melt blowing head 1 comprises an inlet 2 for the polymeric material to be melt blown a polymeric material delivery or distributing channel 3 a filter 4 a melt blowing die 5 as well as channels 6 for supplying hot air at the outlet of the holes 7 of the melt blowing die 5 a plurality of fibrils 8 will be obtained by spraying as clearly shown in fig2 the above mentioned polymeric material delivery channel 3 is widened in the form of a narrow chamber 9 in which the polymeric mass supplied to a pre die or filter 4 and then to the die 5 is expanded thus the path of the polymeric material from the inlet 2 to the die holes 7 would be a random and uncontrolled path then it should be apparent that this lacking of properly controlling the supplying of the polymeric material from the inlet 2 to the die 5 holes 7 would generate variations in the flow of the polymeric material due to the different holding time in which said polymeric material is held in the chamber 9 accordingly the polymeric material will be subjected to an uncontrolled thermal processing very different from that would be necessary and desired moreover the above mentioned different time and temperature would generate a degradation of the polymeric material which will have a different melt index or fluidity and a different flow rate through the melt blowing die thus fibrils will be generated having different chemical physical characteristics for example length cross sections consistency and so on which would provide an end product for example a non woven fabric with dishomogeneous properties such as toughness felting thickness and so on the.