Ceramic-top cooking assembly fracture detector

Claim 2

In an infrared radiant cooking assembly, the combination of an upper utensil-supporting cover plate of infrared-transmissive frangible glass-ceramic material having a predetermined planar extent, a heater block supporting a resistance element in spaced relation from the undersurface of said cover plate, a circuit for energizing said resistance element across a pair of lines from an AC power source, said cover plate having an electrically conductive stripe incorporated thereon, said conductive stripe being electrically connected in said circuit, thermal fuse means in said circuit connected in each of said lines between said power source and said resistance element, a pair of heaters serially connected in one line of said AC power source such that each of said heaters is in thermal transfer relation with one of said fuse means, AC switching means connected in said circuit, said AC switching means comprising a symmetrical controlled rectifier having two main electrodes and a control electrode together with a series-connected resistor-capacitor network connected across one of said main electrodes and said control electrode, said conductive strip having one end connected to the junction of the capacitor and resistor of said network and its other end connected to the other of said main electrodes whereby said conductive stripe is connected in parallel with said AC switching means, said one main terminal of said symmetrical controlled rectifier being connected to said power source via said serially connected heaters, said capacitor of said network offering high impedance to the flow of current through said heaters, said resistor-capacitor network operative in thE event that an open circuit occurs in said conductive stripe to provide capacitive reactance phase shifting of the current flow to said control electrode to permit a reduced value of current flow to said control electrode to render said symmetrical controlled rectifier conductive, said symmetrical controlled rectifier upon being rendered conductive permitting increased current to pass to each of said heaters to fuse their associated thermal fuse means and thereby remove said cooking assembly from both lines of said power source.

Claim 3

In an infrared radiant cooking assembly, the combination of an upper utensil-supporting cover plate of infrared-transmissive frangible glass-ceramic material having a predetermined planar extent, a heater block supporting a resistance element in spaced relation from the undersurface of said cover plate, a circuit for energizing said resistance element across first and second AC power lines and a neutral line, said cover plate having an electrically conductive stripe incorporated thereon, said stripe being electrically connected in said circuit, thermal fuse means in said circuit, said fuse means comprising a first thermal fuse connected in said first powerline and a second thermal fuse connected in said second powerline, said fuse heater means comprising first and second resistance heaters connected in series in said first powerline in thermal transfer relation, respectively, with said first and second thermal fuses, AC switching means connected in parallel with said conductive stripe, said AC switching means comprising a symmetrical controlled rectifier having first and second current-carrying main electrodes and a control electrode, a series-connected resistor-capacitor network connected across said first main electrode and said control electrode, the capacitor of said network connected serially between one terminal of said conductive stripe and said first main electrode, the second terminal of said conductive stripe connected to said neutral line, the resistor of said network connected serially between said one terminal of said conductive stripe and said control electrode, said first main electrode connected in series with said first powerline via said second resistance heater and thence via said first resistance heater, said capacitor allowing a limited current flow through said first and second resistance heaters and said conductive stripe during normal operation of said cooking assembly, said control electrode rendering said symmetrical controlled rectifier conductive in the event of an open circuit in said conductive stripe thereby permitting increased current flow to said first and second heaters to fuse their associated first and second fuses, said second heater having greater resistance than said first heater whereby said second heater fuses said second powerline fuse before said first heater fuses said first powerline fuse to insure sufficient energization of said heaters such that both said fuses are fused.

Claim 4

In an infrared radiant cooking assembly, the combination of an upper utensil-supporting cover plate of infrared-transmissive frangible glass-ceramic material having a predetermined planar extent, a heater block supporting a resistance element in spaced relation from the undersurface of said cover plate, a circuit for energizing said resistance element across first and second AC power lines and a neutral line, said cover plate having an electrically conductive stripe incorporated thereon, said stripe being electrically connected in said circuit, thermal fuse means in said circuit, said fuse means comprising a first thermal fuse connected in said first powerline and a second thermal fuse connected in said second powerline, said fuse heater means comprising first and second resistance heaters connected in series in said first powerline in thermal transfer relation, respectively, with said first and second thermal fuses, AC switching means connected in parallel with said conductive stripe, said AC switching means comprising a symmetrical controlled rectifier having first and second current-carrying main electrodes and a control electrode, a series-connected resistor-capacitor network connected across said first main electrode and said control electrode, the capacitor of said network connected serially between one terminal of said conductive stripe and said first main electrode, the second terminal of said conductive stripe connected to said neutral line, the resistor of said network connected serially between said one terminal of said conductive stripe and said control electrode, said first main electrode connected in series with said first powerline via said second resistance heater and thence via said first resistance heater, said capacitor allowing a limited current flow through said first and second resistance heaters and said conductive stripe during normal operation of said cooking assembly, said control electrode rendering said symmetrical controlled rectifier conductive in the event of an open circuit in said conductive stripe thereby permitting increased current flow to said first and second heaters to fuse their associated first and second fuses, said second heater having greater resistance than said first heater whereby said second heater fuses said second powerline fuse before said first heater fuses said first powerline fuse to insure sufficient energization of said heaters such that both said fuses are fused.

Claim 5

In an infrared radiant cooking assembly for mounting in a range top or the like having an opening therein, said assembly comprising a frangible cover plate of infrared-transmissive glass-ceramic material including an upper utensil-supporting surface, said cover plate positioned in said opening whereby a continuous gap is defined between the edges of said cover plate and said opening, a lower housing positioned below said cover plate having a bottom wall, end walls and sidewalls defining a boxlike receptacle, at least one radiant heating unit supported in said housing, said heating unit including a fibrous-ceramic heater block having a substantially planar raised peripheral face defining a central recessed area, said recessed area supporting an infrared-emissive uninsulated electrical resistance element thereon in spaced relation below the undersurface of said cover plate, a circuit for energizing said resistance element across first and second powerlines, continuous-pressure clamping means positioned in said gap for Retaining said cover plate and said housing in said range opening, said cover plate having an electrically conductive continuous stripe positioned on the undersurface thereof, said stripe paralleling the edges of said cover plate and having a pair of terminal end portions located adjacent one edge of said cover plate, a terminal board spaced from the undersurface of said cover plate having a pair of spaced terminals therein whereby each said terminal electrically contacts one of said conductive stripe terminal end portions, said continuous-pressure clamping means operative with said terminal board to maintain said pair of spaced terminals in electrical contact with said conductive stripe terminal ends, first and second thermal fuses connected in said first and second power lines respectively, fuse heater means in said circuit in thermal transfer relation with said first and second fuses, said fuse heater means comprising first and second resistance heaters connected in series in said first powerline in thermal transfer relation, respectively, with said first and second thermal fuses, AC switching means connected in parallel with said conductive stripe, said AC switching means comprising a symmetrical controlled rectifier having first and second current-carrying main electrodes and a control electrode, a series-connected resistor-capacitor network connected across said first main electrode and said control electrode, the capacitor of said network connected serially between one terminal of said conductive stripe and said first main electrode, the second terminal of said conductive stripe connected to said neutral line, the resistor of said network connected serially between said one terminal of said conductive stripe and said control electrode, said first main electrode connected in series with said first powerline via said second resistance heater and thence via said first resistance heater, said capacitor allowing a limited current flow through said first and second resistance heaters and said conductive stripe during normal operation of said cooking assembly, said control electrode rendering said symmetrical controlled rectifier conductive in the event of an open circuit in said conductive stripe thereby permitting increased current flow to said first and second heaters to fuse their associated first and second fuses, said second heater having greater resistance than said first heater whereby said second heater fuses said second powerline fuse before said first heater fuses said first powerline fuse to insure sufficient energization of said heaters such that both said fuses are fused.

Claim 6

In an infrared radiant cooking assembly for mounting in a range top or the like having an opening therein, said assembly comprising a frangible cover plate of infrared-transmissive glass-ceramic material including an upper utensil-supporting surface, said cover plate positioned in said opening whereby a continuous gap is defined between the edges of said cover plate and said opening, a lower housing positioned below said cover plate having a bottom wall, end walls and sidewalls defining a boxlike receptacle, at least one radiant heating unit supported in said housing, said heating unit including a fibrous-ceramic heater block having a substantially planar raised peripheral face defining a central recessed area, said recessed area supporting an infrared-emissive uninsulated electrical resistance element thereon in spaced relation below the undersurface of said cover plate, a circuit for energizing said resistance element across first and second powerlines, continuous-pressure clamping means positioned in said gap for Retaining said cover plate and said housing in said range opening, said cover plate having an electrically conductive continuous stripe positioned on the undersurface thereof, said stripe paralleling the edges of said cover plate and having a pair of terminal end portions located adjacent one edge of said cover plate, a terminal board spaced from the undersurface of said cover plate having a pair of spaced terminals therein whereby each said terminal electrically contacts one of said conductive stripe terminal end portions, said continuous-pressure clamping means operative with said terminal board to maintain said pair of spaced terminals in electrical contact with said conductive stripe terminal ends, first and second thermal fuses connected in said first and second power lines respectively, fuse heater means in said circuit in thermal transfer relation with said first and second fuses, said fuse heater means comprising first and second resistance heaters connected in series in said first powerline in thermal transfer relation, respectively, with said first and second thermal fuses, AC switching means connected in parallel with said conductive stripe, said AC switching means comprising a symmetrical controlled rectifier having first and second current-carrying main electrodes and a control electrode, a series-connected resistor-capacitor network connected across said first main electrode and said control electrode, the capacitor of said network connected serially between one terminal of said conductive stripe and said first main electrode, the second terminal of said conductive stripe connected to said neutral line, the resistor of said network connected serially between said one terminal of said conductive stripe and said control electrode, said first main electrode connected in series with said first powerline via said second resistance heater and thence via said first resistance heater, said capacitor allowing a limited current flow through said first and second resistance heaters and said conductive stripe during normal operation of said cooking assembly, said control electrode rendering said symmetrical controlled rectifier conductive in the event of an open circuit in said conductive stripe thereby permitting increased current flow to said first and second heaters to fuse their associated first and second fuses, said second heater having greater resistance than said first heater whereby said second heater fuses said second powerline fuse before said first heater fuses said first powerline fuse to insure sufficient energization of said heaters such that both said fuses are fused.