Inductor devices – Core forms casing
Reexamination Certificate
1998-11-30
2001-05-29
Mai, Anh (Department: 2832)
Inductor devices
Core forms casing
C336S233000, C336S060000, C029S602100
Reexamination Certificate
active
06239681
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to induction coils, and is more particularly concerned with a wire core for induction coils such as transformers, chokes and the like.
2. Discussion of the Prior Art
It is common for transformers and other induction devices to be made up of a core comprising a plurality of sheets of steel, the sheets being die cut and stacked to create the desired thickness of a core. The individual sheets are varnished or otherwise electrically insulated from one another in order to reduce eddy currents in the core, and the thickness of the individual sheets is selected to minimize eddy currents.
The core of a transformer or the like generally passes through the center of the electric winding, and closes on itself to provide a closed magnetic circuit. Since the core then supports the electric winding, it is natural that the core has been used as the support for the transformer. That is to say, one attaches the core to a container or baseboard in order to support the transformer.
Transformers and other induction coils inherently generate heat, and the heat must be dissipated or the power characteristics of the device will change. If the device becomes too hot, the electric winding can become short circuited and burn out the coil. In small devices, one usually relies on air cooling, sometimes with metal fins or the like to assist in dissipating the heat. In larger devices, the coils and core may be immersed in oil. One then may use fins on the container, radiator pipes, or both, so convection currents move the heated oil through the cooling fins or pipes. If further cooling is needed, one generally resorts to fans to move more air across the cooling means.
When a stack of metal sheets is used as the core for an induction coil, it is usual to provide a shape, such as an E with the electric winding on the center leg of the E. After the coil is in place, in additional stack of sheets is applied to connect the ends of the E, thereby completing the magnetic circuit. Using such a technique, it will be understood that the coil is necessarily wound separately, and subsequently placed on the core. The coil must therefore be big enough to slip onto the core. Such construction contributes to the inherent noisiness of an induction coil, because the electric winding must be somewhat loose on the core. As a result, when an alternating voltage is applied to the electric winding, the sheets making up the core tend to vibrate with the alternating magnetic field. Any gaps and spaces between the electrical components and the magnetic components reduce coupling and efficiency of action.
SUMMARY OF THE INVENTION
The present invention provides a core for induction coils, the core comprising a plurality of wires bundled to make up the needed core. The electric winding is either wound directly onto the bundle of wires, or is wound separately and slipped over the core. After the electric winding is in place, the ends of the wires making up the core are spread and formed over the winding, the two ends of the wires meeting to form a complete magnetic circuit. A band or other connector means can hold the ends together.
In one embodiment of the invention, the core may include a screw bound into the core and extending therefrom as a mounting means for the induction coil. The screw may extend from either one side or both sides as desired. Also, the make-up of the core may be otherwise varied considerably. Wires of various diameters may be used to achieve greater density of the core; a few large wires may be spaced around the core to provide rigidity; and, one or more tubes may be incorporated into the core, the tubes carrying a heat exchange fluid for cooling the induction coil. The cooling tubes are preferably of non-magnetic and non-electrical-conducting material.
REFERENCES:
patent: 414266 (1889-11-01), Thomson
patent: 499852 (1893-06-01), Pfannkuche
patent: 619760 (1899-02-01), Kinrade
patent: 1597901 (1926-08-01), Kent
patent: 2043346 (1936-06-01), Buckley
patent: 2179661 (1939-11-01), Jones
patent: 3304599 (1967-02-01), Nordin
patent: 3350670 (1967-10-01), Strauch
patent: 3720897 (1973-03-01), Feather et al.
patent: 4035751 (1977-07-01), Waltnew
patent: 352251 (1922-04-01), None
King & Schickli PLLC
Mai Anh
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