The Naxon Utilities Corporation of Chicago developed the Naxon Beanery All-PurposeCooker. The Rival Company bought Naxon in 1970, and reintroduced it under the Crock-Pot name in 1971. In 1974, Rival introduced removable stoneware inserts. The brand now belongs to Sunbeam Products, a subsidiary of Jarden Corporation. While Crock-Pot still dominates the market in the USA, Hamilton Beach, West Bend Housewares and other companies have also introduced similar slow cookers.
A slow cooker consists of a lidded round or oval cooking pot made of glazed ceramic or porcelain, surrounded by a housing, usually metal, containing a thermostatically controlled electric heating element. The lid is often transparent glass and is seated in a groove in the pot edge; condensed vapour collects in that groove and provides a low-pressure seal to the atmosphere. Pressure inside a working crock pot is therefore effectively at atmospheric pressure, despite the water vapor generated inside the pot. A crock pot therefore is substantially different from a pressure cooker and presents no danger of an abrupt (perhaps explosive) pressure release.
The ceramic pot, or a 'crock', acts as both a cooking container and a heat reservoir. Many slow cookers have two or more temperature settings (e.g., low, medium, high, and sometimes a "keep warm" setting). A typical slow cooker is designed to heat food to 170°F (77°C) on low, to perhaps 190-200°F (88-93°C) on high.Click here for some Crock-Pots.