Method for forming webs of transversely extensible fibrous material, in particular paper webs, and apparatus for implementing the method

A method for forming a web of transversely extensible fibrous material comprising:

• subjecting a fluid-permeable endless conveyor belt of elastic material, said conveyor belt having a thickness increasing from a longitudinal axis thereof to edges thereof, to at least one localized transverse stretching operation, achieved by temporarily withdrawing at least one longitudinal band of said conveyor belt from a surface on which said conveyor belt slides and maintaining said conveyor belt in contact, in this stretched condition, with at least a part of a surface of at least one support member;
• depositing a web of pliable fibrous material having a liquid content between 3% and 70% by weight against that portion of said conveyor belt of elastic material which has been transversely stretched;
• by effect of vacuum, maintaining said web of pliable fibrous material adhering to said conveyor belt of elastic material during a return thereof to an original configuration thereof, such to cause a transverse contraction of said web and a simultaneous partial removal of liquid therefrom;
• using as said endless conveyor belt a sleeve of elastic material mounted on a support roller having an axial length less than an axial length of said sleeve, which is fixed at ends thereof to external prolongations of a rotational shaft of said roller, and
• causing transverse stretching of said sleeve of elastic material with a pair of presser rollers which have axes parallel to an axis of said support roller and a distance apart greater than the axial length thereof, and are made to translate perpendicular to said axis such as to cause those portions of said sleeve projecting beyond said roller to approach the axis thereof.

An apparatus for producing a transversely extensible fibrous material web from a web of pliable fibrous material having a water content between 3% and 70%, comprising:

• a fluid-permeable endless conveyor belt of elastic material, of thickness increasing from a longitudinal axis of said endless conveyor belt to edges of said endless conveyor belt;
• a first system causing a localized transverse stretching of said endless conveyor belt following withdrawal of at least one longitudinal band thereof from a surface on which it said endless conveyor belt slides, and maintaining said endless conveyor belt adhering, in this stretched condition, to at least a part of a surface of at least one support member;
• a second system depositing said web of pliable fibrous material on the transversely stretched portion of said endless conveyor belt;
• and
• at least one fixed vacuum source acting through said endless conveyor belt to maintain said web of pliable fibrous material adhering to said endless conveyor belt during an elastic return of said endless conveyor belt to an original configuration thereof, such to cause in this manner a transverse contraction of said web of pliable fibrous material and a simultaneous partial removal of liquid therefrom,
• wherein the endless conveyor belt consists of a sleeve, the support member consisting of a roller of substantially rigid material having a lateral surface that is perforated and wrapped by said sleeve, and wherein said roller is provided with at least one circumferential groove to be covered by said sleeve after fixing said sleeve at both ends thereof to ends of said roller.