Thermo-sensitive heater and heater driving circuit

• US 6,756,572 B2
• Filed: 12/28/2001
• Issued: 06/29/2004
• Est. Priority Date: 06/09/2001
• Status: Expired due to Fees

• Current Assignee: Myoung Jun Lee
• Original Assignee: Myoung Jun Lee
• Inventors: Lee, Myoung Jun
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US10/034,177
• Publication Number:
  US 20020195442A1
• Time in Patent Office: 914 Days
• Field of Search: 219/212, 219/200, 219/209, 219/213, 219/482, 219/490, 219/491, 219/494, 219/497, 219/505, 219/548, 219/552, 219/553, 219/544, 219/549
• US Class Current: 219/505
• CPC Class Codes: H05B 1/0272 For heating of fabrics
• CPC Class Codes: H05B 2203/01 Heaters comprising a particular structure with multiple layers
• CPC Class Codes: H05B 3/56 Heating cables

Abstract

A thermo-sensitive heater and heater driving circuit are disclosed. The thermo-sensitive heater comprises a cord-shaped nylon thermistor that surrounds a heating element, such that the thermistor detects the temperature of the heating element and controls the driving current for a heating coil. Also, the present invention includes electromagnetic shielding material, which is formed by winding an electric conductor around the outer surface of the nylon thermistor, or formed as a wire mesh. This shielding material is advantageous for discharging the electric field radiated from inside of the heater to an external electric field, thus safely eliminating harmful electric fields. Also, the present invention further provides a driving circuit for safely driving the heater, which includes a temperature controller or an overheating prevention circuit.

Claims

1. A thermo-sensitive heater comprising:

a tubular coating layer with electric insulating characteristics;

a tubular thermistor disposed in the coating layer, having inner and outer surfaces;

a cord-shaped heating element disposed in the thermistor, having inner and outer surfaces;

a center core structure disposed in the form of a wire in the cord-shaped heating element;

a shielding coil disposed in the form of a winding wire around the outer surface of the thermistor, wherein the shielding coil comprises a temperature detecting terminal;

a first heating coil disposed in the form of a winding wire around the outer surface of the cord-shaped heating element, thus contacting the inner surface of the thermistor; and

a second heating coil disposed in the form of a winding wire around the center core structure, contacting the inner surface of the cord-shaped heating element, wherein the first and second heating coils are connected in series and are each connected to a current supplying terminal.

2. The thermo-sensitive heater as set forth in claim 1, wherein the thermistor is formed on an outer surface of the cord-shaped heating element through an extrusion forming process.

3. The thermo-sensitive heater as set forth in claim 1, wherein the tubular coating layer comprises polyvinyl chloride.

4. The thermo-sensitive heater as set forth in claim 1, wherein the thermistor comprises a nylon resin.

5. The thermo-sensitive heater as set forth in claim 1, wherein the shielding coil comprises rolled copper wire that is formed by compressing a copper wire, and radiates electromagnetic waves radiated from the cord-shaped heating element to a neutral terminal of an AC voltage during a heating cycle.

6. The thermo-sensitive heater as set forth in claim 1, wherein the outer surface of the cord-shaped heating element comprises silicon rubber.

7. The thermo-sensitive heater as set forth in claim 1, wherein the center core structure comprises polyester filament yarn.

8. The thermo-sensitive heater as set forth in claim 1, wherein the first and second heating coils comprise rolled copper wire that is formed by compressing the copper wire.

9. The thermo-sensitive heater as set forth in claim 1, further comprising:

a diode disposed between a first terminal and the cord-shaped heating element such that an operation cycle of an AC voltage supplied to the first terminal and a neutral terminal is divided into a heating cycle with a positive AC voltage applied to the cord-shaped heating element through the first terminal, and a (2) temperature detecting cycle with the positive AC voltage applied to the current supplying terminal through the neutral terminal;

a heating resistor arranged parallel to the diode for inducing a temperature voltage left in the tubular thermistor to the temperature detecting terminal during a temperature detecting cycle; and

a temperature controller for detecting a voltage, which is outputted between opposite sides of the heating resistor, through the temperature detecting terminal during the temperature detecting cycle, and for switching on/off a driving current for the cord-shaped heating element.

10. The thermo-sensitive heater as set forth in claim 9, wherein the temperature controller comprises:

a silicon controlled rectifier arranged between the first heating coil and the neutral terminal so as to switch on/off the driving current for the first and second heating coils which is applied through the first terminal;

a temperature fuse connected to the heating resistor and arranged on a side of a terminal for supplying the driving current for the cord-shaped heating element such that the temperature fuse is cut if a temperature of the heating resistor rises;

a temperature detector for detecting a temperature voltage applied between the heating resistor and the second heating coil during the temperature detecting cycle and for maintaining the detected temperature voltage until a next temperature detecting cycle;

a temperature setting unit for setting a heating temperature of the thermo-sensitive heater by a variable resistor and simultaneously operating in conjunction with a switch for switching on/off the driving current for the cord-shaped heating element;

a temperature comparator for comparing a temperature detected by the temperature detector and a temperature preset by the temperature setting unit, and for outputting a “

high”

signal if the detected temperature voltage is correspondingly lower than the preset temperature and a “

low”

signal if the detected temperature voltage is correspondingly higher than the preset temperature;

a zero detector for generating a “

high”

signal for a predetermined period of time when a voltage at the neutral terminal is 0 V during the operation cycle of the AC voltage, and for generating a “

low”

signal during a remaining period of time during the operation cycle of the AC voltage;

a disconnection detector connected to a side of the shielding coil opposite the neutral terminal for generating a “

high”

signal if the shielding coil is not disconnected, and for generating a “

low”

signal if the shielding coil is disconnected;

an AND gate for logically combining the output signals from the zero detector, the temperature comparator and the disconnection detector, and for outputting the combined signal; and

a driving unit for receiving and amplifying the output of the combined signals from the AND gate and providing the amplified output of the combined signals to the SCR as a gate current.

11. A thermo-sensitive heater comprising:

a tubular coating layer with electric insulating characteristics;

a tubular electrical insulation layer disposed in the coating layer, having inner and outer surfaces;

a tubular first layer disposed in the electrical insulation layer, having inner and outer surfaces;

a cord-shaped heating element disposed in the first layer, having inner and outer surfaces;

a core wire disposed in the cord-shaped heating element;

a first electrode disposed around the outer surface of the cord-shaped heating element and connected to a driving current connection terminal, thus contacting the inner surface of the first layer, for applying a temperature measuring current to the first layer, and for use as a heating element of the cord-shaped heating element;

a second electrode disposed around the first layer, thus contacting the inner surface of the electrical insulation layer, for detecting an electric resistance value of the first layer, which is varied according to the temperature variation of the cord-shaped heating element; and

a first heating coil disposed around the core wire and connected to a driving current connection terminal, wherein the first heating coil and the first electrode are connected in series.

12. The thermo-sensitive heater as set forth in claim 11, wherein a first shielding coil is disposed in the form of a winding wire around the outer surface of the electrical insulation layer for discharging an electric field radiated from the cord-shaped heating element to an external electric field and comprises rolled copper wire that is formed by compressing a copper wire.

13. The thermo-sensitive heater as set forth in claim 11, wherein the first electrode is a winding wire arranged to coil around the outer surface of the cord-shaped heating element and comprises rolled copper wire that is formed by compressing a copper wire.

14. The thermo-sensitive heater as set forth in claim 11, wherein the second electrode is a winding wire arranged to coil around the nylon layer and comprises rolled copper wire that is formed by compressing a copper wire.

15. The thermo-sensitive heater as set forth in claim 11, wherein the first heating coil is a winding wire arranged to coil around the electric insulation core wire and comprises rolled copper wire that is formed by compressing a copper wire.

16. The thermo-sensitive heater as set forth in claim 11, wherein the core wire comprises glass fiber wire.

17. The thermo-sensitive heater as set forth in claim 11, wherein the electrical insulation layer comprises silicon rubber.

18. The thermo-sensitive heater as set forth in claim 11, wherein the first layer comprises a nylon resin.

19. The thermo-sensitive heater as set forth in claim 11, wherein the outer surface of the cord-shaped heating element comprises rubber.

20. The thermo-sensitive heater as set forth in claim 11, wherein the tubular coating layer comprises polyvinyl chloride.

21. The thermo-sensitive heater as set forth in claim 11, wherein the first electrode is disposed in the form of a wire mesh surrounding the outer surface of the cord-shaped heating element.

22. The thermo-sensitive heater as set forth in claim 11, wherein the second electrode is disposed in the form of a wire mesh surrounding the first layer.

23. The thermo-sensitive heater as set forth in claim 11, wherein the first heating coil is disposed as a plurality of wires winding wire surrounding the core wire.

24. The thermo-sensitive heater as set forth in claim 11, wherein the cord-shaped heating element is a non-magnetic heating element;

the first electrode is used as a second heating coil; and

the second electrode is used as a second shielding coil.