MAGNETIC HEATING BLANKET

• US 20110139769A1
• Filed: 12/15/2009
• Published: 06/16/2011
• Est. Priority Date: 12/15/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Taylor, David F., Matsen, Marc R., Miller, Robert J.
• Granted Patent: US 8,330,086 B2
• Time in Patent Office: Days
• US Class Current: 219/634
• CPC Class Codes: B29C 2035/0811 using induction
• CPC Class Codes: B29C 73/10 using patches sealing on the surface of the article B29C73/14 takes precedence
• CPC Class Codes: B29C 73/30 for local pressing or local heating
• CPC Class Codes: H05B 2206/023 using the curie point of the material in which heating current is being generated to control the heating temperature
• CPC Class Codes: H05B 6/106 in the form of fillings

Abstract

A heating blanket comprises a conductor for receiving current and generating a magnetic field in response to the current. The heating blanket may include a susceptor sleeve formed of magnetic material having a Curie temperature. The susceptor sleeve may extend along the conductor and may be inductively heated in response to the magnetic field.

Claims

1. A heating blanket, comprising:

a conductor for receiving current and generating a magnetic field in response thereto; and

a susceptor sleeve formed of magnetic material having a Curie temperature, the susceptor sleeve extending along the conductor for induction heating thereof in response to the magnetic field.

2. The heating blanket of claim 1 further comprising:

a matrix in thermal contact with the susceptor sleeve.

3. The heating blanket of claim 1 wherein:

the current is alternating current.

4. The heating blanket of claim 3 wherein:

the frequency of the alternating current is in the range of from approximately 1 kHz to approximately 300 kHz.

5. The heating blanket of claim 4 wherein:

the frequency of the alternating current is less than 20 kHz.

6. The heating blanket of claim 3 wherein:

the frequency of the alternating current is adjustable for altering the heating rate.

7. A heating blanket for heating a rework area of a composite structure, comprising:

a power supply for generating alternating current having a frequency of between approximately 1 kHz and 300 kHz and an amperage of between approximately 10 amps and 1000 amps at a voltage of between approximately 10 volts and 300 volts;

a housing formed of flexible material and containing a thermally conductive matrix;

an insulating layer disposed on one of opposing sides of the housing;

a conductor housed within the housing and extending in a meandering pattern through the matrix, the conductor receiving alternating current from the power supply for generating an alternating magnetic field in response to the alternating current; and

a susceptor sleeve formed of magnetic material having a Curie temperature and being coaxially mounted to the conductor and electrically insulated therefrom for induction heating in response to the magnetic field.

8. A heating blanket for heating a structure to a desired temperature, comprising:

a conductor for receiving alternating current and generating a magnetic field in response thereto; and

a matrix disposed in proximity to the conductor and containing at least one of the following;

ferromagnetic particles for hysteretic heating thereof in response to the magnetic field, the ferromagnetic particles being selected such that the Curie temperature is substantially greater than the desired temperature;

superparamagnetic particles for relaxation heating thereof in response to the magnetic field, the superparamagnetic particles having a Curie temperature corresponding to a size of the superparamagnetic particles.

9. The heating blanket of claim 8 wherein:

the frequency of the alternating current is in the range of from approximately 1 kHz to approximately 300 kHz.

10. The heating blanket of claim 8 wherein:

the alternating current is substantially constant.

11. The heating blanket of claim 8 wherein:

the Curie temperature comprises a temperature range of the superparamagnetic particles.

12. The heating blanket of claim 11 wherein:

the temperature range corresponds to at least one of a frequency and an amplitude of the alternating.

13. A method of heating a structure, comprising the steps of:

heating inductively a susceptor sleeve in response to a magnetic field;

heating conductively a structure in thermal contact with the susceptor sleeve; and

reducing the inductive heating of the susceptor sleeve when the susceptor sleeve becomes non-magnetic upon reaching a Curie temperature of the susceptor sleeve.

14. The method of claim 13 further comprising the step of:

applying alternating current to a conductor having the susceptor sleeve mounted thereto, the susceptor sleeve being formed of magnetic material having the Curie temperature.

15. The method of claim 14 further comprising the step of:

generating the magnetic field along the length of the susceptor sleeve in response to the alternating current.

16. The method of claim 13 further comprising the step of:

reducing the conductive heating of the structure.

17. The method of claim 13 wherein the step of reducing the inductive heating of the susceptor sleeve comprises:

reducing a voltage across the conductor to a level for maintaining the susceptor sleeve at the Curie temperature.

18. The heating blanket of claim 13 wherein the step of reducing the inductive heating of the susceptor sleeve comprises the steps of:

reducing the inductive heating of portions of the susceptor sleeve at the Curie temperature; and

continuing the inductive heating of the portions of the susceptor sleeve that are below the Curie temperature.

19. The method of claim 18 wherein the step of reducing the inductive heating of the susceptor sleeve comprises:

reducing a voltage across the conductor while maintaining the alternating current;

monitoring the reduction of the conductor voltage; and

indicating attainment of the desired temperature when the conductor voltage stabilizes.

20. A method of heating a structure, comprising the steps of:

applying alternating current to a conductor having ferromagnetic particles embedded in a matrix located adjacent to the conductor, the ferromagnetic particles having a Curie temperature and a hysteretic temperature that is less than the Curie temperature;

generating a magnetic field in the ferromagnetic particles in response to the alternating current;

heating the ferromagnetic particles;

heating conductively the structure; and

reducing the heating of the ferromagnetic particles when the ferromagnetic particles reach the hysteretic temperature.

21. The method of claim 20 further comprising the steps of:

selecting a desired temperature of the structure; and

selecting the ferromagnetic particles such that the Curie temperature is substantially greater than the desired temperature.

22. The method of claim 20 further comprising the steps of:

maintaining a substantially uniform temperature across the structure by performing at least one of the following;

reducing the conductive heating of portions of the structure located adjacent to ferromagnetic particles reaching the hysteretic temperature; and

continuing the conductive heating of portions of structure located adjacent to ferromagnetic particles below the hysteretic temperature.

23. A method of heating a structure, comprising the steps of:

applying alternating current to a conductor having superparamagnetic particles embedded in a matrix located adjacent to the conductor, the superparamagnetic particles having a Curie temperature corresponding to a size of the superparamagnetic particles;

generating a magnetic field in response to the alternating current;

heating the superparamagnetic particles by relaxation heating in response to the magnetic field;

heating the structure conductively; and

reducing the relaxation heating of the superparamagnetic particles when the superparamagnetic particles attain the Curie temperature.

24. The method of claim 23 further comprising the step of:

adjusting the Curie temperature by altering a frequency of the alternating current.

25. The method of claim 23 further comprising the step of:

selecting a plurality of particle sizes of the superparamagnetic particles for generating heat within a corresponding plurality of Curie temperatures.