Web dryer with control of air infiltration.

A unique nozzle assembly (11, 12) is provided for placement within the chamber (4) of a web dryer (1) and closely adjacent a housing web slot (5, 6). The nozzle assembly generally comprises a Coanda-type nozzle (27) and a supplemental nozzle (33) disposed on the assembly so that it is positioned between the Coanda nozzle and the housing wall (3). Both the Coanda and supplemental nozzles are supplied with air from a common manifold (13) connected to an external air source. An air flow control device (34, 35) is provided for the individual air flow paths in the assembly to suitably balance the velocities of the two discharging air jets. To prevent any transient air currents inside the dryer chamber from causing web or air flow instability, a seal (43) is provided between the improved nozzle and the dryer housing wall. The seal is disposed along the head end of the nozzle; that is, closely adjacent the nozzle jet discharge ports. A pair of improved nozzles are usually disposed adjacent each housing web slot, one on each side of the web. The exact relative positioning of the nozzles in a pair may be varied according to the particular conditions encountered. To overcome any problems caused by narrow webs or a slight amount of cool room air infiltrating the warmer dryer environment, a labyrinth of expansion chambers (66) may be positioned between the inner dryer wall (3) adjacent the slots and the improved nozzles (58, 65) as per FIG. 7. In the present embodiment, the labyrinth forms part of the nozzle assemblies (44) themselves.