Heating device having an optimized heating element of PTC thermistor material
First Claim
1. A heating device, comprising:
- (a) a disc-shaped heating element having first and second major heat surfaces with electrodes thereon, the element being comprised of positive temperature coefficient (PTC) thermistor material;
(b) network voltage means electrically connected to said electrodes for operating the heating element;
(c) said PTC thermistor material having a cut-off control property at a desired cut-off temperature;
(d) the heating element having a thickness from 0.5 to 2 mm when the network voltage is 220 volts;
(e) a specific electrical impedance of the heating element, at Curie temperature and 2000 volt/cm being between ρ
c= 1×
103 Ohm·
cm and 6×
103 Ohm·
cm;
(f) the heating element having a specific heat output of greater than 50 watts per cm2 of a cross-section of the disc-shaped element;
(g) the PTC thermistor material being selected to have a Curie temperature which is at least 50°
K. higher than the cut-off temperature; and
(h) means for providing a substantially even dissipation of heat from the first and second major surfaces of the heating element.
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Abstract
A heating device is disclosed having a disc-shaped heating element consisting of PTC thermistor material typically operated by a network voltage of 220 volts. The PTC thermistor material has a cut-off control property at a desired cut-off temperature so as to minimize further heat rises of the heating element above the cut-off temperature. In this fashion, the possibility of fire damage is reduced. The heating element has a specific heat output of greater than 50 watts per cm2 and the PTC thermistor material is selected to have a Curie temperature which is at least 50° K. higher than the cut-off temperature. A heating body is provided to affect a substantially even dissipation of heat from two sides of the heating element.
86 Citations
10 Claims
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1. A heating device, comprising:
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(a) a disc-shaped heating element having first and second major heat surfaces with electrodes thereon, the element being comprised of positive temperature coefficient (PTC) thermistor material; (b) network voltage means electrically connected to said electrodes for operating the heating element; (c) said PTC thermistor material having a cut-off control property at a desired cut-off temperature; (d) the heating element having a thickness from 0.5 to 2 mm when the network voltage is 220 volts; (e) a specific electrical impedance of the heating element, at Curie temperature and 2000 volt/cm being between ρ
c= 1×
103 Ohm·
cm and 6×
103 Ohm·
cm;(f) the heating element having a specific heat output of greater than 50 watts per cm2 of a cross-section of the disc-shaped element; (g) the PTC thermistor material being selected to have a Curie temperature which is at least 50°
K. higher than the cut-off temperature; and(h) means for providing a substantially even dissipation of heat from the first and second major surfaces of the heating element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A heating device, comprising:
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(a) a heating element with electrodes connected thereto having first and second major heat surfaces, the element being comprised of a positive temperature coefficient (PTC) thermistor material formed of ceramic on the basis of barium titinate, the PTC thermistor material having a sharp rise of specific impedance near the Curie temperature of the material; (b) network voltage means electrically connected to said electrodes for operating the heating element; (c) said PTC thermistor material having a cut-off control property at a desired cut-off temperature at which heating protection is desired; (d) the heating element having a thickness from 0.5 to 2 mm; (e) a specific electrical impedance of the heating element, at the Curie temperature being between ρ
c= 1×
103 Ohm·
cm and 6×
103 Ohm·
cm;(f) the heating element having a specific heat output of greater than 50 watts per cm2 of a cross-section of the disc-shaped element; (g) the PTC thermistor material being selected to have a Curie temperature which is at least 50°
K. higher than the cut-off temperature; and(h) means for providing a substantially even dissipation of heat from the first and second major surfaces of the heating element.
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Specification