US1810499A - Transformer winding wire - Google Patents

Description

Patented June 16, 1931 UNITED STATES PATENT OFFICE- .TOHAN ROMP, OF EINDHOVEN, NETHERLANDS, ASSTGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OE DELAWARE TRANSFORMER WINDING WIRE Ho Drawing. Application filed October 31, 1929, Serial No. 403,915, and in the Netherlands December 4, 1928.

The present invention relates to transformers, and, more particularly, to wire for windings of small transformers employed in wireless and similar purposes.

In order that such transformers may be given very small dimensions and yet include a large number of turns, the wire is usually drawn out to a very thin wire. For this purpose, a material must be used which has a sufficient tensile strength. Moreover, the material of the said wire must not have too high a specific resistance, and, besides, it must be resistant to corrosion so that if in the wound wire the insulation, which naturally is extremely thin, shows slight faults, corrosion of the wire will be out of the question.

In general, copper does not fulfill the condition of having sufficient tensile strength, and nearly all the alloys of this metal do not satisfy at the same time the requirements of conductivity and resistance against corrosion. Silver offers, it is true, a suflicient resistance against corrosion, but it also has too small a tensile strength.

There are known, however, alloys of silver and copper which possess the three above mentioned properties. In order to ensure a sufficient resistance against corrosion, the alloy must contain at least ninety-four per cent of silver, for at this percentage free copper crystals no longer occur in it. This is disclosed, for example, in United States Patent 1,718,080 issued June 18, 1929.

However, the use of a winding wire having such a high content of silver is rather expensive. Thus, this invention has for its object the provision of a wire which has a slight total content of silver, and, which notwithstanding, possesses the aforementioned re uired properties.

ccording to my invention, the wire constituting at least one of the windings of the transformer, consists of a core of a metal or alloy which has a great tensile strength, said core being surrounded by a sheath consisting of a metal or alloy which is highly resistant to corrosion. In this case, the core of the wire need not be highly resistant against corroslon.

For constituting the winding or windings, use may be made, for example, of a wire whose core consists of an alloy containing about ninety per cent of copper and about ten per cent of silver, said core bein surrounded by a sheath of pure silver. Tt has been found that when for winding such transformers, use is made of enamelled copper wire, the tensile strength of this metal is considerably reduced by the enamelling operation. The use of a windin wire according to the present invention a ords the advantage that the tensile strength of the enamelled wire still meets the requirements. 7

While I have indicated and described one arrangement for carrying my invention into elfect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organization shown and described, but that many modifications may be employed, without departing from the scope of my invention as set forth in the appended claims.

Whatl claim is:

1. A high frequency transformer in which the wire of at least one of the windings consists of a metallic core of great tensile strength and low corrosion resistance surrounded by a metallic sheath which is highly resistant to corrosion.

2. A transformer, according to claim 1, in which the sheath of the wire consists of an alloy of silver and copper free of copper crysta s.

3. A transformer, according to claim 1, in which the core of the wire consists of an alloy of copper and silver which contains a small percentage of silver.

4. A high'frequency transformer in which the core of the wire of at least one of the windings consists of a copper-silver alloy which contains a small percentage of silver, said core being surrounded by a sheath of silver, said Wire being insulated by a layer of enamel.

5. A high frequency transformer having a Winding of wire comprising a metallic core consisting of about ninety per cent of copper and ten per cent of silver, and a silver sheath surrounding said core.

6. A radio frequency transformer having a Winding of Wire, comprising a core including a large amount of copper and a relatively small amount of silver, and a layer of silver surrounding the core.

JOHAN ROMP.