Dummy pin structure for a miniature transformer

Details Dummy pin structure for a miniature transformer Dummy pin structure for a miniature transformer

1999-02-16

2001-03-27

Gellner, Michael L. (Department: 2832)

Inductor devices

Winding with terminals, taps, or coil conductor end...

C336S107000, C336S198000

Reexamination Certificate

active

06208232

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to dummy pins for a miniature transformer, and more particularly to dummy pins for a miniature transformer that are integral extensions of principal pins projected from two ends of a bobbin of the transformer. The dummy pins at each end of the bobbin are located between and shorter than the principal pins and are provided at an inner side with a curved notch for leads on the transformer to wind around the dummy pins at the curved notches instead of the principal pins, so as to avoid broken leads that results in high bad yield in the production of the miniature transformer.
A transformer is an important and necessary component in an electronic circuit. With the development of dimensionally minimized circuit board, the transformer for mounting on the circuit board must be as small as possible in volume without sacrificing its intended functions. A conventional miniature transformer includes a bobbin, windings (including first and second windings), a core, and pins projected from two end surfaces of the bobbin. The transformer has dimensions as small as 18 mm (L)×8.5 mm (W)×4.4 mm (H). A small space generally equal to the volume of the transformer must be prepared on the circuit board for mounting the transformer. For such a small transformer to achieve the intended high performance within a given or extremely limited volume, it is basically necessary to reduce the diameter and increase the turns of the copper wire for forming the windings. Such miniature transformer is particularly needed in the designs of, for example, modems for notebook computers and/or card-type portable modems that have a transmission speed as high as 33.6 K or 56 K BPS. However, following confusions are often found with currently commercially available miniature transformers:
1. The first and second windings of the miniature transformer have their own leads that are guided to wind around the pins at two end surfaces of the bobbin. Such leads are so tiny that they tend to break when the pins are subject to an external force in the process of manufacturing the transformer. A high bad yield up to 2% in the production of the miniature transformer is therefore frequently caused. In other words, quality control in the mass production of conventional miniature transformer is uneasy and the manufacturing cost thereof is increased, accordingly.
2. The fine leads having been wound around the pins are subject to another possible breaking caused by external force against it and/or touch of it in the process of mounting the completed miniature transformer on the circuit board. This would cause a reduced reliability of the finished product and would have big influence on a good image of the product.
It is therefore necessary to develop dummy pins for a miniature transformer to facilitate the mass production and enhance the durable use thereof.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a dummy pin structure for a miniature transformer. The dummy pin according to the present invention is formed by integrally extending a rear end of a principal pin obliquely forward toward a central area of the end surface of the bobbin and then turning straight forward to project from the end surface of the bobbin. The rear ends of the principal pins and the oblique parts of the dummy pins are actually an integral piece and are firmly embedded in the bobbin when the bobbin is injection molded. The dummy pins at each end surface of the bobbin are located between and shorter than two principal pins and are therefore protected by them from external force. By guiding and winding leads of the transformer around the dummy pins instead of the principal pins, the leads are not subject to easy breaking due to external force during manufacturing and using of the miniature transformer.
Another object of the present invention is to provide a dummy pin structure for a miniature transformer. The transformer has principal pins and each of the principal pins has an extended rear portion embedded in the bobbin of the transformer. The extended rear portion of the principal pin obliquely extends forward toward a central area of the end surface of the bobbin at an optimal angle to form a shorter and integral dummy pin that projects from the end surface of the bobbin to locate between two principal pins. Such arrangement requires minimum space and facilitates firm and stable location of the dummy pins in the bobbin when the same is injection molded.
A further object of the present invention is to provide a dummy pin structure for a miniature transformer. Wherein the dummy pin each is provided at an inner side with a curved notch for a lead of the transformer to wind around there without undesirably contacting with the lead wound around an adjacent dummy pin, so that the quality and reliability of the transformer can be well controlled.


REFERENCES:
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patent: 5751203 (1998-05-01), Tsutsumi et al.
patent: 5859577 (1999-01-01), Nihei et al.
patent: 5903202 (1999-05-01), Endoh et al.

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