Formable composite magnetic flux concentrator and method of making the concentrator

• US 5,828,940 A
• Filed: 01/26/1996
• Issued: 10/27/1998
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: Lear Flux, Inc.
• Original Assignee: Lear Flux, Inc.
• Inventors: Learman, Thomas J.
• Primary Examiner(s): Jenkins, Daniel J.
• Application Number:
  US08/592,097
• Time in Patent Office: 1,005 Days
• Field of Search: 419/38, 419/10, 419/23
• US Class Current: 419/10
• CPC Class Codes: H01F 1/26 by macromolecular organic substances
• CPC Class Codes: H05B 6/02 Induction heating
• CPC Class Codes: H05B 6/365 using supplementary conductive or ferromagnetic pieces

Abstract

A formable composite magnetic flux concentrator material is composed of about 65% to 90% ferromagnetic material, such as iron powder, and about 35% to 10% binder, the binder being a mixture of an epoxy and one or more catalysts. The concentrator material is provided in a formable state as a putty-like body which can be worked into any desired shape dictated by the configuration of the induction heating coil used in a particular application. In one form, the density of the concentrator material is increased by application of vibration, compression and vacuum to de-air the material and to reduce voids therein. In another form, the iron powder comprises spherical-shaped particles and non-spherical shaped powders chosen in a ratio to maximize the density of material available.

Claims

1. A method of making a formable composite magnetic flux concentrator, comprising the steps of:

(a) preparing a body in a formable putty-like state by mixing together a ferromagnetic material and a binder, said ferromagnetic material being in a percent by weight in the range of about 65% to 90% and said binder being in a percent by weight range of about 35% to 10%;

(b) shaping said body while in said formable putty-like state into a selected shape; and

(c) solidifying said formable body by applying heat to said body to cause said binder to change said formable body having the selected shape to a solid body.

2. The method of claim 1 wherein said binder is a mixture of an epoxy and at least two catalysts.

3. The method of claim 2 wherein said shaping includes applying a coating material to the body to form a dry shell thereof about the exterior of the body so that the body will hold said selected shape.

4. The method of claim 1 wherein said shaping includes adding a dry colored powder to the coating material to indicate a formulation assigned to the concentrator.

5. The method of claim 1 wherein said preparing includes adding a fumed silica to the ferromagnetic material and binder.

6. The method of claim 5 wherein the fumed silica is within the range of from about 0.01% to 6% by weight of the total composition of the concentrator body.

7. The method of claim 1 wherein said shaping includes embedding hollow elements in the body while the body is in said formable putty-like state to provide a means by which the concentrator can be cooled during use.

8. The method of claim 1 wherein said shaping includes graining the body while the body is in said formable putty-like state by applying a magnetic field to the body in the direction of the proposed end use of the concentrator.

9. The method of claim 1 wherein said ferromagnetic material is an iron powder having particles of a first shape and a second shape different than said first shape.

10. The method of claim 1 wherein said binder will harden without the presence of a catalyst when heated to between about 380°

F. to 400°

F.

11. A method comprising steps of:

providing a formable magnetic flux concentrator material;

forming the concentrator material at low pressure so that there is no loss of desirable magnetic properties; and

baking the formable concentrator material to harden the concentrator material into a permanent shape.

12. A method as defined in claim 11 wherein said step of forming includes forming the material at less than 10 tons per square inch.

13. A method as defined in claim 12 wherein said step of forming includes forming the material by hand.

14. A method as defined in claim 11 including a step of machining the concentrator material after the step of baking.

15. A method as defined in claim 14 wherein the concentrator material includes about 85% to 96% ferromagnetic material.

16. A method as defined in claim 11 wherein the step of forming includes compressively vibrating the concentrator material.

17. A method comprising steps of:

mixing a formable magnetic flux concentrator material including at least about 85% machineable iron powder;

forming the concentrator material at less than 10 tons per square inch;

machining the formed concentrator material after the step of forming; and

hardening the formed composite material.

18. A method as defined in claim 17 wherein the step of forming includes compressively vibrating the concentrator material.

19. A method as defined in claim 17 wherein the step of mixing includes at least about 96% machineable iron powder.

20. A method for forming a magnetic flux concentrator comprising steps of:

selecting particles of predetermined size comprising an alloy having a selected permeability;

mixing a formable magnetic composite material including the alloy particles;

forming the formable magnetic composite material at a pressure below about 10 tons per square inch and which is low enough to prevent undesired loss of magnetic properties below the selected permeability; and

hardening the formed material.

21. A method as defined in claim 20 wherein the step of mixing includes mixing another magnetically conductive material with the alloy particles, the another magnetically conductive material having a different composition than the alloy particles.