Method of and apparatus for thermally treating fiber yarns

In an apparatus (20) for continuous thermal treatment of a bundle or bundles of fibers (21) withdrawn from a stuffer box (22) in a continuous cake form corrugated in advance, said apparatus comprising:

• means (24) disposed downstream of the stuffer box (22) for wrapping the continuous cake of the fibers (21) with a breathable heat resistant fabric (25) to form a continuous belt-like shaped object (28) having a substantially uniform cross section throughout the length thereof;
• a heat-treatment chamber (23) disposed downstream of said wrapping means (24) and including a pair of parallel spaced perforated partition walls (31, 32) defining therebetween a guide channel (33) for the passage of the belt-like shaped object (29);
• means (42, 58) for supplying a heating medium into said heat-treatment chamber (23) to heat the fibers (21);
• and a pair of ducts (29, 30) extending outwardly from the opposite ends of said guide channel (33) of the heat-treatment chamber (23) for the passage therethrough of the belt-like shaped object (28), said ducts (29,30) having a cross section substantially the same as the cross section of the belt-like shaped object (28) to provide pressure seal for the purpose of limiting the quantity of flow of the heating medium out of the channel and preventing intrusion of the outside air into said heat-treatment chamber (33) and the first one of said ducts corresponding to the inlet duct (29) of said heat-treatment chamber (33), the improvement wherein said heat-treatment chamber (23) is separated by said guide channel (33) into high-pressure portion (34) and the low-pressure portion (35) disposed on opposite sides of said guide channel, said heating medium comprises one of non-condensable gas, superheated steam, and a mixture of said non-condensable gas and said superheated steam, passage means is disposed outside said heat-treatment chamber for recirculating the heating medium from said low-pressure portion (35) to said high-pressure portion (34) of said heat-treatment chamber (23), and pressurizing and heating means (40, 41) is disposed in said passage means for pressurizing and heating the heating medium before the heating medium is recirculated into said high-pressure portion (34).