Method and apparatus for heat treating webs

Apparatus for heat-treating webs, including a cylinder mounted for rotation about a horizontal axis, having an outer web-engaging surface and an inner prominently heat-absorbing surface, and a stationary structure within the cylinder comprising a complement of IR burners that includes at least one IR burner, said complement of IR burners having combustion area confronting but spaced freon said inner heat-absorbing surface, the combustion area being incandescent when in operation, said complement of IR burners extending essentially from end-to-end of said cylinder and confronting only a cylindrical segment of said heat-absorbing surface, an elongated exhaust duct at the top of said cylinder but separated from said heat-absorbing surface by exhaust duct clearance space, said exhaust duct extending along and within said cylinder and being formed for admitting exhaust gas from said exhaust duct clearance space, and shielding means coacting with said heat-absorbing surface to guide hot exhaust gas from said complement of IR burners to said exhaust duct, said shielding means acting with said complement of IR burners and said exhaust duct for providing heat protection for the stationary structure within the cylinder.

A method of heat-treating a web that traverses a path partway around and in contact with a heated rotating cylinder, wherein the cylinder is heated by an internal stationary complement of IR burners extending end-to-end in the cylinder and whose extent around the cylinder is limited to have a predetermined limited capacity of delivering heat to the web via the cylinder when the rate of supply of air-fuel mixture to the IR burner complement is at least near maximum, i.e., flame lift-off rate, said method including the steps of rotating the cylinder at a routine maximum rate for thereby heat-treating the web at a routine maximum rate while the cylinder is contacted by the web and while the complement of IR burners is being supplied with air-fuel mixture at least near said maximum rate, and reducing the speed of the web and of cylinder rotation while progressively reducing the rate of air-fuel mixture supply to the complement of IR burners through a turn-down range from said at-least near maximum rate to the minimum rate that supports combustion.

A method of producing a cylinder for imparting heat to a web, including the steps of mounting an IR burner complement stationary within a rotary cylinder and extending in confrontation with the inner surface of the cylinder from end-to-end thereof, the IR burner complement being of the type that characteristically emits radiant heat when in operation and whose maximum rate of heat emission is limited by the maximum rate of supply of air-fuel mixture that sustains operation without flame lift-off, and establishing the combustion area of the IR burner complement at substantially less than said inner area of the cylinder in accordance with the rate of heat to be imparted to the web when the cylinder is in full-speed operation and when the IR burner complement is operating at least near its maximum supply rate.