A heater unit and control circuitry therefor, the heater unit typically being employed as a preheater or primary heater for the installation and removal of electronic components from a PCB or the like and having various means for accommodating (a) an uneven surface or the presence of other components on the underside of the board or (b) an unlevel board. Moreover, a heater unit for sequentially providing preheat and primary heat from different zones of the heater is disclosed. A probe for use with the heater for sensing the temperature at various points on the board is also disclosed. The circuitry is characterized by ease of calibration of the heater temperature, the temperature transducing circuits, and the temperature setting circuits thereof. Moreover, circuitry is provided to insure the same voltage out of each input source in response to the input source measuring or setting a common temperature.

The invention concerns an appliance for heating up and keeping warm of food or beverages comprising at least one food container and one heating element and is easy to operate and to clean as well as allowing an even heating up of food, containing an electrical temperature control preventing overheating.

An electrically heated wok having a bowl of substantial thickness preferably formed from aluminium by gravity or sand casting and having an electrical heating element on the underside thereof, the bowl being supported on an annular skirt surrounding the heating element, the bowl being tiltable in relation to the skirt and being guided by a guide member associated with the skirt and with which portions of the bowl interact, a locking lever being provided for engagement with detents on the skirt so that the bowl can be fixed in a number of predetermined tilted positions in relation to the skirt.

Electrically heated cooking pans usually have a number of supporting legs, each of which is fixed individually to the underside of the pan. The assembly of such items is expensive and time-consuming and in addition failure of one leg can result in the whole device becoming useless and if failure occurs during cooking can be dangerous. According to the invention, a circular stand is used which replaces individual legs and only a single central fixing point is required for the ciruclar stand. Normally, the device will have its own electrical heater permanently secured to the base of the pan and this will have a metal cover to enclose the heater. The circular stand will normally be of synthetic plastics material and secured to the cover. The cover in turn can then be secured by a single central screw to the under side of the pan.

A combination of a bottom of a pan and a heating device comprises a pan, an aluminum alloy plate and an electric heating member welded to a bottom of the pan by means of instantaneous welding, a thermostatic circuit fixed to the bottom of the pan for keeping the pan at a constant temperature when energized, a mounting plate integrally formed with the aluminum alloy plate, and a temperature-control switch fixed to the mounting plate. A switch is mounted to a rear of the temperature-control switch to thereby switch the temperature-control switch between the electric heating member and the thermostatic circuit. An activating member is operably connected to the switch in a manner that the electric heating member is turned on when the activating member is manually activated and that the electric heating member is turned off and the thermostatic circuit is energized when a food in the pan is well cooked or heated to a predetermined temperature.