Adjustable width steam box for fabric processing and method of using the same

A variable discharge steam box for use in the processing of fabric webs of variable width, which comprises

• an enclosed housing having an axis and an axial length sufficient to extend transversely across a full width of a fabric web of a predetermined maximum fabric width,
• a plurality of partition elements dividing said steam box axially into a central chamber and a plurality of additional chambers on opposite axial sides of said central chamber,
• said housing having a fabric-facing wall and said fabric-facing wall having steam outlet openings associated with each of said chambers for the discharge of steam onto a fabric web moving adjacent to said fabric-facing wall,
• a steam duct extending axially through said enclosed housing and having portions thereof within each of said chambers,
• said steam duct having at least one steam outlet orifice in each of said chambers,
• a steam inlet in a central portion of said steam duct to introduce steam under pressure into said central portion for flow axially outward within said steam duct toward opposite ends thereof,
• controllable valve elements in said steam duct operative to block said steam duct at multiple axial positions therein to controllably limit the flow of steam within said steam duct axially outward from said central portion thereof, to controllably limit the effective width of steam discharge from said steam box,
• said controllable valve elements comprising axially movable valve pistons positioned within said steam duct and controllably axially movable therein to increase or decrease the length of said steam duct receiving steam from said steam inlet.