High power induction work coil for small strip susceptors

Abstract

There is disclosed a high power induction heating coil for use in thermoplastic welding where a metallic susceptor is embedded in a composite assembly and is heated by eddy currents generated by the coil. The coil is comprised of several windings of Litz wire composed of multiple individually insulated strands of copper wire. The coil is wound on a circular E core having a coolant conduit through the center of the core. Coolant is introduced through the central core and returned by circulating through the loosely wound coil to the coolant source.

Description

BACKGROUND OF THE INVENTION

it is desirable to have as small a device as possible capable of producing sufficient heat for the welding process. An example of such a coil would be one having an effective work area of approximately one square inch. Such a coil made according to the invention would have a coil made up of 25 turns of five number 20 Litz wires wound on a Ferrotron 559 core. The core material is powdered iron in a plastic polymer and is identified by the trade name Ferrotron. This coil was designed to operate at a frequency of about 50 KHz and will provide a power level of up to 1,400 Watts.

Thus it can be seen that the invention described herein can produce an intense magnetic field over a small area and the self enclosed cup-core allows complete cooling of the winding and core. In addition, the device has a relatively high impedance making it possible to use leads of up to 10 feet without serious performance degradation.

Claims

1. A high power induction coil comprising:

a core of magnetic material having a central axis, first and second surfaces and a length therebetween, said core having an annular ring-shaped cavity extending from said second surface of said core to near the first surface of is said core and having a central leg approximately in a center of said annular ring-shaped cavity connected to the first surface of the core, said central leg being shorter than the length of said core whereby a sectional view through said core along the central axis forms an E-shaped core with a central leg and opposing side legs;

a sole plate attached to the second surface of the core forming a closure for the annular ring-shaped cavity in the core with a space between a lower end of the central leg and the sole plate;

a first fluid conduit extending through said central leg;

a second fluid conduit for providing a communication between an outside surface of said core with the annular ring-shaped cavity and with said first conduit through the space between the lower end of the central leg and the sole plate;

first and second fluid connectors attached to the first surface of the core, each of said fluid connectors being connected to its respective fluid conduit; and

an induction coil wound loosely around the central leg of said core, said coil having first and second ends extending through said first surface of said core, wherein said core allows for complete cooling of the coil and core, and wherein the high power induction coil produces an intense magnetic field over a small area.

2. The coil according to claim 1 wherein the inductive coil comprises multiple turns of a plurality of wires, each of said wires being composed of a plurality of individually insulated conductive strands.

3. The coil according to claim 2, wherein the lower end of the center leg of said core is truncated.

4. The coil according to claim 1, further comprising: a wedge shaped member of dielectric material having a thick and a thin edge attached to the sole plate of said core inside said annular ring-shaped cavity, the edge shaped member being placed with its thick end adjacent the outer edge of one side of sole plate and its thin edge terminates at the inside edge of the annular ring-shaped cavity at the opposite side of the core.

5. The coil according to claim 4 wherein the core is composed of ferrite material.

6. The coil according to claim 4 wherein the core is composed of powered iron in a plastic binder.

7. The high power induction coil according to claim 1, wherein said inductive coil is comprised of Litz wire.