Heat setting machine with sealing head

A continuous heat set line for setting yarn, having spaced-apart, elongate, tubular entrance and exit cooling chambers interconnected by an elongate intermediate steam heat-setting chamber communicating therewith. The entrance and exit cooling chambers and the intermediate heat-setting chamber collectively define a single longitudinally-extending axis along the combined length thereof. Sealing heads seal the entrance and exit cooling chambers and the intermediate heat-setting chamber to a degree sufficient to maintain a pressurized condition within the heat-setting chamber. A yarn conveyor extends through the pretreatment chamber for conveying the yarn through the entrance and exit cooling chambers and the heat-setting chamber. At least one piston and cylinder assembly moves sealing rolls into and out of position relative to each other, while independently-operating springs urge the rolls together sufficiently to effect a seal.