Electric blanket having reduced electromagnetic field

• US 5,837,971 A
• Filed: 01/21/1997
• Issued: 11/17/1998
• Est. Priority Date: 01/21/1997
• Status: Expired due to Term

• Current Assignee: Myoung Jun Lee
• Original Assignee: Myoung Jun Lee
• Inventors: Lee, Myoung Jun
• Primary Examiner(s): Walberg, Teresa J.
• Assistant Examiner(s): NGUYEN, QUAN PHUOC
• Application Number:
  US08/785,981
• Time in Patent Office: 665 Days
• Field of Search: 219/528, 219/529, 219/212, 219/511
• US Class Current: 219/212
• CPC Class Codes: H05B 1/0272 For heating of fabrics
• CPC Class Codes: H05B 2203/004 using zigzag layout
• CPC Class Codes: H05B 2203/014 Heaters using resistive wires or cables not provided for in H05B3/54
• CPC Class Codes: H05B 2203/017 Manufacturing methods or apparatus for heaters
• CPC Class Codes: H05B 3/342 heaters used in textiles

Abstract

An electric blanket using an AC to DC converter circuit either alone or in combination with a shield mesh that surrounds the heating wire to substantially reduce the electromagnetic field produced by the heating wire. The electric blanket has a heating element having a conductive wire and a shielding component, in which the conductive wire is placed between the shielding component to substantially encase the conductive wire. To discharge any build up of electrical charges, the shielding component is coupled to the ground. The electric blanket also has a control device for use with the alternating electrical current. The control device has a temperature control circuit that controls the current flow pursuant to the temperature setting. A converter device used in the electric blanket is electrically connected to the outputs of the control device. The converter device includes a rectifier circuit connected to the control device and has output terminals to generate rectified current from the alternating electrical current; and a filter circuit connected across the output terminals of the rectifier circuit to provide direct electrical current to the wire of the heating element. The output of the filter circuit is provided to the conductive wire to generate heat with substantially reduced electromagnetic field.

Claims

1. An electric blanket adapted for use with alternating electrical current and a ground, the electric blanket comprising:

a heating element having a conductor disposed and enclosed between a first planar shield mesh and a second planar shield mesh, the first and second planar shield meshes substantially aligned to form a blanket layer, wherein the conductor is arranged to planarly meander between the first and second planar shield meshes which are coupled to the ground;

a control device for use with the alternating electrical current, having a temperature control circuit for outputting the alternating electrical current in relation to a predetermined temperature setting; and

a converter device electrically connected to the control device, wherein the converter device comprises

a rectifier circuit connected to the control device and having output terminals to generate rectified current from the alternating electrical current; and

a filter circuit connected across the output terminals of the rectifier circuit to provide direct electrical current to the conductor of the heating element.

2. An electric blanket of claim 1, wherein each one of the first and second planar shield meshes is in the form of a wire mesh made of conductive wire.

3. An electric blanket of claim 2, wherein the distance between each strand of the conductive wire in the wire mesh is about 5-10 mm.

4. An electric blanket of claim 2, wherein the conductive wire in the wire mesh is made of a plurality of twisted individual copper wires.

5. An electric blanket of claim 4, wherein the individual copper wire has a diameter of about 0.005 mm.

6. An electric blanket of claim 4, wherein the conductive wire in the wire mesh is made of five twisted individual copper wires.

7. An electric blanket of claim 1, wherein the filter circuit includes at least one capacitor connected to the output terminals of the rectifier circuit.

8. A resistive wiring for use in an electrical blanket adapted for use with a power source and a ground, the resistive wiring comprising:

a conductor which produces heat when connected to the power source; and

a first planar shield mesh and a second planar shield mesh, the first and second planar shield meshes being substantially aligned to form a blanket layer, wherein the conductor is arranged to planarly meander between the first and second planar shield meshes.

9. A resistive wiring of claim 8, wherein each one of the first and second planar shield meshes is in the form of a wire mesh made of conductive wire.

10. A resistive wiring of claim 9, wherein the distance between each strand of the conductive wire in the wire mesh is about 5-10 mm.

11. A resistive wiring of claim 9, wherein the conductive wire in the wire mesh is made of a plurality of twisted individual copper wires.

12. A resistive wiring of claim 11, wherein the individual copper wire has a diameter of about 0.005 mm.

13. A resistive wiring of claim 11, wherein the conductive wire in the wire mesh is made of at least three twisted individual copper wires.