Oven: Insulated Electric Oven with Plug-In Grid Heaters and a Thermostat (Ogden, US 987,161, 1911)

An electric oven built to waste as little heat as possible: a double-walled, packed box with a packed door that seals like a strong-room door. Grid-shaped heating elements slide into grooves in the walls and plug into sockets at the back, and the food rests on them. A thermostat cuts the current when the set temperature is reached and switches it on again as the oven cools. Result: an oven that bakes, roasts or dries at a set temperature with any number of heating grids. Source: G. J. Ogden, US 987,161 (1911). Unknown: sizes, metals, packing and temperatures. Picture: the patent drawing.