Pressure-controlled steam oven for asymptotic temperature control of continuous feed media

A vapor fuser apparatus for fusing a toner material to a substrate in a xerographic system, the vapor fuser apparatus comprising:

• a vapor oven defining a gas-tight pressure chamber and having sealed entry and exit ports for transferring said substrate through the pressure chamber;
• and
• means for controlling an internal pressure inside said pressure chamber such that a saturation temperature of heat transfer fluid disposed inside the pressure chamber is adjusted to a predetermined temperature, wherein said internal pressure inside said pressure chamber is different from an atmospheric pressure external to said vapor oven.

A method for fusing a toner material onto a substrate in a xerographic system, the method comprising:

• generating temperature and pressure conditions inside a pressure chamber containing a heat transfer fluid such that an internal pressure of heat transfer vapor in said pressure chamber is different from an atmospheric pressure external to said pressure chamber, and such that an internal temperature of said pressure chamber is equal to or greater than a boiling point temperature of said heat transfer fluid at said pressure conditions, and
• transferring said substrate with un-fused toner material disposed thereon through said pressure chamber without significantly changing a pressure differential between said internal pressure and said atmospheric pressure, whereby said substrate is heated to said internal temperature and said toner material is fused to said substrate.