Sealing head for machines for heat treating threads

A control process for a heat treatment machine for heat treating threads, the heat treatment machine comprising at least one sealing head provided with balloon or bellows type actuators without pistons that move the heat treatment machine between an open position and a closed position, the control process comprising:

• positioning an upper horizontal sealing roller and a lower horizontal sealing roller with respect to opposite faces of a conveyor belt;
• aligning the horizontal sealing rollers using vertical seals adjacent ends of the upper and lower horizontal sealing rollers, wherein aligning the horizontal sealing rollers comprises performing a series of pressurizations and de-pressurizations of at least one balloon or bellows type actuator of a third set of balloon or bellows type actuators;
• actuating a first set of the balloon or bellows type actuators to place the upper and lower horizontal sealing rollers under pressure against the opposite faces of the conveyor belt;
• actuating a second set of the balloon or bellows type actuators to apply thin sealing sheets of horizontal seals, under pressure, to the upper and lower horizontal sealing rollers;
• actuating the third set of the balloon or bellows type actuators to apply the vertical seals, under pressure, against the ends of the upper and lower horizontal sealing rollers;
• providing authorization to pressurize a treatment chamber upon closing a plurality of drain valves associated with the first, second, and third sets of balloon or bellows type actuators while opening a plurality of regulating valves that control the first, second, and third sets of balloon or bellows type actuators;
• and
• successively depressurizing the third, second, and first sets of balloon or bellows type actuators to return the heat treatment machine to the open position before a new treatment cycle.