Look a little closer
See the mechanism
Water enters a hot chamber before steam leaves
Read the diagram steps
Feed shut. The valve blocks new water. The heater and chamber may still be hot; closing the feed is not instant cooling.
Feed open. Water falls through the feed valve into the heated chamber. Steam follows a separate gallery to the soleplate holes.
Original functional schematic; dimensions and motion are exaggerated, not measured. Gravity-fed flash-steam example; the reservoir is not shown boiling.
Diagram basis: US2499185A: heater, feed valve and steam route.
The valve feeds water to a heated chamber
In the gravity-fed design described in General Electric's patent, the reservoir sits above the steam chamber. Opening a needle valve lets water descend through a passage. Changing the opening changes the water supply.
A resistance heater is embedded in the soleplate. It supplies heat to the pressing surface and the steam-generating chamber. The water route ends at that hot chamber; a separate steam route leads toward the fabric.
The holes are exits
Steam travels through internal passages before leaving through ports in the soleplate. Closing the water valve blocks new water from reaching the chamber. That does not instantly remove the water or heat already there, so it is not an instantaneous steam-off switch.
The thing to remember
The feed valve admits water; the hot chamber vaporizes it; internal passages send steam to the soleplate holes.
What this example leaves out
This is a gravity-fed flash-steam design. Irons with external steam generators use another supply arrangement.
Sources & further reading
Source access dates are listed below. Manufacturer descriptions and patents support the specific constructions described, not every product.
- Steam iron reservoir water supply and water discharge means (US2499185A) ↗
General Electric / Frank E. Finlayson · Retrieved 2026-10-18 · Gravity-fed water, needle valve, resistance-heated soleplate, steam chamber and outlet passages.
Read patent description: definitions for parts 2, 3, 10, 18, 48–51 and operation; claims 1–5. Selected historical flash-steam architecture, not proof of adoption in every modern iron.
