Method and apparatus for producing a web of extensible fibrous material

A method of treating a web of extensible fibrous material to increase extensibility in multiple directions, comprising:

• passing a web of the extensible fibrous material through a passage between a cylinder of rigid material having, on a side surface, a plurality of incisions running circumferentially, and a pressing web having an outer layer of elastically compressible material kept locally pressed, at a pressing area, against the side surface of said cylinder, said pressing web being longitudinally inextensible at least on a side that is not facing said cylinder, peripheral speeds of said cylinder and of said pressing web in said pressing area being substantially equal;
• pressing the web of the extensible fibrous material to cause the extensible fibrous material to accumulate inside the incisions;
• and
• causing said pressing web to adhere to said cylinder over a portion located downstream of said pressing area, said pressing web assuming, downstream of said pressing area, a concavity opposite to a concavity assumed by said pressing web upstream of said pressing area.