 6a is in turn provided around the opening 7 with a cylindrical collar 13 which is fitted within the body 11 a metallic tube 14.