Infra-red heaters

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish and having an upper surface and two generally concave depressions extending below said surface;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• two infra-red lamps each extending across the base layer above one of said depressions;
• said lamps having filaments which together have a first electrical resistance when the lamps are at ambient temperature and a second electrical resistance higher than said first resistance when the lamps are at operating temperature;
• a ballast device comprising a coil of electrical resistance wire extending around said heater adjacent said peripheral wall;
• means coupling said ballast device in series with said infra-red lamps;
• said ballast device having an electrical resistance at least half said second electrical resistance of said filaments, whereby said ballast device limits inrush current upon energization of said lamps when said filaments are in their first electrical resistance condition;
• and
• a thermal cutout device connected to said lamps for controlling energization thereof in accordance with temperature.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• two infra-red lamps each extending across the base layer, said lamps having filaments which together have first electrical resistance when the lamps are at ambient temperature and a second electrical resistance higher than said first resistance when the lamps are at operating temperature;
• a ballast device comprising a coil of electrical resistance wire extending around said heater adjacent said peripheral wall;
• means coupling said ballast device in series with said infra-red lamps for supply of electrical power to said infra-red lamps solely by way of said ballast device when said filaments are in their first electrical resistance condition;
• said ballast device having an electrical resistance providing limitation of inrush current upon energization of said lamps when said filaments are in their first electrical resistance condition;
• and
• a thermal cutout device connected to said lamps for controlling energization thereof via said ballast device in accordance with temperature.

The infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish and having an upper surface and at least one generally concave depression extending below said surface;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means which comprises at least one infra-red lamp extending over the base layer above said depression and which has filament means having a first electrical resistance at ambient temperature and a second electrical resistance higher than said first resistance at operating temperature;
• a ballast device comprising a coil of electrical resistance wire extending over said base layer in a generally circular configuration;
• means coupling said ballast device in series with said infra-red source means;
• said ballast device having an electrical resistance approximately half said second electrical resistance of said filament means, whereby said ballast device provides limitations of inrush current upon energization of said infra-red source means when said filament means is in its first electrical resistance condition;
• and
• a thermal output device connected to said infra-red source means for controlling energization thereof in accordance with temperature.

The infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish and having an upper surface and at least one generally concave depression extending below said surface;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means which comprises at least one infra-red lamp extending over the base layer above said depression and which has filament means having a first electrical resistance at ambient temperature and a second electrical resistance higher than said first resistance at operating temperature;
• a ballast device comprising a coil of electrical resistance wire extending over said base layer in a generally circular configuration;
• means coupling said ballast device in series with said infra-red source means;
• said ballast device having an electrical resistance at least half said second electrical resistance of said filament means, whereby said ballast device provides limitation of inrush current upon energization of said infra-red source means when said filament means is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said infra-red source means for controlling energization thereof in accordance with temperature.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means extending over the base layer and including filament means which has a first electrical resistance at ambient temperature and a second electrical resistance higher than said first resistance at operating temperature;
• a ballast device comprising a coil of electrical resistance wire;
• a means coupling said ballast device in series with said infra-red source means;
• said ballast device having an electrical resistance approximately half said second electrical resistance of said filament means, whereby said ballast device provides limitation of inrush current upon energization of said infra-red source means when said filament means is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said infra-red source means for controlling energization thereof in accordance with temperature.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of microporous thermal insulating material supported in the dish;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means extending over the base layer and including filament means which has a first electrical resistance higher than said first resistance at operating temperature;
• a ballast device comprising a coil of electrical resistance wire;
• means coupling said ballast device in series with said infra-red source means;
• said ballast device having an electrical resistance at least half said second electrical resistance of said filament means, whereby said ballast device provides limitation of inrush current upon energization of said infra-red source means when said filament means is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said infra-red source means for controlling energization thereof in accordance with temperature.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of thermal insulating material supported in the dish;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means extending across the base layer and having filament means which has a first electrical resistance when the source means is at ambient temperature and a second electrical resistance higher than said first temperature when the source means is at operating temperature;
• a ballast device;
• manually-operable control means for connection to a source of electric power and having a first setting for supplying power at a first level and a second setting for supplying power at a second level, said first level being lower than said second level;
• means co-operable with said control means to supply power at said first setting to said source means via said ballast device;
• said ballast device having an electrical resistance providing limitations of inrush current upon energization of said source means when said filament means is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said source means for controlling energization thereof in accordance wit temperature.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of thermal insulating material supported in the dish;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• infra-red source means extending across the base layer and having filament means which has a first electrical resistance when the source means is at ambient temperature and a second electrical resistance higher than said first resistance when the source means is at operating temperature;
• a ballast device electrically connected in series with said source means;
• said ballast device having an electrical resistance at least half said second electrical resistance of said filament means, whereby said ballast device provides limitation of inrush current upon energization of said source means when said filament means is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said source means for controlling energization thereof.

An infra-red heater for a glass ceramic top cooker, which heater comprises:

• a dish;
• a base layer of thermal insulating material supported in the dish and having at least one generally concave depression having at least in part a width greater than twice its depth;
• a peripheral wall of thermal insulating material extending around the periphery of the base layer;
• at least one infra-red lamp extending across the base layer above said depression and including a filament which has a first electrical resistance when the lamp is at ambient temperature and a second electrical resistance when the lamp is at operating temperature;
• a ballast device electrically connected in series with said at least one lamp;
• said ballast device having an electrical resistance providing limitation of inrush current upon energization of said at least one lamp when said filament is in its first electrical resistance condition;
• and
• a thermal cutout device connected to said at least one lamp for controlling energization thereof.