US1789477A - Magnet core - Google Patents

Description

Patented Jam 20, 1931 UNITED STATES PATENT. OFFICE PHILIP NORTON BOSEBY, OF LIVERPOOL, ENGLAND, ASSIGNOB TO ASSOCIATED TELE- PHONE AND TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION 01 DELAWARE MAGNET CORE No Drawing. Applicationfiled April 27, 1029, Serial No. 858,760, and in Great Britain June 13,1928.

as employed in telephone circuits. The ob- 5 ject of the invention is the provision of a new and improved core material which is chea to manufacture and can readily be forme to the desired shape and which moreover possesses in a high degree the properties most advantageous for cores in loading coils, viz. high specific gravity and high ohmic resistance.

It has been usual hitherto to construct cores for loading-coils by subjecting a mixture of finely divided magnetic material with insulating material for magnetically separating the particles of magnetic material, to very high pressures so that the particles cohere and form a solid mass the specific gravity of which approximates tothat of pure-iron.

According to the present invention the insulating material comprises a film of iron phosphate and the particles are preferably held together by a binder of synthetic resin varnish, for instance a phenol-aldehyde condensation product. p

In order that the invention ma be better understood one methodof carrying it intoeffect will now be described. Use is preferably made of commercial iron powder which can be cheaply obtained, or use may be made of a powdered iron alloy such, as ferro-silicon or nickel iron. The powdered iron is first annealed in air-tight pots at a temperature of about 600 C. and is then boiled in a solution of zinc phosphate. As a result of this treatment an insulating film of metallic phosphate of iron is formed on the surface of the iron particles. This film has i great mechanical strength and very high electrical resistance and is therefore particularly suitable for loading-coil, dust cores, as its mechanical strength enables it to withstand moulding at pressures of 20 to 90 tons per square inch without losing its insulating properties and at the same time ensuring an initial permeablity approximating to that of pure iron.

The magneto powder after being boiled in the solution of zinc phosphate is washed in water and dried. In order to bind the magnetic particles together they are next coated with one coat of synthetic resin varnishof su table consistency,this varnish preferably being prepared from a powder composed of material known under the. registered trade name of Bakelite. The magnetic powder is then subjected to pressure of about 40 tons per s uare inch in moulds heated to about 200 to form rings The rings may now be made up into loading coils for use on telephone lines and for this purpose a suitable number, for instance, from four to eight, are bound together with tape and are wound with two windings on oposite halves of the core followed by a further two windings on top of those previously wound. In use one mner winding is connected with the opposite outer winding, and the two coils thus produced form the windings of the loading coil. The coil is then dried and embedded in resin.

It will be seen therefore that the arran ement according to the invention permits t e cheap construction of satisfactory loading coils having properties which make them comparatively small in bulk and highly efficient in use.

What I claim as new and desire to secure by Letters Patent is 1. A magnet core composed oi finely divided iron particles, a coating of iron phosphate on sald particles, and insulating material separating said phosphate coated particles.

2. A magnet core composed of finely divided particles of magnetic material, a coating of phosphate on said particles, and insulating material separating the phosphate coated particles.

3. The method ofmaking magnet cores, which consists in covering particles of magnetic material with a coating of phosphate of the magnetic material, then covering the coated particles with a binding material, and then forming a mass of the coated particles into a solid body by pressure sufiicient to give it a specific gravity approximating that of. the magnetic material.

4. The method of making magnet cores, which consists in covering particles of pure iron with a coating of iron phosphate, then proximating that of pure iron.

covering the coated iron particles with a. binding material, and then formin a mass of the coated particles into a solid b y by pressure suflicient to give it a specific gravity ap- 5. The method of making magnet cores, which consists in covering particles of pure iron with a coating of iron phosphate byboiling tlie ironcpartlcles in a solution of zinc phosphate, then. covering said coated particles with a binding material, and then forming a mass of said coated particles into, a solid body in a heated mold by pressure sufiicient to give it aspecific gravityapproximating' that of pure iron.

In testimony whereof I have signed my name at Liverpool, England, this th day of 1 April, 1929.

PHILIP NORTON ROSEBY.