Induction heating system with a flexible coil

• US 6,346,690 B1
• Filed: 09/20/2000
• Issued: 02/12/2002
• Est. Priority Date: 05/05/1998
• Status: Active Grant

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Baxter, Randall, Bickel, David M., Wiseman, Don, Ulrich, Mark
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US09/665,844
• Time in Patent Office: 510 Days
• Field of Search: 219/635, 219/643, 219/644, 219/647, 219/656, 219/663, 219/672, 219/674, 219/629, 219/645, 219/664, 219/601-603, 219/607, 219/617, 219/637, 219/640, 219/660-662, 219/665, 219/666, 219/668, 296/05
• US Class Current: 219/635
• CPC Class Codes: C21D 1/10 by electric induction
• CPC Class Codes: C21D 1/42 Induction heating
• CPC Class Codes: C21D 2221/00 Treating localised areas of an article
• CPC Class Codes: H05B 6/40 Establishing desired heat distribution, e.g. to heat particular parts of workpieces
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A method and apparatus for induction heating includes a power supply, and a controller, and an induction head. The induction head includes a flexible coiled, such as one formed with Litz wire. The head also includes a thermal insulator, for disposing between the head and the workpiece. The insulator reflects heat back to the workpiece, protecting the coil, but is transparent to inductive (E-M) energy. The power supply is a variable output frequency power supply, such as one having a resonant tank, to adapt to the inductance of the head.

Claims

1. A method of relieving heat stress from a weld between two cylindrical workpieces, comprising:

placing an induction coil comprised of Litz wire on either side of the weld;

flexing the coil about the workpieces; and

heating the cylindrical workpieces along the weld, thereby relieving stress.

2. The method of claim 1, further comprising inducing heat at a frequency in at least the kilohertz range.

3. The method of claim 1, further including placing the coil in a blanket comprised of a silica fiber.

6. The method of claim 1, further including placing the coil in a blanket comprised of a silica fiber.

4. A method of relieving heat stress from a weld between two cylindrical workpieces comprising:

placing an induction coil on either side of the weld;

flexing the coil about the workpieces; and

inducing heat in the workpiece at a frequency of at least in the kilohertz range, thereby relieving stress.

5. The method of claim 4, further comprising placing the coil comprised of Litz wire about the workpieces.

7. A method of relieving heat stress from a weld between two cylindrical workpieces, comprising:

placing an induction coil comprised of Litz wire in a blanket comprised of silica fiber;

placing the blanket on either side of the weld; and

heating the cylindrical workpieces along the weld;

thereby relieving stress.

8. A method of relieving heat stress from a weld between two cylindrical workpieces comprising:

placing an induction coil in a blanket comprised of silica fiber;

placing the blanket on either side of the weld; and

inducing heat in the workpieces at a frequency of at least in the kilohertz range, thereby relieving stress.