Electric blanket heating control with capacitance sensing
First Claim
1. An electric blanket control for use with a blanket having an electrical heating circuit that includes an electrical resistance wire array in an expanse of blanket, the control effective to deactivate power to the heating circuit when the blanket is unattended, said control comprising means for applying electric power to said resistance wire array to generate heat in said expanse of blanket, a capacitance detector for said heating circuit, said capacitance detector being arranged for connection to said resistance wire array and constructed and adapted to respond to differences in the capacitance of the heating circuit attributable to the presence or absence of the user under the heating wire of the blanket, and switch means responsive to said capacitance detector adapted to interrupt power flow to said heating circuit when the capacitance value of the heating circuit indicates the absence of the user under the heating wire of the blanket.
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Accused Products
Abstract
An electric blanket control effective to deactivate power to the blanket'"'"'s resistance wire heating circuit, the control having a capacitance detector constructed and adapted to respond to differences in the capacitance of the heating circuit attributable to the presence or absence of the user under the heating wire of the blanket, and a switch responsive to the detector adapted to interrupt power to the heating circuit when the capacitance value of the heating circuit indicates the absence of the user.
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Citations
17 Claims
- 1. An electric blanket control for use with a blanket having an electrical heating circuit that includes an electrical resistance wire array in an expanse of blanket, the control effective to deactivate power to the heating circuit when the blanket is unattended, said control comprising means for applying electric power to said resistance wire array to generate heat in said expanse of blanket, a capacitance detector for said heating circuit, said capacitance detector being arranged for connection to said resistance wire array and constructed and adapted to respond to differences in the capacitance of the heating circuit attributable to the presence or absence of the user under the heating wire of the blanket, and switch means responsive to said capacitance detector adapted to interrupt power flow to said heating circuit when the capacitance value of the heating circuit indicates the absence of the user under the heating wire of the blanket.
- 15. In combination, an electric blanket and control therefor, said blanket having an electrical heating circuit that includes an electrical resistance wire array in an expanse of blanket, means for connecting said resistance wire array to a power source, means connected in circuit between said power source connecting means and said resistance wire array for interrupting current to said heating circuit when said circuit is grounded, said control effective to deactivate power to the heating circuit when the blanket is unattended, said control comprising a capacitance detector connected to said resistance wire array and responsive to differences in capacitance of the heating circuit attributable to the presence or absence of the user under the heating wire of the blanket, means to apply radio frequency current through said resistance wire array, means for sensing change in radio frequency current due to the absence of the user under the resistance wire array of said blanket, comprising a resistance-capacitance bridge formed in part by said resistance wire array, RF isolation means for isolating said resistance wire array from RF ground, and switch means responsive to said capacitance detector adapted to interrupt power flow to said heating circuit when the capacitance value of the heating circuit indicates the absence of the user under the heating wire of said blanket, said switch means being connected, upon activation, to draw current at a point in the circuit between said current interrupting means and said resistance wire array, said current draw being of sufficient size to cause said current interrupting means to terminate flow of current to said heating circuit.
Specification